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Cranial Nerves Spinal Nerves 1. There are 12 pairs of cranial nerves. 1. There are 31 pairs of spinal nerves. 2. They arise from the brain and extend to the other parts of the body. 2. They arise from the spinal cord and extend to other parts of the body. 3. They may be sensory, motor or mixed. 3. They are mixed nerves.
Blind Spot Yellow Spot 1. It is the point on the retina at which the optic nerve leaves the eye and retinal blood vessels enter the eye. 1. It is the point on the retina which lies exactly opposite the centre of the cornea. 2. It is void of photoreceptor cells. 2. It contains two kinds of photoreceptor cells-rods and cones. 3. It is insensitive to light. 3. It is very...
Aqueous Humour Vitreous Humour 1. It is present in the aqueous chamber between the lens and the cornea. 1. It is present in the vitreous chamber between the lens and the retina. 2. It is secreted by the ciliary processes. 2. It is secreted by the retina of the eye. 3. It is a jelly-like fluid. 3. It is a watery fluid. 4. It supports the lens. 4. It supports the...
Impulse Conduction in a Myelinated Nerve Fibre Impulse Conduction in Non-myelinated Nerve Fibre 1. Impulse travels from node to node. 1. Impulse travels along the length of the entire nerve fibre. 2. The speed of conduction is 50 times faster than the non-myelintaed nerve fibre. 2. The speed of conduction is slower. 3. Energy expenditure during impulse transmission is...
Afferent Neurons Efferent Neurons 1. They conduct sensory impulses from the receptors to the central nervous system.   1. They conduct motor impulses from the central nervous system to the effector organs such as muscles. 2. They are present in the sense organs.   2. They are present in the brain and the spinal cord. 3. They are sensory neurons.   3. They are motor neurons.
Cerebrum Cerebellum 1. It is the largest part of the brain. 1. It is the second-largest part of the brain. 2. It is part of the forebrain. 2. It is part of the hindbrain. 3. The cerebrum is divided into two cerebral hemispheres. 3. The cerebellum is divided into three lobes-central vermis and the two lateral cerebellar hemispheres. 4. It is the site of memory and...
Thalamus Hypothalamus 1. It is made of only grey matter. 1. It is made of white and grey matter. 2. The thalamus does not secrete any hormone. 2. The hypothalamus secretes certain hormones which control the activity of the pituitary gland. 3. It is situated superior to the midbrain. 3. It is situated at the base of the thalamus. 4. It contains the centres of...
Rods Cones 1. They are sensitive to dim light. 1. They are sensitive to bright light. 2. Rods contain the pigment rhodopsin. 2. Cones contain the pigment iodopsin. 3. They have no role to play in colour vision. 3. They are responsible for colour vision. 4. Only one kind of rods exist. 4. There are three kinds of cones-red, blue and green.
Dendrites Axons 1. They are short processes. 1. Axons are long processes. 2. Dendrites carry impulses towards the cell body of the neuron. 2. Axons carry impulses away from the cell body of the neuron. 3. Dendrites are always branched. 3. Axons may or may not be branched. 4. Nissl's granules are present in the neuroplasm. 4. Nissl's granules are absent in the...
Myelinated Axons Non-myelinated Axons 1. Myelin sheath is present.  1. Myelin sheath is absent. 2. Nodes of Ranvier are present.  2. Nodes of Ranvier are absent.  It is found in the grey matter of the brain, spinal cord, and autonomous nervous system. 3. It is found in the white matter of the brain, spinal cord and autonomous nervous system. 4. The conduction of nerve impulse is...
From the perilymph, the vibrations are transferred to the scala vestibuli of the cochlea and then to the scala media through Reissner's membrane and stimulate the sensory hair of the organ of Corti. The impulses thus received by the hair cells are carried to the brain through the auditory nerve where the sensation of hearing is felt. 
The photosensitive compounds (photo pigments) in the human eye are composed of opsin and retinal. Light induces dissociation of retinal and opsin which changes the structure of opsin. It generates an action potential in the bipolar neurons. These impulses/action potential are transmitted by the optic nerves to the visual cortex of the brain where the neural impulses are analysed and the erect...
Sodium ions diffuse from the outside to the intracellular fluid because of the electrochemical gradient. The potassium ions move out, and the membrane becomes negatively charged from outside and positively charged from inside. This sudden change in the membrane potential is called the action potential, and the membrane is said to be depolarised.
Light enters the eye through the pupil, an aperture present in the centre of the iris. The iris has two types of muscles-circular smooth muscles and radial smooth muscles-which regulate the amount of light which falls on the retina. The smooth circular muscles contract in bright light which makes the pupil smaller in size; hence, lesser amount of light falls on the retina. In dim light, the...
Crista ampullaris present in the three semicircular canals, the macula utriculi present in the utricle and the macula sacculi present in the saccule of the inner ear help us in maintaining body balance. 
Cone cells present in the retina of the eye are responsible for colour vision. There are three kinds of cone cells which respond to red, green and blue light. Different cone cells get stimulated at different wavelengths of light. The other colours are detected by the simultaneous stimulation of more than one kind of cone cells. When all the three types of cells are stimulated simultaneously, a...
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