lecture 4: guyton chapter 14 Flashcards
where is conduction in the heart intiated
SA node
when there is conduction at the SA node explain the depolar
1) signal initted at the SA node (1 cell depolarizes and reaches the rest through synsitium
2) Sign travels to AV node and is slowed down (to allow atrial contraction first)
3) Signal passes through bundle of his (allows signal to pass trhough atria to venticrles
4) purkinje fibers
Why and how is conduction slowed down at AV node
it has less gap junctions
slowed to allow atria to contract befroe ventricles (max blood filling)
why does conduction begin at the SA node
1) it has a more positive resting membrane potential (can reach threshold faster)
2) has leaky sodium channels (sodium easily flows from the outside to the interior of the cells to reach threshold)
parasympathetic nerves release
acetylcholine
which nerve only affects heart rate
parasympathetic
parasympathetic nerves release signals where and what does that mean for the heart
released only at SA and VA node (on atrial side) which means it only decreases heart rhytm
=SLOWS THE SIGNAL DOWN (signal no longer transmitted to ventricles)
sympathetic nerves release signals where and what does that mean for the heart
released through atrial and ventricles which means it affects heart rate and cotnractility
=speeds signal up
what NT do sympathetic nerves release
norepinephrin
What are the 2 reasons that HR increases after sympathtetic activation
1) cells are more slightly depolazrized (more positive membrane potention=easier to reach membrane potential)
2) stimulates sodium entry into the cell (steeper slope)
what are the 2 reasions that HR decreases adter parasympathtic activation
1) cells are slightly hyperpolarized (more negative membrane potential=harder to reach potential)
2) slow is not as steep, less sodium entering in the xell
what are the 5 functions of the cardiovascular system
1) Rapid substance transport to and from the tissues and organs of the body.
2) Rapid removal of metabolic waste (carbon dioxide, urea).
3) Distribution of hormones to the tissues/organs of destination.
4) Immune protection.
5) Temperature regulation.
explai nthe fucntion of Temperature regulation in CV system
Blood vessels deliver heat from the core to the peripheral areas. Temperature regulation is done by the alteration of the blood flow through the skin. Vasodilation (dilation of arterioles and small arteries) and vasoconstriction (the opposite process) determine temperature locally.
explain the fuction of immune protection of the CV system
Specialized blood cells called leucocytes (white blood cells) are used for antibody production.
explain the fucntion of Distribution of hormones to the tissues/organs of destination.
in the CV system
Hormones are secretions of the endocrine glands that have specific effects on the functioning of other tissues/organs.
(ex: insulin is made in pancrease but needs to be delivered all over the body)
exaplin the function of Rapid substance transport to and from the tissues and organs of the body.
in the CV system
transporting things like Oxygen, glucose, amino-acids, fatty acids, water, vitamins, drugs are carried along blood.
explain the fucntion of Rapid removal of metabolic waste (carbon dioxide, urea).
in the CV system
The circulatory system collects the metabolic waste products and delivers them to the excretory organs - e.g., the kidneys, lungs
what are the 5 vessels of the circulatory sytem
1) conduction
2) distributing
3) resistance
4) exchange
5) capacitance
true or false: the pump has an electrical system for regular running
true
what ppermit rapid exchange between the tissues and the vascular channels
extensive system of thin vessels
which is thicker and why: artery or vein
artery because it deals with more pressure
what are the special features of the artery
muscular, highly elastic
what are the special features of the arteriole
muscualr, well innervation
(only 1 monolayer of muscle cells(
what are the special features of capillaries
thin walled, highly permeable
only 1 single layer of endothelial cells where excahange happens
what are the special features of venules
tin walled, with some smooth msucle
what are the special featurse of veins
thin walled (compared to arteries), fairly muscular, and distensibke 1 or 2 layers or smoothe muscles
what is the function of the aorta
pulse dampening and distrbution
what is the function of large arteries
distribution
what is the function of small arteries
distrubution and resistance
what is the function of arterioles
resistance (pressure/flow reg)
what is the fucntion of capillaries
exhchange
what is the function of the venules
exchange, collection and capacitance
what is the function of veins
capacitance (blood vol)
what is the fucntion of the vena cava
collection
Velocity of blood flow is BLANK related to the cross-sectional area of the vascular system
inversly
is blood flow velocity slow or fast in capilarries and why
very slow
they have a large cross sectional area which makes conditions ideal for exchange of diffusible substances
where is velocity of blood flow greatest
in the aorta
rank these from fastest to slowest,
small veins, capillaries, aorta, aterioles
aorta
arterioles
small veins
capilaries
what is the equation for velocity of blood
blood flow/CSA
what is the defintion of blood flow
is the quantity of blood that passes a given point in the circulation in a given period of time.
how is unit of blood flow usally expresed as
as milliliters (ml) or Liters (L) per minute.
what is overall flow of an adult
is 5 liters/min which is the cardiac output.
how does blood usually flow
streamlines with each layer of
blood remaining the same distance from the wall, this
type of flow is called laminar flow.
what happens when laminar flow occurs
the velocity of blood in the center of the vessel is greater than that toward the outer edge creating a parabolic profile.
