Lec 21 Cardiovascular Part 1 Flashcards
What are the high pressure circuits?
Arteries and arterioles
What are the low pressure circuits
Veins and venules
What are the exchange vessels
Capillaries
At what level is blood pumped with no direction
Arteries
At what level is blood distributed
Arterioles
The _______ of blood flow varies in different sections of the circulatory system
Velocity
What is the relationship between CSA and velocity of blood flow
As CSA increases then velocity ________
Inversely related
Decreases
Where is blood flow the slowest and why
Capillaries due to exchange of nutrients and gases
Where is velocity/ pressure the highest and where is it the lowest
Highest in arteries lowest at capillaries and goes slightly back up at that venous side
What are the difference between myocardium vs skeletal muscle
- 5 structural differences and 2 mechanical differences
Structural
- shorter, no satellite cells, intercalated disks connecting end to end, homogenous fibres (type 1), connected fibres contract as a unit
Mechanics
- is involuntary contraction
- calcium induced calcium release
What types of muscle has calcium to calcium release
Myocardial muscle
Myocardium generates ____________ electrical singles
What is this due to
It’s own
Due to anatomical coupling through gap junctions
No regeneration of action potential ?
What is the intrinsic control of myocardium electrical activity
- SA node does NOT contribute to myocardium contraction - just automatic impulse
- SA node is the pacemaker - is the fastest to depolarize due to leakiness of Na rather than K
- SA node - AV node - AV bundle
- delay between AV node and AV bundle allows the blood from the atria to fully empty into the ventricles before contraction
- the terminal ends of AV bundles are purkinji fibres which transmit impulse to ventricles
Does SA node contribute to myocardium contraction?
Why is SA node considered the pacemaker
SA node does NOT contribute to myocardium contraction - just automatic impulse
SA node is the pacemaker - is the fastest to depolarize due to leakiness of Na rather than K
What is the sequence of events ?
Why is it important to have a delay between AV node and AV bundle ?
What are purkinji fibres and what do they do?
- SA node - AV node - AV bundle
- delay between AV node and AV bundle allows the blood from the atria to fully empty into the ventricles before contraction
- the terminal ends of AV bundles are purkinji fibres which transmit impulse to ventricles
What are the extrinsic control factors of HR
Parasympathetic NS, sympathetic NS, endocrine system
What role does the parasympathetic NS play on HR and where does it originate
Originates at medulla oblongata
Plays a role in vagal tone produced by the vagal nerve
Reduces heart rate - at rest sets HR to around 60-80
Vagus nerve sends signal to SA node and AV nodes to release ACETYLCHOLINE ( at this level acetylcholine reduces)
What role does sympathetic NS play on HR
Increases the rate of depolarization of the Sa node
Increases HR
What role does the endocrine system play on HR
When does it occur, where does it come from, what is released
Epinephrine and norepinephrine are released from the adrenal glands
Triggers by sympathetic stimulation during stress
Chemoreceptors in the arteries and metoboreceptors of muscle have a ________ effect while
Baroreceptors in the heart and lungs have a ________ effect and ____________ role
Positive
Negative , homeostatic
They work like brakes and balance out the hearts excitatory and inhibitory responses
What is the definition for cardiac cycle
Repeating pattern of contraction and relaxation of the heart
Which involve mechanical and electrical events that occur in a single heart beat
What is the diastolic phase
Relaxation phase
Ventricles fill with blood
Twice as long as systole
70% passive flow 30% atrial contraction
What is the systole phase
Contraction phase
Ventricle contract
Ejection of blood into aorta and pulmonary artery
Describe the cardiac cycle
When is the blood ejected from the ventricles what is this called
atrial contraction followed by ventricle contraction pumping the blood into pulmonary and systematic circuits
Blood is ejected from the ventricles when the ventricular pressure become greater than the pressure in the aorta and pulmonary artery, called cardiac afterload
