cardiovascular system L5-10 Flashcards
functions of CVS
controlled/ continuous transfer
hormone transport
homeostasis
CVS structure
2 circulations in series (systemic> high and pulmonary> low)
unidirectional flow
equal blood vol in each circulation
which vessels carry blood away from heart?
aorta
pulmonary artery
which vessels carry blood into heart?
vena cava
pulmonary vein
atrioventricular valves
R - tricuspid
L- mitral/ bicuspid
semilunar valves
R- pulmonary
L- aortic
stroke volume
volume of blood pumped by 1 ventricle
average stroke volume
~75ml at rest
cardiac output
volume of blood pumped per ventricle per minute
cardiac output formula
heart rate * stroke volume
venous return
amount of blood returning to heart
at steady state VR=CO
arteries properties
high pressure
elastic
function for distribution
arterioles properties
high resistance
blood flow control to tissues
capillaries function
thin wall
arranged in parallel
exchange function
veins properties
decreasing pressure
one-way valves
capacitance/ collection function
pressure of fluid in motion rule
decreases with distance due to friction
pulse pressure
systolic pressure - diastolic pressure
biggest drop in pressure
from arterioles
mean arterial pressure
pressure averaged over time
blood flow relation to resistance
blood flow proportional to 1/ resistance
Darcy’s law
flow = change in pressure/ resistance
resistance factors
distance
vessel radius
blood viscosity
poiseuille’s law
flow proportional to change in pressure * radius^4
blood flow
volume/ minute
blood velocity
distance travelled / minute
blood velocity factors
flow
cross-sectional area
cardiac muscle cells
striated with T-tubules > SR
actin/ myosin/ troponin sarcomere
a.p generation to elevate cytoplasmic Ca2+ for contraction in excitation-contraction coupling
autorythmic
nerve supply regulated HR
2 groups of myocytes
conducting > fast spread of a.p’s
work> generate atrial/ ventricular force
heart beat initiation location
sino atrial node in right atrium
synctium
work cells interlinked by intercalated discs
spread of excitation from SAN
conducting fibres in atria/ ventricles
cell-cell via gap junctions
pacemaker potential function
spontaneously depolarizes to threshold so AP is generated, setting HR
ionic basis of electrical activity of SAN
- slow initial depolarization
- full depolarization
- repolarization
- minimum potential phase
slow initial depolarization of SAN
cation leak via non-spec cation leak channels in PM
full depolarization of SAN
at threshold, v-gated Ca2+ channels open and Ca2+ enters cell
repolarization of SAN
Ca2+ channels close and K+ open
minimum potential phase of SAN
K+ remains open
membrane hyperpolarization and non-specific cation channels open, repeating cycle
ionic basis of electrical activity in ventricular muscle cell
- rapid depolarization
- initial repolarization
- plateau
- repolarization
rapid depolarization of ventricular muscle cell
v-gated Na+ channels open and Na+ enters
initial repolarization of ventricular muscle cell
Na+ channels inactivated and K+ leak
plateau of ventricular muscle cell
Ca2+ channels open as K+ leave , prolonging depolarization
repolarization of ventricular muscle cell
Na+/ Ca2+ channels close and K+ exits
trigger Ca2+
v-gated Ca2+ channels in plateau phase lead to muscle contraction > Calcium induced Calcium release
factors affecting force of contraction
sarcomere length
no. active cross-bridges (how much Ca2+ bound to troponin-C, depending on CICR amount)
refractory period of heart
outlasts contraction period to prevent tetanus
ECG
measures electrical signals conducted to body surface for depolarization/ repolarization/ disturbance recording
(summed electrical activity generated by all working cells of heart)
P wave
atrial depolarization
QRS complex
ventricular depolarization
T wave
ventricular repolarization
arrythmia
abnormal heart rythmns
1. impulse propagation
2. impulse initiation
cardiac cycle
cycle of pressure and volume changes in the heart chambers w contraction and relaxation
cardiac cycle stages
1.ventricular filling/ late diastole
- atrial systole
2. isovolumetric ventricular contraction
- AV valves close
3. ventricular ejection
- semilunar valves open
4. isovolumetric ventricular relaxation
cycle repeat
systole
contraction
diastole
relaxation
end-diastolic volume
most blood in ventricles
end-systolic volume
minimum blood in ventricles
lubb
S1-AV valve closure
dupp
S2-SL valve closure
phonocardiogram
measure pressure over time
- all 4 valves can be individually listened to for functional abnormalities
valve diseases
stenosis
incompetence (regurgitation/ leaky)
arterial pressure wave
diastolic pessure
systolic pressure
dichrotic notch
aortic valve closure
MAP formulae
diastolic pressure + 1/3 pulse pressure
pulse pressure formulae
SP-DP
systemic arterial blood pressure
measured at heart level on upper arm
systolic/ diastolic measurement
~120/80mmHg
auscultation
2 types of flow?
measures systolic/ diastolic flow
laminar
turbulent
laminar flow
silent flow w no compression
turbulent flow
korotkoff sounds
pulsatile blood through artery
cardiac output formula
stroke volume * Heart rate
total peripheral resistance
sum of individual vessel resistance to flow
mean arterial blood pressure formula
cardiac output * total peripheral resistance
average cardiac output/ heart rate/ tidal volume at rest
4.9 L/min
70ml
70bpm
parasympathetic neural control of heart
ACh
muscarinic ACh receptor activation
sympathetic neural control of heart
NA
B1-adrenergic receptor activation
sympathetic stimulation with SAN pacemaker
tachycardia
tachycardia
increased HR due to steeper potential slope/ quicker threshold time
parasympathetic stimulation w SAN pacemaker
bradycardia
bradycardia
decreased HR
longer threshold time
chronotropic effects
changes in HR
2 mechanisms for stroke volume regulation
intrinsic
extrinsic
Starling’s law of the heart
force of contraction proportional to initial muscle fibre length in diastole
intrinsic neural regulation
VR^ ^EDV in diastole (stretching cardiac muscle) ^ force of contraction and stroke volume
intracellular Ca2+ lowers tension/ matches R/L input of heart/ heart adaptation when pumping/ prevents lung oedema
extrinisic neural regulation
^sympathetic activity
enhances contractility/ NA/ binds to B1 adrenergic receptors
enhances SV
+inotropic effect
lusitropic effect
changes in rate of muscle relaxation
catecholamines
^ contractility by triggering more Ca2+
what’s venous return maintained by?
venous-atrial pressure difference
skeletal muscle contraction
venometer tone
respiration
arterioles function
control TPR
match local blood flow to local metabolic need (decreases tone w ^ need/ radius)
arteriole radius control
local
hormonal
neural
autoregulation of tissue blood flow
constant flow w ^pressure
intrinsic / myogenic smooth muscle activity
safety mechanism preventing damage to vessels
flow formula
MAP/R
metabolic control of tissue blood flow
*can override myogenic
metabolism-derived vasodilators»_space; ^CO2/ ^H+ ^temp ^adenosine ^K+ / decreasing O2
vasodilators
kinins
histamine
adrenaline
vasoconstrictors
angiotensin II
vasopressin
adrenaline
sympathetic vasoconstriction fibres
release NA
bind to a1-adrenergic receptor for vasoconstriction
B-receptor vasodilation
epinephrine from B-receptor
a-receptor vasoconstriction
norepinephrine from a-receptor
