Download Q1: What happens at the synapse between two neurons? Answer

Q1: What happens at the synapse between two neurons?
Answer: Synapse is a very small gap between the last portion of axon of one neuron and the dendron
of the other neuron. It acts as a one way valve to transmit impulses. This is one directional flow of
impulses because the chemicals are produced only on one side of the neuron i.e., the axon’s side.
Via axon, the impulses travel across the synapse to the dendron of the other neuron.
In toto, synapse performs the following tasks:
1. It allows the information to pass from one neuron to another.
2. It ensures the passage of nerve impulse in one direction only.
3. It helps in information processing by combining the effects of all impulses received.
Watch the you tube video explaining what is the Synapse structure and how it functions.
Q2: Which part of the brain maintains posture and equilibrium of the body?
Answer: Cerebellum.
Q3: How do we detect the smell of an agarbatti (incense stick)?
Answer: The fore-brain is the main thinking part of the brain. It has regions which receive sensory
impulses from various receptors. Separate areas of the fore-brain are specialised for hearing, smell,
sight and so on.
Olfactoreceptors (present in nose) send the information about the smell of incense stick to fore-brain.
The for-brain interprets it along with with information received from other receptors as well as with
information that is already stored in the brain.
Q4: List the functions performed by Cerebrum.
Answer: The cerebrum performs the following functions:
1. It governs our mental abilities like thinking, reasoning, learning, memorising etc.
2. It controls our feelings, emotions and speech.
3. It controls all involuntary functions.
Q5: Which is the largest and most prominent part of the brain.
Answer: Cerebrum
Three regions of Brain
Q6: What are the functions of cerebellum?
Answer:
1. Maintains equilibrium or balance of the body.
2. Coordinates muscular movement.
3. Controls posture of the body.
Q7: How brain is protected inside a human body?
Answer: Brain is protected by a bony box called cranium, within which are present 3 layers of fluidfilled (called cerebrospinal fluid) membranes (called meninges) for absorbing shock and buoyancy.
Q8: What is the role of the brain in reflex action?
Answer: Brain has no role to play in creation of reflex action response. Instead spinal cord is the
control centre of a reflex action. In fact brain becomes aware after the reflex arc has been formed.
Q9: What do you mean by reflex action? Give examples of reflex actions?
Answer: It is defined as fast, unconscious, immediate, automatic and involuntary response of the body
(through effectors) to a stimulus. It is monitored through spinal cord.
Examples of reflex actions:
1.
2.
3.
4.
5.
6.
Closing eyes when bright light falls on the eyes.
Knee-jerk
Withdraw Hands when pricked by a pin.
Choking stimulates cough reflex
Withdraw hand or leg when it touches an hot object.
Women knitting a sweater while watching TV (conditioned reflex).
Q10: What are the different types of reflexes?
Answer: There are two types of reflexes:


Unconditioned reflexes
Conditioned reflexes
Unconditioned or Unconditional reflexes are those which are inherited. Our brain does not learn these
reflexes. E.g. when we touch a hot plate, we immediately moves away our hand.
Conditioned reflexes are those which our brain has learned by repeating the action number of times.
e.g. a typist is typing a letter without looking at the typewriter keys.
Q11: What is reflex arc?
Answer: The structural and functional unit that carries our reflex action is called a reflex arc. It
consists of:





A receptor
sensory nerve (afferent)
Spinal Cord and Inter-neuron
motor nerve (efferent)
effector
Q12: What are plant hormones?
Answer: Plant hormones or phytohormones are naturally-occurring organic substances used as
chemical coordinators in plants. These are synthesized in one part of the plant body (in minute
quantities) and are translocated to other parts when required.
The five major types of phytohormones are:





