Intro to the ANS

Question 1

What would an increase in Arterial Baroreceptor firing lead to with regards to the ANS?

Answer 1

Stimulations of parasympathetic nerve; inhibits heart contraction

Inhibition of sympathetic innovation of heart and arteries to lower blood pressure and HR

Question 2

Describe the balance of the ANS in the eye at rest:

Answer 2

Dominated by the Parasympathetic at rest.

You need your smooth muscle to be partially constricted so it can change in both directions

Question 3

Where do parasympathetic nerves originate?

Answer 3

Cranial or Sacral regions

Question 4

What is the neurotransmitter used in the Parasympathetic Nervous system?

Answer 4

ACh

Question 5

What does the Preganglionic fibre of the SNS usually release?

Answer 5

ACh

Question 6

What dies the Post-ganglionic fibre of the SNS usually release?

Answer 6

Noradrenaline

Question 7

What post-ganglionic neurotransmitter may be secreted to innovate sweat glands?

Answer 7

ACh

Question 8

What is the function of the SNS and PNS in the eye?

Answer 8

SNS: Pupil dilation

PNS: Constriction of pupil, Contraction of ciliary muscle

Question 9

What is the balance of the ANS in the lungs at rest?

Answer 9

Dominated by the Parasympathetic;

There is a partial level of constriction so that it can both constrict further and dilate

Question 10

What is the dominant branch of the ANS in the liver and what does it control?

Answer 10

Sympathetic

Glycogenolysis + Gluconeogenesis

You want glucose to be available in a fight or flight situation so sympathetic discharge will stimulate an increase in glycogenolysis and gluconeogenesis.

Question 11

What are the effects of the SNS in the Kidneys, Bladder and Ureters?

Answer 11

Kidney: Increased renin secretion

Ureters and Bladder: Relaxes detrusor; constriction of trigone and sphincter

Question 12

What are the effects of the ANS in the heart, and which is dominant at rest?

Answer 12

SNS: Increased rate and contractility

PNS: Decreased rate and contractility

PNS dominant at rest

Question 13

Describe the ANS innovation of arteries and arterioles:

Answer 13

There is no parasympathetic innovation

The sympathetic is totally in control of the arterioles it controls constriction and dilation of the arterioles.

Question 14

Where do the post-ganglionic neurones in the sympathetic limb project from, and what does this mean for their organisation?

Answer 14

Sympathetic trunk

Very divergent (1:20) neurones so the sympathetic responses are coordinated and divergent; because of the sympathetic trunk, there is a mass discharge of the SNS.

Question 15

What are the consequences of the organisation and origins of the Parasympathetic trunk of the ANS?

Answer 15

Little divergence of neurones, so its effects tend to be discreet and localised.

Question 16

Recall the organisation of the ANS and the neurotransmitters it uses:

Answer 16

Question 17

What are the two types of ACh receptor?

Answer 17

Nicotinic and Muscarinic

Question 18

Where are nicotinic receptors found?

Answer 18

At ALL autonomic ganglia

Question 19

What is the speed of Nicotinic receptors and why?

Answer 19

Rapid as they transfer the stimulus from the pre-ganglionic to the post-ganglionic neurone.

Question 20

What type of receptor is the Nicotinic receptor?

Answer 20

Type 1 - Ionotropic

Question 21

How do nicotinic receptors work?

Answer 21

Acetylcholine binds to the receptor and opens an ion channel that allows sodium/calcium influx and allows transmission.

Question 22

Where are Muscarinic receptors found?

Answer 22

At any tissue that is innervated by a post-ganglionic parasympathetic fibre

Question 23

What type of receptors are Muscarinic receptors?

Answer 23

Type 2 - G-protein coupled

Question 24

What is the speed of a muscarinic receptor?

Answer 24

Much slower than nicotinic

Question 25

What are the sub-types of Muscarinic receptors?

Answer 25

• M1 – Neural (Forebrain – learning & memory)
• M2 – Cardiac (Brain – inhibitory autoreceptors)
• M3 – Exocrine & smooth muscle (Hypothalamus – food intake)

Question 26

Where are Adrenoceptors located?

Answer 26

Most effector organs innovated by post-ganglionic sympathetic fibres

Question 27

What type of receptors are adrenoceptors?

Answer 27

Type 2 - G-protein coupled

Question 28

What are the four types of Adrenoceptors?

Answer 28

• Alpha 1
• Alpha 2
• Beta 1
• Beta 2

Question 29

What are the functions of Alpha 1 and Beta 2 adrenoceptors, and what does this mean in terms of the ANS?

Answer 29

Alpha 1 Constricts

Beta 2 Dilates

• The SNS controls vasculature by itself

Question 30

Describe the synthesis of ACh:

Answer 30

Acetyl CoA + Choline (from diet)

with Choline Acetyl Transferase

(within presynaptic bulb)

Question 31

Describe the metabolism of ACh:

Answer 31

Acetylcholinesterase converts ACh in the synapse to Choline and acetate. The Choline then reenters the bulb to from more ACh.

Question 32

What three enzymes are involved the biosynthesis of Noradrenaline, and what do they convert?

Answer 32

Tyrosine hydroxylase: Tyrosine to DOPA

DOPA decarboxylase: DOPA to Dopamine

Dopamine beta-hydroxylase: Dopamine to NA

Question 33

What is the main difference betweent he metabolism of ACh and NA?

Answer 33

NA is not metabolised in the synapse!

Question 34

How is noradrenaline removed from the synapse?

Answer 34

Uptake-1: Back into neuronal tissue

Uptake-2: into extraneuronal tissue

Question 35

How is NA metabolised, and where?

Answer 35

In neuronal tissue: Monoamine oxidase (MAO)

In extraneuronal tissue: Catechol-O-Methyl Transferase (COMT)