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Physiology Block I
Cardiovascular System
238
Physiology
Post-Graduate
02/08/2014

Additional Physiology Flashcards

 


 

Cards

Term
What percent of the TBW is extracellular fluid (ECF) and intracellular fluid (ICF)?
Definition

ECF: 33%

 

ICF: 67%

Term
What is hematocrit?
Definition
Percentage of blood volume made up of cells
Term
How do you calculate Total Blood Volume (TBV)?
Definition
TBV= Plasma Volume x 100 / (100-hematocrit)
Term
How do you calculate volume of distribution?
Definition
Volume = amount of tracer / concentration of tracer
Term
For what particles does simple diffusion work for?
Definition
Small (<200MW) and uncharged
Term
Why does facilitated diffusion require no energy?
Definition
It only transports particles down their concentration gradient
Term
Why is water transfer via aquaporins faster than osmosis?
Definition
Aquaporins are facilitated diffusion, which is faster than simple diffusion.
Term
Why does active transport require energy?
Definition
You transport against the concentration gradient.
Term
What is the action of Na+/K+ ATPase?
Definition
3 Na+ out of the cytosol and 2 K+ into the cytosol
Term
What is the critical task that the Na/K ATPase performs in terms of osmolarity?
Definition
It reduces the number of osmotic particles inside the cell so that it does not swell and burst.
Term
How do secondary active transporters get their energy?
Definition
They use the electrochemical gradient set up by another transporter.
Term
What is a cotransport (symport) vs. a countertransport (antiport/exchange)?
Definition

Cotransport have both solutes moving in the same direction.

 

Countertransport has the solutes moving in opposite directions.

Term
What causes osmotic pressure?
Definition
When two compartments separated by a semipermiable membrane have different concentrations of impermeable solutes.
Term
When do behaviors of fluids in solution become more ideal?
Definition
When they become closer to dilute
Term
What is the major player in determining osmalarity in extracellular fluid?
Definition
Na+
Term
What is the normal osmolarity in body fluids?
Definition
290 mOsm/L
Term
What is tonicity?
Definition
Tendancy of an external solution to resist expansion
Term
What is an isotonic solution?
Definition

145mM NaCl (290mOsm/L).

No change in RBC volume

Term
What is a hypertonic solution?
Definition

300 mM NaCl (600 mOsm/L)

Water comes out of the RBC by osmosis into plasma, shrinking it.

Term
What is a hypotonic solution?
Definition

50mM NaCl (100 mOsm/L)

RBC swells because water leaves plasma and enters the cell, leading to hemolysis when plasma is <200mOsm/L

Term
When does hypernatremia/dehydration occur?
Definition

Na+ concentration in serum is >146 mM.

Electrolyte imbalance due to lack of free water.

Term
When does hypoatremia occur?
Definition

When serum Na+ is below 135 Na+ mmol/L

Life-threatening at 120 mmol/L

Term
What are the subunits of myosin-II?
Definition

6 subunits:

 

one pair heavy, 2 pairs of light chains.

Term
What is the function of Titin?
Definition
It's the molecular spring that keeps the thick filament centered
Term
What are the parts of the thin filament?
Definition
Actin, tropomyosin, troponin
Term
What subunit of troponin binds to Ca?
Definition
C subunit
Term
How many thin filaments surround a thick filament?
Definition
6
Term
Where does actin bind on myosin (thick filament)?
Definition
On the globular heads.
Term
Where does Calcium come from in muscles?
Definition
The sarcosmic reticulum, especially near the terminal cistern near the T system
Term
What pumps the Calcium into the SR at a high rate?
Definition
SERCA, active transporter of Ca-ATPase
Term
What helps sequester the Calcium in the terminal cisterns of the SR?
Definition
Calsequestrin
Term
How many Ca are pumped into the SR by SERCA per ATP?
Definition
2
Term
What causes the relaxation of a muscle fiber?
Definition
SERCA pumping of a into the SR (ATP-dependent process)
Term
What is an isometric contraction?
Definition

"Same length"

Generates force with constant muscle length

Term
What is an isotonic contraction?
Definition

"same tension"

length decreases as the muscle shortens, force remains constant.

