Nervous System

A nerve impulse is also known as an action potential. It is a brief electrical signal that travels along the axon of a neuron, and it is caused by a change in the membrane potential of the neuron. This change in membrane potential, which is known as depolarization, occurs when sodium ions rush into the cell, making the inside more positive. This depolarization then triggers the opening of voltage-gated potassium channels, allowing potassium ions to flow out of the cell, which returns the membrane potential to its resting state. The action potential travels down the axon to the synapse, where it triggers the release of neurotransmitters, which carry the signal to the next neuron or effector cell.

The human nervous system is responsible for transmitting signals between different parts of the body and the brain. It comprises two main parts: the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS includes the brain and the spinal cord, while the PNS consists of all the nerves that connect the CNS to the rest of the body.
Option A is the correct answer because it includes both the CNS and the PNS, which are the two main components of the human nervous system. The CNS is responsible for processing and coordinating information, while the PNS is responsible for transmitting information between the CNS and the rest of the body.
Option B is incorrect because it only includes the CNS and the somatic nervous system, which is responsible for voluntary movement and sensory information. It does not include the PNS, which is responsible for involuntary functions such as digestion and breathing.
Option C is incorrect because it includes the sympathetic and parasympathetic nervous systems, which are part of the autonomic nervous system. The autonomic nervous system is responsible for regulating involuntary functions such as heart rate and blood pressure, but it is not one of the two main components of the human nervous system.
Option D is incorrect because it includes the autonomic and somatic nervous systems, but it does not include the central nervous system. The somatic nervous system is responsible for voluntary movement and sensory information, while the autonomic nervous system is responsible for regulating involuntary functions.
In conclusion, the correct answer is option A, which includes both the central nervous system and the peripheral nervous system. The CNS and the PNS work together to ensure the proper functioning of the human body.

The autonomic nervous system (ANS) is a division of the peripheral nervous system that regulates the involuntary functions of the body, such as heart rate, breathing, digestion, and temperature control. It is responsible for maintaining the internal environment of the body, which is essential for survival.
Option C is the correct answer because it accurately describes the function of the ANS. The ANS controls the internal environment of the body by regulating the activity of organs and glands, which is necessary for maintaining homeostasis. For example, the sympathetic division of the ANS increases heart rate and blood pressure in response to stress, while the parasympathetic division decreases heart rate and promotes digestion.
Option A is incorrect because the ANS does not enable us to act on the external environment. It is responsible for involuntary functions that occur within the body, rather than voluntary movements that involve interaction with the external environment.
Option B is incorrect because the ANS does not transmit motor information to the brain. Rather, it transmits sensory information from the internal organs to the brain, which allows the brain to monitor and regulate the activity of the ANS.
Option D is incorrect because the ANS is not located within the brain. Rather, it is located outside the brain and spinal cord, and it consists of two main divisions: the sympathetic and parasympathetic nervous systems.
In conclusion, the correct answer is option C, which accurately describes the function of the autonomic nervous system. The ANS plays a crucial role in regulating the internal environment of the body and maintaining homeostasis.

The three main anatomical neural planes are sagittal, coronal, and horizontal. These planes are used in neuroscience to visualize and study the structure and function of the brain.
Option D is the correct answer because it accurately describes the three main anatomical neural planes. The sagittal plane divides the brain into left and right halves, the coronal plane divides the brain into front and back sections, and the horizontal plane divides the brain into top and bottom sections.
Option A is incorrect because the term "cerebral" does not accurately describe a neural plane. The cerebral cortex is the outer layer of the brain and is involved in higher cognitive functions, but it is not a plane of anatomical reference.
Option B is incorrect because ventral and dorsal are terms that describe the location of structures in relation to the spinal cord. These terms are not used to describe anatomical planes.
Option C is incorrect because anterior and posterior are terms that describe the location of structures in relation to the front and back of the body. These terms are not used to describe anatomical planes.
In conclusion, the correct answer is option D, which accurately describes the three main anatomical neural planes. These planes are essential for visualizing and studying the structure and function of the brain.

