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nuero > control of heart function > Flashcards

control of heart function Flashcards

1
Q

what are the main anatomical features of the heart

A

Muscle cells (cardio-myocytes)
Specialised electrical cells
Vessels

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2
Q

describe the muscle cells function

A

can contract and relax in response to electrical stimuli. Essential for pumping blood around the body

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3
Q

function of specialised electrical cells:

A

cells that create spontaneous currents and those that transmit currents exist within the heart. Essential for regulating contraction of the cardio-myocytes

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4
Q

Vessels

A

he major blood vessels are responsible for transporting blood in and out of the heart, whilst the coronary blood vessels are responsible for supplying blood to the heart

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5
Q

what are the most prominent cells in controlling heart function

A

specialised electrical cells

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6
Q

what are the nodes in the heart

A

sa node

av node

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7
Q

what is the sa node function

A

Pacemaker of the heart: 60-100 bpm

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8
Q

where is it

A

Junction of crista terminalis; upper wall of right atrium & opening of superior vena cava

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9
Q

function of av node

A

Has pacemaker activity: slow calcium mediated action potential

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10
Q

where

A

Triangle of Koch at base of right atrium

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11
Q

what are the tracts in the heart

A

Bundles of His & bundle branches

Purkinje fibres

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12
Q

what are the bundles of his

A

Specialised myocytes. AV node: His bundle  branches at intraventricular septum  apex

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13
Q

what are purkinje fibres

A

Specialised conducting fibres

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14
Q

function of bundle of his

A

serves to transmit the electrical impulse from the AV node to the Purkinje fibres of the ventricles.

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15
Q

function of purkinje

A

purkinje fibers allow the heart’s conduction system to create synchronized contractions of its ventricles, and are essential for maintaining a consistent heart rhythm

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16
Q

how many phases in nodal ap

A

3

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17
Q

what are they

A

0 3 4

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18
Q

what is phase 0

A

upstroke (depolarisation

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19
Q

what is it caused by

A

ca2+ influx

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20
Q

what is phase 3

A

repolarisation

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21
Q

what is it caused by

A

k+ efflux

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22
Q

what is phase 4

A

pre potential

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23
Q

what is the nodal cell resting potential

A

Nodal cells do not have a resting membrane potential - only a pre-potential due to Na+ influx through a ‘funny’ channel
continous deploirasation and repolarisation

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24
Q

what causes phase 4

A

sodium influx through funny channel (GOOGLE GRAPH TO SEE SHAPE)

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25
Q

what does the duration of Cardiac muscle action potential control

A

contraction of the heart

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26
Q

what is longer cardiac muscle ap or nodal ap

A

cardial ap is ~200x longer

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27
Q

what are charactiristics of an effective pump

A

long slow contraction

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28
Q

how many phases

A

5

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29
Q

what are they

A

0 1 2 3 4

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30
Q

what is the Absolute refractory period (ARP)

A

= time during which no AP can be initiated regardless of stimulus intensity

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31
Q

what si Relative refractory period (RRP)

A

period after ARP where an AP can be elicited but only with larger stimulus strength

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32
Q

what is phase 0

A

upstroke/depolarisation

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33
Q

phase 1

A

early repolarization

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34
Q

phase 2

A

plateau (still depolarised but starting to decrease)

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35
Q

phase 3

A

repolarisation

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36
Q

phase 4

A

resting membrane potential

Google to see graph shape

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37
Q

what causes phase 0

A

sodium influx (remember they are ions)

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38
Q

what causes phase 1

A

potassium efflux

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39
Q

causes phase 2

A

calcium influx

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40
Q

phase 3 and 4

A

potassium efflux

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41
Q

what 3 major organs control heart function

A

The brain/central nervous system

The kidneys

The blood vessels

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42
Q

function of the brain/cns

A

can effect immediate changes through nerve activity or slower changes through hormonal activity

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43
Q

The kidneys function in controlling the heart

A

the heart and kidneys share a bi-directional regulatory relationship usually through indirect mechanisms

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44
Q

how do blood vessels control heart function

A

by regulating the amount of blood that goes to and from the heart the blood vessels are able to influence cardiac activity.

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45
Q

what are subbranches of the autonomic nervous system

A

para

and symp

46
Q

function of para

A

rest and digest

47
Q

effect of para on the heart

A

decrease heart rate (HR) – decreases the slope of phase 4

48
Q

function of sympathetic nervous system

A

‘fight or flight’

49
Q

effect of symp on the heart

A 
increase HR (chronotropy) – increases the slope of phase 4
increase force of contraction (inotropy) – increases Ca2+ dynamics
50
Q

what nerve to heart

A

vagus

51
Q

how does para decraese heart rate

A

effects pre potential in nodal cell

52
Q

what does phase 4 determine

A

how quickly it can contract again

53
Q

where do para nerves originate from

A

cranial part of spinal cord

sacral part of spinal cord

54
Q

what nerves do they have

A

pre and post ganglionic fibres

55
Q

what neurotransmitter do they release

A

Ach

56
Q

what do para nerves achieve

A

controlling heart rate

57
Q

where do symp originate from

A

thoracic and lumbar

58
Q

what type of nerve

A

pre and post

59
Q

what strcuture do symp nerves tend to synapse on

A

synpathetic chain (paraveterbral ganglia)