Term
What type of contraction can do work?
Definition
Isotonic contraction
Term
What is a twitch?
Definition
A single contraction caused by a single AP
Term
What is tetanus?
Definition
Muscle contraction has APs with frequency high enough to produce continuous maximal contraction in muscle
Term
What is Active Tension?
Definition
Total tension minus Passive Tension
Term
Where is active tension maximal?
Definition
Where there is a max overlap of thick and thin filaments allowing the most cross-bridges to form.
Term
What are Type I muscle fibers?
Definition
Slow twitch (Red Muscles)
Term
What are type II muscle fibers?
Definition
Fast twitch muscles (white muscles)
Term
How to single-unit smooth muscles function?
Definition
They funciton as a syncytium - muscle fibers electrically connected to each other via gap junctions.
Term
What is myogenic activity?
Definition
When single-unit smooth muscle produce phasic contractions.
Term
How do type II smooth muscles initiate contraction?
Definition
Neurotransmitter release (neurogenic not syncytial)
Term
What innervates a multiunit subunit?
Definition
En passant bouton
Term
Where does the calcium for contraction come from for smooth muscle?
Definition
ECF or increased IP3
Term
Where does Ca bind to in smooth muscle?
Definition
Calmodulin to phosphorylate myosin
Term
What allows persistant partial contraction of smooth muscle (tonus)?
Definition
Latch bridge
Term
What is the purpose of Alpha-1 adrenergic recptor activation and what activates it?
Definition

NE

 

It increases IP3 and Ca to increase muscle contraction/BP

Term
What is the purpose of Beta-2 adrenergic recptor activation and what activates it?
Definition

Epinephrine

 

Increases cAMP to relax muscle and decrease peristalsis/BP

Term
What causes the steady influx of Ca and Na in pacemaker cells?
Definition
If channels
Term
What channel do pacemaker cells lack that ventricular cells do have?
Definition
K1 Potassium channels
Term
What channels do ventricular cells possess that are not in SA nodal cells?
Definition

 

Fast voltage-dependent Na channels that opens with depolarizations


Potassium channel called the K1 potassium channel that is open at voltages between -90 mV and -50 mV.  

Term
At what rate do SA nodal cells fire without modulation?
Definition
100-120 beats/min
Term
At what rate do AV nodal cells fire without modulation?
Definition
80-100 beats/min
Term
At what rate do Bundle of His cells fire without modulation?
Definition
30-50 beats/min
Term
What type of blockage is marked by a >0.18 sec (180 msec) delay between atrial and ventricular depolarization?
Definition
First Degree blockage.
Term
What is it called when every other P wave is followed by a QRS complex?
Definition
2:1 Second degree blockage
Term
What type of blockage is determined by an AV node being incapable of conducting impulses?
Definition
Third degree blockage
Term
How much stronger is the Left Ventricle pump vs the Right Ventricle?
Definition
5 times stronger due to resistance
Term
How are the systemic and pulmonary circuits arranged vs the vascular beds?
Definition

Systemic/Pulmonary: Series

 

Vascular beds: Parallel

Term
What is the relationship of velocity, CSA, and flow?
Definition
Flow = Velocity x CSA
Term
What is cardiac output?
Definition
CO = Stroke Volume x HR
Term
Where is the most time spent by blood in the vascular cycle?
Definition
Large veins
Term
Where does the biggest drop in pressure occur in the circulatory system?
Definition
Between the small arteries and the arterioles
Term
How does the mean pressure vs maximal puslatile pressure change across the circulatory tree?
Definition
The mean pressure always decreases, but the maximal pulsatile presure can actually be higher past the aorta.
Term
Where is most of the blood found in the circulatory tree?
Definition
On the venous side under low pressure.
Term
How do the artery and vein paths of the circulatory tree differ in terms of pressure and volume storage?
Definition

Aorta/large arteries: Pressure storage

 

