ANS

Question 1

What is the anatomical classification of the ANS (2) ?

Answer 1

preganglionic origin

parasympathetic nervous system cranial and sacral

sympathetic nervous system thoracic and lumbar

Question 2

What is the physiological classification of ANS (2)?

Answer 2

Transmitter released from the nerve terminal.

cholinergic releasing acetylcholine (Ach)

adrenergic releasing Norepinephrine (NE) or Epinephrine (E)

Question 3

What are the types of cholinoceptors (2)?

Answer 3

Nicotinic or muscarinic (both activated by Ach)

Question 4

What are nicotinic receptors (2)?

Answer 4

muscle nicotinic (Nm) - activates (@ nm junction of somatic nerves)

Neuronal nicotininc (Nn) - activates autonomic ganglia (PSNS or SNS).

Question 5

What are muscarinic receptors?

Answer 5

Present in effector organs innervated by postganglionic PSNS nerves.

Activated by muscarine (or bethanechol) or Ach

Question 6

What are they types of adrenoreceptors and what activates them?

Answer 6

Alpha (α1 or α2) and Beta (β1, β2)

All activated by EP

NE activates all except β2.

Question 7

What do parasympathetic and sympathetic nerves do (2) ?

Answer 7

PSNS –> Ach

SNS –> NE

(adrenal medulla - SNS postganglionic cell releases 85% E and 15 % NE)

Question 8

What’s the deal with somatic nerves?

Answer 8

They don’t have ganglion and release ACH at neuromuscular junction (synapse bw nerve and skeletal muscle).

Question 9

Where is Ach synthesized and stored?

Answer 9

ACh is synthesized in cholinergic nerve terminal and transported and stored in vesicles.

Question 10

How is ACh released?

Answer 10

An action potential along nerve fiber causes Ca++ influx, fusion of vesicular and cell membrane, and release of ACh (exocytosis).

Question 11

What is needed for SNS activation?

Answer 11

NE, E postganglionic VIA sympathetic nerves and/or adrenal medulla with the presence of selective adrenoceptors at target tissue.

Question 12

What is needed for PSNS activation?

Answer 12

Ach at cholinergic nerve terminals and presence of PSNS nerves, release of Ach, and receptors (nicotinic and muscarinic).

Question 13

Describe the mechanism of PSNS?

Answer 13

Ach released from PSNS nerves can activate M receptors

on SA and AV nodes of heart (reduce HR),
to narrow airway
increase GI tract.

Does not affect vascular tone because muscarinic receptors are present in blood vessels but not innervated with PSNS. But Ach injected in IV can dilate blood vessels and reduce blood pressure, which leads to release of nitric oxide NO cause vasodilation.

Question 14

What are the directly acting cholinoceptor agonists (4)?

Answer 14

NON-SELECTIVE, poor lipid solubility, not used often clinically

1) ACh (nicotinic and muscarinic),

2) nicotinic receptor agonists (nicotine)

3) muscarinic receptor agonist muscarine (an alkaloid)

4) bethanechol (a synthetic agent) - increase muscle tone in urinary retention and gastrointestinal hypotonia after surgery

Question 15

What are indirectly cholinoceptor agonists (2) ?

Answer 15

Anticholinesterase/ Cholinesterase inhibitors - inhibit cholinesterase, therefore amplify ACh.

Clinically used cholinesterase inhibitors include reversible:

1) neostigmine, a hydrophilic compound which is poorly absorbed, and does not penetrate the CNS and

2) physostigmine, which is lipophilic and well absorbed from all sites.

Both drugs can be used to increase the tone of the GI tract (in GI hypotonia) and urinary bladder (in urinary retention).

In contrast, Sarin (chemical weapon) and Malathion (insecticide) are
“irreversible” cholinesterase inhibitors which form strong covalent bonds with cholinesterase.

Question 16

What can cholinergic blockers block (3)?

Answer 16

1) muscarinic (M atropine (reversable blockade of M receptors) & scopolamine (prevent motion sickness))

2) neuronal nicotinic (Nn, hexamethonium)

3) muscle nicotinic (Nm; curare, d-Tubocuranine) receptors.

Question 17

What are the clinical uses of antimuscarinics (6)?

Answer 17

Block actions of acetylcholine (ACh) on muscarinic (M) receptors (think blocking rest and digest)

1.Motion sickness (block ACh stimulation of M receptors in inner ear).

2.Eye: over constricted (miosis) (block ACh-induced miosis/pupil constriction).

