35.E: The Nervous System (Exercises) - Biology

35.1: Neurons and Glial Cells

Nervous systems throughout the animal kingdom vary in structure and complexity, as illustrated by the variety of animals shown in Figure 35.1.1. Others, like jellyfish, lack a true brain and instead have a system of separate but connected nerve cells (neurons) called a “nerve net.” Echinoderms such as sea stars have nerve cells that are bundled into fibers called nerves.

Review Questions

Neurons contain ________, which can receive signals from other neurons.

  1. axons
  2. mitochondria
  3. dendrites
  4. Golgi bodies


A(n) ________ neuron has one axon and one dendrite extending directly from the cell body.

  1. unipolar
  2. bipolar
  3. multipolar
  4. pseudounipolar


Glia that provide myelin for neurons in the brain are called ________.

  1. Schwann cells
  2. oligodendrocytes
  3. microglia
  4. astrocytes


Free Response

How are neurons similar to other cells? How are they unique?

Neurons contain organelles common to all cells, such as a nucleus and mitochondria. They are unique because they contain dendrites, which can receive signals from other neurons, and axons that can send these signals to other cells.

Multiple sclerosis causes demyelination of axons in the brain and spinal cord. Why is this problematic?

Myelin provides insulation for signals traveling along axons. Without myelin, signal transmission can slow down and degrade over time. This would slow down neuronal communication across the nervous system and affect all downstream functions.

35.2: How Neurons Communicate

All functions performed by the nervous system—from a simple motor reflex to more advanced functions like making a memory or a decision—require neurons to communicate with one another. While humans use words and body language to communicate, neurons use electrical and chemical signals. Just like a person in a committee, one neuron usually receives and synthesizes messages from multiple other neurons before “making the decision” to send the message on to other neurons.

Review Questions

For a neuron to fire an action potential, its membrane must reach ________.

  1. hyperpolarization
  2. the threshold of excitation
  3. the refractory period
  4. inhibitory postsynaptic potential


After an action potential, the opening of additional voltage-gated ________ channels and the inactivation of sodium channels, cause the membrane to return to its resting membrane potential.

  1. sodium
  2. potassium
  3. calcium
  4. chloride


What is the term for protein channels that connect two neurons at an electrical synapse?

  1. synaptic vesicles
  2. voltage-gated ion channels
  3. gap junction protein
  4. sodium-potassium exchange pumps


Free Response

How does myelin aid propagation of an action potential along an axon? How do the nodes of Ranvier help this process?

Myelin prevents the leak of current from the axon. Nodes of Ranvier allow the action potential to be regenerated at specific points along the axon. They also save energy for the cell since voltage-gated ion channels and sodium-potassium transporters are not needed along myelinated portions of the axon.

What are the main steps in chemical neurotransmission?

An action potential travels along an axon until it depolarizes the membrane at an axon terminal. Depolarization of the membrane causes voltage-gated Ca2+ channels to open and Ca2+ to enter the cell. The intracellular calcium influx causes synaptic vesicles containing neurotransmitter to fuse with the presynaptic membrane. The neurotransmitter diffuses across the synaptic cleft and binds to receptors on the postsynaptic membrane. Depending on the specific neurotransmitter and postsynaptic receptor, this action can cause positive (excitatory postsynaptic potential) or negative (inhibitory postsynaptic potential) ions to enter the cell.

35.3: The Central Nervous System

The central nervous system is made up of the brain and spinal cord and is covered with three layers of protective coverings called meninges (from the Greek word for membrane). The outermost layer is the dura mater with the primary function for this thick layer is to protect the brain and spinal cord. The dura mater also contains vein-like structures that carry blood from the brain back to the heart. The middle layer is the web-like arachnoid mater. The last layer is the pia mater.

Review Questions

The ________ lobe contains the visual cortex.

  1. frontal
  2. parietal
  3. temporal
  4. occipital


The ________ connects the two cerebral hemispheres.

  1. limbic system
  2. corpus callosum
  3. cerebellum
  4. pituitary


Neurons in the ________ control motor reflexes.

  1. thalamus
  2. spinal cord
  3. parietal lobe
  4. hippocampus


Free Response

What methods can be used to determine the function of a particular brain region?

To determine the function of a specific brain area, scientists can look at patients who have damage in that brain area and see what symptoms they exhibit. Researchers can disable the brain structure temporarily using transcranial magnetic stimulation. They can disable or remove the area in an animal model. fMRI can be used to correlate specific functions with increased blood flow to brain regions.

What are the main functions of the spinal cord?

The spinal cord transmits sensory information from the body to the brain and motor commands from the brain to the body through its connections with peripheral nerves. It also controls motor reflexes.

35.4: The Peripheral Nervous System

The peripheral nervous system (PNS) is the connection between the central nervous system and the rest of the body. The central nervious system (CNS) is like the power plant of the nervous system. It creates the signals that control the functions of the body. The PNS is like the wires that go to individual houses. Without those “wires,” the signals produced by the CNS could not control the body (and the CNS would not be able to receive sensory information from the body either).