Veins: Volume storage

Term
What is compliance?
Definition
The ratio between change in volume and change in pressure
Term
How do you measure Cardiac Output in terms of pressure and resistancef?
Definition
CO = MAP/TPR
Term
How will raising pressure on the left side of the circulatory system affect blood flow?
Definition
Raising the diastolic pressure will diminish the driving pressure through the pulmonary circuit leading to lung edema
Term
How does the resistance of a vessel relate to the radius of the vessel?
Definition
R=1/r^4
Term
How does flow rate of a vessel relate to it's radius?
Definition
Q=r^4
Term
What is critical closing pressure?
Definition
If driving pressure drops 20-25 mmHg, blood flow stops completely because the intrinsic sympathetic tone causes the small vessels to close.
Term
How does constriction/dilation affect critical closing pressure?
Definition

Constriction: Increases CCP

 

Dilation: Decreases CCP

Term
How does increased hematocrit affect viscosity?
Definition
Increases it
Term
How does a radius <200um affect viscosity?
Definition
It results in fluidization of RBC and streamlined flow
Term
How does velocity affect viscosity?
Definition
At slow speeds viscosity increases
Term
Where does blood flow fastest in a vessel?
Definition
Center
Term
When does turbulent flow occur in straight vs braches of vessels?
Definition

Branches: Re > 1000

 

Straight: Re > 2000

Term
Why does Re increase during constriction of a vessel?
Definition
The velocity of a vessel that's half the size will have a velocity 4 times greater, so Re is two times larger (turbulence more likely)
Term
How does radius affect wall size of a vessel?
Definition
A small radius requires a thin wall to maintain pressure, while a large radius requires a thicker wall to maintain pressure
Term
What is the average length of a small artery?
Definition
10 cm
Term
How do the walls of the right and left ventricles and the sizes of the ventricles compare in the heart?
Definition

Walls: Left ventricle 3 xs thicker than right

 

Size: Equal

Term
What type of motion do myocytes enact?
Definition
Oblique/Circumferential motions
Term
What causes the differences in pressure between the Left and Right ventricles of the heart?
Definition

The different wall thicknesses and radii 

 

Left is 3xs thicker, 2xs larger radius = 120 mmHg

Right is 3xs thinner, 2xs smaller radius = 20 mmHg

Term
How does contraciton of cardiomyocytes affect the heart?
Definition
It increases wall tension, τ
Term
How does concentric hypertrophy affect the heart (thickened walls)?
Definition
More pressure can be generated, but volume inside the ventricle decreases => decrease in stroke volume
Term
How does Dilated/eccentric hypertrophy affect the heart (radius increase)?
Definition

Thickness decreases of the wall => pressure decreases.

 

More blood can be accomadated, but enough pressure can't be generated.

Term
What happens to the excitation wave if the AV node pathway is blocked?
Definition
The wave will not propagate
Term
What are the low pressure and high pressure valves?
Definition

Low pressure: AV Valves

 

High Pressure: Semilunar Valves

Term
What causes the influx of extracellular Calcium during long cardiac contractions?
Definition
Dihydropyridine receptors (L-type Ca receptors)
Term
How can you increase the uptake of Ca into the SR?
Definition
Beta-adrenergic agonists (phosphorylates phospholamban)
Term
What are the preload and afterload for the heart?
Definition

Preload: End diastolic volume

 

Afterload: Aortic pressure

Term
What is the total force generated in contraction?
Definition
Sum of active fores generated by contractile elements plus the passive force due to extension of muscle elastic elements.
Term
How does stretch relate to force in the heart?
Definition
The greater the stretch, the more forceful the contraction
Term
What is the resting length of cardiac muscle sarcomeres?
Definition
70% optimum length required for force generation
Term
What is inotropy?
Definition
Influence of agents that alter contractility
Term
What are positive inotropes?
Definition
Increase contractility (noradrenaline, digitoxin)
Term
What are negative inotropes?
Definition
Decrease contractility (acetylcholine, Ca Channel blockers)
Term
How do cardiac glycosides affect the heart?
Definition
They inhibit the Na-K pump causing increased cytosolic Na, and increased Ca to improve contractility through SR load increase.
Term
How are cardiomyocytes connected to each other?
Definition
Gap Junctions
Term
What is contractility a measurement of?
Definition
The amount of Ca available in the cytosol
Term
How does excitation-contraction of skeletal muscle differ from cardiac muscle?
Definition
It does not require an influx of extracellular Ca
Term
How much tension does the cardiac muscle develop in order to double the systolic pressure within the ventricle?
Definition
Increase twice
Term
What are the steps in atrial contraction?
Definition

