Cardiovascular 1 Flashcards
How does O2 move along this pathway
Ventilation -> Pulmonary O2 diffusion -> Circulatory O2 delivery -> Muscle O2 diffusion -> Muscle O2 Utilization -> Muscle ATP Turnover
How is blood circulated? How is blood distributed to all cells?
- blood motion
- The mechanics of blood motion (haemodynamics) relate mainly to the physical quantities of pressure, resistance and flow.
- Blood flows around and around and around…..in a closed circuit: it leaves the heart and returns to the heart, picking up oxygen and releasing cellular wastes, and visits every cell at all times.
Five cardiovascular responses during graded exercise
- Responses are based on ‘end-stage’ measurements during a graded test.
Five CV responses
- Cardiac output - the rate at which blood leaves the heart (flow)
- Mean Arterial Pressure - (pressure)
- Total Peripheral Resistance - (resistance)
- Heart Rate
- Stroke Volume
Cardiovascular design: Basic plan
- Four chambered mammalian heart.
- Pulmonary circuit lies ‘in series’ with the systemic circuit (see next slide).
- Blood flows in one direction.
- Arterial blood flows away from the heart.
- Venous blood flows towards the heart
Cardiovascular design: systemic and pulmonary circuits lie ‘in series’
- In series design, combined with one-way flow, ensures that all blood that flows through the lungs then flows through the systemic circulation and to all organs.
Cardiovascular design: system (regional) circuit lie ‘in parallel’
- Arterial blood will divide continually as it flows further away from the heart.
- All organs receive the oxygen-rich blood that left the lungs.
- No organ receives the carbon dioxide-rich blood leaving another organ (except the liver).
Cardiovascular output is continually divided as blood flows away from the heart
- Arterial blood will divide continually as it flows further away from the heart.
- This enables blood flow to be ‘distributed’ between the regional circulations.
And the blood then merges as it flows back to the heart
- Blood leaves capillaries via small venules and flows into small veins, medium-size veins, large veins, inferior or superior vena cava and then the right atrium.
- This venous ‘flow’ is sometimes called ‘venous return’.
- What leaves the heart, returns to the heart: blood flows in a circle!!
Distribution of cardiac output at rest
- parallel arrangement
In parallel arrangement enables cardiac output to be distributed to the regional circulations
(IMAGE)
Cardiac output and its distribution during exercise
- Increases in blood flows to heart, muscle and skin (except “maximal exercise”).
- Decreases in blood flows to GI tract and kidneys.
- Constant blood flow to brain.
How is blood circulated at a faster rate? How is the distribution of blood flow changed?
- The mechanics of blood motion (haemodynamics) relate mainly to pressure, resistance and flow.
- Physiological processes affect these mechanical aspects of motion to control the flow of blood.
Haemodynamic I: blood flow in a blood vessel
Blood flow = Pressure Difference / Resistance
Q = ∆P/R
Resistance - the friction between blood and blood vessel
Haemodynamic II: Blood flow in the systemic circulation
Heart -> organ/region -> heart
R = TPR
A sufficiently high arterial pressure is critical to enabling blood to flow in the vasular system
Interpreting cardiovascular responses during graded exercise
Flow - increases
Mean arterial Pressure - increases by 30%
Resistance - Decreases
From neuromuscular to cardiovascular: Blood flow, oxygen and endurance
- Restricting muscle blood flow reduces muscle endurance: try a fist-clenching exercise.
- This effect of blood flow on muscle endurance is thought to be mediated by oxygen (O2 ).
- Endurance at the highest of intensities depends on the use or consumption of O2 . (This doesnt make sense)
O2 and Life
Animals take O2 from the atmosphere and use it to release the energy stored in other ‘fuels’ (e.g., carbohydrate) – aerobic metabolism.
O2 pathway and processes from atmosphere to cell
- Ventilation
- Pulmonary O2 diffusion
- Circulatory O2 delivery
- Muscle O2 diffusion
- Muscle O2 utilisation
- Muscle ATP turnover
O2 consumption from the atmosphere
- V̇
- VO2
- Atmospheric O2 exists as a gas,
- The rate at which a volume of gas is used with respect to time is denoted, V̇, (L/min or L.min-1 ).
- The rate at which a volume of O2 is used (consumed) is denoted, V̇O2 .
- To sustain life, O2 must be consumed at a rate that is sufficient to sustain the most basic biological processes consistent with life.
- V̇O2 is proportional to body size (and the number of body cells).
- To function, to move, to be active, requires some biological processes to operate at a higher rate and, thus, a higher rate of O2 consumption (V̇O2 ) .
The concept and measurement of pulmonary VO2
- O2 uptake
- O2 uptake = O2 inspired – O2 expired
- V̇O2 = V̇O2 in – V̇O2out
- = (V̇air × Fo2 ) in - (V̇air × Fo2 )out
- The rate at which O2 ‘flows’ into the pulmonary circulation - V̇O2 - is, under most conditions, equal to the rate at which O2 is consumed by all body tissues.
Continuous response of O2 uptake during graded exercise
As time and workload (intensity) increases so does oxygen consumption until maximum VO2 is reached
Skeletal muscle and the heart during exercise
- Oxygen
Skeletal muscles and the heart consume more oxygen during exercise
- Skeletal Muscle (3900ml/min)
- Heart (140 ml/min)
Mitochondria during exercise
- Mitochondria consume more O2 and support increased ATP synthesis during exercise
- Mitochondria uses oxygen and a fuel to make carbon dioxide and water (waste products) as a means to convert ADP and phosphate to ATP
Scope of VO2max in humans
- Oxygen uptake & intensity
Oxygen uptake increases as a linear function of power output/intensity
