Physiology of Vessels Flashcards
The regulation of blood pressure must change in response to ______.
cellular activity
a collection of mechanisms that influence the active and changing circulation of blood
hemodynamics
Circulation control mechanisms must accomplish two functions:
- maintain circulation
- vary the volume and distribution of the blood circulated
_____ is the only means by which cells can receive materials necessary for survival and have wastes removed.
circulation
Primary Principle of Circulation: Blood flows because a ________ exists between different parts of its volume; this is based on Newton’s first and second laws of motion.
pressure gradient
the symbol used to represent a pressure gradient. ___ represents the higher pressure and ___ represents the lower pressure.
P1-P2
- P1
- P2
A _____ gradient is needed to maintain blood flow through a local tissue
perfusion pressure (PP) gradient
A blood pressure gradient drives blood flow from the ______ to the _____.
right ventricle to the left atrium
fluid always travels from high pressure to low pressure. This is called
pressure gradient
The primary determinant of arterial blood pressure is the ____ of blood in the arteries
volume
A ____ relationship exists between arterial blood pressure and arterial blood volume
direct
volume of blood pumped out of the heart per unit of time.
cardiac output (CO)
the amount the cardiac output can increase above the resting cardiac output
cardiac reserve
Within limits, the longer or more stretched the heart fibers are at the beginning of contraction, the stronger the contraction.
The amount of blood in the heart at the end of diastole determines the amount of stretch or preload placed on the heart fibers
Starling’s Law of the heart
Frank-Starling mechanism
factors that affect strength of myocardial contraction and therefore stroke volume
inotropic factors
one mechanical factor that helps determine stroke volume:
myocardial fibers at the beginning of ventricular contraction.
Contractility can also be influenced by chemical factors:
- neural: norepinephrine
- endocrine: epinephrine
- triggered by stress, exercise
ratio of stroke volume to end-diastolic volume
ejection fraction
usually expressed as a percentage
In a healthy adult, the ejection fraction is at least __%
55%
the pumping work the heart must do to push blood into the arteries
afterload
the harder it is to push blood out of the ventricles, the lower the _____.
stroke volume.
Abnormally high afterload from flow resistance in the arteries can cause _____.
heart failure
_______ and _______ are located in the aorta and carotid sinus.
They affect the autonomic cardiac control center in the Medulla, and therefore parasympathetic and sympathetic outflow, to aid in control of blood pressure.
Cardiac pressoreflexes:
aortic baroreceptors and carotid baroreceptors
factors that change the rate of the heartbeat
chronotropic factors
_________ reflex:
- located at the beginning of the internal carotid artery
- sensory fibers from carotid sinus baroreceptors run through the carotid sinus nerve and the glossopharyngeal nerve to the cardiac control center
- parasympathetic impulses leave the cardiac control center and travel through the vagus nerve to reach the SA node
carotid sinus reflex
_____ reflex:
- sensory fibers extend from baroreceptors in the wall of the aortic arch through the aortic nerve and through the vagus nerve to terminate in the cardiac control center
- stimulation causes the cardiac control center to increase vagal inhibition, thus slowing the heart
aortic reflex
______ produce changes in the heart rate through the influence of impulses from the cerebrum by way of the hypothalamus
emotions
other reflexes that influence heart rate (4):
- emotions
- exercise
- increased blood temperature or stimulation of skin heat receptors
- decreased blood temperature or stimulation of skin cold receptors
resistance to blood flow imposed by the force of friction between blood and the walls of its vessels
peripheral resistance
factors that influence peripheral resistance:
- blood viscosity
- diameter of arterioles
blood viscosity is determined mainly by the proportion of ______, but also partly by the number of ______.
red blood cells (hematocrit),
protein molecules
arterial blood pressure tends to vary directly with ____.
