Physiology Flashcards
What is the cardiac cycle of the heart?
A series of alternating contractions and relaxations of the hearts atria and ventricles in order to pump blood throughout the body.
Fluid in the body moves from an area of high to low pressure. How does this apply to the heart?
The pressure will increase inside one of the heart chambers and will increase pressure, valves will open and blood will flow to the area of lower pressure.
The rate of heart beat is set by the electrical conduction system of the heart. What part of the heart sets this?
a. Pukingje fibres.
b. Bundle branches.
c. SA Node
The SA node of the right atrium sets the rate of your heart beat.
Is the systole the contraction or relaxtion of the heart?
Contraction
Relaxtion is the diastole
The cardiac cycle has three phases. What are they?
Ventricular Filling.
Ventricular Systole
Isovolumetric relaxtion
In phase 1 of the cardiac cycle (Ventricular filling), the ventricles are end of the diastole and will contain the maximum amount of blood. What is this called?
End Diastolic volume
An ECG has P, Q, R,S, T Waves. What does the P Wave represent?
The P Wave is when the atria depolarise.
In phase 2 of the cardiac cycle, ventricular systole we hear the noise of ‘lub’. What does this represent?
It is when the AV valves close.
In Phase 2 of the cardiac cycle, ventricular systole, how is it represented on an ECG?
It is the QRS Wave on an ECG which shows the atria relax and the ventricles depolarise.
What is the end systolic volume?
When there is a small amount of blood that remains in ventricles at the end of systole.
The second heart sound of the cardiac cycle is a ‘dub’. What phase does this happen and what does it represent?
The dub occurs in Phase 3 - isovolumetric relaxation and represents the closing the Semilunar valves.
The T wave on an ECG is what phase of the cardiac cycle?
Phase 3 - isovolumetric relaxation.
This is early diastole where ventricles repolarise, causing them to relax.
Sometimes we can hear a 3rd heart sound. When would you hear this?
When blood rapidly empties into ventricles causing turbulent flow of the blood.
What is cardiac output and how we do we calculate it?
It is the volume of blood pumped out of each ventricle in 1minute.
Heart rate x Stroke volume = Cardiac Output
Venous return and blood pressure are 2 of the 5 factors which influence cardiac output. What are the other three?
Blood volume - amount of blood in CV system.
Heart rate - number of times heart beats in 1min
Stroke volume - amount of blood pushed out of a ventricle each time it contracts.
Venous return is the amount of blood returning through the veins to the right atrium of the heart.
Venous return is aided by three functions, what are they?
Respiratory pump - pressure changes in thoracic cavity by breathing.
Valves - preventing backflow.
Muscular pump - skeletal muscles compresses veins and pushes blood back to the heart.
What is the amount of blood pumped out of the ventricle with each heart beat?
Stroke Volume
Stroke volume is calculated by:
End diastolic volume - end systolic volume = SV
Stroke volume is affected by three factors. What are they?
Pre-load - blood volume / venous return.
After-load - vasodilation / constriction
Contractility - hormones / potassium / sodium
True or false - Preload is how much the ventricle wall is stretched.
True - and is increased if blood volume and venous return increases.
Therefore will increase stroke volume.
Pressure inside the left ventricle must be greater than inside the aorta to ensure the ventricle can eject the blood into the aorta. What is this called?
Afterload.
Stroke volume is increased by blood volume and exercise, what are three other factors that influence SV?
Sympathetic stimulation
Vasodilation
Increased EDV - end diastolic volume.
What is cardiac output?
The volume of blood pumped out by each ventricle in a minute.
How do we calculate cardiac output?
Heart rate x stroke volume = cardiac output.
On average, how much blood is pumped into the systemic circuit from the left ventricle every minute?
About 5.25L of blood is pumped from the left ventricle every minute.
What two factors affect heart rate?
Para & Sympathetic nervous stimulation.
Afterload is the amount of pressure a ventricle needs to overcome. If afterload is increased, what is the effect on stroke volume and cardiac output?
