Exam 2 Part I - regulation of BP and CO Flashcards
Blood pressure is the function of ___, ___ and ___
Blood, vascular tree, heart
The left ventricle creates and initial pressure that results in an
Aortic pressure
Pulse pressure is (equation)
Systolic pressure (SBP) - diastolic pressure (DBP)
Pulse pressure is ~
~40mm Hg
Augmentation is seen in what kind of arteries?
Large arteries
Augmentation is likely due to ________ in the arterial tree
Pulse reflection
Pulse reflexion causes summation of pulse wave-forms and may correlate with a condition like
Aneurysm
Systemic venous BP is also called
Central venous pressure
Central venous pressure (CV) averages about
0 mmHg
systemic vasculature has an average pressure about
100 mmHg
Venous pump is a term that describes the combination of ____ and ____
Valves and skeletal muscles
The primary role of valves is to prevent
Retrograde flow in low-pressure blood vessels
What are the 2 pumps in the systemic circulatory systeM/
- Left ventricle
2. Collective venous pump
What do left ventricles do?
Establish arterial pressure and flow to body tissues
What does the collective venous pump do?
Establish a venous pressure and flow back to the heart
What are hydrostatic forces?
Gravity — force due to pressure at rest
In an average person of average height in a standing position at rest, the venous pressure rises to _____ in the feet
90 mmHg
In an average person of average height WHILE WALKING, the venous pressure drops to _____ in the feet
25 mmHg
What is the impact of hydrostatic forces in the head?
Negative venous pressure
BP =
Cardiac output X peripheral resistance
CO =
Stroke volume X heart rate
Peripheral resistance is due to many factors including:
— blood volume
— viscosity
— size of vascular container (primarily r^4)
When you put all the factors together (including cardiac output formula and peripheral resistance) you end up with, BP =
~ SC and HR and collective ‘r^4’
OR
BP = CO/ ‘r^4’
Mean arterial blood pressure (MAP) is what?
Average blood pressure from left ventricle that is responsible for flow (Q) in the arterial tree
Mean arterial blood pressure (MAP) =
DBP + 1/3 (SBP - DBP)
In other words: MAP is diastolic pressure plus 1/3 * (systolic pressure - diastolic pressure)
Blood pressure control systems can be fast or slow acting; high or low “____”
Gain (power to correct)
There are two main systems of blood pressure control:
Nervous and renal mechanisms
Short term adjustments in BP are best done with ______
Rapid-acting ANS
Rapid-acting ANS (blood pressure control system) affects
Heart and vessels
Long term regulation is done by controlling
Volume of blood in vascular compartment
What are the pressure-sensors in the arterial tree close to the out put of the left ventricle?
Aortic and carotid baroreceptors
Where are signals from the aortic arch and carotid bifurcation baroreceptors delivered to in the brain?
Cardiovascular center in the brain medulla
When carotid sinus nerve impulses, what does that do to cardiac output?
Slows heart rate
Decreases contractility
When vagus nerve impulses, what does that do to cardiac output?
Slows heart rate
Decreases contractility
When carotid sinus OR vagus nerve impulses, what does that do to peripheral resistance?
Decreases vasoconstriction
When sympathetic cardiac nerve impulses, what does that do to cardiac output?
Accelerates heart rate
Increases contractility
When sympathetic cardiac nerve impulses, what does that do to peripheral resistance?
Increases vasoconstriction
How fast and what kind of gain does arterial baroreceptor reflex get in controlling BP?
Fast and high gain
Arterial baroreceptor reflex reaches a peak within what length of time?
15 seconds
Arterial baroreceptor reflex has a responsiveness that is lose in what timeframe?
2-4 days
The function of arterial baroreceptor reflex is what?
Sudden changes in BP
What system is used for postural changes?
Arterial baroreceptor reflex
Aortic and carotid chemoreceptors are within small “organs” called
Aortic and carotid bodies
Aortic and carotid baroreceptors are used in _________ while aortic and carotid chemoreceptors are used in ________
Arterial baroreceptor reflex; arterial chemoreceptor reflex
How fast/slow and how effective is the arterial chemoreceptor reflex?
Fast and high gain
What is the peak timeframe of arterial chemoreceptor reflex?
