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Cardiovascular system > Lecture 10- Autonomic cardiac control > Flashcards

Lecture 10- Autonomic cardiac control Flashcards

1
Q

The ANS has important for regulating many physiological functions inc…

A

HR, BP, body temp etc (homeostasis)

Fight or flight response (stress response)

*Outside voluntary control*

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2
Q

ANS control over specific tissue

A

Smooth muscle

Exocrine secretion

Rate and force of contraction in the heart

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3
Q

Two divisions (defined by their origin- anatomical grounds)

A

Parasympathetic- craniosacral origin

Sympathetic- thoracolumbar origin

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4
Q

sympathetic neurones

A

preganglionic within CNS (short), postganglionic innervates target tissue (long)

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5
Q

parasympathetic neurones

A

preganglionic (long), post ganglionic neurone are within the target tissue (short)

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6
Q

function of the ANS

A

Where parasympathetic and sympathetic divisions both innervate a tissue they often have opposite effects

  • Sympathetic activity is increased under stress
  • Parasympathetic system is more dominant under basal conditions
    • Both work together to maintain balance
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7
Q

sympathetic effect and receptor: pupil of the eye

A

dilation (contracts raidal muscle)

alpha1

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8
Q

sympathetic effect and receptor: airways of lungs

A

relax

Beta1

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9
Q

sympathetic effect and receptor: heart

A

increase rate (chronotropy) and force of contraction (inotropy)

Beta1

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10
Q

sympathetic effect and receptor: sweatglands

A

localised secretion (e.g. palms)–> alpha1

generalised secretion–> M3

*Sweat glands- one of the only sympathetic receptors that use ACh*

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11
Q

parasympathetic effect and receptor: pupil of eye

A

contraction (contracts sphincter muscle)

M3

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12
Q

parasympathetic effect and receptor: airways of lungs

A

contracts

M3

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13
Q

parasympathetic effect and receptor: heart

A

decrease rate

M2

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14
Q

parasympathetic effect and receptor: sweat glands

A

no effeect

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15
Q

ANS control of CVS

A

Heart rate

Force of contraction of heart

Peripheral resistance of blood vessels

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16
Q

what does thr ANS not do to the CVS

A

Initiate electrical activity in the heart

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17
Q

if the heart was dennervated

A

Dennervated heart still beats, but at a faster rate

At rest the heart is normally under vagal (parasympathetic) influence

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18
Q

(1) Parasympathetic input of the heart

A
  • Preganglionic fibres- 10th X cranial nerve VAGUS
  • Synapse with postganglionic cells on epicardial surface or within the walls of the heart at the SA and AV node
    • Slow conduction at both SA and AV
  • Post ganglionic release ACh
    • Acts on M2 receptors
    • Decrease heart rate (-ve chronotropic effect)
    • Decrease AV node conduction velocity
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19
Q

(2) Sympathetic input to the heart

A
  • Post ganglionic fibres from the sympathetic trunk
  • Innervates SA, AV node and myocardium
    • Release noradrenaline
  • Acts mainly on B1 adrenoreceptors
    • Increases heart rate (+ve chronotropic effect)
    • And increases forces of contraction (+ve inotropic effect)
    • B2 and B3 also present in heart, but the main effect is mediated by B1 receptors
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20
Q

autonomic NS input into the heart diagram

A
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21
Q

The pacemaker of the heart

A

Cells in the SAN steadily depolarise towards threshold

  • Slow depolarising pacemaker potential
  • Turning on of a slow Na+ conductance-HCN (If-funny current)
  • Opening of ca2+ channels
  • AP firing in the SA node set the rhythm of the heart
22
Q

Effects of ANS on the pacemaker potential (chronotropic): sympathetic

A

effects mediated by b1 receptor

GPCR

  1. increase cAMP
  2. speed up pacemaker potential

HCN – cyclic nucleotide gated

–>Increase cAMP, increase If current

23
Q

Effects of ANS on the pacemaker potential: parasympathetic

A

effects mediated by M2 receptors

GPCR

  1. increased K+ conductance
  2. decrease CAMP
24
Q

How does NA increase force of contraction? (inotropic)