Review Questions

Activation of the sympathetic nervous system causes:

  1. increased blood flow into the skin
  2. a decreased heart rate
  3. an increased heart rate
  4. increased digestion


Where are parasympathetic preganglionic cell bodies located?

  1. cerebellum
  2. brainstem
  3. dorsal root ganglia
  4. skin


________ is released by motor nerve endings onto muscle.

  1. Acetylcholine
  2. Norepinephrine
  3. Dopamine
  4. Serotonin


Free Response

What are the main differences between the sympathetic and parasympathetic branches of the autonomic nervous system?

The sympathetic nervous system prepares the body for “fight or flight,” whereas the parasympathetic nervous system allows the body to “rest and digest.” Sympathetic neurons release norepinephrine onto target organs; parasympathetic neurons release acetylcholine. Sympathetic neuron cell bodies are located in sympathetic ganglia. Parasympathetic neuron cell bodies are located in the brainstem and sacral spinal cord. Activation of the sympathetic nervous system increases heart rate and blood pressure and decreases digestion and blood flow to the skin. Activation of the parasympathetic nervous system decreases heart rate and blood pressure and increases digestion and blood flow to the skin.

What are the main functions of the sensory-somatic nervous system?

The sensory-somatic nervous system transmits sensory information from the skin, muscles, and sensory organs to the CNS. It also sends motor commands from the CNS to the muscles, causing them to contract.

35.5: Nervous System Disorders

A nervous system that functions correctly is a fantastically complex, well-oiled machine—synapses fire appropriately, muscles move when needed, memories are formed and stored, and emotions are well regulated. Unfortunately, each year millions of people in the United States deal with some sort of nervous system disorder.

Review Questions

Parkinson’s disease is a caused by the degeneration of neurons that release ________.

  1. serotonin
  2. dopamine
  3. glutamate
  4. norepinephrine


________ medications are often used to treat patients with ADHD.

  1. Tranquilizer
  2. Antibiotic
  3. Stimulant
  4. Anti-seizure


Strokes are often caused by ________.

  1. neurodegeneration
  2. blood clots or burst blood vessels
  3. seizures
  4. viruses


Free Response

What are the main symptoms of Alzheimer’s disease?

Symptoms of Alzheimer’s disease include disruptive memory loss, confusion about time or place, difficulties planning or executing tasks, poor judgment, and personality changes.

What are possible treatments for patients with major depression?

Possible treatments for patients with major depression include psychotherapy and prescription medications. MAO inhibitor drugs inhibit the breakdown of certain neurotransmitters (including dopamine, serotonin, norepinephrine) in the synaptic cleft. SSRI medications inhibit the reuptake of serotonin into the presynaptic neuron.

35.E: The Nervous System (Exercises) - Biology

Nervous system worksheets and online exercises
Language: English Subject: Biology

Reflec Arc
Grade/level: 11
by lailaramlan212

Human nervous system
Grade/level: Form 4/5
by Mr_Apish797

Nervous system
Grade/level: class x
by bijayiniswain

Nervous control in human
Grade/level: Form 4/5
by Mr_Apish797

Biology LP 8 D 6
Grade/level: high school
by dminson

Nervous system
Grade/level: class x
by bijayiniswain

ICSE Solutions for Chapter 8 The Nervous System Class 10 Selina Biology

(Select the most appropriate option in each case).
Question 1: The insulating sheath covering the neural axon is called.
(a) plasmalemma (b) neurolemma
(c) dura mater (d) pia mater

Solution 1: (b) neurolemma

Question 2: Which one of the following pairs of brain part and its function is not correctly matched?

(a) Cerebrum – Memory
(b) Cerebellum - Balance of body
(c) Medulla oblongata - controls activites of internal organs
(d) Pons - Consciousness

Solution 2: (d) Pons - consciousness

Question 3: A mixed nerve is one which
(a) carries sensations from 2 or more different sense organs
(b) contains both sensory and motor fibres
(c) has a common root but braches into two or more nerves to different organs
(d) has two or more roots from different parts of brain.

Solution 3: (b) Contains both sensory and motor fibres

B. Very Short Answer Type

Question 2: Note the relationship between the first two words and suggest the suitable word/words for the fourth place.
(a) Stimulus: Receptor:: Impulse: .
(b) Cerebrum: Diencephalon:: Cerebellum: .
(c) Receptor: Sensory nerve:: Motor nerve: .

Solution 2: (a) Stimulus: Receptor:: Impulse: Effectors
(b) Cerebrum: Diencephalon:: Cerebellum: Medulla oblongata
(c) Receptor: Sensory nerve:: Motor nerve: Effector

Question 3: Complete the following statements by choosing the correct alternative from the choice given in brackers:
contains cell bodies of
(a) The dorsal root ganglion of the spinal cord (motor/sensory/intermediate) neurons.

