Animals - Nervous System 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.

(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.

(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.

(A) 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.

(B) In a neuron,the electrical impulse is received by the dendrites.
From the dendrites,the impulse travels to the cell body (cyton).
Then,it moves along the axon to the axonal end (nerve ending).
Therefore,the correct sequence is: Dendrite $\to$ cell body $\to$ axon $\to$ axonal end.

(C) synapse is the junction between two neurons.
In a synapse,the chemical signal (neurotransmitter) is released from the axonal end (axon terminal) of the presynaptic neuron.
These neurotransmitters diffuse across the synaptic cleft and bind to the receptors present on the dendritic end (dendrites) of the postsynaptic neuron.
Therefore,the transmission occurs from the axonal end of one neuron to the dendritic end of another neuron.

(D) In a neuron,the electrical signal (nerve impulse) travels along the axon to the axon terminal (axonal end).
At the axonal end,the electrical signal triggers the release of chemical messengers known as neurotransmitters into the synaptic cleft.
This process effectively converts the electrical signal into a chemical signal,which then diffuses across the synapse to the next neuron or target cell.
Therefore,the conversion occurs at the axonal end.

(A) reflex arc is the pathway taken by nerve impulses in a reflex action.
$1$. The process begins when receptors detect a stimulus.
$2$. The sensory neuron carries the signal from the receptor to the spinal cord (central nervous system).
$3$. Within the spinal cord,the signal is processed,often involving an interneuron.
$4$. The motor neuron then carries the response signal from the spinal cord to the effector organ (muscle or gland).
$5$. Finally,the muscle contracts or the gland secretes,resulting in the reflex action.
Therefore,the correct sequence is: Receptors $\to$ Sensory neuron $\to$ Spinal cord $\to$ Motor neuron $\to$ Muscle.

(B) Statement $(i)$ is true: $A$ reflex action is an automatic, rapid, and involuntary response to a stimulus.
Statement $(ii)$ is false: Sensory neurons carry signals from receptors to the central nervous system (spinal cord/brain), not from the spinal cord to muscles.
Statement $(iii)$ is false: Motor neurons carry signals from the central nervous system to effectors (muscles or glands), not from receptors to the spinal cord.
Statement $(iv)$ is true: The pathway taken by nerve impulses in a reflex action is known as a reflex arc, connecting the receptor to the effector.
Therefore, statements $(i)$ and $(iv)$ are correct.

(C) Statement $(i)$ is false because the forebrain is the main thinking part of the brain.
Statement $(ii)$ is true because the forebrain (cerebrum) contains specialized regions for sensory processing like hearing,smell,memory,and sight.
Statement $(iii)$ is true because the medulla oblongata,located in the hindbrain,controls involuntary actions such as salivation,vomiting,and blood pressure.
Statement $(iv)$ is false because the cerebellum is specifically responsible for maintaining the posture and balance of the body.
Therefore,statements $(ii)$ and $(iii)$ are correct.

(D) 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.
Therefore, the correct option is $D$.

(A) 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 autonomic functions such as breathing,heart rate,and blood pressure.
Therefore,the correct option is $A$.

(A) The correct answer is $A$.
In a neuron,the nerve impulse travels from the dendritic end towards the axonal end.
At the axonal end (synaptic knob),the electrical impulse triggers the release of neurotransmitters (chemicals) into the synapse.
These chemicals diffuse across the synapse and bind to receptors on the dendrite of the next neuron,where they generate a new electrical impulse.
Option $A$ is incorrect because it states that the electrical impulse at the dendritic end releases chemicals to generate an impulse at the axonal end of another neuron,which reverses the actual direction of signal transmission.

(B) 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 $B$.

(C) Involuntary actions are those that occur without conscious control,such as heart beat,salivation,and vomiting. These are controlled by the medulla in the hindbrain.
Chewing (mastication) is a voluntary action because it is controlled by our conscious will and involves the skeletal muscles of the jaw.

(D) synapse is the specialized junction between two neurons,or between a neuron and a target cell (such as a muscle or gland cell),where information is transmitted from one cell to another.
At the synapse,the plasma membranes of the neurons are separated by a narrow space called the synaptic cleft.
Neurotransmitters are released from the presynaptic neuron into the synaptic cleft to transmit the signal to the postsynaptic neuron.

(N/A) The given figure represents a reflex arc,which is the pathway taken by nerve impulses in a reflex action.
$(a)$ Sensory neuron: It carries the electrical signal from the receptor (skin) to the central nervous system.
$(b)$ Spinal cord: It acts as the processing center for the reflex action.
$(c)$ Motor neuron: It carries the response signal from the spinal cord to the effector.
$(d)$ Effector: It is the muscle in the arm that contracts to pull the hand away from the hot object.
The direction of the flow of electrical signals is from the receptor (hand) $\rightarrow$ sensory neuron $(a)$ $\rightarrow$ spinal cord $(b)$ $\rightarrow$ motor neuron $(c)$ $\rightarrow$ effector $(d)$ (muscle).

