Week 4 - Intro to Cardiovascular Physiology Flashcards
What is the role of the cardiovascular system?
The role of the cardiovascular
system is to provide a mass
transit system to move materials
around the body and an exchange
surface for movement of materials
into and out of the vascular space.
Mass transit to and from cells*
Total body water can be divided into intracellular water (~66%)and extra-cellular water (~33%).
The extracellular water can be divided
into interstitial water and plasma
water. Total blood volume ~5 liters
Adults 60-65% water
Babies 80% water
Hematocrit
vs
Plasma
The cellular portion of blood about 40%
The rest is the liquid form, plasma, 60%
Total blood volume is 5 L
Pulmonary and systemic circulation arrangement
The pulmonary circulation and the systemic circulation are arranged in series.
Systemic organs represent individual circulations arranged in parallel. This allows
blood flow to individual systemic organs to be independently controlled.
Heart is in Series with lungs*
Rest of body is in parralell with heart and lungs*
This is important.. because we can have major changes in a single body system without a huge overall change in the body…
Parallel structure in the systemic orgains allows for individual control of eacy organ* Very important
What determines fow through a system?
- Flow through a tube (or system of tubes) is directly proportional to the pressure difference across the tube and inversely proportional to the resistance offered by frictional forces at the surface
- Must have a pressure difference to create flow*
- FLOW = deltaP / R
- Resistance also effects flow (cells in the blood, cell wall)
- Blood flow is fastest in center of vessel and zero at the wall
- Collective crossectional area gets bigger as we get farther from the heart..so.. event though the radius is much smaller in the capilaries the total cross sectional area is much larger
What is the basic flow equation?
units of volume/time
How is flow and resistance applied to cardiovascular system?
Flow:
Resistance:
MAP
CO
TPR
Output of right heart is equal to ouput of left heart*
- Flow through the circulation is equal to the cardiac output from heart pump.
- Right and left heart output are equal… i.e., the cardiac output (CO).
- Resistance in the circulation is a result of frictional forces as blood passes hrough the consecutive segments (artery, arteriole, capillary, veins) …and is called the” total peripheral resistance” (TPR)
Basid flow equation can be rearranged to:
delta P = MAP because MAP - CVP = MAP - 0.. central venous pressure is essentially zero. Q = CO, R = TPR
MAP = CO X TPR
where MAP is the CONTROLLED variable (by CNS)
MAP is usualy about 100 mmHg
SO… if MAP falls, the CNS will either increase CO, TPR or both!* and CO = SV X HR so one of these will increase!
Cardiac Anatomy
Describe the flow of blood through the heart
How to determine Cardiac Output?
Ventricular systole vs diastole
Which valves are closed, which muscles are contracted/relaxed?
What are heart sounds from?
Lub and Dub
First sound, Lub, is from the closure of the AV valve*
If have stenoic AV valve (aortic stenosis).. then you would have a murmer from turbulent flow leaving the left ventricle
Second sound is from mitral valve closing.. (arterial pressure is higher than left ventricular pressure.
www.blaufuss.org/turorial/index1.html
What are the excitable properties of the heart?
Excitable Properties of the Heart
- Heart rate is normally set by SA nodal cell firing spontaneously.
- All cardiac muscle cells are activated by the spread of action potentials from cell to cell.
- Conduction pathways follow preferred pathways with variable conduction velocity.
Parasympathetic vs sympathetic stimulation of SA node control heart rate
So a pts blood pressure is low.. what could it be?
Either their cardiac output is low OR their total peripheral resistance is low. Period.
Now ask why/how could this happen.
Peripherial Vasculature
ateries
arterioles
capillaries
veins
Arteries - conduit vessels
Arterioles - Resistance vessels (resistance of flow is highest here) Smooth muscle controls the diameter of the arterioles
Capillaries - Exchange vessels
Venules - collect blood from capillaries (have one way valves*)
Veins - Capacitance vessels (have one way valves*)
Aortic pressure (MAP - 100mmHg)
Vena Cava pressure - 0 mmHg
What is the controlled variable in the cardiovascular system?
Short term control
Long term control
MEAN ARTERIAL PRESSURE (MAP)
- As long as mean arterial pressure is controlled (at about 100 mmHg), brain blood flow will be sufficient. The status of CV variables (i.e., HR, SV, CO, TPR) are irrelevant as long as the brain is perfused.
- Short-term (acute) control of arterial pressure depends primarily upon the operation of the arterial baroreceptor reflex.
- Long-term (chronic) control of arterial pressure depends primarily on control of blood volume which depends upon the operation of the kidneys.
Arterial Baroreceptor Reflex
sensor
afferent signals
integrating center (compare to set point)
efferent signals
effectors
Difference in parasympathetic vs sympathetic regulation
Sensor - barorecetors
Aferent signals - action potential from sensor to medulla
integrating center - medulla
efferent siganls - action potentials to effectors
effectors are arterioles
What happens when a person stands…
Know the controls
