Int 4: Cardiovascular System Flashcards
What are the two main circulatory circuits
Pulmanory
Systemic
Name the 4 valves of the heart
- pulmonary semilunar valve
- aortic semilunar valve
- left AV (bicuspid) valve
- right AV (tricuspid) valve
Cardiac muscles are a)______ meaning they will only contract along their long axis. They wrap around the heart to contract in 2 axis
a) striated
Name some things that a healthy endothelium regulates
- vessel tone
- movement of fluid into tissues
- leukocyte adhesion, platelet aggregation
- structure of endothelium varies in different locations depending on its function
What does the term myogenic mean and how does cardiac muscle pull it off
generates its own action potential - action potential conducted from cell to cell via intercalated discs which have gap junctions.
skeletal muscle is neurogenic
What is the function of the Purkinje fibres
To coordinate contraction of the muscles in the ventricles
Explain the process of cardiac excitation
1) AP depolarises atria while impulse is delayed at AV-node ~100ms
2) AV-node the activate Purkinje fibres via Bundle of His
3) Purkinje fibres activate ventricles
Explain the processes behind the following steps in terms of Na+, K+ and Ca++:
1) Depolarisation of cardiac muscles
2) Repolarisation (3 sub-steps)
3) refractory period
1) Fast influx of Na+
2a) Steep initial decrease from the efflux of K+.
2b) Ca2+ is also released from intracellular stores to cause contraction (enters vi a Ca channels)
2c) Further repolarisation from K leaving
3) Hyperpolarisation, heart still contracted because of high calcium. Na+ removed and K+ returned via Na+/K+ ATPase. Also a Na/Ca exchanger
When measuring the electrical activity of the heart you can measure 4 things:
a) automaticity
b) conductivity
c) hypertrophy
d) ischemic damages
What is being measured in each case
a) HR, rhythmicity
b) pathway
c) -
d) location, size and progress
Below are the ECG events of the cardiac cycle. Describe the events that are occurring / causing these ECG features
- P wave (small bump)
- Q wave (small, sharp downwards divot)
- R wave (sharp, large upwards spike)
- S wave (sort of like hyperpolarisation, small downward divot)
- T wave (rounded bump)
Repeat
- P wave: Atrial depolarisation, atria contract after
- Q wave: Signal goes through sinoatrial node to Purkinje fibres
- R wave: Purkinje fibre depolarisation, ventricle contraction
- S wave: Ventricles still contracted
- T wave: Repolarisation
- AORTIC valve CLOSES a bit after T wave
What is bradycardia and what is tachycardia
Bradycardia - Slow HR
Tachycardia - fast HR
Define the following:
- Cardiac Output
- Stroke Volume
- Ejection Fraction
- Cardiac Output: amount of blood pumped out by each side of the heart in 1 minute
- Stroke Volume: Vol of blood pumped out by each ventricle in one contraction
- Ejection Fraction: % of blood vol that is pumped out by the ventricle can increase to 80% during exercise
The ANS (sympathetic and parasympathetic) can modify 2 things to do with the heart, what are they?
Rate of activation (thru effects on the S.A node) and contraction force
Two branches of the ANS are involved in heart modulation, the parasympathetic (PSNS) and the sympathetic nervous system (SNS). What type of nerves does each system use?
PSNS: Cholinergic
SNS: Noradrenergic
What are the respective functions of the PSNS and SNS on heart activity? (hint = 1 decreases and 1 increases)
Sympathetic: Fight or Flight
- Increases HR
- Increases rate of conduction and overall excitability
- Increases force of contraction
- Dilates coronary arteries
Parasympathetic: Rest
- Decreases HR
- Reduce the force of contraction
What is considered normal BP and what is considered hypertension
Normal: 120/80mmHg
Hypertension: 140/90mmHg
Outline the foundations of measuring BP and how it can be measured
- SBP and DBP
- Pulse pressure = SBP-DPB
- 2/3 cycle is in diastole, 1/3 in systole
- Can be measured invasively (arterial cannulation) or indirectly (cuff sensor)
What is mean arterial blood pressure and why do we use it?
- Is the average arterial pressure through 1 cardiac cycle
- Used because it accounts for flow, resistance, and pressure within arteries.
- MAP = DP + 1/3(pulse pressure)
What does stroke volume depend on? (2 things - pretty obvious)
- Contractility (force of contraction)
- End diastolic volume (amount of blood in ventricles)
What is Starling’s Law of the heart (hint = elastic one)
- Venous return to the heart gives ‘preload’. this refers to the stretching of the heart muscle during filling.
- Higher venous return increases volume –> increases stretch of the ventricle –> increases elastic recoil
What is Laplace’s Law? (hint = blood pressure one)
Force acting on blood vessel wall is proportional to: Diameter of vessel x BP
Large diameter = thick walls to withstand pressure
Capillaries = thin walls = low pressure
Hypertension induces stiffness of arteries so can lose their elastic properties
What is Ohm’s Law? (hint = flow one) and Poiseuille’s adaptation
Flow = Pressure gradient / Resistance
Poiseuille found that a 2 fold change in radius produces a 16 fold change in flow rate. I.e. small changes in arteriole diameter exert large changes in tissue perfusion.
How do kidneys control blood volume?
1) Blood pressure increases
2) Kidney excretes more salt and water
3) Extracellular fluid volume falls
4) Blood pressure falls
Given a normal ECG record, what would be the approximate duration of the P-R interval, the QRS complex and the Q-T and the S-T intervals?
a) 0.4s
b) 0.08s
c) 0.32s
d) 0.12-0.2s
- P-R interval
- QRS complex
- Q-T interval
- S-T interval
a) Q-T
b) QRS complex
c) S-T
d) P-R
Note:
At a state of rest (75bpm), systole lasts 0.27s and diastole 0.53s
Which fibres are where in the heart:
a) Ordinary myocardial fibres
b) Bachmann’s bundle
c) Purkinje fibres
d) Bundle of His
a) Right atrium
b) Left atrium
c) Ventricles
d) Upper ventricles
