Exam 4 Flashcards
Basal metabolism of the heart consumes what percent of oxygen used by the heart?
25%
What does basal metabolic activity refer to?
Maintain active transport mechanisms at rest
Muscle contraction consumes what percent of the oxygen used by the heart?
75%
Pressure Work
99% of total work
External work; works ot move blood from low pressure to high pressure
Stroke Work
1% of total work of heart (up to 50% heart failure)
Work needed to accelerate blood to ejection velocity
Workload of R side of heart vs L side
R side has 1/6th work load of L side
External Work of the heart
Pressure Volume Work
Transferring blood to the arterial system against a resistance
Velocity Equation
Velocity = Flow/ Cross Sec. A
Minute Work Output
Total energy converted to work per minute
Stroke Work x HR
Potential Energy of the heart
additional work heart could do if it were able to contract and empty the ventricle
Stroke Work Output
Amount of energy converted to work by heart during each beat
Total Energy of the heart
Potential energy + Stroke Work Output
Equation for Efficiency of Work
Work Output/Total E used = Efficiency
What is the normal efficiency of cardiac contraction?
20 to 25%
Efficiency of cardiac contraction can go as low as _____to_____% with heart failure.
5 to 10 %
Max systolic pressure that a normal left ventricle can generate
250 to 300 mmHg
Max systolic pressure the right ventricle can generate
60 to 80 mmHg
Optimal filling volume for the right/left ventricle
120 to 170 mls
Normal end-systolic volume
50 mL
Normal end-systolic pressure
2-3 mmHg
Normal end-diastolic volume
120 mLs
Normal end-diastolic pressure
5 to 7 mmHg
Normal Stroke Volume
70mL
Equation for Cardiac Output
CO = HR x SV
What factors change SV?
Preload (Intrinsic contractility)
Afterload
Extrinsic Contractility
Changing 1 mmHg preload pressure results in how many mls change?
25 mls
Changing 1 mmHg afterload pressure results in how many mls change?
0.5 mL
Why does SV increase when contractility is increased (no change in afterload or preload)?
Each muscle fiber able to generate more tension at any given resting length
Why does end-systolic pressure decrease when contractility is increased?
Stroke volume increased, able to expel more blood
How to calculate changes in contractility on the graph?
Slope of the line = Change P/Change V
Substrate utilization for normal energy production by the normal adult heart
70-90% oxidative metabolism of fatty acids
10-30% lactate and glucose
Substrate utilization for normal energy production of the normal fetal heart
Derive most ATP from lactate and glucose
Substrate utilization for energy production by the adult heart suffering from heart failure
Most ATP derived from lactate and glucose
Calculating Stroke Work
Volume x Pressure
What does ATP used for muscle contraction encompass?
ATP associate with cross-bridge action
Sequestration of calcium; active mechanisms
What is the name of the protein that can bind with oxygen?
Myoglobin
Heart removes most of the oxygen from the blood- leaving venous sat to….
25%
What is the only way to increase oxygen supply to the herat?
Increase coronary blood flow
What percent oxygen does isovolumic contraction use?
50% off overall O2 use
Why is cardiac afterload a major determinant of overall oxygen use?
Related to tension development (more than pressure generation)
Law of LaPlace: Tension= P x R
Three Basic Principles of Circulatory Function
- Rate of BF to each tissue is precisely controlled by tissue need (arterioles, CNS, hormones)
- CO controlled by sum of local tissue flow (CNS)
- Arterial Pressure independent of local BF or CO (kidneys)
Shear Stress Equation
SS = 4nQ/ pi*r^3
Reynolds’ number values at which turbulence will begin to appear at a side branch
200 to 400
Reynold’s number at which turbulence will being to appear in a straight tube
2000
Blood is ___x more viscous than water.
3x
What are the functional parts of the circulation?
Systemic
Pulmonary
Which functional circulation has a constant internal environment?
Systemic Circulation
How much lymphatic flow circulates each day?
2.5 L/day
Peripheral veins
all veins outside the thorax; not affected by thoracic P
Central Veins
major veins within the thorax; affected by thoracic pressure; lowest pressure in vascular system. Determine ventricular filling (if no pulmonary problems)
Cross Sectional A of Aorta
4.5 cm^2
Cross Sectional A of Arteries
20 cm^2
Cross Sectional A of Arterioles
400 cm^2
Cross Sectional A of Capillaries
4500 cm^2
Cross Sectional A of Venules
4000 cm^2
Cross Sectional A of Veins
40 cm^2
Cross Sectional A of Vena Cava
18 cm^2
Blood volume in veins, venules, and venous sinuses
64%
Blood volume in arteries
13%
Blood volume in arterioles and capillaries
7%
Blood volume in heart
7%
Blood volume in lungs
9%
Blood volume in systemic circulation
84%
Flow velocity in arteries
500 mm/s
Flow velocity in capillaries
0.5 mm/s
Flow velocity in arterioles
decreasing
Flow velocity in venules and veins
increasing
Mean pressure in arteries
100 mmHg
Mean pressure in capillaries
25 mmHg
What factors affect MAP?
MAP = CO x TPR
Why do arterial systolic, mean, and diastolic pressure change as the patient ages?
Decreasing arterial distensibility and increased SVR; changes in pressure control mechanisms by decreasing arterial distensibility and increased SVR
What is MAP?
Pressure drop across the systemic system; assuming the CVP is 0 mmHg
As ________ goes up, MAP will be closer to systolic.
