1. SENSATIONS AND RESPONSES 

Class 10 Biology - Focus Area covered Notes

1. What is the function of nervous system ? 

A) To generate and coordinate responses according to external and internal changes.

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2. Define stimulus.

A) The senses that evoke responses in organisms are called stimuli. These are two types,

* External stimuli :- Sound, touch, heat, chemicals, pressure, cold, radiations... 

* Internal stimuli :- Hunger, touch, infection, pressure variation, thirst, exhaust...

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3. Name the parts included in our nervous system.

A) Brain, spinal cord, nerves and receptors. 

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4. The structural and functional units of the nervous system?

A) Neurons (nerve cells).

• dendrites

• Dendron

• axonite

• Axon

• Cell body /Cyton

• Myelin sheath / Scwann cells

• Synaptic knobs

A neuron has mainly the following parts; a cyton (cell body), impulse receiving dendrons (branches are known as dendrites), impulse transmitting axon (branches are axonites) and synaptic knobs for secreting neurotransmitter. In certain neurons, the nerve fibres are covered by myelin sheath, made up of white shining Schwann cells.

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5. The protective covering of nerve fibres (axons)? Mention its function,

A) Myelin sheath.

• Provide nutrients and oxygen to the axon. Accelerate impulses.

• Act as an electric insulator.

• Protects the axon from external shocks.

• Gives white appearance ('white matter') to the neural parts.

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6. Table showing the function of different parts of nerve cell.

• Part of nerve cell

           👇

• Dendrite

           👇

• Dendron

            👇

• Cyton / Cellbody

            👇

• Axon

             👇

• Receives impulses

              👇

• Function

               👇

• Carries impulses from dendrite to the cell body

                👇

• Passes impulses to the axon. Carries impulses from the cell body to outside.

                  👇

• Schwann cells/ Myelin sheath Protects the axon and increases the speed of impulse

               👇

• Axonite

                👇

• Synaptic knob

                👇

• Carries impulses to the synaptic knob

                  👇

• Secretes neurotransmitter

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7. Name the swollen ends of axon. How is it important in the transmission of impulse ?

A) Synaptic knobs, from which neurotransmitter secretes. The impulses are transmitted across the synaptic cleft only through a chemical (neurotransmitter), secreted from the synaptic knobs.

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8. Give example for neurotransmitter.

A) Acetyl choline (Dopamine is another example).

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9. Define synapse.

A) The junction between neurons or between neurons and muscles or glands is known as the synapse. It helps to regulate the speed and direction of impulses. The impulses are transmitted across the synaptic cleft only through a chemical (neurotransmitter), secreted from the synaptic knobs.

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10. The electrical messages conducted through nerves ?

A) Impulses.

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11. How is the impulses transmits through the neurons ?

A) Impulse due to stimulus dendrites dendrons cytone axon axonites synaptic knob secretion of neurotransmitter to the synaptic cleft Stimulation in the adjacentd dendrites Impulse forms.

When impulses reach at the synaptic knobs, a chemical substance, known as neurotransmitter, released in the synaptic cleft. This chemical stimulates the adjacent dendrites to form new electric impulses.

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12. Name the two types of neurons ?

A) Sensory neurons - (carry impulses from different body parts to the brain and spinal cord) Motor neurons - ( carry impulses from the brain and spinal cord to various parts of body)

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Define a nerve ?

A) A nerve is a group of axons or nerve fibres, covered by connective tissue.

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14. Show different kinds of nerves with their functions in a table.

Sensory nerves

(consists of sensory neurons)

Motor nerves

(consists of motor neurons)

Mixed nerves

(consists of sensory and motor neurons)

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15. How is human nervous system classified ?

Central Nervous System

- Brain - Spinal cord

Carry impulses from sense organs to the brain and spinal cord

Carry impulses from brain and spinal cord to different organs

Carry impulses from brain and spinal cord to different

organs and vise versa

Peripheral Nervous System

- Cranial nerves (12 pairs) - Spinal nerves (31 pairs)

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16. The protective measures for human brain ?

Inside a hard skull and is covered by a three layered membrane, called the meninges. Cerebrospinal fluid, a fluid formed inside the meninges, also protects the brain.

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17. The outer covering of brain and spinal cord

Meninges.

?

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18. The fluid which provides nutrients and oxygen to brain tissues ? Give its function ?

Cerebrospinal fluid (CSF).

CSF provides nutrients and oxygen to brain tissues.

Regulates the pressure inside the brain.

Protects brain from injuries.

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19. Name the functional parts of human brain.

A) Human brain has outer cerebrum, cerebellum and medulla oblongata and inner thalamus and hypothalamus.

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21. There are many fissures and folds in the cerebral cortex (the peripheral part of brain), What is the advantage of this ?

A) This is an adaptation to include more number of neurons and there by increase the efficiency of cerebrum.

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23. Any mild injury to the medulla oblongata may lead to sudden death. Why ?

A) Medulla oblongata controls involuntary actions like heart beat and breathing. Any mild injury to medulla oblongata results malfunctioning of breathing and heartbeat and this may lead to death.

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24. The central nerve, seen as the continuation of medulla oblongata ? How is this part protected ? Spinal cord. It is protected inside the vertebral column and is covered by the meninges. 25. The - of the spinal cord is filled with cerebrospinal fluid.

Central canal

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26. Mention the functions of spinal cord. •

Transmitting impulses from different parts of our body to and from the brain. Coordinates the rapid and repeated movements during walking, running etc.

Effects certain reflex actions.

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27. What do you mean by reflex action ?

Reflex actions are the accidental and involuntary responses of the body, These are two types, 1. Cerebral reflexes 2. Spinal reflexes

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28. The table showing neural disorders, reason and symptoms.

Disorder

Alzheimer's

Parkinsons

Epilepsy

Cause

Continuous degeneration of neurons due to the accumulation of an insoluble protein.

in response to a stimulus.

Symptom

Complete loss of memory.

Degeneration of specific ganglia in the brain Loss of body balance. Tremor in muscles, due to the deficiency of dopamine flow of saliva

Discharge of irregular electrical impulses from brain.

Fits (due to uncontrolled muscular contractions), frothy discharge from mouth, clenching of teeth, unconsciousness

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29. Name a neurotransmitter, which is secreted in the brain. What will happen when the production of this hormone cease in a person ?

Dopamine. The deficiency of dopamine may result a disease called parkinsons.

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