THE CARDIAC CYCLE AND BLOOD VESSELS
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- Created by: S14n
- Created on: 14-03-21 13:03
THE CARDIAC CYCLE
- repeated around 70 times/min at rest
- 2 phases; systole and diastole
- contraction occurs separately in the ventricles and the atria
- 2 phases; systole and diastole
- contraction occurs separately in the ventricles and the atria
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WHAT IS DIASTOLE?
RELAXATION OF THE HEART
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DIASTOLE
(1)
(1)
Blood returns to atria of heart from the pulmonary veins ( lungs) and the vena cava ( from body). when pressure exceeds that in ventricles, bicuspid and tricuspid valves open allowing blood to pass into ventricles; aided by gravity.
muscular walls of atri
muscular walls of atri
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(2)
relaxation of the ventricle causes
then to recoil and reduces ventricle pressure- causes pressure to be
lower than that in aorta and p.artery so the semi-lunar artery close.
then to recoil and reduces ventricle pressure- causes pressure to be
lower than that in aorta and p.artery so the semi-lunar artery close.
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WHAT IS ATRIAL SYSTOLE?
WHAT IS VENTRICULAR SYSTOLE?
WHAT IS VENTRICULAR SYSTOLE?
CONTRACTION OF THE ATRIA
CONTRACTION OF THE VENTRICLE
CONTRACTION OF THE VENTRICLE
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ATRIAL SYSTOLE
contraction of atrial walls, along with recoil of relaxed ventricle walls, forces remaining blood into ventricles from the atria. throughout this stage, muscle of v walls remains RELAXED
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VENTRICULAR SYSTOLE
(1)
(1)
after a short delay to allow ventricles to fill with blood, their walls simultaneously contract; increasing their blood pressure
forcing the atrioventricular valves to shut and preventing backflow into atria.
forcing the atrioventricular valves to shut and preventing backflow into atria.
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(2)
with the atrioventricular valves closed the v. pressure rises more. once exceeds that in aorta & p.artery blood is forced out the v's into these vessels.
ventricles contract forcefully creating high blood pressure to pump round body
ventricles contract forcefully creating high blood pressure to pump round body
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HOW DO VALVES CONTROL BLOOD FLOW?
(1)
(1)
- blood= kept flowing 1 direction through the heart and around the body by pressure from the heart. blood always moves from region of high pressure to low.
- valves are designed so they open whenever the difference in blood p favours movement of blood in
- valves are designed so they open whenever the difference in blood p favours movement of blood in
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(2)
- when pressure differences= reversed, valves close
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ATRIOVENTRICULAR VALVES
between left A and right V and right
V and left A. prevent backflow when contraction of V means V pressure exceeds A pressure. closure of these valves ensures when V contract, blood moves within them moves to aorta and p.artery rather than back to atria
V and left A. prevent backflow when contraction of V means V pressure exceeds A pressure. closure of these valves ensures when V contract, blood moves within them moves to aorta and p.artery rather than back to atria
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SEMI-LUNAR VALVES
in aorta and p.artery. prevent backflow into Vs when pressure in these vessels exceeds that in the Vs. this happens when elastic walls of vessels recoil increasing pressure in them. when ventricle relax inducing pressure within Vs
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POCKET VALVES
in veins ensure that when veins are squeezed/ skeletal muscles contract blood flows back towards heart rather than away.
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CARDIAC OUTPUT
is the volume of blood pumped by one V of the heart in 1 min.
measured in dm_3min_-1
and depends on
- heart rate
- stroke volume
measured in dm_3min_-1
and depends on
- heart rate
- stroke volume
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WHAT IS THE EQUATION FOR CARDIAC OUTPUT?
