Chp 19 PP Flashcards
What Structure/function relationships change as one moves through the cardiovascular tree
vessels
Vessels Tunic thickness and composition of the three layers are
variable
capillary beds flow is regulated by
smooth muscle valves
allows flow through capillary bed w/out flow through caps
Metarterioles
are found from arterioles to venules through capillary
Metarterioles
pre-capillary sphincter
- True capillaries
- ring of smooth muscle
- open/close to control flow
- regulated by chemicals
True capillaries
have intermittent vasomotion. How often do they open
, open for flow 5-10 times each minute
Allow exchange of nutrients and wastes between the blood and the tissue cells
Capillaries
Capillary structure
– simple squamous epithelium
- basal lamina - connective tissue
- endothelial cells
3 types of capillaries
continuous, fenestrated, sinusoidal
Vascular Anastomoses that provides collateral supply to some organs and tissues, e.g., skeletal muscles
Arterial Anastomoses
Vascular Anastomoses are
- Arterial Anastomoses
- Arteriovenous Anastomoses
- Venous Anastomoses
Vascular Anastomoses that have thoroughfare channels
Arteriovenous Anastomoses
Vascular Anastomoses that are most common, e.g., deep and superficial veins in limbs and head
Venous Anastomoses
At rest how much of blood volume is located in veins and venules
60%
at rest serves as reservoirs for blood
venous system
what veins in particular serve as reservoirs for blood
veins of the abdominal organs and the skin
how does ANS regulate volume distribution
- vasoconstriction
- vasodilation
- diverts blood to areas with increased metabolic needs
what organ of the body holds 1 liter of blood
spleen
Flow =
ΔP/R
MAP =
mean arterial pressure
CO =
MAP/R
when you go from higher pressure to lower pressure you do what to resistance
decrease resistance
pressure of the blood on the vessel wall is
blood pressure
measure the pressure of a volume in a space
is
blood pressure
norm systole/diastole is
120/80 (mm Hg)
what is BP at the Right atrium
0.0 mm Hg
opposes blood flow because of the friction produced by the vessel walls is
resistance
Factors that affect resistance (R)
1) viscosity
2) vessel length
3) vessel width
if viscosity increases what happens to resistance
resistance increases
“thickness” of the blood is
viscosity
what can cause viscosity
e.g., dehydration, elevated plasma proteins, polycythemia (RBCs), leukemias (WBCs)
resistance is what to viscosity
proportional
resistance is what to vessel length
proportional
what does obesity do to the route lengths within connective tissue
increases
resistance is what to vessel width
inversely proportional
decrease the radius by 1/2 and R increases by
16x
most important in vessels that can change their
size actively
changes in diameter affect
flow
blood cells dragging against the wall is called
vessel wall drag
layers of flow is called
laminar flow
if vessel length increases resistance
increases
if vessel width decreases resistance
increases
Systemic Vascular Resistance (SVR) =
Total Peripheral Resistance (TPR)
all vascular resistance is offered by the
systemic vessels
resistance is highest in
arterioles
largest pressure drop is in the
arterioles
Relationship of the radius to resistance in the arterioles is due to
smooth muscle contraction/relaxation
What does the Windkessel effect have on pulse pressure?
- Decreases pulse pressure
What is the effect of hardening of the arteries on pulse pressure?
