Transmission of Impulses Questions in English

(D) Synapses are the junctions between two neurons where information is transmitted.
These junctions contain synaptic vesicles in the presynaptic terminal.
These vesicles store neurotransmitters,which can be either excitatory (stimulating) or inhibitory in nature.
Since synapses store both types of chemicals to facilitate or inhibit the transmission of nerve impulses,the correct answer is $D$.

(B) The junction or functional contact between two neurons is known as a $Synapse$. At this site,the signal is transmitted from one neuron to another,either chemically or electrically.

(A) In a laboratory setting,if a nerve impulse is initiated in the middle of an isolated nerve fibre,it can travel in both directions $(bidirectional)$.
However,in the living body,nerve impulses are conducted in only one direction due to the presence of synapses.
Synapses ensure that the impulse travels from the axon terminal of one neuron to the dendrite of the next neuron,making the transmission unidirectional.

(B) synapse is the specialized junction through which a neuron signals to another neuron or to a non-neuronal cell such as a muscle or gland.
It is formed by the membranes of a pre-synaptic neuron and a post-synaptic neuron,which may or may not be separated by a gap called the synaptic cleft.

(A) synapse is the specialized junction through which a neuron (nerve cell) signals to another neuron or to a non-neuronal cell such as a muscle or gland. It is the site where the terminal end of an axon (presynaptic membrane) comes into close proximity with the dendrite or cell body of another neuron (postsynaptic membrane),allowing for the transmission of nerve impulses.

(C) The junction between two neurons is called a $Synapse$.
Within this junction, the physical gap or space between the pre-synaptic membrane and the post-synaptic membrane is specifically referred to as the $Synaptic \text{ } cleft$.
Chemical neurotransmitters are released into this $Synaptic \text{ } cleft$ to transmit the nerve impulse from one neuron to the next.

(B) The correct statement is that information across the synaptic cleft is transmitted by means of a chemical neurotransmitter stored in small vesicles.
$1$. At a chemical synapse,the membranes of the presynaptic and postsynaptic neurons are separated by a fluid-filled space called the synaptic cleft.
$2$. Chemicals called neurotransmitters are involved in the transmission of impulses at these synapses.
$3$. The axon terminals contain vesicles filled with these neurotransmitters.
$4$. When an impulse (action potential) reaches the axon terminal,it stimulates the synaptic vesicles to move towards the membrane and release the neurotransmitters into the synaptic cleft via exocytosis.
$5$. These neurotransmitters bind to specific receptors on the postsynaptic membrane,thereby opening ion channels and generating a new potential in the postsynaptic neuron.

(C) The correct answer is $C$.
Nerve impulses are transmitted across the synapse from the axon terminal to the dendrite of the next neuron with the help of chemical substances known as neurotransmitters.
$Acetylcholine$ and $Adrenaline$ (also known as $Epinephrine$) are well-known examples of neurotransmitters produced by the secretory vesicles located in the synaptic knobs of neurons.

(A) When a nerve impulse reaches the synaptic knob,it triggers the release of neurotransmitters,primarily $Acetylcholine$,into the synaptic cleft.
These neurotransmitters then bind to receptors on the postsynaptic membrane,facilitating the transmission of the impulse to the next neuron.

(D) Acetylcholinesterase is an enzyme present at the synaptic cleft.
After the transmission of a nerve impulse,the neurotransmitter acetylcholine is released into the synaptic cleft to propagate the signal.
To prevent continuous stimulation and allow the synapse to reset,the enzyme acetylcholinesterase hydrolyzes acetylcholine into choline and acetic acid.
This action terminates the signal,allowing the postsynaptic membrane to return to its resting state so it can receive another impulse.

(A) $Acetylcholine$ is the primary neurotransmitter that facilitates the transmission of nerve impulses across the synapse between two neurons.
It also plays a crucial role in the transmission of impulses at the neuromuscular junction,which is the site of communication between a motor neuron and a muscle fiber.