The corpus callosum is a neural pathway that connects the right and left hemispheres of the brain. It is the largest white matter structure in the brain and is responsible for the communication between the two hemispheres.
Option B is the correct answer because it accurately describes the corpus callosum. The corpus callosum is made up of millions of axons that transmit information between the two hemispheres of the brain, allowing for integration and coordination of cognitive and motor functions.
Option A is incorrect because the hypothalamus is a region of the brain that produces and regulates hormones, but it is not related to the corpus callosum.
Option C is incorrect because the neocortex is the outer layer of the brain that is responsible for higher cognitive functions such as perception, movement, and consciousness. The corpus callosum is located deeper in the brain and is not part of the neocortex.
Option D is incorrect because the cerebellum is a separate region of the brain that is responsible for coordination and balance. It is not related to the corpus callosum.
In conclusion, the correct answer is option B, which accurately describes the corpus callosum as a neural pathway that connects the right and left hemispheres of the brain.

During the fourth week after conception, the neural tube develops into three primary vesicles: the prosencephalon, mesencephalon, and rhombencephalon. These primary vesicles will further divide and develop into different structures of the brain.
The prosencephalon will divide into the telencephalon and diencephalon, while the rhombencephalon will divide into the myelencephalon and metencephalon. The mesencephalon will not further divide, but will develop into the midbrain.
Option D is the correct answer because it accurately describes the three primary vesicles that develop in the neural tube during the fourth week after conception. The prosencephalon will eventually develop into the forebrain, the mesencephalon will become the midbrain, and the rhombencephalon will become the hindbrain.
Option A is incorrect because the myelencephalon and metencephalon are part of the rhombencephalon, which is one of the primary vesicles that develop from the neural tube. The telencephalon and diencephalon are part of the prosencephalon.
Option B is incorrect because the metencephalon is part of the rhombencephalon, not the prosencephalon.
Option C is incorrect because the cerebral cortex, limbic system and basal ganglia are structures that develop from the telencephalon, which is one of the secondary vesicles that form from the prosencephalon.
In conclusion, the correct answer is option D, which accurately describes the three primary vesicles that develop in the neural tube during the fourth week after conception. These vesicles will eventually develop into different structures of the forebrain, midbrain and hindbrain.

The term "anterior" refers to the front end of an animal. In rats, the nose is located at the front end of the body, making it the anterior part of the rat. The term "ventral" refers to the belly or underside of an animal, "caudal" refers to the tail end of an animal, and "posterior" refers to the rear end of an animal. Therefore, option B is the correct answer.

The autonomic nervous system is a branch of the peripheral nervous system, which regulates and controls the involuntary functions of the body such as heart rate, digestion, and respiratory rate. The peripheral nervous system comprises the nerves and ganglia outside of the brain and spinal cord, including the somatic nervous system which controls voluntary movements and sensations, and the autonomic nervous system which controls involuntary functions. The autonomic nervous system can be further divided into the sympathetic and parasympathetic divisions, which have opposing effects on many organs and tissues in the body. Therefore, the correct answer is option B, the peripheral nervous system.

The tectum, also known as the roof of the midbrain, is a region of the brainstem that is involved in sensory processing. It is composed of two main structures, the superior colliculus and the inferior colliculus. The superior colliculus is responsible for processing visual information and plays an important role in orienting the eyes and head towards visual stimuli. The inferior colliculus, on the other hand, is involved in processing auditory information. Therefore, option A, the superior colliculus, is the correct answer. The periaqueductal grey, substantia nigra, and red nucleus are not part of the tectum, but rather are located in other areas of the midbrain and are involved in various functions such as pain modulation, motor control, and reward processing.

Afferent nerves, also known as sensory nerves, are responsible for carrying sensory information from various parts of the body towards the central nervous system, including the brain and spinal cord. The sensory information can come from different senses such as touch, smell, taste, sight, and hearing. Once the sensory information is received by the central nervous system, it is processed and integrated to generate a response, which is then transmitted via efferent nerves to the appropriate muscles or organs. Therefore, option A is the correct answer, as it correctly states the direction of the transmission of sensory information by afferent nerves.