Atrial contraction

Isovolumetric ventricular contraction

Ventricular ejection

Isovolumetric ventricle relaxation

Ventricular filling

Term
What is the End Diastolic Volume?
Definition
Total blood contained in each ventricle.
Term
What is a healthy EDV?
Definition
130 mL
Term
What causes the first heart sound?
Definition
Closure of the AV valve
Term
What valves are opened for ventricular ejection?
Definition
Semilunar valves
Term
What causes the second heart sound?
Definition
Sharp closure of the semilunar valve
Term
What is the normal stroke volume at rest?
Definition
70-90 mL
Term
What is normal ESV?
Definition
≈50 mL
Term
What are systolic and diastolic pressures?
Definition

Systolic: Peal pressure reached during systole

 

Diastolic: Lowest pressure during diastole

Term
What is systole?
Definition
Period during which the ventricle is contracting
Term
How does shortening of diastole affect the heart at high rates?
Definition
It causes CO to decrease
Term
What is diastole?
Definition
Period of ventricular relaxation
Term
How do you find systole?
Definition
It's the period between closure AV valve closes to the closure of the semilunar valve
Term
What is overall heart rate shortening due to - systole or diastole?
Definition
Diastolic shortening
Term
What creates the a-wave?
Definition
Atrial contraction.
Term
What creates the c-wave?
Definition
Reflection of backward AV valve bending during isovolumetric ventricular contraction and impact of adjacent arteries with sudden increase in pressure from aortic valve opening
Term
What is the v-wave?
Definition
Association of slow rise in pressure as the atria and great veins fill.
Term
What will an incompetence in the tricuspid valve cause?
Definition
Regurgitation of blood through the valve during systole that would have an abnormal increase between c and v waves during rapid ejection.
Term
How do you calculate MAP?
Definition
MAP= 1/3 SP + 2/3 DP
Term
What is pulse pressure?
Definition
PP= SP-DP
Term
When is the greatest change in volume in the heart?
Definition
During rapid ventricular ejection and rapid filling
Term
When is the least change in volume in the heart?
Definition
Isovolumetric ventricular contraction/relaxation (no change)
Term
What is the ejection fraction (EF)?
Definition
EF = (EDV-ESV)/EDV
Term
How do right and left ventricular SV compare?
Definition
THEY'RE THE SAME MORON
Term
What are the heart sounds caused by?
Definition
The closure of the valves resulting in vibration of the valves, the heart, and the large arteries near them.
Term
When is a third heart sound normal to be found?
Definition
Young people
Term
What causes a fourth heart sound to be heard?
Definition
Stiff ventricles
Term
What causes a splitting of the second heart sound?
Definition
The semilunar valves close with a delay of each other (pulmonary valve closes slightly later than aortic)
Term
What causes an accentuation of splitting (physiological splitting)?
Definition
Deep inspiration so that pulmonary valve closure is further delayed by larger blood amount being ejected.
Term
What causes pathological splitting?
Definition

A diseased left ventricle causes contraction to be less vigorous so the aortic valve closes after the pulmonary.

 

Inspiration leads to lessened splitting.

Term
What are the effects of valve stenosis?
Definition
Orifice of the valve is narrowed so that the velocity increases and flow is turbulent.
Term
What is valve incompetence and what are the effects?
Definition
Incomplete closure of the valve causes a leaky valve.
Term
When are soft systolic murmors common?
Definition
Children and anemic patients due to low viscosity.
Term
What are the P, QRS Complex, and T waves representative on the ECG?
Definition

P wave: depolarization of atria and initiates atrial contraction.

 

QRS Complex: Depolarization of ventricle and precedes ventricle contraction.

 

T wave: precedes ventricular contraction.

Term
What is the end-systolic pressure-volume relationship (ESPVR)?
Definition

The max pressure that can be developed by the ventricle at any given left ventricular volume.

 

Defines the max pressure generated at any given inotropic state.