Stroke Volume will decrease.
Cardiac output will also decrease.
True or false.
Blood pressure is the pressure exerted by the circulating blood on the blood vessel walls.
True. Refers to systemic arteries at the level of the heart.
In order for blood to flow to tissues there has to be a pressure gradient.
True or False - blood flow from low pressure to the high pressure outside of the arteries?
False.
Blood flows from an area of high pressure (inside arteries) to the low pressure in the veins.
How do you calculate blood pressure?
Cardiac Output x Peripheral resistance = Blood Pressure
Will blood pressure increase or decrease if cardiac output is increased?
Blood pressure will increase as the amount of blood pumped out of each ventricle in 1 minute increases.
If the resistance inside the blood vessel is increased through blood being viscous. What will this do to blood pressure?
Blood pressure will increase as the peripheral resistance of the vessel increases, therefore, increasing blood pressure.
The mean arterial blood pressure (MAP) measures _______ in the arteries over the whole cardiac cycle.
a. Rate of contraction
b. Pressure
c. Volume of blood pumped
d. length of artery
The MAP is the average pressure in the arteries over the whole cardiac cycle.
Why do we know the mean arterial blood pressure of our arteries?
We calculate the MAP so that we know the tissue perfusion of the blood flow through the tissues - if the MAP is above 60mmHG we will have healthy tissues.
What does the systolic blood pressure represent?
Systolic blood pressure is the highest pressure in the arteries created by the contraction of the left ventricle.
Does the diastolic pressure represent contraction or relaxtion of the ventricles?
Relaxation of the ventricles.
What are considered normal (healthy range) parameters for MAP?
60-100mmHG
Is blood pressure lower in the systemic or pulmonary circuit in the body?
BP is lower in the pulmonary circuit -
What is the most important force in venous flow of blood through veins?
The pressure gradient that is generated by the heart.
Stimulation of the sympathetic nervous system, which will increase stress, will increase BP, what are the two factors that increase BP?
Increased blood viscosity
Increased peripheral resistance
Vasodilation is one of four factors which decrease BP, what are the other 3?
Decreased blood volume
Decreased heart rate
Decreased contractility of the heart.
There are two main reasons why it is important for you BP to be within normal ranges, what are they?
Ensures adequate blood supply to the tissues.
Prevents damage to the blood vessels through having an high BP.
There are two fast short term corrections that can occur to regulate BP, what are they?
- Neural mechanisms
2. Hormonal mechanisms
Baroreceptors are found in the wall of blood vessels. What is their role of when BP increases?
When BP increases, it stretches the walls of the blood vessels which stimulate the baroreceptors. This will send a rapid stream of nerve impulses to the brain, altering:
Heart rate
Contractility
Dilation of blood vessels.
The kidneys play a role in the long term regulation of BP. This is achieved in two ways, they are:
- Direct mechanism - variation in blood flow through the kidneys alters rate of urine formation.
- Indirect mechanism - hormones alter the reabsorption of water in the kidneys.
There are five hormones which will be secreted when BP is low to increase it, they are?
Aldosteron Antidiuretic hormone Atrial natriuretic peptide Angiotensin 11 Noradrenaline
What hormone is secreted when BP is high to lower it?
Atrial Natriuretic peptide (ANP)
Movement of fluid between the blood and _______ occurs in the capillary bed?
a. venules
b. veins
c. interstitual fluid
d. arteriorles
Occurs between the blood and interstitial fluid.
The majority of blood is returned to the heart through veins, a small amount is returned to circulation by what ____ vessels.
a. venules
b. capillary beds
c. lympathic
d. endocrine
Lymphatic vessels.
BP can be measured directly and indirectly. What is the was you would see in the hospital?
Indirect measurement -
Direct measurement is a catheter into the artery with an attached pressure gauge..
Korotkoff sounds in BP is first heard when the blood spurts into the constricted artery. Is this the systolic or diastolic reading?
Systolic pressure.
