Circulatory Response to Exercise (CHPT 9) Flashcards
What are the components of the circulatory system?
- Heart
- Arteries and arterioles
- Capillaries
- Veins and venules
The cardiovascular system works with which system?
- pulmonary system
What are the purposes of the cardiorespiratory system?
- Transport O2 and nutrients to tissues
- Removal of CO2 wastes from tissues
- Regulation of body temperature
What are the two major adjustments of blood flow during exercise?
- Increased cardiac output
- Redistribution of blood flow
What is the formula to calculate arterial blood pressure?
- = Cardiac Output x Total Peripheral Resistance
What side of the heart has the pulmonary circuit?
- Right side of the heart
What is the role of the pulmonary circuit?
- Pumps of deoxygenated blood to the lungs via pulmonary arteries
- Returns oxygenated blood to the left side of the heart via pulmonary veins
What side of the heart has the systemic circuit?
- left side of the heart
What is the role of the systemic circuit?
- Pumps oxygenated blood to the whole body via arteries
- Returns deoxygenated blood to the right side of the heart via veins
What is the purpose of the cardiovascular system?
(1) the transport of O2 to tissues and removal of wastes
(2) the transport of nutrients to tissues
(3) the regulation of body temperature
What are the three layers of the heart wall?
- Epicardium
- Myocardium
- Endocardium
Where does the heart receive its blood supply from?
- via coronary arteries
- high demand for oxygen and nutrients
What is a myocardial infarction (MI)?
- Blockage in coronary blood flow results in cell damage
- Exercise training protects against heart damage during MI
What are some characteristics of the epicardium?
- serous membrane including blood capillaries, lymph capillaries, and nerve fibers
What is the function of the epicardium?
- serves as a lubricative outer covering
What is the function of the myocardium?
- provides muscular contractions that eject blood from the heart chambers
What are some characteristics of the myocardium?
- cardiac muscle tissue separated by connective tissues and including blood capillaries, lymph capillaries, and nerve fibres
What are some characteristics of the endocardium?
- endothelial tissue and a thick subendothelial layer of elastic and collagenous fibers
What is the function of the endocardium?
- serves as a protective inner lining of the chambers and valves
What is the connective tissue of the heart?
- endomysium
Does the heart have cellular junctions?
- yes, intercalated discs
Is the energy production of the heart aerobic or anaerobic?
- aerobic
Where does the heart get its calcium supply for contraction?
- sarcoplasmic reticulum and extracellular calcium
How is regular exercise cardioprotective?
- Reduce the incidence of heart attacks
- Improves survival from a heart attack
How does exercise reduce the amount of myocardial damage from a heart attack?
- Improvements in the heart’s antioxidant capacity
- Improved function of ATP-sensitive potassium channels
What is an ARED?
- Advanced Resistive Exercise Device
- Load of up to 600 pounds using vacuum cylinders and flywheel
- Used in space
Explain the aspects of the systole phase of the cardiac cycle.
- Contraction phase
- Ejection of blood
~2/3 blood is ejected from ventricles per beat
Explain the diastole phase of the cardiac cycle.
- Relaxation phase
- Filling with blood
At rest, is diastole or systole longer?
- diastole
What is the length of the systole and diastole at a resting heart rate of 75 bpm?
- s: 0.3 s
- d: 0.5s
Explain the pressure changes during the diastole phase of the cardiac cycle.
- Pressure in ventricles is low
- Filling with blood from atria
- AV valves open when ventricular P < atrial P
Explain the pressure changes during the systole phase of the cardiac cycle.
- Pressure in ventricles rises
- Blood ejected in the pulmonary and systemic circulation
- Semilunar valves open when ventricular P > aortic P
Explain the lub and dub sounds of the heart.
First (lub): closing of AV valves
Second (dub): closing of aortic and pulmonary valves
What is normal blood pressure?
- 120/80 mmHg
What is systolic pressure?
- Pressure generated during ventricular contraction
What is diastolic?
- Pressure in the arteries during cardiac relaxation
What is pulse pressure?
- Difference between systolic and diastolic
What is mean arterial pressure? (MAP)
Average pressure in the arteries
How is mean arterial pressure calculated?
- MAP = DBP + 0.33(SBP – DBP)
What is hypertension?
- Blood pressure above 140/90 mmHg
What is the cause of primary hypertension?
- Cause unknown
- 90% cases of hypertension
What is the cause of secondary hypertension?
