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EEOB Exam 11

Terms in this set (57)

Myocardium
middle layer of cardiac muscle fiber. Constitutes bulk of heart
Striated muscle fibers
parallel myosin and actin
Short and branched myofibers
individual cardiac muscle cells that are interconnected
Intercalated discs
junction between two myofibers. Two types: Desmosomes and Gap Junctions
Desmosomes
adhering junction that mechanically holds cells together. Abundant in tissues such as the heart that are subject to considerable mechanical stress
Gap Junctions
Opposing membranes approach each other closely to form these. Allows action potentials to spread from one cardiac cell to adjacent cells
Contraction
Ca2+ induced Ca2+ release

AP on PM into TT
Voltage gated Ca2+ channels lie within TT
Ca2+ diffuses into cytosol from ECF across the TT
Binds to troponin --> Cross bridge cycling
Induces a much larger influx of Ca2+ into the cytosol from SR
Relaxation
Isovolumic pressure drops
Ca2+ returns to the interstitial fluid from cytosol and SR via ATPase pumps
Sinoatrial node (SA)
right atrial wall near opening of superior vena cava. Initiates AP that spreads through both atria
Atrial cells
contract and transmit the APs from top to bottom of heart
Atrioventricular node (AV)
small bundle of cardiac muscle cells located at the base of the right atrium. Only point where an AP can spread from the atria to the ventricles
Bundles of His
originates at AV node and enters septum between ventricles. Divides to form left and right bundle branches.
Helps spread AP without contraction
Purkinje Fibers (PF)
fibers that extend from Bundle of His and spread throughout ventricular myocardium.
Ventricular cells contract and transmit AP from bottom to top
Electrocardiogram (EKG)
recording of overall spread of electrical activity throughout the heart
P wave
atrial depolarization.
SA node fires when atria are full of blood. Causes depolarization when AP fires
QRS complex
ventricular depolarization
atria repolarizing simultaneously but is obscured.
firing of AV node
T wave
ventricular repolarization. (absent of blood right before cycle starts again)
Lub
just post QRS. cuspids closing
Dub
just post T. seminars closing (aortic and pulmonic valves)
Heart murmur
backflow of blood due to failed closure
Blood pressure
force exerted by blood against a vessel wall. Depends on the volume of blood and compliance of walls.
Systole
The stage of the heart cycle in which the heart muscle contracts and the chambers pump blood.
Diastole
the phase of the heartbeat when the heart muscle relaxes and allows the chambers to fill with blood.
Stroke Volume
The amount of blood ejected from the heart in one contraction.
End diastolic volume (EDV)
how much blood is left in heart at the end of diastole. Max 135 mL
End systolic volume
The amount of blood in the ventricles after systole. Min about 65 mL
Heart Rate
A measure of cardiac activity usually expressed as the number of beats (strokes or cycles) per minute.
Cardiac output
The amount of blood ejected from the heart in one minute. Determined by SV x HR. Relatively independent
Heart rate regulation is _______________
autonomic
This can modify the strength and rate of contraction by acting on the SA node
decrease or increase in the rate of depolarization to threshold
Conduction velocity
The speed at which an action potential is propagated along the length of an axon. Availability of gap junctions. Less connexions, less availably to make gap junctions, less action potentials, lower heart rate.
Other impacts on heart rate
1) Epinephrine
2) Body Temp
3) Electrolytes
4) Endocrine System
Epinephrine
Flight or flight sympathetic, increase heart rate
Body Temp
P = nRT/V. Increases temp. Become pink = expel heat out. Decreases temp. Become pale = retain heat

Body temp increase = heart rate increase
Body temp decrease = heart rate decrease
Electrolytes (ions)
Ca2+, Na+, K+ = key for APs

Mg+ = effect Vm
Endocrine System
sex endocrines = testosterone and estrogen. Get heart rate up when there is an increase
Stroke Volume Regulation
increase in EDV.

Increase in contraction force when stretched a little (increase potential for CBC) so that myosin can connect to actin

Decrease force coming from ventricles when there is too much stretch (congestive heart failure) causes actin and myosin to separate.

Change in arterial pressure : pressure gradient creates resistance

Sympathetic NS: Norepinephrine and Epinephrine will increase contraction force regardless of EDV
All blood vessels are lined with _________________
endothelial cells
Arteries
Biggest of vessels

highly elastic

smooth muscle

increased hydrostatic pressure
Arterioles
Smaller

less elastic

smooth muscle

increased hydrostatic pressure
Capillaries
smallest : one RBC at a time

Want walls to be as thin as possible so that we can get RBC as close to other cells as possible for exchange of glucose and oxygen. Limits distance and makes diffusion easier

Increased surface area

To help with diffusion, we want things to move as slow as possible. One RBC at a time.

There's a decrease in hydrostatic pressure because the walls are so thin and we don't want them to break

As BP goes down away from our heart, so does hydrostatic pressure
Hydrostatic pressure depends on
surface area: the amount of space available for the blood to press on
Vein
carries deoxygenated blood to the heart

has valves that work against gravity to ensure blood is moving in the correct direction

sits between skeletal m. so that when skeletal m. contracts, it forces blood up towards the heart

low hydrostatic pressure but still greater than in capillaries. lower surface area. base BP is lower
Arterial BP
blood pressure found in the arteries.

determined by PV=nRT

Mirrors cardiac cycle in terms of systolic/diastolic
Arterial BP- Systolic
Squeezing/Contraction.

Contractions end = max

Top number

smallest volume = biggest pressure
Arterial BP - Diastolic
Relaxation

Before contraction = min

Bottom number

biggest volume/smallest pressure
In terms of PV=nRT, when we change n we are changing
the amount of blood within a vessel
In terms of PV=nRT, what determine our volume
how rigid the vessel wall is
n has a ____________ relationship with pressure
direct - the amount of blood within a vessel influences the pressure within the vessel
v has an ___________ relationship with pressure
inverse - the more pressure that's applied, the less volume
Arteriolar BP
blood pressure within the arteriolar

each area of the body can have a different pressure

Arterioles regulate flow to specific tissues/organs in the body.
Local factors influencing arteriolar BP
active hyperemia
flow autoregulation
Active hyperemia
increasing flow to an area due to an increase in metabolic activity.

greater flow in one area = lesser flow in another
Flow autoregulation
vital organs such as the heart and brain need to have constant arteriolar flow. Independent of active hyperemia.
Arteriolar BP Extrinsic control factors
Vasodilation
Vasoconstriction
Vasodilation
arteriolar size increases = less force = lower BP

Nitric oxide decreases dilation
Vasoconstriction
arteriolar size decreases = more force = higher BP

Vasopressin does contstriction
Angiotensin increases tension on vessels
Norepi does constriction
Epi constricts only in cardiac and smooth but not in skeletal
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