Biology Class 11 NCERT Solutions: Chapter 21 Neural Control and Coordination Part 7

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Q: 10. Answer the following:

(A) Which part of the ear determines the pitch of a sound?

(B) Which part of the human brain is the most developed?

(C) Which part of our central neural system acts as a master clock?

Answer:

(A) Cochlea determines the pitch of a sound.

Figure shows the Cochlea

Figure Shows the Cochlea

Figure shows the Cochlea

(B) Forebrain is largest and the most developed part of the human brain.

Part of the human brain in figure

Part of the Human Brain in Figure

Part of the human brain in figure

(C) Hypothalamus acts as a master clock in the human body.

Hypothalamus in figure

Hypothalamus in Figure

Hypothalamus in figure

Q: 11. The region of the vertebrate eye, where the optic nerve passes out of the retina, is called the

(A) Fovea

(B) Iris

(C) Blind spot

(D) Optic charisma

Answer:

(C) Blind spot

Blind spot is the part where the optic nerve passes out of the retina. Photoreceptors are absent from this region.

Q: 12. Distinguish between:

(A) Afferent neurons and efferent neurons

(B) Impulse conduction in a myelinated nerve fibre and unmyelinated nerve fibre

(C) Aqueous humor and vitreous humor

(D) Blind spot and yellow spot

(F) Cranial nerves and spinal nerves.

Answer:

(A) Afferent neurons and efferent neurons

Q_12_A_Table of Afferent and Efferent Neurons
Q_12_A_Table of Afferent and Efferent Neurons

Afferent neurons

Efferent neurons

1

Afferent neuron conducts nerve impulses toward the brain or the spinal cord.

2

Efferent neuron conducts nerve impulses from the brain or spinal cord to the effector organs such as muscles or glands.

(B) Impulse conduction in a myelinated nerve fibre and an unmyelinated nerve fibre

Q_12_B_Impulse Conduction in a Myelinated and an Unmyelinated Nerve Fibre
Q_12_B_Impulse Conduction in a Myelinated and an Unmyelinated Nerve Fibre

Impulse conduction in a myelinated nerve fibre

Impulse conduction in an unmyelinated nerve fibre

1

In a myelinated nerve fibre, the action potential is conducted from one node to another.

2

In an unmyelinated nerve fibre, the action potential is not conducted from node to node. It is carried along the whole length of the nerve fibre.

2

The conduction of impulses is faster.

2

The conduction of impulses is slower.

(C) Aqueous humour and vitreous humour

Aqueous humour and vitreous humour

Aqueous Humour and Vitreous Humour

Aqueous humour and vitreous humour

Q_12_C_Table of Aqueous and Vitreous Humour
Q_12_C_Table of Aqueous and Vitreous Humour

Aqueous humour

Vitreous humour

1

It is a thin, watery fluid present between the cornea and the lens.

2

It is a transparent gel present between the lens and the retina.

(D) Blind spot and yellow spot

Q_12_D_Table of Blind and Yellow Spot
Q_12_D_Table of Blind and Yellow Spot

Blind spot

Yellow spot

1

Blind spot is a spot on the retina present at the point of origin of the optic nerve.

2

Yellow spot is a small area on the retina present at the posterior pole of the eye, lateral to the blind spot.

2

Photoreceptor cells are absent from this region.

2

Only cones are present in this region.

3

They are insensitive to light as both rods and cones are absent

They are sensitive to bright light as cones are present.

(F) Cranial nerves and spinal nerves

Q_12_F_Table of Cranial and Spinal Nerves
Q_12_F_Table of Cranial and Spinal Nerves

Cranial nerves

Spinal nerves

1

Cranial nerves arise from the brain.

2

Spinal nerves arise from the spinal cord.

2

There are 12 pairs of cranial nerves.

2

There are 31 pairs of spinal nerves.