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KPE 260 Human physiology > Cardiac L 14 > Flashcards

Cardiac L 14 Flashcards

1
Q

cardiac muscle is regulated by the

A

autonomic nervous system

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2
Q

is cardiac muscle striated or non striated

A

striated

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3
Q

Myosin and actin filaments form

A

sarcomeres

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4
Q

Contraction occurs by means of sliding

A

thin filaments

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5
Q

cardiac muscle is connected via

A

via gap
junctions called intercalated discs (electrical
synapses that permit impulses to be
conducted cell to cell).

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6
Q

is cardiac muscle multinucleated?

A

NO

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7
Q

define myocardium

A

a mass of cardiac muscle cells connected to
each other via gap junctions.

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8
Q

do action potentials have to occur at all cells in myocardium to simulate ALL the cells in myocardium?

A

no, Action potentials that occur at any cell in a myocardium can
stimulate all the cells in the myocardium
-behaves as single functional unit

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9
Q

what is pacemaker potential?

A

Cardiac muscle producing action potentials automatically
(without innervation)

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10
Q

what is heart rate influenced by?

A

autonomic innervation and
hormones.

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11
Q

are voltage-gated calcium
channels directly connected to calcium
channels in the SR?

A

NO,
instead:calcium acts as a second messenger to open
SR channels: called calcium induced calcium release

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12
Q

what is cardiac output?

A

Cardiac output – the volume of blood
pumped each minute by each ventricle:
cardiac output = stroke volume X heart rate
(ml/minute) (ml/beat) (beats/min)
a. Average heart rate = 70 bpm
b. Average stroke volume = 70 to 80 ml/beat
c. Average cardiac output = 5,000-5,500 ml/minute

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13
Q

how is cardiac rate regulated?

A

Spontaneous depolarization occurs at SA node
when HCN channels open, allowing Na+ in.

a. Open due to hyperpolarization at the end of the
preceding action potential

b. Sympathetic norepinephrine and adrenal
epinephrine keep HCN channels open, increasing
heart rate.

c. Parasympathetic acetylcholine opens K+ channels,
slowing heart rate.

d. Controlled by cardiac center of medulla oblongata
that is affected by higher brain centers

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14
Q

what antagonistic influence increases cardiac rate?

A

Positive chronotropic effect
Tachycardia >100 bpm

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15
Q

what antagonistic influence decreases cardiac rate?

A

Negative chronotropic effect
Bradycardia < 60 bpm

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16
Q

what are the sympathetic and parasympathetic effects of the SA node?

A

sympathetic:Increased rate of diastolic
depolarization; increased
cardiac rate

parasym:Decreased rate of diastolic
depolarization; decreased
cardiac rate

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17
Q

what are the sympathetic and parasympathetic effects of the AV node?

A

sym:Increased conduction rate
para:Decreased conduction
rate

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18
Q

what are the sympathetic and parasympathetic effects of the atrial muscle?

A

sym: Increased strength of
contraction

para:No significant effect

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19
Q

what are the sympathetic and parasympathetic effects of the ventricular muscle?

A

sym: Increased strength of
contraction

para: No significant effect

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20
Q

what 3 variables is stroke volume regulated by?

A
  1. End diastolic volume (EDV): volume of blood in the
    ventricles at the end of diastole
    a) Sometimes called preload
    b) SV increases with increased EDV.
  2. Total peripheral resistance: Frictional resistance in
    the arteries
    a) Called afterload
    b) Inversely related to SV
  3. Contractility: strength of ventricular contraction
    a) SV increases with increased contractility.
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21
Q

normally, about how much % of the end diastolic volume (EDV) is ejected?

A

60%,
aka the ejection fraction: amount of blood pumped out of the ventricle/total amount of blood in ventricle

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22
Q

what is the frank starling law?

A

increased end diastolic volume (EDV) results in increased contractility and thus increased stroke volume

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23
Q

what is Intrinsic Control of Contraction Strength due to?

A

1) Due to myocardial stretch

a) Increased EDV stretches the myocardium,
which increases contraction strength.
b) Due to increased myosin and actin overlap and
increased sensitivity to Ca2+ in cardiac muscle
cells

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24
Q

what is the Adjustment for rise in peripheral resistance?(Intrinsic Control of Contraction Strength.)