(N/A) Dendrite: These are branch-like structures that receive information from other neurons.
$(b)$ Cell body (Cyton): It contains the nucleus and cytoplasm and is responsible for processing information.
$(c)$ Axon: It is a long fiber that conducts electrical impulses away from the cell body.
$(d)$ Nerve ending (Axon terminal): These are the branched ends of the axon that transmit signals to the next neuron or target cell.

(A) The correct matches are as follows:
$(a)$ Olfactory receptors are sensory receptors for smell,located in the $(iii)$ Nose.
$(b)$ Thermoreceptors are sensory receptors for temperature,located in the $(iv)$ Skin.
$(c)$ Gustatoreceptors are sensory receptors for taste,located in the $(i)$ Tongue.
$(d)$ Photoreceptors are sensory receptors for light,located in the $(ii)$ Eye.
Therefore,the correct sequence is: $(a-iii, b-iv, c-i, d-ii)$.

(C) At the synapse,the electrical impulse reaching the axon terminal of one neuron triggers the release of neurotransmitters (chemical substances).
These chemical substances cross the synaptic cleft and bind to receptors on the dendrite of the next neuron.
This process converts the chemical signal back into an electrical impulse in the next neuron,allowing the signal to propagate through the nervous system.

(N/A) neuron (nerve cell) is the structural and functional unit of the nervous system. Its structure consists of three main parts:
$1$. Cell Body (Cyton): It contains the nucleus and cytoplasm (Nissl granules). It is responsible for the metabolic activities of the cell.
$2$. Dendrites: These are short,branched extensions that receive electrical impulses from other neurons or sensory receptors and transmit them towards the cell body.
$3$. Axon: This is a long,single fiber that carries electrical impulses away from the cell body to other neurons,muscles,or glands. It is often covered by a myelin sheath for faster signal transmission.
Function: Neurons are specialized to detect,receive,and conduct nerve impulses (electrical signals) throughout the body,enabling communication between different parts of the body and the brain.

(N/A) The human brain is divided into three major parts:
$1$. Forebrain: It is the main thinking part of the brain. It controls voluntary actions,stores information (memory),and processes sensory information like sight,smell,and hearing.
$2$. Midbrain: It connects the forebrain to the hindbrain and controls reflex movements of the head,neck,and eyes in response to visual and auditory stimuli.
$3$. Hindbrain: It consists of the cerebellum,pons,and medulla. The cerebellum controls posture,balance,and precision of voluntary movements. The medulla controls involuntary actions like blood pressure,salivation,and vomiting.

(N/A) The central nervous system $(CNS)$ is composed of the brain and the spinal cord.
The peripheral nervous system $(PNS)$ consists of all the nerves that branch out from the $CNS$ and connect to the rest of the body,including cranial nerves and spinal nerves.
The components of the $CNS$ are protected as follows:
$1$. The brain is protected by a bony box called the cranium (brain box),which contains cerebrospinal fluid for shock absorption.
$2$. The spinal cord is protected by the vertebral column (backbone).

(N/A) Reflex actions are rapid,automatic,and involuntary responses to a stimulus that do not involve conscious thought by the brain.
Examples:
$1$. Sudden withdrawal of the hand upon touching a hot object.
$2$. Blinking of eyes when a bright light or object suddenly approaches them.
Reflex Arc:
$A$ reflex arc is the neural pathway that mediates a reflex action. The pathway consists of the following components:
$1$. Receptor: Detects the stimulus.
$2$. Sensory Neuron: Carries the signal from the receptor to the spinal cord.
$3$. Relay Neuron (Interneuron): Processes the signal within the spinal cord.
$4$. Motor Neuron: Carries the response signal from the spinal cord to the effector.
$5$. Effector: $A$ muscle or gland that performs the action.

(D) When an electrical impulse reaches the axonal end (synaptic knob) of a neuron,it triggers the release of chemical substances known as neurotransmitters into the synaptic cleft.
These chemicals diffuse across the synapse towards the dendritic end of the adjacent neuron.
At the dendritic end,these chemicals bind to specific receptors to generate a new electrical impulse.
Since the neurotransmitters are stored only in the synaptic vesicles at the axonal end and the receptors are located only on the dendritic membrane,the signal can only flow in one direction: from the axon of one neuron to the dendrite of another.

(N/A) The two specialised tissues that provide control and coordination in multicellular organisms are:
$1$. Nervous tissue: It is responsible for the transmission of electrical impulses and the processing of information.
$2$. Muscular tissue: It is responsible for the movement of body parts in response to the signals received from the nervous system.

