Circulatory System Flashcards
What are the two circuits that make up the circulatory system?
Systemic and Pulmonary Circuits
Which side of the heart pumps blood into the pulmonary circuit?
Right
Which side of the heart pumps out oxygenated blood into the systemic circuit?
Left
What are the 3 major kinds of blood vessels?
Artery, Capillaries, Veins
What are the 3 layers of the artery?
Tunica Intima, Tunica Media, Tunica Adventitia
What is the innermost layer of the artery?
Tunica Intima
Which layer of the artery is mainly composed of smooth muscle fiber and elastic fiber?
Tunica Media
What layer of the artery is made of fibrous tissue (collagen and elastic fiber) and surrounds the artery?
Tunica Adventitia
What are the three types of arteries according to structure?
elastic, muscular, resistance
What is the function of elastic arteries?
Conductive: conducts blood from the heart to the smaller arteries.
What is the unique feature of the elastic artery?
The tunica media is made mostly of elastic fibers.
The elasticity creates “pressure” and aids in accepting large volumes of blood.
What is the function of muscular arteries?
Distributive: responsible for delivering blood to specific organs and tissues
What kind of arteries are the aorta and pulmonary artery?
elastic artery
What is the unique feature of the muscular artery?
Tunica media is made mostly of muscular fibers.
What kind of arteries are the radio-ulnar and hepatic artery?
muscular artery
What is the function of resistance arteries?
Regulatory: constrict or dilate to control blood pressure
What is the unique feature of resistance arteries?
barely contains elastic fibers
Which artery sustains chronic (tonic) contraction of the muscles?
arterioles
Which artery dissipates pressure directly after a cardiac contraction?
elastic artery
What are the smallest blood vessels?
capillaries
What is diameter of capillaries?
5-8 μm
What do you call the first branches that come out of the arteriole system?
terminal arterioles
What do you call the arterioles located at the end of terminal arterioles?
Meta-arterioles
What is the mechanism and function of meta-arterioles?
They have a
sphincter-like
mechanism that
allows their closure to
prevent blood from
going into a particular
segment of the
capillary bed
What is the major connection between the arterioles and venules?
Thoroughfare/Shunt
What blood vessel experiences the greatest pressure drop from the arterial system going into the capillary network?
arterioles/resistance vessels
What blood vessel is responsible for microcirculation?
capillaries
The capillaries’ tunica media and tunica adventitia is very thin. T/F?
F. There is no tunica media or adventitia. It has ENDOTHELIAL layer ONLY.
What system brings back post-metabolic blood to the heart to exchange nutrients?
veins/venules
Veins are also known as _________ vessels.
capacitance vessels
At any given time, blood is stored in the ________.
veins
How much blood volume (%) is at the veins at any given time?
64%
The veins have a large amount of adventitial layer, why?
to prevent collapse
What primarily retains the shape of veins?
blood
What are the layers found in veins?
endothelial, tunica media, tunica adventitia
What are the drivers of venous flow?
vein valves, calf pump, respiratory pump
What is the function of vein valves?
prevents backflow and helps with volatile nature of blood (e.g. gravity pushing blood down, pressure changes, sluggish forward movement)
Briefly explain the calf pump.
calf muscles squeeze causing the veins to constrict.
When the calf muscles are contracted, will the vein valves be closed or open?
open
When the calf muscles are relaxed, is the vein valves closed or open?
closed. prevents backflow
How does the respiratory pump work?
Every time the chest expands, it causes a decrease in INTRATORACIC pressure. This serves as a suction causing the blood from legs to go up (to abdominal and thoracic cavity)
Who discovered the closed loop circulation?
William Harvey
Who described the viscosity and mechanisms of blood flow?
Newton
What did Hales contribute in the understanding of the circulatory system?
blood pressure and windkessel (tool to measure blood pressure non-invasively)
Who combined the relationship of flow, pressure, fluid viscosity, and tube dimensions into one equation?
Poiseuille
According to Poiseuille’s law, what are the beneficial factors that aid flow?
Pressure difference & diameter of tube (directly proportional to flow)
What factors are indirectly proportional to flow? (hint: resistance factors)
viscosity of fluid & length of tube (indirectly proportional to flow)
What kind of flow does the circulatory system have?
pulsatile flow
Why does the circulatory system have pulsatile flow?
due to systolic and diastolic phases of the heart
What does “systolic” mean?
heart contraction
What does “diastolic” mean?
heart relaxation
What causes the forward flow of blood?
recoil of elastic arteries of aorta and first branches
Describe the slope between the pressure difference of the arterial system coming from the heart to the entrance of the capillaries.
steep downward slope (more flow)
What causes the pressure to dissipate at the entrance to the capillaries?
parallel circuits, multiple branching, pressure loss due to turbulent flow
What kind of flow does the capillary microcirculation have?
non-pulsatile flow
What prevents the transmission of systole onto the capillary bed?
arterioles
Is the pressure high or low at the entry of the capillary beds?
low pressure
What pat of the capillary bed experiences a rapid drop in pressure?
arteriolar bed
Is the venous system pulsatile or non-pulsatile?
non-pulsatile
The slope between P1 to P2 in the venous system is ______ steep.
