cardiac output and regulation Flashcards
what is cardiac output?
the amount of blood pumped by each ventricle in one minute
produce of heart rate and stroke volume
how do calulate cardiac output?
CO= HR X SV
what is stroke volume
amount of blood pumped out by a ventricle with each beat
what are the layers of the heart wall?
epicardium
myocardium
endocardium
what is the epicardium?
visceral layer of serous pericardium
what is pericardial fluid?
surronds the heart and protects it from compression
what is cardiac muscle?
fibres that wrap around the whole organ
contracts and twists to push blood out
why is the left side thicker?
higher pressure
systemic circulation here
more resistance
what is the coronary circulation?
supplies the heart with oxygen and nutrients
what are the two main branches of the left main coronary artery?
LAD
circumflex
what does the sympathetic nervous system do to the heart?
increases rate and force of contraction
what does the parasympathetic nervous system do to the heart?
slows heart rate
what does activation of the SAN do?
increases firing and thus heart rate too
what does the change in time lag of the cardiac cycle do?
allows blood to move from the atria to the ventricles
allows signal to move from the SAN to AVN
where are valves found in the heart?
2 atria ventricular valves
2 semilunar
what are the atria-ventricular vales?
mitral valves separates atrium from ventricles on each side
what are the semilunar valves
pulmonary valve goes from right ventricle to lung
aortic valve goes from left ventricle to body
where is the tricuspid valve found?
RA to RV
where is the pulomary valve found
RV to pulmonary trunk to lungs
where is the mitral/ bicuspid valve found?
LA to LV
where is the aortic valve found?
LV to aorta
what is the function of AV valves
allows blood to flow to ventricles ad prevents bacl flow during contraction
what are valves made of?
connective tissue connected to papillary muscles in endocardial wall
contraction of the muscles closes the valves
what are papillary muscles?
connected to valves and close and open them
they contract during systole and prevent valves inverting
what is S1
the sound of the closing of AV vales at start of ventricular systole
what is S2
the sound of semilunar valves closing at the edn of ventricular systole
whats key about looking at cardaic muscle
striations
collagen
intercolated disks
how does cardiac muscle appear ?
branches of the fibres and myocytes for branches
intercolates disks are seen between sections
whats the function of an intercolated disk?
form the mechanical connection for contraction and force to be transmitted across the heart
what cells are found in the heart?
myocytes ECM fibroblasts muscle blood cells
what alters the distrubution of myocytes and fibroblasts?
species
what are the physical connections found in cardiac muscle?
intercollated disks
desmosomes
what do jap junctions do within cardiac muscle?
allow communication between adjacent cells
electrical, small molecules, small RNA
where are mitochondria found in cardiac muscle?
near the myofilament
define sarcomere
small region of contraction
thick filament
myosin
thin filaments
actin
dark bands
thick myosin mainly, some overlapping thin actin
A bands
ansiotrophic bands, dark
thick myosin and some ovelapping actin
light I bands
thin actin only
whats the end of a sarcomere called?
Z line connects to ECM
what is the M line?
middle of the sarcomere
myosin
what happens during contraction
I band shrinks
A and M band shrink
describe the steps of the sliding filament mechanism
- tropomyosin prevents myosin head attaching to binding sites of actin
- calcium ions released from endoplasmic reticulum causing tropomyosin to move
- myosin can now bind to actin
- head changes angle, moving actin along, ADP released. power stroke, conformational change
- ATP fixes to head, myosin detaches from actin
- ATP to ADP using ATPase makes energy for myosin head to resume normal
- cycle repeats
what is actin and myosin like at rest?
proteins troponin and tropomyosin prevent myosin from interacting
what does calcium do to tropomyosin?
causes a conformational change allowing actin and myosin to interact
what is a T-Tubule?
helps transmit electrical signals into the interior of the cell
act as microvili increasing surface area
7 steps of the cardiac cyce
atrial contraction isovolumetric contraction rapid ejection reduced ejection isovolumetric relaxation rapid filling reduced filling
what happens during atrial contraction
initiated by the P wave
valves between atria open
semilunar valves closed
what is isovolumetric contraction
QRS complex
ventricle pressure increases with no volume change
contraction without volume change
no blood movement
what happens during rapid ejection
blood flows rapidly from ventricles to arteries
AV closed
semilinar open
what happens during isovolumetric relaxation?
valves closed
venticle pressure drops
no volume change but pressure drops
was is reduced ejection?
ventricles repolarise tention in ventricle reduced blood flow due to kinetic energy now volume decreased tension drops
what is isovolumetric relaxation
valves closed ventricle pressure drops pressure down after contraction AV valve then open no volume change but pressure down as muscle relaxes
what is the ejection fraction?
proportion ejected out but some blood left behind
what happens during rapid filling?
