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gen.exam.review > Costanza.Ch1.Cell physiology > Flashcards

Costanza.Ch1.Cell physiology Flashcards

1
Q

What substances can dissolve across the the lipid bilayer? and why?

A

Lipid soluble substances
**O2, CO2, Steroid hormones

–>b/c they can dissolve in the hydrophobic lipid bilayer

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2
Q

Cell membranes are composed primarily of what substances?

A

phospholipids
proteins

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3
Q

Which substances cannot pass the lipid bilayer of cells and why?

A

water-soluble sustabnces (e.g. Na, Cl, glucose, H2O)

–>cannot dissolve in the lipid of the membrane, but may cross through water-filled channels or pores or may be transported by carriers

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4
Q

Where are integral proteins located?

A

anchored to and imbedded in, the cell membrane through hydrophobic interactions
**may span the cell membrane

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5
Q

Give examples of integral proteins

A

ion channels
transport proteins
receptors
guanosine 5 triphosphate GTP-binding proteins (G proteins)

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6
Q

Describe peripheral proteins

A

-not imbedded in the cell membrane
-not covalently bound to membrane components
-loosely attached to the cell membrane by electrostatic interactions

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7
Q

Tight junctions are attachments between cells (often epithelial cells), which can have one of which two properties?

A

-tight (impermeable)– renal distal tubule

-leaky (permeable)– renal proximal tubule & gall bladder

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8
Q

Define gap junctions

A

attachments between cells that permit intercellular communication
–permit current flow and electrical coupling between myocardial cells

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9
Q

What are characteristics of simple diffusion?

A

-only form of transport that is not carrier mediated
-occurs down an electrochemical gradient
-does not require metabolic energy & therefore is passive

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10
Q

What are factors that increase permeability (ease at which a solute diffuses through a membrane)?

A

-INC oil/water partition coefficient of solut
-DEC radius (size) of the solute
-DEC membrane thickness

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11
Q

Which solutes have the highest permeabilities in lipid membranes?

A

small hydrophobic solutes (eg. O2, CO2)

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12
Q

what are the characteristics of carrier-mediated transport?

A

-stereospecificity
-saturation
-competition

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13
Q

What are characteristics of facilitated diffusion?

A

-occurs down an electrochemical gradient
-does not require metbaolic energy (passive)
-more rapid than simple diffsuion
**carrier mediated

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14
Q

What is an example of facilitated diffusion?

A

Glucose transport in mm and adipose cells
– inhibited by sugars– galactose
–ie. diabetes mellitus, glucose uptake by mm and adipose cells is impaired b/c carriers for facilitated diffusion of glucose requires insulin

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15
Q

What are characteristics of primary active transport?

A

-occurs against electrochemical gradient
-required direct input of metabolic energy in the form of ATP (active)
-is carrier mediated

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16
Q

Na, KATPase (Na-K pump), is an example of what form of transport? describe

A

-primary active transport

-transport Na from intracellular Na to extracellular fluid and K from extracellular to intracellular fluid
-both Na & K are transported against their electrochemical gradients

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17
Q

Where is the energy acquired from for primary active transport performed by Na, K ATPase?

A

terminal phosphate bond of ATP

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18
Q

What are specific inhibitors of Na, K-ATPase?

A

-cardiac glycoside drugs ouabain and digitalis

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19
Q

Where are H,K-ATPase located?

A

gastric parietal cells
-renal alpha intercalated cells transports H into lumen of the stomach or renal tubule against the electrochemical gradient

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19
Q

Where is Ca ATPase located?

A

In the sarcoplasmic reticulum or cell membranes transports Ca against an electrochemical gradient

**SERCA

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20
Q

Proton pump inhibitors, function by inhibiting which enzyme?

A

H, K-ATPase

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21
Q

What are characteristics of secondary active transport?

A

-transport of two or more solutes is coupled
-one of the solutes (usu Na) is transported “downhill” and provides energy for the “uphill” transport of the other solutes

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22
Q

Where is the metabolic energy come from, for secondary active transport?

A

-metabolic energy is not directly provided
-indirectly provided by Na gradient that maintained across cell membranes
**Ie inhibition of Na, K-ATPase will dec transport Na out of cell

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23
Q

If solutes move in the same direction across the cell membrane, it is called

A

cotransport or symport

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24
Q

What are examples of cotransport or symport?

A

Na glucose co transport in SI & renal proximal tubule
-Na-K-2Cl cotransport in renal thick ascending limb

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25
Q

If solutes move in the opposite directions across the cell membranes it is called?

A

countertransport
exchange
antiport

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26
Q

What are examples of countertransport/exchange/antiport?

