Cardiovascular Physiology Flashcards
What are the general characteristics of circulatory systems?
1. pump/propulsive structures
* main: heart
* accessory pumps: help gets blood to main pump -> leg muscles that contract around vessel
2. system of tubes, channels or spaces through which fluids flows
3. fluid that circulates the system
- mammalian - blood; other - hemolymph
What is the difference between cardiovascular systems in small animals vs bigger animals?
- Unicellular + some small animals lack circulatory systems and rely on diffusion to transport molecules since their radius is small enough
- As animals get bigger and more complex, diffusion is too slow to transport nutrients and gases
What is the goal of the circulatory system?
- To enable RAPID circulation of fluids
- To exchange nutrients, gases, wastes and help with homeostasis
Closed circulatory system
- fluid stays in vessels and does not bathe the tissue
- fluid is distinct from interstitial fluid -> fluid that is not blood that bathes tissue
- have evolved many times, support higher flow rates, better at controlling where the fluid goes
Open circulatory system
- fluid enters sinus at least once therefore directly in contact with tissue
- blood flows in one direction (enter/leave heart) and once it reaches the end of the tube, empties into bathing open space mixing with interstitial fluid
What kind of circulatory system do arthropods have? Explain the process/path.
OPEN SYSTEM where blood is pumped from posterior to anterior (anterograde flow = forward)
1. blood exits through holes -> ostia
2. …to tissues that need blood (wing + leg muscles) so nutrients are dropped off, waste picked up)
3. remaining fluid exits through head (driven by accessory pumps in antenna)
4. blood circulated throughout body w/ current until picked up into ostia again
*accessory pumps throughout body ensure blood is circulated wherever necessary
What are the parts of the circulatory plan of vertebrates?
- arterial system
- oxygenated blood
- distributes blood + regulates blood pressure - venous system
- deoxygenated blood
- returns blood to heart + acts as a blood volume reservoir - capillaries
- site of gas + nutrient exchange - heart
- creates pressure that drives blood flow
- has sensory + endocrine functions
What are the main components of blood?
1. plasma (55%): water electrolytes, proteins, nutrients, hormones, waste products, etc.
- hydrophilic, H2O containing fluid
- helps buffer blood (maintain pH)
2. white blood cells (<1%)
3. red blood cells/erythrocytes (45%)
- proteins involved in O2 + CO2 transport (ie haemoglobin, carbonic anhydrase)
What are the different types of blood cells in insects vs vertebrates? (Make a table)
Refer to table made in summary sheet
How to determine percentage of plasma and cells?
Hematocrit: proportion of blood composed of RBCs
- ideal hematocrit = 40-50% (~45% in humans)
- low = 25-30% -> may be anemic meaning there is an issue w/ RBC production
- high = leukemia -> more WBCs
Where does the left side of the heart pump blood to vs the right side?
Left = systemic
Right = pulmonary
Why does ____ ventricle have a much thicker heart tissue than ____?
left;right
This is because more contractile force is needed to pump blood systemically. The right side being less muscular is actually good or else we would blow out our heart with every heart beat.
What do the semilunar valves do?
Open up to allow blood to be passed to lungs or to aorta (pulmonary arteries)
How do atrialventricular valves open and what are the two types?
Valves between atria and ventricles -> opening is triggered by pressure
- Left = bicuspid
- Right = tricuspid
Vertebrate blood vessels
Describe what each vessel is made of and describe the pressure change
Veins + arteries
- tunica externa
- tunica media
- tunica intima
- endothelium
- veins: thin-walled, not as muscular therefore they are flexible + distensable
- arteries: thick
Venules
- tunica externa
- endothelium
Arterioles
- tunica media
- endothelium
Capillaries
- endothelium
- Pressure is HIGHEST in arteries close to heart
- drops further from heart
- LOW pressure as it gets to venous system but accessory contractile structures help blood get back to heart
tunica externa: connective tissue
tunica media: smooth muscle tissue
What is the law of circulation?
Blood flow equation
Coronary artery disease
Blood flow = deltaP/R
- more resistance = less flow
- less resistance = more flow
- blood flow is inversely proportional to R -> increased friction = bad blood flow
- coronary artery disease: plaque builds up -> resistance increases, blood flow decreases, heart tissue starved of O2 + nutrients
Cardiovascular pressures and velocity
Refer to graphs + explanations in summary sheet
Pressure differences in morphology of heart chambers
Pulmonary: LOW pressure and resistance circuit
1. prevent fluid filtration in lungs
2. prevents damage of alveoli
3. minimizes workload by right ventricle
Systemic: HIGH pressure and resistance circuit
1. ensure good fluid filtration in systemic capillaries
2. maintain high flow rates to many tissues
3. left ventricle has high workload
Describe the mammalian cardiac cycle.
Include diastole and systole moments
Refer to diagram in summary sheet
When are the AV + semilunar valves open/closed during the cardiac cycle?
Refer to graph/diagram in summary sheet
What are the different types of hearts?
