Mix Examples - Control and Coordination Questions in English

(A) The hormone injected into a diabetic patient is $Insulin$.
$(b)$ We should use iodised salt in our diet because iodine is essential for the thyroid gland to synthesize and secrete the hormone $Thyroxine$. $Thyroxine$ plays a crucial role in regulating the metabolism of carbohydrates,proteins,and fats in the body,ensuring a balanced growth and development.
$(c)$ If iodine is insufficient in one's diet,it leads to a deficiency disease known as $Goitre$. The primary symptom of $Goitre$ is a swollen neck,caused by the enlargement of the thyroid gland as it attempts to produce more $Thyroxine$ in response to low iodine levels.

(N/A) $(i)$ Voluntary actions are controlled by the cerebrum (specifically the motor cortex).
$(ii)$ Involuntary actions (such as blood pressure,salivation,and vomiting) are controlled by the medulla oblongata.
$(b)$ The peripheral nervous system $(PNS)$ facilitates communication between the central nervous system $(CNS)$ and the rest of the body.
The components of the $PNS$ are cranial nerves and spinal nerves.
Distinction in origin:
$1$. Cranial nerves arise directly from the brain.
$2$. Spinal nerves arise from the spinal cord.

(N/A) $(i)$ Iodine deficiency leads to Goitre.
$(ii)$ Insulin deficiency leads to Diabetes.
$(b)$ The timing and amount of hormone release are regulated by feedback mechanisms.
For example,if the blood sugar level rises,the cells of the pancreas detect this change and respond by secreting more insulin.
As the blood sugar level falls back to the normal range,the secretion of insulin is reduced or inhibited.
This self-regulating system ensures that hormones are secreted only in the required quantity at the appropriate time.

(N/A) $(i)$ Auxins: Promote cell elongation,root formation,and cell division. They also promote fruit growth.
$(ii)$ Gibberellins: Stimulate stem elongation,seed germination,and flowering.
$(iii)$ Cytokinins: Help in breaking the dormancy of seeds and buds. They delay ageing in leaves and promote the opening of stomata.
$(iv)$ Abscisic acid: Promotes the abscission (falling) of leaves and fruits.
$(v)$ Ethylene: Promotes the ripening of fruits.

(N/A) In humans,growth hormone is synthesized in the anterior lobe of the $Pituitary$ $gland$. In plants,growth hormones (auxins) are synthesized in the shoot tips (apical meristems).
$(b)$ The sequence of events is as follows:
$1$. When a plant is exposed to unidirectional light,the hormone $Auxin$ is synthesized at the shoot tip.
$2$. $Auxin$ diffuses towards the shaded side of the shoot,away from the light source.
$3$. The higher concentration of $Auxin$ on the shaded side stimulates the cells to elongate more rapidly compared to the cells on the illuminated side.
$4$. This differential growth causes the shoot to bend towards the light source.
$Name$ $of$ $the$ $hormone$: $Auxin$.
$Type$ $of$ $movement$: $Phototropic$ $movement$ (or $Phototropism$).

(N/A) reflex arc is the neural pathway that controls a reflex action. It is the path taken by nerve impulses in a reflex action,from the receptor to the effector.
Flow chart for sneezing:
Unwanted particles in the nostril $\to$ Receptors $\to$ Sensory neuron $\to$ Spinal cord $\to$ Motor neuron $\to$ Effectors (muscles of the respiratory system) $\to$ Sneezing.
$(b)$ Four plant hormones and their functions:
$1$. Auxins: Promote cell elongation and growth.
$2$. Gibberellins: Promote stem elongation and seed germination.
$3$. Cytokinins: Promote cell division.
$4$. Abscisic acid: Inhibits growth and promotes seed dormancy or leaf wilting.

(N/A) The structure of a neuron consists of a cell body (cyton) containing the nucleus,dendrites that receive signals,and an axon that transmits electrical impulses.
$(b)$ $(i)$ Dendrite: This part of the neuron acts as the receptor site where information from the environment or other neurons is acquired.
$(ii)$ Axon: This is the long,fiber-like extension of the neuron through which information travels in the form of an electrical impulse toward the nerve endings.