(iv) peripheral nervous system

Solution 3: (a) Sensory
(b) Maintaining posture and equilibrium
(c) Spinal cord

C. Short Answer Type

Question 1: Mention where in human bosy are the following located and state their main function: (a) corpus callosum (b) central canal

Solution 1: (a) Corpus Callosum: It is located located in the forebrain. It connects two cerebral
hemispheres and transfers information from one hemisphere to other.

(b) Central Canal: It is located in centre of the spinal cord. It is in continuation with the cavities
of the brain. It is filled with cerebrospinal fluid and acts as shock proof cushion. In addition, it also helps in exchange of materials with neurons.

Question 2: State whether the following statements are true (T) or false (F).
(a) The main component of the white matter of the brain is perikaryon
(b) The arachnoid layer fits closely inside the pia mater.
(c) A double chain of ganglia, one on each side of the nerve cord belongs to the spinal cord.
(d) Dura mater is the outermost layer of the meninges.

Solution 2: (a) False
(b) False
(c) True
(d) True

Question 3: Differentiate between following pairs with reference to the aspect in brackets.
(a) cerebrum and cerebellum (function)
(b) sympathetic nervous system and para – sympathetic nervous system (overall effect on body) (c) Sensory nerve and motor nerve (direction of impulse carried)
(d) medulla oblongata & cerebellum (function)
(e) cerebrum and spinal cord (arrangement of cytons and exons of neurons).

Solution 3:

The cerebrum controls all voluntary actions. It enables us to think, reason, plan and memorize.

The cerebellum on the other hand maintains balance of the body and coordinates muscular activity.

Sympathetic Nervous System

Parasympathetic Nervous System

Sympathetic nervous system prepares the body for violent action against the abnormal condition.

Parasympathetic nervous system is concerned with re-establishing normal conditions after the violent act is over.

Sensory Nerve

Motor Nerve

Sensory nerve brings impulses from the receptors i.e. sense organs to the brain or spinal cord.

Motor nerve carries impulse from the brain or spinal cord to effector organs such as muscles or glands.

Medulla Oblongata

Medulla oblongata controls the activities of internal organs and many other involuntary actions.

The cerebellum on the other hand maintains balance of the body and coordinate muscular activity.

Spinal Cord

The grey matter containing cytons lies in the cortex (outer region) while the white matter containing axons lies in the medullary region (inner region).

The grey matter containing cytons lies in the medullary region i.e. inner side while matter containing axons lies in the cortex i.e. the outer region.

Question 4: Given below are two structures, write their special functional activity.
(a) cerebellum and .
(b) Myelin sheath and .

Solution 4: (a) Cerebellum maintains balance of the body and coordinates muscular activity.
(b) Myelin sheath acts like an insulation and prevents mixing of impulses in the adjacent axons.

Question 5: Write the functions of the following:
(a) synapse
(b) Association neuron
(c) medullary sheath
(d) Medulla obiongata
(e) cerebellum
(f) Cerebrospinal fluid

Solution 5: (a) Synapse: It is a gap between the axon terminal of one neuron and the dendrites of the adjacent neuron. It transmits nerve impulse from one neuron to another neuron.

(b) Association Neuron: It interconnects sensory and motor neurons.

(c) Medullary sheath:It provides insulation and prevents mixing of impulses in the adjacent axons.

(d) Medulla Oblongata: It controls activities of internal organs such as peristalsis, breathing and many other involuntary actions.

(e) Cerebellum: It maintains balance of the body and coordinates muscular activity.

(f) Cerebrospinal Fluid: It acts like a cushion and protects the brain from shocks.

Question 6: what do we refer to in the nervous system when we say:
(a) sensory, motor and mixed .
(b) somatic and autonomic .
(c) Natural and conditioned
(d) sensory, motors and association .
(e) Gray and white

Solution 6: (a) Sensory, motor and mixed nerves
(b) Somatic and autonomic nervous system
(c) Natural and conditioned reflexes
(d) Sensory, motor and association neurons
(e) Gray and white matter

Question 7: Rearrange the following in correct sequence pertaining to what is given within brackets at the end.
(a) Effector . sensory neuron . Receptor. motor neuron. Stimulus. central nervous system. Response (Reflex arc)

(d) diencephalon . Cerebellum . medulla oblongata . Pons . Cerebrum . mid-brain (sequence of parts of human brain).

Solution 7: (a) Stimulus --- receptor --- sensory neuron --- central nervous system --- motor neuron ----- effector --- response

(b) Resting --- depolarization --- repolarization

(c) Dendrites --- Dendron --- perikaryon --- nucleus --- axon --- axon endings

(d) Cerebrum --- diencephalon --- mid-brain --- cerebellum --- pons --- medulla oblongata

D. Long Answer Type

Type of Reflex

(iii) Contraction of eye pupil

(v) Knitting without looking

(vi) Sudden application of brakes of the cycle on sighting an obstacle in front

Question 2: What are the advantages of having a nervous system?

