Terminology and structure of Nerves. Watch

Jonn ,LR
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Hello

Have I got this right?

A nerve cell (soma, dendrites and axon) is also called a neuron or if the nerve cell has a myelin sheath it is then generally called a nerve fiber.

Many nerve cells (running parallel to each other) make up an actual nerve. Therefore a nerve is a collection of nerve cells, Glial cells and blood vessels.

In regards to the PNS, one of many such nerve cells will stretch, unbroken, from the spinal cord all the way, for example, to the finger tip, or in the case of the sciatic nerve, the big toe.

That a nerve cell will not link to another nerve cell, which links to another nerve cell and so on as it stretches from the spinal cord to the finger tips, that it is only one cell (soma, dendrites and axon process) that extends this distance.

Lastly, therefore the dendrites (if a sensory neuron) will connect directly to the sense receptors, say in the skin, and the axon (synaptic terminal), of the same nerve cell, will connect to the dendrites of a nerve cell in the spinal cord.

John
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Jpw1097
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(Original post by Jonn ,LR)
Hello

Have I got this right?

A nerve cell (soma, dendrites and axon) is also called a neuron or if the nerve cell has a myelin sheath it is then generally called a nerve fiber.

Many nerve cells (running parallel to each other) make up an actual nerve. Therefore a nerve is a collection of nerve cells, Glial cells and blood vessels.

In regards to the PNS, one of many such nerve cells will stretch, unbroken, from the spinal cord all the way, for example, to the finger tip, or in the case of the sciatic nerve, the big toe.

That a nerve cell will not link to another nerve cell, which links to another nerve cell and so on as it stretches from the spinal cord to the finger tips, that it is only one cell (soma, dendrites and axon process) that extends this distance.

Lastly, therefore the dendrites (if a sensory neuron) will connect directly to the sense receptors, say in the skin, and the axon (synaptic terminal), of the same nerve cell, will connect to the dendrites of a nerve cell in the spinal cord.

John
Yes, you're right that generally when people say nerve cells they mean neurones, although as you've mentionned, you do also have glial cells such as astrocytes, microglia, oligodendrocytes, Schwann cells, etc.

Individual neurones are wrapped in loose connective tissue called endoneurium. Many neurones are grouped together into fascicles and enclosed in perineurium, another layer of connective tissue. Several fascicles are enclosed in a layer of dense, irregular connective tissue called epineurium. A nerve is made up of lots of neurones, fascicles (groups of neurones) and is enclosed in epineurium. And yes, nerves have lots of blood vessels as neurones are very metabolically active and therefore require lots of oxygen and nutrients.

You're right, in the somatic peripheral nervous system, neurones extend from the CNS to wherever they need to go, which could be as you've said the finger tip or big toe, without synapsing. However, in the autonomic nervous system, neurones synapase first in ganglia before reaching their target. You get preganglionic neruones which extend from the CNS (i.e. brain and spinal cord) to ganglia, where they synapse with postganglionic neurones which then innervate the target organ/tissue.

Again, you're right, sensory receptors at the end of sensory neurones respond to stimuli and this signal is transmitted along the sensory neurones axon which synapses with dendrites of neurones in the CNS.
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Jonn ,LR
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Good Morning

Thanks for the feedback, helped me a great deal - Jonn
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