Lecture notes
physiology
- Module
- Physiology
- Institution
- The University Of Huddersfield (UoH)
Lecture notes of 15 pages for the course physiology at UoH (lectures)
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Physiology- TERM TWOCardiovascular System
- Heart has autorhymatic cells which can create an AP, about 1-2% of cardiac
cells are autorhythmatic
- The AP can travel from cell to cell like a wave so all the cells will contract.
- Nerves involved are from ANS
- Sympathetic division will increase the heart rate and increase stroke volume
- Parasympathetic division will decrease the heart rate
- Without nerves the heart will do 120 BPM
- Heart is a double pump; systemic circulation and pulmonary circulation
- 2 reasons why blood flows correctly through the heart:
- Valves stop backflow of blood and allow it flow in one direction
- Electrical activity follows a pattern so it allows an orderly contractions
- Cells in tissues are rarely 100 nm away from capillaries. If cells are further
away they would die due to low oxygen and this is hypoxia
- Cardiac muscle cells have the same diameter as skeletal muscles but they
are 100 nm long as appose to 300,000 nm.
- Cross bridge cycle are the same
- Between the cells are intercalated disks which have anchoring proteins called
desmosome
- Pores allow excitation to travel from cell to cell
- They have unstable RMP which oscillates so it allows them to create an AP
- Heart either contracts as a whole unit or not at all. It acts as a functional
syncytium so it is a mass of cytoplasm containing several nuclei enclosed in
membrane with no internal boundaries so electrical activity can spread from
one cell to the next
- Refractory (unresponsive) period is about 250 ms so about same time as
contraction. Cant create AP as ventricles need to refill
- Non contractile cells (autorhythm cells)- 1% of cells
- Contractile cells (cardiac muscle cells)- 99% of cells
- Pacemaker cells become less negative slowly due to slow leakage of na
channels. When cells reach threshold voltage gated calcium channels open
causing rapid depolarisation. Then cell has to repolarise and RMP established.
- Phases of cardiac muscle AP
- Depolarisation: voltage gated Na ion channel cause rapid depolarisation
- Plateau phase of AP: slow Ca channels open
- Repolarisation: slow Ca channels inactive and K channels open
- How does the con of Ca increase in cardiac muscle cells?
- Small amounts of Ca enter the cells through channels
- Triggers SR to release more Ca. This is called calcium induced calcium
response
- Drinking caffeine causes CICR
- SAN where it is initiated and it fires an AP and depolarisation spreads so
atrias contract, reaches AVN transmits AP to the ventricles. Then it reaches to
the bundle of his and back up through the purkinje fibres.
, -
- P=depolarisation
- QRS= ventricles depolarisation (biggest peak as V has more cells and tissues)
- T= ventricular repolarisation
- Junctional rhythm= when SAN isn’t working and the AVN would take over
- 2nd degree heart block= something blocking the AVN and SAN
- Ventricular fibrillation= fast contractions, tectonic contractions, needs
defibrillating so it goes back to normal sinus rhythm
Cardiovascular system II
- Heart is a double pump (very active), has two systems
- Left ventricle pumps blood to systemic circulation
- Right pumps blood to pulmonary system
- Valves allow blood to move through the heart correctly, allows unidirectional
of flow of blood
- Contraction is co-ordinated
- Blood moves in ventricles mostly by gravity and 20% by atrial contraction
- Blood moves through tricuspid valve (three, flat)
- Walls of v have to fully contract to be emptied
- Blood flows through semilunar valves (half, moon)
- Cords of the valves attached to muscles of walls of V these are called chordae
tendinae
- On the finger pulse the dicrotic notch is when SL valve closes so BP drops
- Lub: AV closes, louder and longer, ventricular pressure>atrial pressure so
beginning of V systole
- Dub: SL valve closing, short and sharp, beginning of V diastole
- Heart murmur: results from turbulent blood flow due to valve malfunction
- Stenotic valve: stiff, narrow valve which doesn’t open completely, blood flows
through HP so produces whistling sound
- Insufficient valve: can’t close fully, backflow of blood causes turbulence,
creates swishing noise
- CC: rhythmic changes in cardiac electrical activity, blood flows through
pressure gradient through any opening
- Systole: A/V contracting
- Diastole: A/V relaxing
- Cardiac output: how much blood does the heart pump, (we always talk about
the left ventricle), amount of blood pumped by each ventricle in one minute
- CO: heart rate x stroke volume
- SV is the volume of blood pumped out of one ventricle with each beat
- 5 l/min is the resting cardiac output
- difference between resting and max CO is called cardiac reverse
- SV represents difference between end diastolic volume and systolic volume
- SV= EDV-ESV
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