Final: Circulation 4

Question 1

cardiac cycle (2)

Answer 1

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

Question 2

cardiac cycle: systole (2)

Answer 2

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

Question 3

cardiac cycle: diastole (2)

Answer 3

• relaxation
• blood enters the heart

Question 4

fish cardiac cycle (2)

Answer 4

• serial contractions of chambers
• valves are passive

Question 5

fish cardiac cycle: valves (2)

Answer 5

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

Question 6

fish cardiac cycle: bulbus arteriosus

Answer 6

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

Question 7

mammal cardiac cycle (2)

Answer 7

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

Question 8

mammal cardiac cycle steps (4)

Answer 8

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

Question 9

mammal cardiac cycle simplified (5)

Answer 9

• ventricular diastole 1
• atrial systole
• ventricular systole 1
• ventricular systole 2
• ventricular diastole 2

Question 10

mammal cardiac cycle: ventricular diastole 1 (3)

Answer 10

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

Question 11

mammal cardiac cycle: atrial systole (2)

Answer 11

• atrial contraction forces additional blood into ventricles
• ventricles are in diastole

Question 12

mammal cardiac cycle: ventricular systole 1 (3)

Answer 12

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

Question 13

mammal cardiac cycle: ventricular systole 2 (3)

Answer 13

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

Question 14

mammal cardiac cycle: ventricular diastole 2 (3)

Answer 14

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

Question 15

birds/mammals: ventricular filling (2)

Answer 15

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

Question 16

fish/some amphibians: ventricular filling (2)

Answer 16

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

Question 17

left ventricular pressure

Answer 17

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

Question 18

right ventricular pressure

Answer 18

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

Question 19

characteristics of the pulmonary circuit system (2)

Answer 19

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

Question 20

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

Answer 20

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

Question 21

circuit blood flow

Answer 21

• systemic and pulmonary circuits have the same total blood flow

Question 22

control of cardiac contraction (3)

Answer 22

• neurogenic pacemakers
• myogenic pacemakers
• artificial pacemakers

Question 23

neurogenic pacemakers (2)

Answer 23

• rhythm generated in neurons
• present in some invertebrates

Question 24

myogenic pacemakers (2)

Answer 24

• rhythm generated in myocytes
• present in vertebrates and some invertebrates

Question 25

artificial pacemakers

Answer 25

- rhythm generated by a device

Question 26

control of cardiac contraction: vertebrates (3)

Answer 26

- hearts are myogenic - electrically coupled cardiomyocytes produce spontaneous rhythmic depolarizations - does not require nerve signal

Question 27

how are cardiomyocytes electrically coupled (2)

Answer 27

- via gap junctions to ensure coordinated contractions - allows action potentials to pass direction from cell to cell

Question 28

vertebrate pacemaker location (2)

Answer 28

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

Question 29

cell membrane state (3)

Answer 29

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

Question 30

what creates the resting membrane potential (2)

Answer 30

- created by ATPases working against selectively permeable ion channels - results in ionic gradients across the cell membrane

Question 31

why are electrochemical gradients important in cell membranes

Answer 31

- create the 'battery' for life by providing electrical potential energy for many cell activities

Question 32

what cells are excitable (2)

Answer 32

- cells that become 'excited' due to brief changes in ion channel permeabilities - eg. neurons and muscles

Question 33

muscle cell action potentials (2)

Answer 33

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

Question 34

pacemaker cells (3)

Answer 34

- derived from cardiomyocytes - small, with few myofibrils, mitochondria, or other organelles - do not contract; lack contractile tissues

Question 35

pacemaker cells: resting membrane potential (2)

Answer 35

- have unstable resting membrane potential (pacemaker potential) - this potential depolarizes until it reaches threshold and initiates an action potential

Question 36

vertebrate pacemaker action potential (4)

Answer 36

- cell gradually depolarizes to threshold (-60mV to -40 mV) - voltage-gated channels open - initiates "spike", or the action potential - cell repolarizes

Question 37

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

Answer 37

- slow decrease in K+ permeability - opening of "funny" channels (Na+ channels), increasing Na+ permeability

Question 38

what causes the action potential/spike in pacemaker cells

Answer 38

- voltage-gated Ca2+ channels open, increasing Ca2+ permeability

Question 39

what initiates repolarization in pacemaker cells

Answer 39

- K+ channels open, increasing K+ permeability

Question 40

what support repolarization in pacemaker cells

Answer 40

- "funny" channels (Na+ channels) close, decreasing Na+ permeability

Question 41

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

Answer 41

- 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

Question 42

nervous system modulation of pacemakers: no modulation

Answer 42

- no hormonal influence, so rate of depolarization is "normal"

Question 43

nervous system modulation of pacemakers: sympathetic nervous system stimulation

Answer 43

- increases rate of pacemaker potentials

Question 44

nervous system modulation of pacemakers (3)

Answer 44

- no modulation - sympathetic stimulation - parasympathetic stimulation

Question 45

nervous system modulation of pacemakers: parasympathetic nervous system stimulation

Answer 45

- decreases rate of pacemaker potentials

Question 46

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

Answer 46

- 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

Question 47

increasing heart rate: pathway (6)

Answer 47

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

Question 48

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

Answer 48

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

Question 49

decreasing heart rate: pathway (4)

Answer 49

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