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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
what does the duration of Cardiac muscle action potential control
contraction of the heart
26
what is longer cardiac muscle ap or nodal ap
cardial ap is ~200x longer
27
what are charactiristics of an effective pump
long slow contraction
28
how many phases
5
29
what are they
0 1 2 3 4
30
what is the Absolute refractory period (ARP)
= time during which no AP can be initiated regardless of stimulus intensity
31
what si Relative refractory period (RRP)
period after ARP where an AP can be elicited but only with larger stimulus strength
32
what is phase 0
upstroke/depolarisation
33
phase 1
early repolarization
34
phase 2
plateau (still depolarised but starting to decrease)
35
phase 3
repolarisation
36
phase 4
resting membrane potential Google to see graph shape
37
what causes phase 0
sodium influx (remember they are ions)
38
what causes phase 1
potassium efflux
39
causes phase 2
calcium influx
40
phase 3 and 4
potassium efflux
41
what 3 major organs control heart function
The brain/central nervous system The kidneys The blood vessels
42
function of the brain/cns
can effect immediate changes through nerve activity or slower changes through hormonal activity
43
The kidneys function in controlling the heart
the heart and kidneys share a bi-directional regulatory relationship usually through indirect mechanisms
44
how do blood vessels control heart function
by regulating the amount of blood that goes to and from the heart the blood vessels are able to influence cardiac activity.
45
what are subbranches of the autonomic nervous system
para | and symp
46
function of para
rest and digest
47
effect of para on the heart
decrease heart rate (HR) – decreases the slope of phase 4
48
function of sympathetic nervous system
‘fight or flight’
49
effect of symp on the heart
``` increase HR (chronotropy) – increases the slope of phase 4 increase force of contraction (inotropy) – increases Ca2+ dynamics ```
50
what nerve to heart
vagus
51
how does para decraese heart rate
effects pre potential in nodal cell
52
what does phase 4 determine
how quickly it can contract again
53
where do para nerves originate from
cranial part of spinal cord | sacral part of spinal cord
54
what nerves do they have
pre and post ganglionic fibres
55
what neurotransmitter do they release
Ach
56
what do para nerves achieve
controlling heart rate
57
where do symp originate from
thoracic and lumbar
58
what type of nerve
pre and post
59
what strcuture do symp nerves tend to synapse on
synpathetic chain (paraveterbral ganglia)
60
what neurotrasnmitter do they release at pre
Ach
61
and post
Can be nora a
62
so what does symp control
circulation
63
where is the vasomotor centre located
located bilaterally in reticular substance of medulla & lower third of pons
64
what 3 areas are they composed of
pressor area depressor area Cardio-regulatory inhibitory area
65
what is the pressor area aka
vasoconstrictor area
66
depressor aka
vasodilator
67
what is the vmc controlled by
Many higher centers of the brain such as the hypothalamus can exert powerful excitatory or inhibitory effects on the VMC.
68
what 2 portions of the vmc control the heart
lateral and medial
69
how does the lateral portion of the vmc control the heart
Lateral portions of VMC controls heart activity by influencing heart rate and contractility dont really need to know
70
medial
Medial portion of VMC transmits signals via vagus nerve to heart that tend to decrease heart rate. dont really need to know
71
distally
Transmits impulses distally through spinal cord to almost all blood vessels
72
how does para innervate
``` ACh binds to m2 muscarinic receptor on cm of sa node bind to (inhibotory ]) g protien, inhibits of adenyl cyclase ```
73
and symp
releases nora acts on beta 1 receptor stimulate adenyl cyclase increase level of protien kinsae
74
what will para do to heart
decrease heart rate
75
symp
increase
76
what would happen if you cut para
heart rate increase q
77
cut symp
heart rate decrease
78
symp nerve innervating kidney
less glomerular filtration less na+ excretion increase blood volume (aldosterone)
79
what is the blood volume detected by
Detected by venous volume receptors
80
what else does symp innervation do
more renin secreation more angiotensin 2 causing vasoconstriction high blood pressure
81
what is blood pressure detected by
detected by arterial baroreceptors
82
how do kidney affect heart
affect blood volume and vlood pressure
83
how does kidney increase blood volume
less na+ excretion
84
hoe does the kidney affect blood pressure
increase secretion of ang II | increasing blood pressure
85
angiotensin 2 also secretes what
aldosterone
86
what do. the symp nerve fibre innervate
afferent and efferent atrerioles of glomerulus
87
what affect on afferent arterioles
symp inneravtion causes vasoconstriction by activation of a1- adrenoceptor
88
what is the nuerotransmitter
noradrelaline
89
what does that cause
decrease glomerular filtration rate | less na filtered
90
function of juxtaglomerlular cells
the site of synthesis, storage & release of renin
91
which recpetor causes renin secretion
b1 adrenoceptor increases aldesterone increases blood volume
92
define inotropic
increases contractility
93
chronotropic
increases heart rate
94
What effect will activation of renal arteriole alpha-1 receptor eventually have on the heart?
Increased chronotropy & inotropy
95
what happens when there is a decrease in heart filling
less baroreceptor firing more symp nerve activity increases heart rate
96
what happens in distention
higher barorecpetor firing | less sns activity
97
what is decrease in fillling caused by
less blood coming back to the heart
98
distention.
more blood coming back to the heart
99
what controls how much blood comes back to the heart
kidney and blood vessels
100
what are large pulmonary vessels sensitive to
Volume sensors (also atria & right ventricle): send signals though glossopharyngeal & vagus nerves
101
what are Arterial circuit Aortic arch, carotid sinus & afferent arterioles of kidneys sensitive to
Pressure sensors: send signals though glossopharyngeal & vagus nerves
102
when there is a decrease in pressure
less barorecptor firing | higher sns
103
increase in pressure
high barorecpetor firing | less sns
104
what is venous volume affected by
Venous volume distribution affected by peripheral venous tone, gravity, skeletal muscle pump & breathing
105
what determibes the amount of blood flowing back to the heart
Central venous pressure (mean pressure in the right atrium) determines amount of blood flowing back to heart.
106
what determines stroke volume
Amount of blood flowing back to the heart determines stroke volume
107
what does constriction in veins cause
In veins, constriction reduces compliance and increases venous return
108
what does arteriole constrcition cause
Blood flow to downstream organs Mean arterial blood pressure The pattern of blood flow to organs
109
what affects atrial pressure
venous return
110
what affects vebous return
venous pressure
111
what affects venous pressure
↑Blood volume ↑SNS activation of veins ↑Skeletal muscle pump ↑Respiratory movements

nuero (36 decks)

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