Solution 2: The advantages of having a nervous system are as follows:
(a) Keeps us informed about the outside world through sense organs.
(b) Enables us to remember, think and reason out.
(c) Controls and harmonizes all voluntary muscular activities such as running, holding, writing
(d) Regulates involuntary activities such as breathing, beating of the heart without our thinking about them.

Question 3: Why do you call the spinal cord and the brain as the central nervous system?

Solution 3: The brain and the spinal cord lie in the skull and the vertebral column respectively. They have an important role to play because all bodily activities are controlled by them. A stimulus from any part of the body is always carried to the brain or spinal cord for the correct response. A response to a stimulus is also generated in the central nervous system. Therefore, the brain and the spinal cord are called the central nervous system.

Question 4: What is the difference between reflex action and voluntary action?

Solution 4: Reflex actions are involuntary actions which occur unknowingly. Voluntary actions on the other hand are performed consciously.
Picking up an apple and eating it is an example of voluntary action whereas withdrawal of hand on touching a hot object is an example of reflex action.

Reflex Action

Voluntary Action

Reflex actions are involuntary actions which occur unknowingly.

Voluntary actions on the other hand are performed consciously.

Commands originate in the spinal cord, autonomic nervous system and a few in the brain as well.

Commands originate in the brain.

Sympathetic System

Parasympathetic System

Dilates bronchi and bronchioles

Constricts bronchi and bronchioles

Inhibits the secretion of saliva causing the drying of the mouth

Stimulates the release of saliva

E. Structured/Application/Skill Type

Boy B starts salivating but not A. Explain the reason for this difference.

Solution 1: Salivation is an example of conditioned reflex that develops due to experience or learning. Saliva starts pouring when you chew or eat food. Therefore, this reflex will occur not just on the sight or smell of food. The brain actually needs to remember the taste of food. Boy B started salivating because he must have tasted that food prior unlike boy A.

Question 2: Given below are a few situations. What effective change will occur in the organ/body part mentioned and which part (sympathetic or parasympathetic) of the autonomic nervous system brings it about?

Organ/body part


Part of autonomic nervous system involved

1. You have entered a dark room

2. Your body is consuming lot of glucose while running a race

3. You are chewing a tasty food

5. You are retiring to bed for sleep

6. You are shivering in intense cold

Organ/body part


Part of autonomic nervous system involved

1. You have entered a dark room

2. Your body is consuming lot of glucose while running a race

Glycogen is converted into glucose in liver

3. You are chewing a tasty food

Release of adrenaline and noradrenaline increases

5. You are retiring to bed for sleep

6. You are shivering in intense cold

Solution 3: Fill in the following information in the diagram.
1 Central Nervous System
2 - Autonomic
3 - 12
4 - spinal
5 - 31
6 - dilates
7 - constricts
8 - liver

Review Questions

A. Multiple Choice Type

(d) Ciliary muscles

Solution 1: (b) Cornea

Question 2: Which part of our ear is shaped like a snail shell?
(a) Semi circular canals
(b) Cochlea
(c) Stapes
(d) Eustachian tube

Solution 2: (b) Cochlea

Question 3: The three parts of human ear contributing in hearing are
(a) cochlea, ear ossicles and tympanum
(b) semicircular canals, utriculus and sacculus
(c) eutachian tube, tympanum and utriculus
(d) perilymph, ear ossicle and semicircular canals.

Solution 3: (c) eutachian tube, tympanum and utriculus

Question 4: The region in the eyes where the rods and cones are located is the
(a) retina

(d) sclera

Solution 4: (a) retina

B. Very Short Answer Type

Question 1: Name the following:
(a) The photosensitive pigment present in the rods of the retina.
(b) The part which equalizes the air pressure in the middle and external ear.
(c) The ear ossicle attached to the tympanum
(d) The outermost covering layer of the brain
(e) The tube which connects the cavity of the middle ear with the throat
(f) The part of the eye responsible for its shape.
(g) The nerves which transmit impulse from ear to the brain
(h) The photoreceptors found in the retina of the eye.
(i) The eye defect caused due to shortening of the eye ball from front to back.

Solution 1: (a) Rhodopsin
(b) Eustachian tube
(c) Hammer
(d) Dura mater
(e) Eustachian tube
(f) Cornea
(g) Auditory nerves
(h) Rods and cones
(i) Hypermetropia

Question 2: Note the relationship between the first two words and suggest the suitable word/words for the fourth place.
(a) Cones : Iodopsim :: Rods : .
(b) sound : ear drum :: Dynamic balance : .

Solution 2: (a) Cones: Iodopsin:: rods: rhodopsin
(b) Sound: ear drum:: dynamic balance: semi-circular canals

Question 3: Which one or more of the expressions in column II are appropriate for the items listed in column I? write the correct matching pairs-

(c) protective covering of the brain

(d) basic unit of brain (e) free of rod cells

(c) protective covering of the brain

C. Short Answer Type

Question 1: Differentiate between members of each of the following pairs with reference to what is asked in brackets.
(a) Myopia and hyperopia (cause of the defect)
(b) Rods and cones (sensitivity)

(c) Semi-circular canal and cochlea (Senses perceived)
(d) Rod and cone cells (pigment contained)
(e) Dynamic balance and static balance (Definition)

Solution 1: (a) Myopia results when the eye ball is lengthened from front to back or the lens is too curved. Hyperopia results from either too shortening of the eyeball from front to back or when the lens is too flat.

