Receptor sites for neurotransmitters are present on
1. membrances of synaptic vesicles
2. pre-synaptic membrane
3. tips of axons
4. post-synaptic membrane

Good vision depends on adequate intake of carotene rich food.

Select the best option from the following statements.

I. Vitamin-A derivatives are formed from carotene.
II. The photopigments are embedded in the membrane discs of the inner segment.
III. Retinal is a derivative of vitamin-A.
IV. Retinal is a light absorbing part of all the visual photopigments.

(1) (I) and (II)

(2) (I), (III) and (IV)

(3) (I) and (III)

(4) (II), (III) and (IV)

Myelin sheath is produced by
(1) Schwann cells and Oligodendrocytes

(2) Astrocytes and Schwann cells

(3) Oligodendrocytes and Osteoclasts

(4) Osteoclasts and Astrocytes

Choose the correct statement.
(1) Nociceptors respond to changes in pressure

(2) Meissner's corpuscels are thermoreceptors

(3) Photoreceptors in the human eye are depolarised during darkness and become hyperpolarised in response to the stimulus 

(4) Receptors do not produce graded potentials

Destruction of the anterior horn cells of the spinal cord would result in loss of 

(1) sensory impulses

(2) voluntary motor impulses

(3) commissural impulses

(4) integrating impulses

Stimulation of a muscle fibre by a motor neuron occurs at

1. the neuromuscular junction

2. the transverse tubules

3. the myofibril

4. the sacroplasmic reticulum

Which one of the following statements is not correct?

1. Retinal is the light absorbing portion of visual photopigments 

2. In retina the rods have the photopigment rhodopsin, while cones have three different

photopigments

3. Retinal is a derivative of vitamin-C

4. Rhodopsin is the purplish red protein present in rods only 

A diagram showing axon terminal and synapse is given. Identify correctly A-D.

1. A- Receptor                  C-synaptic Vesicles

2. B-Synaptic connection   D-K⁺

3. A-Neurotransmitter        B-Synaptic cleft

4. C-neurotransmitter        D-Ca²⁺        

Parts A, B, C and D of the human eyes are shown in the diagram. Select the option

which gives correct identification along with its functions/characteristics

1. A-retina-contains photoreceptors-rods and cones

2. B-blind spot-has only a few rods and cones

3. C-aqueous chamber-reflects the light which does not pass through the lens

4. D-choroidits anterior part forms ciliary body

Which part of the human ear plays no role in hearing as such but is otherwise very much

required?

1. Eustachian tube

2. Organ of Corti

3. Vestibular apparatus

4. Ear ossicles