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ESA 2 SK > CVS 4 ANS and the CVS and Cellular and Molecular events > Flashcards

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

1
Q

How do neurones exert actions?

A

Via smooth muscle, viscera and secretory glands

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2
Q

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

A

Pre-ganglionic- short

Post-gangionic- long

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3
Q

Where are cell bodies in sympathetic outflow?

A

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

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4
Q

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

A

Aceytl choline

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5
Q

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

A

Nicotinic

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6
Q

What neurotransmitter do post-ganglionic sympathetic neurones express?

A

noradrenaline

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7
Q

What receptors do sympathetic effectors express?

A

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

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8
Q

Which sympathetic postganglionic synapses are an exception being cholinergic?

A

perspiration and ejaculation pathways

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9
Q

What does the ANS exert control over?

A

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

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10
Q

What is the origin of the parasympathetic division

A

Craniosacral

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11
Q

What is the relative length of parasympathetic neurones?

A

long pre-ganglionic

short post-ganglionic

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12
Q

What neurotransmitter do pre-ganglionic parasympathetic neurones use?

A

Acetyl choline

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13
Q

What receptors do post ganglionic parasympathetic neurones express?

A

nicotinic

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14
Q

What neurotransmitter do postganglionic parasympathetic neurones us?

A

Acetyl choline

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15
Q

What receptors to parasympathetic effectors express?

A

muscarinic, g protein coupled

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16
Q

What type of receptors are present in the heart?

A

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

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17
Q

What type of receptors are present in the airways?

A

Sympathetic- b2 adrenoreceptor- relax

Parasympathetic- M3- contract

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18
Q

What type of receptors are in the pupil?

A

Sympathetic-a1- dilation

Parasympathetic- M3- contraction

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19
Q

What type of receptors are in sweat glands?

A

Sympathetic- a1 localised secretion

m3-generalised secretion

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20
Q

How do nicotinic receptors work?

A

They have an ion channel and allow sodium influx

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21
Q

What are chromaffin cells?

A

Like special postganglionic sympathetic neurones that release adrenaline into the bloodstream

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22
Q

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

A

10th cranial nerve- vagus nerve

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23
Q

Where do parasympathetic fibres to heart synapse with postganglionic fibres?

A

epicardial surface or within walls of heart at SAN and AVN

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24
Q

What do M2 receptors in the heart do?

A

decrease heart rate (-ve chronotropic effect)

decrease AVN conduction velocity

25
Q

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

A

sympathetic trunk

26
Q

Where do the sympathetic fibres innervate the heart?

A

SAN, AVN and myocardium

27
Q

What do the b1 receptors do in the heart?

A

positive chronotropic effect

positive inotropic effect

28
Q

How does depolarisation in the SA node occur?

A

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

29
Q

How does the ANS effect pacemaker potentials?

A

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
Q

How does noradrenaline increase force of contraction?

A

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
Q

What innervation do most blood vessels receive?

A

sympathetic (except some specialised tissue like erectile)

most arteries have a1 adrenoreceptors, coronary and skeletal muscle vasculature also have B2 receptors

32
Q

How do changes in sympathetic output affect size or arteries?

A

decreased- vasodilation
normal- vasomotor tone
increased- vasoconstriction

33
Q

What blood vessels have B2 adrenoreceptors?

A

skeletal muscle
myocardium
liver

34
Q

What binds to B2 receptors in blood vessels and why?

A

circulating adrenaline as has higher affinity for b2 adrenoreceptors

35
Q

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

A

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

36
Q

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

A

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

37
Q

What effect do local metabolites have?

A

vasodilator effect. More important dilator effect than B2

38
Q

Give examples of local metabolites made by active tissues

A

adenosine, K+, H+, increase in pCO2

39
Q

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

A 
baroreceptors (high pressure side of system)
Atrial receptors (low pressure side of system)
40
Q

Where are baroreceptors located?

A

carotid sinus and aortic arch.

41
Q

What are baroreceptors sensitive to?

A

stretch by increased arterial pressure

42
Q

What is the resting membrane potential largely due to?

A

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

43
Q

How does excitation of cardiac myocytes cause contraction?

A

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

44
Q

Summarise the cardiac action potential in words

A

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
Q

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

A

If- funny current

46
Q

What channels are involved in the funny current?

A

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
Q

What causes the upstroke in SAN potential?

A

voltage gated Ca2+ channel opening causing calcium influx

48
Q

What causes the downstroke in SAN potential?

A

Opening of voltage gated K+ channels causing K+ efflux

49
Q

Which part of heart depolarises fastest?

A

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

50
Q

What do desmosomes do?

A

Mechanically tether cadiac myocytes together

51
Q

What do gap junctions do?

A

Gap junctions permit ion movement and electrically couple cells

52
Q

Where is the nucleus in cardiac myocytes?

A

Centre of cell

53
Q

Will cardiac muscle contract in Ca2+ free solution?

A

No but skeletal muscle will

54
Q

How does cytosolic calcium increase?

A

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
Q

How does calcium effect sliding filament mechanism?

A

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

56
Q

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

A

Most pumped back into SR by SERCA

Some exits via cell membrane: Sarcolemmal Ca2+ATPase, Na+/Ca2+ exchanger

57
Q

How does calcium affect contraction in vascular smooth muscle?

A

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
Q

What does phosphorylation by PKA do?

A

inhibits MLCK and so inhibits contraction

ESA 2 SK (35 decks)

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