(A) The transmission of a nerve impulse involves rapid changes in the electrical potential across the neuronal membrane,known as an action potential.
An oscilloscope is an electronic instrument used to visualize and measure these rapid,time-varying electrical signals.
Therefore,the transmission of a nerve impulse is recorded using an oscilloscope.

(B) Acetylcholine $(ACh)$ is a well-known neurotransmitter.
It is released by the presynaptic neurons into the synaptic cleft.
It binds to the receptors on the postsynaptic membrane to transmit nerve impulses across the synapse.
Therefore, it acts as a chemical transmitter across the synapse.

(B) The conduction of nerve impulses across a chemical synapse involves the release of neurotransmitters like acetylcholine $(ACh)$.
Choline acetylase (also known as choline acetyltransferase) is the enzyme responsible for the synthesis of acetylcholine from choline and acetyl-CoA in the presynaptic terminal.
This neurotransmitter is then released into the synaptic cleft to propagate the nerve impulse to the postsynaptic neuron.
Therefore,choline acetylase is essential for the chemical transmission of nerve impulses.

(D) The transmission of a nerve impulse across a synapse is unidirectional because neurotransmitters are stored in synaptic vesicles located only at the axon terminals (presynaptic knobs).
When an action potential reaches the axon terminal,it triggers the release of these neurotransmitters into the synaptic cleft.
Dendrites possess receptors for these neurotransmitters but do not contain synaptic vesicles to release them.
Therefore,the impulse can only travel from the axon of one neuron to the dendrite or cell body of the next neuron,ensuring unidirectional flow.

(B) The transmission of a nerve impulse across a synapse is accomplished by chemical substances known as neurotransmitters.
When an action potential reaches the axon terminal (presynaptic knob),it triggers the release of neurotransmitters from synaptic vesicles into the synaptic cleft.
These neurotransmitters then bind to specific receptors on the postsynaptic membrane,initiating a new action potential in the next neuron.

(C) Parkinson's disease is a neurodegenerative disorder characterized by tremors,bradykinesia,and progressive rigidity of limbs.
It is caused by the degeneration of dopaminergic neurons in the substantia nigra region of the brain.
These neurons are responsible for movement control and utilize the neurotransmitter dopamine to transmit signals.
Therefore,the correct option is $C$.

(D) The parasympathetic nervous system is a division of the autonomic nervous system.
In the parasympathetic nervous system,the post-ganglionic nerve fibers release the neurotransmitter $Acetylcholine$ $(ACh)$.
Therefore,the correct option is $(d)$.

(C) Cobra venom contains neurotoxins,which are potent substances that specifically target the nervous system. These neurotoxins block the transmission of nerve impulses at the neuromuscular junction,leading to paralysis and,if untreated,respiratory failure.

(A) Synaptic fatigue is a temporary suspension of impulse transmission in the region of synapses.
It occurs due to the exhaustion of neurotransmitters (such as $acetylcholine$) at the synaptic knob.
When the neurotransmitter is depleted,the signal cannot be transmitted across the synaptic cleft,leading to fatigue.

(A) The venom of a cobra contains neurotoxins,specifically postsynaptic neurotoxins like alpha-neurotoxins.
These toxins bind to the acetylcholine receptors at the neuromuscular junction.
This binding prevents the transmission of nerve impulses to the muscles,leading to the inactivation of nerves and subsequent paralysis of respiratory muscles,which causes death due to respiratory failure.

(D) The correct answer is $D$.
Nerve cells that release acetylcholine at their nerve endings are known as cholinergic neurons.
Acetylcholine is a neurotransmitter that facilitates the transmission of nerve impulses across the synapse.
Once released into the synaptic cleft,it is rapidly hydrolyzed by the enzyme acetylcholinesterase,which is present in high concentrations in the synaptic fluid,to terminate the signal.

(C) Nerve gases are potent neurotoxins that act as irreversible inhibitors of the enzyme $acetylcholinesterase$.
This enzyme is responsible for breaking down the neurotransmitter $acetylcholine$ in the synaptic cleft.
By inhibiting this enzyme,nerve gas leads to the continuous accumulation of $acetylcholine$,causing overstimulation of muscles and glands,which results in paralysis,respiratory failure,and eventually death.

