← Back to Chapter
Exam Focus:
Nervous system, neuron, reflex action, reflex arc, brain,
spinal cord, plant movements, tropisms, plant hormones,
endocrine glands and animal hormones.
A. Very Short Answer Questions
Question 1
What is coordination?
Coordination is the process by which different organs and
systems work together to produce an appropriate response
to a stimulus or change.
Question 2
What is a stimulus?
A stimulus is a detectable change in the internal or
external environment that can produce a response.
Question 3
What is a neuron?
A neuron is a specialised cell that receives and transmits
nerve impulses.
Question 4
What is a reflex action?
A reflex action is a rapid, automatic and usually involuntary
response to a stimulus.
Question 5
What is a hormone?
A hormone is a chemical messenger secreted by endocrine
tissue and transported to target sites where it produces
a response.
B. Nervous System & Neuron
Question 6
Name the main parts of a neuron.
The main parts are:
-
Cell body
-
Dendrites
-
Axon
-
Nerve endings
Question 7
What is the usual direction of an impulse through a neuron?
Dendrite → Cell Body → Axon → Nerve Ending
Question 8
What is a synapse?
A synapse is the junction between two neurons or between
a neuron and another cell, across which the signal is
transmitted.
Question 9
Why are nerve impulses transmitted rapidly?
Neurons are specialised cells designed to conduct electrical
impulses efficiently, allowing rapid communication between
different parts of the body.
C. Reflex Action
Question 10
What is a reflex arc?
A reflex arc is the pathway followed by nerve impulses during
a reflex response.
Receptor → Sensory Neuron → Spinal Cord
→ Motor Neuron → Effector
Question 11
Why are reflex actions important?
Reflex actions provide rapid responses that can protect the
body from potentially harmful situations.
Question 12
Why can the spinal cord coordinate many reflex actions?
The spinal cord contains neural pathways that can rapidly
connect sensory input to motor output without waiting for
the complete conscious processing of the stimulus by the brain.
D. Human Brain
Question 13
Name the three broad regions of the human brain discussed
in this chapter.
Forebrain, midbrain and hindbrain.
Question 14
What are the main functions of the forebrain?
It is involved in thinking, interpreting sensory information,
learning, memory and voluntary actions.
Question 15
What is the function of the cerebellum?
The cerebellum helps coordinate movement, posture and balance.
Question 16
Which part of the brain controls many involuntary activities?
The medulla in the hindbrain controls several involuntary
activities such as breathing and heartbeat.
Question 17
Why is the brain protected by the skull?
The skull provides mechanical protection to the delicate
brain tissue.
E. Spinal Cord & Coordination
Question 18
What are the functions of the spinal cord?
The spinal cord carries information between the brain and
body and also participates in many reflex actions.
Question 19
Differentiate between voluntary and involuntary actions.
Voluntary actions:
Actions performed under conscious control.
Involuntary actions:
Actions that occur automatically without conscious control.
F. Coordination in Plants
Question 20
How do plants coordinate their responses without a nervous
system?
Plants coordinate responses through chemical signals,
changes in growth and movements of plant parts.
Question 21
What is phototropism?
Phototropism is directional growth of a plant part in
response to light.
Question 22
What is geotropism or gravitropism?
It is directional growth of a plant part in response to
gravity.
Question 23
What is hydrotropism?
Hydrotropism is directional growth of a plant part in
response to water or moisture.
Question 24
What is chemotropism?
Chemotropism is directional growth in response to a chemical
stimulus, such as pollen tube growth towards the ovule.
Question 25
What happens when the leaves of Mimosa pudica are touched?
The leaves fold or droop rapidly in response to touch. This
is a nastic movement rather than a directional growth
response.
G. Plant Hormones
Question 26
What is auxin?
Auxin is a plant hormone that promotes growth, particularly
cell elongation, and plays an important role in phototropic
responses.
Question 27
What is the role of gibberellins?
Gibberellins promote plant growth and are associated with
processes such as stem elongation and seed germination.
Question 28
What is the main role of cytokinins?
Cytokinins promote cell division and influence plant growth
and development.
Question 29
What is the role of abscisic acid?
Abscisic acid generally inhibits growth and is involved in
plant responses to environmental stress, including helping
regulate stomatal closure.
Question 30
Which plant hormone is commonly associated with fruit ripening?
Ethylene.
H. Hormonal Coordination in Animals
Question 31
What is endocrine coordination?
Endocrine coordination is control and communication through
hormones released by endocrine glands and transported to
target tissues.
Question 32
Why are hormones called chemical messengers?
