Week 1 Flashcards
How are cardiac muscle cells electrically coupled
Via gap junctions
What muscle type is found in the middle layer of the aorta
Smooth muscle
What does calcium do in a action potential
Removes the tropomyosin block
The nerves and ganglia that transmit action potentials to smooth muscle and cardiac muscle are part of:
Efferent division
The parasympathetic nervous system
Peripheral nervous system
Autonomic nervous system
Sequence of a reflex arc
Sensory receptor
Afferent (sensory neurone)
Interneurone
Efferent (motor) neurone
Effector organ
Postganglionic sympathetic neurones release the transmitter:
Noradrenaline
Function of CVS
Transport and exchange
Arrangement of the CVS
Right atrium- pulmonary artery- lungs- pulmonary vein- left atrium- aorta- systemic circulation- right atrium
Pulmonary artery and pulmonary vein
Artery away from heart but pulmonary artery is deoxygenated
Vein towards the heart but pulmonary vein is oxygenated
The left and right sides of the heart are in series with eachother
Output of RV into pulmonary circulation= output of LV into systemic circulation
Vascular beds
Parallel arrangement
All beds get blood with same level of oxygenation
Prevents changes in blood flow in one organ affecting flow in other organs
Blood flow in the heart
In order for blood to flow through the systemic blood vessels at a rate that ensures metabolic demand can be met, considerable pressure has to be applied to the blood
Blood flow unidirectional due to one way valves
Systole= phase of contraction and ejection
Diastole= phase of relaxation and filling
Cardiac output
Pumping activity of heart is expressed as the cardiac output CO
CO= volume of blood pumped/min = 5L/min
Determined by:
-stroke volume SV 70ml, volume ejected per contraction
-heart rate HR 70b/min
CO=SV * HR
Left CO= right CO
Pulse pressure in the aorta
Pulse pressure= systolic pressure- diastolic pressure
Diastole= 60% of total cardiac cycle
Elastic recoil maintains pressure during diastole
Mean ABP
Mean ABP= (SP-DP)/3 +DP
Eg 120-80/3 + 80= 93mmg
Pressure throughout systemic vasculature
Greatest resistance is in arterioles
Because pressure falls as move through the system- there must be resistance to flow
Blood enters right side of the heart at minimal pressure
What determines pressure in the arterial system
Resistance to blood flow
Blood volume in the arterial system
Pressure= flow * resistance
ABP= cardiac output * total peripheral resistance TPR
Total peripheral resistance TPR
Or systemic vascular resistance SVR
Is the resistance to flow offered by all systemic vasculature excluding pulmonary circulation
How do arterioles control blood flow to individuals organs
Vasoconstriction or vasodilation changes resistance therefore controls flow
Vasodilation increase flow
Vasoconstriction decreases flow
Resistance controlled by nerves, local factors, hormones
Blood vessels
Veins: very low pressure, thin walls, under control ANS, accommodate large volumes, reservoirs
Arteries: high pressure, muscular walls, elastic, conduits
Small arteries, arterioles: modest pressure, muscular walls, under influence of local factors and ANS, control flow to tissues
Capillaries: low pressure, single endothelial cell wall, exchange
Venules: low pressure, conduits
Venous return and cardiac output
Any imbalance between VR and CO (eg standing decrease VR), leads to a coordinated response so that ABP is maintained
ABP is maintained by negative feedback control
ABP= CO * TPR
(SV * HR) * TPR
Low ABP -> ANS- cardiac stimulation, vascular constriction, kidneys- increase blood volume
Increase ABP
