cardiovascular system Flashcards
myogenic
capacity of the heart to generate its own impulses
sinoateial node
small mass of cardiac muscle located in the right atrium that generates a heart beat (pacemaker)
atrioventricular node
this node relays the impulse between the upper and lower chamber of the heart
systole
heart contracts
bundle of his
collection of heart muscle fibres that transmit electrical impulses from the av node via bundle branches to the ventricles
purkinje fibres
muscle fibres that conduct impulses in the walls of the ventricles
where are chemoreceptors found
carotid arteries and aortic arch
what do chemoreceptors do
sense chemical changes, during exercise they detect an increase in co2 in the blood this stimulates the sympathetic nervous system which means the heart will beat faster
where are proprioceptors found
muscles tendons and joints
what do proprioceptors do
at start of exercise, they detect an increase in muscle movement, an impulse is sent to the medulla oblongata which then sends an impulse through the sympathetic nervous system to the sa node to increase the heart rate, when parasympathetic nervous system is stimulated the sa node heart rate increases
what do baroreceptors do
respond to the stretching of the arterial wall caused by changes in blood pressure
establish a set point for blood pressure, any fluctuation from this results in them sending signals to the medulla oblongata
increase in arterial pressure means an increase in stretch of baroreceptors means a decrease in heart rate.
hormonal control mechanism
hormones effect heart rate
adrenaline is a stress hormone released by the sympathetic nerves during exercise
stimulates the sa node to increase speed and force of contraction and therefore increasing cardiac output.
cardiac conduction system
an electrical signal in the sinoatrial node starts the heartbeat
The electrical impulse spreads across the atria in a wave of excitation
The atria contracts and blood is forced through to the ventricles
The electrical impulse passes through the av node
The AV node delays the transmission for approximately 0.1 seconds to enable the atria to fully contract before ventricular systole begins
The electrical impulse passes down specialised fibres which formed the bundle of his in the septum
The bundle of Hess branches out into two bundle branches and then moves into smaller bundles called Purkinje fibres which spread throughout the ventricles
The ventricles contract and blood is forced up and out of the heart
what does the neural control mechanism involve
Involves the sympathetic nervous system and the parasympathetic nervous system
parasympathetic nervous system
Returns the heart to resting level
sympathetic nervous system
stimulates heart to beat faster
nervous system
CNS (brain and spinal cord)
PNS (nerve cells that transmit electrical impulses info to and from the nervous system
CNS
coordinated by medulla oblongata
venous return
The volume of blood returning to the heart via the veins
ejection fraction
The percentage of blood pumped out by the left ventricle per beat
cardiac output
The volume of blood pumped out by the heart ventricles per minute it is equal to stroke volume times heart rate
heart rate
number of times the heartbeats per minute
cardiac hyper trophy
The thickening of the muscular wall of the heart so that it becomes bigger and stronger
stroke volume
The volume of blood pumped out by the heart ventricles in each contraction average resting value is 70 ML
bradycardia
A decrease in resting heart rate to below 60 BPM
starlings law
increased Venous return creates greater diastolic filling which leads to an increased ejection fraction
health
A state of mental physical and social well-being and not merely the absence of infirmary or disease
fitness
When an individual is able to meet the demands of the environment
how is a heart attack formed
coronary arteries become narrow
unable to deliver enough oxygen to the heart
pain and discomfort occurs
If an arothema breaks off in the coronary artery, it can cause a blood clot
Results in a blockage
This can cut off the supply of oxygenated blood to the heart resulting in a heart attack
blood pressure
Force exerted by the blood against the blood vessel wall
what does regular exercise do to blood pressure
lowers your blood pressure and helps you maintain a healthy weight
Lowers your chance of stroke by 27%
bad lifestyle choices
diet
smoking
lack of exercise
work life balance
overtraining
lack of sleep
alcohol and drugs
stroke
occur when blood supply is cut off causing damage to brain cells so they die
Leads to brain injury, disability or death
2 types of stroke
ischamic: blood clot stops the blood supply
haemorrhaging: weakened blood vessel supplying brain burts
HDL
high density lipoproteins
transport excess cholesterol in the blood back to the liver where it is broken down
Good cholesterol since they lower risk of developing heart disease
LDL
low density lipoproteins
Transport cholesterol in the blood to tissues and classed as bad cholesterol as linked to heart disease
angina
pain and discomfort
atheroma
fatty deposit that breaks off and causes a blood clot
what does stroke volume depend on
venous return increases so will stroke volume
elasticity of cardiac fibres, the more they stretch the greater the force of contraction will be and then it will increase ejection fraction (starling law)
stroke volume in response to exercise
will increase as exercise intensity increases
but only up to 40-60% of max effort after it plateaus
as heart rate is near max so results in shorter diastolic phase
cardiac output in response to exercise
increase as exercise intensity increases until reached max intensity then it plateaus
avo2 difference
difference in the 02 content between arterial blood arriving at the muscles and the venous blood leaving the muscles
cardiovascular drift
occurs after 10 mins of exercise
heart beat rate increases and stroke volume fraction decreases
warm conditions
caused by fluid lost as sweat and reduction in plasma and blood and increased blood viscosity
reduced venous return
starlings law occurs
heart rate increases to maintain cardiac output
pre hypertension
120-139/80-89 mmhg
hypertension
140/90 mmhg or higher
venous return mechanisms
gravity
muscle pump
respiratory pump
smooth muscle
pocket valves
suction pump of the heart
gravity
helps blood return to the heart from upper body
muscle pump
when muscles contract and relax they change shape
they press on nearby veins and cause a pumping effect
the squeezes blood towards the heart
respiratory pump
when the muscles contract and relax during breathing in and out, pressure changes occur in the thoracic cavity and abodmoninal cavity
these changes in pressure compress the nearby veins and assist blood return to the heaty
pocket valves
valves ensure blood flows one way
smooth muscle
thin layer of smooth muscle in the walls of the veins and helps squeeze blood back to the heart
plasma
fluid part of the blood that surrounds blood cells and transports them
haemoglobin
iron containing pigment found in rbc which combines with oxygen to form oxyhaemoglobin
myoglobin
iron containing pigment in slow twitch muscle fibres and stores o2 in muscle fibres
mitochondria
respiration and energy production occur here
bohr shift
increase in co2 and decrease in ph results in reduction for the affinity of haemoglobin for oxygen
ph
measure of acidity
vasodilation
widening of blood vessels to increase blood flow to the capillaries
vasoconstriction
narrowing of the blood vessels to reduce blood flow to the capillaries