The basal ganglia are a group of subcortical nuclei that play a crucial role in motor control and reward learning. The basal ganglia comprise several structures, including the caudate nucleus, the putamen, and the globus pallidus. These structures are involved in regulating voluntary movements, including starting, stopping, and adjusting movement patterns. The caudate nucleus and putamen, together known as the striatum, receive input from different areas of the cerebral cortex and transmit signals to the globus pallidus, which in turn sends output to the thalamus and brainstem to regulate movement. Dysfunction of the basal ganglia can lead to motor disorders such as Parkinson's disease, Huntington's disease, and dystonia.

The cerebral cortex is the outermost layer of the brain and covers the cerebral hemispheres, which are the two largest and most prominent structures in the brain. It is responsible for many important functions, such as consciousness, perception, memory, thought, language, and voluntary movement. The cerebral cortex is divided into four main lobes: the frontal lobe, parietal lobe, temporal lobe, and occipital lobe. Each lobe has its unique functions and plays a vital role in the overall functioning of the brain. Therefore, option D is the correct answer.

The telencephalon is one of the five major divisions of the brain and it refers to the cerebral hemispheres. These hemispheres make up the largest part of the brain and are responsible for a variety of functions, including sensory and motor processing, memory, emotion, and consciousness. The telencephalon is the most recently evolved part of the brain and is unique to mammals. It is divided into several lobes, including the frontal, parietal, temporal, and occipital lobes, each with its own specialized functions. Overall, the telencephalon plays a critical role in human behavior, cognition, and intelligence.

The somatic nervous system is a division of the peripheral nervous system that controls voluntary movements and senses such as touch, temperature, and pain. It is responsible for transmitting sensory and motor information between the central nervous system and the body's muscles and sensory receptors. The autonomic nervous system, on the other hand, regulates involuntary functions such as heart rate, digestion, and respiration. The central nervous system comprises the brain and spinal cord, and it processes and coordinates all incoming and outgoing information. Finally, the parasympathetic nervous system is one of the two divisions of the autonomic nervous system that conserves energy and promotes restful functions.

The inferior and superior colliculi are structures located in the midbrain that form the tectum, a region involved in processing auditory and visual information. The superior colliculus is primarily responsible for visual processing, while the inferior colliculus is involved in auditory processing. Together, these structures play a critical role in orienting the body towards sensory stimuli and initiating appropriate motor responses.

The thalamus is a large mass of gray matter located in the brain that plays a crucial role in relaying sensory and motor signals to the cerebral cortex. Most sensory nuclei of the thalamus send their projections to the cortex. The cortex is responsible for the processing of sensory information, such as touch, vision, and hearing. The thalamus acts as a relay center for sensory information, sending it to the appropriate part of the cortex for processing. In addition to sensory information, the thalamus also processes motor information and sends it to the motor cortex for execution of movement. Thus, the thalamus plays a crucial role in the integration of sensory and motor information in the brain.

Cerebrospinal fluid (CSF) is a clear and colorless liquid that circulates throughout the brain and spinal cord. It is essential for the proper functioning of the central nervous system. One of the primary functions of CSF is to provide mechanical protection to the brain by cushioning it against impacts or sudden movements. CSF also helps in the exchange of nutrients and metabolic waste products between the brain and the circulatory system. In addition, CSF helps carry neuroactive hormones and substances, but it does not directly improve the conduction of nerve signals between different brain regions.

The parasympathetic nervous system generally acts to conserve energy by promoting rest and digestion. It is responsible for activities such as decreasing heart rate, constricting pupils, increasing digestive secretions, and promoting bladder emptying. In contrast, the sympathetic nervous system, which is responsible for the body's fight or flight response, acts to expend energy by increasing heart rate, dilating pupils, decreasing digestive secretions, and promoting bladder retention. Therefore, option D is the correct answer.

