Heart Flashcards
Lumen
Central cavity
Endothelium
Smooth preventing friction
Elastic layer
Maintains blood pressure by recoiling
Muscle layer
Contracts to control flow of blood
Tough outer layer
Resists pressure within and outside
Thin endothelium
Short diffusion pathway for exchange
Plasma rbc wbc and platelets percents
55% plas
45% rbc
1% plat and wbc
What kind of system is the heart
Myogenic
Cardiac cycle
Controlled by the hearts electrical system, capable of working without input from ns
Describe how a heartbeat is initiated and coordinated
-SA node sends impulses to atrium stimulating contraction
-non conductive tissue prevents immediate contraction of ventricles/prevents impulses reaching ventricles
-AVN delays impulse when blood leaves atria filling ventricle
-AVN sends impulses down the bundle of his
-v contract from base up
Factors affecting O2 dissociation
Location ^ altitudes = lower pp 02 shifts left
Activity. ^ co2 = shifts right
Size lower size= ^ metabolism = shifts right
Systole
Contracts
Vol decrease
Press increase
Diastole
Relaxed
Co operative binding
As o2 loads to oxygen
The binding causes the hb to change shape
This makes loading more oxygen easier
Until all haem groups are occupied and hb is saturated
Dissociation and po2
Lungs vs respiring tissues
Hb has a higher affinity for o2 so it loads easier in the lungs/close to 100% saturated
In respiring tissues the saturation is low so o2 dissociâtes easily as o2 has a lower affinity for O2
Bohr shift
Excersizing/ high metabolism organisms (small)
CO2 is acidic denaturing hb reducing affinity of o2 to hb
Tissues with lots of respiration o2 = easily unloaded so curve moves right as it’s easier to replace o2
Explain how tissue fluid is formed and how it may be returned to the circulatory system [6]
• High Pressure caused by the ventricles contracting
• High hydrostatic pressure at the arteriole end of the capillary
• Water (and dissolved substances) are forced out (into the tissue) reject plasma/blood
• Large proteins remain in the blood
• Water potential increases in the tissue/decreases in the capillary
• Water enters at the venule end by osmosis
• Excess fluid is drained/absorbed into the lymph
• Lymph returns the fluid to the circulatory system
Artery structure
Thick muscle layer – can control blood flow through constriction/dilation (only in smaller arteries/arterioles)
• Thick elastic layer – for elastic recoil/smooths blood flow
• Overall thick wall – to withstand high pressure form the
heart
• No valves – not needed as pressure is high
Arterioles
• Similar to arteries but:
• Muscle layer is proportionally thick so blood flow
can be controlled.
• Elastic layer is thinner than arteries as blood is lower pressure
Veins
• Thin muscle layer – blood flows away from tissues, doesn’t need to constrict
• Thin elastic layer – low pressure so no recoil
• Overall thin wall – blood is at low pressure
• Valves – to ensure no back flow of blood as pressure is low. Muscle contraction pushes blood through the valves
Capillaries
• Thin/Endothelium only – short diffusion distance
• Very branched – large surface area
• Narrow lumen – red blood cells squeezed against endothelium short diffusion pathway
• Narrow diameter – permeate tissues
• Gaps between endothelium – substances can move in and out
Relaxation of the heart (diastole)
• Blood returns to the atria of the heart through the pulmonary vein (lungs) and vena cava (body).
• The filling of blood in the atria increase the pressure and forces the AV valves open.
• Pressure is higher in the aorta and the pulmonary artery than in the ventricles so SL valves close
Contraction of the atria (atrial systole)
• Atria (atrial walls) contract
• Pushing the remaining blood into the ventricles
• Ventricles remain relaxed and recoil
Contraction of the ventricles (ventricular systole)
• The atria relax and after a short delay the ventricles fill with blood.
• The walls of the ventricles contract and the pressure increases forcing the AV valves to shut. Preventing backflow.
• The pressure increases in the ventricles and becomes higher than in the aorta and pulmonary artery – so SL valves open
• Blood is pushed away from the heart through pulmonary arteries and aort
pLV > pLA
ATRIOVENTRICULAR VALVE CLOSES
pLV > pAorta
SEMILUNAR VALVE OPENS
pAorta > pLV
SEMILUNAR VALVE CLOSES
pLA >pLV
ATRIOVENTRICULAR VALVE OPENS