Term
What does the width of a pressure-volume loop show?
Definition
Stroke Volume
Term
What does the height of a pressure-volume loop show?
Definition
Systolic pressure
Term
What is the preload on the pressure-volume loop?
Definition
Volume at which the mitral valve closes
Term
What is the afterload on the pressure-volume loop?
Definition
Pressure at which the aortic valve opens
Term
How does the External/Internal work ratio compare to cardiac performance?
Definition
The larger the ratio, the better the performance.
Term
How is pumping effected if cardiac muscle compliance decreases?
Definition
Less effective pumping
Term
How is pumping effected if cardiac muscle contractility increases?
Definition
More effective pump
Term
How is pumping effected if aortic pressure increases?
Definition
Less effective pumping
Term
How is pumping effected if venous pressure increases?
Definition
More effective pumping
Term
End diastolic volume increases causes what?
Definition
SV increase
Term
If diastolic pressure is 90 and systolic pressure is 135, what will your MAP be?
Definition
105 mmHg
Term
How does CO in women compare to men?
Definition
Women have a 10% less CO
Term
How many L/min and mL/sec of blood are pumped?
Definition

5-6L/min

 

100mL/sec

Term
What are the long-term CO factors?
Definition

Ventricular geometry

Ventricular compliance

Electrical Coordination of contraction

Term
What are the short-term CO factors?
Definition

Preload

Afterload

Contractility

HR

Term
What is pulse pressure?
Definition
PP = SV/Aortic Compliance
Term
What happens to pulse pressure when arteries are less compliant?
Definition
It increases
Term
How does inhalation affect intrathoracic pressure, RA pressure, Pressure difference, and venous return?
Definition

intrathoracic pressure = decreases

RA pressure = decreases

Pressure difference = increases

venous return = increases

Term
What is the Mean Systemic Filling Pressure (MSFP)?
Definition
Pressure values after circulation has been stopped and pressure has equalized between arteries, capillaries, veins, and cardiac chambers.
Term
How will a 1L infusion of saline affect your MSFP?
Definition
Increases
Term
How will decreasing the compliance of veins affect the MSFP?
Definition
This makes the veins "less flacid," so that the circuits are more "full" and the MSFP increases
Term
How does gravity affect "gauge" pressure above and below the heart?
Definition

Above the heart: subtracts gauge pressure

 

Below the heart: adds gauge pressure

Term
What happens to a vessel if pressure is negative inside the flexible vessel and positive outside of it?
Definition
The vessel collapses
Term
What will happen to a vessel if the pressure is negative inside and the integrity of the vessel is damaged?
Definition
An air embolism will occur
Term
How does mean system filling pressure compare to mean arterial pressure and venous pressure?
Definition

Always:

 

Lower than MAP

Higher than Venous Pressure

Term
How is MAP calculated with an elevated HR?
Definition
MAP = 1/2 DP + 1/2 SP
Term
What is the value of the mean circulatory filling pressure and how does saline addition affect it?
Definition

7 mmHg

 

It increases it since it's more "full."

Term
What is the difference between contraction, contractility, and contractile?
Definition

Contraction: shortening and creating force

 

Contractility: Cardiac muscles contracting depending on Ca

 

Contractile: Protein/fiber/etc ability to contract

Term
How will Increased Blood volume affect CO and Venous pressure?
Definition
Higher CO and VP
Term
How will an increase in heart contractility affect CO and VP?
Definition
CO increases, CVP decreases
Term
How will a hemorrhage affect CO and VR?
Definition
Vascular volume significantly decreases so CO and VR drop
Term
How does adipose accumulation affect CO and BV?
Definition
Linearly increases BV and CO
Term
How does hypertention affect obese people?
Definition
It's a double burden - increase in afterload and preload
Term
What ventricle is thicker in fetuses and newly borns?
Definition
Right ventricle wall because it has been working harder in the womb.
Term
What is autoregulation?
Definition
Maintenance of constant blood flow to an organ despite changes in pressure gradient across the organ bed.
Term
What are the major determinants of coronary blood flow?
Definition

