Circulatory physiology Flashcards
Explain (and give examples) of some of the key roles of circulatory systems.
- supply blood to tissues and deliver metabolic wastes for excretion
- initiate urine formation in the kidneys
- thermoregulation of various body parts
What is the difference between plasma and serum?
- plasma: fluid; dissolved substances (glucose, proteins, ions, hormones), clotting factors
- serum: plasma - clotting factors
When blood is centrifuged, what is contained in each of the resulting layers that form?
Plasma (55%), buffy coat (leukocytes and platelets,
What is the myocardium and through what artery is oxygen and nutrients supplied to this area? Why does the heart require an arterial blood supply?
- myocardium = cardiac muscle
- blood supplied via the coronary artery
- needs supply to make ATP and deliver O2 and nutrients to the heart so it can contract
How does the overall structure of an artery differ from a vein or a capillary? What is the implication
in terms of transport of solutes between the blood and the tissues?
- artery: many layers of tissue, thicker muscle, more resistance
- veins: many layers of tissue, valves, larger lumen
- capillaries: single endothelial layer; can be ‘leaky’
Arterioles play critical roles in providing appropriate amounts of blood to the tissues. Explain how
they are involved in controlling blood flow and the factors involved in controlling arteriole
constriction/dilation.
- control blood distribution in response to innervation, hormones (insulin, epinephrine) and local mediators (NO lactic acid)
- the smooth muscle controls arteriole diameter which controls blood flow to the tissue
What is the cardiac cycle and what are the five phases?
- one complete cycle of cardiac contraction and relaxation “heart beat”
- atrial contraction (systole)
- isovolumetric contraction (ventricular systole)
- ventricular ejection (ventricular systole)
- isovolumetric relaxation (ventricular and arteriole diastole)
- ventricular filling (ventricular and atrial diastole)
Using the proper terminology, outline the various phases in the cardiac cycle. Explain what is
happening to the heart valves, ventricular volume, and what parts of the heart are contracting at any given time.
- isovolumetric contraction: heart is contracting but because valves are closed, there is no change in blood volume in the ventricle; immediately before the ejection phase
- isovolumetric relaxation: the heart is no longer contracting, but the A-V valve is still closed (as is the aortic valve) and therefore blood cannot move from the atria into the ventricles; precedes the filling phase
- blood flows from high pressure to low pressure
- atrial contraction: A-V valve is open, blood pushed from atria to the ventricles
- ventricular ejection: contracting and pressure in ventricle exceeds that in the aorta/pulmonary artery
- ventricular filling: venous blood fills the atria, pressure in atria exceeds that of the ventricles, so the A-V valves open; blood flows from atria > ventricle
When we use the terms systole and diastole, what chamber of the heart are we usually referring to?
left ventricle
How does the amount of blood released during the contraction of the left ventricle compare to the
amount released from the right ventricle?
EQUAL amounts
Describe the processes involved with the depolarization (and contraction) of the atria and the ventricles (ie. how does depolarization spread from the area where it originates, throughout the entire heart)?
- need a “conducting system” to get depolarization from S-A node to ventricles
- A-V node depolarizes as the atria depolarizes and branches into the ventricles > depolarization spreads to ventricles
- delay between atrial and ventricular contractions due to the spread of depolarization through this system
What factors control heart rate? For each factor identified, explain the manner (ie. increase and decrease) and the mechanism (how they are able to influence heart rate) whereby they affect heart rate (or heart function)
- hormonal control: epinephrine and norepinephrine increases HR
- Neural control: sympathetic increase HR parasympathetic decrease HR
- Intrinsic control: frank-starling relation (match ventricular output with the end diastolic volume)
Define cardiac output and stroke volume.
- cardiac output (CO): the amount of blood pumped by a ventricle per minute
- stroke volume: amount of blood pumped from a ventricle with each heart beat
What is the Frank-Starling relation? What effect does end diastolic volume have on stroke volume for the next cardiac cycle?
- intrinsic control (heart controls over how much blood is released)
- greater stretch of cardiac muscles = greater force of contraction
- match output to input: increase end diastolic volume (EDV) = increase stroke volume
- can be influenced by ionotropes
What are the relationships between cardiac output, stroke volume and heart rate? What factors will allow for an increase in cardiac output and why?
Cardiac output can be increased by:
- increasing heart rate: sympathetic nervous system hormones
- increasing stroke volume: ionotropes to make muscles contract more strongly, increase ventricular filling
What factors determine blood pressure? In what ways?
blood pressure: heart contraction generates hydrostatic pressure
-flows from high pressure to low pressure
How does blood pressure change as the blood flows through the circulatory system?
blood pressure must overcome vascular resistance
What are some differences between pulmonary and systemic circulation? Why are these differences important?
- pulmonary: volume in pulmonary circulation = volume in systemic circulation; relatively low hydrostatic pressure; relatively low resistance
- systemic: arterial system is high pressure, high resistance; pressure decreases rapidly in the microcirculatory beds; venous part is low-pressure and low-resistance
How does the endocrine system regulate blood pressure/blood volume? What other factors can
regulate blood pressure/blood volume?
- higher blood volume = higher blood pressure
- kidneys are important in regulating blood volume
What happens to cardiac output during exercise and why? How is this achieved?
- need to increase O2 delivery to muscles during exercise
- vasodilation of microcirculatory beds in the muscles
- need to maintain O2 delivery to critical organs such as the heart and brain
During exercise, what tissues receive a greater portion of cardiac output? A lower portion of cardiac portion? Explain why.
-blood flow redistributed - more to muscles, less to GIT and kidneys
