CVS 4 ANS and the CVS and Cellular and Molecular events Flashcards Preview

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Flashcards in CVS 4 ANS and the CVS and Cellular and Molecular events Deck (58):
1

How do neurones exert actions?

Via smooth muscle, viscera and secretory glands

2

What are the relative nerve lengths in the sympathetic nervous system?

Pre-ganglionic- short
Post-gangionic- long

3

Where are cell bodies in sympathetic outflow?

Nerve fibres have cell bodies in all 12 thoracic sections and in the first 2 lumbar sections

4

What neurotransmitter do pre-ganglionic nerves in the sympathetic nervous system use?

Aceytl choline

5

What type of receptor do post-ganglionic sympathetic neurones express?

Nicotinic

6

What neurotransmitter do post-ganglionic sympathetic neurones express?

noradrenaline

7

What receptors do sympathetic effectors express?

adreno receptors: alpha 1 & 2, beta 1 & 2

8

Which sympathetic postganglionic synapses are an exception being cholinergic?

perspiration and ejaculation pathways

9

What does the ANS exert control over?

smooth muscle (vascular and visceral)
exocrine secretion
rate and force of contraction in the heart

10

What is the origin of the parasympathetic division

Craniosacral

11

What is the relative length of parasympathetic neurones?

long pre-ganglionic
short post-ganglionic

12

What neurotransmitter do pre-ganglionic parasympathetic neurones use?

Acetyl choline

13

What receptors do post ganglionic parasympathetic neurones express?

nicotinic

14

What neurotransmitter do postganglionic parasympathetic neurones us?

Acetyl choline

15

What receptors to parasympathetic effectors express?

muscarinic, g protein coupled

16

What type of receptors are present in the heart?

Sympathetic- b1 adrenoreceptor- increases rate/force of contraction
Parasympathetic- M2- decreases rate

17

What type of receptors are present in the airways?

Sympathetic- b2 adrenoreceptor- relax
Parasympathetic- M3- contract

18

What type of receptors are in the pupil?

Sympathetic-a1- dilation
Parasympathetic- M3- contraction

19

What type of receptors are in sweat glands?

Sympathetic- a1 localised secretion
m3-generalised secretion

20

How do nicotinic receptors work?

They have an ion channel and allow sodium influx

21

What are chromaffin cells?

Like special postganglionic sympathetic neurones that release adrenaline into the bloodstream

22

What is the origin of the pregangionic parasympathetic fibres to the heart?

10th cranial nerve- vagus nerve

23

Where do parasympathetic fibres to heart synapse with postganglionic fibres?

epicardial surface or within walls of heart at SAN and AVN

24

What do M2 receptors in the heart do?

decrease heart rate (-ve chronotropic effect)
decrease AVN conduction velocity

25

Where are the ganglions for the smpathetic input to the heart?

sympathetic trunk

26

Where do the sympathetic fibres innervate the heart?

SAN, AVN and myocardium

27

What do the b1 receptors do in the heart?

positive chronotropic effect
positive inotropic effect

28

How does depolarisation in the SA node occur?

slow depolarising pacemaker potential towards threshold, If- funny current, once above threshold causes opening of fast Ca2+ channels.

29

How does the ANS effect pacemaker potentials?

Sympathetic- increases slope gradient, g-protein receptors increasing cAMP speeding up pacemaker potential
Parasympathetic- decrease slope gradient, g protein receptors increasing K+ conductance and decrease cAMP

30

How does noradrenaline increase force of contraction?

acts of b1 receptors in myocardium, increasing cAMP
Ca2+ channels phosphorylated increasing Ca2+ entry during AP
increased uptake of Ca2+ in SR
increased sensitivity of contractile machinery to Ca2+
so increased force of contraction

31

What innervation do most blood vessels receive?

sympathetic (except some specialised tissue like erectile)
most arteries have a1 adrenoreceptors, coronary and skeletal muscle vasculature also have B2 receptors

32

How do changes in sympathetic output affect size or arteries?

decreased- vasodilation
normal- vasomotor tone
increased- vasoconstriction

33

What blood vessels have B2 adrenoreceptors?

skeletal muscle
myocardium
liver

34

What binds to B2 receptors in blood vessels and why?

circulating adrenaline as has higher affinity for b2 adrenoreceptors

35

What does activating B2 adrenoreceptors in blood vessels cause and how?

