Lecture 16 - Circulation Part 2 Flashcards
What is pressure?
Name the following types of pressures:
- Pressure tending to distend a vessel
- Pressure differential between inflow/outflow
- Pressure caused by the height of a fluid column
P = F/A
- Transmural Pressure
- Pressure Gradient
- Hydrostatic Pressure
What is the mean arterial pressure?
Average pressure existing in the AORTA and proximal arterial system during ONE cardiac cycle
What are the components that make up Mean Arterial Pressure?
MAP = diastolic Pressure + 1/3 Pulse Pressure
What are the 2 physiologic factors of BP? The 2physical?
Physiological:
- Cardiac Output
- Peripheral Resistance
Physical:
- Arterial Blood Volume
- Arterial Compliance
What primarily determines systolic pressure?
CARDIAC OUTPUT
- changed by autonomic nervous system
What primarily determines diastolic pressure?
Total Peripheral Resistance
How is TPR & Cardiac output regulated?
TPR:
- Autonomic control
- Local Metobolic (which overrides nervous control)
- vasodilation/vasoconstriction
CO:
1. Autonomic Control
How does arterial compliance affect systolic and diastolic pressures?
- at LOW compliance
systolic INCREASES & diastolic DECREASES
- created a large Pulse Pressure
What are the 2 main determinants of TPR?
- Arteriolar Radius
2. BLOOD VISCOSITY
Baroreceptors maintain arterial BP by continuously adjusting what 2 factors?
- HR
2. Peripheral Resistance
How does the pulse pressure change with exercise?
WIDENS
- more work for the heart, BUT transient wider pulse pressure is good during exercise because it strengthens the heart
(not the same as having this problem CONSTANTLY; transient is ok)
What is sepsis?
massive vasodilation & diastolic drops out
- if all vascular beds open up all at the same time & diastolic pressure drops out
The following all decrease what?
- CHF
- Bradycardia
- Sepsis
BLOOD PRESSURE
What determines arterial compliance?
- location in arterial vasculature,
- age
- blood volume
- sympathetic tone
- pregnancy
As peripheral resistance increases, how does systolic and diastolic BP change? Which is affected more?
BOTH increase
- diastolic is affected MORE (since TPR primarily affects diastolic BP & cardiac output affects systolic)
The following are local or global responses to a decrease in Total Peripheral Resistance:
- Baroreceptor Reflex
- Hormonal (angiotensin, epinephrine)
- Sympathetic Activity (vasocontrict/vasodilate)
GLOBAL!!
What are some local affects to increase TPR?
- Myogenic Response (muscle)
- Endothelium Meditated Regulation
- Local Metabolic Changes (O2, CO2, metabolites)
Blood pressure relies on what 2 factors?
- Peripheral Resistance
2. Compliance
At HIGH peripheral resistance is diastolic pressure high or low?
HIGH
- relies on TPR
Blood viscosity works to increase what?
Total Peripheral Resistance
What 3 areas does the sympathetic system change in order to increase BP?
- Heart- increase HR - increase Cardiac Output
- increase contractility - Veins venoconstrict - increase Venous Return - increase Stroke Volume
- Arteries
- vasocontrict
- increase Total Peripheral Resistance
What are 2 ways the heart increases Cardiac Output directly & by increasing stroke volume?
- Increase Heart rate
2. Increase contraction strength (which increases stroke volume)
How does the venous system increase CO?
- Venoconstrict
- increase Venous Return
- Increase Stroke Volume
How does the arterial system increase BP?
- Vasoconstrict
- increase Total Peripheral Resistance
- Increase BLOOD PRESSURE
During exercise where is blood shunted/cut off?
- Shunted to skeletal muscle
- heart
- cutaneous (to sweat&cool down) - Cut off to VISCERA
- no pee/poo
Does pulse pressure increase or decrease during exercise?
INCREASES
- diastolic should decrease since TPR is decreasing
How does Arteriovenous Oxygen changing during exercise?
IT IS INCREASING
What occurs during anticipation of exercise?