60 seconds
Arterial chemoreceptor reflex is very strong when
MAP drops below 80 mmHg
Atrial stretch reflex uses stretch-receptors in the walls of the
Right atrium
Atrial stretch receptors are not pressure receptors, they are actually
Volume receptors
How fast/slow and what gain is atrial stretch reflex?
Fast and unknown gain
Bainbridge reflex dominates when _______; baroreceptors dominate when _______
Blood volume rises; blood volume diminishes
Intravenous infusion leads to…
Increased R atrial pressure —> atrial receptor stimulation —> Bainbridge reflex and INCREASED heart rate
BUT ALSO
Increased cardiac output —> increased arterial pressure —> baroreceptor reflex and DECREASED heart rate
What serves to minimize venous damming of blood?
Bainbridge reflex
Atrial stretch can cause a hormonal effect from
Atrial natriuretic factor (ANF)
Atrial natriuretic factor (ANF) is released with increased
Atrial pressure/stretch
Atrial natriuretic factor (ANF) functions to
Decrease blood volume and decrease BP
A nervous control “system” that involves neurons of cardiovascular control center:
CNS Ischemic Response
How fast/slow and what kind of gain does the CNS Ischemic Response get?
Fast and high gain — aka last ditch effort
CNS Ischemic Response uses neurons of the
Medullary “pressor” area due to cerebral ischemia
The CNS Ischemic Response is a reflex triggered from
Very slow moving blood that fails to remove CO2 from cardiovascular center
What does the pressor region do?
Evokes vasoconstriction, cardiac acceleration, and myocardial contractility
In the pressor region, vasoconstrictor sub-areas are
Topically active and responsible for vasomotor tone
The depressor region functions to
Inhibit Pressor area
Decrease sympathetic outflow and increase parasympathetic activity
Withdrawal of sympathetic tone is the primary mechanism for nervous-induced
peripheral vasodilation and low BP
Humoral control system that uses hormones from adrenal medulla that act as sympathetic neurotransmitters
Epinephrine system
Epinephrine system uses what neurotransmitters?
Epinephrine (80%) and norepinephrine (20%)
Epinephrine and norepinephrine land on what kind of receptors?
Alpha and beta adrenergic receptors
When epinephrine and norepinephrine land on alpha and beta adrenergic receptors, it causes
Peripheral vasoconstriction and increased cardio output
How fast is the Epinephrine system? And what is the gain?
Fast-acting and unknown gain
Epinephrine system is under what kind of control?
Smooth muscle control
What is a property of the arterial system (and vascular smooth muscle) that causes an increase or decrease in constant pressure on arterial vessel that results in a change in contractile state?
Stress-relaxation behavior
Stress-relaxation behavior has what kind of speed and gain?
Slow acting, low gain
What system is a property of the capillaries of the body?
Capillary fluid shift (edema)
How fast and what kind of gain does capillary fluid shift get?
Slow acting and low gain
What system can account for peripheral edema in pathological states?
Capillary fluid shift
A humoral control system that uses hormones from kidney and blood
Renin-angiotensin system
What hormones does the renin-angiotensin system use?
Renin and angiotensin II
Renin-angiotensin system works closely with what system?
Aldosterone system
Renin-angiotensin system is how fast and what kind of gain?
Slow-acting and low gain
The renin-angiotensin system’s participation is modified by
- increase or decrease in BP at different arterioles
- increase or decrease in sympathetic stimulation to kidneys
- increase or decrease in sodium levels in nephron
What are the effects of angiotensin?
- Cause cardiac myocytes to hypertrophy
- cause thirst
- stimulate nephron to retain Na+ and H2O
- cause efferent arteriolar vasoconstriction and increase glomerular filtration
- stimulate release of ADH from posterior pituitary
** all to increase BP **
A humoral control system that uses a hormone from the adrenal cortex
Aldosterone system
Aldosterone works closely with what other BP regulatory system
Renin-angiotensin system
The aldosterone system is how fast and what kind of gain?
Slow-acting and low gain
Aldosterone system’s participation is modified by:
- increase or decrease in angiotensin II levels
- K+ levels to adrenal cortex
A humoral control system that uses osmotically sensitive neurons in hypothalamus to produce a hormone that is released from posterior pituitary gland
Vasopressin system
What is the alternate name for vasopressin?