Hormones carry chemical signals from their source gland or
tissue to target cells where they regulate specific functions.
Question 33
Which gland secretes thyroxine?
The thyroid gland secretes thyroxine.
Question 34
Why is iodine important for thyroid function?
Iodine is needed to make thyroid hormones such as thyroxine.
Severe iodine deficiency can interfere with normal thyroid
function.
Question 35
Which hormone is associated with the fight-or-flight response?
Adrenaline.
Question 36
What is the role of insulin?
Insulin helps regulate blood glucose concentration by
promoting uptake and storage of glucose in appropriate tissues.
I. Reproductive Hormones
Question 37
What is the role of testosterone?
Testosterone contributes to development of male reproductive
organs and secondary sexual characteristics.
Question 38
What is the role of oestrogen?
Oestrogen contributes to development of female reproductive
organs and secondary sexual characteristics and participates
in regulation of the reproductive cycle.
J. Reasoning-Based Questions
Question 39
Why is reflex action generally faster than a conscious response?
Reflex pathways can use relatively short neural circuits
through the spinal cord, allowing a rapid protective response
before complete conscious processing by the brain.
Question 40
Why does a plant shoot bend towards light?
Unequal distribution of auxin causes greater cell elongation
on the shaded side of the shoot, resulting in bending towards
the light.
Question 41
Why does the human body need both nervous and hormonal
coordination?
Nervous coordination provides rapid and usually targeted
responses, while hormonal coordination can regulate processes
over a longer period and across wider parts of the body.
Question 42
Why can hormonal effects continue for longer than many
nervous responses?
Hormones circulate through the blood and may act on target
tissues for longer periods, whereas many nervous signals
are rapid and short-lived.
K. Competency-Based Practice
Question 43
A person accidentally touches a very hot object and
immediately withdraws the hand. Explain the pathway involved.
The heat stimulus is detected by receptors.
The sensory neuron carries the impulse to the spinal cord.
A motor neuron then carries the instruction to the muscles,
causing the hand to withdraw.
This is a reflex action.
Question 44
A plant placed near a window bends towards the light.
Identify the response and explain it.
It is positive phototropism. Unequal auxin distribution
causes differential growth of the shoot, so it bends toward
the light.
Question 45
A person faces a sudden frightening situation and experiences
an increase in heart rate and breathing rate. Which hormone
is involved and why?
Adrenaline is involved. It prepares the body for rapid action
by increasing heart rate and breathing rate and directing
resources towards immediate physical activity.
Question 46
A child has a severe deficiency of a hormone responsible for
normal growth. Which endocrine gland is likely to be involved?
The pituitary gland is likely to be involved because it
secretes growth hormone, which contributes to normal growth
and development.
Question 47
A student has a problem maintaining normal blood glucose
concentration. Which hormone should be considered and which
organ produces it?
Insulin should be considered. It is produced by the pancreas
and plays a key role in regulating blood glucose levels.
L. Long Answer Questions
Question 48
Explain the structure and working of a neuron.
A neuron consists mainly of dendrites, a cell body, an axon
and nerve endings.
Dendrites receive signals. The cell body integrates the
information and the impulse travels along the axon to the
nerve ending, which communicates the signal to the next cell.
Question 49
Explain reflex action and reflex arc.
Reflex action is a rapid automatic response to a stimulus.
The pathway involved is called a reflex arc:
Receptor → Sensory Neuron → Spinal Cord
→ Motor Neuron → Effector
This arrangement allows a quick protective response.
Question 50
Explain how plants coordinate their responses.
Plants use chemical signals and changes in growth or cell
behaviour rather than a nervous system.
Directional growth responses include phototropism,
geotropism, hydrotropism and chemotropism. Plant hormones
such as auxin, gibberellins, cytokinins, abscisic acid and
ethylene regulate many growth and developmental responses.
Question 51
Compare nervous and hormonal coordination.
Nervous coordination mainly uses electrical impulses and
neurotransmitters and generally produces rapid responses.
Hormonal coordination uses chemical hormones transported
through the blood and generally produces slower but often
longer-lasting effects.
M. Quick Revision Questions
-
Define stimulus, response and coordination.
-
Draw and explain a neuron.
-
Explain reflex action and reflex arc.
-
Write the functions of major brain regions.
-
What is phototropism?
-
Explain the role of auxin in phototropism.
-
Differentiate between tropic and nastic movements.
-
Name important plant hormones and their functions.
-
Name important animal hormones and their sources.
-
Differentiate between nervous and hormonal coordination.