Not. This means flow is sluggish
What is the flow of the venous system?
non pulsatile + phasic flow (related to breathing)
What happens in the case of venous congestion?
not enough blood flow to the heart, + venous system keeps on dilating
Which of the two has lower pressure in the venous system: P1 or P2?
P2
When nervous impulses to the vein decrease, it will result in a dilated vein, and therefore increased blood storage in the venous system. What condition will occur?
neurogenic shock
What are the side-effects of venous hypertension and congestion and how does it manifest?
promotes a cycle of venous inflammation = damage of venous endothelial walls and venous valves = more venous dilation
What are the 2 categories in which we can categorize the distribution of fluids (i.e. fluid compartments)?
intracellular fluid (ICF) and Extracellular fluid (ECF)
What is the normal amount of ICF (% and L)?
40% of body weight (24L)
What is the average cardiac output during heavy exercise?
25L/min
What is the average cardiac output at rest?
5L/min
How much blood (%) does the muscle receive during heavy exercise?
80-85%
How much blood (%) does the muscle receive at rest?
15-20%
Which organ(s) receive the highest amount of blood at rest?
Gastrointestinal/Digestive Tract (20-25%)
What factor has the greatest the effect on blood flow?
radius of blood vessel
What is the decrease in lumen size, causing less blood towards the organ?
Vasoconstriction
Give 4 common vasoconstrictors.
- norepinephrine/epinephrine
- Angiotensin II
- Vasopressin
- Sympathetic stimulation
What happens during vasodilation?
increase in lumen size + more blood towards the organ
Give 4 common vasodilators.
- Nitric Acid
- Endothelin
- Serotonin
- Parasympathetic
What stimulates the muscle fibers of the blood vessels to contract and cause vasoconstriction?
firing rate of sympathetic nerve fibers
What happens when there is a slowing of firing rate of the sympathetic nerve fibers?
less stimulation of the muscle fibers = vasodilation
Neural control of blood happens via what?
reflex arc + feedback loop
Briefly describe the neural control for circulation (list steps).
Carotid viral receptors and
chemoreceptors → medulla → paraganglionic
fibers → cardiovascular organs.
What can a hemorrhage result to besides the loss of blood?
decrease in arterial pressure
What receptor detects the decrease in arterial pressure?
baroreceptor at the carotid and aortic arch
What system acts as a hormonal response to controlling the flow of blood?
renin-angiotensis-aldosterone system
What organ produces renin?
kidneys
What organ secretes angiotensinogen?
liver
What triggers the release of angiotensin I?
renin acts enzymatically on angiotensinogen
A few seconds to minutes after formation of
angiotensin I, angiotensin II splits off from it. T/F?
T
What does angiotensin II affect?
- kidneys: increases retention of sodium and water
- brain: stimulates it to release antidiuretic hormones + increase thirst response
- adrenals: increase aldosterone production (preserves sodium)
- blood vessels: cause vasoconstriction (increases blood pressure)
What gland releases catecholamines?
adrenal gland
What are the effects of catecholamines?
- heart: increases heart rate and heart contractility
- liver: converts glycogen to glucose
- digestive system: decrease activity
- bronchioles: dilation > lungs take in more oxygen
- arteries and veins: cause vasoconstriction
What is the net effect of catecholamines?
vasoconstriction
What triggers the local autoregulatory response?
changes in blood pressure
The local autoregulatory response mainly acts at the capillary level. T/F?
T
Vasodilation or vasoconstriction only happens at a certain segment of the capillary bed. T/F?
F. It can happen at the whole capillary bed too.
The brain blood flow is controlled by what?
carbon dioxide and hydrogen ion
What theory states the idea that as arterial pressure is decreased, oxygen and nutrient delivery is also decreased, resulting in the release of local vasodilators (adenosine, CO2, Lactic Acid, etc.)?
Metabolic theory
Adenosine, CO2, Lactic Acid, ADP compounds, Histamine. K+ ions, H+ ions, Prostacyclin, Bradykinin, and Nitrous oxide (NO) are products of what?
metabolism
What is the myogenic theory?
Myogenic regulation is intrinsic to the vascular smooth muscle. As arterial pressure falls, the arterioles have an intrinsic property to dilate in response to the decrease in wall tension.
According to the myogenic theory, an increase in systemic arterial pressure causes cerebral vessels to ___________.
contract/constrict
According to the myogenic theory, a decrease in systemic arterial pressure causes cerebral vessels to ___________.
dilate (there isn’t much force to cause the muscle to stretch)
The Neural/Baroreceptor Reflex increases ___________ outflow.
sympathetic
Hormonal (RAAS) increases
__________.
angiotensin II
The Local Autoregulatory Response (capillaries) decreases _________ pressure.
capillary
