Week 6 The cardiovascular system (heart & cardiac cycle) Flashcards
Define the Cardiac Cycle.
all evwnts associated with the flow of blood through the heart during single heart beat.
Define a Systole.
phase of the cariac cycle in which the heart is contracting
Define a Diastole.
phase of the cariac cycle in which the heart is relaxing
What are the features in an Arthropod Heart?
They are neurogenic(require external stimulus), humans are the oppostie - homogenic
shape and size VERY variable
Common features:
- pump hemolymph –> circulation via arteries
- blood returns to heart via ostia
- Ostia has valves
Arthropods Hearts: What controls the cardiac cycle?
Neurons of the cardiac ganglion needed (found in the surface of the heart, among heart muscle cells)
- generates rhythm
- spontaneous rhythmic depolarisations
- initiate rhythmical contractions of the heart
Arthropod Hearts: the cardiac cycle - how do systole contractions work?
systole - contractions:
- impulses –> heart
- initiates heart beat and closes ostia
Effects:
- msucle cells contract
- ↓ volume in the heart cahmbers
- ↑ pressure on circulatory fluid
- blood flows out into circulation
- + contraction pulls on ligaments
Arthropod Hearts: the cardiac cycle - how do diastole contractions work?
diastole - relaxation:
- cease impulses –> heart
- suspensory ligaments recoil - elastic recoil outwards
- pulls apart walls of heart
- ↓ volume in the heart
- ↓ pressure on chambers
- ostia opens
- ↓ pressure sucks fluid into heart
Arthropods Hearts also act as what?
pressure pumps (systole) & suction pumps (diasole)
Vertebrate Hearts: What are 4 distinct layers of the complex walls?
- endothelium (inner)
- myocardium (middle)
- epicardium (outer)
- pericardial sac (visceral & parietal)
Vertebrate Hearts: What is the endothelium layer?
- thin layer of conntective tissue
- & layer of endothelial cells
Vertebrate Hearts: What is the myocardium layer?
- caridac muscle - cardiomyocyctes
- divided into several layers
Vertebrate Hearts: What is the epicardium layer?
- thin external membrane
- continuous with visceral layer of pericardium
- may contain nerves (depending on heart) - regulates heart & coronary artieries
Vertebrate Hearts: What is the pericardial sac (visceral & perietal) layer?
- double-walled membranous sac (contains fluid)
- function: lubricates heart, decreasing friction
What is the caridac anatomy of a fish?
(water-breathing)
- 4 chambers
- blood flow into sinus venousus –> atrium –> ventricle –> bulbous arteriousus
What is the caridac anatomy of an amphibian?
- 3 chambers (2 artria, 1 ventricle)
- pulmonary vein –> LA
- sinus venosus –> RA
- LA & RA –> ventricle
- conus arteriousus (spinal fold) controls the blood flow going into:
- systemic arteries
- pulmocutaneous artery
What is the caridac anatomy of birds & mammals?
- 4 unobstructed chambers
- Left side: thin walled atrium, thick walled ventricle
- Right side: thin walled atrium, thin walled ventricle
(ventricles dont have to be symmetric in size, as some preform different functions)
Caridac anatomy of birds & mammals: what does the left ventricle do?
Left Ventricle: pumps blood to systemic circulation
systemic = high pressure and resistance
–> stronger force of contraction needed
Caridac anatomy of birds & mammals: what does the right ventricle do?
Right Ventricle: pumps blood to pulmonary circulation
pulmonary = lower pressure and relatively low total resistance
- large number of capillaries arrnages in parallel
- shorter distance, shorter vessels
Caridac anatomy of birds & mammals: What are the different types of valves?
- Atrioventricular valves: between atria and ventricles (R = tricuspid valve, L = bicuspid valve)
- Outflow valves: pulmonary and aortic (semilunar)
heathy valves have very little resistance - small pressure gradient causes them to open.
The structure of the heart:
What are the considerations of the cardiac cycle:
considerations:
- rhythmic changes in electrical acitivty of the heart
- alternate periods of contraction (systole) & relaxation (diasole)
- resultant changes in pressure
- drice BF (high to low pressure) causing opening/closing of heart valves
What are the phases of the cardiac cycle?
- ventricular filling (during diastole)
- isovolumetric contraction (systole)
- ventricular ejection (systole)
- isovolumetric relaxation (diastole)
Volume stays contstant but pressure changes
Define a Stoke volume.
the amount of blood ejected by ventricle (SV)
Define the cardiac output.
volume ejected per minute (SA x heart rate)
the cardiac cycle begins with sinoatrial (SA) node that initiates the heart beat
What occurs during Phase 1 of the cardiac cycle?
Ventricular Filling
- LA pressure higher than LV
- Mitral valve opens, blood flows into LV
- LA contracts - ‘atrial kick’
What occurs during Phase 2 of the cardiac cycle?
Isovolumetric contraction
3. LV contracts
- LV pressure rises (Isovolumic contraction)
- AV opens when V pressure exceeds A pressure
- Ventricular ejection
What occurs during Phase 3 of the cardiac cycle?
Ventricular ejection
- End-systolic pressure falls
- LV pressure falls below AP and AV shuts
- Period of isovolumic relaxation
- LV pressure falls below A pressure and MV opens and V refills
What occurs during Phase 4 of the cardiac cycle?
Isovolumetric relaxation
What is the relationship between pressure and volume: P-V Loops?
you can relate the phases of the cardiac cycle on the PV loops
How can you measure the stroke volume with use of the P-V Loop?
What phase of the cardiac cycle is systole?
isovolumetric contraction & ventricular ejection
Arthropod hearts are myogenic. T/F?
False. They are neurogenic (require external stimulus), humans are the oppostie - homogenic
Arthropod hearts act as a pressure pump during which phase of the cardiac cycle?
during systole
Is the myocardium of mammals more compact or spongy?
more compact
How many chambers do amphibian hearts have?
3 chambers
What are the 2 types of valve that exist in the heart of brids & mammels?
Atrioventricular valves & Outflow valves
During isovolumetric contraction in mammals, pressure in the ventricles is greater than pressure in the atria. T/F?
True. AV opens when V pressure exceeds A pressure
