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CAM201 Pharmacology > ANS > Flashcards

Flashcards in ANS Deck (59)
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1

What are some of the major functions of the ANS?

- maintain homeostasis
- coordinate response to external stimuli (fight or flight)
- specific regulatory functions

2

what are some of the specific functions of the ANS?

- contraction and relaxation of the vascular and visceral smooth muscle
- CVS reflexes
- all exocrine and endocrine secretions
- energy metabolism, particularly in liver and skeletal muscle

3

What are the divisions of the ANS? what do they do?

SNS
- dominates during stress and emergency situations
- expenditure of energy
- increase in BGL, heart activity and BP

PNS
- conserve energy
- reduce HR
- increase GI and secretions

Enteric
- comprises the intrinsic nerve plexuses of GI tract

4

What are some of the responses of the SNS?

- increased HR
- vasoconstriction and increased BP
- skeletal muscle vasodilation and tremor
- pupil dilation, adjusting for far vision
- bronchodilation
- glycogenolysis, gluconeogenesi, lipolysis, thermogenesis
- sweating
- release of adrenaline

5

What are some responses of the PNS?

- decrease HR to resting
- digestion and secretion of waste products, increased Gi motility, gastric acid secretion, defecation, urination
- pupil constriction, accommodation for near vision, lacrimation

6

What are autonomic efferent pathways made of?

- Preganglionic neurons
- autonomic ganglia (contains nerve endings of preganglionioc and cell bodies of postganglionic)
- post ganglionic neurons

7

What are the main neurotransmitters in the ANS?

Acetylcholine and noradrenaline

8

How do cholinergic nerves function?

Using Acetycholine on:

ALL preganglioninc nerves

ALL post ganglionic nerves in the PNS

ACTS on nicotininc and muscurain

9

How do noradrenergic nerves function?

Use noradrenaline on:

most post ganglionic nerves in the SNS

10

Describe the neurons and their actions in the PNS

Preganglionic neurons release Ach which acts on nicotinic receptors in the cell body of the postganglionic neuron

Postganglionic neurons release AcH which acts on the muscarinic receptors on the effector tissue

11

What is cholinergic transmission?

Nerve transmission mediated by acetylcholine

12

What are the functions of acetylcholine in the CNS and PNS?

CNS: arousal, learning, memory and motor control

PNS:
- ANS: involuntary control of many structures
- enteric: involuntary control of the GIS
- somatic: voluntary control of skeletal muscles

13

Describe the steps in cholinergic transmission

1. Uptake of choline
2. Synthesis of AcH
3. Uptake of transmitter into synaptic vesicles
4. degradation of surplus AcH
5. depolarisation by propagated action potential
6. opening of voltage gated Ca2+ channels
7. release of transmitter by exocytosis
8. diffusion to postsynaptic membrane
9. binding to postsynaptic receptors
10. inactivation of ACh by ACHE
11. reuptake of transmitter or degradation products by nerve terminal
12. uptake of ACh by non-neuronal cells
13. Binding with presynaptic receptors

14

What is the nicotinic receptor?

a cholinergic receptor activated by acetycholine.

Ligand gated ion channel with two Ach binding sites.

15

What happens when ach binds to a nicotinic receptor?

the channel opens and Na+ enters, causing membrane depolarisation

16

Where are nicotinic receptors located and what do they do?

Skeletal muscle: cause contraction

Autonomic ganglia: allow transmission between pre and post ganglionic neurons

adrenal medulla: cause release of adrenaline

CNS: excitation

17

What is the muscarinic receptor?

A GPCR activated by acetylcholine. It passes on a message within the cell that generates a cellular response

18

What are the types of muscarinic receptors and their general functions?

M1: neural
M2: cardiac
M3: glandular/smooth muscle
M4/M5: mostly CNS

19

What is the role of M1 receptors and where are they located?

Found mainly on CNS and peripehral neurons and gastric parietal cells, M1 receptor activation has excitatory effects

20

What is the role of M2 receptors and where are they located?

Found mainly on the heart, M2 receptor activation has inhibitory effects

21

What is the role of M3 receptors and where are they located?

Located mainly on smooth muscle and glands, receptor activation has excitatory effects

22

What is the role of M4/M5 receptors and where are they located?

Mainly in the CNS. Function is not well understood

23

What is the mechanism of the M1 receptor? What is the result?

Gq: activates phospolipase C
= increased IP3 and DAG
= increased Ca2+

RESULT: neuronal excitation

24

What is the mechanism of the M2 receptor? What is the result?

Gi: inhibitis adenylate cyclase
= decreased cAMP
= decreases PKA
= decreased opening of Ca2+ channels

RESULT: reduce HR and contractility

25

What is the mechanism of the M3 receptor? What is the result?

Gq: activates phospholipase C
= increased IP3 and DAG
=increased Ca2+

RESULT: contraction of visceral smooth muscle. secretion of exocrine glands.

CAN cause relaxation of some smooth muscles, mainly vascular, via the release of nitric oxide from neighbouring endothelial cells (not innveravted by PNS but respond to circulating muscarinic agonists)

26

What are the PNS effects of M2 on the heart?

decreased rate and force of contraction

27

What are the PNS effects of M3 on the blood vessels?

generally none as there is no PNS innervation.

exception: erectile tissue which has mediated vasodilation via nitric oxide. dilated by exogenous muscarinic agonsts

28

PNS effects of M3 on smooth muscle (incl. bronchi, GI and bladder)?

contraction

29

PNS effects of M3 on the eye?

Contraction of the pupil = miosis

contraction of the ciliary muscle = near vision

30

PNS effects of M3 on the exocrine sweat glands

No PNS innervation, but muscarinic receptors respond to sympathetic innervation