BIOC33H3 Lecture Notes - Cardiac Action Potential, Pacemaker Potential, Rectifier

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whitewombat192

15 Jan 2014

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Conduction system of the heart: sa node - fire fastest; ap depolarize the rest of it; depolarization spreads to atrial contractile cells. Neuronal action potential: resting membrane potential, slow depolarization to threshold, massive depolarization, repolarization, hyperpolarization phase, back to resting potential, these changes are due initially to increases in na permeability which carry large increases in membrane potential. Na permeability begins to decreases, k permeability increases, so we get repolarization. Hyperpolarization is due to k permeability changes - exits from cells (slightly delayed) K current that comes on slowly is referred to as a delayed rectifier. Pacemaker potential: pacemaker cells have no resting potential, once ap ends, they depolarize again, slow depolarization to threshold is our pacemaker potential and it is driven by a closure of funny channels = na influx. Cardiac action potential: phase 0: have a rapid increase in membrane potential; initial increase is seen by na influx, opening of voltage-gated na channels.

Related Questions

Tetraethylammonium (TEA) is a drug that blocks voltage-gated potassium channels. What effect would this have on an action potential?

(a)Prevent the rising phase

(b)Prevent the cell from reaching the threshold to trigger an action potential

(c)Prevent or prolong the falling phase

(d)None of the above

The hyperpolarization phase of the action potential is due to:

(a)The opening of voltage-gated Cl- channels

(b)Prolonged opening of voltage gated K+ channels

(c)The closure of resting Na+ channels

(d)Rapid inactivation of voltage-gated K+ channels

The period when it is difficult to initiate another action potential for several milliseconds due to voltage-gated sodium channel inactivation is referred to as the:

(a)Relative refractory period

(b)Absolute refractory period

(c)Resting period

(d)Hyperpolarization period

In the human central nervous system, Gap junctions are found:

(a)Only between neurons

(b)Only between astrocytes

(c)In both neurons and astrocytes

(d)In all cells

Small molecule transmitters such as acetylcholine are synthesized in:

(a)The nerve terminal

B) The cell body and transported to the nerve terminal

C) Synaptic vesicles

D) Endoplasmic reticulum

Prior to Otto Loewiâs classical experiment, which of the following was not known:

(a)stimulation of the vagus nerve slows the heart

(b)extracts of frog heart, made following vagal nerve stimulation, slow the heart

(c)some acetylcholine effects are similar to those produced by muscarine

(d)vagal nerve stimulation releases a substance which slows the heart

Which of the following is most important in determining if neurotransmission is excitatory or inhibitory?

(a)The structure of the synapse

(b)The neurotransmitter released by the presynaptic neuron

(c)The neurotransmitter receptor

(d)The strength of the stimulus

Benzodiazepines such as Valium allosterically regulate GABA receptors by:

(a)Binding at receptor sites other than the transmitter binding site

(b)Binding at the transmitter (GABA) binding site on the receptor

(c)Blocking the action of the endogenous transmitter

(d)Mimicking the action of the endogenous transmitter

GABA-A receptors are ligand-gated Cl- channels. The equilibrium potential of Cl- is -65 mV. At the neuronal resting membrane potential of -65 mV, GABA binding to the GABA-A receptor would result in the opening the Cl- channel, resulting in:

(a)no net flow of Cl- ions

(b)Cl- inflow and hyperpolarization

(c)Cl- outflow and depolarization

(d)Cl- outflow and hyperpolarization

At the mammalian neuromuscular junction, the released neurotransmitter acts on:

(a)muscarinic receptors

(b)nicotinic receptors

(c)adrenergic receptors

(d)Beta receptors

Neurotransmitters are packaged into synaptic vesicles by:

(a)endocytosis following transmitter release

(b)presynaptic membrane transporters

(c)vesicular transporters

(d)all of the above

. Which of the following are NOT types of ion channels?

Voltage-gated

(a)Ligand-gated

(b)G protein coupled receptor (GPCR)-gated

(c)Leak channels

(d)NONE of the above

NMDA receptors are unique in that their ion channel is:

(a)Ligand-gated

(b)Voltage-gated

(c)Ligand- and voltage-gated ion channels

(d)GPCR-gated

. Which of the following is INCORRECT regarding Catecholamine neurotransmitters

(a)Includes Dopamine, Norepinerphrine, and Epinephrine

(b)Contain a Catechol Ring

(c)Synthesized from Tryptophan

(d)Are produced by neurons whose cell bodies are located in the upper brainstem

The largest and most diverse group of receptors in eukaryotes is:

(a)Ligand gated receptors

(b)Glutamate receptors

(c)G-Protein coupled receptors

(d)Allosteric receptors

The most abundant G-protein coupled receptor in the brain is:

(a)Glutamate receptors

(b)Acetylcholine receptors

(c)Cannabinoid receptors

(d)Dopamine receptors

Which of the following drugs DOES NOT block voltage-gated Na+ channels

(a)Lidocaine

(b)Riluzole

(c)Reserpine

(d)Tetrodotoxin

Sarin, a nerve gas, exerts its toxicity by:

