Characteristic feature of human cornea 
The outermost layer of the eye ball is fibrous in nature. Two-third part of this layer is opaque and lies inside the eyeorbit and is known as sclera.The remaining one-third of the outer layer is transparent and bulges out to form the cornea.There is no supply of blood in cornea.
Which of the following statements is correct for ‘nodes of Ranvier’ of nerve? 
Neurons are the chief functional units of the nervous system. An ordinary neuron has a soma or cyton and a long thread called axon which is enclosed in a multilayered myelin sheath, made by Schwann cells. The myelin sheath is interrupted at the spaces between schwann cells to form gaps. These gaps are called Nodes of Ranvier.
These nodes and the myelin sheath create condition that speed up the nerve impulses.
In which animal nerve cell is present but brain is absent? 
A primitive type of nervous system, without brain is found in the form of intra epidermal nerve net. However, there is no brain in Hydra to coordinate the response.
Ommatidia serve the purpose of photoreception in 
Cockroach has compound eye composed of many units called ommatidia. It comprises a cornea lens, crystalline cone, a graph of usually 7–8 retinal cells radially arranged around a central rhabdome
Injury to vagus nerve in humans is not likely to affect 
Muscles of the tongue are invested by the 12th cranial nerve, Hypoglossal. The 10th cranial nerve, vagus supplies the viscera of the thorax, abdominal region and thus controls gastrointestinal, cardiac movements and pancreatic secretion.
In the resting state of the neural membrane, diffusion due to concentration gradients, if allowed, would drive 
In a resting state of the neural membrane, Na+ concentration is higher on the outer side and K+ concentration is more within the cell. This concentration gradient is maintained by voltage gated channels. Hence if diffusion is allowed Na+ would enter the cell and K+ would leave.
Four healthy people in their twenties got involved in injuries resulting in damage and death of a few cells of the following. Which of the cells are least likely to be replaced by new cells? 
The neurons are cells specialised to conduct an electrochemical current. Neuron cells do not have the capability of division.
In a man, abducens nerve is injured. Which one of the following functions will be affected? 
Abducens nerve is the sixth cranial nerve. It supplies the extraocular muscle (superior oblique) of eyeball, therefore controls movement of the eyeball.
One of the examples of the action of the autonomous nervous system is 
Autonomic nerveous system regulates and coordinates involuntry activities like heart beat, homeostasis, body temperature, breathing, gut peristalsis and secretion of glands. Human intestine shows movements during food digestion called peristalsis.
During the transmission of nerve impulse through a nerve fibre, the potential on the inner side of the plasma membrane has which type of electric change? 
Once the events of depolarization have occurred, a nerve impulse or spike is initiated. Action potential is another name of nerve impulse. It lasts about 1 msec (millisecond). The stimulalted, negatively charged point on the outside of the membrane sends out an electrical current to the positive point (still polarized adjacent to it). This local current causes the adjacent inner part of the membrane to reverse its potential from –70 mV to +30 mV. The reversal repeats itself over and over until the nerve impulse is conducted through the length of the neuron
Which of the following is an example of negative feedback loop in humans? 
When the set point of hypothalamus is disturbed by high temperature, it stimulates vasodilation and sweating while in low temperature there is vasoconstriction and shivering.
Which one of the following pairs of structures distinguishes a nerve cell from other types of cells? 
The cytoplasm immediately surrounding the nucleus is loaded with protein synthetic machinery and is called perikaryon, dendrites are usually shorter, tapering and much branched processes which may be one to several. These two are only present in nerve cells.
Given below is a diagrammatic cross section of a single loop of human cochlea: 
Which one of the following options correctly represents the names of three different parts?
The diagramnatic cross section of a single loop of human cochlea represents the three different parts- A- Perilymph B- Tertorial membrane C-Endolymph Cochlea arises from sacculus. It is spirally coiled duct. It is also known as Lagena. It is connected with sacculus by duct of Reunies.
Which one of the following is the correct difference between Rod Cells and Cone Cells of our retina? 
