cardiovascular- control of heart function Flashcards
What are 3 components of heart?
- muscle cells : contract + relax 2. specialised electrical cells: create currents and trasnmit those in. regulate contraction 3. vessels: coronary blood vessels supply heart
What is the pacemaker?
where it is found.
sinoatrial node. at the junction of crista terminalis
What else has pacemaker activity?
Atrioventricular node, slowc alcium mediated AP
found in triangle of koch at base of right atrium
What do internodal tracts do?
connect sinoatrial node to AV node
What does bundle of His do?
from atrium through intraventricular septum to apex of heart to supply purkinje fiberes
How many phases does AP of a nodal cell have?
what are they called?
What is each phase of nodal cell AP due to?
upstroke - due to Ca2+ influx
repolarisation- due to k+ efflux
pre-portiential - NO resting membrane due to Na+ influx through funny channel
(happens straight after repolar always increasing to upstroke)
What is important to consider about Ap profiles of cardio cells?
and how is it caused?
different AP shapes
different ions flowing and different ion channels expression on CM
compare a cardiac muscle and nerve muscle
longer AP in cardiac as controls contraction of heart,, to produce an effctive pump
Stages of AP in cardiac muscle? (5)
What else is there outside of 5 phases in Ap of cardiac muscle?
Absolute refractory period
relative refractory period
What is aboslute refractory period?
time during which no AP can be intiated regardless of stimulus intesnity
so heart doesn’t many beats in small amount of time
What is relative refractory period?
period after ARP when AP can only be elicted when larger stimulus strength
What is each phase of ventricular cell due to?
0 - K+ efflux
1 - Na+ in
2 - Ca2+ in
3&4- K+ out
What 3 organ systems have an effect on activity of heart?
- brain/CNS - immediate change through nerve activity or slower hormonal
- kidney - bidirectional through indirect mechanisms
- blood vessels influence amount of blood in an out
How does parasymathetic travel to heart?
and effect?
vagus nerve
decrease HR by decrease AP in nodal cell, SAN
decreased slop of phase 4
What affect does sympatheric on heart?
- incraese HR by - increase slope of phase 4, easier AP
- increase contraction - increase Ca2+ dyanmics
What does pre-ganglion nerves of parasym use as NT?
aceetylchiline
What does post-ganglion nerves of parasym use as NT?
Ach
What are the 2 receptors of parasym pathway?
What do pre-gang nerves of symypathetic use as NTs?
Ach
What do post-gang nerves of symypathetic use as NTs?
Noradrenaline
where do SNS pre and post gang synapse?
sympatheric chain
(paraverterbral ganglia)
Where is vasomotor centre located?
medulla and lower 1/3 of pons
What is it VMC compsoed of?
vasocontrsictor area
vasodilator area
cardio-reg inhibitory area
Where do its impluses go?
almost all blood vessels
What has effects of VMC?
higher centres of brains such as hypothalamus exert excitary or inhibitory effects
What does lateral portions of VMC control?
Heart activiy by influecning heart rate and contractibility
What is the function of medial portion of GMC?
transmits via vagus nerve to heart, decreae HR
What receptors are on heart?
parasympathetic SA nodule - M2 muscorinic receptor
sympathetic noradrenaline on B1 receptors
What effect does CUTTING sympathetic and parasymp have on heart?
decrease heart rate even when being directly stimulted
they always have an effect even when not being inervated
i.e basal effect
How do symp effect kidneys?
deccrease glomerular filtration - decrease Na+ sectrion
increase blood volume
How is blood volume detected?
venous volume receptors
What affect does increase in sympathetic nerves have on kidney?
increase activity
increase renin
increase AT11: causes vasoconstriction and increase BP
What is blood pressure detected by?
aterial baroreceptos
How does kidney indirectly affect heart?
control of blood volume and pressure that in turn is detected and effects heart function
Exactly how does sympathetic effect renal system?
2 areas-
afferent arterioles of glomerulus
by activation fo a1-adrenoceptors - vasonctiction that causes decrease GFR as decreased Na+ increases BV
other affect is on juxgolumerus cells - renin secretion by B1 adreonergic receptor increases BP
How is blood volume increased by sympathetic nerves in kidneys?
juxtaglomerular cells
B1-adrenoceptor causes renin secretion
increases aldosterone
What are uses/sensation of volume?
in importantly large pulomonary vessels, atria, ventricle
signals thro glossopharyngeal and vagus nerve,
decreased filling increases firing and SNS activity
What is distention?
What effect does it have on nervous pathway?
distention - heart full
increase baroreceptor and decreases SNS
What regulates blood volume filling?
kidney and blood vessels
Where are PRESSURE sensors found in blood vessels to feedback for heart?
arterial circuit: aortic arch, cartoid sinus and afferent aterioles of kidney
What effect does decrease in pressure have on pressure sensors in arterial arch?
less baroreceptor firing and increased SNS activity
What affects venous volume?
venous tone, gravity, skeletal muscle pump and breathing
central venous pressure determines what?
amount of blood flowing back to heart
What effect does constricition have on veins?
constriction reduces compiance and increaes venous return
In aterioles what constricition determine?
a) blood flow to downstream organs
b) mean arterial blood pressure
c) pattern of blood flow to organs
What effects venous pressure and what effect does venous pressure have?
