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Anatomy II > AnatomyII-Test One part 3 > Flashcards

AnatomyII-Test One part 3 Flashcards

1
Q

Heart Cells

A

Some cardiac muscle cells are self-excitable (autorhythmic) and initiate the depolarization of the whole heart
All cardiac muscle cells contracts as a unit
Have a long (250 ms) absolute refractory period
Have more mitochondria than skeletal muscles
Non autorhythmic contract similar to skeletal muscles

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2
Q

Intrinsic Conduction System

A

Initiate the action potentials which cause the muscles of the heart to contract and pump blood
Network of noncontractile (autorhythmic) cells

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3
Q

Autorhythmicity

A

Heart depolarizes and contracts without nervous system stimulation (Intrinsic)
Autorhythmic Cells (pacemaker cells)
Unstable resting membrane potentials
pacemaker potentials or prepotentials
Continuously depolarize, never rest
Due to opening of slow Na+ channels
Use calcium influx (rather than sodium) for rising phase of the action potential

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4
Q

Heart is stimulated by the

A

sympathetic cardioacceleratory center

 rate and force

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5
Q

Heart is inhibited by the

A

parasympathetic cardioinhibitory center

 rate

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6
Q

Electrocardiogram

A

Recorded by electrodes placed at specific points on the skin

Electrical activity resulting from the propagation of many action potentials

Composite of all action potentials generated by nodal and contractile cells at given time

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7
Q

PWave

A

depolarization SA node  atria

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8
Q

QRS Complex

A

ventricular depolarization and atrial repolarization

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9
Q

TWave

A

ventricular repolarization

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10
Q

Why EKG

A

Valuable in diagnosing diseases or ailments that damage the conductive abilities of the heart muscle
Damaged cardiac muscle cells no longer conduct electrical impulses
Electrical signals terminate at the damaged tissue
Alters the manner in which the heart contracts
A patient’s electrocardiogram can help determine the presence of damaged cardiac muscle based on the waveform as well as the time interval between electrical events

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11
Q

Heart Sounds

A

Heart sounds (lub-dup) are associated with closing of heart valves
First sound occurs as AV valves close and signifies beginning of systole (contraction)
Second sound occurs when SL valves close at the beginning of ventricular diastole (relaxation)

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12
Q

Diastole

Systole

A

relaxation of heart muscle

contraction of heart muscle

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13
Q

Ventricular filling

A

mid-to-late diastole
Heart blood pressure is low as blood enters atria (passively) and flows into ventricles
AV valves are open, then atrial systole occurs

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14
Q

Ventricular systole (contraction)

A

Atria relax
Rising ventricular pressure results in closing of AV valves
Isovolumetric contraction phase
Ventricular ejection phase opens semilunar valves

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15
Q

Isovolumetric Relaxtion

A

early diastole
Ventricles relax
Backflow of blood in aorta and pulmonary trunk closes semilunar valves

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16
Q

Dicrotic Notch

A

brief rise in aortic pressure caused by backflow of blood rebounding off semilunar valves

17
Q

Cardiac Output

A

amount of blood pumped by each ventricle in one minute

18
Q

CO is the product of

A

heart rate (HR) and stroke volume (SV)

19
Q

HR

SV

A

the amount of blood pumped out by a ventricle with each beat

the number of heart beats per minute

20
Q

Cardiac Reserve

A

difference between resting and maximal CO

21
Q

EDV

ESV

A

amount of blood remaining in a ventricle after contraction

amount of blood collected in a ventricle during diastole

22
Q

Factors Affecting Stroke Volume

A

Preload
Contractility
Afterload

23
Q

Preload
Contractility
Afterload

A

amount ventricles are stretched by contained blood

cardiac cell contractile force due to factors other than EDV

back pressure exerted by blood in the large arteries leaving the heart

24
Q

Preload

A

or degree of stretch, of cardiac muscle cells before they contract is the critical factor controlling stroke volume
Most important factor stretching cardiac muscle is venous return – amount of blood returning to heart
Slow heartbeat and exercise increase venous return to the heart, increasing SV
Blood loss and extremely rapid heartbeat decrease SV

25
Q

Contractility

A

is the increase in contractile strength, independent of stretch and EDV

Increase in contractility comes from: 
Increased sympathetic stimulation
 increased Ca2+ influx  more cross bridges
Certain hormones
Ca2+ and some drugs
26
Q

Sympathetic stimulation

A

releases norepinephrine and initiates a cyclic AMP second-messenger system
Results in elevated intracellular [Ca2+] of pacemaker cells

27
Q

Agents/factors that decrease contractility include:

A

Acidosis
Increased extracellular K+
Calcium channel blockers

28
Q

Regulation of Heart Rate
Positive chronotropic
Negative chronotropic

A

factors decrease heart rate
Sedatives

factors increase heart rate
Caffeine

29
Q

Sympathetic nervous system activated by

A

emotional or physical stressors
Norepinephrine causes pacemaker to fire more rapidly (and increases contractility)
increase HR
increase contractility

30
Q

Parasympathetic nervous system opposes

A

sympathetic effects
Acetylcholine hyperpolarizes pacemaker cells by opening K+ channels
 HR

31
Q

Vagal Tone

A

Parasympathetic dominant influence

Heart at rest

32
Q

Atrial (Bainbridge) reflex

A

sympathetic reflex initiated by increased venous return, hence increased atrial filling
Stretch of atrial walls stimulates SAnode
 HR
Also stimulates atrial stretch receptors, activating sympathetic reflexes

33
Q

Hormones that increase heart rate

A

epinephrine and thyroxine

Intra- and extracellular ion concentrations must be maintained for normal heart function

34
Q

Hypocalcemia

Hypercalcemia

A

depresses heart

increased HR and contractility

35
Q

Hyperkalemia

Hypokalemia

A

alters electrical activity  heart block and cardiac arrest

feeble heartbeat; arrhythmias

36
Q

Other Factors that Influence Heart Rate

A

Age
Fetus has fastest HR

Gender
Females faster than males

Exercise
Increases HR

Body temperature
Increases with increased temperature

37
Q

Tachycardia

A

abnormally fast heart rate (>100beats/min)

38
Q

Bradycardia

A

heart rate slower than 60beats/min

Anatomy II (7 decks)

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