Cardiovascular Physiology Flashcards
The cardiovascular system divides into the
Heart and blood vessels
bulk flow
All components of blood flow together
Highly efficient exchange of nutrients, oxygen and metabolic waste occurs between cells and regional capillaries
• Mediated by
Starling Equilibrium
Small proportion of blood is in the __________ at any given time
capillaries
Cell/capillary interface is the
powerhouse of the circulatory system
• tremendous feat of nutrient/oxygen supply, hormone delivery & waste removal
Organization of the Cardiovascular System
- closed circulation
Two circuits: - pulmonary circulation
- systemic circulation
- arteries: carry blood away form heart
- veins: carry blood back to heart
Systemic Circulation
• Blood moves into the aorta from the left ventricle
• Aorta branches successively into main
arteries supplying organ systems
• Further branching into arterioles and then
capillaries
- Venules coalesce to form progressively larger veins
- Veins draining the organ systems join into the inferior and superior vena cava
- Blood then moves into the right atrium
Pulmonary Circulation
- Blood moves from right ventricle through the pulmonary trunk – divides into two pulmonary arteries
- Blood returns to the heart via 4 pulmonary veins to enter the left atrium
Where do lung receive all blood form?
Right ventricle
As blood passes through capillaries, it is
Oxygenated
There is lower oxygen levels in
Systemic venous blood (and pulmonary arterial blood)
Each organ system received blood form the
Left ventricle
Hepatic portal system
• Sometimes organs obtain blood secondhand form another organ. Supports the unique functions for the organs. Liver part of the largest portal system. Transport blood, nutrient, and hormones.
Hemodynamics
Relationship between blood pressure, blood flow, and vascular resistance
Pressure gradients
- drives flow of blood form one region to another
- blood flow always form a region of higher pressure to lower pressure
Hydrostatic pressure
Blood contained within vessel excerpts a force
- origin of blood pressure is force generated by heart contractions
Determinants of blood flow
- Differences in pressure between two points determines blood flow
- pressure gradient
- measured blood flow in L/min (F)
Formula for blood flow
Flow = (pressure)/(resistance)
Flow direct with pressure, inverse with resistance
3 determinants of resistance
- viscosity (direct)
- vessel length (direct)
- vessel radius (inversed)
Viscosity varies with
Hematocrit, protein
Vessel length is relatively
Constant, doesn’t control vascular resistance
________ the most important regulator for vascular resistance
Radius
Radius is very
Dynamic and changes a lot
Heart muscle called
Myocardium
Heart is enclosed by
epicardium and pericardium
Layers of the heart layered by the
Endothelium
Atrioventricular valves have
One way flow to prevent flooding
As valves open when the
Pressure is higher in the atrium compared to the ventricle
When ventricle pressure rises during contraction, the Av valves
Close
Blood only moves form atrium ton
Ventricle
Valves tethered to papillary muscles by
Chordate tendinae
Right ventricle separated form the pulmonary trunk by the
Pulmonary valve (blood flows into pulmonary circulation)
Left ventricle separates form the aorta by the
Aortic valves (blood flows into the systemic circuit)
What determines whether the valves are open or closed
Pressure gradient
Properties of valves
- low resistance to blood flow
- small pressure gradient can facilitate large flow
Are there other valves at other entries of the heart
No
Without valves, in some openings, how is back flow prevented?
Atrial contraction partially occluded the blood entry points, high resistance
Cardiomyocytes comprise cardiac muscle that
Never rest and are arranged in layers
Electrical Excitability of Cardiomyocytes
Generated ATP, Ca2+ enters cytosol, activates actin myosin cross-bridge formation
Other types of cardiac cells are required for cardiomyocyte function in the conduction system:
- electrical contact with cardiomyocyte
- through gap junctions
Parasympathetic
- inner age cells in atria
- release Ach
Sympathetic
- entire heart
- release NE
Parasympathetic travelling via
vagus nerves
Blood within the chambers dont
Supply cardiac tissue directly
Coronary arteries branch form the
aorta behind the aortic valve cusps
- supplies myocardium within coronary blood flow
Venous blood collects in the
Coronary sinus, blood flows into the right atrium
The heart is essentially two pumps in that
The left and right pump simultaneously
Atria must contract first to fill ventricles, then the ventricles must
rapidly contract to pump blood to pulmonary and systemic circulation
Cardiac muscle contraction stimulated by
Plasma membrane depolarization, APs transmitted across all cells by gap junctions
Initial depolarization originates form the
SA node, then spreads through atria, then into the ventricles last
SA node is pacemaker for heart, depolarization generates AP which is then coupled with
Cardiac muscle contraction, SA node discharge thus determines heart rate
Rapid conduction form the SA node ensures contraction
Of both atria
Modified cardiac cells comprise the
AV node and dont contract
Where do AP move form ?
Form the SA node to the AV node via intermodal pathways
AV node links
atrial and ventricular depolarization (base of the atrium)
AV node conducts slowly, permitting completion of
Atrial conduction before the ventricular contraction
Purkinje fibres rapidly conduct AP to
- Ventricular myocytes
- Purkinje fibres have large diameters and low resistant gap junction
Purkinje fibres cause simultaneous depolarization of all
left and right ventriclular cells, permits coordinated contraction begins at the apex, spreading upwards
Cardiac cell types feature different ion channels, determining the
Shape of the AP
3 main ion channel mechanisms of pacemaker potential
- slow decrease in K+ permeability
- funny Na+ channels
- T-type Ca+ channels