A
  • NA acting on B1 receptors in myocardium causes an increase in cAMP –> activates PKA (GalphaS)
    • Phosphorylation of Ca2+ channels increase Ca2+ entry during the plateau of the AP
    • Increase uptake of Ca2+ in SR
    • Leads to increased force of contraction
25
ANS effects on vasculature
Most vessels receive sympathetic innervation (bar erectile tissue which does have some parasympathetic innervation)
26
which receptors do most arteries and veins have
* Most arteries and veins have alpha1-adrenoreceptors * Coronary and skeletal muscle vasculature also have B2- receptors
27
Vasomotor tone allows for dilation to occur
Have to have some basal level of vascular tone to make sure the vessels have somewhere to dilate i. e. the less sympathetic outcome --\> vasodilation e. g. to reduce BP--\> dilate vessels
28
which blood vessels have B2 adrenoreceptors as well as alpha1 adrenoreceptors
e.g. skeletal muscle, myocardium and liver
29
why do skeletal muscle, myocardium and the liver have B2 and alpha1 adrenoreceptors
* NA released from SNS will bind to alpha 1 will causes vasoconstriction * Circulating adrenaline preferentially acts on B2 receptors (will also act on alpha1 as conc gets higher) * **At physiological conc will activate B2--\> vasodilation** * **If you increase conc of circ adrenaline, then at higher conc it will work on alpha1 --\> causing vasoconstriction**
30
Effects of B2 adrenoreceptors on vascular smooth muscle
Activating B2 adrenoreceptors causes vasodilation 1. Increases cAMP 2. Activates PKA 3. opens potassium channels and inhibits MLCK 4. relaxation of smooth muscle
31
Effects of alpha1 adrenoreceptors on vascular smooth muscle
Activating alpha1 adrenoreceptors causes vasoconstriction 1. Stimulates IP3 production 2. Increase in (Calcium) in from stores and via influx of extracellular Ca2+ 3. contraction of smooth muscle
32
local metabolites which cause vasodilation
* Adenosine * K+ * H+ * Increased PCO2 * Locale increase in metabolites have strong vasodilator effects
33
local metabolists are more important for ensuring
adequate perfusion of skeletal and coronary muscle than activation of B2 receptors
34
Changes in the state of the cardiovascular system are communicated to the brain via
afferent nerves: * Baroreceptors (high pressure side of system) * Atrial receptors (low pressure side of the system) will alter activity of efferent nerve
35
baroreceptor nerve endings found in.... and are sensitive to ....
carotid sinus and aortic arch sensitive to stretch
36
baroreceptors during an increased BP
1. Increased arterial pressure stretches these receptors 2. Afferent nerves report back to medullary centre 3. Parasympathetic nervous system activated * Vasodilation of vessels * Reduced inotropy of the heart
37
baroreceptor reflex
* Important for maintaining blood pressure over short term * It compensates for moment to moment changes in aBP * **However Baroreceptors can re-set to higher levels with persistent increases in blood pressure**
38
drugs which act on the ANS
1. Sympathomimetics * Alpha-adrenoreceptors agonists * B-adrenoreceptor agonists 2. Adrenoreceptor antagonists 3. Cholinergics * Muscarinic agonists and antagonists
39
name some sympathomimetics
adrenaline, dobutamine and salbutamol
40
Admin of adrenaline
to restore function in cardiac arrest
41
dobutamine is a
B1 agonist that may be given in cardiogenic shock (pump failure)
42
adrenaline also administed for
anaphylactic shock
43
salbutamol is a
B2 agonist- treatment for asthma
44
adrenoreceptor agonists
Alpha-adrenoreceptors antagonists B-adrenoreceptor antagonists
45
Alpha-adrenoreceptors antagonists
Alpha 1 antagonist e.g. prazosin * Anti-hypertensive agent * Inhibits NA action on vascular smooth muscle alpha 1 receptors- vasodilation
46
B-adrenoreceptor antagonists
propanol atenolol
47
Propranolol
* Non-selective B1/B2 antagonists * Slows heart rate and reduces force of contraction (B1) but also acts on bronchial smooth muscle (B2)- bronchoconstriction
48
Atenolol
Selective B1 (cardio-selective)- less risk of bronchoconstriction
49
cholinergics
muscarininc agonists muscarinic antagonists
50
muscarininc agonists
e. g. pilocarpine- used in treatment of glaucoma * activates constrictor pupillae muscle
51
Muscarinic antagonists
e.g. atropine or tropicamide * Increases heart rate, bronchial dilation * Used to dilate pupils for examination of the eye

Cardiovascular system (30 decks)

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