2 week 10 Flashcards
a) describe where the P QRS and T waves are in terms of the cardiac cycle phases
b) T or F: electrical signals always occur after heart contractions
a) P = end of ventricular diastole/start of atrial systole, QRS complex = end of atrial systole to mid isovoumetric ventricular contraction, T = end of ventricular systole
b) false – BEFORE*
describe left ventricular volume thru cardiac cycle
- at 100 from previous pump’s late V diastole (100mL)
- atrial systole = 135mL (peak)
- isovolumic V contraction = stays at 135mL
- V systole = decreasing
- early V diastole = 65mL (low)
cycle repeats… rises to 100mL during late V diastole!
describe left atrial pressure thru cardiac cycle
- increases during contractions
- low and relatively steady
describe left ventricular pressure thru cardiac cycle
- starts to increase at isovolumetric V contraction
- peaks increase during V systole
- levels off at late V diastole
describe aortic pressure thru cardiac cycle
- also peaks during V systole because SL valves have opened and blood is filling the aorta
- decreases during early V diastole as well
- A = SL valves have opened (beginning of V systole)
- B = SL valves have closed (end of V systole)
- B also = “dicrotic notch” where blood bounces off SL valve
what are the heart sounds, specifically sound 1 and sounds 2?
- sound 1 = AV valve closes (end of A systole)
- sound 2 = aortic SL valve closes (dicrotic notch, aka end of V systole)
summarize atrial systole regarding pressure and volume
- increase in atrium pressure
- increase in ventricle volume
summarize isovolumic ventricular contraction regarding pressure and volume
- increase in ventricular pressure
- ventricular volume remains same (pressure not strong enough to open valves yet)
summarize ventricular systole regarding pressure and volume
- [aortic SL valve opens]
- aortic pressure increases
- ventricular volume decreases bc ejects blood
summarize early ventricular diastole regarding pressure and volume
- ventricular volume drops
- [valve closes]
- ventricular pressure drops
summarize late ventricular diastole regarding pressure and volume
- [passively filling ventricles]
- slight increase in ventricular pressure
- slight decrease in aorta pressure
describe the innervation of the heart by the autonomic nervous system
- sympathetic nerves activate pacemaker nodes and ventricles
- parasympathetic nerves inactivate pacemaker nodes only
how does the autonomic nervous system adjust the SA node?
SYMPA:
- use NE and beta receptors
- increase Na and Ca influx
- increase rate of depolarization
- increase heart rate
PARASYMPA:
- use Ach and muscarinic receptors
- increase K efflux, decrease Ca influx
- hyperpolarize
- decrease heart rate
T or F: parasympathetic system does NOT affect the ventricular myocardium
true
factors affecting stroke volume (3)?
- contractility
- end diastolic volume
- afterload
how does contractility affect SV?
- sympathetic neurons project on heart’s conduction system and myocardium
- hormonal connection to contractility – E, NE, insulin, glucagon and thyroid hormone (i.e., EXTRINSIC CONTROL, controlled by brain)
what is the frank-starling law?
greater filling of the heart leads to greater end diastolic volume and drives greater stroke volume (i.e., volume in, volume out, INTRINSIC CONTROL)
“the more the heart is filled during diastole, the more forcefully it contracts during systole”
how does the frank-starling law work on the sarcomere?
- myosin attaches to actin
- pulls actin filaments together (sliding of actin filaments over myosin filaments), shortening muscles
- there is an optimal sarcomere length
how does the nervous system shift the frank-starling relationship curve? why does this matter?
increased SYMPA activity = higher
decreased SYMPA activity = lower
matters bc enhances performance during exercise
what is afterload?
- pressure that ventricles have to work against (i.e., resistance) as they pump blood out of the heart
- ↑ in MAP ↓ SV
- ↑ afterload ↓ SV
how are blood vessels organized (5)?
arteries, arterioles, capillaries, venules, veins
describe each blood vessel (5)
- arteries = muscular and elastic
- arterioles = muscular and well innervated
- capillaries = thin walled, highly permeable
- venules = thin walled, some smooth muscle
- veins = thin walled, muscular, distensible
what do large arteries do? (2)
- carry blood from heart to tissues
- stiff and inflexible pressure regulators
key feature of resistance arteries?
can change diameter to influence flow!
key function of metarterioles?
allow for blood to bypass capillary beds
T or F: capillaries are the largest and least numerous blood vessels?
F – smallest (but large SA) and most numerous
characteristics of continuous capillaries? (4)
- joined endothelial cells
- permeable to small molecular size or high lipid solubility (e.g., O2, CO2, steroids)
- less permeable to water-soluble substances (e.g., Na+, K+, glucose, amino acids)
- impermeable to proteins
characteristics of fenestrated capillaries? (3)
- large pores
- permeable to proteins and large molecules
- purpose = move substances across walls (e.g., kidney, intestine, liver, bone marrow)
which capillaries are most common?
continuous
what do large veins do? (3)
- carry blood from tissue to heart
- have valves
- act as volume reservoirs (high compliance)
what does “compliance of a vessel” mean?
- change in volume as pressure changes
- ex high compliance: BIG volume changes = SMALL pressure changes bc expand (good for holding blood, veins)
- ex low compliance: SMALL volume changes = BIG pressure changes bc less expandable (good for regulating pressure, arteries)
T or F: veins hold most of the blood volume
true
what is the significance of the 90mmHg pressure gradient between the atria?
ensures blood flows in one direction
what is poiseuille’s law in words?
- resistance increases as length increases (more wall interaction)
- resistance increases as viscosity increases (bc friction)
- resistance decreases as radius increases
T or F: vessel radius has small effect on resistance/flow.
F – HUGE effect bc 4th power
which blood vessel vasodilates/constricts to control BP?
arterioles
diff bw series and parallel flow?
- series flow: single path (right to left heart)
- parallel flow: each organ is fed by a separate artery
pros of parallel flow? (2)
- each organ receives fully oxygenated blood
- each organ’s blood flow can be independently regulated depending on metabolic needs without affecting other organs
how is blood flow re-distributed in exercise?
- more blood flows to liver and GI tract + kidneys at rest (“rest and digest”)
- more blood flows to skeletal muscle and skin at max exercise (80-85%)
- heart: same % but more L during exercise
- brain: less % during exercise but ~same L
- skeleton/fat/tissues: overall less during exercise