Vasodilation by increasing cAMP which opens a type of K channel which relaxes smooth muscle

36

What does activating a1 receptors in blood vessels do and how?

Vasoconstriction by increasing [Ca2+]in from stores and via influx of extracellular Ca2+ causing contraction of smooth muscle

37

What effect do local metabolites have?

vasodilator effect. More important dilator effect than B2

38

Give examples of local metabolites made by active tissues

adenosine, K+, H+, increase in pCO2

39

What two types of receptors are afferent nerves feeding back from the heart?

baroreceptors (high pressure side of system)
Atrial receptors (low pressure side of system)

40

Where are baroreceptors located?

carotid sinus and aortic arch.

41

What are baroreceptors sensitive to?

stretch by increased arterial pressure

42

What is the resting membrane potential largely due to?

K+ permeability of the cell membrane at rest due to open leak K+ channels and a small permeability to other ions

43

How does excitation of cardiac myocytes cause contraction?

action potential causes increase in cytosolic Ca2+ conc which allows actin and myosin interaction

44

Summarise the cardiac action potential in words

RMP due to background K+ channels
Upstroke due to opening of voltage gated Na+ channel- influx of Na+
Initial repolarisation due to transient outward K+ channels (V-gated ito)
Plateau due to opening to voltage gated Ca2+ channels (L-type)- Ca2+ influx that balances with K+ efflux
Repolarisation due to efflux of K+ through voltage gated K+ channels and others

45

What is the initial slope to threshold called in the pacemaker potential?

If- funny current

46

What channels are involved in the funny current?

HCN channels (Hyperpolarisation-activated Cyclic Nucleotide-gated channels) which allow sodium influx. These channels are activated by membrane potentials more negative than -50mv. The more negative, the more activation.

47

What causes the upstroke in SAN potential?

voltage gated Ca2+ channel opening causing calcium influx

48

What causes the downstroke in SAN potential?

Opening of voltage gated K+ channels causing K+ efflux

49

Which part of heart depolarises fastest?

SA node as sets the rhythm being pacemaker. Other parts of heart do also have automaticity but slower

50

What do desmosomes do?

Mechanically tether cadiac myocytes together

51

What do gap junctions do?

Gap junctions permit ion movement and electrically couple cells

52

Where is the nucleus in cardiac myocytes?

Centre of cell

53

Will cardiac muscle contract in Ca2+ free solution?

No but skeletal muscle will

54

How does cytosolic calcium increase?

Depolarisation opens L-type Ca2+ channels in t-tubule system
Localised Ca2+ entry opens Calcium-Induced Calcium Release (CICR) channels in the SR
25% entry across sarcolemma 75% released from SR

55

How does calcium effect sliding filament mechanism?

binds to troponin C, conformational change shifts tropomyosin to reveal mysosin binding site on actin filament

56

How is Ca2+ conc returned to resting levels in relaxation of cardiac myocytes?

Most pumped back into SR by SERCA
Some exits via cell membrane: Sarcolemmal Ca2+ATPase, Na+/Ca2+ exchanger

57

How does calcium affect contraction in vascular smooth muscle?

Ca2+ binds to calmodulin
Activates Myosin Light Chain Knase MLCK
Phosphorylates the myosin light chain to permit interaction with actin.
Relaxation as Ca2+ levels decline

58

What does phosphorylation by PKA do?

inhibits MLCK and so inhibits contraction