ANS

Question 1

ANS

Answer 1

divided in sympathetic and parasymapthetic + enteric nervous system (GIT)

Question 2

preganglionic

Answer 2

lightly myelinated slow conducting, thin, type B
conduction speed = 100 m/s

originates from the intermediolateral area of the grey horn from spinal regions:
T1 - T 12
L1 - L2

Question 3

postganglionic

Answer 3

unmyelinated slow conducting, very thin, type C
conduction speed = 1 m/s

ganglion is collection of cell bodies outside of CNS.

Question 4

denervation of autonomic nervous system

Answer 4

denervation hypersensitivity as up-regulation of NAChR receptors occurs and there is an exaggerated response to exogenous agonists.

Question 5

primary organs ANS

Answer 5

viscera of thoracic and abdominal cavities
cutaneous blood vessels
sweat glands
piloerector muscles

Question 6

SNS

Answer 6

originates in ventral/anterior horn and travels uninterrupted.
myelinated fast conducting type A alpha motor neurons. conducting 1000 m/s

Question 7

denervation of SNS

Answer 7

flaccid paralysis and atrophy due to lack of innervation and activity at the muscle site

Question 8

organisation of sympathetic nervous system

Answer 8

preganglionic originate at the intermediolateral area of grey horn. exit via the ventral roots and enter the sympathetic trunk via white ramus communicans.

synapse in the sympathetic trunk at the same spinal level and can then ascend or descend by entering para vertebral ganglion or passing to collateral ganglia.

postganglionic leave sympathetic trunk via gray ramus.

Question 9

somatic neurons

Answer 9

monosynaptic
NT = ACh
receptor = Nicotinic 1 type

Question 10

sympathetic neurons

Answer 10

cardiac tissue, smooth muscle and gland cells:
NT = NE
receptor = alpha and beta receptors

sweat glands:
NT = ACh
receptor = Muscarinic

Renal tissue:
NT = dopamine
receptor = dopamine 1

Question 11

all preganglionic neurons

Answer 11

NT = ACh
receptor = Nicotinic type 2

Question 12

parasympathetic neurons

Answer 12

NT = ACh
receptor = muscarinic receptor

Question 13

block N1 type receptor

Answer 13

pancuronium is selective N1 type agonist and is used for general anaesthesia

Question 14

block N2 type receptor

Answer 14

trimethaphan is selective N2 type agonist and blocks both arms of the ANS, used for treatment of hypertensive crisis

Question 15

endocrine ANS neuron

Answer 15

adrenal meduall activation releases:
20% NE
80% epinephrine

NE endocrine release adds to effect of sympathetic stimulation on alpha and beta receptors

Question 16

adrenal medulla enzyme

Answer 16

phenyl ethanolamine N methyl transferase converts NE into —–> epinephrine

Question 17

epinephrine effects

Answer 17

epinephrine stimulates beta receptor to a greater extent.
epinephrine causes weak constriction of blood vessels.
epinephrine is 5 - 10 times more effective in stimulating metabolism.

Question 18

vascular tone and denervation of the ANS

Answer 18

initially: marked increase in blood flow as vascular tone is lost

following days to weeks: vascular tone returns towards normal because of progressive increase in intrinsic tone of vascular muscle.

following test doses of NE: the response of vessels to NE (constriction) can increase 3 to 4 fold due to upregulation of receptors at denervation site.

Question 19

organs with only sympathetic innervation

Answer 19

kidneys, liver, arterioles and veins, piloerection and sweating

Question 20

beta1 adrenergic receptors only

Answer 20

heart + kidneys

Question 21

alpha receptors only

Answer 21

eyes, endocrine pancreas, exocrine pancreas, sex organs

Question 22

both alpha and beta receptors

Answer 22

arteries and veins, salivary glands, stomach, urinary bladder

Question 23

alpha 1 receptor activation

Answer 23

always contraction in its target areas

vascular smooth muscle of skin, splanchnic region, sphincters of the GIT and urinary tract, radial muscle of the iris.

NE binds to alpha 1 receptor triggering a conformational change in the GqPCR at the membrane. the alpha q subunit is inactive when bound to GDP.

conformational change of GPCR causes alpha q subunit to bind to GTP and be released into the cytosol.

alpha q bound to GTP interacts with phospholipase C triggering the activation of PIP2.

