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BIOL 364 > Circulation 4 > Flashcards

Circulation 4 Flashcards

1
Q

cardiac cycle (2)

A
  • pumping action of the heart
  • contains two phases: systole and diastole
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2
Q

cardiac cycle: systole (2)

A
  • contraction/pressure-generating
  • blood is forced out into the circulation
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3
Q

cardiac cycle: diastole (2)

A
  • relaxation
  • blood enters the heart
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4
Q

fish cardiac cycle (2)

A
  • serial contractions of chambers
  • valves are passive
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5
Q

fish cardiac cycle: valves (2)

A
  • valves open and close according to pressure differences
  • assure unidirectional flow of blood
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6
Q

fish cardiac cycle: bulbus arteriosus

A
  • in teleosts, noncontractile bulbus arteriosus serves as volume and pressure reservoir
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7
Q

mammal cardiac cycle (2)

A
  • atria and ventricles alternate systole and diastole
  • maximizes stroke volume and therefore, cardiac output
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8
Q

mammal cardiac cycle steps (4)

A
  • two atria contract simultaneously
  • there is a slight pause
  • two ventricles contract simultaneously
  • atria and ventricles relax while the heart fills with blood
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9
Q

mammal cardiac cycle simplified (5)

A
  • ventricular diastole 1
  • atrial systole
  • ventricular systole 1
  • ventricular systole 2
  • ventricular diastole 2
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10
Q

mammal cardiac cycle: ventricular diastole 1 (3)

A
  • pressure in atria exceeds ventricular pressure
  • AV valves open and the ventricles passively fill
  • atria is in diastole
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11
Q

mammal cardiac cycle: atrial systole (2)

A
  • atrial contraction forces additional blood into ventricles
  • ventricles are in diastole
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12
Q

mammal cardiac cycle: ventricular systole 1 (3)

A
  • isovolumetric contraction (volume remains the same)
  • ventricular contraction pushes AV valves closed and increases pressure inside the ventricle
  • atria are in diastole
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13
Q

mammal cardiac cycle: ventricular systole 2 (3)

A
  • ventricular ejection
  • increased ventricular pressure forces the semilunar valves open and blood is ejected
  • atria are in diastole
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14
Q

mammal cardiac cycle: ventricular diastole 2 (3)

A
  • as ventricles relax, pressure in arteries exceeds ventricular pressure
  • semilunar valves close
  • atria in diastole
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15
Q

birds/mammals: ventricular filling (2)

A
  • fill passively during diastole due to venous pressure
  • atrial contraction adds a little blood to the ventricles
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16
Q

fish/some amphibians: ventricular filling (2)

A
  • ventricles actively filled by contraction of atrium
  • they generate little passive ventricular filling due to low venous pressure after going through two capillary beds
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17
Q

left ventricular pressure

A
  • contracts more forcefully and develops higher pressure to pump blood to body/systemic system
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18
Q

right ventricular pressure

A
  • contracts less forcefully as less pressure is needed to pump blood through the lungs
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19
Q

characteristics of the pulmonary circuit system (2)

A
  • resistance is low due to high capillary density in parallel
  • large cross-sectional area
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20
Q

why is the pulmonary circuit a low pressure system (2)

A
  • protects delicate blood vessels of lungs
  • prevents edema that would be caused by fluids exiting the blood into the lungs
21
Q

circuit blood flow

A
  • systemic and pulmonary circuits have the same total blood flow
22
Q

control of cardiac contraction (3)

A
  • neurogenic pacemakers
  • myogenic pacemakers
  • artificial pacemakers
23
Q

neurogenic pacemakers (2)

A
  • rhythm generated in neurons
  • present in some invertebrates
24
Q

myogenic pacemakers (2)

A
  • rhythm generated in myocytes
  • present in vertebrates and some invertebrates
25
Q

artificial pacemakers

A
  • rhythm generated by a device
26
Q

control of cardiac contraction: vertebrates (3)

A
  • hearts are myogenic
  • electrically coupled cardiomyocytes produce spontaneous rhythmic depolarizations
  • does not require nerve signal
27
Q

how are cardiomyocytes electrically coupled (2)

A
  • via gap junctions to ensure coordinated contractions
  • allows action potentials to pass direction from cell to cell
28
Q

vertebrate pacemaker location (2)

A
  • in sinus venosus of fish
  • in right atrium at the sino-atrial (SA) node of tetrapods (amphibians, reptiles, birds, mammals)
29
Q

cell membrane state (3)

