Question 1

Draw a labelled diagram of reflex arc and explain reflex action.

Accepted Answer

The reflex arc describes the pathway in which the nerve impulse is carried and the response is generated and shown by the effector organ. The reflex arc typically consists of five components: 1. The receptor is present in the receptor organ. 2. The sensory neuron conducts the nerve impulses towards the central nervous system (CNS). The CNS is comprised of the brain and the spinal cord. 3. The information is transferred from one neuron to other. 4. A motor neuron conducts the response nerve from the CNS to the effector organ. 5. The effector organ shows response by contracting or secreting a product.The instant movement performed by the individual in response to the stimulus is known as a reflex action.

Question 2

The order of three layers of cells in retina of human eye from inside to outside is

Accepted Answer

Correct option: CExplanation:The retina is the innermost layer of the eye and is responsible for sight.It is connected to the brain with the help of the optic nerve.The outermost layer of cells is the photoreceptor cells that detect light and low light vision.Next to them are the bipolar cells that perceive the signal.Innermost is the ganglionic cells that form the optic nerve and transmit information.Hence, the order of three layers of cells in the retina of the human eye from inside to outside is &#34;Ganglion cells, bipolar cells, photoreceptor cells&#34;.

Question 3

Explain the process of conduction of a nerve impulse along a nerve fibre.

Accepted Answer

The nerve fibre is at resting phase when it is not stimulated by any impulse. They possess a potential difference along the membrane which is known as resting potential (-70mv). The membrane is negatively charged inside due to the lower concentration of potassium ions and positively charged outside due to the high concentration of sodium ions. When an electrical stimulus is received by a nerve fibre, an action potential is generated. The membrane becomes permeable to sodium ions than to potassium ions. This results in a positive charge inside and negative charge outside the nerve fibre. Hence, the membrane is said to be depolarised.The potential generated at this phase is known as the action potential. As the action potential reaches its maximum value, the membrane potential gets reversed and this state is known as repolarization. By sequential activity of the nerve conduction, it reaches the terminal end of the axon and stimulates the synaptic vesicles which release the neurotransmitters. The neurotransmitters cross the synaptic membrane and reach the dendrite of the next neuron.

Question 4

Which one of the following is not an effect of sympathetic nervous system?

Accepted Answer

The sympathetic nervous system is involved in the stimulation of activities that prepare the body for action, such as increasing the heart rate, increasing the release of sugar from the liver into the blood, and other generally considered as fight-or-flight responses (responses that serve to fight off or retreat from danger). The parasympathetic nervous system activates tranquil functions, such as stimulating the secretion of saliva or digestive enzymes into the stomach.

Question 5

Given is a diagram depicting a defect of the human eye. Study the same and answer the questions that follow:(a) Name the defect shown in the diagram.(b) Give two possible reasons for this defect.(c) Name the paws labeled 1 to 4.(d) Name the type of lens used to correct this eye defect.(e) Draw a labelled diagram to show how the above mentioned defect is rectified using the lens named above.

Accepted Answer

(a) The figure depicts myopia defect also known as nearsightedness(b) The possible reason for this defect is:     (1) It occurs when the eye grows too long from front to back as instead of focusing on the retina the lens of the eye focuses the image in front of the retina     (2) It can also occur when the cornea is too curved for the length of the eyeball or a lens that is too thick.(c) The parts labelled in the diagram are as follows:1. is vitreous humour2. is the blind spot3. is Lens4. is Pupil(d) The lens used to correct myopia is a concave lens, the concave lens diverge the light rays, and as a result, the image will form on the retina.(e) The attached figure shows how myopia is rectified

Question 6

Which is the correct sequence of the components of a reflex arc?

Accepted Answer

When a receptor is stimulated, it sends a signal to the central nervous system, where the brain coordinates the response. But sometimes a very quick response is needed, one that does not need the involvement of the brain. This is called as the reflex action. In a simple reflex action:Stimulus -> Receptor -> Sensory neuron -> Relay Neuron -> Motor neuron -> Effector (Muscle).So, the correct answer is 'Receptors - Sensory neuron - Spinal cord - Motor neuron - Muscle'

Question 7

The diagram given below is a representation of a certain phenomenon pertaining to the nervous system. Study the diagram and answer the following questions.(i) Name the phenomenon that is being depicted. (ii) Give the technical term for the point of contact between the two nerve cells. (iii) Name the parts 1, 2, 3 and 4.(iv) Write the functions of parts 5 and 6. (v) How does the arrangement of neurons in the spinal cord differ from that of the brain ?

Accepted Answer

i) The phenomenon that is depicted here is the reflex action which is an involuntary and instant movement in response to stimuli. (ii) The term for the point of contact between the two nerve cells is called the synapse. (iii) (1). Sensory (Afferent neuron)     (2). Dorsal ganglion       (3). White matter                            (4). Grey matter (iv) The function of 5 (Synapse): It transmits the sensory impulse from sensory neurons to the motor neurons.The function of 6 (Motor neuron/Efferent neuron): It transmits the command to the effectors part (e.g. muscles).v) The arrangement of neurons in the spinal cord differs from that of the brain. In the brain, Gray matter is present on the outside and white matter on the inner side. In Spinal cord, white matter is present on the outside and Gray matter on the inner side.

Question 8

Which one of the following is not a part of brain stem?

Accepted Answer

Human brain along with spinal cord makes up the central nervous system of the body. The brain consists of the cerebrum, brain stem, and cerebellum. The brain stem consists of midbrain, pons, and medulla. On the dorsal aspect of the midbrain, corpora quadrigemina: four colliculi, two inferior and two superior are found, which are reflex center involving vision and hearing. Whereas cerebrum is the part of the forebrain.Hence, the correct answer is option A.

Question 9

Put the following parts of a reflex arc in the correct order beginning with the sensory receptor.A. Motor neuron    B. Interneuron    C. Effector    D. Sensory neuron     E. Sensory receptor

Accepted Answer

Most reflex arcs have five main components:  receptors, sensory neurons,interneurons, motor neurone and muscles.Neurons have special proteins called receptors. Receptors respond to signals in the environment like pressure, pain, vibrations, light etc.Sensory neurons have sensory receptors, they get activated by the signal from the environment. The activated sensory neurons extend into spinal cord sending an electrical signal to another neuron, the interneuron.Interneuron then relays the signal to the motor neuron. Motor neuron run out of spinal cord and connect with the muscle or effector.Thus the correct sequence is a sensory receptor, sensory neuron, interneuron, motor neuron and last effector.

Question 10

Integration of visual, tactile and auditory inputs occurs in

Accepted Answer

Integration of visual, tactile, and auditory inputs occurs in the midbrain. The upper surface of the midbrain has two pairs of rounded protrusions called corpora quadrigemina, one pair is called superior colliculi which is concerned with the sense of sight, and the other pair is called inferior colliculi which is concerned with hearing.So, the correct answer is option D.