A

Na-Ca exchange
Na-H exchange

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27
Q

Define osmolarity

A

the concentration of osmotically active particles in a solution

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28
Q

Define osmosis

A

the flow of water across a semipermeable membrane

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29
Q

Ion channels are integral proteins, with what properties:

A

-selective
-may be open or closed
-conductance of a channel depends on the channel is open

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30
Q

The higher the probability that an ion channel is open, the higher the….

A

conductance or permeability

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31
Q

What are voltage-gated channels open/closed by?

A

changes in membrane potential

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32
Q

The activation/inactivation of a sodium channel is opened/closed by

A

depolarization

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33
Q

Ligand gated channels are opened or closed by

A

hormones, second messengers or neurotransmitters

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34
Q

Name an example of a ligand-gated channel

A

nicotinic receptor for acetylcholine at the motor end plate is an ion channel that opens when ACh binds to it. when open, it is permeable to Na and K, causing the motor end plate to depolarize

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35
Q

Define diffusion potential

A

the potential difference generated across a membrane because of a concentration difference of an ion

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36
Q

The size of diffusion potential depends on

A

the size of the concentration gradient

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37
Q

The sign of the diffusion potential depends on

A

whether the diffusing ion is positively or negatively charged

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38
Q

The equilibrium potential is…

A

the potential difference that would exactly balance (oppose) the tendency for diffusion down a concentration difference

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39
Q

define electrochemical equilibrium

A

– the chemical and electrical driving forces that act on an ion are equal and opposite, and no further net diffusion of the ion occurs

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40
Q

What is the resting membrane potential established by?

A

diffusion potentials that result from concentration differences of permeant ions

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41
Q

At rest, the nerve membrane is far more permeable to which ion in comparison to Na?

A

K

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42
Q

How does the Na-K pump contribute to the resting membrane potential?

A

The Na-K pump contributes only indirectly to the resting membrane potential by maintaining, across the cell membrane, the Na and K concentration gradients that then produce diffusion potentials

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43
Q

Define depolarization

A

makes the membrane potential less negative ( the cell interior becomes less negative)

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44
Q

Define hyperpolarization

A

makes the membrane potential more negative (the cell interior becomes mroe negative)

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45
Q

Define Inward Current

A

is the flow of positive charge into the cell. Inward current depolarizes the membrane potential

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46
Q

define outward current

A

the flow of positive charge out of the cell. Outward current hyperpolarizes the membrane potential

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47
Q

Define action potential

A

property of excitable cells that consists of a rapid depolarization or upstroke, followed by repolarization of the membrane potential

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48
Q

Define threshold

A

membrane potential at which the action potential is inevitable

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49
Q

What is the resting membrane potential (value)?

A

-70 mV (cell negative)

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50
Q

The resting membrane potential is the result of high resting conductance to what electron?

A

K

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51
Q

Tetrodotoxin (TTX) and lidocaine block what channels?

A

voltage sensitive Na channels and abolish action potentials

52
Q

Define the absolute refractor period

A

the period during which another action potential cannot be elicited, no matter how large the stimulus

53
Q

Define relative refractory period

A

begins at the end of the absolute refractory period and continues until the membrane potential retrusn to the resting level
**an action potential elicited during the period only if a larger than usual inward current is provided

54
Q

Define accomodation

A

when the cell membrane is held at a depolarized level such that the threshold potential is passed without firing an action potential

55
Q

What is an example of accomodation?

A

hyperkalemia
– in which skeletal mm membranes are depolarized by the high serum K concentration
- the membrane potential is closer to threshold, action potentials do not occur b/c inactivation gates on Na channels are closed by depolarization, causing mm weakness

56
Q

Conduction velocity is increased by:

A
  1. INC fiber size
  2. myelination
57
Q

Describe saltatory conduction

A

-myelinated nerves
-action potential generated only at the nodes of Ranvier, where there are gaps in the myelin sheaths

58
Q

Inhibitory neurotransmitters hyperpolarize…

A

the postsynaptic membrane

59
Q

Excitatory neurotransmitters depolarize the….

A

postsynaptic membrane

60
Q

As a result of depolarization, what ion enters the presynpatic terminal?

A

calcium
**causes release of the neurotransmitter into the synaptic cleft

61
Q

What is the neurotransmitter released from the presynaptic terminal at neuromuscular junction?

A

acetylcholine

62
Q

At the neuromuscular junction, the postsynaptic membrane contains what receptor?

A

nicotinic receptor

63
Q

Describe the role of choline acetyltransferase

A

catalyzes the formation of ACh from acetyl coenzyme A (CoA) and choline in the presynaptic terminal

64
Q

Where is acetylcholine stored?

A

in synaptic vesicles with ATP and proteoglycan for later release

65
Q

Action potentials are conducted down the motoneuron. Depolarization of the presynaptic terminal causes

A

opens Ca channels

66
Q

Ca uptake causes the release of what into the synaptic cleft?

