lecture 12 Flashcards
the motor subdivisions of the PNS are:
somatic (voluntary) and autonomic (involuntary)
what do the motor subdivisions of the PNS innervate?
smooth muscle, cardiac muscle, glands
the somatic nervous system has ___ neuron(s):
1
the autonomic nervous system has ___ neuron(s):
2
describe autonomic nervous system’s pathway for motor output
- one preganglionic and one postganglionic neuron (one is short and one is long)
- pre has its cell body in the CNS
- pre = B fibre (faster)
- pre synapses on ganglion
- post has its cell body outside the CNS
- post = C fibre (slower)
- post synapses on target tissue
what are the divisions of the autonomic nervous system?
sympathetic and parasympathetic
what is the origin of the sympathetic ns?
lateral gray horns of the sc segements T1-L2 (thoracolumbar division)
is the sympathetic ns widely distributed to many parts of the body or more limited?
widely distributed to many parts of the body (divergent)
why are the effects of the sympathetic ns widely spread?
- because one pregang fiber can synapse with many postgang fibers
- also medulla of adrenal gland releases sympthatheic NTs epinephrine and norepinephrine which travel through the blood across most of the body
generally, what is the sympathetic ns responsible for?
situations in which energy needs to be expended (fight or flight)
what is the origin of the parasympathetic ns?
brainstem and sc segements S2,3,4 (craniosacral division)
is the parasympathetic ns widely distributed to many parts of the body or more limited?
more limited in distribution to target organs (convergent)
why are the effects of the parasympathetic ns more limited?
- pregang fibers on only a few postgang neurons
- no comparable organ to the medulla of adrenal gland
generally, what is the parasympathetic ns responsible for?
enhances energy storage and conserves energy (rest and digest)
describe the sympathetic efferent pathway up to the ganglia
- myelinated pregang neurons from lateral horn leave the sc via the ventral nerve root
- pass through the spinal nerve and then leave via ramus to sympathetic trunk (paravertebral ganglia)
the preganglionic neuron has three options at the ganglia, what are they?
(1) synapse, then unmyelinated postgang neurons pass through the ramus to enter the spinal nerve and then onward to the target site
(2) pregang neurons can travel up or down the sympathetic trunk to synapse in another paravertebral ganglia, then postgang neurons pass through the ramus to enter the spinal nerve and then onward to target site
(3) pregang neurons can pass through the sympathetic trunk without synapsing, to form the splanchnic nerves
what are the splanchnic nerves?
- greater splanchnic
- lesser splanchnic
- least splanchnic
where is the greater splanchnic nerve?
T5-T9 thoracic ganglia