Rod cells is a type of light sensitive receptor cell present in the retinas of vertebrates. Rod contains the pigment rhodopsin and are essential for vision in dim light. Cone cells is a type of light sensitive receptor cell, found in retinas of all diurnal vertebrates. Cones are specialized to transmit information about colour and are responsible for the visual acuity of the eye. They function best in bright light
During the propagation of a nerve impulse, the action potential results from the movement of : 
During the propagation of nerve impulse when a stimulus of adequate strength is applied to a polarised membrane, the permeability of the membrane to Na+ is greatly increased at the point of stimulation. As a result the sodium ion channels permit the influx of Na+ by diffusion. Since, there are more Na+ ions entering than leaving, the electrical potential of the membrane changes from - 70 mV towards zero. At 0 mV the membrane is said to be depolarised. While the resting potential is determined largely by K+ ions, the action potential is determined largely by Na+ ions. Action potential is another name of nerve impulse. The stimulated negatively charged point on the outside of the membrane sends out an electrical current to the positive point adjacent to it. This local current causes the adjacent inner part of the membrane to reverse its potential from -70 mV to-+30 mV.
Cornea transplant in humans is almost never rejected. This is because 
Cornea transplant in humans is almost never rejected. This is because it has no blood supply. Cornea is a transparent layer of tissue, continuous with the sclerotic, that forms the front part of the vertebrate eye, over the iris and lens
Alzheimer disease in humans is associated with the deficiency of: 
Alzheimer disease in humans is associated with the deficiency of acetylcholine. Acetylcholine is the neurotransmitter produced by neurons referred to as cholinergic neurons. Acetylcholine plays a role in skeletal muscle movement, as well as in the regulation of smooth muscle and cardiac muscle. Acetylcholine is synthesized from choline and acetyl coenzyme-A through the action of the enzyme choline acetyltransferase and becomes packaged into membranebound vesicles.
Which part of human brain is concerned with the regulation of body temperature? 
Hypothalamus part of human brain is concerned with the regulation of body temperature. The hypothalamus is a portion of the brain that contains a number of small nuclei with a variety of functions. The hypothalamus is small cone-shaped structure, projects downward, ending in the pituitary.
The nerve centres which control the body temperature and the urge for eating are contained in: 
Hypothalamus contains important nerve centres that controls the body temperature, thirst, hunger and eating, water balance and sexual function.
When a neuron is in resting state I not conducting any impulse, the axonal membrane is: 
When a neurone is in resting state i.e., not conducting any impulse, the axonal membrane is comparatively more permeable to K+ ion and nearly impermeable to Na+ ions.
The purplish red pigment rhodopsin contained in the rods type of photoreceptor cells of the human eyes is a derivative of
There are two types of photoreceptor cells of retina, namilyrods and cones. The rods contain a purplish red protein called the rhodopsin or visual purple, which contains a derivative of vitamin - A.
The human hind brain comprises three parts, one of which is : 
The human hind brain comprises of pons, cerebellum and medulla oblongata.
Which part of the human ear plays no role in hearing as such but is otherwise very much required? 
Vestibular apparatus is a part of inner ear which has no role in hearing but responsible for the maintenance of balance of the body and posture.
A person entering an empty room suddenly finds a snake right in front on opening the door. Which one of the following is likely to happen in his neuro-hormonal control system ? 
Epinephrine and norepinephrine are secreted by adrenalmedulla in response to stress of any kind and during emergency situations and are called emergency hormones or hormones of flight, or fight.
The most abundant intracellular cation is : [NEET 2013]
The most abundant intracellular cation is K+.
A diagram showing axon terminal and synapse is given. Identify correctly at least two of A-D. [NEET 2013]
A-Receptor, C-Synaptic vesicles B is synaptic cleft. A synapse is formed by the membranes of a synaptic neuron and post synaptic neuron, which may or may not separated by a gap called synaptic cleft. It is filled by fluid called neurotransmitter which are involved in transmission of impulse at these synapses.
A sagittal section of human-brain is shown here. Identify at least two labels from A-D. [NEET Kar. 2013]
Cerebrum is the first and most developed part of fore brain. It makes 2/3 part of total brain. Pons is a small spherical projection, which is situated below the midbrain and upper side of the medulla oblongata. It acts as a relay centre among different parts of brain. B and D are thalamus and spinal cord respectively.
The figure shows an axon terminal and synapse. Select the option giving correct identifications of tables A-D [NEET Kar. 2013]
In the given figure, A, B, C and D are axon, neurotransmitters, receptors and synaptic vesicles respectively.