(a)blocking nicotinic receptors

(b)inhibiting choline acetyltransferase

(c)inhibiting acetylcholinesterase

(d)inhibiting voltage-gated Na+ channels

Botulinum Toxin (BoTox) interferes with transmitter release by:

(a)cleaving protein(s) involved in transmitter release

(b)blocking voltage-gated Ca2+ channels

(c)blocking voltage-gated Na+ channels

(d)blocking voltage-gated K+ channels

Atropine is:

(a)An agonist of the acetylcholine ionotropic receptor

(b)An antagonist of the acetylcholine ionotropic receptor

(c)An agonist of the acetylcholine metabotropic receptor

(d)An antagonist of the acetylcholine metabotropic receptor

1)What type of cell allows the immune system to respond morequickly if the same antigen is encountered a second time?

A)leukocytes

B)memory cells

C)macrophages

D)neutrophils

E)natual killer cells

2)why is the heart divided funtionally into two separate pumpsthat work in series?

A)because arteries carry blood away from the pump and veinsbring blood back to the pump

B)because blood decreases in pressure as it travels throughcirculation

C)because vessles in the vasculature keep blood moving in onedirection'

D)because there are four chambers to the heart

E)none of the above-the heart contracts in unison and is notdivided into two pumps

3)which of the following statements is correct?

A)Na+,K+, Ca2+ and Cl- are all more concentrated in theEXTRACELLULAR fluid

B)Na+, K+, Ca2+ and Cl- are all more concentrated in theEXTRACELLULAR fluid

C)Na+, Ca2+, and Cl- are all more concentrated in theEXTRACELLULAR fluid

D)K+, ca2+ are more concentrated in the EXTRACELLULAR fluid

E)K+, Ca2+ are more concentrated in the EXTRACELLULAR fluid

3)During skeletal muscle contraction:

A)the width of the H-zone decreases

B)the actin heads bind to myosin chain

C)ATP hydrolysis requires Ca2+ as a cofactor

D)tropomyosin changes conformation when Ca2+ binds

E)all of the above occur during skeletal muscle contraction

4)The rapid depolarization phase of myocardial contratile cellaction potential is due to the movement of which ion(s)?

A)Ca2+ flows into the cytosol

B)K+ flow out of the cytosol

C)Na+ flow into the cytosol

D)Ca2+ flow out of the cytosol

E)K+ flow into the cytosol

5)You are a physiology graduate student asked to study theeffect of ion permeability on the initiation of action potentials.You have isolated a cell with resting membrane potential of -70mVand have determined that the cell's threshold voltage is -55mV. Youthen change the cell to make it less permeable to K+ ions(Eions=-90mV)

With all ther condition staying the same, has cell's restingmembrane potential been DEPOLARIZED or HYPERPOLARIZED; and will thecell require a greater or smaller stimulus to reach threshold?

A)hyperpolarize; smaller

B)depolarize;greater

C)hyperpolarize;greater

D)depolarized; smaller

E)none of the above answers are possibe

6)Skeletal muscle cells are UNUSUAL in that they :

A)lack smooth endoplasmic reticulum

B)have no mitochondria

C)depend entirley on anaerobic respiration

D)have MULTIPLE nuclei

E)none of the baove are found in the skeletal muscle cells

7)What is the name for the autonomic nervous system synapses atthe neuroeffector?

A)electrical synapses

B)axon viscosities

C)bidirectional synapses

D)axon varicosities

E)light bulb synapse

8)Which cytokines are involvedin making cells resistant toviruses?

A)colony-stimulating actors

B)interferons

C)erythrpoietin

D)major histocompatibility complex

E)none of the above can make a cell resistant to a virus

9)If a person switiches from normal breathing to more shallowbreathing, whcih statement is true

A)tidal volume decreases

B)alveolar PO2 decreases

C)alveolar ventilation decreases

D)"a" and "b"

E)"a", "b', and "c"

10)Which scenerio supports hyperpolarization of pre-synapticcell?

A)allowing Cl- ions into the cell

B)allowing K+ ions to leave the cell

C)allowing Ca2+ ions into the cell

D)"a" and "b"

E)"a", "b", and "c"

11)The gap junctions in cardia muscle are part of specializedcell junctions that are localized to the__________.

A)transverse tubules

B)intercalated discs

C)Interdigitated fingers

D)desmosomes

E)high-end shppoinf malls

12)What role does myosin light chain kinase (MLCK) play insmooth muscle cell contraction?

A)dephosphorylates myosin

B)phosphorylates actin

C)phosphoylates myosin

D)dephosphorylates actin

E)both "a" and "c"Given that your forearm is 30cm long and yourbiceps inserts 2 cm away from your elbow joint, how much force mustyour biceps exert to hold up a 10kg weight?

A)0.67kg

B)6.0kg

C)20kg

d)150kg

e)600kg

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BIOC33H3 Lecture Notes - Cardiac Action Potential, Pacemaker Potential, Rectifier

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