Week 4: Physiology of the Cardiovascular System Flashcards
What are the 11 different body systems?
- Circulatory system, consisting of…
- Cardiovascular system
- Lymphatic system! - Digestive system
- Respiratory system
- Urinary system
- Skeletal system
- Muscular system
7.Integumentary system - Immune system
- Nervous system
- Endocrine system
- Reproductive system
Define homeostasis.
Maintaining a relatively constant internal environment (steady state) in the face of a constantly changing external environment.
What is the average red blood cell concentration for males?
5.4 x 10^6/microlitre
(with a normal range being 4.5-6.5)
What is the average red blood cell concentration for females?
4.8 x 10^6/microlitre
(with a normal range being 3.9-5.6)
What two systems regulate homeostasis?
- Nervous system
- Hard-wired
- Fast acting (milliseconds)
- Rapid response by target cells - Endocrine system
- Hormones transported in blood
- Slower acting (minutes, hours, days)
- Slower and often long-lasting responses of target cells
NOTE! The nervous and endocrine systems often overlap in function (e.g., in blood pressure regulation)!
What is the heart?
A high-pressure pump, essentially the central driver of the cardiovascular system.
What is the function of blood vessels (a.k.a., vasculature)?
Distributes blood to all parts of the body and back to the heart.
What are the 5 types of blood vessels?
- Arteries
- Arterioles
- Capillaries
- Venules
- Veins
What is the function of blood?
It is a transport medium in which materials to be transported are dissolved or suspended.
What are the two vascular loops (blood vessel loops)?
- Pulmonary circulation (from the heart to the lungs and back)
- Systemic circulation (from the heart to the other organs and back)
What are the two vascular loops (blood vessel loops)?
- Pulmonary circulation (from the heart to the lungs and back)
- Systemic circulation (from the heart to the other organs and back)
How much of our total body weight (TBW) is made up by the blood?
About 8%.
What is the average volume of blood in…
- Males?
- Females?
Males = 5.5 litres
Females = 5 litres
What is the liquid portion of the blood called? What portion of the blood is liquid?
Plasma, which makes up approx. 55% of the blood.
What are the 3 types of specialised elements that are suspended in the plasma?
- Erythrocytes (Red Blood Cells)
- Important in oxygen transport! - Leukocytes (White Blood Cells)
- Immune system’s mobile defence unit - Platelets
- Important in haemostasis (blood clotting)
What is haemostasis?
Blood clotting.
What portion does each blood component of the blood take up of the whole blood?
Plasma = 55% of whole blood
Erythrocytes = 45% of whole blood
Platelets and Leukocytes = <1%
What is the function of the smooth muscle that is present in the walls of some blood vessels?
Allows the blood vessels to contract (vasoconstriction) or relax (vasodilation) in response to changes in the local environment.
What is achieved through vasoconstriction?
Blood vessels is narrowed, limiting blood flow.
Give an example of when vasoconstriction may be employed.
- When temperature drops, the skin blood vessels will constrict.
- Reduces loss of heat from skin to the environment (i.e., a method of thermoregulation) - Blood vessels serving the kidneys and digestive tract will constrict during exercise.
- Allows us to divert that blood supply elsewhere where it is needed (i.e., skeletal muscles)
What is achieved through vasodilation?
Blood vessels widen, increasing blood flow.
Give an example of when vasoconstriction may be employed.
- When temperature increase, the skin blood vessels will dilate.
- Blood vessels serving the skeletal muscles will widen during exercise (allowing more blood to reach those tissues).
- More oxygen and fuel needed
What are the “receiving chambers” of the heart?
The atria!
- Right atrium receives deoxygenated blood from the systemic circuit
- Left atrium receives oxygenated blood from the pulmonary circuit (the lungs)
What is the name of the vein that brings blood from the body (systemic circuit) back to the heart?
Vena cava.
What valves prevent blood from back-flowing from the ventricles back into the atria?
Atrioventricular (AV) valves.
What valves are present in the arteries of the heart (i.e., the pulmonary arteries and the aorta) that prevent back-flow of blood into the ventricles?
Semilunar valves.
What is the major artery of the heart (where oxygenated blood exits)?
Aorta.
What must pass through the heart to allow the cardiac muscle to contract?
