L12- Pt 2 Flashcards
Intrinsic regulation
“Inside”
- build in control
Extrinsic regulation
“Exit” or External
Controlled externally
Cardiac output (co)
Volume of blood ejected/min
Why is cardiac output regulated?
To increase/ decrease blood flow to meet changes in energy (ATP) needs
Equation for cardiac output
CO= HR x SV
(ml/min) (beats/min) (ml/beats)
What is cardiac output (CO) at rest and maximal exercise?
Rest = 5000ml/min
Max exercise = 20000ml/min
If CO is constant and HR increases, what will happen to SV?
SV (stroke volume) will decrease to maintain Cardiac output
If HR is constant and SV increases, what will happen to CO?
CO will increase
How is CO regulated ?
By heart rate and Stroke volume
Regulating heart rate (HR)
(Extrinsic regulation)
- sympathetic NS ➡️ increases hr
- parasympathetic NS ➡️ decreases hr
3 factors that affect Stroke volume (SV)
- End diastolic volume (EDV
- Total peripheral resistance (TPR)
- Contractility of ventricles
End diastolic volume (EDV)
- ventricular volume at the end of diastole (relaxation)
Frank starling law of the heart
Increase EDV ➡️ allowing for more optimal sarcomere length & increase Ca2+
➡️ increases cross bridge formation
What affects end diastolic volume?
Venous return
What affects venous return (VR)?
Blood pressure & venous pressure
Total peripheral resistance (TPR)
Frictional resistance to blood flow from vessels
(Artery diameter)
During vasoconstriction TPR decreases, which causes the arteries diameter to decrease which causes SV to ________
Increase ; heart contracts less hard to maintain sv
If TPR increases, the arteries diameter must _______ and the sv will _________
Arteries = increase
SV = decrease
What affects TPR?
- Sympathetic nervous system ( increases overall TPR)
- vasoconstriction (viscera/skin)
- vasodilation (skeletal muscle) - Parasympathetic nervous system (decreases overall TPR)
- vasodilation (intestinal tract)
Contractility of ventricles
Strength of ventricular contraction
What affects Contractility of ventricles?
- Sympathetic NS (Extrinsic)
- innervates myocardial cells ➡️ increasing ca+ in sarcoplasm ➡️ increase cross bridge formation ➡️ increase contraction strength - Frank starling law (intrinsic)
- increase EDV ➡️ stretch myocardial cells ➡️ allow sarcomere @ optimal length ➡️ increases contraction strength
Why regulate blood flow?
To redistribute blood flow as needed
- not enough blood to fill all capillaries at once
Redistributed blood flow is needed for :
- Thermal regulation
- Meet metabolic demands
- exercising or @ rest - Maintain Blood pressure (BP)
- hydrated or dehydrated
Equation for blood flow (F)
F= p/R
Pressure/ Resistance
Blood flow (F)
Volume of blood moving/time
Pressure (P) - blood pressure
Driving force created by heart contraction (arteries)
Resistance (R)
Effects vessel diameter
Total peripheral resistance (TPR)
Resistance caused by all blood vessels in the systemic circuit
If P generated by the heart stays the same, and R increases due to vessels contracting, what will happen to F through the vessels?
F: flow through the vessels will decrease
In what vessel does constriction/ dilation occur that allows for redistributed blood?
Arterioles
Parallel arranged arterioles allows selective change in BF to organs
TRUE or FALSE
True
What are the two smooth muscle locations where distribution of blood flow is regulated?
W/in capillaries; arteriolar smooth muscle & pre-capillary sphincter
Pre-capillary sphincters
Decrease blood flow to tissue
Intrinsic control mechanism for blood flow
Hint: 2 types
- Metabolic
- metabolic waste + increase temp. In interstitial fluid = vasodilation - Myogenic
- increase BP = vasoconstriction
Decrease BP = vasodilation
Extrinsic control mechanism for blood flow
- caused by nervous and endocrine system
Acts on arteriolar smooth muscle:
1. Control BP
2. Regulate BF to muscle for exercise/ skin for temp. Regulation
Angiotensin II (hormone)
Constricts arterioles
ADH/ Vasopressin
Constricts arterioles
Sympathoadrenal control on blood flow
Rest: sympathetic tone = basal level body wide vasoconstriction
Flight/ Fight:
- skin/ viscera arteriolar smooth muscle ➡️ NE bind to alpha receptor = vasoconstriction
- skeletal muscle arteriolar smooth muscle ➡️ E bind to beta receptor = vasodilation
OR ACH bind to muscarinic receptors = vasodilation
Parasympathetic nervous system control on blood flow (BF)
Rest/digest: limited to vasodilation (Ach) to intestines & genitalia
Blood pressure
Pressure of blood in the cardiovascular system
Why is blood pressure regulated?
Maintain adequate blood flow to tissues
Equation for BP
BP=CO x TPR
How is BP regulated?
- HR, SV, TPR
By using baroreceptor reflex
Baroreceptor reflex
Assures enough driving pressure (BP) to meet blood flow needs to tissues
How is BP altered if ONLY HR is increased, SV and TPR stay the same?
BP would increase
What are the two locations where stretch receptors are found w/in the heart?
Carotid baroreceptor and Aortic baroreceptors
Carotid baroreceptors
Wall of carotid arteries
Aortic baroreceptors
In wall of aortic arch
How do baroreceptors work?
Increase BP at rest
- stretching of baroreceptors = increase AP firing to cardiac control center in medulla
In the nFL for baroreceptor reflex what is the stimulus
Sensors
Integration center
Effector
Stimulus = increase/ decrease of blood pressure
Sensors = baroreceptors - sensory neurons ( aortic & carotid baroreceptor)
Integration center = medulla oblongata
Effector =
1. Heart - SNS increasing heart rate & PNS decreasing heart rate
2. Arterioles - increase SNS = increase TPR
Why regulate blood volume?
Maintain blood pressure
- maintain osmolarity
(Effects venous return)
What affects blood volume?
- h2o balance
( gain or loss water) - blood loss
What is water balance
Water intake = water secreted
How do we gain and lose water daily?
Gain : eating & drinking
Loose :
Urinating, feces, sweat, breathing
Fluid compartments - ISF , plasma, cells
Intracellular fluid = 67%
Blood plasma = 8%
Interstitial fluid = 25%
What happens when a person is dehydrated
BV⬇️ = VR⬇️ = EDV ⬇️ = SV ⬇️ =CO⬇️= BP ⬇️
Capillary exchange
- allow nutrient absorption
Between fluid compartments ( depends on BV & BP)
Describe how blood pressure and blood osmotic pressure interact to create fluid in nutrient movement out of capillaries at the arteriolar end and fluid with the cellular waste back in the capillaries at the venule end
Arteriolar end :
blood pressure out > blood osmotic pressure in = net filtration pressure
Venule end:
Blood pressure out < blood osmotic pressure in = net reabsorption pressure
At the arterial end, what is the blood pressure and osmotic pressure? Venule end?
Arterial end:
- osmotic pressure = 21 mmhg
- blood pressure = 30 mmhg
Venule end:
- osmotic pressure = 21mmhg
- blood pressure = 15mmhg
Laminar flow
No sound
Turbulent flow
Sound
Why must cellular waste be moved back into capillaries?
Prevents waste build up
