Nervous System 2

Question 1

Autonomic NS

Answer 1

• Motor nerves to smooth and cardiac muscle visceral motor efferent
• two divisions: sympathetic and parasympathetic

Question 2

Divisions of autonomic NS

Answer 2

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

Question 3

1st and 2nd order neuron locations

Answer 3

• 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

Question 4

1st order neuron

2nd order neuron

Answer 4

1st - tend to be more myelinated therefore white

2nd - tend to be less myelinated and therefore grey

Question 5

Distribution of sympathetic system

Answer 5

• 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

Question 6

Distribution of parasympathetic system

Answer 6

• restricted to visceral organs apart from head and genitalia
• no PS innervation of kidney and adrenal medulla

Question 7

Tone of neurones

Answer 7

• continuous active basal rate of action potential = tone

- fine control achieved b increasing or decreasing tone

Question 8

Antagonism

Answer 8

• 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

Question 9

Sensory nerves

Answer 9

• run back from viscera following route of autonomic nerves
• referred to as visceral sensory
• similar to somatic sensory
• not strictly pat of ANS

Question 10

SYMPATHETIC VS PARASYMPATHETIC

Answer 10

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

Question 11

Sympathetic outflow from CNS origin and routes taken from lat horn

Answer 11

• 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

Question 12

Sympathetic chain running from C1 to C2/3

Answer 12

• 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

Question 13

L7 IMPAR GANGLION

Answer 13

Point of mergence of left and right chain ganglion

Question 14

Paravertebral collateral ganglia

Answer 14

• 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

Question 15

Paravertebral collateral ganglia origins

Answer 15

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
-

Question 16

Splanchnic nerves

Answer 16

• 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

Question 17

Sympathetic supply to thoracic viscera

ORIGIN, 1ST ORDER PATHWAY, GANGLION, 2ND ORDER PATHWAY, TARGET ORGAN

Answer 17

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

Question 18

Sympathetic supply to the head

Answer 18

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

Question 19

Sympathetic supply to abdominal viscera - ganglia and arteries

Answer 19

• 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

Question 20

Sympathetic supply to the foregut

Answer 20

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

Question 21

Sympathetic supply to midgut

Answer 21

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

Question 22

Sympathetic supply to hindgut

Answer 22

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

Question 23

Sympathetic supply to blood vessels, skin of trunk and limbs

Answer 23

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

Question 24

Sympathetic supply to blood vessels and skin of neck

Answer 24

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

Question 25

PARASYMPATHETIC INNERVATION | Restrictions, outflow and pairs of nerves

Answer 25

- restricted to glands and viscera - craniosacral outflow - 12 pairs of cranial nerves - 4 contain PS fibres CN III = oculomotor CN VII = facial CN IX = glossopharyngeal CN X = vagus

Question 26

Vagus nerve

Answer 26

Contains 75% of all ps fibres in the body - innervates thoracic and abdominal viscera Pelvic nerves innervate urogenital and caudal abdominal viscera

Question 27

Parasympathetic supply to thoracic viscera

Answer 27

O; L and R vagal nucleus in brain stem 1OP; R and L vagus, L and R vagosympathetic trunks, cardiovagal nerves 2OP; synapse on/close to target organ - very short 2nd order neurones Target; heart, bronchiole smooth muscle - r and l vagi continue along oesophagus where they split and reunite as dorsal and ventral vagi - dorsal and ventral vagi pass through diaphragm on oesophagus into abdominal cavity

Question 28

Parasympathetic supply to fore and midgut viscera

Answer 28

1OP; after passing through diaphragm on oeseophagus - ventral vagus; supplies lesser curvature of stomach, liver and ventral pancreas - dorsal vagus; supplies greater curvature of stomach and then continues to supply remainder of foregut as plexus on coeliac artery - dorsal vagus continues to supply midgut as plexus on cranial mesenteric artery 2OP; synapse on/close to target organ - very short 2nd order neurones

Question 29

Parasympathetic supply to pelvic viscera

Answer 29

O; sacral segments 1 and 2 1OP; pelvic nerves to pelvic plexus 2OP; synapse on/close to target organ - very short 2nd order neurones Target; rectum, anal canal, ureter, bladder, urethra, genitalia

Question 30

Parasympathetic supply to hindgut viscera

Answer 30

O; sacral segments 1 and 2 1OP; pelvic nerves to pelvic plexus then along gut wall to hind gut OR pelvic nerves, pelvic plexus, hypogastric nerve, plexus on caudal mesenteric a 2OP; synapse on/close to target organ - very short 2nd order neurones Target; hindgut viscera

Question 31

Clinical conditions

Answer 31

- surgical consideration - dysautonomia = neuropathy of ANS neurones, fatigue/depression, hypotension/hypertension, exercise intolerance, digestive problems, urinary problem, sweating

Question 32

Veterinary syndromes

Answer 32

- grass sickness: clostridium butulinum - key Gaskell syndrome: autonomic ganglia degen = toxin, depression, regurgitation, constipation, dilated pupils, 3rd eyelid - horners syndrome: damage to sympathetic supply to head often unilateral, constricted pupil, protrusion of 3rd eyelid and droopy upper lid