Podcast
Questions and Answers
What is the primary factor that determines cardiac output during exercise?
What is the primary factor that determines cardiac output during exercise?
Which of the following accurately describes the relationship between VO2 and exercise workload?
Which of the following accurately describes the relationship between VO2 and exercise workload?
What is the primary role of the cardiovascular system during exercise?
What is the primary role of the cardiovascular system during exercise?
In terms of complexity, how does the systemic circulation compare to the pulmonary circulation?
In terms of complexity, how does the systemic circulation compare to the pulmonary circulation?
Signup and view all the answers
What physical mechanism primarily increases oxygen extraction from blood during exercise?
What physical mechanism primarily increases oxygen extraction from blood during exercise?
Signup and view all the answers
How does the body primarily accommodate increased oxygen demand in active muscles during exercise?
How does the body primarily accommodate increased oxygen demand in active muscles during exercise?
Signup and view all the answers
Which of the following factors is primarily responsible for mediating extrinsic control during exercise?
Which of the following factors is primarily responsible for mediating extrinsic control during exercise?
Signup and view all the answers
In terms of cardiovascular response to exercise, how does blood flow redistribution occur?
In terms of cardiovascular response to exercise, how does blood flow redistribution occur?
Signup and view all the answers
What defines the balance of intrinsic and extrinsic control over blood flow to tissues during exercise?
What defines the balance of intrinsic and extrinsic control over blood flow to tissues during exercise?
Signup and view all the answers
How does the duty cycle during heavy exercise compare to at rest?
How does the duty cycle during heavy exercise compare to at rest?
Signup and view all the answers
What factor primarily indicates the stroke volume response during exercise?
What factor primarily indicates the stroke volume response during exercise?
Signup and view all the answers
How does stroke volume change across exercise time in athletes?
How does stroke volume change across exercise time in athletes?
Signup and view all the answers
In which scenario is stroke volume expected to be the least affected?
In which scenario is stroke volume expected to be the least affected?
Signup and view all the answers
What change occurs in heart rate response at maximal exercise intensity for untrained individuals?
What change occurs in heart rate response at maximal exercise intensity for untrained individuals?
Signup and view all the answers
Which of the following statements about cardiac output is true during maximal exercise?
Which of the following statements about cardiac output is true during maximal exercise?
Signup and view all the answers
Study Notes
Cardiovascular System Structure and Function
- Two systems in series: pulmonary and systemic
- Both have arteries, arterioles, capillaries, venules, and veins
- Systemic system is more complex
- Primarily responsible for transport:
- Pumping blood
- Oxygen delivery to cells and tissues
- Removing waste products
- Heat regulation
- Transporting hormones
- Immune functions
Cardiovascular Response to Exercise
- Increased oxygen demand during exercise is met by:
- Local vessel dilation due to increased metabolites
- Increased cardiac output
- Redistribution of blood flow to active muscles
- Increased oxygen extraction from blood in those muscles
- Flow to each tissue is a result of intrinsic and extrinsic control
- Intrinsic control is inherent to the organ
- Extrinsic control comes from outside the organ (nervous and endocrine systems)
The Heart & Cardiac Cycle
- Anatomy: Right and left ventricle, atria, valves
- Electrical properties:
- Autorhythmicity: heart can control its own heart rate
- Long action potential: allows for separate contractions
- Electrical conduction system: transmits electrical signals through the heart
- Myocardial structure:
- Oxidative fiber type: utilizes oxygen efficiently
- High mitochondrial density: provides energy for contractions
- Primarily uses free fatty acids at rest
- Uses lactate under hard exercise
