Cardiovascular system Flashcards
composition of blood
transport vehicle for electrolytes, proteins, gasses, nutrients, waste products and hormones.
blood composed by cells
- erythrocytes
- leucocytes
- platelets
- plasma
erythrocytes (red blood cells)
transports nutrients, oxygen, carbon dioxide, waste products and hormones to cells and organs around the body
make up 40 - 45% of blood volume known as hematocrit. contain an oxygen-carrying pigment called hemoglobin, which gives blood its red color.
leucocytes (white blood cells)
protects us from disease, by destroying invasive microorganisms and toxic substances
1% of blood volume
platelets
protects us from bleeding to death, via clotting
1% of blood volume
plasma
acts as a regulator of temperature, the water content in cells, and body pH
anatomy of the heart
- heart
- atria
- ventricles
- valves
heart
involuntary muscle with striated muscle fibers (myocardium)
own blood supply via the coronary arteries
- branches off the aorta
- has its own set of veins
atria
(left & right) receiving blood from the body. Have thin walls because they only have to pump to the ventricles
ventricles
(left & right) they are thick as they propel blood from the heart to body
valves
prevent backflow by shutting when the heart relaxed
1. atrioventricular valves (tricuspid & bicuspid/mitral)
2. pulmonary and Aortic Semilunar Valve
process
- superior vena cava
2.right atrium - tricuspid valve
- right ventricle
- pulmonary valve
- pulmonary artery
- lungs (deoxygenated gets oxygenated)
- pulmonary veins
- left atrium
- mitral valve
- left ventricle
- aortic valve
- aorta
4 chambers
- right atrium
- right ventricle
- left atrium
- left ventricle
intrinsic regulation of heart
refers to mechanisms contained within heart itself. the force of contraction produced by cardiac muscle is related to the degree of stretch of cardiac muscle fibers
extrinsic regulation of heart
refers to mechanisms external to heart, such as either nervous or chemical regulation.
- nervous regulation: baroreceptor reflex
- chemical regulation: chemoreceptor reflex
intrinsic control
- control is entirely from within the issue or organ.
- uses paracrines or properties of muscle tissue.
- also known as autoregulation or local control
extrinsic control
- control is from outside of the tissue or organ.
- uses nerves or hormones
can the heart beat on its own?
- heart is able beat spookle after being separated from the body from its owner (as seen in horror films) is not totally a product of overactive imaginations.
- hearth can actually continue to beat for a number of hours if supplied with appropriate nutrients & salts.
- this is because heart has its own specialized conduction system & can beat independently of its nerve supply.
cardiac impulses / conduction system
- start in right atrium.
- a cardiac impulse is initiated from the sinoatrial (SA) node (pacemaker).
- the impulse causes the atria to contract.
- cardiac impulse reaches and activates the atrioventricular (AV) node.
- this passes the impulse down Bundle of His (in the septum of the heart).
- bundle of his splits left and right, up around the heart (purkinje fibers).
- the impulse is spread around the walls of the ventricles causing them to contract.
- ventricles relax and the cycle starts again.
cardiac cycle
- the complete sequence of events from the beginning of one heartbeat to the beginning of the next.
- an electrical impulse is conducted through the myocardium causing cardiac cycle.
- systolic (contraction) / diastolic (relaxation) pressures in the ventricles.
nervous system
- heart is also regulated by nervous system
- hormones, ion concentration and change in body temperature will influence heart rate
- heart is innervated by parasympathetic nerves that slow its rate & sympathetic nerves that speed it up
parasympathetic nerves
innervation originates in the cardiac centers in the medulla and passes to the heart by way of the vagus nerves
- when stimulated, these parasympathetic nerves release acetylcholine, which slows heart
vagus nerves
fibers richly supply the SA and AV nodes
acetylcholine
chief neurotransmitter of the parasympathetic nervous system that contracts smooth muscles, dilates blood vessels, increases bodily secretions and slows heart rate
sympathetic
nerves that serve the heart originate in upper thoracic spinal cord and reach the myocardium by way of several nerves sometimes called accelerator nerves
accelerator nerves
supply the nodes and also the muscle fibers themselves.
when stimulated, they release norepinephrine, which increases the heart rate as well as the strength of ventricular contraction
norepinephrine (definition)
hormone that is released predominantly from the ends of sympathetic nerve fibers and that acts to increase the force of skeletal muscle contraction and the rate and force of contraction of the heart
norepinephrine
released from the adrenal medulla of adrenal glands as a hormone into blood, it’s also a neurotransmitter in central nervous system where its released from noradrenergic neurons during synaptic transmission
autonomic nervous system
- responsible for control of involuntary or visceral bodily functions.
