Week 5 - Cardiovascular system Flashcards
Whats the role of the cardiorespiratory system
(ON SHEET)
Transport o2 and nutrients to tissues
Remove Co2 waste from tissues
Regulate body temperature
What are the 2 major adjustments of blood flow during exercise
Increased cardiac output
Redistribution of blood flow from inactive organs to active muscle
Whats the role of arteries and veins
Arteries carry blood away from the heart
Veins carry blood towards the heart
What are the physical characteristics of the blood
Plasma - liquid portion of the blood, contains ions, proteins and hormones
Cells - red blood cells erythrocytes, white blood cells platelets
Hematocrit - % of blood composed of erythrocytes
How does pressure change across the systemic circulation
Pressure is generated by the heart
Main resistance to flow is provided by arteries and arterioles
Whats the relationship of blood flow to pressure and resistance
(ON SHEET)
Blood flow is directly proportional to pressure
But is inversely proportional to resistance
What does resistance depend on
Length of the vessel
Viscocity of the vessel
Radius of the vessel
What is local vascular resistance
Resistance to blood flow in an organ or tissue calculated from pressure and local organ/tissue flow
What are the sources of vascular resistance
MAP decreases throughout the systemic circulation
Largest BP drop occurs across the arterioles
What is a-Vo2 difference and how is it impacted during exercise
Amount of o2 that is taken up from 100ml of blood
Increased during exercise due to increased o2 uptake in tissues
What is the Fick equation
Relationship between cardiac output, a-vo2 difference and vo2
Vo2 = Q x a-vo2 difference
What is central command theory
(ON SHEET)
Initial signal to drive cardiovascular system comes from higher brain centers
Fine-tuned by afferent feedback from heart mechanoreceptors, muscle chemoreceptors and pressure sensitve baroreceptors
Exercise pressor relex
What are baroreceptors
Sensitive to changes in arterial blood
pressure.
What are muscle mechanoreceptors
Muscle spindles and golgi tendon organs
Sensitive to force and speed of muscular movement
What are muscle chemoreceptors
Sensitive to changes in chemical environment
Why is the baroreflex reset during exercise
(ON SHEET)
Curves are shifted upwards and rightwards during exercise of harder intensity
Central command and exercise pressor reflex both play an active role in resetting the arterial baroreflex during exercise
What are the 3 parts that make up the heart wall
Epicardium
Myocardium
Endocardium
What is myocardial infarction
(ON SHEET)
Blockage in coronary blood flow results in cell damage
Exercise training protects against heart damage during an MI
What makes up the conduction system
Sinoatrial node - Pacemaker, initiates depolarization
Atrioventricular node - Passes depolarization to ventricles, brief delay to allow ventricular filling
Bundle branches - connect atria to left and right ventricle
Purkinje fibers - spread wave of depolarization throughout ventricles
What are the steps of the conduction system
(ON SHEET)
- Action potentials originate in the sinoatrial (SA) node (the pacemaker) and travel across the wall of the atrium (atrioventricular (AV) node.
- Action potentials pass through the AV node and along the atrioventricular (AV) bundle, which extends from the AV node, through the fibrous skeleton, into the interventricular septum.
- The AV bundle divides into right and left bundle branches, and action potentials descend to the apex
of each ventricle along the bundle branches. - Action potentials are carried by the Purkinje fibers from the bundle branches to the ventricular walls
What do the different aspects of an ECG show
(ON SHEET)
ECG - records the heart’s electrical activity
P wave - atrial depolarization
QRS complex - ventricular depolarization and atrial repolarisation
T wave - ventricular repolarization
What is the reltionship between pressure changes and the ECG
(ON SHEET)
Intraventricular pressure rises as ventricles contract
Intraventricular pressure falls as ventricles relax
How can the ECG be used for diagnostic purpose
Graded exercise test to evaluate cardiac function - observe ECG during exercise, also observe changes in blood pressure
Atherosclerosis
S-T segment depression - suggests myocardial ischemia
How is regular exercise cardioprotective
Reduces incidence of heart attacks
Improves survival from heart attacks
How does exercise help with the amount of myocardial damage from heart attack
(ON SHEET)
Improvements in heart’s antioxidant capacity
Improved function of ATP-sensitive potassium channels
How does PNS regulate HR
Slows HR by inhibiting SA and AV node via vagus nerve
How does SNS regulate HR
Increases HR by stimulating SA and AV node via cardiac accelerator nerves
Whats the purpose of using exercise stress tests for diagnosis of coronary artery disease
Exercise stress tests can detect restricted coronary flow due to coronary artery
disease
Coronary circulation measurements
At rest heart takes 5% of L min-1 = 0.25 Lmin-1
In exercise heart takes 5% of 25 Lmin-1 = 1.25L/min-1
At rest oxygen extraction is already high 65-75%
What is the main reason for increased myocardial oxygen consumption
an increase in coronary blood flow with only modest contributions of increase in haematocrit and oxygen extraction
How is coronary circulation controlled
Coronary blood flow is closely related to cardiac work
Chronotpic - HR increases
Inotropic - Contractility increases
Whats the main metabolic vasodilator
Adenosine
What are the mechanical forces that control coronary circulation
(ON SHEET)
At rest, 80% of coronary flow takes place during diastole because of vessel compression during systole
During heavy exercise, 40-50% occurs during systole (less time in diastole)
