cardiovascular system Flashcards
pulmonary arteries
go to the lungs and chest to oxygenate oxygen deficient blood
pulmonary veins
go from the heart to the lungs –> oxygen rich
systemic arteries
oxygenated blood from the heart (aorta) for tissues around the body
systemic veins
take deoxygenated blood from repairing tissue back to the right atrium
why does the right ventricle have a larger diameter
due to having a thinner muscle
the left ventricle pumps with
4-6 times more pressure due to a 3:1 ratio in muscle mass between the left and right ventricles
systolic
contracting
diastolic
relaxing
steps of conducting system (contraction of the heart)
1) SAN activity and atrial activation begins
2) stimulus spreads across the atrial surfaces and reaches the AVN
3) there is a 100msec delay at the AVN, to allow the atria to fill
4) impulse travels along the interventriuclar septum (bundle of HIS) within the AV bundle branches to the Purkinje fibres and via moderator bands, to the papillary muscle of the right ventricle
5) the impulse is distributed by Purkinje fibre and relayed throughout the ventricular myocardium. Atrial contraction is completed and ventricular contraction begins.
SAN action potential
1) decrease in K+ permeability along with an increase in Na+ permeability (If current)
2) T-type (transient) Ca2_ channels open
3) threshold reached–> l type Ca2+ channels open (AP)
4) K+ channels open causing an efflux of K+
5) resting potential achieved
cardiac muscle action potential
1) rapid rise in Na+ permeability (voltage gated Na+)
2) slower rise in Ca2+ permeability and decrease in K+ permabilit. @nd smaller wave increases Na+ permeability
3) decrease in permeability in Ca2+ and an increase in K+ permeability
conductance of a cardiac action potinetal
intercalated discs: interconnect cardiac muscle cells and secured by desmosomes. Linked by gap junctions (propagate AP).
loca changes in currents–> passive depolarisation of adjacent muscle cells (voltage gated ion channels) through gap junctions
excitation contraction coupling
physiological process of converting an electrical stimulus to a mechanical response. It is the link between the AP generated in the sarcolemma and the start of muscle contraction.
excitation-contraction coupling process
1) impulse arrives at T-tubule, deep into the muscle
2) Ca2+ enter via L-type Ca+ channel
3) some of the ca2+ goes straight to the sarcomere and cause conformation change and contraction
4) other ca2+ will forma receptor complex with ryanodine (RyRs) and this causes Ca2+ induced Ca2+ release
5) this ca2+ will now go to the sarcomere
which receptor is responsible for calcium induced calcium release
ryanodine receptor
difference between cardiac smooth muscle and skeletal muscle
calcium induce calcium release
what alter Ca2+ release or storage and therefore also affect contractility/relaxation
- calcium channel blockers
- Beta blockers (effect A/NA)
- caffeine
sympathetic nervous system increases
permeability of membrane to Na+ and Ca2+
parasympathetic increases
permeability of the membrane to K+
sympathetic response
increase spontaneous depolarisation and educes time to initiate depolarisation
parasympathetic response
decreases spontaneous depolarisation and increases time to initiate depolarisation
B1 blockade leads to
- reduced contractility via reduction in the conc of cAMP
- reduced HR-similar effect to parasympathetic input
- reduced Ca2+ entry via camp-dpeendnet pK activity
- decrease in L type channel activity
- reduced renin secretion via selective B1 inhibition at GJ cell
PACE
preload
after load
contractility
‘Eart rare
stroke volume
SV= EDV-ESV
EDV
end diastolic volume - volume of blood just before contraction
ESV
end systolic volume- the volume of blood after contraction (left overs)
both hypertension and aortic valve stenosis lead to
decreases stroke volume
cardiac output
heart rate x stroke volume
Preload –> end diastolic volume
increases in EDV leads to increases in myocardial performance. Because as EDV increases, the starting myocardial muscle length also increases. This leads to more cross bridge formation and therefore there will be a more powerful contraction.
as the length of the muscle increases
contraction will also increases due to more cross bridges being formed. known as a strength force relationship
EDV effects
contractility and thus SV and thus CO
an increase in venous return will
1) increase EDV
2) increase stretch of muscle
3) increase cross bridge formation
4) increase force of contraction
5) increase SV and thus CO
venous return
Venous return is the rate of blood flow back to the heart. It normally limits cardiac output.
afterload/ ESV
the pressure in which the heart has to pump against. Higher the pressure in the aorta–> the more force required by the heart.
As afterload increases, cardiac output decreases
three factors that effect EV:
- preload/edv
- edv increases contractility and therefore less blood at the end of contraction
as after load increase
cardiac output decreases
contractility
controlled hormonally by A and NA that is circulating
B2
found in lungs
quantification of contractility- ejection fraction
ratio of SV to EDV
EF= SV/EDV
normal is between 55 and 75%
‘eart rate
neuronal and endocrine regulation–> increase HR= positive chrontopic factors (A and NA)
atrial reflex
Bainbridge reflex–> adjust heart rate in response to venous retune
–> stretch receptors in right atrium trigger increase in heart rate through increase sympathetic activity.
angina
chest pain when blood supply to muscles is restricted
common arteries affected by atherosclerosis
LAD
LCX
RCA
can occur at any point only artery
left coronary artery
divides into tow branches; circumflex and left anterior descending artery
circumflex artery
supplies the blood to the left atrium and the side and back of the left ventricle
left anterior descending artery
supplies blood to the front an bottom of the left ventricle and the front of the septum
coronary veins
take oxygen poor blood that has already been used by muscles of the heart and returns it to the right atrium
right coronary artery
supples blood to the right atrium and right ventricles , bottom portion of the left ventricle and back of the septum
three types of capillary
continuous
fenestrated
sinusoidal