Anti-diuretic hormone (ADH)
What does vasopressing / ADH do?
Acts as both a cardiovascular pressor agent and renal fluid retention agent
V1 receptors on vascular smooth muscle can cause
vasoconstriction
What speed and gain is vasopressin system?
Slow-acting and unknown gain
A fluid (and humoral) control system that uses the kidney
Renal-blood fluid (volume pressure) system
The renal-blood fluid system involves what?
Nephron and renin-angiotensin system
The renal-blood fluid (volume pressure) system is how fast and what kind of gain?
Slow-acting and very high gain
Which BP control system is the ultimate mechanism?
Renal-blood fluid (volume pressure) system
Because it works by adjusting the amount of fluid in the vascular compartment, rather than just manipulating existing fluids of the body.
Pressure diuresis
Increased arterial BP leads to increased water disposal
Pressure natriuresis
Increased arterial BP leads to increased salt/sodium disposal
Diuresis
Formation of urine
What system relies on diuresis?
Renal-blood fluid (volume pressure) system
A moment-to-moment adjustment process that attempts to stabilize and match input and output (of both salt and water)
Renal output curve
ADH causes kidneys to
Retain water
How does salt intake increase extra cellular fluid volume?
- Stimulates hypothalamic thirst center
- Stimulates hypothalamic production of anti-diuretic hormone (ADH)
- ADH causes kidneys to retain water
2 primary determinants of long-term arterial pressure
- Level of water and salt intake (net fluid vol)
2. Behavior of kidneys as represented in the acute renal output curve
Renal output curve can be changed by
- addition of hormonal controls
- abnormalities of nephrons
Angiotensin acts directly on kidneys to
Retain salt and water
Angiotensin acts on adrenal glands to
Increase aldosterone secretion which increases salt and water retention in the kidneys
The pressure in the system is created primarily from
The heart
Cardiac output =
Venous return
What determines CO?
By the end-diastolic volume which is dictated by venous return
What determines venous return?
The size of peripheral vascular tubes
What determines the r^4 (all vessels of the body) / size of vascular container?
Release of local factors from metabolizing tissues
In other words, metabolizing tissues determines venous return which determines C.O.
If there is increased tissue metabolism, what are the next steps?
- Increased in local metabolites
- Increased vasodilation
- Increased flow into venous system
- Increased venous return
- Increased cardiac output
- Increased flow to original metabolizing tissues
If there were 2 outputs in the cardiovascular system and cardiac output is 1 them, what is the other?
Tissue output (from the body) coupled with venous pump
*this is another way to think about it
If you think of the systemic circulation as having 2 pumps with the left ventricle for Cardiac Output being 1, what is the other?
Collective skeletal muscles of the body (for venous return)
Remember the equation:
Q = ∆P * r^4 where Q is flow, ∆P is pressure and r^4 is the size of all the vessels/vascular container…
∆P must be maintained, how is it maintained?
By the many BP regulatory systems that regulate the redistribution (and a few manage the volume) of blood
Given the limited supply of blood and changing needs of the body, what becomes an important balancing act?
Distribution of blood
What system can modify both cardiac output and the peripheral resistance and manage the distribution of blood?
Sympathetic nervous system
If the body has an increased work-load, what will happen to CO and BP?
Increase
How does changing blood chemistry alter breathing?
Increased H+ leads to increased ventilation
Breathing serves as additional venous pumping
Respiratory pump
“Warming down”
Continue to move though not fully exercising that is needed to prevent sudden post-exercise pooling of blood through venous pumping
Exercise and related metabolism of skeletal muscles is often measured by amount of oxygen consumed by the body
VO2, volume of O2 consumed per minute
VO2 levels at rest? But can rise to?
250 ml/min at rest
3,000 ml/min or more
A maximum aerobic limit of VO2 is called
maxVO2
A-V O2 difference is
Measure of tissue metabolism (or O2 extraction)
A-V O2 = Atriovenous oxygen difference
In exercise, as total body Q increases, what happens?
Redistribution
- increased Q to skin for sweating
- stable Q to brain
- increased Q to heart
- decreased Q to gut
- decreased Q to kidneys
Q = flow
During exercise, CO can raise from ~5 l/m to
> 25 l/m
See graph on Pg 35 if Beck doesn’t insert it here