A

release of AcH

67
Q

Synaptic vesicles fuse with the palsma membrane and empty their contents into the cleft via

A

exocytosis

68
Q

Diffusion of Acetylcholine to the postysnaptic membrane– alpha subunits of the receptors causes

A

a conformational change that opens the central core of teh channel and increases its conductance to Na and K

69
Q

Describe what the end plate potential is

A

**not an action potential
– depolarization of the specialized mm end plate

70
Q

Acetylcholine is degraded to what two components and by which enzyme?

A

acetyl co A and choline
**by acetylcholinesterase (AcHE) on teh muscle end plate

71
Q

How does Botulinum toxin affect neuromuscular transmission?

A

-blocks release of ACH from presynpatic terminals
**total blockade of neuromuscular transmission

72
Q

How does Curare affect neuromuscular transmission?

A

-competes with ACh for receptors on motor end plates
–decreases size of EPP; maximal doses produce paralysis of respiratory mm and death

73
Q

How does Neostigmine affect neuromuscular transmission?

A

inhibits acetylcholinesterase
– prolongs and enhances action of ACh at mm end plate

74
Q

The disease myasthenia gravis is caused by

A

the presence of antibodies to the ACh receptor

75
Q

myasthenia gravis is characterized by skeletal mm weakness & fatigability resulting from

A

reduced number of ACh receptors on the muscle end plate

76
Q

What is the treatment for myasthenia gravis?

A

AChe inhibitors (eg. neostigmine) prevents the degradation of ACh and prolongs the action of ACH at the mm end plate, partially compensating for the reduced number of receptors

77
Q

Excitatory post-synaptic potentials (ESPS) are cause dby:

A

opening of channels that are pearmable to Na and K, similar to ACh channels. The membrane potential depolarizes to a value halfway between teh equilibrium potentials for Na and K

78
Q

List Excitatory neurotransmitters

A

ACh
norepinephrine
epinephrine
dopamine
glutamate
serotonin

79
Q

What are excitatory postynaptic potentials (EPSPs)

A

inputs that depolarize the postsynaptic cell, bringing it closer to threshold and closer to firing an action potential

80
Q

What are inhibitory postsynaptic potentials (IPSPs)?

A

are inputs that hyperpolarize the postsynaptic cell, moving it away from threshold and farther from firing an action potential

81
Q

How are inhibitory postsynaptic potentials created?

A

opening of Cl channels
–the membrane potential is hyperpolarized toward the CL equilibrium potential (-90mV)

82
Q

List inhibitory neurotransmitters

A

y-aminobutyric acid acid (GABA)
glycine

83
Q

Define spatial summation

A

occurs when two excitatory inputs arrive at a postsynaptic neuron simultaenously.

84
Q

Define temporal summation

A

occurs when two excitatory inputs arrive at a postsynaptic neuron in rapid succession. because of the resulting postsynaptic depolarizations overlap in time, they add in stepwise fashion

85
Q

What is the primary transmitter release from postganglionic sympathetic neurons?

A

norepinephrine

86
Q

norepinephrine is synthesized in the nerve terminal and release into the synapse to bind with what, on the postsynaptic membrane?

A

alpha or beta receptors

87
Q

norepinephrine is removed from the synapse by

A

-reuptake
-metabolized in hte presynaptic terminal by moamine oxidase (MAO) and catechol-O-methyltransferase (COMT)

88
Q

Where in epinephrine synthesized by?

A

from norepinephrine by teh action of phenylethanolamine-N-methyltransferase in the adrenal medulla

89
Q

Where is Dopamin released from?

A

hypothalamus

90
Q

What is the action of Dopamine?

A

inhibits prolactin secretion

91
Q

D1 receptors

A

activate adenylate cyclase via a Gs protein

92
Q

D2 receptors

A

inhibit adenylate cyclase via a Gi protein

93
Q

Serotonin is formed from

A

tryptophan

94
Q

which neurotransmitter is converted to melatonin in the pineal gland?

A

serotonin

95
Q

What is the most prevalent excitatory neurotransmitter in the brain?

A

glutamate

96
Q

GABA is an excitatory or inhibitory neurontrasmitter

A

inhibitory neurotransmitter

97
Q

GABA is synthesized from

A

glutamate by glutamate decarboxylase

98
Q

What receptors is the site of action of benzodiazepines and barbiturates?

A

GABAb receptor
**increases Cl conductance

99
Q

Glycine is an excitatory or inhibitory neurotransmitter?

A

inhibitory

100
Q

Nitric oxide is an excitatory or inhibitory neurotransmitter?

A

inhibitory in GIT, blood vessels and CNS

101
Q

Nitric oxide is synthesized where?