(b) Rods are sensitive to dim light but do not respond to colour. Cones are sensitive to bright light and are responsible for colour vision.

(c) cochlea is responsible for hearing it can perceive the senses of hearing.

(d) Semicircular canals are responsible for perceiving the senses to maintain the body balance.

(e) Rod cells contain rhodopsin whereas the cone cells contain iodopsin.

(f) Dynamic balance is when the body is in motion whereas static balance is positional
balance with respect to gravity.

Question 2: State whether the following statements are True (t) or False, correct them by changing any one single word in each.
(a) Deafness is caused due to rupturing of the pinna
(b) Semi circular canals are concerned with static (positional) balance.

Solution 2: (a) False
Correct statement: Deafness is caused due to rupturing of the eardrum.

(b) Organ of corti

Solution 3: (a) Fovea centralis is located at the back of the eye almost at the centre of the eyeball. It is the region of the brightest vision and also of the colour vision.

(b) Organ of corti is located in the inner ear. It contains sensory cells which process hearing.

Question 4: Mention if the following statements are true (T) or false (F) Give reason.
(a) Sometimes medicines dropped into the eyes come into the nose and even throat
(b) Ciliary muscles regulate the size of the pupil
(c) yellow spot of the retina is the region of colour vision
(d) The auditory nerve is purely for perceiving sound
(e) Malleus incus and stapes are collectively called the ear ossicles
(f) Flavour and taste are one and the same thing.
(g) short-sightedness and hyperopia are one and the same thing
(h) Blind spot is called so because no image is formed on it.

Solution 4: (a) True
(b) False/Ciliary muscles regulate the size of the lens.
(c) True
(d) False/The auditory nerve responsible for sound as well as for the body balance.
(e) True
(f) False/flavour is a combination of taste and smell.
(g) False/short-sightedness is myopia and hyperopia is long-sightedness.
(h) True

Question 5: Given below are two sets (a) and (b) of five parts in each. Rewrite them in correct sequence.
(a) Cochlea, tympanum, auditory canal, ear ossicles, oval window.
(b) Conjunctiva, retina, cornea, optic nerve, lens

Solution 5: (a) Auditory canal, tympanum, ear ossicles, oval window, cochlea
(b) Conjunctiva, cornea, lens, retina, optic nerve

Question 6: Given below are certain structures. Write against them their functional activity.
(a) organ of corti and .
(b) Olfactory nerve and .
(c) retina and .
(d) Taste bud and .

Solution 6: (a) Organ of Corti and hearing
(b) Olfactory nerve and smell
(c) Retina and vision
(d) Taste bud and taste

Question 7: Answer the following:
(a) What is a lacrimal gland?
(b) In what two ways is the yellow spot different from the blind spot?
(c) Name an old age eye defect. What happens in it?
(d) What is meant by power of accommodation of the eye?
(e) Mention the characteristics of the image that falls on the retina of the eye.

Solution 7: (a) Lacrimal gland is a tear gland located at the upper sideward portion of the eye orbit. Its secreation lubricates the surface of the eye, washes always the dust particles and kills germs

(b) Yellow spot is the region of brightest vision and contains maximum sensory cells whereas
a blind spot contains no sensory cells and this is the point of no vision.

(c) Presbyopia is an age-old eye defect. In this condition, the lens loses flexibility resulting in far-sightedness.
Cataractis also very common in old people, the cornea becomes opaque and the vision is cut down even to blindness.

(d) The process of focusing the eye at different distances is called the power of

(e) The image formed on the retina is inverted and real.

Question 8: What is meant by optical illusion? Give one example.

Solution 8: An optical illusion is the life-like continuous movement on the screen. Television is an example of optical illusion, where the scanning beam of a picture frame of the TV camera moves so rapidly on the viewing screen of the TV set that our eyes cannot keep pace with it.

Question 9: Where are the following located? Briefly mention the function of each:
(a) oval window

(b) Cochlea
(c) Semicircular canals
(d) Utriculus

Solution 9: (a) Oval window is located in the middle ear. It helps in setting the fluid in the cochlear canals into vibration.

(b) Cochlea is located in the inner ear. It helps in transmitting impulses to the brain via the auditory nerve.

(c) Semicircular canals are located in the inner ear. These help in maintaining the dynamic equilibrium of the body.

(d) Utriculus is located in the inner ear. It joins the semi-circular canals to cochlea. It also helps in maintaining static balance of the body.

Question 10: Name the four principal tastes and the respective regions of the tongue concerned with their perception.

Solution 10: The four principal tastes are sweet, salt, bitter and sour.