Broca's area is a region in the dominant hemisphere of the brain, typically located in the left frontal lobe. It is responsible for language production, including speech and writing. Damage to this area can result in a condition known as Broca's aphasia, where the individual has difficulty producing language but can still understand it. Therefore, the correct option is A) Frontal lobe.

The primary auditory cortex is located in the temporal lobe of the brain. It is responsible for processing auditory information and plays a crucial role in speech perception, sound localization, and the discrimination of different types of sounds. The auditory cortex receives information from the ears via the thalamus and processes this information to allow us to make sense of the sounds in our environment. Damage to the primary auditory cortex can result in various auditory processing disorders such as difficulty understanding speech, sound localization problems, and tinnitus.

Magnetic Resonance Imaging (MRI) is a technique used to obtain detailed images of the brain and other parts of the body. MRI uses strong magnetic fields and radio waves to produce images of the body's internal structures. In the case of the brain, MRI can show the structure of the brain and identify areas of damage or abnormalities. Other techniques, such as EEG, fMRI, and PET, can provide information about brain function, but MRI is specifically used to visualize the structure of the brain. MRI is a non-invasive and relatively safe procedure, but it can be expensive and time-consuming.

A neuron is a specialized cell that transmits information in the nervous system. It consists of three primary structures: the cell body, the axon, and the dendrites. The cell body contains the nucleus and other organelles necessary for the neuron's function. The axon is a long, slender structure that conducts electrical impulses away from the cell body, while dendrites are shorter and more branched structures that receive signals from other neurons. The glomerulus, on the other hand, is not a part of a neuron but a part of the nephron in the kidney. Therefore, the correct answer is D) Glomerulus.

Nissl's granules are specialized structures found in the cell body of neurons. They are clusters of ribosomes, which are responsible for synthesizing the proteins required for the normal functioning of the neuron. The cell body also contains other organelles, such as mitochondria and Golgi apparatus, which are involved in cellular metabolism and protein trafficking. The dendrites and axons of neurons are primarily involved in receiving and transmitting signals, respectively, and do not contain Nissl's granules. The presence of Nissl's granules in the cell body helps to distinguish neurons from other types of cells in the nervous system.

Dendrites are short fibers that project out from the cell body of a neuron and help in the transmission of impulses. They are characterized by their branching structure and may contain Nissl’s granules, which are clusters of rough endoplasmic reticulum. However, they do not project out from the axon, which is a long fiber that carries electrical impulses away from the cell body. The axon and dendrites are both part of the neuron's structure, but they serve different functions. While dendrites receive signals from other neurons and transmit them towards the cell body, the axon carries signals away from the cell body towards other neurons or target cells.

The branched ends of axons are called synaptic knobs, which are the points of contact between the axon of one neuron and the dendrites or cell body of another neuron. The synaptic knobs contain small sacs called synaptic vesicles that release neurotransmitters, which then travel across the synaptic cleft and bind to receptors on the postsynaptic membrane, transmitting signals between neurons. Dendrons, on the other hand, are not related to axons, but are short fibers that branch out from the cell body and receive information from other neurons. Synaptic vesicles are present within the synaptic knobs and contain neurotransmitters, which are released when an action potential reaches the terminal end of the axon. The release of these neurotransmitters triggers a response in the postsynaptic neuron, leading to the transmission of information between neurons.

Neurotransmitters are the chemical messengers that are released by the neuron to communicate with the target cell or another neuron. These neurotransmitters are stored in small, bubble-like structures called synaptic vesicles. When an action potential reaches the synaptic knob, these vesicles fuse with the presynaptic membrane and release the neurotransmitters into the synaptic cleft, which then bind to the receptors on the postsynaptic membrane, transmitting the signal to the next cell. The neurotransmitters are then either taken back into the presynaptic neuron for reuse or are broken down by enzymes in the synaptic cleft.