Increases pulse pressure
Pulse pressure =
systolic (minus) diastolic
Arterial Blood Pressure
Pulsatile in arteries due to the pumping of the heart
Systolic/diastolic values
Capillaries have what kind of Blood Pressure high or low
relatively low blood pressure
low pressure is good design for capillaries because:
capillaries are fragile - high pressure would tears them
capillaries are very permeable - high pressure forces a lot of fluid out
the volume of blood flowing back to heart from systemic veins is called
Venous return
venous return depends on
pressure difference from beginning of venules (16 mmHg) to heart (0 mmHg)
any change in right atrial (RA) pressure changes
venous return
what act as assistance for venous return
- skeletal muscles act as pumps
- respiratory pump
how does the respiratory pump assist venous return
- inhaling causes a lowered pressure in the thoracic cavity
- primarily to pull air into the lungs
- helps to draw blood into thorax via pulmonary circulation
how does the skeletal muscle act as a pump for venous return
-contracting muscles squeeze veins
-force blood back to the heart
valves prevent back flow
Velocity of blood flow - inversely proportional to
the total cross sectional area (CSA) of vessels
inversely proportional to the total cross sectional area (CSA) of vessels
Velocity of blood flow
what has
- total CSA (cross sectional area) = 3-5 cm2
- velocity = 40 cm/sec
Aorta
what has
- total CSA = 4500-6000 cm2
- velocity = 0.1 cm/sec
Capillaries
what has
- total CSA = 14 cm2
- velocity = 5-20 cm/sec
Vena Cava
site of exchange between blood and tissues
Capillary Function
delivery of nutrients and removal of wastes
Capillary Function
slow flow allows time for molecules to diffuse
Capillary Function
Mechanisms of nutrient exchange
in capillaries
diffusion - O2, CO2, glucose, AA’s, hormones, electrolytes – diffuse down [ ] gradients
lipid soluble molecules can pass through cell membrane easily
water soluble molecules generally require transport mechanisms to enter/exit cells
fluid movement in capillaries
- Fluid diffuses out and is reabsorbed across the capillary walls
- Starling’s law of the capillaries
Forces driving the movement of fluid
in capillaries
Hydrostatic pressure capillary (HPc)
Hydrostatic pressure interstitial fluid (HPif)
Osmotic pressure capillary (OPc)
Osmotic pressure interstitial fluid (OPif)
is the net effect of all four forces at any point along the capillary
Net filtration pressure (NFP)
On average, how much fluid entering the tissues on the arteriole side is reabsorbed on venous end
85%
neural control of the cardiac centers comes from the
medulla
has a medullary area dedicated to control of blood vessels
Vasomotor center
sends sympathetic output to blood vessels
Vasomotor center
receives sensory input from different sources
Vasomotor center
what different sources does the vasomotor center receive sensory input from
baroreceptors (blood pressure)
chemoreceptors (O2, CO2, H+, HCO3-)
- normal amount of vasoconstriction or vasodilation is called
Vasomotor tone
Vasoconstricts or vasodilates as needed through sympathetic output to blood vessels
Vasomotor center
ANS can vary the vasomotor tone which
varies the delivery of blood to particular regional capillary beds
what short term mechanism for maintaining blood pressure are located at carotid sinuses and aortic arch
Baroreceptor
do baroreceptors monitor blood pressure
yes
regulates the activity of the sympathetic nervous system (vascular tone)
and help maintaining blood pressure short term
baroreceptors
Carotid bodies, aortic bodies
Monitor changes in indicator chemicals (O2, CO2, H+, HCO3-)
Chemoreceptor initiated reflexes
increased CO2, increased H+, decreased O2 (stresses) result in
increased sympathetic activity and increased blood pressure
what are the higher brain centers (areas above medulla) - that influence short term mechanism for maintaining blood pressure
cortex and hypothalamus
not involved in minute-to-minute regulation of short term blood pressure regulation
cortex and hypothalamus
when do the cortex and hypothalamus influence the vasomotor center
temperature changes
stressful emotional situations
What are the short term chemicals that influence blood pressure
renin
angiotensin
aldosterone
what does Renin/ACE do to influence blood pressure
enzymes from kidney/lung
catalyze formation of Angiotensin I/II
what does Angiotensin II do to influence blood pressure
vasoconstrictor
stimulates Antidiuretic Hormone ADH, thirst
stimulates aldosterone release for Na+ & H2O reabsorption
releases epinephrine and norepinephrine in coordination with activity from the Sympathetic Division of the ANS
Adrenal medulla
diverts blood from the skin and abdominal organs to the skeletal muscles