A

a) Increased peripheral resistance will
decrease stroke volume

b) More blood remains in the ventricles, so
EDV increases

c) Ventricles are stretched more, so they
contract more strongly

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25
Q

Extrinsic Control of Contractility

A

1) Contractility – strength of contraction at any
given fiber length

2) Sympathetic norepinephrine and adrenal
epinephrine (positive inotropic effect) can
increase contractility by making more Ca2+
available to sarcomeres. Also increases
heart rate.

3) Parasympathetic acetylcholine (negative
chronotropic effect) will decrease heart rate
which will increase EDV →increases
contraction strength →increases stroke
volume, but not enough to compensate for
slower rate, so cardiac output decreases

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26
Q

regulation of cardiac output equation

A

cardiac output=cardiac rate x stroke volume(total peripheral resistance and mean arterial pressure)

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27
Q

what is the distribution of blood at rest?

-small veins and venules, systemic veins, large veins
- capillaries
-systemic arteries
-heart
-lungs`

A
  • 60-70%
  • 4-5%
    -10-12%
    -8-11%
    -10-12%
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28
Q

what are the 3 factors in venous return?

A
  1. blood volume (uring volume, tissue filled fluid)
  2. negative intrathoracic pressure(breathing)
  3. venous pressure(skeletal muscle pump, sympathetic nerve stimulation–>venoconstriction)
29
Q

VENOUS RETURN

-what factors is end diastolic volume controlled by?

A

-factors that affect venous return:
1. total blood volume
2. venous pressure difference between arteries and veins(driving force for blood return)

30
Q

which stretches more: veins or arteries?

A

veins
(have higher compliance and thinner walls)

31
Q

where is most blood volume stored?

A

veins

32
Q

where is the pressure difference in the venous system(which has highest which has lowest)

A

highest pressure
in venules versus lowest pressure in venae cavae into the right atrium (0mm Hg)

33
Q

The rate of blood flow is inversely proportional to

A

the frictional resistance to blood flow within the vessels.

34
Q

what are the 2 most important factors in blood flow?

A
  1. mean arterial pressure
  2. vessel radius
35
Q

vasoconstriction of __________________ provides the
greatest resistance to blood flow and can
redirect flow to/from particular organs

A

arterioles

36
Q

______________ ____________ ____________ is The sum of all vascular resistance in systemic
circulation

A

total peripheral resistance

37
Q

Vasodilation in a large organ may : increase OR decrease
total peripheral resistance and mean arterial
pressure.

A

decrease

38
Q

Increase in cardiac output and increase total
peripheral resistance through release of
____________ onto smooth muscles of arterioles in
the viscera and skin to stimulate vasoconstriction
(alpha-adrenergic).

A

norepi

39
Q

____________ is released onto skeletal muscles,
resulting in increased vasodilation to these tissues
(cholinergic)

A

acetylcholine
(cholinergenic)

40
Q

____________ __________ stimulates beta-adrenergic receptors for
vasodilation

A

Adrenal epinephrine

41
Q

what neurotransmitter stimulates vasodilation

-located in

A

Acetylcholine

digestive tract, external genitalia, and
salivary glands

42
Q

what is reactive hypermia vs active hypermia

A

Reactive hyperemia – constriction causes
build-up of metabolic wastes which will then
cause vasodilation (reddish skin)

  1. Active hyperemia – increased blood flow
    during increased metabolism (reddish skin
43
Q

local vasodilation is controlled by changes in:(4)

A

1) Decreased oxygen concentrations due to
increased metabolism
2) Increased carbon dioxide concentrations
3) Decreased tissue pH (due to CO2, lactic acid, etc.)
4) Release of K+ and paracrine signals (nitric oxide
etc.)

44
Q

blood flow is restricted during what part of the cardiac cycle?

A

systole

45
Q

Regulation of Coronary Blood Flow:

____________ from sympathetic nerve fibers
(alpha-adrenergic) stimulates vasoconstriction,
raising vascular resistance at rest.

-_______________________________ (beta-adrenergic)
stimulates vasodilation and thus decreases
vascular resistance
during exercise.

-Vasodilation is enhanced by intrinsic metabolic
control mechanisms – __________________-__

A

Norepinephrine

-adrenal epi

-increased CO2, K+,
paracrine regulators

46
Q

what is an angiogram?