AV valves open, semilunar closed
ventricular relaxation
pressure lower in atria
fills with blood
what happens during reduced filling?
chamber fills, pressure increases, amount of blood entering slows,
AV open so some blood flows via gravity to ventricles
semilunar closed
which steps of the cardiac cycle are systole?
atrial contraction
isovolumetric contraction
rapid ejection
reduced ejection
which steps of the cardiac cycle are diastole?
isovolumetric relaxation
rapid filling
reduced filling
what is a diad?
The diad is a structure in the cardiac myocyte located at the sarcomere Z-line. It is composed of a single t-tubule paired with a terminal cisterna of the sarcoplasmic reticulum.
function of the diad?
electrical impulse travesl through the diads to the cells
causes electrochemical gates to opn
where does calcium come from for contraction?
first comes from outside the cell
this then triggers stores from the sarcoplasmic reticulum to be used
by how much does the calcium concentration increases in the cytosol ready for contraction
from 0.1uM to 10uM
how is calcium removed again after contraction?
calcium pump
sodium calcium exchanger
what is excitation-contraction coupling?
physiological process of converting an electrical stimulus to a mechanical response. It is the link (transduction) between the action potential generated in the sarcolemma and the start of a muscle contraction
what allows actin and myosin to bind/ interact?
the binding of calcium to trononin-C
what does the binding of myosin to actin result in?
ATP hydroloysis which supplies the energy for the conformational change in actin-myosin
how does calcium enter to cytosol?
L-type ca+2 channels
what is calsequestrin?
calcium-binding protein of the sarcoplasmic reticulum. The protein helps hold calcium in the sarcoplasmic reticulum after a muscle contraction, even through the concentration of Ca is higher here than in the cytosol
what does the sodium-calcium exchanger do?
exchanges 3 Na for each calcium
uses electrogenic potential generation to work
the calcium is moved out and Na in
why is the Na/K pump also used in muscles?
during contraction, Na comes in but you dont want too much inside so the pump helps regulate this
by removing calcium, Na can get too high so it now triggers the Na/ pump to remove some Na
name the pacemaker electrical acitivty cells in the heart
sino-atrial node
atrioventricular node
bundle of his
purkinje fibres
how do electrical activty heart cells work?
they use ATP to create a concentration gradient of either side
the cell then works as a battery: then chennals are open there is a flow of ions ad a potential difference across the membrane and a flow of charge
what are concentrations of K like?
high within the cell
low outside
chemical gradient for it to diffuse out of the cell
what describes permeability of the cell embrane to a given ion?
conductance
what is conductance
modification of currentX resistance = voltage
when relaxed what is the potential difference of all the ions?
K higher inside
Ca higher inside
Na higher outside
pumps maintain this
describe Ohms law
resistance is now conductance in this case
permeability of an ion is related to its charge
what determines the movement of ions?
both the concentration gradient and membrane potential
and ion pumps
what is the equilbrium for potassium
goes out
need negative potential
whats the quilibrium for sodium
high cone outside
flows into cells
positive potential needed to stop flow in
whats the equibrium for calcium
high outside
flows into cells
positive differene needed to repel it to move in
what causes action potentials in non-pacemaker cells?
depolarising currents from neighbouring cells
describe the generation of an acton potential
- STIMULUS excites the membrane, Na channels open Na in, less negative
- DEPOLARIsATION, reaches threshold, more Na influx
- REPOLARISATION, na channes close, K open, K diffuses out, back to resting negative
- HYPERPOLARIATION, K channels slow to close, more negative than resting
- RESTING ion channels reset
