Textbook - Control and Coordination Questions in English

(B) reflex action is a rapid,automatic,and involuntary response to a stimulus that does not involve conscious thinking. It is controlled by the spinal cord. For example,withdrawing a hand upon touching a hot object.
Walking,on the other hand,is a voluntary action. It is under our conscious control and involves the brain (cerebrum) for planning and execution.

(N/A) synapse is a microscopic gap between the axon terminal of one neuron and the dendrite of the next neuron.
It functions as a one-way valve,ensuring that nerve impulses travel in only one direction.
This unidirectional transmission occurs because chemical messengers (neurotransmitters) are stored only in the axon terminals of the presynaptic neuron.
When an electrical impulse reaches the axon terminal,these chemicals are released into the synaptic cleft.
They diffuse across the gap and bind to specific receptors on the dendrite of the postsynaptic neuron,where they trigger a new electrical impulse.

(B) The $Cerebellum$, which is a part of the $Hindbrain$, is responsible for maintaining the posture, balance, and equilibrium of the body. It also coordinates voluntary muscular movements.

(B) The thinking part of our brain is the forebrain.
It has separate areas that are specialized for hearing,smelling,sight,taste,touch,etc.
The forebrain also has regions that collect information or impulses from the various receptors.
When the smell of an incense stick reaches us,our forebrain detects it.
Then,the forebrain interprets it by putting it together with the information received from other receptors and also with the information already stored in the brain.

(N/A) Reflex actions are sudden,involuntary responses to stimuli that do not involve conscious thinking.
For example,when we touch a hot object,we withdraw our hand immediately without thinking,as the time taken for conscious processing could cause severe burns.
The sensory nerves that detect the heat are connected to the motor nerves that move the muscles of the hand.
Such a connection of detecting the signal from the nerves (input) and responding to it quickly (output) is called a reflex arc.
The reflex arcs—connections present between the input and output nerves—meet in a bundle in the spinal cord.
Reflex arcs are formed in the spinal cord,and the information (input) simultaneously reaches the brain.
The brain is only made aware of the signal and the response that has taken place.
However,the brain plays no role in the initiation or creation of the reflex response itself.

(N/A) Plant hormones,also known as phytohormones,are naturally occurring organic substances. They are synthesized in minute quantities in specific parts of the plant body and are translocated to other parts where they are required to regulate physiological processes. The five major types of phytohormones are auxins,gibberellins,cytokinins,abscisic acid,and ethylene.

(B) The movement of leaves of the sensitive plant,$Mimosa$ $pudica$ (touch-me-not),occurs in response to touch or contact stimuli (thigmonasty). This movement is independent of growth and is reversible.
The movement of a shoot towards light is known as phototropism. This type of movement is directional and is growth-dependent,meaning it involves the differential growth of cells on different sides of the stem.

(A) Auxin is a primary example of a growth-promoting plant hormone. It is responsible for cell elongation,apical dominance,and root initiation in plants.

(B) Auxin is a plant hormone synthesized at the shoot tip that promotes cell elongation.
When a tendril comes in contact with a support,the concentration of auxin decreases on the side touching the support and remains higher on the side away from the support.
This higher concentration of auxin on the side away from the support stimulates faster cell growth and elongation on that side.
As a result,the side away from the support grows longer than the side in contact,causing the tendril to coil around the support.

(N/A) $1$. Take two small beakers and label them as $A$ and $B$.
$2$. Fill beaker $A$ with water and leave beaker $B$ empty.
$3$. Make a cylindrical-shaped roll from a filter paper and place it as a bridge between beaker $A$ and beaker $B$.
$4$. Place a few germinating seeds in the middle of the filter paper bridge.
$5$. Cover the entire set-up with a transparent plastic container to maintain humidity.
Observation:
After a few days,it is observed that the roots of the germinating seeds grow towards beaker $A$ (the source of water).
Conclusion:
This growth of plant roots towards water is known as hydrotropism. It demonstrates that roots are positively hydrotropic.

(N/A) Chemical coordination in animals is mediated by hormones.
Hormones are chemical messengers that regulate various physiological processes in living organisms.
These substances are secreted by endocrine glands directly into the bloodstream.
The regulation of physiological processes,as well as control and coordination via hormones,is collectively known as the endocrine system.
In animals,the nervous system works in conjunction with the endocrine system to effectively control and coordinate complex physiological activities.

(B) Iodine is essential for the thyroid gland to produce the hormone thyroxin.
Thyroxin regulates the metabolism of carbohydrates,fats,and proteins in the body.
$A$ deficiency of iodine leads to a deficiency of thyroxin,which causes the thyroid gland to enlarge,a condition known as goitre.
Therefore,the use of iodised salt is advised to ensure the normal functioning of the thyroid gland and to prevent goitre.

(B) Adrenaline is a hormone secreted by the adrenal glands in response to danger,emergency,or stress.
It is secreted directly into the blood and transported to various target organs.
When secreted in large amounts,it increases the heartbeat to supply more oxygen to the muscles.
The breathing rate also increases due to the contraction of the diaphragm and rib muscles.
Additionally,it increases blood pressure and diverts blood flow to essential organs.
All these physiological responses prepare the body to deal with stressful or emergency situations.

(N/A) Diabetes is a metabolic disorder characterized by high blood sugar levels (hyperglycemia).
Insulin is a hormone produced by the $\beta$-cells of the pancreas that facilitates the uptake of glucose into cells,thereby lowering blood sugar levels.
In patients with diabetes,the pancreas either does not produce enough insulin or the body cannot effectively use the insulin it produces.
Therefore,external injections of insulin are administered to maintain blood glucose levels within the normal physiological range.

