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Gen.Exam.Review > Costanza.Ch1.Cell physiology > Flashcards

Costanza.Ch1.Cell physiology Flashcards

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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
What are examples of cotransport or symport?
Na glucose co transport in SI & renal proximal tubule -Na-K-2Cl cotransport in renal thick ascending limb
25
If solutes move in the opposite directions across the cell membranes it is called?
countertransport exchange antiport
26
What are examples of countertransport/exchange/antiport?
Na-Ca exchange Na-H exchange
27
Define osmolarity
the concentration of osmotically active particles in a solution
28
Define osmosis
the flow of water across a semipermeable membrane
29
Ion channels are integral proteins, with what properties:
-selective -may be open or closed -conductance of a channel depends on the channel is open
30
The higher the probability that an ion channel is open, the higher the....
conductance or permeability
31
What are voltage-gated channels open/closed by?
changes in membrane potential
32
The activation/inactivation of a sodium channel is opened/closed by
depolarization
33
Ligand gated channels are opened or closed by
hormones, second messengers or neurotransmitters
34
Name an example of a ligand-gated channel
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
35
Define diffusion potential
the potential difference generated across a membrane because of a concentration difference of an ion
36
The size of diffusion potential depends on
the size of the concentration gradient
37
The sign of the diffusion potential depends on
whether the diffusing ion is positively or negatively charged
38
The equilibrium potential is...
the potential difference that would exactly balance (oppose) the tendency for diffusion down a concentration difference
39
define electrochemical equilibrium
-- the chemical and electrical driving forces that act on an ion are equal and opposite, and no further net diffusion of the ion occurs
40
What is the resting membrane potential established by?
diffusion potentials that result from concentration differences of permeant ions
41
At rest, the nerve membrane is far more permeable to which ion in comparison to Na?
K
42
How does the Na-K pump contribute to the resting membrane potential?
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
43
Define depolarization
makes the membrane potential less negative ( the cell interior becomes less negative)
44
Define hyperpolarization
makes the membrane potential more negative (the cell interior becomes mroe negative)
45
Define Inward Current
is the flow of positive charge into the cell. Inward current depolarizes the membrane potential
46
define outward current
the flow of positive charge out of the cell. Outward current hyperpolarizes the membrane potential
47
Define action potential
property of excitable cells that consists of a rapid depolarization or upstroke, followed by repolarization of the membrane potential
48
Define threshold
membrane potential at which the action potential is inevitable
49
What is the resting membrane potential (value)?
-70 mV (cell negative)
50
The resting membrane potential is the result of high resting conductance to what electron?
K
51
Tetrodotoxin (TTX) and lidocaine block what channels?
voltage sensitive Na channels and abolish action potentials
52
Define the absolute refractor period
the period during which another action potential cannot be elicited, no matter how large the stimulus
53
Define relative refractory period
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
Define accomodation
when the cell membrane is held at a depolarized level such that the threshold potential is passed without firing an action potential
55
What is an example of accomodation?
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
Conduction velocity is increased by:
1. INC fiber size 2. myelination
57
Describe saltatory conduction
-myelinated nerves -action potential generated only at the nodes of Ranvier, where there are gaps in the myelin sheaths
58
Inhibitory neurotransmitters hyperpolarize...
the postsynaptic membrane
59
Excitatory neurotransmitters depolarize the....
postsynaptic membrane
60
As a result of depolarization, what ion enters the presynpatic terminal?
calcium **causes release of the neurotransmitter into the synaptic cleft
61
What is the neurotransmitter released from the presynaptic terminal at neuromuscular junction?
acetylcholine
62
At the neuromuscular junction, the postsynaptic membrane contains what receptor?
nicotinic receptor
63
Describe the role of choline acetyltransferase
catalyzes the formation of ACh from acetyl coenzyme A (CoA) and choline in the presynaptic terminal
64
Where is acetylcholine stored?
in synaptic vesicles with ATP and proteoglycan for later release
65
Action potentials are conducted down the motoneuron. Depolarization of the presynaptic terminal causes
opens Ca channels
66
Ca uptake causes the release of what into the synaptic cleft?
release of AcH
67
Synaptic vesicles fuse with the palsma membrane and empty their contents into the cleft via
exocytosis
68
Diffusion of Acetylcholine to the postysnaptic membrane-- alpha subunits of the receptors causes
a conformational change that opens the central core of teh channel and increases its conductance to Na and K
69
Describe what the end plate potential is
**not an action potential -- depolarization of the specialized mm end plate
70
Acetylcholine is degraded to what two components and by which enzyme?
acetyl co A and choline **by acetylcholinesterase (AcHE) on teh muscle end plate
71
How does Botulinum toxin affect neuromuscular transmission?
