Circulatory 3 Flashcards
Transmural pressure
Pressure tending to distend or collapse a vessel - total pressure pushing on the vessel wall
Pressure gradient
Pressure differential between inflow and outflow
Hydrostatic pressure
Pressure caused by the height of a fluid column (due to gravity)
Mean arterial pressure
Average pressure existing in the aorta and proximal arterial system during one cardiac cycle
Equation for mean arterial pressure
Diastolic pressure + 1/3 pulse pressure
OR
2/3 diastolic + 1/3 systolic
Physiological factors affecting mean arterial pressure
Cardiac output
Peripheral resistance
Physical factors affecting mean arterial pressure
Arterial blood volume and arterial compliance
Cardiac output as a physiological factor
Primarily affects systolic pressure; regulated by autonomic nervous system
Peripheral resistance as a physiological factor
Primarily affects diastolic pressure; also regulated by the ANS, but local metabolic activity overrides nervous control
Baroreceptor reflex
Acts via the autonomic nervous system to affect both cardiac output and peripheral resistance
Exercise’s effect on blood pressure
Systolic pressure increases and diastolic pressure remains constant or decrerases
MAP during exercise
Pulse pressure widens due to increase in systolic and steady state/decrease of diastolic, thereby increasing the MAP
Disease’s effect on blood pressure
Congestive heart failure, infarction, bradycardia, and sepsis all decrease blood pressure.
Arterial compliance as a physical factor
Affects both systolic and diastolic pressures; determined by location in vasculature, age, blood volume, sympathetic tone, and pregnancy
Blood volume as a physical factor
Affects stroke volume and arterial compliance
For things that happen in anticipation of exercise
- Decrease of parasympathetic nerve activity
- Increase sympathetic nerve activity
- Increased heart rate and myocardial contractility
- Continues through exercise
Four things that happen with sympathetic activity to the heart
- Increased heart rate
- Increased contractility
- Increased cardiac output
- As heart rate reaches maximum, stroke volume declines due to decreased filling time
From where is blood diverted during sympathetic vasoconstriction?
Skin
Kidneys
Splanchnic regions
Inactive muscle
Vascular resistance during sympathetic stimulation
Increases due to vasoconstriction
Which type of vasculature remains unchanged during sympathetic stimulation?
Cerebral, pulmonary, and cardiac
Compounds involved in metabolic vasodilation
K+, adenosine, CO2, and hydrogen ion
What is the effect of metabolic vasodilators?
Lowers vascular resistance and increases blood flow 15-20 fold
Where does metabolic vasodilation take place?
In metabolically active skeletal muscle and heart
What is total peripheral resistance dependent upon?
Level of exercise and mass of active muscle
Capillary recruitment
Active muscle capillaries all open for maximum blood flow
Enhanced oxygen extraction
Rightward shift in oxyhemoglobin dissociation curve, since less oxygen is held by hemoglobin and more oxygen unloads into the skeletal muscle
What affect does enhanced oxygen extraction have on the AV oxygen difference?
Increases it
Where can enhanced oxygen extraction not take place?
In the heart
Sympathetic venoconstriction
Decreases venous compliance and shunts blood back to the heart
Muscle pump
Working skeletal muscles compress veins and shunt blood back to the heart through one-way venous valves to increase venous return
Respiratory pump
During deep inspiration, negative intra-thoracic pressure and positive intra-abdominal pressure create a pressure gradient that increases venous return
How is systolic pressure mainly increased during exercise?
By the increase in stroke volume
What else contributes to maintaining and raising mean arterial pressure during exercise?
Sympathetic vasoconstriction
How is diastolic pressure primarily determined? During exercise?
By changes in total peripheral resistance; depending on the level of exercise and mass of active tissue, it could rise slightly, stay the same, or even decrease
