Lesson: Control and Coordination
Which of the following is a plant
hormone?
(a) Insulin
(b) Thyroxin
(c) Oestrogen
(d) Cytokinin
(d)
The gap between two neurons is called a
(a) Dendrite
(b) Synapse
(c) Axon
(d) Impulse
(b)
The brain is responsible for
(a) Thinking
(b) Regulating the heartbeat
(c) Balancing the body
(d) All of the above
(d)
What is the function of receptors in
our body? Think of situations where receptors do not work properly. What
problems are likely to arise?
Functions
of receptor in our body:
·
They
sense external stimuli such as heat or pain and pass on the information to the
brain. The brain, in turn, instructs related organ to take necessary action.
·
They
also trigger an impulse in the sensory neuron which sends message to the spinal
cord.
When
receptors do not function properly, the brain does not get signals regarding
external stimuli. This may lead to accident or bodily damage. For example, if
we accidentally touch any hot object, then our hands might get burnt as
non-functional receptors cannot perceive external stimuli of heat and pain.
Draw the structure of a neuron and
explain its function.
Neurons are also known as nerve cells. They are the
structural and functional units of our nervous system. A neuron is the largest
cell in a body that carries messages across large distances in a body. The
messages are in the form of electrical signals called electrical impulses or
nerve impulses.
The structure of a neuron is shown below:
The components of a neuron are:
·
Dendrites: Dendrites are tree-like extensions which
receive information from a body part or other neurons and transmit electric
signals to a cell body.
·
Cell body: Cell body (also known as soma) is the place
where all the dendrites are joined. It produces all necessary proteins for
other parts of a neuron.
·
Nucleus: Nucleus is the most important organelle
which contains genes that consist of DNA.
·
Axon hillock: Axon hillock is part of a cell
body that receives signals from all dendrites and creates the electric impulse
which travels down the axon.
·
Axon: Axon is a long tube which carries electric
signals away from a cell body towards the terminal button and transmits them to
other neurons.
·
Myelin sheath: Myelin sheath is made up of
proteins and fats and is responsible for protection and insulation of neurons.
·
Synaptic terminals: Synaptic
terminals are terminal buttons that are located at the end of a neuron and are
responsible for sending signals on to other neurons
·
Synapse: Synapse is a small gap at the end of
a neuron that allows information to pass from one neuron to the next
muscle or gland.
How does phototropism occur in plants?
Growth movement in plants in response to light
stimulus is called phototropism. In plants, shoots bend towards a source of
light and roots bend away from the light source. Therefore, shoots show
positive phototropism whereas roots show negative phototropism.
Which signals will get disrupted in
case of a spinal cord injury?
The
nerves from all over the body meet in a bundle inside the spinal cord. In case
of spinal cord injury, there will be total shutdown of signal transmission from
rest of the body to the brain. Therefore,
messages from the brain too will not be conducted to any organ.
How does chemical coordination occur in
plants?
Chemical coordination occurs in plants through
plant hormones. Different plant hormones help to coordinate growth, development
and responses to the environment.
Examples:
·
Auxin
promotes cell growth.
·
Gibberellin
promotes stem growth.
·
Cytokinins
promote cell division.
·
Abscisic
acid inhibits growth, wilting and shedding of leaves etc.
·
Ethylene helps fruits ripen by making them softer and sweeter.
What is the need for a system of
control and coordination in an organism?
There are various organs in an organism. For
survival of an organism, these organs must work together in a proper manner. In
human beings, the nervous system and the endocrine system work together for
control and coordination. Hormones are responsible for overall growth and
development of an organism, and the central nervous system is responsible for
daily decision that includes voluntary and involuntary actions.
How are involuntary actions and reflex
actions different from each other?
Involuntary actions: These actions are
part of routine activities. They happen in involuntary organs. They are
directly under the control of brain.
Reflex actions: These actions are in
response to a sudden danger or action and happen in voluntary organs. They are
not under the control of brain.
Compare and contrast nervous and
hormonal mechanisms for control and coordination in animals.
Nervous System Mechanism:
·
It is fast
·
It is facilitated by neuro transmitters
·
The information is transmitted in the form of electric impulses
Hormone System Mechanism:
·
It is slow
·
It facilitates hormonal control
·
The information is transmitted in the form of chemical messengers
What is the difference between the
manner in which movement takes place in a sensitive plant and the movement in
our legs?
The movement in a sensitive plant is
facilitated by chemical control and the movement in our legs is facilitated by nervous
control.