heart as a pump Flashcards
describe the right side of the heart
thin muscular wall
works at low pressure
RV pumps blood into the pulmonary circulatory system whet oxygen taken up, carbon eliminated
describe left side of the heart
thicker muscular wall
higher blood pressure
LV pumps blood into the systemic circulatory system for delivery to the limbs and organs
resting state amount of blood circulating
about 5 litres per minute
define
- myocardium
- pericardium
- endothelium
- cardiac muscle
- covered by epithelial sac called pericardium
- inner surface facing the blood
conducts blood away from the heart
aorta and pulmonic artery
returns blood to the heart
pulmonary veins and vena cava
describe function pulmonic and aortic valves
respond passively to pressure gradients
prevent backflow from arteries into relaxing ventricles
describe AV valves
mitral: 2 leaf, higher pressure left ventricle
tricuspid: 3 leaf, lower pressure right ventricle
tethered to ventricle wall by tendon like cords and papillary muscle
systole
period of contraction
diastole
period of relaxation
cardiac cycle begins at
diastole
ventricles relax and fill with blood
AV valves are
open
following stage of heart cycle (4 parts)
P wave
depolarisation of atria
contraction
blood ejected from ventricles
when ventricular pressure exceeds atrial pressure AV valves
close
last 20% of ventricular filling cause by
contraction of atria
systole begins with
QRS complex
depolarisation of ventricles
- when ventricles start to contract all valves are….
- this causes…
- this is called
- does blood volume change?
- closed
- increased ventricle pressure
- isovolumic contraction
- no
- increased pressure opens
2. this causes
- pulmonic and aortic arteries
2. blood to be ejected
following ejection of blood from ventricles
- myocardium relaxes
2. pressure falls
pulmonic and aortic arteries close when
ventricular pressure is less than that in the pulmonic and aortic arteries
describe what happens during isovolumic relaxation
- with all 4 valves closed ventricles relax further
2. with pressure in ventricles less that atria, AV valves open and blood flows passively into ventricles.
EDV
end diastolic volume
volume of blood left in the ventricles at the end of ventricular relaxation
about 125ml (LV)
SV
stoke volume
volume of blood ejected from the ventricles
about 70ml
ESV
end systolic volume
blood remaining in the vetricle at the end of ventricular contractin
about 55ml
CO
Cardiac output
volume of blood ejected by ventricle over a period of time
CO= SVxHR
for example
CO 5L= SV 70ml per beat xHR 70 beats per min
EF
ejection fraction
efficiency of the heart
SV / EDV x 100 = EF (%)
force of cardiac contraction increased by
- cardiac muscle fibre length at beginning of contraction
2. contractility of muscle fibre
Frank-Starling relationship
- length of cardiac muscle fibre dependent upon
- stretch ….
- volume of blood in ventricle
2. increases overlap of actin and myosin to optimal length and contractile force increases
Preload
degree of stretch in myocardium before contraction
an increase in preload filling will
- Raise EDV
2. increase pressure generated (systolic pressur)
4 factors that can increase venous return (EDV)
- Skelatal Muscle Pump
- Respiratory Pump
- Sympathetic Nervous System
- Increase in blood volume (doping)
and inotropic agent…
examples of inotopic agents
affect cardiac contractility
epinephrine norepinephine