(C) The venom of a cobra ($Naja$ $naja$) is primarily neurotoxic in nature.
Neurotoxins are substances that damage,destroy,or impair the functioning of nerve tissue.
When a cobra bites,the venom enters the bloodstream and travels to the nervous system,where it blocks the transmission of nerve impulses to the muscles.
This leads to paralysis,particularly affecting the respiratory muscles,which can eventually cause respiratory failure and death.

(C) Most insecticides,such as organophosphates and carbamates,are designed to target the nervous system of insects. They typically act by inhibiting the enzyme acetylcholinesterase,which leads to the accumulation of the neurotransmitter acetylcholine at the synapse. This results in continuous nerve impulse transmission,causing paralysis and eventually death of the insect.

(A) Acetylcholinesterase is an enzyme that breaks down the neurotransmitter acetylcholine in the synaptic cleft.
Malathion is an organophosphate insecticide that acts as a potent inhibitor of the enzyme acetylcholinesterase.
By inhibiting this enzyme,it prevents the breakdown of acetylcholine,leading to continuous nerve stimulation,which eventually causes paralysis and death in insects.
$CO$ (carbon monoxide) binds to hemoglobin,$KCN$ (potassium cyanide) inhibits cytochrome c oxidase,and colchicine inhibits microtubule polymerization.

(B) $Synapse$ is the functional junction between the axon terminal of one neuron and the dendrite or cell body of the next neuron.
It allows the transmission of nerve impulses from one neuron to another or to an effector cell.
This transmission can be chemical (via neurotransmitters) or electrical.

(B) Acetylcholinesterase is an enzyme present in the synaptic cleft that terminates the action of the neurotransmitter acetylcholine.
It catalyzes the hydrolysis of acetylcholine into acetic acid and choline.
This process is essential for the repolarization of the postsynaptic membrane,allowing the neuron to be ready for the next signal.
Therefore,the correct products are acetic acid and choline.

(D) In the central nervous system $(CNS)$,neurotransmitters are classified as either excitatory or inhibitory based on their effect on the postsynaptic neuron.
$GABA$ (Gamma-aminobutyric acid) is the primary inhibitory neurotransmitter in the brain.
Glycine is the primary inhibitory neurotransmitter in the spinal cord and brainstem.
Norepinephrine is generally considered an excitatory neurotransmitter.
Therefore,both Glycine and $GABA$ function as inhibitory neurotransmitters in the $CNS$.

(D) The parasympathetic nervous system is a part of the autonomic nervous system.
It primarily uses the neurotransmitter $Acetylcholine$ $(ACh)$ to transmit signals to target organs.
Depending on the specific organ and receptor type,$Acetylcholine$ can have either an excitatory or inhibitory effect.
However,in the context of the parasympathetic system's general role in 'rest and digest' functions,it is known to inhibit certain activities (like heart rate) while stimulating others (like digestion).
Among the given options,$Acetylcholine$ is the correct neurotransmitter,and it is widely recognized for its inhibitory role in cardiac muscle and excitatory role in smooth muscle of the digestive tract.

(B) The transmission of nerve impulses across a synapse is mediated by chemical messengers known as neurotransmitters.
When an action potential reaches the presynaptic terminal,it triggers the release of neurotransmitters into the synaptic cleft.
$Acetylcholine$ is a well-known neurotransmitter that binds to receptors on the postsynaptic membrane,facilitating the propagation of the nerve impulse to the next neuron.

(A) Synaptic vesicles are small,membrane-bound sacs found within the axon terminals of the presynaptic neuron. These vesicles contain neurotransmitters,which are chemical substances released into the synaptic cleft to transmit nerve impulses to the postsynaptic neuron. Therefore,they are specifically located in the presynaptic neuron.