- Result of some other disease process
Hypertension is a risk factor for…
- Left ventricular hypertrophy
- Atherosclerosis and heart attack
- Kidney damage
- Stroke
What are the determinants of mean arterial pressure?
- Cardiac output
- Total vascular resistance
Explain, short-term regulation of blood pressure.
- Sympathetic nervous system
- Baroreceptors in aorta and carotid arteries
An increase in blood pressure = a decrease or an increase in sympathetic nervous system activity?
- Decrease in sympathetic nervous system activity
A decrease in blood pressure = increased or decreased sympathetic nervous system activity?
- Increased sympathetic nervous system activity
What controls long-term regulation of blood pressure?
- The kidneys
- Via control of blood volume
What are some factors that influence arterial blood pressure? (Increase)
- Blood volume increases
- Heart rate increases
- Stroke volume increases
- Blood viscosity increases
- Peripheral resistance increases
Contraction of the heart depends on what?
- Electrical stimulation of the myocardium
Explain the conduction system. (4)
- Sinoatrial node
- atrioventricular node
- Bundle branches
- Purkinje fibres
What is the role of the sinoatrial node?
- pacemaker, initiates, depolarisation
What is the role of the atrioventricular node?
- Passes, depolarisation to ventricles
- Brief delay to allow for ventricular filling
What is the role of the bundle branches?
- left bundle branch, conducts impulses to the left ventricle
- right…
What are the Purkinje fibres?
- Specific heart muscle tissue responsible for generation of the heart impulses
What is the first step of the conduction system?
- Action, potentials originate in the Sinoatrial node and travel across the wall of the atrium from the SA node to the AV node
What is the second step of the conduction system?
- Action potentials pass through the AV node, and along the atrioventricular bundle, which extends from the AV node, through the fibrosis skeleton, into the interventricular septum
What is the third step of the conduction system of the heart?
The AV bundle divides into right and left bundle branches, and action potentials descend to the apex of each ventricle along the bundle branches
What is the fourth step of the conduction system of the heart?
Action potentials are carried by the Purkinje fibres from the bundle branches to the ventricle walls.
What is the purpose of an electrocardiogram? (ECG)
Record the electrical activity of the heart
What is the P-wave in an electrocardiogram?
Atrial depolarisation
What is the QRS complex in an electrocardiogram?
- ventricle depolarisation, and atrial repolarisation
What is a T wave in the electrocardiogram?
- ventricle repolarisation
ECG abnormalities may indicate what?
Coronary heart disease
On an ECG, which segment indicates myocardial ischemia?
- ST segment
How can an ECG be used for diagnostics during exercise?
- graded exercise stress test to elevate cardiac function
- atherosclerosis
- ST segment depression
What is atherosclerosis?
- fatty plaque that narrows coronary arteries
- Reduces blood flow to myocardium
- Can cause a heart attack
What is cardiac output?
- The amount of blood pumped by the heart each minute
Cardiac output as a product of what?
- Heart rate (number of beats per minute)
- Stroke volume (amount of blood ejected in each beat)
What is the formula for cardiac output?
- Q = HR x SV
Cardiac output is dependent on…
Training state, and gender
How does the parasympathetic nervous system regulate heart rate?
- Via vagus nerve
- So is heart rate by inhibiting SA, and AV node
What causes an increase in heart rate at the onset of exercise?
- initial increase to the parasympathetic withdrawal
- later increase due to increased sympathetic nervous system, simulation
What is the relation between Beta-adrenergic blocking drugs (beta blockers) and heart rate?
- reduce heart rate and contractility (lower the myocardial oxygen demand)
- Compete with epinephrine and norepinephrine for beta receptors in the heart
Why are beta blockers prescribed (Heart issues)?
- Prescribe for patients with coronary artery disease and hypertension
What is heart rate variability?
- The time between heartbeats
What is the balance between the sympathetic nervous system and parasympathetic nervous system called?
Sympathovagal balance
Is a wide variation in heart rate, variability considered healthy?
Yes
What regulates stroke volume?
- end diastolic volume
- Average aortic blood pressure
- Strength of ventricular contraction
What is end diastolic volume?
- Volume of blood in the ventricles at the end of diastole
What is the strength of ventricular contraction enhanced by?
- circulating epinephrine and norepinephrine
- Direct sympathetic stimulation of heart
What is the equation for stroke volume?
SV = EDV (end-diastolic volume) x ESV (and systolic volume)
What is ejection fraction?
- Proportion of blood pumped out of left ventricle each beat
What is the formula for ejection fraction?
- EF = SV/EDV