- Systole: contraction phase
- Diastole: relaxation phase
- Isovolumetric phases: short periods of no volume change
- Duty cycle: time spent in systole versus diastole
- Rest: 0.3 sec systole, 0.5 sec diastole
- Heavy exercise: 0.2 sec systole, 0.13 sec diastole
Cardiovascular Adjustments to Exercise
- VO2 (oxygen consumption) rises linearly with power output
- Cardiac output rises linearly with VO2
- Aerobic power and fitness depend on the ability to:
- Increase cardiac output
- Carry arterial oxygen
- Redistribute blood flow to active muscles
- Extract oxygen from blood in those muscles
Sex and Fitness Differences in Cardiac Output
- Sedentary men have higher cardiac output than women
- During submaximal exercise, women have 5-10% higher CO, but carry 10-15% less hemoglobin
- During maximal exercise, men have 20% higher max CO - Untrained men can increase CO 4-5 times - Trained men can increase CO 6-8 times
Stroke Volume
- Factors that affect stroke volume:
- Time
- Exercise intensity
- Fitness level
- Hydration/temperature
Stroke Volume Response to Exercise Time
- Rapid increase in stroke volume that plateaus over time
- Athletes have a larger increase in stroke volume
- Smaller increase with arm exercise due to higher blood pressure
- Decrease in stroke volume with dehydration and heat stress due to decreased central blood volume
Stroke Volume Response to Exercise Intensity
- Athletes have higher stroke volume at rest and throughout exercise
- Untrained individuals maintain increased stroke volume up to about 50% VO2max
- Athletes maintain increased stroke volume up to about 100% VO2max
Determinants of Stroke Volume in Exercise
-
End Diastolic Volume (Preload):
- Influenced by venous return
- How much blood is returning back to the heart?
- Blood volume is an important determinant
- Influenced by hydration and training
-
Contractility:
- Frank-Starling mechanism: heart operates below optimal length, increased contractility with increased end diastolic volume
-
Mean Arterial Pressure (MAP):
- Afterload: resistance the heart pumps against
Heart Rate
- Factors that affect heart rate:
- Time
- Exercise intensity
- Fitness level
- Sex
Heart Rate Response to Exercise Time
- Rapid increase in heart rate that plateaus over time
- Due to decreased parasympathetic activity and increased sympathetic activity on the SA node
- Athletes have a much smaller increase in heart rate
- Greater increase in heart rate with arm exercise due to increased sympathetic activity
- Increase in heart rate with dehydration and heat stress due to decreased central blood volume
Heart Rate Response to Exercise Intensity
- Rises linearly up to 100% VO2max
- Untrained individuals have higher resting and exercise heart rates
- Untrained individuals have a steeper rise to maximal heart rate
- Athletes reach a similar maximal heart rate, but at a much higher workload
Control of Heart Rate
- Initially due to withdrawal of parasympathetic activity
- Later due to increased sympathetic activity
- The balance of these two systems determines heart rate
- Sympathetic activity increases with exercise intensity
Max Heart Rate Drops with Age
- Linear decrease in heart rate with age
- Estimated using the formula: 220 - age (± 10bpm)
- Due to reduced adrenoreceptor sensitivity
- Contributes to decrease in maximal cardiac output with age
Implications of Heart Rate Responses
- Resting heart function is important
- Determines heart rate range (cardiac reserve)
- Indicator of health status: lower resting heart rate indicates lower cardiac oxygen demand and higher potential for power
- Fast recovery from exercise indicates higher aerobic fitness
- Slower rate of rise in heart rate is generally good
- Can also reflect anti-hypertensive therapy (alpha blocker)
Summary of the Control of Cardiac Output
- Cardiac Output (Qc) = Stroke Volume (SV) x Heart Rate (HR)
-
Stroke Volume:
-
Intrinsic (Autoregulation):
- Frank-Starling Law of Heart
-
Extrinsic:
- Direct neural drive from the sympathetic nervous system
- Adrenaline and noradrenaline from the adrenal medulla
-
Intrinsic (Autoregulation):
-
Heart Rate:
- Direct neural drive (balance of sympathetic and parasympathetic nervous systems)
- Hormonal influence from the sympathetic nervous system on the Adrenal Medulla
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