35.E: The Nervous System (Exercises) - Biology

Body temperature is primarily regulated by an area in the brain known as the hypothalamus. The hypothalamus sets the body’s temperature and controls it by opening and closing sweat glands and contracting muscles.

The integumentary system helps regulate body temperature through its tight association with the sympathetic nervous system, the division of the nervous system involved in our fight-or-flight responses. The sympathetic nervous system is continuously monitoring body temperature and initiating appropriate motor responses.

Recall that sudoriferous glands, accessory structures to the skin, secrete sweat to cool the body when it becomes warm. Even when the body does not appear to be noticeably sweating, approximately 500 mL of sweat (insensible perspiration) are secreted a day. If the body becomes excessively warm due to high temperatures, vigorous activity (Figure 1), or a combination of the two, sweat glands will be stimulated by the sympathetic nervous system to produce large amounts of sweat, as much as 0.7 to 1.5 L per hour for an active person. When the sweat evaporates from the skin surface, the body is cooled as body heat is dissipated.

In addition to sweating, arterioles in the dermis dilate so that excess heat carried by the blood can dissipate through the skin and into the surrounding environment (Figure 1). This accounts for the skin redness that many people experience when exercising.

Figure 1. During strenuous physical activities, such as skiing (a) or running (c), the dermal blood vessels dilate and sweat secretion increases (b). These mechanisms prevent the body from overheating. In contrast, the dermal blood vessels constrict to minimize heat loss in response to low temperatures (b). (credit a: “Trysil”/flickr credit c: Ralph Daily)

When body temperatures drop, the arterioles constrict to minimize heat loss, particularly in the ends of the digits and tip of the nose. This reduced circulation can result in the skin taking on a whitish hue. Although the temperature of the skin drops as a result, passive heat loss is prevented, and internal organs and structures remain warm. If the temperature of the skin drops too much (such as environmental temperatures below freezing), the conservation of body core heat can result in the skin actually freezing, a condition called frostbite.

Deep breathing tips

Here are some ways to up your deep breathing game.

Try different breathing patterns

There are many different ways to breathe deeply, so play around to find one that feels natural to you. Try breathing in for four counts, then out for six. Or try square breathing: in for four, hold for four, out for four, hold for four. As long as you’re still keeping your breathing slow and deep, there’s no pattern that’s better than the others.

Practice self-compassion

Be kind to yourself as you practice deep breathing. Recognize that you might not notice results immediately, and that’s OK. Give yourself credit for trying, and keep practicing, even just for a few minutes at a time, until you reach a point where you notice it’s starting to help you manage your stress. Then keep at it. Deep breathing isn’t like riding a bike you have to do it regularly for it to be helpful.

Be mindful

Being mindful can enhance your deep breathing practice. Mindfulness is about recognizing your emotions and what’s going on in your body without judging any of it as bad or good. To be mindful during deep breathing, focus on your breath and let any thoughts fade away. Don’t judge yourself for having them, but don’t pursue them try to let them go. Notice if your body is tense or if your mind keeps trying to go back to a particular unpleasant topic, but don’t get down on yourself—just recognize what’s going on as a way of gathering information about yourself and your stress response.

Find a guide

If trying to guide your own deep breathing isn’t working well, try a phone app or website or audiobook that will guide you through the practice. You might find it helpful to record yourself talking through a breathing exercise and then playing it back when you want to practice. Or, if you need peer support, ask a friend to join you or research local meditation groups.

Interplay of the nervous and endocrine systems

The endocrine system is an organ system which consists of various glands around the body (examples of which are the Hypothalamus, Pituitary gland, Parathyroid gland, Thyroid gland, Adrenal glands, Pancreas, Ovaries in females and Testies in the male body). These glands secrete hormones directly into the bloodstream.

The nervous system is an organ system consisting of many different specialized cells (called neurons) which &lsquocoordinate the actions of a person and transmit signals between different parts of its body&rsquo[1]. In our bodies the nervous system is made up of two parts: the central nervous system and the peripheral nervous system. The central nervous system consists of the brain, spinal cord, and the retina. The peripheral nervous system consists of sensory neurons, clusters of neurons which are called ganglia, and nerves which connect them to each other and to the central nervous system. All of these regions are all interconnected by means of complex neural pathways.

The hypothalamus is a gland which is found in the brain and it links the endocrine system and the nervous system together. The hypothalamus receives different information from all of the main areas that make up the brain and other organs. The hypothalamus is able to registers a variety of feeling and sensations such as pain, temperature, hunger, thirst, stress, fear, and anger. Then, once this information has been sent to the hypothalamus (part of the endocrine system) and has been registered, it works with the autonomic nervous system (part of the peripheral nervous system) to affect and administer changes to various organs. Examples of any effects or changes are an increased heart or lung rate, &lsquoincreased blood flow to your skeletal muscles or digestive organs, changes in how much light enters your eyes and how well your eyes can focus on distant objects, production of sweat or shivers, and arousal of sexual organs.&rsquo[2] So because of the ability of the hypothalamus to link and affect both the nervous and the endocrine systems, it is called a neuroendocrine tissue a specialized type of tissue.

