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Human physiology > regulation and adaptation of the heart > Flashcards

regulation and adaptation of the heart Flashcards

1
Q

what factors determine the membrane potential?

A

concentration gradients of K, Na,Ca

electrical conductance of the memebrane being regulated by ion channels

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2
Q

what is an electrogenic pump?

A

contributes to the resting membrane potential

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3
Q

what maintains a negative charge inside the cell?

A

na/K pump

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4
Q

how does electrical activity pass through the heart?

A

contractile fibres

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5
Q

how do myocardial cells work?

A

SAN depolarises across all cells

cells dont contract though till they recieve this activity much like a wave

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6
Q

what is the prepotential?

A

tendency for K and Na chennels to open allowing influf of positive ions into cells
causes depolariasation

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7
Q

what affects the prepotential?

A

autonomic nervous system

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8
Q

what is the sloping prepotetial caused by?

A

slowly declining membrane potential is called the pre-potential, the slope detemines the heart rate
it is caused by the Na pacemaker current

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9
Q

describe the steps of the impulse conduction through the heart

A
  1. SA node fires wave of depolarization across atria
  2. stimulus spreads across atria reaching AV node
  3. millisecond delay at AV node before atria contraction begins
  4. impulse travels along septum with th AV bundle and Purkinje fibres into ventricles
  5. impulse distributed by Purkinje fibres and relayed throughout the ventricular myocardium and ventricular contraction begins
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10
Q

how can the ECG be used as a diagnostic tool

A 
electrical axis
heart rate
activation sequencce disorders
drugs
electrolyte imbalance
carditis
pacearker issues
coronary circulation
hypertrophy
arrhythmias
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11
Q

what is sinus tachycardia

A

impulses from SA node at rapid rate

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12
Q

what is an atrial flutter

A

impulses travel in circular route across atria

ventricular response irregular

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13
Q

what is atrial fibrillation

A

impulses have chaotic, random pathways in the atria

ventricles irregular too

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14
Q

what is ventricular fibrilation

A

very serious as output decreased

rapid, wide, irrregular venticular complexes

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15
Q

what is stroke volume dependent on?

A

energy of contractios
atrial pressure
muscles ability

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16
Q

what does cardiac output depend on?

A

affected by activity

changes affected by heart rate and stroke volume

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17
Q

define inotropy

A

strength of contraction

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18
Q

define chronotrophy

A

contraction frequency

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19
Q

define bradycardia

A

decreased heart rate

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20
Q

define tachycardia

A

increased heart rate

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21
Q

define dromotrophy

A

the velocity of signal conduction

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22
Q

define lusitropy

A

myocardial relaxation

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23
Q

define bathmotropy

A

myocardial excitability

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24
Q

what does the sympathetic nerve innervation do?

A

increases heart rate and force of contraction

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25
what does the parasympthtic nerve innervtion do?
slows the heart rate down
26
what happens during sympathetic regulation?
``` inotropy up chronotrophy up dromotrophy up bathmotrophy up lusitriophy up faster, harder ```
27
what increases sympathetic innervation
exercise standing up stress haemorrhage
28
what happens to the ejection fraction during sympathetic inervation?
increases
29
what hapens to stroke volume during sympatetic innervation
increased
30
what causes increased luisotrophy during symatheic innervation
phosphorylation of actin filaments
31
what mediates sympathetic innervation?
B-adrenergic receptors
32
what mediates parasympathetic innervation?
M2 muscarinic acetylcholine receptors
33
what happens during parasympathetic innervation?
chronotrophy down inotrophy down bathotrophy down dromotrophy down
34
at rest what keeps heart rate suppressed?
parasmpathetic
35
what is the anrep effect?
increased arterial pressure causes increased contractility of myocardium
36
what is the effect of temperature
fever increased heart rate | cooling is used in surgery to slow heart rate
37
what is the frank-starling mechanism?
the more the ventricle is filled with blood during diastole, the greater the stroke voume
38
what does increased blood volume cause in the frank-starling mechanism
increased stretch of the myocardium equalling and increase force to pump the bloo out
39
when does the law become invalid ( frank-starling)
after a certain LVEDP | left ventricular end-diastole pressure
40
what is the calcium tension curve
sensitivity of calcium depends on the sarcomere length
41
what does a long sarcomere mean for calcium?
myofilaments mroe sensitive to calcium | more Ca can bind to thin filaments as there is less overlsp
42
what does a short saarcomere mean for calcium?
more overlap, less sensitive
43
what is Laplaces law?
tension on the wall of the heart is product of the pressure times the radium of the chamber the tension is invertly related to the thickness of the wall
44
equation of laplace's law
internal presssure P = 2Tension / radius
45
as the radius increased what happened? Laplace's law
pressure decreases
46
what is preload?
stretch of the cardiac muscles when exposed to diastole conditons
47
what affect preload?
venous presssure, rate of venous blood flow, venous tone and volume of circulating blood
48
define afterload?
tension produced by the heart in order to eject blood into vessels
49
what affects afterload?
blood pressure
50
what affects the venous pressure?
``` blood volume gravit/posture muscle pump respiratory pump cardiac output ```
51
where are baroreceptors found?
arotic arch
52
what are baroreeptors?
nerve ending in the adventitia of carotid sinus and aortic arch sense distortions in vessels in blood pressue
53
what do baroreceptors sense?
degree of pressure through stretch
54
what is the baroreceptor refex?
depression of the heart rate by activating vagus nerve vasodilation through decreasing sympathetic activity loweres blood pressure contraction strength reduced too
55
what can be reduced to lower blood presure?
Bp is result of cardiac output and total peripheral resistance so can chnge one of these two
56
natura causes of long term myocardial adaptation
exercise | pregnancy
57
what happens when the heart is stressed?
undergoes hypertrophy and changes gene expression
58
what is hypertrophy
process where the heart changes gene expression in response to new envirnental requirements
59
how does hypertrophy actually occur?
- expression of genes changes | - isoform shifts in cytoskeletal proteins and ECM
60
what is physical hypertrophy?
temp increase in heart size due to enlargement of cardiac myocytes as a result of exercise improves functioning
61
what is pathological hypertrophy?
stress leading to change. leads to inability of the heart to deliver blood and oxygen
62
what can pathological hypetrophy lead to?
abnormalities in metabolism more heart stress heart failure
63
what is heart failure defined as?
progressive disrder which damages the heart | weakens the cardiovascular system
64
what does heart failure cause in the body?
inadequate blood flow to tissues | blood pressure issues
65
causes of heart failure
myocardial infarction cornary heart disease valve diease hyerptension
66
what is dilated cardiomyopathy?
los of myocytes being replaced by fibrobasts | heart cannot contract as cell
67
what happens in cardiac hypertrophy on a cellular level?
wall thickens no proliferations cells get bigger
68
what is the P wave
depolaristion of the atria
69
what is the QRS complex
depolaristion of the venticles
70
what is the T wave
repolarisation of the venticles

Human physiology (21 decks)

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