Biology 3 Marks Question

Dendrites and axons:

	Dendrites		Axons
1.	Dendrite is a small projection arising from the neuron. It conducts the nerve impulse toward the cell body.	1.	Axon is a single, long projection that conducts the nerve impulse away from cell body to the next neuron.
2.	Nissl’s granules are present in dendrites.	2.	Nissl’s granules are absent from axons.
3.	Dendrites are always non-myelinated.	3.	Axons can be myelinated or non-myelinated.

The middle ear contains a flexible chain of three middle bones called ear ossicles. The three ear ossicles are as follows.

1. Malleus
2. Incus
3. Stapes

The malleus is attached to tympanic membrane on one side and to incus on the other side. The incus is connected with stapes. Stapes, in turn, are attached with an oval membrane, fenestra ovalis, of internal ear. The ear ossicles act as a lever that transmits sound waves from external ear to internal ear.

Blind spot 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.	1.	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.	3.	They are sensitive to bright light as cones are present.

Rods and cones:

	Rods		Cones
1.	Rods help in twilight vision.	1.	Cones help in colour vision.
2.	They have visual purple pigment called rhodopsin.	2.	They have visual violet pigment called iodopsin.
3.	Rods are the photoreceptor cells of the retina that are sensitive to dim light.	3.	Cones are the photoreceptor cells of the retina that are sensitive to bright light.

Central neural system (CNS) and Peripheral neural system (PNS):

	Central neural system		Peripheral neural system
1.	It is the main coordinating centre of the body.	1.	It is not the main coordinating centre of the body.
2.	It includes brain and spinal cord.	2.	It includes cranial and spinal nerves that connect central nervous system to different parts of the body.

The symptoms of dizziness and vomiting, faced by a person travelling at higher altitude is because of the following reasons The function of Eustachian tube is to equalise the pressure on either sides of the ear drum; sudden elevation in height causes disturbance in maintaining pressure by this area of ear. The semicircular ducts, the anterior, posterior and lateral semicircular ducts, are enlarged at one end to give rise to ampulla. Each ampulla contains sensory path of hairs, the cristae, which is concerned with the balancing of the body, Change in altitude brings changes in the reorientation and adjustments in these structures of internal ear causing the above said symptoms.

Dendrites and axons:

	Dendrites		Axons
1.	Dendrite is a small projection arising from the neuron. It conducts the nerve impulse toward the cell body.	1.	Axon is a single, long projection that conducts the nerve impulse away from cell body to the next neuron.
2.	Nissl’s granules are present in dendrites.	2.	Nissl’s granules are absent from axons.
3.	Dendrites are always non-myelinated.	3.	Axons can be myelinated or non-myelinated.

1. The cause of Vijay's sickness is the change of altitude in which there is change in the physiology of the body.
2. Internal ear gets affected which control balancing of body.
3. Eustachian tube maintains the air pressure in the ear.
4. The guide is a very sensible person and is caring too.

The human brain is made up of two types of matter the outer grey matter and inner white matter. Grey matter is nothing but it is due to collection of cytons/ cell bodies/ soma of neurons and non-myelinated neurons which appears grey in colour hence called grey matter. White matter is due to collection of myelinated neurons hence called white matter. Outer grey matter and inner white matter is present in cerebrum, cerebellum while outer white matter and inner grey matter is present in pons, medulla oblongata and spinal cord.

1. Multipolar neurons:

1. A multipolar neuron has one axon and many dendrons.
2. They are found in the cerebral cortex.

2. Bipolar neurons:

1. A bipolar neuron has one axon and one Dendron.
2. They are found in retina.

3. Unipolar neurons:

1. Cell body has only one axon.
2. They are found in the embryonic stage.

The correct order of involvement in electrical impulse movement.

1. Dendrites.
2. Cell body.
3. Axon.
4. Axon terminal.
5. Synaptic knob.

1. No, actually he was not able to differentiate colours.
2. In human, colours vision results from the activity of cone cells of retina of eyes as these contain three different pigments each absorbing light of different wavelength. The sensation of different colours are produced by various combination of these cones and their pigments.
3. The daylight vision and colour vision are functions of cones cells of retina.
4. The teacher showed his concerns about his student.

A neuron is a microscopic structure composed of three major parts, namely, cell body, dendrites and axon Cell Body. The cell body contains cytoplasm with typical cell organelles and certain granular bodies called Nissi's granules.

• Dendrites: Short fibres which branch repeatedly and project out of the cell body also contain Nissi's granules and are called dendrites. These fibres transmit impulses towards the cell body.
• Axon: The axon is a long fibre, the distal end of which is branched. Each branch terminates as a bulb-like structure called synaptic knob which possess synaptic vesicles containing chemicals called neurotransmitters. The axons transmit nerve impulses away from the cell body to a synapse or to a neuro-muscular junction.