Adrenal medulla
increases heart rate, stroke volume and, therefore, cardiac output & blood pressure
Adrenal medulla
also stimulates vasoconstriction at high levels
ADH
targets kidneys to retain water
ADH
(ADH action is inhibited by
alcohol
has osmoreceptors in hypothalamus trigger release from the neurohypophysis
Antidiuretic Hormone (ADH) or Vasopressin
released from atrial cells in response to increased blood vol & increased BP
Atrial Natriuretic Peptide (ANP)
stimulates vasodilation, increases Na+ and water loss, antagonizes Aldosterone, inhibits thirst
Atrial Natriuretic Peptide (ANP)
controls blood volume
through nervous control - ANS and
hormones
Renal mechanism
what mechanism regulates in the short term by adjusting blood pressure and adjusting blood flow to different capillary beds
regulation in the long term by adjusting blood volume
Renal mechanism
target the kidneys
increased BP, increases urine flow to decrease blood pressure is done by what mechanism
Renal mechanism
decreases blood pressure, decreases urine flow to increase blood pressure is done by what mechanism
Renal mechanism
short term mechanisms to maintain blood pressure are
Neural Control - Cardiac Centers in medulla (Vasomotor center)
Baroreceptor
Chemoreceptor
Cortex and hypothalamus
Chemicals
Renin - Angiotensin - Aldosterone
Adrenal medulla
Antidiuretic Hormone (ADH) or Vasopressin
Atrial Natriuretic Peptide (ANP)
Maintaining Blood Pressure: Long Term Regulation is done by
Renal mechanism
what is local automatic adjustment of blood flow to match specific local tissue metabolic needs called
Autoregulation (local control)
In Autoregulation Warming does what to control blood flow
increases vasodilation
In Autoregulation Cooling does what to control blood flow
increases vasoconstriction
In Autoregulation Chemical changes in local tissues generate
metabolic byproducts
vasodilators or vasoconstrictors
in myogenic control smooth muscle controls what
resistance
increased stretching does what to contraction
increases contraction
decreasing stretching does what to contracting
decreases contraction
what has fine tuned control with wide variation in rate of blood flow
skeletal muscle
what organ in the body has minimal variation in rate of blood flow
and minimal nutrient storage, so adequate flow must be maintained!
brain
how is skeletal muscle influenced by the brain when involved with blood flow
brain directs the sympathetic division for NE release in response to the degree of muscular activity
α receptors - vasoconstriction
β receptors - vasodilation
skeletal muscles metabolic regulation in tissue affect O2 how
low O2 causes vasodilation, increasing flow
high O2 cause vasoconstriction, decreasing flow
three ways skin affects blood flow
adjusting rate of flow aids in temperature regulation
controls skin’s capacity as a blood reservoir
sympathetic and local metabolic regulation
what is flow regulated by in the lungs
O2
high o2 in the lungs does what to blood flow
high O2 causes vasodilation to increase flow – opposite of muscle
low O2 in the lungs does what to blood flow
low O2 causes vasoconstriction to decrease flow – opposite of muscle
how does the heart regulate blood flow
through sympathetic and local metabolic regulation
what kind of flow does the heart have depending on metabolic/pumping activity
variable
a portal system that transfers venous blood from one capillary bed to another capillary bed before the blood is returned to the heart
Hepatic Portal System
collects venous blood from five abdominal organs and routes the blood to the liver for specific processing of transported molecules
Hepatic Portal System
Where does HPS collect venous blood from five abdominal organs
- stomach: toxins (ethanol)
- small intestine: nutrients, toxins
- large intestine: nutrients, toxins
- pancreas: insulin, glucagon
- spleen: RBC breakdown products
bring oxygen and nutrients from the placenta to the liver and then to the heart of the fetus
Umbilical veins
in what circulation does the ductus venosus bypasses liver
Fetal Circulation
Fetal Circulation
3 Right > Left shunts
because oxygenated blood is derived from the placenta
- ductus arterious -> ligametum arteriosum
- foramen ovale -> fossa ovalis
- interventricular shunt -> no remnant
where is oxygenated blood is derived from in fetal circulation
the placenta
sudden dramatic loss in blood pressureor sudden decrease in circulatory flow is called
Circulatory Shock
Acute hemorrhage (or other sudden fluid loss as from vomiting or diarrhea) is called
Hypovolemic Shock
Loss of vasomotor tone as from anaphylaxis, neural malfunction, or poisons (septicemia) is called
Vascular Shock
Loss of cardiac output due to heart failure
is called
Cardiogenic Shock