Myogenic
- able to produce rhythmic contraction on its own through specialized, adapted contractile cells that generate their own electrical activity
Neurogenic
- contract only in response to neural stimulation
- mostly invertebrates
What are cardiac cells interconnected and innervated by?
Interconnected by gap junctions and innervated by sympathetic neurons
What are the three types of cardiac muscle?
Draw the flowchart
1. pacemaker cells
2. conduction fibers
3. contractile fibers
Describe impulse conduction in the heart and the ECG.
Refer to diagram in summary sheet
What is stroke volume?
Also draw the graph
Volume ejected by ventricles w/ each heartbeat (atria contracting)
SV = end diastolic volume (EDV) - end systolic volume (ESV)
- volume in ventricles is GREATEST at end of atrial contraction = EDV
What is the ejection fraction formula?
Ejection fraction = SV/EDV
- increases with exercise
What is cardiac output?
Volume of blood pumped out of heart per min
CO = SV (ml/beat) x heart rate (beats/min)
What are high-performing athletes better in terms of cardiac output?
Since they have an increased cardiac output, they have more O2 and nutrient distribution
Why is lower stroke volume bad?
Cardiac output decreases and therefore you won’t be able to circulate as much blood through body
- might enter hypoxic states: inability to fuel enough O2 throughout all O2 deficient tissues efficiently over time
Why is cardiac output important and how can it be changed?
It maintains blood flow through body and can be altered by changing heart rate and stroke volume
How does autonomic innervation affect cardiac output?
- PNS + SNS innervate heart at SA node, AV node, atrial and ventricular contractile cells
- there are more sympathetic nerve fibers at ventricular innervation
- autonomic system only increases/decreases HR
- resting HR is maintained by PNS but pacemaker cells regulate too
What are the factors affecting cardiac output?
Refer to diagram on summary sheet
How are pacemakers innervated by the ANS?
Refer to flowchart on summary
Describe the action potential of a pacemaker cell.
Refer to labelled graph in summary
How does GPCR activation lead to cardiac muscle contractions?
Refer to diagram in summary
How does GPCR activation facilitate increase in heart rate?
- Ca + HCN (Na+K) channels open and shut with freq. + efficiency
What is the effect of SNS innervating the adrenal medulla?
It systemically releases epinephrine + norepinephrine from sympathetic neurons. Thus, more Na and CA channels open and the rate of depolarization + freq. of APs increase
Increased heart rate is accompanied with an increase in…
Also describe HOW and the end result
Stroke volume
- sympathetic innervation increases heart rate by stimulating SA+AV nodes
- it also enhances force of contraction + speeds of relaxation
- tension also rises
- Ca removed more quickly through activation of beta adrenergic receptors in contractile fibres
- END RESULT: more blood ejected from heart (lower ESV) = stroke volume does not decline
Describe parasympathetic control of contractions.
- acetylcholine (released from parasympathetic neurons) binds to muscarinic2 AchR (a GPCR) on cardiac tissue
- the G-protein does two things…
- Gi subunit: CLOSE Ca channels, inhibiting adenyl cyclase = decrease in Ca influx
- beta,gamma subunit: OPEN K channels = increasing K out - increases time it takes for depolarization
- heart rate decreases
What are the variables of cardiac regulation?
Also draw diagram
1. cardiac output
- increase heart rate = increase cardiac output
- therefore more fluids can be brought to exercising muscles
2. peripheral resistance
- high pressure flow so blood can be transported full distancce
3. blood pressure
- systemic capillaries
For diagram: refer to summary sheet
Where are baroreceptors located and how do they present there?
- carotid arteries (bulbs bilaterally -> carotid sinus: detecting pressure out of heart)
- aortic arch (stretch sensors)
- large arteries
What are baroreceptors?
Sensory neurons that detect blood pressure changes by sensing stretch in blood vessel walls
- afferent neurons from baroreceptors project to medulla control centre
Neural activity of arterial baroreceptors
Pressure and AP freq.
- increase in BP = increase in AP freq. sending signal through sensory neurons back to control centre
- decrease in BP = decrease in AP freq.
Describe efferent pathways in baroreceptor reflex.
Afferent baroreceptor signals are transmitted to cardiovascular control centre in medulla oblongata. Then depending on low or high BP, outputs are from parasympathetic or sympathetic ganglia. This is due to innervation of preganglianic neurons. Either…
- parasympathetic ganglia are innervated by control centre (medulla oblongata innervates PNS for further parasympathetic activity)
OR
- excitatory neurons from medulla oblongata innervate spinal cord to cause more sympathetic activation
Describe how homeostasis of BP and volume is maintained by baroreceptors.
Refer to flowchart on summary sheet.
What are the different routes across capillaries?
- intercellular areas: water-soluble molecules
- straight through membrane: lipid-soluble substancces
- fenestrated (tiny holes): for smaller water-soluble molecules
- transport vesicles: slower mechanism, large substances
Bulk flow across capillaries
Refer to diagram + explanation on summary sheet