1. Perfusion Pressure

2. Myocardial Extravascular Compression

3. Local Myocardial Metabolism

4. Neurohormonal Influenecs

Term
What is reactive hyperemia?
Definition
Increase in blood flow in response to prior decrease in blood flow
Term
How do you calculate Cerebral Perfusion Pressure (CPP)?
Definition
CPP = MAP - ICP (Intracranial Pressure)
Term
What are the most common vasodilator signals in the cerebral circulation?
Definition

CO2 and pH

 

(increased CO2 and H+ causes cerebral vasodilation and increased blood flow)

Term
How does low O2 concentrations affect the lungs?
Definition
It causes pulmonary vasoconstriction
Term
What does a reflection coefficient of 0 and 1 mean?
Definition

0: freely permeable to the barrier

 

1: barrier is impermeable to the substance

Term
What is the typical oncotic pressure of blood?
Definition
28mmHg
Term
What is oncotic pressure?
Definition
Pressure created by proteins in the blood plasma that tends to pull water into the circulatory system.
Term
What pressure opposes oncotic pressure?
Definition
Hydrostatic pressure
Term
What are the typical hydrostatic pressure at the arterial and venous ends of the capillaries?
Definition

Arterial end: 30 mmHg

 

Venous end: 15mmHg

Term
What is the oncotic pressure and the hydrostatic pressure of the interstitial fluid?
Definition

Oncotic: 3-6 mmHg

 

Hydrostatic: -1 and -5 mmHg

Term
What pressure drives fluid movement of the blood?
Definition
Starling Pressure
Term
How do lymphatic vessels differ from blood capillaries?
Definition
They lack tight juncitons between endothelial cells and are permeable to proteins
Term
How do you determine the net movement of blood?
Definition

Hydrostatic pressure (P) - Oncotic pressure (Π) 

 

If positive = net movement OUT capillary

If negative = net movement IN capillary

Term
What happens if Hydrostatic pressure is greater than oncotic pressure?
Definition
Filtration (movement OUT)
Term
What happens if Hydrostatic pressure is less than Oncotic pressure?
Definition
Absorption (movement IN)
Term
What will increased capillary hydrostatic pressure cause?
Definition
Increased filtration in the arteries
Term
What will increased Venous Hydrostatic Pressure cause?
Definition
Increased venous filtration (since absorption won't occur in the venous system and pressure won't drop as much across)
Term
How will blocked lymph affect filtration and absorption?
Definition
Intersitial Oncotic pressure would increase, thus the overall oncotic pressure drops and filtration will increase
Term
How will a decrease in plasma protein affect filtration and absorption rates?
Definition
Overall oncotic pressure will decrease since capillary oncotic pressure drops, thus overall filtration increases.
Term
How will a increase in plasma protein affect filtration and absorption rates?
Definition
Overall oncotic pressure will increase since capillary oncotic pressure increases, thus causing absorption to increase.
Term
What NT is released by preganglionic sympathetic and parasympathetic neurons?
Definition
Ach
Term
What receptors are on postganglionic sympathetic and parasympathetic neurons?
Definition
Nicotonic receptors
Term
What is the primary NT released by postganglionic sympathetic neurons?
Definition
Norepinephrine (but not always)
Term
What is the NT released by postganglionic parasympathetic neurons?
Definition
Ach
Term
What is the effector organ receptor sympathetic neurons?
Definition
alpha or beta (but not always) receptors
Term
What is the effector organ receptor parasympathetic neurons?
Definition
muscarinic receptors
Term
What blocks postsynaptic nicotinic receptors?
Definition
hexamethonium
Term
What blocks muscarinic receptors?
Definition
atropine
Term
Where are α1 receptors present?
Definition
Postsynaptic sites in smooth muscle innervated by adrenergic sympathetic nerves
Term
Where are β1 receptors present?
Definition
postsynaptic sites of some adrenergic nerves like the heart.
Term
What usually stimulates β2 cells?
Definition
Circulating epinephrine
Term
What will stimulating β1 receptors of the heart cause?
Definition
Increased HR and contractility
Term
What will β2 receptor stimulation cause?
Definition
relaxation of bronchioles, and vasodilation in arterioles with β2 receptors (like skeletal muscle arterioles)
Term
What will a cholinergic activation of the heart cause?
Definition
Decreased HR via cholinergic muscarinic receptors
Term
What will Adrenergic activation of the heart cause?
Definition
Increased HR and contractility due to norepinephrine release from sympathetic fibers activating β1 receptors
Term
What will cholinergic activation of blood vessels cause?
Definition
Little, if any, endogenous parasymp innervation of blood vessels
Term
What will adrenergic activation of the blood vessels cause?
Definition

Constriction via symp activating α1 receptors

Dilation via circulating epinephrine activating β2 in arterioles with β2 receptors.