(A) $GABA$ (Gamma-aminobutyric acid) is the primary inhibitory neurotransmitter in the mammalian central nervous system.
It functions by reducing the excitability of neurons,thereby playing a crucial role in regulating neuronal communication and preventing over-excitation.

(A) The transmission of a nerve impulse across a synapse follows a specific sequence of events:
$1$. First,the action potential reaches the axon terminal $(d)$.
$2$. This arrival causes the synaptic vesicles to fuse with the pre-synaptic membrane,releasing neurotransmitters into the synaptic cleft $(c)$.
$3$. These neurotransmitter molecules then diffuse across the synaptic cleft and bind to specific receptors on the post-synaptic membrane $(b)$.
$4$. This binding triggers the opening of ion channels,allowing ions to enter and generate a new action potential in the post-synaptic neuron $(a)$.
Therefore,the correct sequence is $d \rightarrow c \rightarrow b \rightarrow a$.

(B) synapse is formed by the membranes of a presynaptic neuron and a postsynaptic neuron,which may or may not be separated by a gap called the synaptic cleft.
In electrical synapses,the membranes of pre- and post-synaptic neurons are in very close proximity,and electrical current can flow directly from one neuron into the other across these synapses.
Impulse transmission across an electrical synapse is very similar to impulse conduction along a single axon.
Therefore,the statement that synaptic membranes are 'always' separated by a synaptic cleft is incorrect,as electrical synapses do not necessarily have a synaptic cleft.

(B) The transmission of a nerve impulse across a synapse is not instantaneous. It involves the release of neurotransmitters from the presynaptic neuron,their diffusion across the synaptic cleft,and the binding to receptors on the postsynaptic membrane. This process takes a small amount of time,typically $0.3$ to $0.5 \text{ ms}$,which is known as the $Synaptic \ delay$.

(B) Acetylcholine $(ACh)$ is a well-known neurotransmitter in the nervous system.
Its primary function is to facilitate the transmission of nerve impulses across the synapse between two neurons or between a neuron and a muscle cell (neuromuscular junction).
When an action potential reaches the synaptic knob,$ACh$ is released into the synaptic cleft,where it binds to receptors on the postsynaptic membrane to propagate the signal.
Therefore,it is essential for synaptic transmission.

(C) In a neuron,the synapse is the junction between two neurons. The pre-synaptic neuron is the one that sends the signal,and the post-synaptic neuron is the one that receives it. The axon terminal,also known as the telodendria,contains synaptic vesicles filled with neurotransmitters. Therefore,the telodendria acts as the pre-synaptic part of the neuron.

(B) The parasympathetic nervous system is a division of the autonomic nervous system that helps maintain homeostasis and promotes 'rest and digest' activities.
In the parasympathetic nervous system,the neurotransmitter released at both the preganglionic and postganglionic nerve endings is $Acetylcholine$ $(ACh)$.
In contrast,the sympathetic nervous system typically releases $Norepinephrine$ at the postganglionic nerve endings.
Therefore,the correct option is $B$.

(C) Parkinson's disease is a progressive neurodegenerative disorder.
It is primarily caused by the loss of dopaminergic neurons in the $substantia$ $nigra$ region of the midbrain.
These neurons are responsible for the production and release of the neurotransmitter $Dopamine$, which plays a crucial role in the regulation of movement and coordination.
A deficiency of $Dopamine$ leads to the characteristic symptoms of Parkinson's disease, such as tremors, muscle rigidity, and bradykinesia (slowness of movement).

(C) $GABA$ (Gamma-Aminobutyric Acid) is the primary inhibitory neurotransmitter in the central nervous system.
When $GABA$ is released into the synaptic cleft,it binds to specific $GABA$ receptors on the postsynaptic membrane.
This binding typically opens chloride $(Cl^-)$ channels,allowing $Cl^-$ ions to flow into the postsynaptic neuron.
The influx of negatively charged $Cl^-$ ions makes the membrane potential more negative than the resting membrane potential,a process known as hyperpolarization.
Hyperpolarization makes the neuron less likely to fire an action potential,thereby inhibiting neural transmission.

