physiology Flashcards
what is the function of the CVS (5) - what is the main theme?
transportation of : gas
nutrients, metabolites, hormones, heat
transportation
how many times dose the heart beat in 70 years - what does this show
2.5 billion times
the heart is amazingly reliable
what shows the heart is remarkably flexible (3)
pump can vary output
vessels can redirect blood
vessels can store blood
why do we need a Vascular system
because we are not single celled and diffusion only takes part over 1mm
the left and right ‘‘pumps’’ are said to be in what
series with one another
why in terms of the CVS is series so important
it means the output of both must be equal for function
what are the 2 main examples of vascular beds in series
gut to liver
hypothalamus to anterior pituitary
what are most vascular beds - what does this mean (2)
in parallel
all tissues get oxygenated blood
allows regional redirection of blood
what is special about the gut being in series with the liver (2)
the liver still has its own blood supply
the nutrients absorbed from the gut go directly to the liver for storage
what is a problem with the evolution of the coronary blood supply
every time it contracts it cuts of its own blood supply
why is the hypothalamus in series with the anterior pituitary
as the hypothalamus diffuses releasing factors into the blood supply for the anterior pituitary to pickup down stream and release hormones
what are the 3 biggest O2 consumers
the abdominal organs
skeletal muscle
heart
why doses the cardiac output of the biggest O2 consumers vary
because it shows weather the system is effective
why is the kidneys CO so much greater than its O2 consumption
due to the kidneys job of cleaning the blood
what is the equation for flow
change in pressure /resistance
why does the skin have a similar CO vs O2 consumption as the kidneys
as the skin is the thermoregulatory
how does resistance changed
diameter changes of the blood vessels mainly arterioles
what is the pressure difference
mean arterial pressure - central venous pressure
where is the mean arterial pressure measured
in the arteries
where is the central venous pressure measured
in the vena cava
what do arterioles act as
the taps - controlling resistance to the vascular bed
what vessels does blood pass through from first to last
arteries, arterioles, capillaries, venules, veins
what is the aorta an example of
elastic arteries
what are the features of elastic arteries
wide lumen, elastic wall
what is the function of the elastic arteries
to dampen pressure fluctuations but absorbing and smoothing out
what are all other arteries other than the aorta
muscular arteries
what is the function of muscular arteries
to be low resistance conduits and get the blood to the arterioles
features, narrow lumen , thick contractile wall
what are arterioles examples of
resistant vessels
what is the function of resistant vessels
control resistance which in turn controls flow
allow regional redirection of blood
what are the features/ from of arterioles
narrow lumen, thin wall
what are capillaries examples of
exchange vessels
what features do exchange vessels have
narrow lumen and thin walls
what are venules examples of
capacitance vessels
what are veins examples of
capacitance vessels
what are the features of capacitance vessels
wide lumen, distensible wall (allows the vessel to swell and expand )
what is the job of the capacitance vessels
like a capacitor it is to allow fractional distribution of blood (allows for some storage) between veins and heart
how much blood is in the venous system
2/3
what is the pulmonary trunk
the initial ARTERY that comes out of the right ventricle
what is the septum (s) in relation to CVS
the interventricular and interatrial septum’s job is to separate the right and left ventricles and atrium to stop mixing/ shunting of blood.
what is the mitral valve
mitral = bicuspid
2 cusps
stops blood being regurgitated into the left atrium from the left ventricle during contraction
what is the tricuspid valve
a valve with 3 cusps
stops blood regurgitation from the right ventricle to atrium
what is fractional distribution
what the venous system dose to store a bit of blood by distending - keeping the series correct
what is the T-tubule
deep holes in cell
what is the sarcolemma
the membrane that surrounds the whole of the muscle cell
where is the Z line
in the middle of the T-tubule
what do the GAP junctions form
protein channels that let electrical current through them - the electrical connection between them - mass contraction
what are the thin filaments in muscle
actin
what is the sarcoplasmic reticulum
a big calcium cell storage
what are desmosomes
the stiches between the cell - leading to a p
how long is a cardiac action potential - compared to skeletal
250ms of cardiac
vs 2ms of skeletal
why is a cardia action potential so long - why is this
a cardiac action potential is long so Ca2+ and Na+ can enter the cell
the entry of more Ca2+ leads to a greater contraction
so contraction strength can be regulated by how much Ca2+ is let in (length of action potential) - unlike skeletal muscle
can cardiac muscle exhibit tetanus
no
what is tetanus (tetanic contraction)
when skeletal muscles add multiple contractions on top of one another - i.e. holding something for long)
what is the name of how the gap junctions and desmosomes are arranged (alternatively)
intercalated disk
what do the cells that act as pacemakers have
unstable resting membrane potentials that lie a lot closer to threshold and spontaneously reach threshold
what dose the defibrillator do
top the hear to resent the pacemakers
what are the 4 stages of a non-pacemaker action potential
resting membrane potential - high resting permibalitiy ofK+
initial depolarisation - more Na+
Na+ permeability shoots up
plateau - decrease in K+ and more Ca2+ (L type)
repolaisation - decrease Ca2+, increase in K+
what happens in a pacemaker action potential
K+ gradually decreases
a weird Na+ increases
then a late increase in Ca2+ (T type) (initial booster to get into orbit) leads to the firing of the action potential
which leads onto Ca2+ (L type) (main thruster to cause the action potential)
what are the drugs that modulate electrical activity in the heart
Ca2+ channel blockers - decrease force of contraction
cardiac glycosides - increase force of contraction
what factors other than drugs have an effect on electrical activity (7)
sympathetic and parasympathetic
temperature 10bpm per 1oC
hyperkalaemia (high K+)- fibrillation and heart block
hypokalaemia (low plasma K+) - fibrillation and hear block
hypercalcemia (high plasma Ca2+) -increased HR & force of contraction
hypocalcaemia (low plasma Ca2+) - decreased HR & force of contraction
what is the annulus fibrosis - what happens during conduction
its a ring connective tissue (WITHOUT GAP JUNCTIONS) around the tri/bicuspid valves that stops the conduction of a action potential from the atrium to the ventricle
how dose the wave of excitation get past the annulus fibrosus
by passing through the atrioventricular node(like a gateway) and trough the bundle of His (like a tunnel)
how fact dose the action potential travel in the atrium
0.5 m/sec
how fat does the action potential travel through the atrioventricular node - why?
0,05m/sec - to act as a delay box - time for atrium to get the last bit of blood into the ventricles
what are myocardial cells (myocytes)
the cardiac muscle cells
what are the purkinje fibres and what is there function
the fibres that make up the rapid conduction system at 5m/sec
its fast so the contraction is powerful enough for the blood can be pushed and circulated
what happens as ventricular depolarisation begins
atrial repolarisation
how do electrocardiograms work (ECG)
due to the wave of depolarisation/repolarisation leading to the formation of extracellular waves
can a ecg record a single cell
no due to the fact that the extracellular wave is so small
what is the order of the hear cycle
atrium depolarisation
ventricle depolarisation(atrium repolarisation)
atrium repolarisation
what are the waves of a ECG
P, QRS, T
what does the P was correspond to
atria depolarisation
what does the QRS was correspond to
ventricular depolarisation
what does the T was correspond to
ventricular repolarisation
what is the excitiation contration coupleing system
musculoskeletal system is intricately intertwined with the nervous system, allowing muscle contraction and movement
why is the cardiac depolarisation so long
both Na and Ca enter
Ca entry, excite controls contraction.
how long is cardiac muscles refectory period
250ms
same length as the action potential
where does skeletal and some of your cardiac muscle sit normally
-90mV
