Unit 4: SVT Flashcards
What are the effects of stress on the heart?
SNS activation - stress response
Adrenaline and no-adrenaline release
B1 - increase heart rate
B2 - vasodilation of central bv
A2- vasoconstriction of peripheral bv
What are the effects of caffeine on the heart?
Caffeine is structural analogue of adenosine
Bind to A2a receptors - acts as a antagonist to prevent go to spleep signals
Binds to A1 receptors - acts as an agonist to trigger wake up signals
This increases the individuals energy levels, can help them stay awaker for longer.
Eventually the body build up resistance to caffeine and downregulates receptors or receptors are less sensitive
What are the clinical features of an ECG?
What is each segment, how long should it last?
p wave -atrial contraction 4 small squares
QRS complex - ventricular depolarisation 2 small sqaures
T wave - repolarisation 7 small sqaures
PR segment - 1 or 2 small sqaures
ST segment - 2 to 3 sqaures
segment - does not contain waves
Internal - does contain waves
What are the different vagal manoeuvres?
What do they aim to do?
Valsalva maneouvre
Diving reflex
Carotid receptors massage
Aim to decrease HR and blood pressure by increasing activation of the vagal parsympathetic nervous system.
What is valsalva maneouvre?
Ask patient to hold a deap breath and stain as if constipated - increased intrathoracic pressure increases pulmonary return increase CA - decrease HR, then pressure occludes venous return from compression of IVC, decrease CO and increase HR
Release the breath and resume normal breathing
Venous return increases - cardioac output increases, heart rate and blood pressure decrease the counteract this
What is the diving reflex?
Place face in cold water, is detected by the trigeminal nerve.
Low oxygen environment as unable to breath underwater
Decrease respiration rate
Decrease HR
Vasoconstrction fo BV
Mechanism to conserve oxygen supply for vital processes
How does adenosins effect the heart?
Temporaly stops the heart, it should then restart in a normal cardiac rhythm
Binds to alpha1 receptors.
inhibits adenylate cyclase
Inhibitbs conversion of ATP to cAMP.
decreases levels of Ca2+influx and increase K+ efflux, prevents action potential being generated in the SAN.
Most be delivered in a high dose close to the heart as is rapidly broken down
What are the effects of stress on physical health?
Decrease wound healing - decreased fibroblasts, so less collagen and fibrillin synthesis
Decrease immunity - apoptosis of lymphocytes
Insomnia - cortisol acts on brain to promote wakefulness
Decreased muscle and bone mass - promotes gluconeogenesis
Disregulated HP axis - affect secretion of gonadotropic hormones,
WHat are the effects of stress on mental health?
Indicators of poorer mental health
More likely to suffer from anxiety or depression
Emotionally vulnerable, less resistance to external factors.
What is the moa of pronpanolol?
Binds to beta1 receptors
Inhibits andeylate cyclase, reduces conversion of ATP to cAMP
Decreases ca2+ influx
Reduces the probability of an action potential being generated.
What are the difference channel involved in action potential at the nodal cells (SAN) in the heart?
Funny channels - sodium ion influx
T-type ca2+ ion channels - short influx of calcium ion
L-type Ca2+ ion channels - long term influx of calcium ions
K+ channel - efflux of K+ during stage 3 of the action potential
What are the different channels used in an action potential generation in contractile cell in the heart?
Gap junction - diffusion of ions to propagate the action potential
Na+ channel - influx from ECF, efflux from SR
K+ channel - eflux
L- type calcium channel - influx
Ryanodine receptors - release of Ca2+ from SR
Ca2+ - influx to SR
What section of an ECG is the platau stage of ventricular contraction? Stage 2 of action potential?
QT - interval
Time from first depolarisation to last repolarisation
What are the four mechanical phases of the cardiac cycle?
Ventricular filling - includes atrial conraction
Isovolumetric contraction
Ejection
Isovolumetric relaxation
Suggest how the valsalva maneouvre can lead to a headache in some patients.
Decreased sympathetic tone - results in decreased HR and vasodilation hence decreased BP and decreased peripheral resistance
This leads to smaller cardiac output and a smaller cerebral perfusion, temporarly causing a headache until homeostasis mechanism readjust the cardiac output.
