What is the function of afferent and efferent neurons As it relates to a neuron,

Question

What is the function of afferent and efferent neurons

As it relates to a neuron, describe the terms retrograde and anterograde transport, what is its function and what proteins are involved

What is the difference between leak channels, voltage gated channels, ligated channels and where on the neuron are they located

What 2 factors determine the resting membrane potential

Name the neuroglial cells of the peripheral and central nervous system and the function of each

Describe the electrochemical forces acting on Na, K, Cl

What is the difference between a graded potential and an action potential

What is meant by spatial vs temporal summation; what is the function of summation and does this type of summation occur with graded or action potentials and why

What determines if a graded potential is inhibitory or excitatory

What are the different phases of an action potential? Describe the ions involved in each phases of the action potential

Explanation / Answer

Answere

Function of afferent and efferent neurons

Afferent neurons are the sensory neurons that relays the signals from sensory stimuli towards the central nervous system or brain whereas efferent neurons or motor neurons carry nerve impulses from central nervous system towards muscle to bring movement.

Retrograde and anterograde transport, its function and proteins are involved

The transport of chemical entities, vesicles and organelles inside the axon occur in two ways: anterograde and retrograde axonal transport. When the transport occur from cell body to nerve terminal it is termed as anterograde axonal transport, while the transport of entities from nerve terminal to cell body is called retrograde transport.

The anterograde transport is important for carrying the substances which is essentially required for the nutrition and maintenance of the nerve terminal as well as for normal functioning of synapses. These chenmicals are produced in the cell body, packaged into vesicles and transported to the synaptic bouton via anterograde process. The proteins that take part in this process are dynein/kinesin system of proteins. Contrary to this, retrograde axonal transport brings back the chemical packages to cell body. These chemical signals are important for the maintenance of synaptic contact integrity. The clathrin coated vesicles are believed to mediate the entry of extracellular fluid within synapse. The process is essential in the way that it allows the neuron to know if the contact with the post synaptic cleft is functional.

Difference between leak channels, voltage gated channels, ligated channels and location on neuron

Ion channels are the pores forming proteins present on the plasma membrane that allows the passage of ions through them. The ion channels can be votage gated which means that they open or close on the basis of voltage gradient across the plasma membrane. While the ion channels that are ligated or ligand-gated open or close in response to binding of their specific ligands on their extracellular domain. This in turn brings the conformational change in the protein which allows passage of ions across the membrane. Another type of ion channel is leaky channel which are always open and passivley allows the movement of ions across the membrane down to their concentration gradient (from higher to lower concentraiton). All the ion channels are present on plasma membrane of neuronal cells.

Factors determine the resting membrane potential

Resting membrane potential is the voltage which is present across the plasma membrane during the resting state of cells. Normally its value is -70mV, the minus sign here means that membrane is negatively charged from the inside. The two factors that determine the resting potential are 1) Na+K+ ion concentration gradient across membrane and 2) membrane permeability to these ions. Na+ mainly reside inside the cells whereas K+ are extracellular. K+ ions are passively diffused out of the cells due to leaky channels and is not equally compensated by entry of Na+ beacuse of it poor diffusion rate. This leads to establishing negative charge inside the cells and positive outside the membrane require to maintain resting potential of cells.

Neuroglial cells of the peripheral and central nervous system and their functions

The neuroglian cells are of 6 types, of which 4 are found in central nervous system and 2 in peripheral nervous system.

The CNS neuroglia are:

Astrocytes: helps to maintain the concentration of chemicals in the extracellular space and scavenge excess signaling molecules. Astrocytes also forms scar tissue in the damaged space.

Oligodendrocytes: forms myelin sheaths

Microglia: protects the neuronal tissues from infections, act as a scavenger of debris and waste and plays a key role in the neuronal developmental process.

Ependymal cells: Creates barrier between the compartment and also serves as source of neural stem cells.

The gials cells of peripheral nervous system (PNS) are

Satellite cells: supports cell body

Schwann cells: secretes mylein sheaths and secretes nurotrophic factors

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