auxins: promote cell division, bending of shoot towards the source of light.
gibberellins: stimulate stem elongation.
cytokinins: promote cell division.
abscisic acid: inhibit growth ,closing of stomata ,seed dormancy.
ethylene( gas hormone): promotes fruit ripening and growth.
Q13: Who coined the term phytohormones?
Answer: Thimann in 1948.
Q14: How is the movement of leaves of the sensitive plant different from the movement of a
shoot towards light?
Answer: The movement of leaves of the sensitive plant, (e.g. Mimosa pudica or touch-me-not) occurs
in response to touch or contact stimuli. It is a growth independent movement (nastic movement).
The movement of shoot towards light is called photo-tropism. This type of movement is directional
and is growth dependent.
Q15: Write differences between nastic and tropic movements
Answer:
Sno.
Nastic Movements
Tropic Movements
1. Growth
2.Time of Action
3. Response to Stimulus
4. Reason for action
5. Alternate name
Growth Independent movements
Immediate
non-directional
change in turgor
nastics
folding of leaves of
touch-me-not(mimosa),
Growth Dependent movements
Slow
directional
cell division
tropism
phototropism, geotropism,
hydrotropism, chemotropism
6. Examples
Sno.
Nastic Movements
Tropic Movements
opening and closing of stomata
Q16: What will happen when plant is exposed to unidirectional light?
Answer: Stem bends towards unidirectional flow of light. It is called phototropism.
Q17: What is chemotropism?
Answer: Directional movement of a plant/ or its part in response to chemicals is called chemotropism.
e.g. growth of the pollen tube towards the ovule is a chemotropic movement due to which fertilization
of flower takers place.
Q18: Give examples of geotropism.
Answer:
1. Roots move in the direction of gravity (positive +ve getropism)
2. Shoots move (up) against direction of gravity (negative -v geotropism)
Q19: Why do mammals like humans need an endocrinal system?
or
Q: What are the limitations of nervous system in human body? How it is overcome?
Answer: Nervous system in human body works or communicates using nerve impulses which are
form of electrical impulses. Electrical impulses are an excellent means of communication in human
body but they have following limitations:
1. They reach only those cells that are connected by nervous tissue, not each and every cell
in the animal body.
2. Cells cannot continually create and transmit electrical impulses. once an electrical impulse is
generated in a cell and transmitted, the cell will take some time to reset its mechanisms
before it can generate and transmit a new impulse.
Due to above said limitations most multicellular organisms use another means of communication
between cells, namely, chemical communication i.e. hormone or endocrine system. It is slower than
nerve cells but potentially reach all cells of the body.
Q20: How does chemical coordination take place in animals?
Answer: Hormones act as chemical coordinators in animals. Hormone is the chemical messenger that
regulates the physiological processes in living organisms. It is secreted by ductless glands into blood
stream and reach their target site.
Q21: Who coined the term hormone?
Answer: Bayliss and Starling. Both of discovered the peptide hormone called secretin in human
intestine.
Q22: What will happen if intake of iodine in our diet is low?
or
Q: Why is the use of iodised salt advised?
Answer: It is advised to used iodised salt to prevent goitre (enlargement of the thyroid gland). Iodine is
required for the proper functioning of thyroid. Iodine stimulates the thyroid gland to produce thyroxin
hormone. This hormone regulates carbohydrate, fat, and protein metabolism in our body.
Q23: Name the hormone secreted by an endocrine gland during emergency? Name the gland
which secretes this hormone.
Answer: Adrenaline hormone is secreted by the adrenal glands. It helps to regulate heart beat, blood
pressure, metabolism in the times of stress or emergency to cope up with the situation.
Q24: How does adrenaline affects heart during emergency?
or
Q: How does our body respond when adrenaline is secreted into the blood?
Answer: During emergency situations, adrenaline hormone is released to blood stream in large
quantities. It increases the heartbeat and hence supplies more oxygen to the muscles. The increase
in breathing rate also increases due to contractions of diaphragm and rib muscles. It raises the blood
pressure and thus enable the body to cope up with any stress or emergency.
Q25: Which hormone is injected to a diabetic patient and why?
or
Q: Why are some patients of diabetes treated by giving injections of insulin?
Answer: Diabetes is a condition in which sugar level in blood is very high. Insulin hormone is released
by pancreas glands which regulates the blood sugar level. In diabetic patients, pancreas has stopped
releasing insulin hormone. If it is not secreted in proper amounts, the sugar level in the blood rises
causing many harmful effects. Due to this reason diabetic patients are treated by giving injections of
insulin.
Q26 : How does our body maintain blood sugar level?
Answer: The timing and amount of hormone released are regulated by feedback mechanisms. When
the sugar levels in blood rise, they are detected by the cells of the pancreas which respond by
producing more insulin. As the blood sugar level falls, insulin secretion is reduced.
Q27: Where adrenal glands are located?
Answer: Adrenal glands are like caps just above the kidneys.
Q28: What is hyperglycemia?
Answer: Hyperglycemia refers to high sugar level in blood. In general diabetic patients has
hyperglycemia due to insufficient release of insulin hormone.
Q29: Where thyroid gland is located?
Answer: Thyroid gland is situated in front of the neck below larynx.
Q30: Which endocrine gland is called master gland? Why?
Answer: Pituitary gland (pea shape, present in mid-brain) is considered as master endocrine gland. It
is said so because it controls almost all other endocrine glands.
Q31: Why is pancreas a dual gland?
Answer: Pancreas is a dual gland because it acts as both endocrine and exocrine gland. As
endocrine it secretes hormones like insulin, glucagen. As an exocrine glands, it releases enzymes like
trypsin, lypase, amylase etc.