The endocrine system and the nervous system work in parallel with each other and in conjunction with each other in order to maintain homeostasis, development and reproduction. Both of these organ systems are the communication links of the body and help the body&rsquos life systems to function correctly and in relation to each other. In terms of function, both the nervous and endocrine systems work hand in hand with one another by acting in communication and driving hormonal changes. They both work in maintaining homeostasis and they both respond to internal and external changes to the body. Besides functioning in similar ways they both work in conjunction with each other. An example of this can be seen in a mother&rsquos release of milk. When a baby sucks at the nipple of its mother, the sensory cells in the nipple send out signals to the hypothalamus. The hypothalamus then responds by releasing the hormone oxytocin from the posterior pituitary gland. The oxytocin is released directly into the bloodstream where it moves to its target cell, which for this example is a mammary gland. The mammary gland then responds to the signals from the oxytocin hormone by releasing milk through the nipple. Besides working in conjunction with each other, both systems also affect one another. The adrenal medulla is under the control of nerve cells, but the nervous system&rsquos development is under the control of the endocrine system.[3]

Further example as to how the nervous and endocrine systems are interrelated:

Someone is walking along a street at night when they spot a group of people in front of them, all of them carrying knives and other threatening objects. Because it is night, the person&rsquos eyes would take some time to adjust and actually spot the group of people. When they do and their eyes detect the group, their brain would tell them that it may harm them. The hypothalamus in the brain, uses the autonomic nervous system to very quickly help the eyes to adjust and to see better. It uses the brain in order to think more quickly, and your heart, lungs, and large skeletal muscles to allow you to run faster if required or fight off the group with more strength.

The autonomic nervous system would help in stimulating some of the above reactions by stimulating the release of epinephrine and norepinephrine from another region of the adrenal glands (the inner portion). This is another way in which the nervous and endocrine systems are intertwined in their roles and influences over many of the body&rsquos physiological activities.

By way of the endocrine system, the person&rsquos hypothalamus would stimulate the production and the release of cortisol (which is a glucocorticoid) from another region of the adrenal gland (the outside of the adrenal gland). These glucocorticoids would increase the production of glucose, which would therefore ensure that the person has a sufficient amount of energy or fuel in order to fight or to run away from the group of people.

In this situation, adrenalin may also be produced from the adrenal medulla (another gland that is part of the endocrine system). The adrenalin hormone is released as a response to the individual&rsquos feelings of anxiety, during exercise (if the person runs away) or fear. This is why adrenalin is known as the fright, flight or fight hormone. These responses (of staying and fighting the group or running from the group) would both require a lot more blood and oxygen to be present in the muscles.

If the person is scared, it will cause the brain to send signals to the renal glands which would then begin to pump a large amount of adrenalin into the bloodstream. This would then increase the heart rate and the breathing rate in order to prepare for what the person is going to do (run or fight). The heart rate and breathing rate would increase and the airways of the lungs would widen. The person would now have fast shallow chest breathing as opposed to slow relaxed breathing.

The autonomic nervous system is split up into two sub systems the sympathetic and the parasympathetic nervous system. In the example above it is the sympathetic nervous system which would control the body&rsquos responses. When aroused, this is the system that begins to increase the person&rsquos heart rate and breathing rate, their pupils would begin to dilate and they may begin to start sweating (the fight or flight response). The nerve impulses travel at approximately 150 meters per second which means that this stage of the fight or flight response can take place very quickly in milliseconds.

Once the danger has passed (the group of people have moved away), it is the parasympathetic nervous system which would then counteract the sympathetic nervous system. This is the system that would then help to calm the body, gradually slowing the person&rsquos heart and breathing rates, their pupils would contract and the sweating would stop.

[1] Kandel ER, Schwartz JH, Jessel TM, ed. (2000). &ldquoCh. 2: Nerve cells and behavior&rdquo. Principles of Neural Science. McGraw-Hill Professional. ISBN 9780838577011.

Biology 12, the nervous system, senses and endocrine test

Test on the Nervous System. Format: 20 multiple choice questions. -We will conclude our discussion of the Endocrine system.. Nelson Biology 12 $105.95 (Sept 2008)
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Biology II Practice Tests. Fundamentals of the Nervous System and Nervous Tissue Ch 12. Ch 16: The Special Senses Ch 17: The Endocrine System

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. Chapter 12 Nervous System 3 Mastery Test. CHAPTER 12 NERVOUS SYSTEM Ill: SENSES OVERVIEW This chapter. MASTERY TEST Now take the. 1 Chapter 12 The Nervous System Biology 3201.
THE DIGESTIVE SYSTEM (REVISED 3/12/07) THE NERVOUS SYSTEM (REVISED 6/22/01). The Online Biology Book is hosted by Estrella.