peripheral resistance
_____ is caused by viscosity and small diameter of arterioles and capillaries
friction
_____ have a muscular coat that allows them to constrict or dilate and change the amount of resistance to blood flow
arterioles
controls changes in the diameter of arterioles; it plays a role in maintenance of the general blood pressure and in distribution of blood to areas of special need
vasomotor control mechanism
controls changes in the diameter of arterioles; it plays a role in maintenance of the general blood pressure and in distribution of blood to areas of special need
vasomotor control mechanism
see slide 24 for more info
local mechanism produce vasodilation in localized areas
hyperemia
amount of blood returned to the heart by veins
venous return
____ occurs when a change in blood pressure causes a change in vessel diameter (because of elasticity) that accommodates the new pressure and thereby keeps blood flowing
the stress-relaxation effect
the pull of gravity on venous blood while sitting or standing tends to cause a decrease in venous return
orthostatic effect
facilitate venous return by increasing the pressure gradient between the peripheral veins and the venae cavae
venous pumps
facilitate venous return by increasing the pressure gradient between the peripheral veins and the venae cavae
venous pumps:
- respirations
- skeletal muscle contractions
inspiration increases the pressure gradient between peripheral and central veins by decreasing central venous pressure and also by increasing peripheral venous pressure
respirations
promote venous return by squeezing veins through a contracting muscle and milking the blood toward the heart
skeletal muscle contractions
changes in ________ change the amount of blood returned to the heart
total blood volume
The _____ the total volume of blood, the greater the volume of blood returned to the heart
greater
the mechanisms that change total blood volume most quick;y, making them most useful in maintaining constancy of blood flow, are:
those that cause water to move quickly:
- into plasma
- out of the plasma
the ______ system recovers the fluid not recovered by the capillary and returns it to the venous blood before it is returned to the heart
lymphatic
reduces amount of water lost by the body by increasing the amount of water the kidneys reabsorb from urine before the urine is excreted from the body
this mechanism is triggered by input from baroreceptors and osmoreceptors
the anti-diuretic hormone (ADH) mechanism
renin is released when blood pressure in the kidneys is low
- leads to increased secretion of aldosterone which simulates retention of sodium
- angiotensin II is an intermediate compund that causes vasoconsriction
this complements volume-increasing effects of renin and promotes an increase in overall blood flow
Renin-Angiotensin-Aldosterone System (RAAS)
adjusts venous return from an abnormally high level by promoting the loss of water from plasma, thereby causing a decrease in blood volume
increase urine sodium loss
Atral-Natriuretic-Hormone (ANH) mechanism
Arterial blood pressure is measured with the aid of a _______ and ______.
sphygmomanometer and stethoscope
force of the blood pushing against artery walls as ventricles contract
systolic blood pressure
force of the blood pushing against artery walls when ventricles are relaxed and during isovolumetric ventricular contraction
diastolic blood pressure
difference between the systolic and diastolic blood pressures
pulse pressure
average blood pressure in the arteries for the perfusion of tissues
mean arterial pressure (MAP)
a mercury-filled pressure sensor used in clinical and research settings to measure the arterial blood pressure quickly and accurately
sphygmomanometer
volume of blood circulating through the body per minute
minute volume of blood
_____ Law:
minute volume = pressure gradient / resistance
the minute volume of blood is determined by the magnitude of the blood pressure gradient and peripheral resistance
Poiseulle’s Law
______ mechanism:
reveals important information about the cardiovascular system, blood vessels, and circulation
expansion stores energy released during recoil, conserving energy generated by the heart and maintaining relatively constant blood flow
pulse mechanism
each pulse starts with ventricular contraction and proceeds as a wave of expansion throughout the arteries
it gradually dissipates as it travels, disappearing in the capillaries
pulse wave
the ____ can be felt where ever an artery lies near the surface and over a bone or other firm background
pulse
detectable pulse exists only in large veins, most prominently near the heart; this pulse is not clinically important
venous pulse
Where pulse can be felt (7)
- radial artery: at the wrist
- temporal artery: in front of the ear or on the outer side of the eye
- common carotid: anterior edge of the SCM muscle
- facial artery: lower margin of the lower jawbone
- brachial artery: bend of the elbow, along inner margin of the biceps muscle
- femoral artery: middle of groin
- popliteal artery: behind the knee
occurs when force exerted by the arterial blood vessel exceeds 140/90 mmHg
hypertension HTN
lower than normal blood pressure. Acute or chronic.
hypotension