=vectors in same direction
what are the causes of turbulent flow
high velocities
sharp turns in the circulation
rough surfaces in the circulation
rapid narrowing of blood vessels
diverstion into smaller streams
there is more frction in laminar flow or turbulent
turbulent
what type of flow is silent and which causes murmurs
laminar: silent
turbulent: murmurs
why are murmurs important
are important in diagnosing vessel stenosis, vessel shunts, and cardiac valvular lesions.
what is blood flow to tissues controlled in relation to
tissue needs (at rest=equally distrubitioon, during exercise: skeletal gets alot of blood)
what is cardiac output mainly controlled by
local tissue flow (it is the sum of all local blood flows)
true or false: arterial pressure is controlled dependant of local blood flow control or cardiac output control.
false
independant
what is the difference between blood flow and cardiac output
cardiac: amount of blood ejected per min
blood flow: distribution of blood
what generates blood flow
pumping action of the hert
how does pressure arrise
when flow is opposed by resistance
what is the defintion of BP and the formuala
Blood pressure is the force exerted by the blood against any unit area of vessel wall.
BP = CO x TPR
where is systemic pressure the highest
aorta
true or false: systemic pressure decreaess through pathway and reaches 0 mm in right atrium
true
where does the steepest drop in systemic BP occur
in arterioles
the arterial blood pressure reflects what two factors of arteries close to the heart
Elasticity (compliance or distensibility)
Volume of blood forced into them at any time
blood pressure near the heart is called
pulsatile
where does blood pressure change from pulsatile to continous
aterioles
def of systolic pressure and normal number
pressure exerted in aorta during ventricular contraction
Averages 120 mmHg in healthy adult
what is the def of diastolic pressure
lowest level of aortic pressure
what is pulse pressure
difference between systolic and diastolic pressure
Throbbing of arteries (pulse)
what is the oressure that propels the blood to the tissues
mean arterial pressure
true or false: systolic pressure propeles blood to the tissues
false, MAP does
what is the formula for MAP
MAP=diastolic oressure + 1/3 pulse pressure
Pulse pressure and MAP both BLANK with increasing distance from heart
decline/decrease
what is the normal range of capularry blood pressure
17-35 mm HG
do we want high or low capilarry pressure and why
low
Slow capillary flow allows adequate time for exchange between blood and tissues
explain low pressure of capillaries and the effect on permeability
Most capillaries are very permeable, so low pressure forces filtrate into interstitial spaces
true or false: the venous blood pressure changes alot during cardiac cycke
false it changes little
true or false; there is a small pressure gradient in venous BP (about 15)
true
why is ther elow pressure in veins
Low pressure due to cumulative effects of peripheral resistance
where does the energy of BP loss go
as heat
explain low pressure in venous BP
travelling through systemic circulation it loses alot of velocity (slowed down by resistance in arteriole side)
what junction do we see a large pressure drop
arteriole-capillary junction
wht is the defintion of resistance
is the impediment to blood flow in a vessel.
Measure of amount of friction blood encounters with vessel walls, generally in peripheral (systemic) circulation
how can you calcualte resistance
dividing the pressure difference between two points in a vessel by the vessel blood flow
resistance = delta P/flow
true or false: its better to have serial resistnce cites in circualtion
no its better parallel
why is parallel resistnace in circualtion better
blood will travel where there is least resistance so if one path is blocked it will move to another
=ALLOWS REDIRECTION OF BLOOD TO WHERE ITS NEEDED
what ar ethe 3 imporatnt sources of reisstnace
Blood vessel diameter
Total blood vessel length
Blood viscosity
what is the greatest influence on resistance
blood vessel diameter
frequent changes in BLANK alter peripheral resistance
in diameter
resitance varies inversly with BLANK power of vessel radius
with. 4th power
example the relationship between vessel radius and resistance
increase diamter=increase blood flow= decrease in resistance
ex: if diamter does from 1 to 2 then the flow goes from 1 to 16
the resistance is very sensitiv to changes in///
radius of a vessel
if there is vasocontrictuion, there is an increase or decrase in resistance
increase
what are the major determinatnts of peripheral resistance
small radius arterior
abrupt chahgnes in diameter or fatty plaques from atheroscholeros have what affect on ressitance
increase
=disrupt laminator flow and causes tubbulent flow
=irregular flow motion=increase sresistance
what are the 2 factors that remain constant for resistnace
blood viscority and blood vessel length
explain blood viscocity effect on resistance
The “stickiness” of blood due to formed elements and plasma proteins
Increased viscosity = increased resistance
explain blood vessel length effect on ressitance
longer vessel =greater resistance
do you have higher viscoity in summer or winter
summer
what is poiseuilles law
flow = (pie)(pressure diff)(r)^4/8nl
what is conductance and formula
is a measure of the blood flow through a vessel for a given pressure difference.
Units ml/min per mmHg
conductance = 1/resistance
what is the equation ofr flow
flow=change in pressure diff/ressitance
what is flow through a blood vessel determined by
1) The pressure difference (∆P) between the two ends of the vessel
2) Resistance (R) of the vessel
blood flow is BLANK to blood pressure gradient
directly proptional (ie: if change in pressure inreases, bloow flow increases)
blood flow is BLANK proportional to peripheral resistance
inversity
if R increase, blood flow decrease
what is more imporant in influencing local blood flow because easily changed by altering blood vessel diameter
resistance
if arterial pressure and venous pressure remain contant
resistance decreases
what happens to flow
increases
if arterial and venous pressure stay constant
resistnace icnreases
what happens to flow
decreases
