Week 5 Flashcards
What is the role of Acetylcholine in Cardiac regulation ?
- Slows heart rate by delaying sinus discharge
Name the two ways in which parasympathetic stimulation slows heart rate
- Via Acetylcholine release
- Vagus Nerve stimulation
Sympathetic nerve fibres innervate the ________ and the ________
SA node
Ventricles
Sympathetic nervous system releases __________ and activates ___________ receptors in the heart
Noradrenaline
Beta-Adrenergic
Where is the cardiac control centre ?
Medulla Oblongata
What are the two factors affecting blood flow
- Pressure gradient between the two ends of the vessel
2. Inversely to the resistance encountered to fluid flow
What are the three factors determining resistance to blood flow ?
- Blood thickness/viscosity
- Length of the conducting tube
- Vessel radius
Name local factors causing vasodilation
- decreases tissue O2
- local increase in blood flow
- Body temp.
- CO2 levels
- acidity
- NO Production
Name three factors that stimulate NO production as a result from increased blood flow
Signal chemicals
Sheer stress
Vessels stretch
What is considered a reflection of the functional capacity of the CV system ?
Cardiac Output
At rest, why does CO vary ?
Emotional conditions that alter cortical outflow to Cardioaccelorator nerves
Name two factors decreases HR in Endurance athletes
- Increased Vagal Tone
2. Decreased sympathetic drive
Name 3 factors contributing to increased stroke volume in endurance athletes
- Increased blood volume
- Increased ventricular volume
- Increased compliance of left ventricle
What 2 mechanisms aid in venous return
Skeletal muscle pump
Respiratory (abdomino-thoracic) pump
Define Cardiovascular Drift
Gradual time-dependent downward drift in several CV responses
At rest, Roughly 80% of cardiac output is distributed to where?
Digestive tract, liver, spleen, brain, kidneys
What type of muscle with receive most of the blood distribution during exercise
Fibres with higher oxidative capacity/tendencies
What is blood O2 reserve and how much is there?
Extra O2 circulating above the requirement at rest
Roughly 750 ml
A ____L increase in blood flow accompanies a ___L increase in O2 consumption
5-6 Litres
1Litre
Aterial-Venous O2 difference during exercise = ?
50ml of O2 per litre of blood perfusing tissue-capillary bed
Expanding a-VO2 functions to?
Increase O2 consumption for energy
How is a-vO2 expanded
Extracting more O2 from blood
How does arterial blood O2 concentration change during exercise
Varies little from the 200ml range
How does the mixed-venous O2 content change with exercise
Decreases progressively with increased intensity
Increased blood pressure functions to do what at the capillary?
Increased fluid, nutrient and O2 delivery
List factors increasing O2 extraction at muscle tissue during exercise (5 factors)
- CO diverted to active tissue
- other tissue temporarily decrease blood supply
- Central circulation redirected to active muscle
- Increased capillary
- Increased muscle micro circulation
True or false: arm exercise averages more O2 consumption than Leg exercise
False
Upper body Submaximal exercise produces ______ O2 consumption
(Higher or lower)
Higher
What responses are involved in CV Drift
Mainly Stroke
The cardiovascular control centre continually receives input about what four things ?
- BP
- Core body temperature
- muscle metabolism
- muscle contraction
Active muscle results in the opening of dormant capillaries, what is the function of this?
- Increase total muscle blood flow
- Large blood volume delivery with minimal increase in flow velocity
- Increase surface area for gas and nutrient exchange
Three factors regulating SV
- Preload
- contractility
- Afterload
Three factors that enhance stroke volume during exercise
- Enhanced cardiac filling and pre load
- More complete systolic emptying
- Training adaptations that increase total blood volume and reduce resistance to flow
