Autonomic nervous system COPY

Question 1

What does ANS regulate?

Answer 1

Physiological functions -> homeostasis

eg heart rate, body temp, BP

Question 2

What does ANS exert control over?

Answer 2

Smooth muscle (peripheral resistance)
Exocrine secretion
Rate and force of contraction in heart (HR)

Question 3

2 divisions of ANS and what are these based on?

Answer 3

Sympathetic and Parasympathetic

Anatomical grounds

Question 4

Sympathetic ganglionic arrangement

Answer 4

Short preganglionic neurone (in sympathetic chain)

Long post ganglionic neurone to target tissue

Question 5

Parasympathetic ganglion organisation

Answer 5

Long preganglionic neurone

Short postganglionic neurone (within target tissue walls)

Question 6

What happens under stress?

Answer 6

Sympathetic system activity is increased

Question 7

What autonomic system is more dominant under normal body conditions (basal)?

Answer 7

PNS - dominates under normal circumstances

Question 8

What receptor does sympathetic system usually act on and how?

Answer 8

Adrenaline/noradrenaline released and acts on Adrenergic receptors (eg a1/b1 or b2)

Question 9

What receptor does parasympathetic system usually act on and how?

Answer 9

Ach binds to muscarinic receptors usually (eg M3/M2)

Question 10

What happens if you denervate a heart?

Answer 10

Still beats but faster

Vagal influence from parasympathetic usually slows down

Question 11

Parasympathetic supply to heart is via…

Answer 11

Preganglionic fibres of Vagus nerve (10th cranial nerve)

Question 12

Where do preganglionic fibres synapse to postganglionic fibres in parasympathetic system?

Answer 12

On epicardial surface/within heart (SA/AV NODE!)

Question 13

What do post ganglionic fibres release in parasympathetic heart stimulation and what does this bind to?

Answer 13

Ach

Binds to M2 receptors

Question 14

Effects of Ach binding to M2 receptor

Answer 14

Decrease HR (-ve chronotropic effect)
Decrease AV node conduction velocity

Question 15

Sympathetic input to heart

Answer 15

Postganglionic fibres travel from sympathetic chain

Question 16

What do the post ganglionic fibres of sympathetic system innervate?

Answer 16

SA NODE, AV NODE, MYOCARDIUM

different to parasympathetic as myocardium is included here

Question 17

How does the sympathetic input occur in heart?

Answer 17

Release of Noradrenaline

NA binds to B1 adrenoreceptors

Question 18

What effect does NA binding to B1 adrenoreceptors have on the heart?

Answer 18

Increase HR (+ve chronotropic effect)
Increase force of contraction (+ve inotropic effect)

Question 19

What sets the rhythm of the heart?

Answer 19

AP firing in the SA node (steadily depolarise towards threshold)

Question 20

Sympathetic effects on AP firing in SA node

Answer 20

Noradrenaline binds to B1 receptors (Gs receptors)
Increase cAMP
Speeds up pacemaker potential (If - funny current)

Question 21

Parasympathetic effects on AP firing SA node

Answer 21

Ach binds to M2 receptors (Gi receptors)
Decrease cAMP
Increase K+ conductance
decreases pacemaker potential slope

Question 22

How does noradrenaline increase force of contraction?

Answer 22

NA acts on B1 receptors
Increase cAMP
Activates PKA
= phosphorylation of Ca2+ channels

Question 23

What does phosphorylation of Ca2+ channels lead to?

Answer 23

Increase Ca2+ entry during plateau

Increase uptake of Ca2+ in SR (more available to release)

Question 24

what innervation type do most vessels receive?

Answer 24

Sympathetic

Question 25

What receptors are present in most vessels?

Answer 25

a1 adrenoreceptors

Question 26

What vessels have B2 receptors?

Answer 26

skeletal muscle myocardium liver

Question 27

What do you need to ensure you can have vasoconstriction and vasodilation?

Answer 27

Vasomotor tone | Already some constriction to allow vasodilation if needed

Question 28

How does sympathetic output effect vessels?

Answer 28

Increased output = vasoconstriction | decreased output = vasodilation

Question 29

How does circulating adrenaline affect vessels?

Answer 29

High affinity for b2 receptors than for a1 | At high levels adrenaline can affect a1

Question 30

What binds to what to allow for vasoconstriction/vasodilation?

Answer 30

More Noradrenaline will bind to a1 | adrenaline binds to b2 but a1 in high levels

Question 31

What effect does activating b2 adrenoreceptors have?

Answer 31

Vasodilation

Question 32

What effect does activating a1 adrenoreceptors have?

Answer 32

Vasoconstriction

Question 33

How does vasodilation occur from activating b2 receptor?

Answer 33

``` Increase cAMP PKA Open K+ channels inhibits MLCK (cannot phosphorylate MLC) Relaxation of smooth muscle ```

Question 34

How does vasoconstriction occur from activation of a1 receptor?

Answer 34

IP3 production Increase in Ca2+ from SR stores and influx = Contraction (DAG inhibits MLC phosphatase so stays phosphorylated)

Question 35

What has the largest impact on ensuring adequate perfusion?

Answer 35

``` Metabolite concentration (eg adenosine, H+) STRONG vasodilator effect ```

Question 36

How are changes in system communicated to brain?

Answer 36

``` Afferent nerves (towards brain) eg baroreceptors or atrial receptors ``` this then alters efferent pathway

Question 37

What are baroreceptors?

Answer 37

``` Stretch receptors (increased arterial pressure = stretch) ```

Question 38

Where are baroreceptors found?

Answer 38

Carotid sinus and aortic arch

Question 39

What happens if baroreceptors detect stretch of blood vessels?

Answer 39

Stretch = high BP Fire more action potentials towards medulla Inhibit SNS, Activate PNS =Bradycardia and Vasodilation

Question 40

What is baroreceptor for?

Answer 40

Maintaining blood pressure over SHORT time | moment to moment

Question 41

What happens to baroreceptors if there is continuous hypertension?

Answer 41

Reset to 'new normal' | reset to higher levels

Question 42

drugs acting on ANS

Answer 42

Sympathomimetics (a and b receptor agonists) Adrenoreceptor antagonists Cholinergics (muscarinic antagonists/agonists)

Question 43

Sympathomimetics eg

Answer 43

Adrenaline Dobutamine salbutamol

Question 44

Adrenaline function

Answer 44

Restore function and support circulation in cardiac arrest Anaphylactic shock (you get widespread vasodilation when this occurs, HIGH LEVELS of adrenaline stimulates a1 receptor)

Question 45

Dobutamine

Answer 45

``` B1 agonist cardiogenic shock (pump failure) ```

Question 46

Salbutamol

Answer 46

``` b2 agonist treats asthma (relaxes bronchioles0 ```

Question 47

a adrenoreceptor antagonists

Answer 47

Anti-hypertensive eg a1 antagonist PRAZOSIN Inhibits NA action on a1 receptors = vasodilation

Question 48

B adrenoreceptor antagonists example

Answer 48

Propranolol = non selective slows HR reduce force of contraction but BRONCHOCONSTRICTION

Question 49

problem with propranolol

Answer 49

non selective NOT GOOD for Asthmatic patient (causes bronchoconstriction from b2) (use selective b1 like atenolol)