Week 3; anatomy of the PNS and autonomic nervous system Flashcards
What do sensory nerves do?
afferent nerves carry information from sensory receptors to the CNS.
What are the two body parts included in sensory division?
- somatic (skin, muscles, joints)
- visceral organs
What do motor nerves do?
Efferent nerves carry information away from the CNS
What are the two body parts included in motor division?
- somatic nerves innervate skeletal muscles
- autonomic nerves innervate glands, cardiac and smooth muscle
3 key anatomical differences between sympathetic and parasympathetic division?
- sites of origin
- length of axons
- location of ganglia
2 types of nerves in the PNS:
- cranial nerves
- spinal nerves
3 nerves classified on impulse and direction:
- sensory
- motor
- mixed
3 connective tissue in PNS
- epineurium (surrounds peripheral nervous)
- perineurium (surrounds fascicles)
- endoneurium (surrounds individual nerve axons)
2 different types of roots
- dorsal root - sensory
- ventral root - motor
How many spinal cords are there ?
31 spinal cords
- 8 cervical
- 12 thoriac
- 5 lumbar
- 5 sacral
- 1 coccygeal
What is ramus?
Ramus is the site where dorsal and ventral nerves meet and become mixed spinal nerves
what is dorsal rami ?
provide motor and sensory innervation to the skin and back (smaller)
What is ventral rami?
provide sensory and motor innervation to the trunk and rest of limbs (bigger)
What are nerve plexuses ?
they are formed by ventral rami. Fibres from each rami project to periphery via many pathways. They are important incase a nerve is damaged, means the part still has nerves and functions and isn’t destroyed.
4 types of nerve plexuses and their functions:
- cervical - located under the sternocleidomastoid
- brachial - neck and shoulder, innervates the arm
- lumbar - located within the psoas muscle, innervates abdominal wall, anterior and medial thigh
- sacral - posterior to lumbar, innervates buttocks, pelvis and lower limbs
What ventral rami is the brachial plexus made from?
C5-C8 and T1
What are the 4 parts of brachial plexuses?
- 5 roots
- 3 trunks
- 3 cords
- 5 peripheral nerves
5 peripheral nerves in the brachial plexuses?
axillary, musculocutaneous, ulnar, radial, median
How many cranial nerves are there and where are they attached?
12 cranial nerves
- CN1 attaches to cerebrum
- CN11 attaches to diencephalon
- CN111-CNXII attach to brainstem
What does the ANS control?
glands, cardiac muscle, smooth muscle, adipose tissue
What does the ANS maintain?
homeostatis, body temp, heart rate, blood pressure, water
what are the target organs of the ANS?
thoracic and abdominopelvic cavities + the body wall
definition of preganglionic neurons
found in the CNS, before reaching the ganglion, axons are called preganglionic fibers
definition of postganglionic neurons
found in the PNS, cell bodies in the autonomic ganglia, axons are called postganglionic fibers
Anatomy of sympathetic division
cell bodies of the preganglionic neurons are in the lateral horn of the spinal cord. preganglionic fibers leave the spinal cord at the ventral roots at the thoracic and superior lumbar segments
- synapse close to spinal cord, preganglionic fibers are short, post ganglionic fibers are long
recite diagram from wall : division of sympathetic division
…..
3 divisions of ganglia
- sympathetic chain ganglia
- collateral ganglia
- adrenal medullae
How does adrenal medullae supplement the sympathetic NS?
- increases metabolism. Lasts 5-10x longer than ANS. Reaches all tissues of the body and releases epinephrine and norepinephrine to 100% of the body
Anatomy of parasympathetic division:
The cell bodies of parasympathetic division are in the brain stem and sacral segment of the spinal cord. They synapse with ganglia within close range to the target organ, preganglionic neurons are long and postganglionic neurons are short.
What is the vagus nerve ?
provides 75% of all parasympathetic outflow
What neurotransmitter does parasympathetic division produce?
ach - acetylcholine
What neurotransmitter does sympathetic division produce?
norepinephrine / noradrenaline
cholinergic receptors
all parasympathetic division - cells that respond to ach
1. nicotonic receptors:
all ganglionic neurons, release influx of na+ through cation channels
EXCITATORY
2. muscarnic receptors
all parasympathetic target organs e.g glands, cardiac, smooth muscle
EXCITATORY OR INHIBITORY
adrenergic receptors
bind epinephrine and norepinephrine with differing affinities. found on sympathetic target organs, alpha and beta receptor types