(A) The unidirectional transmission of nerve impulses is primarily due to the presence of a $Synapse$.
At a chemical synapse,neurotransmitters are released only from the presynaptic membrane of the axon terminal into the synaptic cleft.
These neurotransmitters then bind to specific receptors located only on the postsynaptic membrane of the dendrite or cell body.
Because receptors are absent on the presynaptic side and neurotransmitter vesicles are absent on the postsynaptic side,the impulse can only travel in one direction.

(D) The synaptic delay is the time required for a nerve impulse to cross a synapse.
This delay occurs due to the time taken for the release of neurotransmitters from the presynaptic membrane,their diffusion across the synaptic cleft,and their binding to the receptors on the postsynaptic membrane.
In most chemical synapses,this process typically takes approximately $0.3 \, ms$ to $0.5 \, ms$.
Among the given options,$0.5 \, ms$ is the standard value often cited in physiological studies for the duration of synaptic transmission delay.

(A) Nerve impulses are transmitted across a synapse with the help of chemical substances known as neurotransmitters.
In the human nervous system,the most common neurotransmitters involved in synaptic transmission are Acetylcholine and Noradrenaline (also known as Norepinephrine).
While Adrenaline and Noradrenaline are catecholamines,Acetylcholine is a distinct ester neurotransmitter.
Since the question asks for the substances involved in transmission,and considering standard textbook options,the most accurate representation of neurotransmitters involved in synaptic transmission is Acetylcholine and Noradrenaline.
However,looking at the provided options,option $A$ mentions Sympathin (an older term for Noradrenaline).
Therefore,the correct answer is $A$.

(A) The functional junction between two neurons,or between a neuron and an effector cell (like a muscle or gland),is known as a $Synapse$.
At a $Synapse$,the nerve impulse is transmitted from one neuron to another,either through chemical neurotransmitters (chemical synapse) or through direct electrical flow (electrical synapse).
$Synapsis$ refers to the pairing of homologous chromosomes during meiosis,while $Chiasmata$ are the points of crossing over between non-sister chromatids.

(A) The junction between the axon terminal of one neuron and the dendrite of another neuron is called a $Synapse$.
It is the site where nerve impulses are transmitted from one neuron to another,either chemically or electrically.

(B) $Synapse$ is the functional junction between two neurons. It is formed by the membranes of a pre-synaptic neuron and a post-synaptic neuron,which may or may not be separated by a gap called the synaptic cleft. Through this junction,nerve impulses are transmitted from one neuron to another.

(A) The neurotransmitter $GABA$ (Gamma-Aminobutyric Acid) is the primary inhibitory neurotransmitter in the central nervous system of mammals.
It functions by binding to specific receptors on the postsynaptic membrane,which leads to the opening of chloride channels,resulting in hyperpolarization of the neuron and inhibition of nerve impulse transmission.
In contrast,Adrenaline,Epinephrine,and Acetylcholine generally act as excitatory neurotransmitters in most physiological contexts.

(B) $Acetylcholinesterase$ is an enzyme present in the synaptic cleft.
It catalyzes the hydrolysis of the neurotransmitter $Acetylcholine$ into $Choline$ and $Acetic$ $acid$.
This process terminates the signal transmission at the neuromuscular junction and synapses,allowing the postsynaptic membrane to reset for the next impulse.

(B) In electrical synapses,the membranes of pre- and post-synaptic neurons are in very close proximity ($i$ is correct).
Electrical current can flow directly from one neuron into the other across these synapses ($ii$ is correct).
Impulse transmission across an electrical synapse is very similar to impulse conduction along a single axon ($iii$ is correct).
Electrical synapses do not use neurotransmitters; they rely on direct ionic flow through gap junctions ($iv$ is incorrect).
Electrical synapse transmission is very fast,often faster than chemical synapses ($v$ is correct).
Electrical synapses are indeed rare in our system compared to chemical synapses ($vi$ is correct).
Therefore,statements $i, ii, iii, v,$ and $vi$ are correct.