(N/A) Activity:
$(i)$ Take a potted plant and place it in a cardboard box that is open from one side. Position the box such that the open side faces a window,allowing the plant to receive light from one direction.
$(ii)$ Observe the plant for a few days. You will notice that the shoot bends towards the light source.
$(iii)$ Now,rotate the plant so that the shoot is facing away from the light. Leave it undisturbed for a few days.
$(iv)$ Observe the plant again; the shoot will gradually bend back towards the light source.
Explanation:
When growing plants detect light,a hormone called auxin,which is synthesized at the shoot tip,plays a crucial role. Auxin always diffuses towards the shady side of the shoot. This higher concentration of auxin on the shady side stimulates the cells to grow longer than those on the side facing the light. Consequently,the unequal growth causes the plant shoot to bend towards the light,a phenomenon known as phototropism.

(N/A) Sensory neuron: It carries sensory impulses from receptors,such as the skin,to the central nervous system.
$(b)$ Cranium: It is the bony case surrounding the brain,which protects it from mechanical injury and shock.
$(c)$ Vertebral column: It is the protective bony covering surrounding the spinal cord. It also provides mechanical support to the body.
$(d)$ Motor neuron: It carries motor impulses from the central nervous system to specific effectors,such as muscle fibers or gland cells.

(N/A) The timing and amount of hormone secretion are regulated by a feedback mechanism.
This mechanism ensures that hormones are released only when required and in the appropriate quantity.
Example: Regulation of blood sugar levels.
When the blood sugar level rises,the cells of the pancreas detect this change.
In response,the pancreas secretes more insulin to facilitate the uptake and oxidation of glucose by body cells,thereby lowering the blood sugar level.
Conversely,when the blood sugar level drops,the secretion of insulin is reduced to prevent hypoglycemia.

(N/A) Reflex actions are rapid,involuntary responses to stimuli. Four examples of reflex actions are:
$(i)$ Sneezing: $A$ sudden,involuntary expulsion of air from the nose and mouth.
$(ii)$ Coughing: $A$ rapid expulsion of air from the lungs to clear the airways.
$(iii)$ Knee-jerk reflex: $A$ sudden involuntary kicking movement of the lower leg in response to a sharp tap on the patellar tendon.
$(iv)$ Blinking of eyes: $A$ rapid closing and opening of the eyelids to protect the eyes from foreign objects or bright light.

(N/A) $(i)$ The brain sends messages to muscles to respond accordingly.
$(ii)$ The communication between the central nervous system and other parts of the body is facilitated by the peripheral nervous system,which consists of cranial nerves arising from the brain and spinal nerves arising from the spinal cord.
$(iii)$ The brain thus allows us to think and take actions accordingly based on that thinking.

(N/A) Involuntary actions: These are actions that occur automatically without our conscious control or choice. They are essential for maintaining the internal physiological processes of the body.
Example: The beating of the heart.
Voluntary actions: These are actions that are performed consciously and are under our control. These actions allow us to respond differently to various stimuli based on our decision.
Example: Walking or picking up a book.

(N/A) $(i)$ Receptor organs like skin receive the stimulus and activate a sensory nerve impulse that travels to the spinal cord.
$(ii)$ The neurons in the spinal cord process this information and transmit the impulse to a motor neuron.
$(iii)$ The motor nerve conducts these impulses to effector organs like muscles,which respond accordingly to the stimulus.

(N/A) When the organism confronts any stressful or scary situation,adrenaline is secreted from the adrenal gland and released directly into the blood. It is then circulated to various parts of the body,resulting in the following responses:
$(a)$ The heart beats faster to supply more oxygen to the muscles.
$(b)$ Blood supply to the digestive system and skin is reduced due to the contraction of muscles around small arteries. This diverts more blood to the skeletal muscles.
$(c)$ The breathing rate increases due to the contractions of the diaphragm and rib muscles,which allows for more oxygen intake.

(B) Plants use electrical-chemical signals to detect touch and to convey information from cell to cell,despite lacking specialized nervous tissue.
The cells in the leaves change their shape by altering the amount of water within them (turgor pressure).
This change in water content causes the cells to swell or shrink,which results in the movement of the leaves in response to the stimulus.

(N/A) The system that facilitates communication between the central nervous system and other parts of the body is the Peripheral Nervous System $(PNS)$.
It consists of two types of nerves:
$(i)$ Cranial Nerves: There are $12$ pairs of cranial nerves,which arise from the brain.
$(ii)$ Spinal Nerves: There are $31$ pairs of spinal nerves,which arise from the spinal cord.

(N/A) When growing plants detect light,a hormone called auxin,which is synthesized at the shoot tip,helps the cells to grow longer.
When light falls on one side of the plant,auxin diffuses towards the shady side of the shoot.
This higher concentration of auxin on the shady side stimulates the cells to elongate more rapidly compared to the side facing the light,causing the shoot to bend towards the light source.