Axons are long fibers that transmit nerve impulses away from the cell body towards synapses. Their terminal ends are branched and end with synaptic knobs, which are responsible for transmitting the impulse to the next neuron. Therefore, option C is incorrect as axons are not short fibers.

Neurons are specialized cells that transmit and process information in the nervous system. They are classified into three types based on the number of axon and dendrites they possess. Multipolar neurons have one axon and multiple dendrites. Unipolar neurons have a single process extending from the cell body that bifurcates into two branches, one acting as an axon and the other as a dendrite. Bipolar neurons have a single dendrite and a single axon. Thus, the correct answer is option A.

Bipolar neurons are a type of nerve cells that contain one axon and one dendrite. They are found in the retina of the eye, where they help in the transmission of visual information. On the other hand, the cerebral cortex and autonomic ganglia are composed of multipolar neurons, while unipolar neurons are present in embryos.

Nissl’s granules are present in both non-myelinated and myelinated neurons. These granules are clusters of rough endoplasmic reticulum (ER) and free ribosomes in the cell body of the neuron. They play an important role in protein synthesis, which is essential for the survival and function of the neuron. On the other hand, myelin forming Schwan cells are only present in myelinated neurons, where they wrap around axons to form the myelin sheath. Nodes of Ranvier are only present in myelinated neurons and are the points between two adjacent myelin sheaths where the axon is exposed.

At resting membrane potential, the axonal membrane of a neuron is selectively permeable, meaning it allows certain ions to pass through while preventing others from doing so. The main ion that can pass through the membrane at resting potential is potassium ions (K+). Sodium ions (Na+) are unable to cross the membrane at this time, as the sodium channels are closed. Calcium ions (Ca2+) and chloride ions (Cl-) also cannot pass through the membrane at resting potential. This selective permeability is due to the presence of ion channels, which are proteins that span the membrane and create a pathway for ions to travel through.
Potassium ions are able to move freely through the membrane because there is a higher concentration of K+ inside the cell compared to outside. This concentration gradient creates a driving force that pushes K+ out of the cell, and the only thing preventing it from leaving is the negative charge on the inside of the cell membrane. This negative charge is created by the presence of negatively charged molecules such as proteins and nucleic acids inside the cell.
In summary, at resting membrane potential, the axonal membrane of a neuron is permeable to potassium ions, but relatively impermeable to sodium, calcium, and chloride ions.

At resting membrane potential, the axonal membrane of a neuron is selectively permeable, meaning it allows certain ions to pass through while preventing others from doing so. The main ion that cannot pass through the membrane at resting potential is sodium ions (Na+), as the sodium channels are closed. Potassium ions (K+) are able to move freely through the membrane because there is a higher concentration of K+ inside the cell compared to outside, creating a driving force that pushes K+ out of the cell. Calcium ions (Ca2+) and chloride ions (Cl-) also cannot pass through the membrane at resting potential.
Because sodium ions are unable to cross the membrane at resting potential, their concentration remains higher outside the cell compared to inside. This concentration gradient creates a driving force that pushes Na+ into the cell if the channels were open. This gradient is maintained by the sodium-potassium pump, a protein that actively transports Na+ out of the cell and K+ into the cell, using ATP as energy. This pump plays a critical role in maintaining the resting membrane potential of the neuron.
In summary, at resting membrane potential, the concentration of sodium ions is higher outside the axonal membrane of a neuron compared to inside, due to the selective permeability of the membrane.

Neurons are classified into three major types based on the number of axons and dendrites they possess. These three types are:

1. Multipolar neurons: These neurons have one axon and two or more dendrites arising from the cell body. They are the most common type of neuron and are found in the brain and spinal cord.
2. Bipolar neurons: These neurons have one axon and one dendrite arising from the cell body. They are found in specialized sensory organs such as the retina of the eye and the olfactory epithelium in the nose.
3. Unipolar neurons: These neurons have a single process that emerges from the cell body and divides into two branches. One branch functions as an axon, and the other branch functions as a dendrite. They are found in the sensory ganglia of the peripheral nervous system.

