Chapter 18: Neural Control and Coordination Short Questions | biology Class 11 CBSE

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Chapter 18: Neural Control and Coordination Short Questions | biology Class 11 CBSE | ByteNotes.in

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Question 1

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What is coordination? Give one example from daily life to illustrate it.

Coordination is the process through which two or more organs interact and complement the functions of one another.
During physical exercise, muscles, lungs, heart, blood vessels, and kidneys all work together to meet the increased energy and oxygen demand.
When exercise stops, the activities of all these organs gradually return to their normal conditions, showing coordinated regulation.

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Question 2

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Name the two systems that coordinate all body activities and state the mode of action of each.

The neural system and the endocrine system jointly coordinate and integrate all activities of the organs.
The neural system provides an organised network of point-to-point connections for quick coordination.
The endocrine system provides chemical integration through hormones, which is comparatively slower.

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Question 3

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Distinguish between afferent and efferent nerve fibres.

Afferent nerve fibres transmit impulses from tissues and organs to the CNS (sensory direction).
Efferent nerve fibres transmit regulatory impulses from the CNS to the concerned peripheral tissues and organs (motor direction).
Both types are components of the Peripheral Neural System (PNS) and together enable two-way communication between the CNS and body parts.

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Question 4

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What are Nissl's granules? Where are they found in a neuron?

Nissl's granules are granular bodies found in the cytoplasm of a neuron and are involved in cellular metabolism.
They are present in the cell body (soma) of the neuron, along with typical cell organelles.
Nissl's granules are also found in dendrites, but are absent in the axon.

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Question 5

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What is a synaptic knob? State its significance.

A synaptic knob is a bulb-like structure at the terminal end of each branch of an axon's distal end.
It possesses synaptic vesicles that contain chemicals called neurotransmitters.
The synaptic knob is the site where neurotransmitters are released into the synaptic cleft to transmit impulses to the post-synaptic neuron.

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Question 6

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Classify neurons on the basis of the number of axons and dendrites.

Multipolar neurons have one axon and two or more dendrites and are found in the cerebral cortex.
Bipolar neurons have one axon and one dendrite and are found in the retina of the eye.
Unipolar neurons have a cell body with only one axon and are found usually in the embryonic stage.

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Question 7

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Differentiate between myelinated and non-myelinated axons.

Myelinated axons are enveloped by Schwann cells that form a myelin sheath around the axon, with gaps called nodes of Ranvier between adjacent sheaths.
Non-myelinated axons are enclosed by a Schwann cell that does not form a myelin sheath around the axon.
Myelinated fibres are found in spinal and cranial nerves, while non-myelinated fibres are found in the autonomous and somatic neural systems.

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Question 8

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What is resting potential? How is the resting potential maintained across the axonal membrane?

Resting potential is the electrical potential difference across the plasma membrane when a neuron is not conducting any impulse, with the outer surface positively charged and the inner surface negatively charged.
It is maintained by the sodium-potassium pump, which actively transports 3 Na+ outward and 2 K+ into the cell.
The axonal membrane is also more permeable to K+ and nearly impermeable to Na+ and negatively charged intracellular proteins, contributing to the charge separation.

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Question 9

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What is an action potential? How does it differ from resting potential?

Action potential is the electrical potential difference across the plasma membrane at a site of stimulation, where the outer surface becomes negatively charged and the inner side becomes positively charged; it is also termed a nerve impulse.
Resting potential exists when the neuron is not conducting any impulse, with the outer membrane positively charged; action potential is generated only when the membrane is stimulated and depolarised.
The resting potential is maintained by selective ion permeability and the Na+-K+ pump, while action potential arises from rapid influx of Na+ following stimulation.

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Question 10

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State the role of potassium ions (K+) in the repolarisation of the axonal membrane.

After the action potential is generated, the rise in Na+ permeability is extremely short-lived and is quickly followed by a rise in permeability to K+.
Within a fraction of a second, K+ diffuses outside the membrane, restoring the positive charge on the outer surface.
This outward movement of K+ restores the resting potential at the site of excitation, making the fibre once more responsive to further stimulation.

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Question 11

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What is a synapse? Name the two types of synapses.

A synapse is a junction formed by the membranes of a pre-synaptic neuron and a post-synaptic neuron through which nerve impulses are transmitted from one neuron to another.
There are two types of synapses: electrical synapses and chemical synapses.
At electrical synapses, pre- and post-synaptic membranes are in very close proximity allowing direct current flow; at chemical synapses, a fluid-filled synaptic cleft separates the two membranes.

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Question 12

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Why is impulse transmission across an electrical synapse faster than across a chemical synapse?

At electrical synapses, the membranes of pre- and post-synaptic neurons are in very close proximity, allowing electrical current to flow directly from one neuron to the next.
This direct current flow does not require the release, diffusion, and receptor binding of neurotransmitters, which is the time-consuming step at chemical synapses.
Thus, transmission across an electrical synapse is analogous to impulse conduction along a single axon, making it inherently faster.

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Question 13

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What are neurotransmitters? Where are they stored and how are they released?

Neurotransmitters are chemicals involved in the transmission of impulses at chemical synapses between neurons.
They are stored in synaptic vesicles present in the axon terminals (synaptic knobs) of the pre-synaptic neuron.
When an action potential arrives at the axon terminal, it stimulates the synaptic vesicles to move towards and fuse with the pre-synaptic plasma membrane, releasing neurotransmitters into the synaptic cleft.

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Chapter 18: Neural Control and Coordination | Short Questions

What is coordination? Give one example from daily life to illustrate it.

Name the two systems that coordinate all body activities and state the mode of action of each.

Distinguish between afferent and efferent nerve fibres.

What are Nissl's granules? Where are they found in a neuron?

What is a synaptic knob? State its significance.

Classify neurons on the basis of the number of axons and dendrites.

Differentiate between myelinated and non-myelinated axons.

What is resting potential? How is the resting potential maintained across the axonal membrane?

What is an action potential? How does it differ from resting potential?

State the role of potassium ions (K+) in the repolarisation of the axonal membrane.

What is a synapse? Name the two types of synapses.

Why is impulse transmission across an electrical synapse faster than across a chemical synapse?

What are neurotransmitters? Where are they stored and how are they released?

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