- decrease parasympathetic nerve activity.
- increase sympathetic nerve activity.
- increased heart rate and myocardial contractility.
- continues throughout exercise
What occurs as HR reaches a maximum value?
STROKE volume declines (reduced filling time)
- but up until a point, HR increases contractility which increases Stroke volume & thus cardiac output
During sympathetic vasoconstriction, where is blood shunted away from?
- kidneys, skin, splanchnic regions & inactive muscle
cerebral, pulmonary, and cardiac unaffected
During exercise, what happens to capillaries?
CAPILLARY RECRUITMENT,
active muscle capillaries open for max blood flow
How is venous return increased? 3 ways
- sympathetic venoconstriction decreases venous compliance & shunts blood BACK to the heart
= INCREASE venous return
- Muscle Pump
- Respiratory Pump
In anticipaion of exercise, what occurs in the oxyhemoglobin dissociation curve? What does this mean?
- shifts RIGHT
- more free O2 available for skeletal muscle (not holding to hemoglobin)
- increase Arteriovenous Oxygen Difference
- OXYGEN CONSUMPTION INCREASES
Metabolites always cause what in the body? Is this a global or local control?
- always cause VASODILATION
- LOCAL control which outcompetes the global vasoconstriction (on ACTIVE muscle)
How do metabolites (adenosine, K+, CO2, and H+) change the local environment to cause vasodilation? How can they be used to break arrhythmias?
- change in pH and changes the binding affinity of hemoglobin to oxygen
- thus MORE free oxygen released to skeletal muscle
- work on same channels as Acetylcholine to INCREASE K+ permeability, allowing it to leave the cell (hyprpolarizes, moving the diastolic depolarization slope away from threshold = slow down pacemakers)
How can vasodilation be induced for people who cannot use the treadmill?
- inject adenosine
- see if VASODILATIOn occurs
(short half life)
Should diastolic pressure decrease or increase with a decrease in TPR? What should usually occur during a stress test?
DECREASE
- diastolic pressure should decrease
- thus if it INCREASES then the arteries are not vasodilating
= increase in after load
(pathology)
What usually overcomes during stimulation of both:
- Global Sympathetic
- Local Metabolic
LOCAL METABOLIC always overcomes global sympathetic
in areas that need it
What are the 3 parameters of work?
- HR
- Contractility
- Afterload
The heart & skeletal muscle VASODILATOR during exercise as a response to what?
respond to an INCREASE in WORK
- HR
- Contractility
- Afterload
What is the only area that cannot increase O2 extraction?
the HEART
- flow limitd organ, & only way to increase oxygenn is through
1. Vasodilation
2. Increase blood flow
With enhanced O2 extraction during exercise, which direction does the oxygen dissociation curve shift? What happens to Arteriovenous Oxygen Difference?
- shifts RIGHT
- so response is MORE sensitive to a change in O2/Co2 - AOD INCREASES
since arteries taking up more oxygen and veins are giving it up
Capillaries that open in skeletal muscle are a metabolic or local response?
METABOLIC response in skeletal muscle
- capillary recruitment is due to an increase in FLOW (not metabolic)
What are 2 important mechanisms that the Venous System relies on to increase Venous Return?
- Skeletal Leg Pump
2. Respiratory pump
During exercise, what are the changes to the following
- Systolic Pressure
- Diasotlic Pressure
- Pulse Pressure
- Systolic pressure - INCREASES due to increased STROKE volume (sympathetics maintaining & raise Mean Arterial Pressure)
- Diastolic - relies on TPR
- so can increase, stay constant, or decrease depending on type of exercise & mass of tissue - PULSE PRESSURE WIDENS
(since systolic pressure increases)
What is the affect of weight lifting on
- TPR
- Mean arterial Pressure
- TPR is not decreasing (no vasodilation)
- MAP is increasing (not aerobic exercise)
ex: why older people can have a heart attack during weight lifting
(map increases, TPR is still high = not enough OXYGEN)
What determines the MAP during exercise?
the type of exercise