60
Q

what neurotrasnmitter do they release at pre

A

Ach

61
Q

and post

A

Can be nora a

62
Q

so what does symp control

A

circulation

63
Q

where is the vasomotor centre located

A

located bilaterally in reticular substance of medulla & lower third of pons

64
Q

what 3 areas are they composed of

A

pressor area
depressor area
Cardio-regulatory inhibitory area

65
Q

what is the pressor area aka

A

vasoconstrictor area

66
Q

depressor aka

A

vasodilator

67
Q

what is the vmc controlled by

A

Many higher centers of the brain such as the hypothalamus can exert powerful excitatory or inhibitory effects on the VMC.

68
Q

what 2 portions of the vmc control the heart

A

lateral and medial

69
Q

how does the lateral portion of the vmc control the heart

A

Lateral portions of VMC controls heart activity by influencing heart rate and contractility
dont really need to know

70
Q

medial

A

Medial portion of VMC transmits signals via vagus nerve to heart that tend to decrease heart rate.
dont really need to know

71
Q

distally

A

Transmits impulses distally through spinal cord to almost all blood vessels

72
Q

how does para innervate

A 
ACh binds to m2 muscarinic receptor on cm of sa node 
bind to  (inhibotory ]) g protien, inhibits of adenyl cyclase
73
Q

and symp

A

releases nora acts on beta 1 receptor
stimulate adenyl cyclase
increase level of protien kinsae

74
Q

what will para do to heart

A

decrease heart rate

75
Q

symp

A

increase

76
Q

what would happen if you cut para

A

heart rate increase q

77
Q

cut symp

A

heart rate decrease

78
Q

symp nerve innervating kidney

A

less glomerular filtration
less na+ excretion
increase blood volume (aldosterone)

79
Q

what is the blood volume detected by

A

Detected by venous volume receptors

80
Q

what else does symp innervation do

A

more renin secreation
more angiotensin 2
causing vasoconstriction
high blood pressure

81
Q

what is blood pressure detected by

A

detected by arterial baroreceptors

82
Q

how do kidney affect heart

A

affect blood volume and vlood pressure

83
Q

how does kidney increase blood volume

A

less na+ excretion

84
Q

hoe does the kidney affect blood pressure

A

increase secretion of ang II

increasing blood pressure

85
Q

angiotensin 2 also secretes what

A

aldosterone

86
Q

what do. the symp nerve fibre innervate

A

afferent and efferent atrerioles of glomerulus

87
Q

what affect on afferent arterioles

A

symp inneravtion causes vasoconstriction by activation of a1- adrenoceptor

88
Q

what is the nuerotransmitter

A

noradrelaline

89
Q

what does that cause

A

decrease glomerular filtration rate

less na filtered

90
Q

function of juxtaglomerlular cells

A

the site of synthesis, storage & release of renin

91
Q

which recpetor causes renin secretion

A

b1 adrenoceptor
increases aldesterone
increases blood volume

92
Q

define inotropic

A

increases contractility

93
Q

chronotropic

A

increases heart rate

94
Q

What effect will activation of renal arteriole alpha-1 receptor eventually have on the heart?

A

Increased chronotropy & inotropy

95
Q

what happens when there is a decrease in heart filling

A

less baroreceptor firing
more symp nerve activity
increases heart rate

96
Q

what happens in distention

A

higher barorecpetor firing

less sns activity

97
Q

what is decrease in fillling caused by

A

less blood coming back to the heart

98
Q

distention.

A

more blood coming back to the heart

99
Q

what controls how much blood comes back to the heart

A

kidney and blood vessels

100
Q

what are large pulmonary vessels sensitive to

A

Volume sensors (also atria & right ventricle): send signals though glossopharyngeal & vagus nerves

101
Q

what are Arterial circuit
Aortic arch, carotid sinus & afferent arterioles of kidneys
sensitive to

A

Pressure sensors: send signals though glossopharyngeal & vagus nerves

102
Q

when there is a decrease in pressure

A

less barorecptor firing

higher sns

103
Q

increase in pressure

A

high barorecpetor firing

less sns

104
Q

what is venous volume affected by

A

Venous volume distribution affected by peripheral venous tone, gravity, skeletal muscle pump & breathing

105
Q

what determibes the amount of blood flowing back to the heart

A

Central venous pressure (mean pressure in the right atrium) determines amount of blood flowing back to heart.

106
Q

what determines stroke volume

A

Amount of blood flowing back to the heart determines stroke volume

107
Q

what does constriction in veins cause

A

In veins, constriction reduces compliance and increases venous return

108
Q

what does arteriole constrcition cause

A

Blood flow to downstream organs
Mean arterial blood pressure
The pattern of blood flow to organs

109
Q

what affects atrial pressure

A

venous return

110
Q

what affects vebous return

A

venous pressure

111
Q

what affects venous pressure

A

↑Blood volume
↑SNS activation of veins
↑Skeletal muscle pump
↑Respiratory movements

nuero (36 decks)

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