- cardiac control system is located in the medulla oblongata of the brain and controls sympathetic & parasympathetic systems
sympathetic nervous system
- stimulates the heart to beat faster
- The receptors send impulses to cardiac control center which then sends an impulse through the sympathetic nervous system to stimulate the SA node of heart
3 receptors stimulated
proprioceptors, baroreceptors, chemoreceptors
the sympathetic nervous system
- fight or flight
- prepares the body for stress
- cortisol and adrenaline
- increases heart rate and blood pressure
- decreases digestion
parasympathetic nervous system
stimulates the SA node and heart rate decreases.
receptors pick up decreases in CO2 levels, blood pressure & muscle movement.
impulses are sent to cardiac control center.
the parasympathetic nervous system
- rest and digest
- returns the body to a calm state
- growth hormones DHEA, Melatonin
- decreased heart rate and blood pressure
- repairs the body
hormonal control
- adrenaline and noradrenaline are stress hormones.
- released by adrenal glands.
- exercise causes stress induced adrenaline response.
results of induced adrenaline
- stimulation of SA nodes, which results in increased speed & force of contraction.
- increase blood pressure due to constriction of blood vessels.
- increase blood glucose levels (glucose used by muscles for energy).
pulmonary circulation
portion of the cardiovascular system that carries oxygen-depleted blood away from the heart and to the lungs and then returns it, oxygenated, back to the heart
systematic circulation
portion of the cardiovascular system that carries oxygenated blood away from the heart and delivers it to body. Also carries deoxygenated blood after use back to heart to be reoxygenated
blood vessels
arteries, veins & capillaries
arteries
transport oxygenated blood away from heart (pulmonary artery)
veins
carry deoxygenated blood to heart (pulmonary vein)
capillaries
carry food and oxygen to tissues, carry waste away
heart rate
number of times the heart beats per minute (bpm)
stroke volume
amount of blood pumped by each ventricle per beat (liters)
= (cardiac output : heart rate)
cardiac output
amount of blood pumped from the heart in one minute (liters)
= (stroke volume x heart rate)
cardiac output
- an increase of body temperature results in lower venous return to heart, a small decrease in blood volume from sweating.
- a reduction in stroke volume causes heart rate to increase to maintain cardiac output.
- blood viscosity, if blood is thicker &more viscous, makes it more difficult to be returned back (up gravity) to heart to pick up oxygen
basal heart rate
when HR is reduced to a min (sleeping)
what does exercise do to these?
there is higher demand of oxygen, causing heart rate, stroke volume & cardiac output to increase
factors affecting heart rate
- autonomic innervation
- hormones
- fitness levels
- age
factors affecting stroke volume
- heart size
- fitness levels
- gender
- contractility
- duration of contraction
- preload (EDV)
- afterload (resistance)
preload
volume of blood received by the heart (end of systolic pressure)
STRETCH
afterload
pressure or resistance the heart has to overcome to eject blood
SQUEEZED
stroke volume
- according to how you exercise because your body needs more oxygen & nourishment, which are both received from blood.
- increases depending on type of physical activity you are doing and training level.
males vs females
- females have a higher heart rate than those of men at max.
- their stroke volume is lower than that of men at max.
- their cardiac output is lower than men at max.
young vs old
- older people have a slightly higher cardiac output than children.
- children have higher overall heart rate & lower stroke volume.
- adults have lower heart rate but higher stroke volume
trained vs untrained
- a trained person has higher cardiac output than an untrained person.
- the trained resting heart rate is lower at rest but same at max.
- the stroke volume is always higher for a trained
cardiovascular drift
- progressive increase in heart rate and decrease in stroke volume that begins after approximately 10 min of prolonged moderate-intensity exercise.
- associated with decreased maximal oxygen uptake, particularly during heat stress.
increased heat rate in cardiovascular drift
reflects an increased relative metabolic intensity during prolonged exercise in heat when cardiovascular drift occurs, which has implications for exercise prescription
increase of body temperature
results in lower venous return to heart, a small decrease in blood volume from sweating. an increase in stroke volume causes heart rate to increase to maintain cardiac output
blood viscosity
if blood is thicker and more viscous, makes it more difficult to be returned back (up gravity) to heart to pick up more oxygen
plasma volume
as you exercise, you sweat. a portion of this loss of fluid volume comes from plasma volume. This decrease in plasma volume will diminish
1. venous return
2. stroke volume
venous return mechanism
- transport of blood to right side of heart via veins
- up to 70% of the total blood volume is contained in the veins at rest.
