the structure and function of the heart 2.6 Flashcards
hearts function
a muscle that pumps blood around the body via a complex network of blood vessels
what is the heart made up of
four chambers, right and left atrium and right and left ventricle
direction of blood through the heart
-deoxygenated blood enters the right atrium through the vena cava, the right atrium contracts and blood is forced into the right ventricle
-at the same time, oxygenated blood enters the left atrium through the pulmonary vein, the left atrium contracts and blood is forced into the left ventricle
-the right ventricle contracts and deoxygenated blood is pumped through the pulmonary artery which travels to the lungs to pick up oxygen
-the left ventricle contracts and oxygenated blood is pumped through the aorta to the rest of the body
what are the walls of the heart made up of
cardiac muscle
why is the wall of the left ventricle thicker than the right ventricle
because it has to pump blood all around the body whereas the right ventricle only has to pump blood to the lungs
where are valves present in the heart
between the atria and ventricles and between the ventricles and pulmonary artery and aorta
valves function
prevent the back flow of blood and ensure blood travels in the one direction
what is cardiac output
the volume of blood pumped through each ventricle per minute
how to calculate cardiac output
CO = HR x SV
HR (heart rate)
SV (stroke volume)
heart rate
the number of beats per minute (bpm)
stroke volume
the volume of blood (in litres) pumped by the left ventricle during one contraction
cardiac cycle
the pattern of contraction (systole) and relaxation (diastole) in one complete heartbeat
average cardiac cycle
0.8 seconds based on a heart rate of 75 bpm
atrial systole
atria contract together pushing remaining blood into the ventricles through OPEN AV valves
ventricular systole
-ventricles contract CLOSING AV valves
-SL valves OPEN and blood is pumped out of the heart and into the aorta and pulmonary artery
atrial and ventricular diastole
-blood returns to atria through vena cava and pulmonary veins
-increased volume of blood in atria causes AV valves to OPEN
-blood flows down into ventricles
-higher pressure in the arteries closes the SL valves
what causes the heart sounds
the opening and closing of AV and SL valves
what valve causes the lubb sound
the closing of the AV valves
what valve causes the dupp sound
the closing of the SL valves
where does the heart beat originate
the heart itself
what regulates the heart
the nervous and hormonal control
where is the SAN located
the wall of the right atrium
SAN
(sino atrial node) sets the rate at which the heart contracts
what controls the timing of the cardiac muscle
impulses from the san spreading through the atria causing atrial systole
where is the AVN located
centre of the heart
AVN
(atrio ventricular node) impulses travel down fibres in the central wall of the heart and then up through the walls of the ventricles causing ventricular systole
calculating heart rate using an ECG
60/time for 1 heart beat
what indicates every heart beat
SAN
what can alter heart rate
nervous and hormonal activity
what regulates the rate of the SAN
the medulla through the antagonistic action of the automatic nervous system
what happens when there’s an increase in the number of impulses from the sympathetic nerves
heart rate increases because they release noradrenaline, these fibres are activated by stress and fear
what happens when there’s an increase in the number of impulses from the parasympathetic nerves
heart rate decreases because they release acetylcholine, these fibres are activated during periods of rest
why are the sympathetic and parasympathetic neves said to be antagonist
they have opposite effects on heart rate
blood pressure
the force exerted by blood against the walls of blood vessels
how is blood pressure measured
millimetres of mercury (mmHg)
how is blood pressure generated
by the contraction of the ventricles
where is blood pressure the highest
aorta and pulmonary artery
when does blood pressure change in the aorta
during the cardiac cycle
when does blood pressure increase in the aorta
ventricular systole
when does blood pressure decrease in the aorta
diastole
how do you measure blood pressure
using a sphygmomanometer
hypertension
prolonged high blood pressure when resting
what can hypertension lead to
strokes and coronary heart disease (CDH)
what causes hypertension
obesity, no exercise, high fat or salt diet, excessive drinking, continuous stress