Reaction Time: The Ruler Drop Test

The nervous system helps information travel through your body. It consists of the 5 senses, your brain, your spinal column, and the nerves that connect them all together. Suppose your eyes see a baseball sailing toward your head. They send a message about the approaching ball to your brain. This message travels to a part of your brain called the cerebrum through nerves. Your cerebrum sends this information to the cerebellum, which has to choose whether to move away, duck, or put a hand up to catch the ball. It finally decides that you should catch it&mdashafter all, you&rsquore wearing your baseball glove! The cerebellum sends this decision as message through other nerves to the arm and hand, activating the muscles used to catch the ball.

The time it takes from when your eye first notices the ball to when your arm reaches up to catch it is an example of reaction time. Even though stimuli&mdashor changes in your environment that you react to&mdashtravel very quickly along your nervous system as messages, your body doesn&rsquot react instantly. Many athletes spend hours practicing to improve their reaction time. In this activity, you will conduct a simple, measurable experiment (the ruler drop test) to study reaction time and determine how it can be improved with practice.


How can reaction time be measured and improved?



  1. Ask your first volunteer to sit in the chair with good upright posture and eyes looking across the room.
  2. Have the volunteer place her forearm (the part of the arm from elbow to hand) so it extends over the edge of the table.
  3. Ask the volunteer to place her thumb and index (pointer) finger on either side of the bottom of the vertically placed ruler. The number &ldquo1&rdquo should be on the bottom, the &ldquo30&rdquo near the top.
  4. Let your volunteer practice holding the ruler with those two fingers.
  5. Now, ask your volunteer to remove her fingers from the ruler while you continue hold it so that the bottom of the ruler is at a height of 2cm above her fingers.
  6. Tell your volunteer that you will release the ruler without telling her. Her job will be to catch it with her thumb and forefinger as soon as she senses it dropping.
  7. Drop the ruler. When your volunteer catches it, record the number on the ruler displayed just over her thumb. The lower the number, the faster her reaction time.
  8. Conduct several trials with the same volunteer, dropping the ruler from 2cm above her fingers each time.
  9. Make sure to record the results for each trial in a table similar to the following:
  1. You might consider letting your volunteers have a rest between trials.
  2. Repeat the experiment with at least one other volunteer.


Your results will vary depending on technique and which volunteers you used, but you should expect that many of your volunteers will show a slight improvement with practice.

When we begin to acquire a new physical skill through repetition, our nervous system creates new neural pathways. Here&rsquos an example: when we practice something like catching a ruler over and over again, all the members of that neural pathway (eye, brain, muscles) become more well-connected and efficient. This phenomenon is often referred to as muscle memory. However, no matter how good your muscle memory for this task becomes, it will always take some time for the falling ruler to travel as a message from your eyes to your brain and from your brain to your fingers!

Going Further

Reflexes in response to stimuli are our quickest reactions. One example is when a doctor hits a spot right below your kneecap and you kick before you even consciously realize you&rsquore doing so. One cool question to explore might be whether reflexes and learned motor skills like catching a ruler can enable us to respond to stimuli more quickly in the morning or in the evening. How does the length of time spent awake affect the efficiency of our central nervous system? Why?

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The peripheral nervous system is made up of all of the nerves and nerve cells that are external to the central nervous system.

The function of the peripheral nervous system is to relay information from the central nervous system to the rest of the body, and from the body back to the central nervous system.

The peripheral nervous system can also be broken down into two subdivisions - the somatic nervous system and the autonomic nervous system.

Avoid Overanalyzing Central Nervous System Fatigue

Many forms of fatigue affect the body. They are complex. Gaining a complete picture is futile.

The journey to do so may paralyze you. Those that venture down this road come to reach rather bizarre, narrow-minded conclusions. They avoid focusing on the right things and sift through countless grains of sand to find diamonds.

They may very well come to understand a piece of the puzzle but then overemphasize its role and ignore its relationship with the whole.

Balance your training, rest, and nutrition variables. Avoid overtraining that comes from exercising too much, too long, and too often. Get enough sleep, rest, and food.

This is all rather simple and easy to figure out. What people lack though is self-discipline. They seek quick and easy fixes.

If you train ideally to positive failure within any reasonable rep range, perhaps with an upper limit of 30 reps due to energy systems, you will recruit the fast-twitch fibers most responsible for the changes you want.

I suggest moderate reps not so much due to any dread of CNS burnout but because lifting too closely to your 1 RM can be dangerous. The idea that you can train close to your 1 RM to focus on strength and limit muscle growth is false as well. You do not need to lift close to your 1 RM to gain strength and size at the fastest rate. Powerlifters and Olympic lifters need to work close to this limit only for their sport.

Beginners can thrive with 2-3 bouts of an exercise per week. They may need to eventually consider once a week though. They can determine when they need to change because they hit an insurmountable plateau.

Progress embodies everything. Judge your results by progress alone, by improving a tad in weight or reps from session to session. This will summarize any complexity with a simple measurement.

If you experience CNS fatigue, it reveals a problem. This fatigue is real, but avoid dwelling on it alone. Consider the advice here as a way to perceive it correctly.

Watch the video: How do nerves work? - Elliot Krane (January 2022).