Peripheral Nervous System And Synaptic Pharmacology 3: The Synapse

Specialized synapses refer to synapses that are specifically adapted to carry out specific functions in certain tissues. These synapses have unique characteristics and structures that enable them to efficiently transmit signals between neurons. Therefore, the statement "Specialized synapses are in certain tissues" is true, as these synapses are indeed found in specific tissues where their specialized functions are required.

Acetylcholine is the correct answer because it is the primary neurotransmitter involved in transmitting signals from motor neurons to muscle fibers in the neuromuscular junction. It binds to receptors on the muscle fiber, causing muscle contraction. Ethanol, dopamine, and noradrenaline are not neurotransmitters involved in the neuromuscular junction.

Chemical synapses are specialized junctions between neurons where communication occurs through the release and binding of neurotransmitters. Neurotransmitters are chemical messengers that transmit signals across the synapse from the presynaptic neuron to the postsynaptic neuron. This process allows for the transmission of information and coordination of neuronal activity in the nervous system. Gap junctions, on the other hand, are direct channels between cells that allow for the passage of ions and small molecules, but they are not involved in the transmission of signals between neurons.

The statement is true because synapses are the junctions between neurons where communication occurs. Neurons transmit signals to other neurons or target organs through these synapses. At the synapse, electrical signals from the transmitting neuron are converted into chemical signals, which then travel across the synapse and are received by the next neuron or target organ. This communication is crucial for the functioning of the nervous system and the coordination of various physiological processes.

Some synapses are inhibitory, meaning that when they are activated, they actually cause the neuronal membrane potential to become more negative, a process known as hyperpolarization. This inhibitory effect reduces the likelihood of the neuron firing an action potential, thus decreasing neuronal activity. Therefore, the statement that some synapses cause hyperpolarization of the neuronal membrane potential is true.

The statement is true because the alpha-motor neuron, which is responsible for initiating muscle contractions, can synapse with multiple muscle fibers. This allows for the activation of a group of muscle fibers simultaneously, resulting in coordinated and efficient muscle contractions. This divergent pathway ensures that the alpha-motor neuron can control and coordinate the movements of multiple muscle fibers at once.

The human nervous system contains an incredibly large number of synapses, estimated to be around 10^14. Synapses are the connections between neurons that allow for communication and transmission of signals. This vast number of synapses is crucial for the complex functioning of the nervous system, enabling the processing and integration of information throughout the body.

The first stage of synaptic transmission is the propagation of an action potential to the terminal of a presynaptic membrane. This action potential is an electrical signal that travels down the axon of the neuron to reach the terminal. Once the action potential reaches the terminal, it triggers the release of neurotransmitters by exocytosis into the synaptic cleft. The neurotransmitters then bind to receptors on the postsynaptic membrane, initiating the transmission of the chemical signal across the synapse. The entry of Ca2+ into the synaptic knob is an important step in the release of neurotransmitters, but it occurs after the propagation of the action potential.

In the fourth stage of synaptic transmission, the neurotransmitter binds to specific sites on the postsynaptic neuron. This binding allows the neurotransmitter to transmit its signal to the postsynaptic neuron, initiating a response. The binding of the neurotransmitter to these specific sites triggers a series of biochemical events within the postsynaptic neuron, ultimately leading to the transmission of the signal. This stage is crucial for the communication between neurons and the transmission of information in the nervous system.

The third stage of synaptic transmission involves the release of neurotransmitter molecules into the synaptic cleft. This release is achieved through exocytosis, a process by which the neurotransmitter-containing vesicles fuse with the presynaptic membrane and release their contents into the synapse. This allows the neurotransmitter to diffuse across the synaptic cleft and bind to receptors on the postsynaptic membrane, initiating the transmission of the chemical signal to the next neuron or target cell.

E. synapses cause depolarisation of a neuronal membrane potential.

Electrical synapses refer to the direct transfer of electrical signals between cells through specialized channels called gap junctions. These gap junctions allow for the passage of ions and small molecules, enabling the rapid and synchronized transmission of electrical impulses. In contrast, communication via neurotransmitters involves the release and binding of chemical messengers to transmit signals between neurons. Therefore, the correct answer is that electrical synapses communicate via gap junctions.

Neurotransmitter may also be removed from the synaptic cleft via reabsorption into the synapse.

In the second stage of synaptic transmission, Ca2+ enters the synaptic knob/presynaptic terminal. This is an important step because the influx of Ca2+ triggers the release of neurotransmitters by exocytosis into the synaptic cleft. This release of neurotransmitters allows for the chemical signal to be transmitted from the presynaptic neuron to the postsynaptic neuron. The entry of Ca2+ is necessary for the proper functioning of synaptic transmission and plays a crucial role in the communication between neurons.

The neuromuscular junction is the synapse between a motor neuron and a muscle fiber. It is responsible for transmitting signals from the motor neuron to the muscle fiber, allowing for muscle contraction. This process is part of the somatic efferent nervous system, which controls voluntary muscle movements. Therefore, the correct answer is "The peripheral synapse of the somatic efferent nervous system."

The alpha-motor neuron originates from the central nervous system (CNS) with its cell body located in the grey matter of the spinal cord or brain stem. This means that the neuron is part of the CNS and its cell body is situated in the regions of the spinal cord or brain stem where the grey matter is present.

In the sixth stage of synaptic transmission, the neurotransmitter is removed from the synaptic cleft. This is an important step to ensure that the signal is not continuously transmitted and that the synapse can be ready for the next signal. The removal of neurotransmitter can occur through various mechanisms such as reuptake by the presynaptic neuron or enzymatic degradation. By removing the neurotransmitter, the synaptic cleft is cleared, allowing for the termination of the signal and preventing overstimulation of the postsynaptic neuron.

*alpha-motor neuron

A divergent pathway is one where a single synapse communicates with many neurons.

In the fifth stage of synaptic transmission, specific ion channels open in the subsynaptic membrane. This allows for the flow of ions into or out of the postsynaptic neuron, which generates an electrical signal. This signal is essential for the transmission of the chemical signal across the synapse. The opening of specific ion channels is a crucial step in the process of synaptic transmission, as it enables the propagation of the signal from the presynaptic neuron to the postsynaptic neuron.