A

presynaptic nerve terminals, where NO synthase converts arginine to citrulline and NO

102
Q

Sarcomeres are made up of

A

interdigitating thick and thin filaments arranged longitudinally

103
Q

What accounts for the unique banding pattern in striated muscle?

A

repeating units of sarcomeres
**sarcomere runs from Z line to Zline

104
Q

What are thick muscle filaments made up of?

A

-present in A band in teh center of the sarcomere
-contains myosin

105
Q

Each myosin is amade up of two heads attached to a single tail, what is the job of the mysoin heads?

A

the myosin heads bind aTP and actin and are involved in cross-bridge formation

106
Q

Describe thin muscle filaments

A

-anchored at the Zlines
-present in the I bands
-interdigitate with the thick filaments in a portion fo the A band
-contain actin, tropomyosin, and troponin

107
Q

What is the function of troponin in skeletal muscle?

A

regulatory protein that permits cross-bridge formation when it binds Ca

108
Q

Function of Troponin T

A

T-for tropomyosin
-attaches the troponin complex to tropomyosin

109
Q

Function of Troponin I

A

-I for inhibition
-inhibits the interaction of actin and myosin

110
Q

Function of Troponin C

A

-C for Ca
-is the Ca binding protein that, when bound to Ca, permits the interaction of actin and myosin

111
Q

Describes T tubules

A

-are extensive tubular network, open to the extracellular space, that carry the depolarization from the sacrolemmel membrane to the cell interior
-located at the junctions of A abnds and I bands
-contain a voltage- sensitive protein called the dihydropyridine receptor

112
Q

SR is the internal tubular structures that is the site of:

A

Ca storage and release for excitation and contraction coupling

113
Q

Describe the function of Ca-ATPase (Ca pump) function in the SR

A

transports Ca from intracellular fluid into the SR interior, keeping intracellular Ca low

114
Q

What structure in the skeletal muscle contains ryanodine receptor?

A

SR

115
Q

What is the ryanodine receptor?

A

contains a Ca release channel

116
Q

Ca in the SR is bound loosely to

A

Calsequestrin

117
Q

What are the steps in excitation-contraction coupling in skeletal muscle?

A
  1. action potential in the muscle membrane
  2. depolarization of T tubules
  3. opens Ca release channels in SR
  4. INC intracellular Ca
  5. Ca binds to troponin C
  6. Cross-bridge cycling
  7. Ca reaccumulated by SR
  8. Relaxation
118
Q

What is the mechanism of tetanus?

A

-a single action potential causes the release of a standard amount of Ca form the SR and produces a single twitch
-if mm is stimulated repeatedly, more ca is released from the SR and there is a cumulative increase in intracellular Ca, extending the time for cross-bridge cycling
**The muscle does not relax (tetanus)

119
Q

What type of muscle does not have sarcomeres?

A

-thick and thin filaments that are not arranged in sarcomeres
**appears more homogenous rather than striated

120
Q

What are examples of multiunit smooth muscle throughout the body?

A

-iris, ciliary mm of the lens and vas deferens

121
Q

How does multiunit smooth muscle function?

A

-behaves as separate motor units
-has little or no electrical coupling between cells
-densely innerves; contraction is controlled by neural innervation

122
Q

What are examples of unitary (single-unit) smooth muscle?

A

-uterus, gastrointestinal tract, ureter & bladder

123
Q

How does unitary (single-unit) smooth muscle function?

A

spontaneously active (exhibits slow waves) and exhibits “pacemaker” activity, which is modulated by hormones and neurotransmitters
**has a high degree of electrical coupling between cells and permits coordinated contraction of the organ

124
Q

Vascular smooth muscle has properties of

A

both multiunit and single-unit smooth muscle

125
Q

What makes the mechanism of excitation-contraction coupling is different fromt hat in skeletal muscle

A

**there is no troponin; instead, Ca regulates myosin on the thick filaments

126
Q

What are the steps in the contraction of smooth muscle

A

1a. depolarization
b. hormones or neurotransmitters
2. a. open voltage gaited channels
b. open ligand gates Ca chennls
3. Ca induces ca release from SR
4. ICN Ca
5. Ca-calmodulin (CaM)
6. INC myosin light chain kinase
7. phosphorylation of myosin light chains
8. INC myosin ATPase
9. Myosin-P +actin
10. Cross bridge cycling
11. Tension

127
Q

Describe the differences in excitation- contraction coupling between skeletal mm, smooth mm and cardiac muscle?

A

Skeletal MM: action potential–> T tubules; Ca released from nearby SR (INC Ca)

Smooth MM: action potential opens volatge-gated Ca channels in cell membrane; hormones and transmitters open IP3 gated Ca channels in SR

Cardiac MM: inward Ca current during plateau of action potential; Ca induced Ca release from SR; INC Ca

gen.exam.review (7 decks)

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