1. The cranial meninges has three layers:

1. The outermost, dura mater.
2. The middle, arachnoid.
3. The innermost, pia mater.

2.  

1. Cerebrum is concoined with memory, intelligence and motor signalling to skeletal muscles.
2. Hypothalamus has centres to control body temperature, thirst and hunger and secretes neurohormones.
3. Medulla has centres which control cardiovascular reflexes, gastric secretions and respiration.
4. Cerebellum controls the coordination of muscular activities and the posture of the body.

1. Coordination and integration of body organs by neural system. Which regulate normal physiology of human body.
2. Coordination is the process through which two or more organs interact and complement the functions of one another. On the other hand, integration is a process, which makes two or more organs to work as a functional unit in harmony.
3. When we do exercise, we observe significant increase in the rate of respiration, heartbeat, bloodflow, sweating, etc., to meet enhanced needs of nutrients and energy for increased activities of lungs, hearts, muscles and many other body organs. When we stop exercising, we witness that the increased activities of lungs, heart, nerves, kidneys, muscles, etc., gradually return to normal. Thus, during exercise, functions of various organs of the body are coordinated and integrated.
4. He has a good knowledge of biology. He has the ability to apply his learning to the practical life.

The entire process of response to a peripheral neural stimulation, that occurs involuntarily, i.e., without conscious effort or thought and requires the involvment of a part of the central neural system is called a reflex action. The reflex pathway comprises at least one afferent neuron (receptor) and one efferent effector or excitor neuron appropriately arranged in a series. The afferent neuron receives signal from a sensory organ and transmits the impulse via a dorsal nerve root into the CNS (at the level of spinal cord). The efferent nueuron then carries signals from CNS to the effector. The stimulus and response thus forms a reflex arc as shown below in the knee jerk reflex.

The middle ear contains a flexible chain of three middle bones called ear ossicles. The three ear ossicles are as follows.

1. Malleus
2. Incus
3. Stapes

The malleus is attached to tympanic membrane on one side and to incus on the other side. The incus is connected with stapes. Stapes, in turn, are attached with an oval membrane, fenestra ovalis, of internal ear. The ear ossicles act as a lever that transmits sound waves from external ear to internal ear.

1. The cranial meninges consists of three layers:

1. The outer pia mater.
2. The middle arachnoid.
3. The inner dura mater.

2.  

1. The cerebellum integrates the information from semicircular canals of the ear and the auditory system.
2. The cerebrum is responsible for memory, communication and intersensory associations.

Blind spot 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.	1.	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.	3.	They are sensitive to bright light as cones are present.

Rods and cones:

	Rods		Cones
1.	Rods help in twilight vision.	1.	Cones help in colour vision.
2.	They have visual purple pigment called rhodopsin.	2.	They have visual violet pigment called iodopsin.
3.	Rods are the photoreceptor cells of the retina that are sensitive to dim light.	3.	Cones are the photoreceptor cells of the retina that are sensitive to bright light.

The limbic system is constituted by the inner part of the while matter of cerebral hemispheres) and deep seated structures like amygdala and hippocampus.Limbic system:

1. The regulation of sexual behaviour.
2. Expression of emotional reactions.
3. Motivation.
4. Olfaction.
5. Autonomic responses.

Central neural system (CNS) and Peripheral neural system (PNS):

	Central neural system		Peripheral neural system
1.	It is the main coordinating centre of the body.	1.	It is not the main coordinating centre of the body.
2.	It includes brain and spinal cord.	2.	It includes cranial and spinal nerves that connect central nervous system to different parts of the body.

1. Pavlov's experiment.
2. Pavlov's Experiment: The concept for which Pavlov experiment is done is to check the conditioned reflexes. Students conduct this experiment to know this concept of conditioned reflex, to examine the rate of salivations among dogs. Everytime when bell is rung they fed the dog. He learned that when the bell was rung without food being presented to the dog. The dog will subsequently initiate salivation. The dog had associated the sound of the bell with the feeding time. This shows to the association of an expected response (drool) to an unlikely stimulus (the bell).
3. Conditioned reflex is acquired after birth, i.e., they are adopted during the course of lifetime.
4. Scientific attitude, awareness and sense of responsibility.

1. Tumour in hypothalamus.
2. Hypothalamus.
3. The hypothalamus lies at the base of thalamus in the forebrain.
4. Humanity and responsibility towards the patient. He is devoted to his duties and has professional ethics.