Heart rate
Why is MAP closer to diastolic pressure under normal circumstances?
Spend more time in diastole
Equation for distensibility
Distensibility =Change vol/ (change P x original volume)
Relative distensibilities of arteries and veins.
Veins are 8x more distensible than arteries
Relative distensibilities of the pulmonary and systemic arteries.
PA 6x more distensible than systemic
Relative distensibilities of the pulmonary and systemic veins.
PV and SV distensibilities are the same.
Two equations for compliance
Compliance= Change V/Change P Compliance= Distensibility x Initial Volume
Normal Compliance for systemic arteries
2 ml/ mmHg
Normal Compliance for systemic veins
100ml/ mmHg
Normal pressure pulse transmission velocity in the aorta
3 to 5 m/s
Normal pressure pulse transmission velocity in large arteries
7 to 10 m/s
Normal pressure pulse transmission velocity in small arteries
15-35 m/s
Pulse pressure equation
PP = SV/ arterial compliance
Systolic pressure equation
Ps= SV x HR x SVR x (2/3)(SV/Ca)
Diastolic pressure equation
Pd= SV x HR x SSR x (1/3)(SV/Ca)
Normal pressure difference between the peripheral veins and the central veins
4 to 6 mmHg
How much does intra-abdominal pressure rise during pregnancy, tumors, obesity….
15-30 mmHg
Standing absolutely still has what venous pressure in the feet
90mmHg
When standing still, how much circulating blood volume can be lost
10 to 20% in 15-30 minutes (pressure in capillaries increases)
Normal venous pressure in the feet of a standing person
20 mmHg
How much does the spleen hold?
100 mls
How much does the liver hold?
Several hundred mls
How much do abdominal veins hold?
300 mls
How much does the venous plexus hold?
Several hundred mls
How much does the heart hold?
50-100 mls
How much do the lungs hold?
100 to 200 mls
ANS activated by centers in
Spinal cord
Brain stem
Hypothalamus
Efferent fibers originate in spinal cord from ____ to ____
T1 to L2
Preganglionic transmission options from sympathetic chains
- Synapse directly with postganglionic fibers
- Follow preganglionic pathway to one of two peripheral ganglia where they synapse with postganglionic fibers
- Pass through sympathetic chains then through splanchnic nerves to the two adrenal medullae
____% of fibers in average skeletal nerve are sympathetic fibers
8%
Parasympathetic nervous system deals with which nerves
3, 7, 9 & 10
____% of the parasympathetic nerves are in the vague nerve (cranial nerve 10)
75%
Transmitter Vesicles store how many molecules of transmitter substance?
2,000 to 10,000 molecules
How big is the space between presynaptic terminal and postsynaptic membrane?
200 to 300 angstroms
Two types of ionophore channels
Cation channel (mainly sodium) Anion channel (mainly chloride)
Alpha component can stimulate four different actions
- Open specific ion channel through postsynaptic membrane- channel can remain open for long period of time
- Activation of cAMP or cGMP
- Activate enzymes
- Gene transcription
Cholinergic fibers
Fibers that release acetylcholine
Adrenergic fibers
Fibers that release norepinephrine
Parasympathetic transmitter
Acetylcholine
Sympathetic transmitter
Norepinephrine
Acetylcholine Production
Acetyl-CoA + Choline -> Acetylcholine
Requires: choline acetyltransferase
Acetylcholine Removal
Catalyzed by acetylcholinesterase into an acetate ion and choline
Choline transported back into terminal nerve ending to be used in production of more acetylcholine
Norepinephrine Production
Starts in axoplasm of terminal nerve ending
- Tyrosine –> Dopa via hydroxylation
- Dopa –> Dopamine via decarboxylation
- Dopamine into vesicles for final production
- Dopamine –> Norepinephrine via hydroxylation
In the medulla, ___% of the norepinephrine is converted to epinephrine via methylation process
80%
3 Mechanisms for Norepinephrine Removal
- 50-80% moved back into terminal nerve ending via active transport process
- Most of rest diffuses away from the nerve endings into surrounding tissue
- Small amt destroyed by monoamine oxidase (nerve endings) or catechol-O-methyltransferase (all tissues)
Norepinephrine and epinephrine released be adrenal medullae into blood remains active for ____ to _____seconds
10-30 seconds
Level of activity takes __ to ___ minutes to degenerate to nothing
1 to 3 minutes
Norepinpherine deactivated by __________, mainly in the liver
Catechol-O-methyl transferase
Two main types of cholinergic receptors
Muscarinic & Nicotinic
What is muscarinic receptor activated by?
Muscarine (Toad-stool poison); acetylcholine
What is the nicotinic receptor activated by?
Nicotine, acetylcholine
Two types of adrenergic receptors
Alpha (1 and 2), Beta (1, 2, and 3)
Norepinephrine is secreted where?
Adrenal Medullae (big effect on afterload)
Norepinephrine has main affect on what receptors?
Alpha Receptors (smaller affect on beta receptors)
Epinephrine is secreted by what?
Adrenal Medullae
____ frequency of stimulation required for full activation of effector receptors.
Low freq.
How many impulses per second will maintain normal sympathetic or parasympathetic effect?
1
How many impulses per second will produce full activation?
10 to 20 impulses per second
Sympathetic tone in systemic arterioles keep almost all sympathetic arterioles contricted to _____ their normal diameter.
1/2
Normal release of norepinephrine
0.05 ug/kg/min
Normal release of epinephrine is
0.2 ug/kg/min