PIP2 allows the liberation of diacyclgycerol and IP3.
IP3 activates calcium release from ER/SR.
diacyglycerol in the presence of calcium will activate protein kinase C.

protein kinase C has a major role in phosphorylating various proteins in the cell.

Question 24

beta receptors

Answer 24

beta1 receptor activation in SA node causes heart rate increase and increase in contractility of the heart, renin secretion in the kidney.

NE binds to beta receptor causing a conformation change in GsPCR at the membrane.

alpha s subunit is inactive when bound to GDP and becomes active and released when conformational change occurs and bound to GTP.

alpha s bound to GTP will phosphorylate adenyl cyclase.

phosphorylated adenyl cyclase converts ATP to cAMP (second messenger).

cAMP activates protein kinases and induces downstream changes.

Question 25

nicotinic AChR

Answer 25

ligand gated with ion channel (for potassium out, sodium in) as part of the receptor itself.

always excitatory

Question 26

muscarinic AChR

Answer 26

GPCR. binding to muscarinic receptor causes conformational change in membrane proteins which in turn affects release

longer lasting effects and can be both excitatory or inhibitory

excitatory: (smooth muscle of digestive tract)
causes contraction when potassium channels close and sodium channels open allowing depolarisation

inhibitory: (slow heart rate)
causes relaxation (produces slower heart rate) when potassium channels open i.e. hyperpolarisation.

Question 27

non adrenergic non cholinergic @ sympathetic axon

Answer 27

3 phases of response: (contraction)
1. ATP binds to P2X purinoceptor (ligand gated cation channel) and causes calcium and sodium to enter the cell causing depolarisation and activation of another voltage gated calcium channel causing rapid phase of contraction

2. NE binds to alpha 1 adrenoceptor and Gq/PLC/IP3 cascade results in calcium release from ER/SR causing second phase of contraction
3. neuropeptide Y binds to Y1 receptor and causes slowest calcium increase producing the slowest phase of contraction.

Question 28

non adrenergic non cholinergic @parasympathetic axon

Answer 28

the parasympathetic axon releases:
ACh
NO
VIP (vasoactive intestinal peptide)

2 phases of response: (relaxation)
1. NO is released by the neuron into smooth muscle cell.
ACh is also released by the neuron which acts on M3 receptors on endothelial cell to produce NO also which will diffuse into smooth muscle cell.
both sources of NO activate guanylyl cyclase and raise cGMP in smooth muscle cell contributing to the first phase of relaxation.

2. neuropeptide VIP binds to receptors on smooth muscle cell causing an decrease in calcium also which contributes to the second (delayed) phase of relaxation.

Question 29

vasoactive intestinal peptide

Answer 29

is released along with ACh by sympathetic nerves to sweat glands and by parasympathetic nerves to enteric nervous system.

Question 30

cGMP inducing smooth muscle relaxtion

Answer 30

3 mechanisms:
1. inhibits calcium entry into the cell and decreases intracellular calcium concentrations

2. activated potassium channels which leads to hyperpolarisation and relaxation.
3. stimulates cGMP dependent protein kinase which activates myosin light chain phosphatase (an enzyme that dephosphorylates myosin light chains)

Question 31

peripheral nervous system

Answer 31

function: communication between CNS and rest of body

includes the ANS + SNS

31 spinal nerves carry info to and from spinal cord
12 cranial nerves carry info to and from the brain

Question 32

enteric nervous system

Answer 32

includes the myenteric and submucosal plexuses in the wall of GIT

myenteric plexus regulates motility
submucosal plexus regulates ion + water transport and secretion

Question 33

functions of the ANS

Answer 33

1. Maintenance of homeostasis (blood pressure)
2. integration of stress response
3. integration of visceral function (food digestion)

Question 34

overactive bladder case study

Answer 34

parasympathetic antagonist (muscarinic cholinergic antagonist) specifically M3 which mediates bladder contractions are useful.

sympathetic agonist at alpha 2 receptors to inhibit bladder contraction would have a small effect. sympathetic alpha 1 agonist would inhibit urination but the urge to urinate would still be present.