(C) Cytokinin is a plant hormone that promotes cell division in plants.
Insulin,Thyroxin,and Estrogen are hormones found in animals.

(D) The gap between two neurons is called a synapse. It is the site where the terminal end of the axon of one neuron comes in close proximity to the dendrite of another neuron,allowing for the transmission of nerve impulses via chemical neurotransmitters.

(A) The brain is the main coordinating centre of the body.
It is responsible for complex processes like thinking,processing information,and memory.
It also controls involuntary actions such as regulating the heart beat through the medulla oblongata.
Furthermore,it is responsible for maintaining the posture and balancing the body,a function primarily performed by the cerebellum.
Therefore,all the given options are correct.

(N/A) Receptors are specialized sensory structures (organs,tissues,or cells) present throughout the body. They are either grouped together,as in the case of the eye or ear,or scattered,as in the case of the skin.
Functions of receptors:
$(i)$ They detect external stimuli such as heat,light,sound,or pain.
$(ii)$ They trigger an electrical impulse in the sensory neurons,which transmits the information to the central nervous system (spinal cord or brain).
Problems when receptors do not work properly:
If receptors are damaged,the body fails to perceive external stimuli. For example,if the heat receptors in the skin are damaged,a person might accidentally touch a hot object and suffer severe burns because the brain does not receive the warning signal of pain or heat. This lack of sensory feedback can lead to serious injuries or accidents.

(N/A) Neurons are the functional units of the nervous system. The three main parts of a neuron are the axon,dendrite,and cell body.
Functions of the three parts of a neuron:
$1$. Dendrite: It receives information from the axon of another cell and conducts the messages towards the cell body.
$2$. Cell body: It contains the nucleus,mitochondria,and other organelles. It is mainly concerned with the maintenance and growth of the cell.
$3$. Axon: It conducts messages away from the cell body towards the nerve endings.

(N/A) Phototropism is the directional growth of a plant in response to light.
$1$. When plants are exposed to light coming from one side,a plant hormone called $Auxin$ is synthesized at the shoot tip.
$2$. $Auxin$ helps the cells grow longer.
$3$. When light falls on the shoot from one side,$Auxin$ diffuses towards the shady side of the shoot.
$4$. This concentration of $Auxin$ stimulates the cells on the shady side to grow longer than those on the side receiving light.
$5$. As a result,the plant appears to bend towards the source of light.

(C) The reflex arc connections between the input and output nerves meet in a bundle in the spinal cord.
In fact,nerves from all over the body meet in a bundle in the spinal cord on their way to the brain.
In case of any injury to the spinal cord,the signals coming from the nerves as well as the signals coming to the receptors will be disrupted.

(N/A) In animals,control and coordination occur with the help of the nervous system. However,plants do not have a nervous system.
Plants respond to stimuli by showing movements. The growth,development,and responses to the environment in plants are controlled and coordinated by a special class of chemical substances known as hormones or phytohormones.
These hormones are produced in one part of the plant body and are translocated to other parts where they are required.
For example,a hormone produced in the roots is translocated to other parts when needed.
The five major types of phytohormones are auxins,gibberellins,cytokinins,abscisic acid,and ethylene.
These phytohormones are either growth promoters (such as auxins,gibberellins,cytokinins,and ethylene) or growth inhibitors (such as abscisic acid).

(N/A) The maintenance of body functions in response to changes in the environment by the integrated working of various body systems is known as coordination.
All movements that occur in response to stimuli are carefully coordinated and controlled.
In animals,control and coordination are provided by the nervous and muscular systems.
The nervous system sends messages to and from the brain,while the spinal cord plays a crucial role in relaying these signals.
Without a system of control and coordination,the body would not be able to function as a unified whole.
For example,when we accidentally touch a hot object,we immediately withdraw our hand due to a reflex action.
In the absence of this system,we would not perceive the danger or react,leading to severe injury or burns.

(N/A) Involuntary actions are those that cannot be consciously controlled,such as the movement of food in the alimentary canal or the beating of the heart. These actions are directly regulated by the brain.
Reflex actions are sudden,automatic,and involuntary responses to a stimulus that do not involve conscious thought or processing by the brain. For example,closing eyes immediately when exposed to bright light. Unlike involuntary actions,reflex actions are primarily controlled by the spinal cord,allowing for a faster response.

(N/A)

Nervous system mechanism	Hormonal system mechanism
$1.$ Information is conveyed as electrical impulses.	$1.$ Information is conveyed as chemical messengers (hormones).
$2.$ Information is transmitted through neurons (axons and dendrites).	$2.$ Information is transported through the blood.
$3.$ The flow of information is rapid,and the response is quick.	$3.$ The flow of information is slow,and the response is gradual.
$4.$ The effects are short-lived.	$4.$ The effects are prolonged and sustained.

(N/A)

Movement in sensitive plants	Movement in our legs
$1$. The movement that takes place in a sensitive plant such as $Mimosa \text{ } pudica$ occurs in response to touch (stimulus).	$1$. Movement in our legs is an example of voluntary actions.
$2$. For this movement, the information is transmitted from cell to cell by electrochemical signals as plants do not have any specialised tissue for conduction of impulses.	$2$. The signals or messages for these actions are passed to the brain and hence are consciously controlled.
$3$. For this movement to occur, the plant cells change shape by changing the amount of water in them.	$3$. In animal muscle cells, specialized proteins are found which allow the movement to occur upon contraction.