Electrical current.
What property of the heart ensures its uniform beating?
Autorhythmicity - allows the heart to generate its own rhythm.
What is the function of the pacemaker (SA node)?
Coordinates and provides rhythm to the heartbeat.
Where is the pacemaker found?
In the right atrium (near the vena cava).
What do the conduction fibres do?
Rapidly conduct the current initiated by the pacemaker cells to the myocardium (i.e., heart muscle).
What is another name for the heart muscle?
Myocardium.
What is the pathway of the electrical current that is initiated by the pacemaker cells?
- Travels through the internodal pathway to the Atrioventricular (AV) node.
- Then passes down the Bundle of His.
- Finally emerges through the Purkinje Fibres, causing the ventricles to contract.
Where are the Purkinje fibres found?
Throughout the cardiac muscle of the ventricles.
What is another word for the heartbeat (used in physiology)?
The cardiac cycle.
What term do we use to describe the heart chambers contracting?
Systole.
What term do we use to describe the heart chambers relaxing?
Diastole.
How long does the cardiac cycle last?
Roughly 0.8 seconds (but depends on HR).
What is the sound that indicates valve closure?
Lub dup heart sounds.
How do we clinically measure the electrical activity of the heart?
Through an ECG (electrocardiogram).
- Non-invasive
- Can allow us to test for clinical abnormalities in the electrical activity of the heart
What are the components of an ECG?
- P wave
- QRS complex
- T wave
What does the P wave represent?
Atrial excitation (i.e., atrial depolarisation).
What does the QRS complex represent?
Ventricle excitation (i.e., ventricle depolarisation).
What does the T wave represent?
Ventricle repolarisation (i.e., return to resting state).
What does an electroencephalogram (EEG) measure?
Measures electrical activity in the brain.
What does an electromyogram (EMG) measure?
Measures electrical activity in the muscle.
- Helps detect neuromuscular abnormalities
Where are the 10 electrodes placed in an ECG?
- 6 chest electrodes.
- 4 limb electrodes (2 on each wrist and 2 on each ankle).
What is stroke volume (SV)?
The volume of blood ejected from the ventricle during each heartbeat.
What is an average range for stroke volume?
60-100mls
What is the cardiac output (CO)?
The volume of blood pumped by each ventricle per minute.
How is cardiac output (CO) calculated?
CO = heart rate (HR) x stroke volume (SV)
What is an average CO value at rest?
5 litres/min at rest
- This differs across the population
- Even differs in each individual minute by minute!
What is CO driven by during light to moderate activity?
CO is driven by HR and SV.
What is CO driven by during moderate to strenuous activity?
CO is driven by HR.
How does the distribution of the blood flow change during exercise?
Vasodilation at the skeletal muscles and heart will increase blood flow (to supply more blood flow to the tissues that need it).
Vasoconstriction to the GI tract and kidneys decreases blood flow (allowing blood to be pumped to places of greater priority during exercise).
What is the total peripheral resistance (TPR)?
The overall resistance to blood flow in the cardiovascular system.
What happens to TPR during strenuous aerobic exercise?
TPR is decreased because there is more dilation than constriction (i.e., the degree of dilation and constriction doesn’t match).
What, essentially, is TPR a reflection of?
TPR is a reflection of the degree of vasodilation and vasoconstriction throughout the entire body.
How does CO and TPR change differ in resistance exercise (compared to aerobic exercise)?
Aerobic exercise:
- Increase in CO
- Decrease in TPR
Resistance exercise:
- Modest increase in CO (using less muscle groups for shorter periods of time)
- Little to no change in TPR (because we are generating resistance in the body, see the “Valsalva manoeuvre”)
What is the “Valsalva manoeuvre”?
A breathing method that is employed when lifting a heavy weight in which you hold your breath, strain, and close your glottis.
What cardiac alterations do we see with resistance training?
Hypertrophy of cardiac muscle (i.e., the heart muscle gets thicker).
What skeletal muscle improvements do we see with resistance training?
Hypertrophy (increase and growth of muscle) and fatigue resistance.
What role does testosterone play in muscle growth?
It facilitates protein synthesis and growth of muscle.
- Males have more testosterone
- Thus, males can put on more muscle than females
What cardiac alterations do we see with aerobic training (e.g., distance running)?