The myelin sheath is formed around the axon of a nerve fibre by Schwann cells. These cells wrap themselves around the axon multiple times, creating the myelin sheath. This sheath provides insulation to the axon and speeds up the process of nerve impulse transmission. The gaps between adjacent myelin sheaths are called Nodes of Ranvier. Schwann cells are found in the peripheral nervous system and are also responsible for the regeneration of damaged nerve fibres.

Myelinated nerve fibers are primarily found in spinal cord and cranial nerves. These neurons are surrounded by Schwann cells that form a myelin sheath around the axon, which helps in the faster conduction of electrical signals. Unmyelinated nerve fibers, on the other hand, are found in peripheral nerves, somatic and autonomous neural systems. Myelination of neurons is a crucial process in the development and function of the nervous system.

The junction that transmits impulses from one neuron to another is called a synapse. It is formed by the membranes of pre-synaptic and post-synaptic neurons. Synapses are the gaps between two neurons where chemical or electrical signals are transmitted to communicate with each other.

Electrical synapses are rare in the nervous system and are found only in specific regions like cardiac and smooth muscle tissue. At electrical synapses, the pre- and post-synaptic membranes are in close proximity, and the transmission of signals is faster than chemical synapses. Electrical synapses allow the direct flow of ions and molecules from one neuron to another.

The synaptic cleft is the fluid-filled space that separates the membranes of the pre- and post-synaptic neurons at chemical synapses. The transmission of impulses at these synapses involves the release of neurotransmitters from the pre-synaptic neuron into the synaptic cleft, which then bind to receptors on the post-synaptic neuron to initiate a response. Gap junctions, on the other hand, are found at electrical synapses and allow for direct communication between the cytoplasm of adjacent cells. Synapse is a general term used to describe the junction between two neurons or a neuron and a target cell. Synaptic vesicles are small membranous sacs found in the pre-synaptic neuron that contain neurotransmitters.

Chemical synapses are characterized by the slow transmission of impulse in one direction only. These synapses are commonly found in the neural system and involve the release of neurotransmitters. However, multidirectional impulse transmission is not a feature of chemical synapses.

The receptors of neurotransmitters are located on the post-synaptic membrane in the neural system. Once the neurotransmitters are released, they bind to their specific receptors on the post-synaptic membrane. This results in the development of new potentials that may either be excitatory or inhibitory. The neurotransmitter-receptor binding at the post-synaptic membrane is a key mechanism for signal transmission in the nervous system. The binding is specific to the neurotransmitter and receptor type, and the strength of the signal depends on the amount of neurotransmitter released and the affinity of the receptor.

The brain is the central processing organ of the human body, responsible for receiving, integrating and processing information from different parts of the body. It controls and coordinates all voluntary and involuntary actions of the body, making it the command and control center of the body. The brain is involved in various functions such as memory, thought, emotion, perception, and behavior, and it is protected by the skull. The brain is composed of several specialized regions that perform different functions, making it one of the most complex and fascinating organs in the human body.

The brain is responsible for various important functions such as thermoregulation, controlling circadian rhythms, voluntary movements, and regulating the functioning of vital involuntary organs. However, generating the heartbeat is not a function of the brain. The heart has its own electrical system that regulates its contractions, independent of the brain's control.

The cranial meninges are the three layers of protective membranes that surround the brain and spinal cord. The three layers of the cranial meninges are the dura mater, arachnoid, and pia mater. The dura mater is the outermost layer, followed by the arachnoid and then the innermost layer, pia mater. The corpus callosum is not a part of the cranial meninges. It is a bundle of nerve fibers that connects the two hemispheres of the brain and allows for communication between them. Therefore, option D is the correct answer.

The forebrain is the anterior part of the brain and consists of cerebrum, thalamus, and hypothalamus. The cerebellum, located in the posterior part of the brain, is not a part of the forebrain. The cerebrum is responsible for conscious thought, voluntary actions, and processing of sensory information. The thalamus is a relay center for sensory information, and the hypothalamus controls the endocrine system and regulates various physiological processes like temperature, hunger, and thirst.

