Intro to ANS

Question 1

ANS is broken up into the ___ and ____

Answer 1

parasymp and symp NS

Question 2

For the most part, where do sympathetic pregang fibers leave the CNS? What about for the parasymps?

Answer 2

Thoracic and lumbar spinal nerves (thoracolumbar);

through cranial nerves, especially III, VII, IX, and X, and through the sacral nerves 2-4

Question 3

Symp ganglia tend to be ____ to spinal column; parasymp ganglia tend to be where?

Answer 3

closer; closer to or in target organs

Question 4

Normally there are ___ inputs to most organs. Give some examples

Answer 4

two;
heart: opposing
airways (smooth muscle): opposing
salivary glands: co-operating

Question 5

Most of symp pregang fibers terminate in ____ located in the ____ chains lying on either side of the spinal column; then ______ symp fibers run to ______ innervated;
exceptions?

Answer 5

ganglia; paraverterbal chains;
postgang; tissues;
think innervation of the adrenal medulla

Question 6

Majority of parasymp pregang fibers; exceptions?

Answer 6

terminate on ganglion cells distributed diffusely or in networks in walls of innervated organs;
e.g. submandibular gland

Question 7

For both the para and symp divisions, the ____ neurons release what to act on ____ ____ receptors?

Answer 7

pregang; Ach;

NN-type nicotinic receptors on postsynaptic membrane of postgang neuron

Question 8

For postgang parasymp neuron, list the neurotransmitter, receptor?

Answer 8

NT: ACh;
Receptor: muscarinic (metabotropic receptor of one of five subtypes, M1-M5)

Question 9

For postgang symp neurons, list NT and receptor type

Answer 9

NT: NE
REceptor: metabotropic adrenergic receptor of one of two major subtypes (a and b)

Question 10

Classical pathway of pregang and postgang neurons for parasymp, along with targets? Same with symp? Exceptions for the sympathetic NS?

Answer 10

1. Uses NN ACh and M ACh; cardiac and smooth muscle, gland cells, nerve terminals
2. NN ACh and NE (alpha and beta); cardiac and smooth muscle, gland cells, nerve terminals;
   A. sweat glands (NN ACh and M ACh)
   B. Renal vascular smooth muscle (NN ACh and D1)
   C. Chromaffin cells are specialized post-gang neurons (NN ACh, just epi and NE release)

Question 11

Symp system tends to have ____ output and is distributed widely to effectors throughout the body, whereas parasymp output is more _____. List ratios of the pre-postgang fibers for symp vs. parasymp?

Answer 11

diffuse; discrete; could be 1:20 vs. 1:1

Question 12

ACh main roles?

Answer 12

1. Primary transmitter at ANS ganglia, somatic neuromuscular junction, at parasympathetic postgang nerve endings
2. Excitatory transmitter to smooth muscle and secretory cells in ENS
3. Could be major neuron-to-neuron transmitter in ENS

Question 13

List steps of cholinergic transmission and what happens with the main player, Ach? Would drugs that block this pathway be useful?

Answer 13

1. ACh synthesized from acetyl-CoA and choline by choline acetyltransferase
2. ACh transported into vesicles for storage
3. ACh release triggered by AP causing Ca influx via Ca channels and fusion of vesicular and plasma membranes
4. ACh interacts with targets and broken down by acetylcholinesterase-mediated cleavage to choline and acetate which are RECYCLED;
   for the most part, NO because effects of drugs NOT SELECTIVE

Question 14

List steps of adrenergic transmission and what happens with main player, NE? Are drugs useful here?

Answer 14

1. NE synthesis with tyrosine hydroxylated to DOPA, DOPA decarboxylated to dopamine, and dopamine hydroxylated to NE inside vesicles
2. NE release similar to ACh
3. NE diffuses and is reuptaken to be cleared from synaptic cleft, but OUTSIDE CLEFT, can be metabolized and excreted;
   drugs blocking NE synthesis can be useful since they’ll block symp but not parasymp functions

Question 15

What are the two types of nicotinic receptors?

Answer 15

Neuronal (NN) and muscle (NM); bot pentameric, ACh-gated, non-selective cation channels

Question 16

For three of the muscarinic receptors, list their mechanism of action and what they help regulate? For the other two, what are possible mechs?

Answer 16

M1, M3, M5 –> Gq –> PLC activity –> increased DAG and IP3 (Ca) –> smooth muscle contraction by M3 receptors, neuroreg by M1;

M2, M4 –> Gi –> decreased AC activity –> decreased cAMP; or –> Gi –> activated K channels –> hyperpolarization (latter slows heartbeat and inhibits NT release by M2)

Question 17

How do the alpha adrenergic receptors work? Beta?

Answer 17

alpha 1 uses same mech as M1, M3, M5 and causes smooth muscle contraction; alpha 2 can use same mechs as M2, M4 to inhibit NT release

beta 1, 2, 3 –> Gs –> increased AC activity –> cAMP increased;
beta 1: increase in force and rate of contraction of heart
beta 2: smooth muscle relaxation
beta 3: lipolysis

Question 18

Sa node: list symp activity and parasymp activity?

Bronchiolar smooth muscle: list as above

Answer 18

SA node: symp accelerates and acts on beta 1 and 2; parasymp decelerates through M2;

bronchiolar: relaxes with beta 2; parasymp contracts through M3

Question 19

Give examples of integration

Answer 19

Central: Sensory carotid sinus baroreceptor fibers in CN IX influence symp and parasymp outflow from VASOMOTOR CENTER;
presynaptic regulation: autoreceptors are presyn receptors responding to transmitter substances released, like alpha 2 neg feedback from NE; or vagal fibers in myocardium synpasing on symp adrenergic nerve terminals and via M2 receptors to inhibit NE release
Postsyn reg: post-spike potential regulated by different receptors and transmitters, generating EPSP or IPSP

Question 20

What helps set a basal tone?

Answer 20

Symp and parasymp arms oppose each other