(N/A)

Estrogen	Testosterone
$(i)$ It is the female sex hormone.	$(i)$ It is the male sex hormone.
$(ii)$ It is secreted by female gonads (ovaries).	$(ii)$ It is secreted by male gonads (testes).
$(iii)$ It helps in the development of female reproductive organs and also imparts female secondary sexual characteristics.	$(iii)$ It helps in the development of male reproductive organs and also imparts male secondary sexual characteristics.

(N/A) $(i)$ The forebrain is the main thinking part of the brain,consisting of specialized thinking tissues.
(ii) It contains distinct regions that receive sensory impulses from various receptors,such as the skin,eyes,ears,tongue,and nose.
(iii) It includes separate association areas where sensory information is interpreted by integrating it with data from other receptors and information already stored in the brain. Based on this analysis,a decision is made regarding the appropriate response.

(N/A) The movement of the leaves of a sensitive plant (e.g.,$Mimosa$ $pudica$) is known as a nastic movement. This movement is independent of the direction of the stimulus and occurs due to a rapid loss of water (turgor pressure) in the cells upon touch.
In contrast,the movement of a shoot towards light is a phototropic movement. This is a directional growth movement that occurs due to the unequal distribution of plant hormones,specifically auxins,in response to light.
While nastic movements are rapid and reversible,tropic movements are generally slower and involve actual growth of the plant part.

(A-D) Hormones: Hormones are chemical messengers that regulate biological processes in living organisms.
Characteristics of Hormones:
$1$. They are produced by ductless glands,meaning their secretion is released directly into the blood.
$2$. They are released in trace amounts,i.e.,in very small quantities.
$3$. They act on specific tissues or organs known as target organs.
$4$. They are generally slow in action.
$5$. They act away from the site of production.
$(b)$ $(i)$ Dwarfism
$(ii)$ Gigantism
$(iii)$ Diabetes mellitus
$(iv)$ Goitre

(N/A) Cerebrospinal fluid $(CSF)$ is a clear,colorless body fluid found in the brain and spinal cord.
It occupies the subarachnoid space and the ventricular system around and inside the brain and spinal cord.
Function: It acts as a cushion or shock absorber,protecting the brain and spinal cord from mechanical injury and sudden impacts.

(N/A) nerve impulse is an electrical signal that travels along the membrane of a neuron,facilitating the transmission of information throughout the nervous system.
$(i)$ Dendrites are the branched structures that receive signals and conduct nerve impulses towards the cell body.
$(ii)$ The axon is a long,slender projection of a nerve cell that conducts nerve impulses away from the cell body towards other neurons or effector organs.

(N/A) $(i)$ Adrenaline increases the heartbeat and breathing rate,which results in the supply of more oxygen to muscles. It reduces blood flow to the digestive system and skin; as a result,blood is diverted to skeletal muscles. All these responses together prepare the body to deal with emergency situations.
$(ii)$ If growth hormone is secreted in excess during childhood,it leads to $\text{gigantism}$,while less secretion of this hormone during childhood causes $\text{dwarfism}$.
$(iii)$ Patients suffering from diabetes have a high blood sugar level because insulin is not secreted in a sufficient amount by the pancreas to lower the blood sugar level. Therefore,to regulate the blood sugar level,insulin hormone is injected into such patients.

(A) In a neuron,electrical impulses are received by the dendrites.
From the dendrites,the impulse travels to the cell body (cyton).
Then,it moves along the axon towards the nerve endings (axon terminals).
At the synapse,the impulse is converted into a chemical signal to be transmitted to the dendrites of the next neuron.
Therefore,the correct direction is: Dendrites $\rightarrow$ Cell body $\rightarrow$ Axon $\rightarrow$ Nerve endings.

(C) Thyroxine is a hormone produced by the thyroid gland.
Iodine is essential for the synthesis of thyroxine,not iron.
Therefore,the statement that 'Iron is essential for the synthesis of thyroxine' is incorrect.
Thyroxine regulates the metabolism of carbohydrates,proteins,and fats in the body.

(D) Dwarfism is a condition characterized by abnormally short stature.
It is primarily caused by the deficiency or reduced secretion of the $Growth$ $Hormone$ $(GH)$,also known as somatotropin,during the childhood growth phase.
$GH$ is secreted by the anterior pituitary gland and is essential for the growth of bones and tissues.
Excess secretion of $GH$ leads to gigantism,while its deficiency leads to dwarfism.

