Cardiovascular Controls Flashcards
At rest CV system is responsible for
Delivery of: O2, Hormones, Nutrients
Removal of: CO2, lactic acid, other metabolic waste products
Aids in temperature regulation
Increased O2 delivery during exercise is accomplished by:
Oxygen demand by muscles during exercise is 15-25X greater than at rest
Accomplished by:
- Redistributing blood flow: from inactive organs to working skeletal muscle
- Increased cardiac output
Cardiac Output increases due to (2):
Increase HR (Max HR 220-age) - Linear Increase
Increased SV with increasing intensity - Increase then plateau at 40% VO2 max
Higher plateau in highly trained subjects
Factors that influence heart rate
Sympathetic: EPI and NOREPI
Parasympathetic: Acetylcholine
Both effect S.A. node rhythmicity
Factors that influence stroke volume
Increase in epi and norepi increase contractility and frank starling effect
Both increase force of contraction
Frank Starling Effect
Due to length tension relationship
creates more actin myosin cross bridges
increases end diastolic volume
= increase in stroke volume
Contractility Effect
EPI and NOREPI increases calcium into muscle tissue
Increases the force generation by contractile proteins through CA++
End systolic volume
Increasing contractility (increase in Ca++) Epinephrine
End diastolic volume (EDV)
fuller ventricle= greater stroke volume
Frank Starling Mechanism
Increase SV by
Increase EDV or decreasing ESV
SV and Endurance Training
EDV is increased and ESV is decreased at rest and during exercise (which is what is responsible for lower HR)
Caused by (3):
Increase in plasma volume
Increase in force of contraction
Increased contractility
Resistance Training and EDV
Changes very little
Resting HR doesnt change
Endurance + Strength Training
Increase ventricular wall thickness
This increase in mass helps maintain SV and Q during weight training activity
VO2 max=
max q (x) max a-VO2 difference
aVO2 difference
Measures difference between oxygenated blood and dexoygenated blood at the capillary (mL O2 per 100 mL of blood)
O2 extraction depends upon
O2 content of blood and uptake rate (removal from blood by tissues)
O2 removal rate depends upon (6 factors)
- Capillary Density
- Myoglobin Content
- Mitochondria Number (Volume)
- Oxidative Capacity of Mitochondria
- Muscle Fiber Type
- PO2 gradient from capillaries to tissue
Effects of training on Mitochondria
Untrained: High ADP needed to stim mitochondria
Trained: More mito to share ATP production means stim at lower ADP provides grater O2 uptake
Regulation of Local Blood Flow During Exercise
Vasoconstriction at visceral organs and inactive tissues (SNS vasoconstriction)
Vasodilation at active skeletal muscles (autoregulation)
Vasodilation effected by (7)
- Increasedtemp
- ElevatedCO2
- LoweredpH
- Adenosine
- NitricOxide
- Ions eg. Mg2 and K+ • Acetylcholine (AUTOREGULATION)
Vasoconstriction effected by (2)
• Norepinephrine • Epinephrine
Precapillary sphincters
Can be relaxed to increase local blood flow.
Capillary Recruitment
1 of every 30 or 40 capillaries is open in muscle at rest
Function of Capillaries perfusing during exercise
Increases blood flow to muscle
Reduces speed of blood flow
Increases surface area for gas exchange at working tissues.