CARDIAC OUTPUT = HEART RATE X STROKE VOLUME
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STRUCTURE OF BLOOD VESSELS
- ARTERIES = carry blood from heart into arteriole
- ARTERIOLES= smaller arteries, control blood flow from arteries to capillaries
- CAPILLERIES= tiny vessels that link arterioles to veins
- VEINS = carry blood from capillaries back to heart
- ARTERIOLES= smaller arteries, control blood flow from arteries to capillaries
- CAPILLERIES= tiny vessels that link arterioles to veins
- VEINS = carry blood from capillaries back to heart
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STRUCTURE OF ARTERIES, ARTERIOLES AND VEINS
(1)
(1)
- all have same basic layered struc.
-tough fibrous layer (resists pressure changes inside and out)
- muscle layer ( contract so control flow)
- elastic layer (maintains blood pressure by stretching and springing back: recoiling)
-tough fibrous layer (resists pressure changes inside and out)
- muscle layer ( contract so control flow)
- elastic layer (maintains blood pressure by stretching and springing back: recoiling)
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(2)
- thin inner lining ( endothelium) that's smooth to reduce friction and thin to allow diffusion
- lumen = not a layer but the central cavity of the blood vessel where the blood flows
- lumen = not a layer but the central cavity of the blood vessel where the blood flows
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HOW DO BLOOD DIFFER FROM EACHOTHER ?
- the relative proportions of each layer. arterioles are similar to arteries, but smaller and have a larger muscle layer and lumen.
- the differences relate to what the blood vessel is needed for
- the differences relate to what the blood vessel is needed for
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ARTERY STRUCTURE
(1)
(1)
- thicker muscle layer than veins. smaller As can be constricted & dilated in order to control vol. of blood going through them
- elastic layer is thicker than veins. blood pressure in arteries needs to be high. stretches and recoils to maintain smooth hi
- elastic layer is thicker than veins. blood pressure in arteries needs to be high. stretches and recoils to maintain smooth hi
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(2)
- overall thickness of wall is large. so it resists bursting of vessel under pressure
- no valves. except in arteries leaving heart. as blood is under constant high pressure; so already doesn't tend to flow backwards.
- no valves. except in arteries leaving heart. as blood is under constant high pressure; so already doesn't tend to flow backwards.
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ARTERIOLE STRUCTURE
- muscle layer thicker than arteries. contraction of this muscle allows
constriction of lumen= restricts flow so controls movement into capillaries that supply tissues with blood.
- elastic layer thinner than arteries as blood pressure is lower.
constriction of lumen= restricts flow so controls movement into capillaries that supply tissues with blood.
- elastic layer thinner than arteries as blood pressure is lower.
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VEIN STRUCTURE
(1)
(1)
- muscle layer is thinner than arteries as they carry blood away from TISSUES so their dilation and constriction can't control flow of blood to tissues
- elastic layer is thinner than arteries as low pressure of blood won't cause burst and pressure too lo
- elastic layer is thinner than arteries as low pressure of blood won't cause burst and pressure too lo
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(2)
- overall thickness of wall is small as
there's no need for thick, pressure is too low to risk bursting. allows them to be flattened easily aiding the flow of blood within them.
- valves at intervals throughout to ensure no backflow due to low
pressur
there's no need for thick, pressure is too low to risk bursting. allows them to be flattened easily aiding the flow of blood within them.
- valves at intervals throughout to ensure no backflow due to low
pressur
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CAPILLERY STRUCTURE
(1)
(1)
- thin walls consist of mostly lining
layer, distance for diffusion is short= rapid diffusion
- narrow diameter to permeate tissues so no cell is far away from capillary and so there's a short diffusion pathway
layer, distance for diffusion is short= rapid diffusion
- narrow diameter to permeate tissues so no cell is far away from capillary and so there's a short diffusion pathway
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(2)
- lumen is so narrow that RBC are flattened against side. brings them closer to cells that they supply O2 to; reduces diffusion distance too.
