lecture 11 : the peripheral nervous system Flashcards
what does the peripheral nervous system consist of?
the peripheral nerves and the ganglia
what is a dorsal root ganglia?
this is a sensory ganglion
what is the structure of a dorsal root ganglion?
- the dorsal root ganglion is surrounded by a connective tissue capsule - inside the capsule is a mixture of neural cell bodies and axons
what is the structure of a single sensory neurone?
- there is a dark nucleus inside a pale nucleus - the small nuclei are the satellite cells which support the neurones - the sensory neurones are pseudo unipolar
where do the sensory neurone cell bodies lie?
they lie in the ganglia associated with the spinal dorsal roots or some cranial nerves
where do post ganglionic neuronal soma lie? how are they arranged?
they lie in the autonomic ganglia they are arranged in rows (sympathetic) or they are arranged closer to the internal organs ( parasympathetic)
what are the axon bundles called? what do these group to make?
the bundles are called fascicles they are grouped to make nerves
what are the three layers of connective tissue in nerves
- epineurium - connective tissue which surrounds the nerve 2. perineurium - this is the connective tissue that surrounds the fascicles 3. endoneurium - this is the connective tissue that surrounds the axons
what is the axon diameter of a myelinated cell?
1.5- 2 micrometers
what is the axon diameter of a non myelinated cell?
1 micrometer
what are the features of myelinated cells?
- they are clothed in succession of schwann cells - separated by the nodes of ranvier - the myelination allows the saltatory conduction to take place
what are the features of non myelinated cells?
each axon only has one single layer of membrane and there is no saltatory conduction
where are schwann cells present?
they are present on both non myelinated and myelinated cells
* show the structure of somatic, autonomic and sensory neurones:
* insert the pic - somatic neurones have their soma in the CNS - autonomic motor neurones have a preganglionic and postganglionic motor neurone - sensory neurones have a ganglion in the middle

* show a diagram of a spinal cord segment:
insert pic

what are the main 3 things that make up the spinal cord segment?
- the dorsal horn - the ventral horn - the spinal nerve
what are the four types of neurone?
- somatic neurone info from non internal organs 2. somatic motor controls the striated muscle 3. autonomic sensory sensory from internal organs 4. autonomic motor controls the internal organs
where are somatic sensory somatic motor and autonomic nerves found?
- somatic sensory and somatic motor are found in all spinal nerves - autonomic is found is most spinal nerves
what is the myotome?
this is the muscle area that the spinal nerve innervates
what is the dermatome?
this is the skin that the spinal nerve innervates
what is a plexus?
a plexus is when spinal nerves are combined to form peripheral nerves
what is ramus?
this is when as the spinal nerves leave the spinal cord some merge together and later divide into rami
what is the significance of rami?
- it gives rise to the mixing of spinal nerves so by the time one has 3 peripheral nerves emerging from the bottom of a plexus each of the nerves have axons that originate from more than one spinal nerve
where do we have spinal nerves and where do we have peripheral nerves?
spinal nerves - before the plexus peripheral nerves - after the plexus