(A) During puberty,the human body undergoes significant physiological and physical changes.
These changes are primarily regulated by sex hormones.
In males,the testes secrete $Testosterone$,which is responsible for the development of secondary sexual characteristics such as facial hair,deepening of the voice,and muscle growth.
In females,the ovaries secrete $Estrogen$,which is responsible for the development of secondary sexual characteristics such as breast development and the onset of the menstrual cycle.
Therefore,the correct combination is $Testosterone$ from the testes and $Estrogen$ from the ovary.

(B) Iodine is an essential mineral required by the thyroid gland to produce the hormone $Thyroxine$.
$Thyroxine$ regulates the metabolism of carbohydrates,proteins,and fats in the body.
$A$ deficiency of iodine in the diet can lead to a condition called goiter,where the thyroid gland enlarges due to its inability to synthesize sufficient $Thyroxine$.

(C) Insulin is a peptide hormone produced by the beta cells of the pancreas.
Its primary function is to regulate blood glucose levels by facilitating the uptake of glucose into cells.
When insulin secretion is insufficient,blood sugar levels rise,leading to a condition known as diabetes mellitus.
Growth and development of the body are primarily regulated by the growth hormone $(GH)$ secreted by the pituitary gland,not by insulin.
Therefore,the statement that insulin regulates the growth and development of the body is incorrect.

(D) The correct answer is $D$.
$A$. Thyroxine is secreted by the thyroid gland. This is a correctly matched pair.
$B$. Testosterone is the primary male sex hormone secreted by the testes. This is a correctly matched pair.
$C$. Estrogen is the primary female sex hormone secreted by the ovaries. This is a correctly matched pair.
$D$. Adrenaline is secreted by the adrenal glands,not the pituitary gland. The pituitary gland secretes hormones like growth hormone,$TSH$,etc. Therefore,this is the mismatched pair.

(A) The shape of guard cells is regulated by the turgor pressure within them.
When water enters the guard cells through osmosis,they become turgid and swell,causing the stomatal pore to open.
Conversely,when water leaves the guard cells,they become flaccid and shrink,causing the stomatal pore to close.
Therefore,the change in the shape of guard cells is primarily due to the amount of water present in the cells.

(B) Tendrils in pea plants exhibit thigmotropism,which is a growth response to touch.
When a tendril comes in contact with a support,the cells in contact with the support do not grow as rapidly as the cells on the side away from the support.
This differential growth rate causes the tendril to coil around the support.
Therefore,the rapid cell division occurs in the cells that are away from the support.

(C) The growth of the pollen tube towards the ovule is a classic example of $Chemotropism$.
This occurs because the ovule secretes specific chemical substances (sugars and other compounds) that attract the pollen tube.
The pollen tube senses these chemical gradients and grows towards the source,which is the ovule,to facilitate fertilization.
Therefore,the correct option is $C$.

(D) The transmission of a nerve impulse follows a specific direction: from the dendrites to the cell body and then along the axon to the axonal terminal. At the synapse,the electrical impulse triggers the release of neurotransmitters (chemicals) from the axonal end of the presynaptic neuron. These chemicals diffuse across the synaptic cleft and bind to receptors on the dendrites of the postsynaptic neuron,where they generate a new electrical impulse. Therefore,statement $D$ is incorrect because it reverses the direction of transmission,claiming that chemicals are released at the dendritic end to trigger an impulse at the axonal end.

(A) Involuntary actions,such as blood pressure,salivation,and vomiting,are controlled by the medulla oblongata.
The medulla oblongata is a part of the hindbrain.
Therefore,the correct option is $A$.

(B) An involuntary action is a movement that occurs without conscious control.
$A$,$C$,and $D$ (Vomiting,Heartbeat,and Salivation) are controlled by the medulla in the hindbrain and occur automatically.
$B$ (Chewing) is a voluntary action because it is under the conscious control of the individual,involving the skeletal muscles of the jaw.

(A) The sense of smell (olfaction) and the sense of taste (gustation) are closely linked. When a person suffers from a severe cold,the nasal passages become congested with mucus. This blockage prevents odor molecules from reaching the olfactory receptors in the nose. Since a significant portion of what we perceive as 'taste' is actually the aroma of food,the inability to smell makes it difficult to distinguish between different flavors,such as an apple and an ice cream. Therefore,the correct option is $A$.