(N/A) The cerebellum is responsible for maintaining posture,balance,and the coordination of voluntary muscle movements.
$(i)$ Walking in a straight line: The cerebellum coordinates the precise muscle movements required to maintain balance while walking.
$(ii)$ Picking up an object from the ground: This requires precise coordination between the eyes and the hands,as well as maintaining body balance while bending,which is controlled by the cerebellum.

(N/A) The motor areas of the brain are responsible for the conscious control and coordination of voluntary muscle movements. These regions receive information from other parts of the brain and send signals through the spinal cord to the skeletal muscles,enabling precise actions such as walking,writing,and speaking.

(N/A) $(i)$ The region responsible for sight is the Occipital lobe (located in the cerebrum of the forebrain).
$(ii)$ The region which controls salivation is the Medulla oblongata (located in the hindbrain).

(N/A) The specialised tips of some nerve cells that detect information from the environment are called $Receptors$.
These $Receptors$ are located in our sense organs,such as the inner ear,the nose,the tongue,the skin,and the eyes.

(N/A) $(i)$ Gustatory receptors are specialized sensory receptors located in the taste buds of the tongue that function to detect taste.
$(ii)$ Olfactory receptors are specialized sensory receptors located in the nasal cavity that function to detect smell.

(B) The reflex arc is a neural pathway that controls a reflex action. In most cases,the sensory neurons transmit the signal to the spinal cord,which processes the information and sends an immediate response through motor neurons to the effector organ. This process bypasses the brain to ensure a rapid reaction to stimuli,making the spinal cord the primary control center for reflex arcs.

(A) The $Peripheral \ Nervous \ System$ $(PNS)$ facilitates communication between the $Central \ Nervous \ System$ $(CNS)$ and other parts of the body. However, in the context of general biological coordination, the $Endocrine \ System$ also plays a crucial role in chemical communication. Given the options provided, the $Endocrine \ System$ is the intended answer for chemical signaling, while the $Peripheral \ Nervous \ System$ is the primary structural link.

(N/A) The two tissues (or systems) that provide control and coordination in multicellular animals are:
$(i)$ Nervous tissue: It consists of neurons that transmit electrical impulses to coordinate body activities rapidly.
$(ii)$ Endocrine tissue (or Glandular tissue): It consists of endocrine glands that secrete hormones directly into the blood to regulate physiological processes slowly and steadily.

(B) synapse is the functional junction between two neurons,or between a neuron and an effector cell (like a muscle or gland),where information is transmitted from one cell to another.

(N/A) Reflex action is a sudden,involuntary,and spontaneous response to a stimulus. It is usually helpful in protecting the body from potential harm or injury by bypassing the conscious thought process of the brain.

(N/A) The sensory receptors found in the nose are called olfactory receptors,which detect smell.
The sensory receptors found on the tongue are called gustatory receptors,which detect taste.

(N/A) neuron is the functional and structural unit of the nervous system,which consists of cells specialized for conducting information via electrical impulses from one part of the body to another.
$(i)$ Information is acquired at the dendrites.
$(ii)$ The impulse is converted into a chemical signal at the axon terminals (end of the axon) to facilitate transmission across the synapse.

(N/A) When a bright light is focused on the eyes,the following sequence of events occurs in the reflex arc:
$1$. Photo receptors (in the retina of the eye) detect the stimulus (bright light).
$2$. Sensory neurons transmit the nerve impulse from the eye to the central nervous system (spinal cord/brain).
$3$. The relay neuron (interneuron) in the central nervous system processes the signal.
$4$. Motor neurons transmit the response signal from the central nervous system to the effector muscles.
$5$. The effector muscles (eyelid muscles) contract,causing the eye to blink.
Sequence: $\text{Photo receptors} \to \text{Sensory neuron} \to \text{Central nervous system} \to \text{Motor neuron} \to \text{Effector (eyelid muscles)} \to \text{Response (blinking)}$.

(A) $(i)$ The information is acquired at the end of the dendrite tip of a nerve cell.
$(ii)$ The information travels as an electrical impulse from the dendrite to the cell body and then along the axon to its end.

(N/A) $(i)$ Cerebellum is responsible for the precision of voluntary actions.
$(ii)$ It maintains the posture and balance of the body.
$(b)$ The components of the central nervous system are:
$(i)$ Brain
$(ii)$ Spinal cord

(N/A) The brain is protected by a bony box called the cranium (skull),which provides a hard outer covering. Inside the skull,the brain is cushioned by a fluid-filled balloon known as the cerebrospinal fluid $(CSF)$,which absorbs mechanical shocks and protects the brain from injury.
The spinal cord is protected by the vertebral column (backbone),which provides structural support and shields it from physical damage.
Additionally,both the brain and the spinal cord are covered by three protective membranes known as the meninges,which provide further insulation and protection.

(N/A) and $(b)$ Refer to the provided diagram of the human brain.
$(c)$ Role of the Cerebellum: It is responsible for the precision of voluntary actions and for maintaining the posture and balance of the body.