Circulation 4 Flashcards
1
Q
cardiac cycle (2)
A
- pumping action of the heart
- contains two phases: systole and diastole
2
Q
cardiac cycle: systole (2)
A
- contraction/pressure-generating
- blood is forced out into the circulation
3
Q
cardiac cycle: diastole (2)
A
- relaxation
- blood enters the heart
4
Q
fish cardiac cycle (2)
A
- serial contractions of chambers
- valves are passive
5
Q
fish cardiac cycle: valves (2)
A
- valves open and close according to pressure differences
- assure unidirectional flow of blood
6
Q
fish cardiac cycle: bulbus arteriosus
A
- in teleosts, noncontractile bulbus arteriosus serves as volume and pressure reservoir
7
Q
mammal cardiac cycle (2)
A
- atria and ventricles alternate systole and diastole
- maximizes stroke volume and therefore, cardiac output
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
9
Q
mammal cardiac cycle simplified (5)
A
- ventricular diastole 1
- atrial systole
- ventricular systole 1
- ventricular systole 2
- ventricular diastole 2
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
11
Q
mammal cardiac cycle: atrial systole (2)
A
- atrial contraction forces additional blood into ventricles
- ventricles are in diastole
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
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
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
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
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
17
Q
left ventricular pressure
A
- contracts more forcefully and develops higher pressure to pump blood to body/systemic system
18
Q
right ventricular pressure
A
- contracts less forcefully as less pressure is needed to pump blood through the lungs
19
Q
characteristics of the pulmonary circuit system (2)
A
- resistance is low due to high capillary density in parallel
- large cross-sectional area
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
artificial pacemakers
- rhythm generated by a device
26
control of cardiac contraction: vertebrates (3)
- hearts are myogenic
- electrically coupled cardiomyocytes produce spontaneous rhythmic depolarizations
- does not require nerve signal
27
how are cardiomyocytes electrically coupled (2)
- via gap junctions to ensure coordinated contractions
- allows action potentials to pass direction from cell to cell
28
vertebrate pacemaker location (2)
- in sinus venosus of fish
- in right atrium at the sino-atrial (SA) node of tetrapods (amphibians, reptiles, birds, mammals)
29
cell membrane state (3)
- polarized
- the resting (stable) membrane potential is negative relative to the outside
- -60mV to -110mV inside
30
what creates the resting membrane potential (2)
- created by ATPases working against selectively permeable ion channels
- results in ionic gradients across the cell membrane
31
why are electrochemical gradients important in cell membranes
- create the 'battery' for life by providing electrical potential energy for many cell activities
32
what cells are excitable (2)
- cells that become 'excited' due to brief changes in ion channel permeabilities
- eg. neurons and muscles
33
muscle cell action potentials (2)
- voltage-gated ion channels can open in muscles cells to create an action potential
- action potential will trigger muscle contraction
34
pacemaker cells (3)
- derived from cardiomyocytes
- small, with few myofibrils, mitochondria, or other organelles
- do not contract; lack contractile tissues
35
pacemaker cells: resting membrane potential (2)
- have unstable resting membrane potential (pacemaker potential)
- this potential depolarizes until it reaches threshold and initiates an action potential
36
vertebrate pacemaker action potential (4)
- cell gradually depolarizes to threshold (-60mV to -40 mV)
- voltage-gated channels open
- initiates "spike", or the action potential
- cell repolarizes
37
what causes the unstable resting membrane potentials in pacemaker cells (2)
- slow decrease in K+ permeability
- opening of "funny" channels (Na+ channels), increasing Na+ permeability
38
what causes the action potential/spike in pacemaker cells
- voltage-gated Ca2+ channels open, increasing Ca2+ permeability
39
what initiates repolarization in pacemaker cells
- K+ channels open, increasing K+ permeability
40
what support repolarization in pacemaker cells
- "funny" channels (Na+ channels) close, decreasing Na+ permeability
41
what are the major differences between action potentials and pacemaker action potentials (2)
- 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
nervous system modulation of pacemakers (3)
- no modulation
- sympathetic stimulation
- parasympathetic stimulation
43
nervous system modulation of pacemakers: no modulation
- no hormonal influence, so rate of depolarization is "normal"
44
nervous system modulation of pacemakers: sympathetic nervous system stimulation
- increases rate of pacemaker potentials
45
nervous system modulation of pacemakers: parasympathetic nervous system stimulation
- decreases rate of pacemaker potentials
46
control of pacemaker potentials: increasing heart rate (3)
- hormones and origin
- voltage-gated channels affected
- result
- 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
increasing heart rate: pathway (6)
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
control of pacemaker potentials: decreasing heart rate (4)
- hormones and origin
- voltage-gated channels
- results (2)
- 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
decreasing heart rate: pathway (4)
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