- spaces between lining (
endothelial cells) that allow WBC to
escape to deal with infections within tissues
- spaces between lining (
endothelial cells) that allow WBC to
escape to deal with infections within tissues
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ARTERY FUNCTION?
transport blood rapidly under high pressure from the heart to the tissues
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ARTERIOLE FUNCTION?
carry blood under lower pressure than the arteries from arteries to capillaries.
control blood flow between arteries and capillaries
control blood flow between arteries and capillaries
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VEIN FUNCTION?
transport blood slowly under low pressure from capillaries in tissues to the heart
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CAPILLARY FUNCTION?
to exchange metabolic materials such as O2, CO2 and glucose between the body cells. flow of blood in the capillaries is much slower to allow more time for exchange of materials
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TISSUE FLUID
(1)
(1)
although capillaries are small they can't serve every cell. therefore the final journey of metabolic materials is made in a liquid solution that bathes the tissues; called tissue fluid
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(2)
-watery liquid containing glucose, amino acids, fatty acids, ions in solution and O2.
- T.F supplies all these to the tissues
- formed from blood plasma & the composition of it is controlled by various homeostasis systems, so TF provides a mostly constant
- T.F supplies all these to the tissues
- formed from blood plasma & the composition of it is controlled by various homeostasis systems, so TF provides a mostly constant
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FORMATION OF TISSUE FLUID
(1)
(1)
- blood pumped by heart passes along arteries then narrower arterioles and then even narrower capillaries. pumping heart creates hydrostatic pressure at arterial end
of capillaries. this pressure causes TF move out the blood plasma
of capillaries. this pressure causes TF move out the blood plasma
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(2)
outward pressure is opposed by:
- hydrostatic pressure of TF outside capillaries= resists outward liquid movement
- lower water potential of blood due to plasma proteins causes H2O to move back into blood within capillaries
- hydrostatic pressure of TF outside capillaries= resists outward liquid movement
- lower water potential of blood due to plasma proteins causes H2O to move back into blood within capillaries
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(3)
- combined effect of all these forces is to create overall pressure that pushes TF out capillaries at the arterial end. pressure= only enough for small molecules to go out capillaries; so leaves all cells &
proteins in blood= they're too big to cross me
proteins in blood= they're too big to cross me
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RETURN OF TISSUE FLUID TO CIRCULATORY SYSTEM?
once TF has exchanged metabolic materials with cells, it's returned to C system. most tissue fluid returns to blood plasma via capillaries:
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(1)
- loss of TF from capillaries reduces hydrostatic pressure:
- by time blood has reached venous end of capillary network its h.p is lower than that of the TF inside
- by time blood has reached venous end of capillary network its h.p is lower than that of the TF inside
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(2)
- therefore TF is forced back into capillaries by h.p outside them
- plasma= lost H2O & still contains proteins, so has lower w.p than TF
= water leaves tissue by osmosis down w.p gradient.
- TF lost most O2 & nutrients by diffusion into cells that it ba
- plasma= lost H2O & still contains proteins, so has lower w.p than TF
= water leaves tissue by osmosis down w.p gradient.
- TF lost most O2 & nutrients by diffusion into cells that it ba
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(3)
- not all TF can return to capillaries; remainder is carried back via lymphatic system.
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LYMPHATIC SYSTEM
contents of it is moved by:
- HYDROSTATIC pressure of TF that's left the capillaries
- CONTRACTION of body muscles that squeeze lymph vessels to ensure fluid inside them moves away from tissues in direction of heart
- HYDROSTATIC pressure of TF that's left the capillaries
- CONTRACTION of body muscles that squeeze lymph vessels to ensure fluid inside them moves away from tissues in direction of heart
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Other cards in this set
Card 2
Front
WHAT IS DIASTOLE?
Back
RELAXATION OF THE HEART
Card 3
Front
DIASTOLE
(1)
(1)
Back
Card 4
Front
(2)
Back
Card 5
Front
WHAT IS ATRIAL SYSTOLE?
WHAT IS VENTRICULAR SYSTOLE?
WHAT IS VENTRICULAR SYSTOLE?
Back
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