Nervous System 2 Flashcards
Autonomic NS
- Motor nerves to smooth and cardiac muscle visceral motor efferent
- two divisions: sympathetic and parasympathetic
Divisions of autonomic NS
Sympathetic
- fight and flight
- protective response
- elevated heart rate, bp, respiratory rate , increased blood flow to skeletal mm heart brain lungs
Parasympathetic
- rest and digest
- quiet stress free situation
- reset system after parasympathetic activation e.g. slows HR, decreases BP
- dominates digestive tract innervation
1st and 2nd order neuron locations
- always and only 2 between cns and target organ often travelling as plexi along blood vessels
- cel body of 1st order neuron is preganglionic, in CNS
- cell body of 2nd order neuron postganglionic and somewhat peripheral (neural crest) > these cell bodies gathered together in a ganglion esp sympathetic nerves
1st order neuron
2nd order neuron
1st - tend to be more myelinated therefore white
2nd - tend to be less myelinated and therefore grey
Distribution of sympathetic system
- widely distributed, goes to smooth muscle of body
- smooth muscle of skin, blood vessels only receive SYMPATHETIC innervation
- 1st sympathetic neurones innervate adrenal medulla»_space; systemic sympathetic activation via release of catechloamines into blood stream
Distribution of parasympathetic system
- restricted to visceral organs apart from head and genitalia
- no PS innervation of kidney and adrenal medulla
Tone of neurones
- continuous active basal rate of action potential = tone
- fine control achieved b increasing or decreasing tone
Antagonism
- 2 systems innervate an organ, they tend to be antagonistic, one will usually dominate e.g. heart sympathetic and guts parasympathetic
- not always anatgonistic
»> male reproduction: parasympathetic gives erection and sympathetic gives ejaculation
Sensory nerves
- run back from viscera following route of autonomic nerves
- referred to as visceral sensory
- similar to somatic sensory
- not strictly pat of ANS
SYMPATHETIC VS PARASYMPATHETIC
DISTRIBUTION: s cardiac and all smooth muscle, p cardiac and smooth muscle of viscera only
ORIGIN: s thoracolumbar and grey matter of spinal cords t1-l4, p craniosacral CN nuclei and grey matter of s1-2
SYNAPSE OF 1/2 ORDER NEURONS: s in discrete ganglia, p often independently on or near target organs
1st ORDER: 2nd ORDER LENGTH: short:long vs long:short
Sympathetic outflow from CNS origin and routes taken from lat horn
- first order neurone found in lat horn of grey matter T1-L4
- axon travels down ventral root to spinal nerve then down raamus communicants to sympathetic chain
- from the chain it can:
synapse immediately with 2nd neuron, travel up and down the chain before synapsing, pass straight through chain to synapse in an outlying prevertebral ganglion with 2nd order neurone - 2nd order axons pass to target organs from chain/ganglia
- 2nd order neurons found in discrete ganglia associated with each Ramos communicans
Sympathetic chain running from C1 to C2/3
- C1-3 CRANIAL CERVICAL GANGLION @base of skul here commo carotid divides into int and ext carotid aa
- sympathetic trunk runs along common carotid artery up the neck
- C4-6 MIDDLE CERVICAL GANGLION ventral to subclavian artery near thoracic inlet
- C7-T3 CERVICO-THORACIC GANGLION C7-T3 found on lateral surface of longus colli muscle dorsal to subclavian artery
L7 IMPAR GANGLION
Point of mergence of left and right chain ganglion
Paravertebral collateral ganglia
- lie beyond sympathetic chain
- 1st. Order fibres pass straight through the sympathetic chain to synapse in these outlying ganglia
- 3 main one associated with 3 large unpaired arteries supplying abdomen :
Coeliac ganglion
Cranial mesenteric
Caudal mesenteric - connected to sympathetic chain by SPLANCHNIC NERVES
Paravertebral collateral ganglia origins
Coeliac ganglion found at root of coeliac artery
Cranial mesenteric found at root of cranial mesenteric artery
Caudal mesenteric found at root of caudal mesenteric artery
-
Splanchnic nerves
- one greater t11-12 connecting to coeliac ganglion - several lesser t13-l1 splanchnics connecting central mesenteric ganglia
- lumbar splanchnics L3,4&5 connect to caudal mesenteric ganglion
Sympathetic supply to thoracic viscera
ORIGIN, 1ST ORDER PATHWAY, GANGLION, 2ND ORDER PATHWAY, TARGET ORGAN
O - T1-T4
1OP - ventral root, spinal nerve, ramus communicans, sympathetic chain
Ganglion - cervico-thoracic or middle cervical ganglion
2OP - cardio sympathetic nerves
Target: heart, bronchiole sm, blood vessel sm
Sympathetic supply to the head
O; T1-4
1OP: ventral root, spinal nerve, ramus communicans, sympathetic chain
Ganglion; cranial cervical ganglion
2OP; nerve plexi on internal and external carotid arteries
TARGET: salivary glands, smooth muscle of pupil, blood vessel smooth muscle
Sympathetic supply to abdominal viscera - ganglia and arteries
- coeliac, cranial mesenteric and caudal mesenteric ganglia are situated at roots of:
- coeliac artery = foregut
- cranial mesenteric artery = midgut
- caudal mesenteric artery = hindgut
- plexi of 2nd order neurons run down arteries to supply all of abdominal viscera
Sympathetic supply to the foregut
O; T1-L4 1OP; ventral root, spinal nerve, ramus communicans, sympathetic chain, greater and lesser splanchnic nerves Ganglion; coeliac 2OP; plexus on coeliac artery Target; foregut viscera
Sympathetic supply to midgut
O; t1-l4 1OP; ventral root, spinal nerve, ramus communicans, sympathetic chain, lesser splanchnic nerves Ganglion; cranial mesenteric ganglion 2OP; plexus on cranial mesenteric artery Target; midgut viscera
Sympathetic supply to hindgut
O; t1-l4 1OP; ventral root, spinal nerve, ramus communicans, sympathetic chain, lumbar splanchnics Ganglion; caudal mesenteric ganglion 2OP; hypogastric nerve to pelvic plexus Target; pelvic viscera
Sympathetic supply to blood vessels, skin of trunk and limbs
O; t1-l4
1OP; ventral root, spinal nerve, ramus communicans, sympathetic chain
Ganglion - sympathetic chain ganglia
2OP; rami communicans back to spinal nerves SN, dorsal or ventral branches of SNs
Target; blood vessel smooth muscle, arrector pili sm, sweat gland sm
Sympathetic supply to blood vessels and skin of neck
O; T1-L4
1OP; ventral root, spinal nerve, ramus communicans, sympathetic chain
Ganglion; cervical-thoracic ganglion
2OP; directly from ganglion to spinal nerves of c7/8 along plexus on vertebral a to spinal nerves c1-6
Target; blood vessel smooth muscle, arrector pili smooth muscle, sweat gland smooth muscle