The cerebrum forms a major part of the human brain. It is divided into two halves, left and right cerebral hemispheres, which are connected by the corpus callosum. The cerebrum is responsible for a variety of functions, including conscious thought, sensory perception, voluntary motor control, and language. It is also involved in memory, emotion, and learning. The cerebral cortex is the outer layer of the cerebrum and is responsible for the complex processes of perception, thought, and action.

At resting membrane potential, the axonal membrane of a neuron is nearly impermeable to sodium ions. However, the membrane is permeable to potassium ions. The resting membrane potential is the electrical potential difference between the inner and outer surfaces of the axonal membrane when the neuron is not transmitting any signals. This potential difference is maintained by the selective permeability of the axonal membrane to different ions, which is controlled by ion channels and ion pumps. The resting membrane potential is important for the normal functioning of neurons, and any disturbance in this potential can lead to neuronal disorders.

When a stimulus is applied to a polarized axonal membrane, there is a rapid influx of sodium ions into the membrane, which makes it permeable to sodium ions. This results in depolarization of the membrane, which means that the membrane potential becomes less negative. However, option C states that there is a slow influx of sodium ions, which is incorrect. The correct answer is option C.

After a nerve impulse, the membrane potential of the neuron becomes depolarized due to the influx of sodium ions. However, the resting potential must be restored for the neuron to be able to fire another action potential. This is achieved through the movement of potassium ions out of the cell. After the peak of the action potential, the voltage-gated potassium channels open, and potassium ions move out of the cell due to their concentration gradient. This causes the membrane potential to become more negative, eventually reaching the resting potential. The movement of potassium ions outside the membrane also restores the concentration gradient of potassium ions, which is important for maintaining the resting potential.

Nerve impulses are transmitted from one neuron to another via specialized junctions called synapses. These synapses are the points where the axon terminal of one neuron comes into close proximity with the dendrite of another neuron, or with an effector cell such as a muscle or gland. When a nerve impulse reaches the axon terminal, it triggers the release of chemical compounds known as neurotransmitters, which diffuse across the synapse and bind to specific receptors on the post-synaptic membrane. This binding causes a change in the membrane potential of the post-synaptic neuron or effector cell, which may either excite or inhibit its firing of an action potential. The neurotransmitters are then removed from the synapse by reuptake, enzymatic breakdown, or diffusion, and the synapse is ready to transmit another nerve impulse.

Neurotransmitters are specialized chemical compounds that are released by the presynaptic neuron in response to an action potential. These neurotransmitters then diffuse across the synaptic cleft and bind to specific receptors on the post-synaptic neuron or effector cell, leading to a change in its membrane potential and the transmission of a nerve impulse. There are many different types of neurotransmitters, including acetylcholine, dopamine, serotonin, and norepinephrine, each of which has a unique role in modulating the activity of the nervous system. In contrast, synaptic knobs are the enlarged axon terminals that contain the vesicles of neurotransmitters, while Schwan cells are glial cells that form the myelin sheath around axons and Nissl's granules are clusters of rough endoplasmic reticulum found in the cell bodies of neurons.

Neurotransmitters are specialized chemical compounds that are released by the presynaptic neuron in response to an action potential. These neurotransmitters then diffuse across the synaptic cleft and bind to specific receptors on the post-synaptic neuron or effector cell, leading to a change in its membrane potential and the transmission of a nerve impulse. There are many different types of neurotransmitters, including acetylcholine, dopamine, serotonin, and norepinephrine, each of which has a unique role in modulating the activity of the nervous system. In contrast, synaptic knobs are the enlarged axon terminals that contain the vesicles of neurotransmitters, while Schwan cells are glial cells that form the myelin sheath around axons and Nissl's granules are clusters of rough endoplasmic reticulum found in the cell bodies of neurons.