- heart can only pump as much blood as it receives, so cardiac output is dependent on venous return
- rapid increase in venous return enables a significant increase in stroke volume & therefore cardiac output
- blood pressure is low by time blood enters veins. this means that active mechanisms are needed to help venous return
mechanisms tat help
- skeletal muscle pump
- respiratory pump
- valves
- smooth muscle
- gravity
skeletal muscle pump
when muscles contract and relax, they change shape. this change in shape means that muscles press on nearby veins, causing a pumping effect & squeezing blood towards heart
respiratory pump
when muscles contract and relax during the inspiration and expiration process, pressure changes occur in thoracic and abdominal cavities. these pressure changes compress nearby veins and assist flow of blood back to heart
valves
is important that blood in veins flows in only direction. valves ensure that this happens. once blood has passed through valves, they close to prevent flowing back
smooth muscle
there is a very thin layer of smooth muscle in walls of veins. this helps squeeze blood back
gravity
assists flow of blood from body parts above heart
venous return & exercise
- venous return must be maintained during exercise to ensure that skeletal muscles receive enough oxygen to meet the demands of activity.
- at rest, valves & smooth muscle in veins are sufficient to maintain venous return.
- demand for oxygen is greater and heart beats faster, so skeletal muscle pump & respiratory pump are required to help out.
- skeletal muscles are constantly contracting & breathing rate is elevated
- active cool-down keeps skeletal muscle pump & respiratory pump working, thus preventing blood from pooling.
blood pressure (definition)
pressure of the blood within the arteries. It’s produced primarily by contraction of the heart muscle. It’s measurement is recorded by two numbers
- systolic
- diastolic
systolic blood pressure
- force exerted by blood on arterial walls during ventricular contraction.
- top number, which is also the higher of the two numbers
diastolic blood pressure
- force exerted by blood on arterial walls during ventricular relaxation.
- bottom number, which is also the lower of the two numbers
smooth muscle
involuntary control of smooth muscle inside circulatory system.
if all of this smooth muscle relaxed then there would not be sufficient pressure to return blood to heart.
nervous & cardiovascular system
they interact so there is sufficient relaxation of some vessel walls & contraction of others to ensure that enough blood is getting to all organs requiring exchange, yet blood is maintained.
bottom line
as muscles work harder, blood pressure will go up to meet the demands of muscles needing more blood
changes in diastolic & systolic BP
we see little or no change in diastolic blood pressure during cardiovascular exercise.
we see a normal increase in systolic blood pressure.
during resistance exercise we see an increase in both
changes are different depending on static or dynamic exercises
static exercise
defined as a sustained contraction of a muscle group where muscle is contracted but there is no change in muscle length
why does systolic blood pressure increase?
volume of blood + contraction rate a larger amount of blood is being pumped through arteries with each contraction
why does diastolic blood pressure increase?
- pressure on the arterial walls is increased even during relaxation.
- vasocontriction creates an increase in pressure.
- muscles squeeze veins to promote venous return, by doing so increases pressure
- during static exercise, breathing is more constricted, there is less oxygen & more carbon dioxide, heart must work harder to pump blood it does have to supply muscles with sufficient oxygen to continue static exercise
dynamic exercise
if you are moving a joint during an exercise
why does systolic blood pressure increase at a lower rate?
breathing frequency is much higher than in static exercise therefore pressure is not as high as during static exercise
why does diastolic blood pressure remain the same?
- muscles are moving constantly, no added pressure on constant contraction.
- you are constantly breathing, which allows carbon dioxide to be quickly expelled.
- arteries are dilated as vasodilation is occurring
heart adaptation
- myocardium increases in thickness.
- left ventricles internal dimensions increase
stroke volume
- increase in size of heart enables the left ventricle to stretch more & thus fill with more blood.
- the increase in muscle wall thickness also increases contractility resulting in increased stroke volume at rest & during exercise, increasing blood supply to the body
resting heart rate
as stroke volume increases cardiac output can remain constant, therefore enabling resting heart rate to be lower
cardiac output
- increases exponentially during maximal exercise because of increases stroke volume.
- this results in a greater oxygen supply, waste removal & hence improved endurance performance
muscular adaptations
- increased capillarization of trained muscles
- improvements in vasculature efficiency
blood
- resting blood pressure decreases as a result of improved cardiovascular factors.
- increase in blood plasma.
- red blood cell volume & hemoglobin
maximal oxygen consumption
represents functional capacity of oxygen transport system & is sometimes referred to as maximal aerobic power or aerobic capacity
fitness
can be measured by volume of oxygen you can consume while exercising at your maximum capacity
VO2 max
maximum amount of oxygen in milliliters, one can use in one minute per kilogram of body weight
fitter have higher VO2 max
how can you increase you VO2 max
numerous studies show that you can increase your VO2 max by working out at an intensity that raises your heart rate to between 65 and 85% of its maximum for at least 20 minutes three to five times a week
factors affecting VO2 max
- chemical ability of muscular cellular tissue system to use oxygen in breaking down fuels.
- combined ability of cardiovascular & pulmonary systems to transport oxygen to muscular tissue system