- Increase in cardiac dimensions (size of the heart)
- Increase in the volume of the ventricles
- Resting heart rate decreases (to 40bpm or below!)
- Resting stroke volume increases (to >100ml)
- Blood volume increases (increase in RBC and plasma)
- Skeletal muscle efficiency increases
Note!
- Little change in the thickness of ventricular wall
What is meant by pathological hypotrophy (in relation to the heart)?
Cardiac remodelling in response to disease!
- Hypertension (resulting in thicker walls to push against a higher pressure)
- Infarction (resulting in dilation of the heart due to heart muscle being starved of blood)
- Diabetes (causing diastolic dysfunction etc.)
Give an example of a maternal physiological response to pregnancy.
Increase in the blood volume.
What happens to the heart in space?
Becomes more spherical and loses muscle mass.
What CO values might you expect to see in an untrained male and female during exercise?
Male - 25 L/min
Females - 20 L/min
(increasing from roughly 5 L/min at rest)
What peak CO was once recorded for Miguel Indurain (an elite cyclist)?
Peak CO of 50 L/min.
Describe the HR and SV of elite athletes at rest.
Low heart rate.
High stroke volume.
What is systolic pressure?
The pressure in the arteries during ventricular systole.
- This is the highest pressure in the arteries
What is diastolic pressure?
The pressure in the arteries during ventricular diastole.
- It will be lower than systolic pressure
What is a pulse?
It is the rhythmic bulging of the artery walls with each heartbeat.
What is the pulse pressure?
Pulse pressure is the difference between systolic and diastolic pressure.
What are the units used for blood pressure?
Millimetres of Mercury (mmHg)
For healthy blood pressure, what readings should we get for…
Systolic pressure?
Diastolic pressure?
Systolic = <120mmHg
Diastolic = <80mmHg
What are the non-modifiable factors effecting blood pressure?
- Age
- Sex
- Genes
What are the modifiable factors effecting blood pressure?
- Diet (fat, salt, cholesterol, alcohol)
- Smoking
- Obesity and Type 2 diabetes
- Stress
- Sedentary behaviour
What is hypertension defined as?
Consistent readings of…
Systolic pressures > 140mmHg (changes to 130 mmHg by the AHA)
Diastolic pressure > 90mmHg
What is “white coat” hypertension?
An increase in blood pressure simply from being in a clinical setting (e.g., doctor’s office) when it is actually lower in another setting (e.g., at home).
What is primary/essential hypertension?
Cumulative effects of genetics, lifestyle, and environmental factors.
- 95% of cases
What is secondary hypertension?
High blood pressure that is developed as a result of some other disease (e.g., renal disease, adrenal disease).
- Only 5% of cases
How do we treat hypertension non-pharmacologically?
Lifestyle change!
What is the aim of antihypertensives?
To prevent endpoints (i.e., myocardial infarction, stroke) by reducing blood volume and reducing cardiac output.
What is the technical term used to describe a heart attack?
Myocardial infarction.
How do diuretics work?
Act on kidneys and endocrine system to reduce blood volume.
How do beta-blockers work?
Act on the heart to reduce cardiac output.
How do alpha-blockers work?
Reduce total peripheral resistance by dilating the blood vessels.
What disease are included under the umbrella term “cardiovascular disease”?
- Coronary Heart Disease
- Peripheral Arterial Disease
- Cerebrovascular Disease
- Hypertension
What is Coronary Heart Disease?
Disease of the blood vessels supplying the heart, which greatly increases the chance of heart attack.
What is Peripheral Arterial Disease?
Disease of the blood vessels supplying the limbs.
What is Cerebrovascular Disease?
Disease of the blood vessels supplying the brain that can lead to stroke.
Exercise has been shown to…
- Reduce blood pressure in hypertensive patients.
- Decrease plasma triglyceride (fat) levels.
- Raise plasma HDL-cholesterol (the “good” cholesterol)
- Lowers plasma LDL-cholesterol (the “bad” cholesterol)
- Protects against atherosclerosis (hardening of the arteries).
What is considered “good” cholesterol?
HDL-cholesterol.
What is considered “bad” cholesterol?
LDL-cholesterol.
What is atherosclerosis?
Hardening of the arteries.