-what is a coronary angioplasty

A

-An angiogram is an X-ray picture with a contrast dye. An
angiogram of the coronary arteries might reveal narrowing
caused by atherosclerotic plaques, a thrombus, or a spasm. A
coronary angiogram is the standard method for assessing
coronary artery disease

-Coronary angioplasty is the technique of inserting a catheter
with a balloon into the occluded site of a coronary artery and
then inflating the balloon to push the artery open. Stents are
often inserted to support the opened section of the coronary
artery.
3. Coronary artery bypass grafting (CABG) surgery is the most
common open-heart surgery, involving the grafting of a vessel
taken from the patient onto the aorta so that it bypasses the
narrowed coronary artery.

47
Q

Arterioles have high vascular resistance at rest
due to:

A

alpha-adrenergic sympathetic stimulation

-Even at rest, skeletal muscles receive 20 to 25% of the body’s blood supply

48
Q

Regulation of Blood Flow Through
Skeletal Muscles(4 factors)

A
  1. Arterioles have high vascular resistance at rest
    due to alpha-adrenergic sympathetic stimulation
    a. Even at rest, skeletal muscles receive 20 to 25% of the
    body’s blood supply.
  2. Blood flow does decrease during contraction and
    can stop completely beyond 70% of maximum
    contraction.
  3. Vasodilation is stimulated by both adrenal
    epinephrine
  4. Intrinsic metabolic controls enhance vasodilation
    during exercise
49
Q

Blood Flow to the Brain and Skin (cerebral and cutaneous flow)

A
  1. Cerebral flow is primarily controlled by
    intrinsic mechanisms and is relatively
    constant; the brain can not tolerate much
    variation in blood flow.
  2. Cutaneous flow primarily controlled by
    extrinsic mechanisms and shows the most
    variation; can handle low rates of blood
    flow
50
Q

blood pressure is affected by:(4)

A

blood volume/stroke volume,
total peripheral resistance, and cardiac rate

a. Increase in any of these will increase blood
pressure.
b. Vasoconstriction of arterioles raises blood pressure
upstream in the arteries.
c. Arterial blood = cardiac X total peripheral
pressure output resistance

51
Q

Blood Pressure Regulation
a. Kidneys can control blood volume and thus
_______ ________
b. The sympathoadrenal system stimulates
vasoconstriction of arterioles (raising total
peripheral resistance) and increased cardiac
output.

A

stroke volume

52
Q

Hypertension can be classified as
“essential” or “secondary.

A

1) Essential or primary hypertension is a result of
complex and poorly understood processes
2) Secondary hypertension is a symptom of
another disease, such as kidney disease.

53
Q

what are some causes of ESSENTIAL HYPERTENSION(4)

A

a. Increased salt intake coupled with decreased
kidney filtering ability
b. Increased sympathetic nerve activity, increasing
heart rate
c. Responses to paracrine regulators from the
endothelium
d. Increased total peripheral resistance

54
Q

baroreceptor reflex is:
activated by:
most sensitive to:

A

one of the body’s homeostatic mechanisms that helps to maintain blood pressure at nearly constant levels

Activated by changes in blood pressure
detected by baroreceptors (stretch receptors)
in the aortic arch and carotid sinuses
2. Increased blood pressure stretches these
receptors, increasing action potentials to the
vasomotor and cardiac control centers in the
medulla.
3. Most sensitive to drops in blood pressure
4. The vasomotor center controls vasodilation and
constriction.
5. The cardiac center controls heart rate.
6. Fall in blood pressure = Increased
sympathetic and decreased
parasympathetic activity, resulting in
increased heart rate and total peripheral
resistance
7. Rise in BP has the opposite effects.
8. Good for quick beat-by-beat regulation like
going from lying down to standing

55
Q

difference between blood pressure at systole
and at diastole is

systole-diastole=PULSE PRESSURE

A

the pulse pressure

If your blood pressure is 120/80, your pulse
pressure is 40 mmHg. (120-80=40)
3. Pulse pressure is a reflection of stroke volume

56
Q

The average pressure in the arteries in
one cardiac cycle is the

A

mean arterial pressure

This is significant because it is the
difference between mean arterial
pressure and venous pressure that drives
the blood into the capillaries.
3. Calculated as:
diastolic pressure + 1/3 pulse pressure
From previous slide: DBP = 80 + 0.33 PP (40) = 93.2 mmHG

57
Q

Occurs when there is inadequate blood
flow to match oxygen usage in the tissues
a. Symptoms result from inadequate blood flow
and how our circulatory system changes to
compensate.
b. Sometimes shock leads to death.