A
  • polarized
  • the resting (stable) membrane potential is negative relative to the outside
  • -60mV to -110mV inside
30
Q

what creates the resting membrane potential (2)

A
  • created by ATPases working against selectively permeable ion channels
  • results in ionic gradients across the cell membrane
31
Q

why are electrochemical gradients important in cell membranes

A
  • create the ‘battery’ for life by providing electrical potential energy for many cell activities
32
Q

what cells are excitable (2)

A
  • cells that become ‘excited’ due to brief changes in ion channel permeabilities
  • eg. neurons and muscles
33
Q

muscle cell action potentials (2)

A
  • voltage-gated ion channels can open in muscles cells to create an action potential
  • action potential will trigger muscle contraction
34
Q

pacemaker cells (3)

A
  • derived from cardiomyocytes
  • small, with few myofibrils, mitochondria, or other organelles
  • do not contract; lack contractile tissues
35
Q

pacemaker cells: resting membrane potential (2)

A
  • have unstable resting membrane potential (pacemaker potential)
  • this potential depolarizes until it reaches threshold and initiates an action potential
36
Q

vertebrate pacemaker action potential (4)

A
  • cell gradually depolarizes to threshold (-60mV to -40 mV)
  • voltage-gated channels open
  • initiates “spike”, or the action potential
  • cell repolarizes
37
Q

what causes the unstable resting membrane potentials in pacemaker cells (2)

A
  • slow decrease in K+ permeability
  • opening of “funny” channels (Na+ channels), increasing Na+ permeability
38
Q

what causes the action potential/spike in pacemaker cells

A
  • voltage-gated Ca2+ channels open, increasing Ca2+ permeability
39
Q

what initiates repolarization in pacemaker cells

A
  • K+ channels open, increasing K+ permeability
40
Q

what support repolarization in pacemaker cells

A
  • “funny” channels (Na+ channels) close, decreasing Na+ permeability
41
Q

what are the major differences between action potentials and pacemaker action potentials (2)

A
  • pacemaker cells are never resting; they continue to create action potentials regardless if stimulus is present
  • stimulus is what alters the membrane potential to trigger an action potential in other cells, and cells rest in-between stimulus
42
Q

nervous system modulation of pacemakers (3)

A
  • no modulation
  • sympathetic stimulation
  • parasympathetic stimulation
43
Q

nervous system modulation of pacemakers: no modulation

A
  • no hormonal influence, so rate of depolarization is “normal”
44
Q

nervous system modulation of pacemakers: sympathetic nervous system stimulation

A
  • increases rate of pacemaker potentials
45
Q

nervous system modulation of pacemakers: parasympathetic nervous system stimulation

A
  • decreases rate of pacemaker potentials
46
Q

control of pacemaker potentials: increasing heart rate (3)
- hormones and origin
- voltage-gated channels affected
- result

A
  • norepinephrine released from sympathetic neurons and epinephrine released from the adrenal medulla
  • more Na+ and Ca2+ channels open
  • rate of depolarization and frequency of action potentials increase
47
Q

increasing heart rate: pathway (6)

A
  1. cardiovascular control center (medulla) stimulates sympathetic neurons
  2. neurons release norepinephrine and stimulate the adrenal medulla to release epinephrine
  3. norepinephrine and epinephrine bind to beta-receptors of autorhythmic cells
  4. signaling cascade occurs, resulting in release of cAMP and activation of protein kinases
  5. funny and Ca2+ channels open, resulting in an influx of Na+ and Ca2+
  6. rate of depolarization increases, resulting in increased heart rate
48
Q

control of pacemaker potentials: decreasing heart rate (4)
- hormones and origin
- voltage-gated channels
- results (2)

A
  • acetylcholine released from parasympathetic neurons
  • more K+ channels open
  • pacemaker cells hyperpolarize
  • time for depolarization takes longer, causing frequency of action potentials to decrease
49
Q

decreasing heart rate: pathway (4)

A
  1. cardiovascular control center (medulla) stimulates parasympathetic neurons to release acetylcholine
  2. acetylcholine binds muscarinic receptors of autorhythmic cells
  3. signaling cascade results in closing of funny channels and opening of K+ channels so that Ca2+ cannot enter and K+ can leave
  4. cell hyperpolarizes, increasing time for depolarization and decreasing heart rate

BIOL 364 (44 decks)

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