CVS 4 ANS and the CVS and Cellular and Molecular events

Question 1

How do neurones exert actions?

Answer 1

Via smooth muscle, viscera and secretory glands

Question 2

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

Answer 2

Pre-ganglionic- short

Post-gangionic- long

Question 3

Where are cell bodies in sympathetic outflow?

Answer 3

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

Question 4

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

Answer 4

Aceytl choline

Question 5

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

Answer 5

Nicotinic

Question 6

What neurotransmitter do post-ganglionic sympathetic neurones express?

Answer 6

noradrenaline

Question 7

What receptors do sympathetic effectors express?

Answer 7

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

Question 8

Which sympathetic postganglionic synapses are an exception being cholinergic?

Answer 8

perspiration and ejaculation pathways

Question 9

What does the ANS exert control over?

Answer 9

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

Question 10

What is the origin of the parasympathetic division

Answer 10

Craniosacral

Question 11

What is the relative length of parasympathetic neurones?

Answer 11

long pre-ganglionic

short post-ganglionic

Question 12

What neurotransmitter do pre-ganglionic parasympathetic neurones use?

Answer 12

Acetyl choline

Question 13

What receptors do post ganglionic parasympathetic neurones express?

Answer 13

nicotinic

Question 14

What neurotransmitter do postganglionic parasympathetic neurones us?

Answer 14

Acetyl choline

Question 15

What receptors to parasympathetic effectors express?

Answer 15

muscarinic, g protein coupled

Question 16

What type of receptors are present in the heart?

Answer 16

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

Question 17

What type of receptors are present in the airways?

Answer 17

Sympathetic- b2 adrenoreceptor- relax

Parasympathetic- M3- contract

Question 18

What type of receptors are in the pupil?

Answer 18

Sympathetic-a1- dilation

Parasympathetic- M3- contraction

Question 19

What type of receptors are in sweat glands?

Answer 19

Sympathetic- a1 localised secretion

m3-generalised secretion

Question 20

How do nicotinic receptors work?

Answer 20

They have an ion channel and allow sodium influx

Question 21

What are chromaffin cells?

Answer 21

Like special postganglionic sympathetic neurones that release adrenaline into the bloodstream

Question 22

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

Answer 22

10th cranial nerve- vagus nerve

Question 23

Where do parasympathetic fibres to heart synapse with postganglionic fibres?

Answer 23

epicardial surface or within walls of heart at SAN and AVN

Question 24

What do M2 receptors in the heart do?

Answer 24

decrease heart rate (-ve chronotropic effect)

decrease AVN conduction velocity

Question 25

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

Answer 25

sympathetic trunk

Question 26

Where do the sympathetic fibres innervate the heart?

Answer 26

SAN, AVN and myocardium

Question 27

What do the b1 receptors do in the heart?

Answer 27

positive chronotropic effect | positive inotropic effect

Question 28

How does depolarisation in the SA node occur?

Answer 28

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

Question 29

How does the ANS effect pacemaker potentials?

Answer 29

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

Question 30

How does noradrenaline increase force of contraction?

Answer 30

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

Question 31

What innervation do most blood vessels receive?

Answer 31

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

Question 32

How do changes in sympathetic output affect size or arteries?

Answer 32

decreased- vasodilation normal- vasomotor tone increased- vasoconstriction

Question 33

What blood vessels have B2 adrenoreceptors?

Answer 33

skeletal muscle myocardium liver

Question 34

What binds to B2 receptors in blood vessels and why?

Answer 34

circulating adrenaline as has higher affinity for b2 adrenoreceptors

Question 35

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

Answer 35

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

Question 36

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

Answer 36

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

Question 37

What effect do local metabolites have?

Answer 37

vasodilator effect. More important dilator effect than B2

Question 38

Give examples of local metabolites made by active tissues

Answer 38

adenosine, K+, H+, increase in pCO2

Question 39

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

Answer 39

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

Question 40

Where are baroreceptors located?

Answer 40

carotid sinus and aortic arch.

Question 41

What are baroreceptors sensitive to?

Answer 41

stretch by increased arterial pressure

Question 42

What is the resting membrane potential largely due to?

Answer 42

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

Question 43

How does excitation of cardiac myocytes cause contraction?

Answer 43

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

Question 44

Summarise the cardiac action potential in words

Answer 44

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

Question 45

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

Answer 45

If- funny current

Question 46

What channels are involved in the funny current?

Answer 46

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.

Question 47

What causes the upstroke in SAN potential?

Answer 47

voltage gated Ca2+ channel opening causing calcium influx

Question 48

What causes the downstroke in SAN potential?

Answer 48

Opening of voltage gated K+ channels causing K+ efflux

Question 49

Which part of heart depolarises fastest?

Answer 49

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

Question 50

What do desmosomes do?

Answer 50

Mechanically tether cadiac myocytes together

Question 51

What do gap junctions do?

Answer 51

Gap junctions permit ion movement and electrically couple cells

Question 52

Where is the nucleus in cardiac myocytes?

Answer 52

Centre of cell

Question 53

Will cardiac muscle contract in Ca2+ free solution?

Answer 53

No but skeletal muscle will

Question 54

How does cytosolic calcium increase?

Answer 54

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

Question 55

How does calcium effect sliding filament mechanism?

Answer 55

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

Question 56

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

Answer 56

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

Question 57

How does calcium affect contraction in vascular smooth muscle?

Answer 57

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

Question 58

What does phosphorylation by PKA do?

Answer 58

inhibits MLCK and so inhibits contraction