A

circulatory shock

58
Q

what is it?
a. Due to low blood volume from an injury,
dehydration, or burns
b. Characterized by decreased cardiac output and
blood pressure
c. Blood is diverted to the heart and brain at the
expense of other organs.
d. Compensation includes baroreceptor reflex, which
lowers blood pressure, raises heart rate, raises
peripheral resistance, and produces cold, clammy
skin and low urine output.

A

hypovolemic shock

59
Q

what is it?
a. Dangerously low blood pressure
(hypotension) due to an infection (sepsis)
b. Bacterial toxins (endotoxins) induce NO
production, causing widespread
vasodilation.
c. Mortality rate is high (50 to 70%).

A

septic shock

60
Q

what are other other causes of circulatory shock?(3)

A

a. Severe allergic reactions can cause
anaphylactic shock due to production of
histamine and resulting vasodilation.
b. Spinal cord injury or anesthesis can
cause neurogenic shock due to loss of
sympathetic stimulation.
c. Cardiac failure can cause cardiogenic
shock due to significant myocardial loss

61
Q

what is this?]
1. Occurs when cardiac output is not
sufficient to maintain blood flow required
by the body
a. Caused by myocardial infarction, congenital
defects, hypertension, aortic valve stenosis,
or disturbances in electrolyte levels (K+ and
Ca2+)
b. Similar to hypovolemic shock in symptoms
and response

a. Left-side failure – raises left atrial pressure
and produces pulmonary congestion and
edema causing shortness of breath
b. Right-side failure – raises right atrial
pressure and produces systemic congestion
and edema

A

congestive heart failure

62
Q

what are the 2 types of congestive heart failure?

A

a. Left-side failure – raises left atrial pressure
and produces pulmonary congestion and
edema causing shortness of breath
b. Right-side failure – raises right atrial
pressure and produces systemic congestion
and edema

63
Q

what are 5 circulatory changes during dynamic exercise?

A
  1. Vascular resistance through skeletal and
    cardiac muscles decreases due to:
    a. Increased cardiac output
    b. Metabolic vasodilation
    c. Diversion of blood away from viscera and skin
  2. Blood flow to brain increases a small amount
    with moderate exercise and decreases a small
    amount during intense exercise
  3. Cardiac output can increase 5X due to
    increased cardiac rate.
  4. Stroke volume can increase some due to
    increased venous return from skeletal
    muscle pumps and respiratory movements
  5. Ejection fraction increases due to
    increased contractility
64
Q

what circulatory changes does endurance training result in?

A

a. Lower resting cardiac rate due to greater
inhibition of the SA node
b. Increase in stroke volume because of the
increase in blood volume
c. Improved O2 delivery

65
Q

paracrine regulation of blood flow:

A
  1. Used by some organs (brain and
    kidneys) to promote constant blood flow
    when there is fluctuation of blood
    pressure; also called autoregulation.
  2. Myogenic control mechanisms: Vascular
    smooth muscle responds to changes in
    arterial blood pressure.
    Paracrine Regulation of Blood Flow
  3. Molecules produced by one tissue control
    another tissue within the same organ.
    a. Example: The tunica interna produces signals to
    influence smooth muscle activity in the tunica media.
  4. Smooth muscle relaxation influenced by
    bradykinin, nitric oxide, and prostaglandin I2 to
    produce vasodilation
  5. Endothelin-1 stimulates smooth muscle
    contraction to produce vasoconstriction and raise
    total peripheral resistance.
66
Q

what are 3 aerobic requirements of the heart for exercise training?

A

a. Increased density of coronary arterioles and
capillaries
b. Increased production of NO to promote
vasodilation
c. Decreased compression of coronary arteries
during systole due to lower cardiac rate

67
Q

vasoconstriction

A

norepi

68
Q

vasodilation

A

epi

KPE 260 Human physiology (4 decks)

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