Term
What will cholinergic activation of the lung bronchiole system cause?
Definition
Contraction
Term
What will adrenerigic activation of lung bronchiole muscles cause?
Definition
Relaxation, β2
Term
What will adrenergic activation of sweat glands cause?
Definition
Secretion (Ach but sympathetic)
Term
What type of system dominates heart rate control?
Definition
Cardioinhibitory parasympathetic control
Term
How do parasympathetic neurons influence SA cells?
Definition
They release Ach that activates muscarinic cholinergic recptors to activate potassium channels and decrease rate of depolarization.
Term
Without the normal cardio-inhibitory parasympathetic activity, what would be your HR?
Definition
100-120 bpm (following SA node cells)
Term
Aside from decreasing rate of depolarization, how else does parasympathetic activity influence the heart?
Definition

Decreases conduction velocity between cells

Decreases excitability of latent pacemakers 

Term
How does norepinephrine affect SA node cells?
Definition

β1 adrenergic receptors are activated causes influx of Na and Ca through the If Channel

 

(increases depolarization rate -> increased HR)

Term
How does sympathetic stimulation affect SA Node Cells?
Definition

Decreases the threshold for Ca Channels -> increased excitability

(HR increases)

 

β1 adrenergic receptors increases depolarizatation rate (HR increases)

and increases Ca flow through voltage gated Ca channels

Term
How does parasympathetic stimulation affect SA Node Cells?
Definition
Ach released to muscarinic cholinergic receptors that activate potassium channels to hyperpolarize the cell and decrease rate of depolarization
Term
What will an increase in parasympathetic activity cause?
Definition
A stop of the HR for as long as 4 seconds.
Term
What will applying atropine do to the heart?
Definition

Muscarininc blocker:  Raises the HR to 100-120 bpm.

 

Mimics a lack of parasympathetic inhibition.

Term
What will applying propanolol to the heart cause?
Definition

Blocks β1 receptors: slows the HR and decreases cardiac contractility and excitability.

 

Mimics a loss of sympathetic activity

Term
What nerve fibers densely innervate smooth muscle cells in arterioles?
Definition
Postganglionic Sympathetic Fibers that release Ach
Term
What will a decrease in sympathetic activity in the arterioles cause?
Definition
Vasodilation
Term
What is respiratory sinus arrhythmia (RSA)?
Definition
The heart beats more rapidly during inspiration and more slowly during post-inspiration
Term
What is the main cause of respiratory sinus arrhythmia (RSA)?
Definition
Inhibition of parasympathetic preganglionic cardiac neurons during inspiration
Term
How does the Valsalva Maneuver affect the heart?
Definition

Decreases CO and BP

Decrease in baroreceptor discharge

Sympathetic increases, Parasympathetic decreases

HR and contractility increase

Term
How does the standing from supine position affect the heart?
Definition

Decreases baroreceptor discharge and parasympathetic.

 

HR and contractility increases and so does vasoconstriction due to sympathetic activity.

Term
How does horrhagic and septic shock affect the heart?
Definition
Bradycardia and vascular resistance decrease causing BP to drop
Term
How does the diving reflex affect cardiac function?
Definition
Bradycardia and increased parasympathetic activity
Term
How does hypertension affect barorecptors?
Definition
They cause resetting due to accomodation.
Term
What causes the Cushing reflex and how does it affect the heart?
Definition

Low levels of cerebral blood flow.

 

Causes dramatic increase in sympathetic heart and arteriole activity to increase arterial pressure.

Term
What are the purposes of the baroreflexes from sustained exercise?
Definition
Restore lowered BP, HR/contractility are increased, CO increases
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