lecture 12

Question 1

the motor subdivisions of the PNS are:

Answer 1

somatic (voluntary) and autonomic (involuntary)

Question 2

what do the motor subdivisions of the PNS innervate?

Answer 2

smooth muscle, cardiac muscle, glands

Question 3

the somatic nervous system has ___ neuron(s):

Answer 3

1

Question 4

the autonomic nervous system has ___ neuron(s):

Answer 4

2

Question 5

describe autonomic nervous system’s pathway for motor output

Answer 5

• 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

Question 6

what are the divisions of the autonomic nervous system?

Answer 6

sympathetic and parasympathetic

Question 7

what is the origin of the sympathetic ns?

Answer 7

lateral gray horns of the sc segements T1-L2 (thoracolumbar division)

Question 8

is the sympathetic ns widely distributed to many parts of the body or more limited?

Answer 8

widely distributed to many parts of the body (divergent)

Question 9

why are the effects of the sympathetic ns widely spread?

Answer 9

• 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

Question 10

generally, what is the sympathetic ns responsible for?

Answer 10

situations in which energy needs to be expended (fight or flight)

Question 11

what is the origin of the parasympathetic ns?

Answer 11

brainstem and sc segements S2,3,4 (craniosacral division)

Question 12

is the parasympathetic ns widely distributed to many parts of the body or more limited?

Answer 12

more limited in distribution to target organs (convergent)

Question 13

why are the effects of the parasympathetic ns more limited?

Answer 13

• pregang fibers on only a few postgang neurons

- no comparable organ to the medulla of adrenal gland

Question 14

generally, what is the parasympathetic ns responsible for?

Answer 14

enhances energy storage and conserves energy (rest and digest)

Question 15

describe the sympathetic efferent pathway up to the ganglia

Answer 15

• 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)

Question 16

the preganglionic neuron has three options at the ganglia, what are they?

Answer 16

(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

Question 17

what are the splanchnic nerves?

Answer 17

• greater splanchnic
• lesser splanchnic
• least splanchnic

Question 18

where is the greater splanchnic nerve?

Answer 18

T5-T9 thoracic ganglia

Question 19

where is the lesser splanchnic nerve?

Answer 19

T10-T11 thoracic ganglia

Question 20

where is the least splanchnic nerve?

Answer 20

(T12-L2 thoracic and lumbar ganglia)

Question 21

describe the pathway and function of splanchnic nerves

Answer 21

these nerves synapse in prevertebral ganglia which then sends postgang neurons to abdominal and pelvic viscera

Question 22

a few pregang fibers in the greater splanchnic nerve end directly on cells in the:

Answer 22

adrenal medulla

Question 23

describe sympathetic preganglionic neurons

Answer 23

unmyelinated, shorter than postganglionic, and relatively slow comducting B fibers

Question 24

describe the sympathetic afferent pathway

Answer 24

travels from viscera to the dorsal root ganglia

Question 25

do sympathetic afferent fibers synapse along the way to the sc?

Answer 25

no

Question 26

how do parasympathetic preganglionic neurons leave the brainstem?

Answer 26

through the nuclei of cranial nerves III, VII, IX and X

Question 27

what is the preganglionic nucleus for CN III?

Answer 27

Edinger-Westphal nucleus

Question 28

what is the preganglionic nucleus for CN VII?

Answer 28

superior salivatory and lacrimatory nuclei

Question 29

what is the preganglionic nucleus for CN IX?

Answer 29

inferior salivatory nucleus

Question 30

what is the preganglionic nucleus for CN X?

Answer 30

dorsal nucleus

Question 31

how do parasympathetic preganglionic neurons leave the gray matter of the sc?

Answer 31

through sacral nerves 2, 3, 4, and the spalnchnic nerves

Question 32

where parasympathetic preganglionic fibers synapse?

Answer 32

in ganglia close to viscera

Question 33

what are the cranial parasympathetic ganglia?

Answer 33

- ciliary (CN III) - pterygopalatine (CN VII) - submandibular (CN VII) - otic (CN IX)

Question 34

what are the parasympathetic plexuses?

Answer 34

- cardiac and pulmonary (CN X) - celiac (CN X) - hypogastric (CN X)

Question 35

what are the sacral parasympathetic ganglia?

Answer 35

pelvic splancnic nerves synapse in ganglia of the hypogastric plexus

Question 36

describe the parasympathetic postganglionic neurons

Answer 36

short, unmyelinated, smaller than preganglionic and slower conducting C fibers

Question 37

what do postganglionic neurons from CNs III, VII, and IX supply?

Answer 37

head

Question 38

what do postganglionic neurons from CN X supply?

Answer 38

thorax and descending colon

Question 39

what do postganglionic neurons from S2,3,4 supply?

Answer 39

terminal gut and pelvic vicsera (bladder/repro organs)

Question 40

describe the parasympathetic afferent pathway

Answer 40

myelinated fibers travel from the vicera to their cell bodies located in the sensory ganglia of cranial nerves or in the dorsal root ganglia of the sacral spinal nerves

Question 41

how are sympathetic postganglionic neurons activated? what are the receptors involved?

Answer 41

ach (nicotinic receptors)

Question 42

how are parasympathetic postganglionic neurons activated? what are the receptors involved?

Answer 42

ach (nicotinic receptors)

Question 43

what do sympathetic postganglionic neurons release? what are the receptors involved?

Answer 43

norepinephrine (a/b receptors)

Question 44

what do parasympathetic postganglionic neurons release? what are the receptors involved?

Answer 44

ach (muscarinic receptors)

Question 45

are there any exceptions to NT activation/release?

Answer 45

yes - sympathetic postganglionic neurons that end on cells of sweat glands release Ach (cholinergic receptors)

Question 46

what are the levels of autonomic control?

Answer 46

- hypothalamus (regulation btwn two systems) - pons, medulla (regulation of autonomic functions) - cortex, limbic system (motor arises, sensory arrives)

Question 47

compare neuron length for pre/postganglionic neurons in the sympathetic and parasympathetic ns's

Answer 47

symp: short pre, long post para: long pre, short post