(D) Statement $(i)$ is true: $A$ reflex action is a rapid,automatic,and involuntary response to a stimulus.
Statement $(ii)$ is false: Sensory neurons carry signals from receptors to the spinal cord,not from the spinal cord to muscles.
Statement $(iii)$ is false: Motor neurons carry signals from the spinal cord to the effectors (muscles or glands),not from receptors to the spinal cord.
Statement $(iv)$ is true: The reflex arc is the neural pathway that controls a reflex action,consisting of a receptor,sensory neuron,integration center (spinal cord),motor neuron,and effector.
Therefore,statements $(i)$ and $(iv)$ are correct.

(A) Statement $(i)$ is false because the forebrain is the main thinking part of the brain,not the hindbrain.
Statement $(ii)$ is true because the forebrain contains specialized regions for sensory processing such as hearing,smell,memory,and sight.
Statement $(iii)$ is true because the medulla oblongata,located in the hindbrain,regulates involuntary actions like salivation,vomiting,and blood pressure.
Statement $(iv)$ is false because the cerebellum is specifically responsible for maintaining posture and balance of the body.
Therefore,statements $(ii)$ and $(iii)$ are correct.

(B) The $Cerebellum$ is a part of the hindbrain responsible for maintaining the posture and balance of the body.
It also coordinates voluntary muscle movements and ensures precision and accuracy in motor activities.
$Cerebrum$ is responsible for thinking and intelligence.
$Medulla$ controls involuntary actions like blood pressure,salivation,and vomiting.
$Pons$ acts as a relay station between different parts of the brain.

(C) The spinal cord is a long, thin, tubular structure made of nervous tissue that extends from the brain.
Specifically, the spinal cord originates from the $Medulla$ $oblongata$, which is the lower part of the brainstem.
The $Medulla$ connects the brain to the spinal cord and controls vital autonomic functions such as breathing, heart rate, and blood pressure.

(D) Receptors are specialized cells or groups of cells that detect stimuli in the environment.
$1$. Gustatory receptors are specialized sensory receptors located in the taste buds of the tongue that detect taste.
$2$. Olfactory receptors are specialized sensory receptors located in the nasal cavity that detect smell.
Therefore,the statement that gustatory receptors detect taste and olfactory receptors detect smell is correct.

(A) In a neuron, the electrical impulse is initiated at the dendrites, which receive information from the environment or other neurons.
From the dendrites, the impulse travels to the cell body (cyton).
Then, it passes through the axon.
Finally, it reaches the axonal end (nerve ending), where it triggers the release of neurotransmitters to pass the signal to the next neuron or effector organ.
Therefore, the correct pathway is: $Dendrite \rightarrow Cell \ body \rightarrow Axon \rightarrow Axonal \ end$.

(B) synapse is the junction between two neurons where information is transmitted.
In this process,the electrical impulse reaching the axonal end (axon terminal) of the first neuron triggers the release of chemical messengers called neurotransmitters.
These chemicals diffuse across the synaptic cleft and bind to receptors on the dendritic end of the next neuron.
Therefore,the chemical signal is transmitted from the axonal end of one neuron to the dendritic end of another neuron.

(C) In a neuron,the electrical signal travels along the axon towards the axonal end (synaptic knob).
At the axonal end,the electrical impulse triggers the release of neurotransmitters into the synaptic cleft.
These neurotransmitters are chemical substances that carry the signal across the synapse to the next neuron.
Therefore,the conversion of an electrical signal into a chemical signal takes place at the axonal end.

(D) reflex arc is the neural pathway that controls a reflex action.
The sequence of components involved in a reflex arc is as follows:
$1$. Receptors: These detect the stimulus.
$2$. Sensory neuron: This carries the signal from the receptor to the central nervous system (spinal cord).
$3$. Spinal cord: This acts as the processing center for the reflex action.
$4$. Motor neuron: This carries the response signal from the spinal cord to the effector.
$5$. Muscles (Effectors): These perform the action in response to the stimulus.
Therefore,the correct sequence is: Receptors $\rightarrow$ Sensory neuron $\rightarrow$ Spinal cord $\rightarrow$ Motor neuron $\rightarrow$ Muscles.

(A) The endocrine system consists of several glands.
$A$. The pituitary gland is a single,unpaired gland located at the base of the brain.
$B$. Testes are a pair of male reproductive glands.
$C$. Adrenal glands are a pair of glands located on top of the kidneys.
$D$. Ovaries are a pair of female reproductive glands.
Therefore,the pituitary gland is the only unpaired gland among the given options.

(B) synapse is the specialized junction between two neurons,or between a neuron and a target cell (such as a muscle or gland cell).
At this junction,the electrical signal (action potential) is converted into a chemical signal via neurotransmitters to bridge the gap between the neurons.
Therefore,the correct term for the junction between two neurons is a synapse.