3.Asthma (block ACh-induced bronchoconstriction).

4.Irritable bowel (inhibit ACh stimulation of bowel movement).

5.Urinary urgency (block ACh stimulation in overactive bladder).

6.Anticholinesterase poisoning (block CNS and peripheral muscarinic effects of ACh).

Question 18

What are the clinical uses of the antinicotinics?

Answer 18

AKA Nicotinic receptor antagonists

1) Ganglionic blockers (Nn) - inhibit SNS/PSNS rarely used except in emergency hyptertension

2) Neuromuscular blockers (Nm) are used to relax skeletal muscles in preperation of surgery (ex. Tubocurarine)

Question 19

Where is NE synthesized and stored?

Answer 19

Synthesized from dopamine in the adrenergic nerve terminal and is transported to storage vesicle.

Question 19

How is NE released?

Answer 19

Propagation of action potential along nerve causes Ca++ influx, fusion of vesicular and cell membrane, and release of NE or dopamine (exocytosis).

Question 20

What happens to dopamine and NE when released (3)?

Answer 20

1) Released dopamine can activate dopamine receptors

1) NE can activate adrenoceptors (alpha or beta) at effector organs to make response.

2) Released NE is primarily terminated by the NET (NE transporter) which uptakes NE and/or dopamine back into the nerve terminals.

3) NE that diffuses away from the nerve terminal can be degraded enzymatically at the postsynaptic cell or in organs.

Question 21

What are the adrenoreceptor agonists? (5)

Answer 21

Phenylephrine (α1) can cause mydriasis (contraction of radial muscle of the iris), vasoconstriction (constriction of arterioles and veins), and constriction of gastrointestinal (GI) and urinary sphincters. (selective)

Salbutamol (or terbutaline) can activate β2–adrenoceptors [bronchodilation, vasodilation of arterioles, relax uterus, increase glucose output, decrease GI and genitourinary (GU) activity]. (selective)

Isoproterenol can activate β1 (increase cardiac rate and contractility) and β2 (see above) adrenoceptors. (selective)

Epinephrine can activate all α1, α2, β1 and β2. (non selective)

NE all except β2. (Less selective)

Question 22

What adrenergic neuron blockers reduce SNS activity (2)?

Answer 22

Clonidine and α-Methyl-dopa (hypertension in preg)

Question 23

Give an overview of ACh/NE release and it’s pathway (4)?

Answer 23

1) ACh released from somatic nerve activate Nm in sketelal muscle.
2) Ach relaesed fome SNS/PSNS preganglionic nerve to activate Nn recoptors in ganglion - activates postganglionic nerve.
3) Ach relased from PSNS postganglionic nerve to tissue (heart, smooth muscle) to activate M
4) NE released from SNS postganglionic nerve to activate alpha or beta adrenoceptors.

Question 24

bethanechol

Answer 24

synthetic cholinoceptor agonist - increase urinary muscle tone and GI hypotnia post-surgery

Question 25

neostigmine

Answer 25

Indirect cholinoceptor agonist -doesn’t peneterate CNS -increase urinary muscle tone and GI hypotnia post-surgery

Question 26

physostigmine

Answer 26

Indirect cholinoceptor agonist -lipophilic/well asborbed
increase urinary muscle tone and GI hypotnia post-surgery

Question 27

atropine

Answer 27

M blocker

Question 28

scopolamine

Answer 28

M blocker - prevents motion sickness

Question 29

hexamethonium

Answer 29

Nn blocker

Question 30

d-Tubocuranine

Answer 30

Nm blocker

Question 31

Phenylephrine

Answer 31

adrenoreceptor alpha 1 agonist (think SNS symptoms)

Question 32

Salbutamol

Answer 32

adrenoreceptor beta 2 agonist- think SNS symptoms + relax utureus, increase glucose output

Question 33

Isoproterenol

Answer 33

adrenoreceptor agonist
Beta 1 - increase heart rate
Beta 2

Question 34

A1 adrenoreceptor agonists

Answer 34

contraction (blood vessels)

Question 35

A2 adrenoreceptor agonists

Answer 35

decrease SNS (decrease NE/E)

Question 36

B1 adrenoreceptor agonists

Answer 36

increase cardiac (heart rate and contractility);

Question 37

B2 adrenoreceptor agonists

Answer 37

relaxation (e.g., uterus, bronchial, blood vessels);

Question 38

Clonidine and α-Methyl-dopa

Answer 38

Adrengic neuron blockers used for hypertension in preg