-blocks release of ACH from presynpatic terminals **total blockade of neuromuscular transmission
72
How does Curare affect neuromuscular transmission?
-competes with ACh for receptors on motor end plates --decreases size of EPP; maximal doses produce paralysis of respiratory mm and death
73
How does Neostigmine affect neuromuscular transmission?
inhibits acetylcholinesterase -- prolongs and enhances action of ACh at mm end plate
74
The disease myasthenia gravis is caused by
the presence of antibodies to the ACh receptor
75
myasthenia gravis is characterized by skeletal mm weakness & fatigability resulting from
reduced number of ACh receptors on the muscle end plate
76
What is the treatment for myasthenia gravis?
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
Excitatory post-synaptic potentials (ESPS) are cause dby:
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
List Excitatory neurotransmitters
ACh norepinephrine epinephrine dopamine glutamate serotonin
79
What are excitatory postynaptic potentials (EPSPs)
inputs that depolarize the postsynaptic cell, bringing it closer to threshold and closer to firing an action potential
80
What are inhibitory postsynaptic potentials (IPSPs)?
are inputs that hyperpolarize the postsynaptic cell, moving it away from threshold and farther from firing an action potential
81
How are inhibitory postsynaptic potentials created?
opening of Cl channels --the membrane potential is hyperpolarized toward the CL equilibrium potential (-90mV)
82
List inhibitory neurotransmitters
y-aminobutyric acid acid (GABA) glycine
83
Define spatial summation
occurs when two excitatory inputs arrive at a postsynaptic neuron simultaenously.
84
Define temporal summation
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
What is the primary transmitter release from postganglionic sympathetic neurons?
norepinephrine
86
norepinephrine is synthesized in the nerve terminal and release into the synapse to bind with what, on the postsynaptic membrane?
alpha or beta receptors
87
norepinephrine is removed from the synapse by
-reuptake -metabolized in hte presynaptic terminal by moamine oxidase (MAO) and catechol-O-methyltransferase (COMT)
88
Where in epinephrine synthesized by?
from norepinephrine by teh action of phenylethanolamine-N-methyltransferase in the adrenal medulla
89
Where is Dopamin released from?
hypothalamus
90
What is the action of Dopamine?
inhibits prolactin secretion
91
D1 receptors
activate adenylate cyclase via a Gs protein
92
D2 receptors
inhibit adenylate cyclase via a Gi protein
93
Serotonin is formed from
tryptophan
94
which neurotransmitter is converted to melatonin in the pineal gland?
serotonin
95
What is the most prevalent excitatory neurotransmitter in the brain?
glutamate
96
GABA is an excitatory or inhibitory neurontrasmitter
inhibitory neurotransmitter
97
GABA is synthesized from
glutamate by glutamate decarboxylase
98
What receptors is the site of action of benzodiazepines and barbiturates?
GABAb receptor **increases Cl conductance
99
Glycine is an excitatory or inhibitory neurotransmitter?
inhibitory
100
Nitric oxide is an excitatory or inhibitory neurotransmitter?
inhibitory in GIT, blood vessels and CNS
101
Nitric oxide is synthesized where?
presynaptic nerve terminals, where NO synthase converts arginine to citrulline and NO
102
Sarcomeres are made up of
interdigitating thick and thin filaments arranged longitudinally
103
What accounts for the unique banding pattern in striated muscle?
repeating units of sarcomeres **sarcomere runs from Z line to Zline
104
What are thick muscle filaments made up of?
-present in A band in teh center of the sarcomere -contains myosin
105
Each myosin is amade up of two heads attached to a single tail, what is the job of the mysoin heads?
the myosin heads bind aTP and actin and are involved in cross-bridge formation
106
Describe thin muscle filaments
-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
What is the function of troponin in skeletal muscle?
regulatory protein that permits cross-bridge formation when it binds Ca
108
Function of Troponin T
T-for tropomyosin -attaches the troponin complex to tropomyosin
109
Function of Troponin I
-I for inhibition -inhibits the interaction of actin and myosin
110
Function of Troponin C
-C for Ca -is the Ca binding protein that, when bound to Ca, permits the interaction of actin and myosin
111
Describes T tubules
-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
SR is the internal tubular structures that is the site of:
Ca storage and release for excitation and contraction coupling
113
Describe the function of Ca-ATPase (Ca pump) function in the SR
transports Ca from intracellular fluid into the SR interior, keeping intracellular Ca low
114
What structure in the skeletal muscle contains ryanodine receptor?
SR
115
What is the ryanodine receptor?
contains a Ca release channel
116
Ca in the SR is bound loosely to
Calsequestrin
117
What are the steps in excitation-contraction coupling in skeletal muscle?
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
What is the mechanism of tetanus?
-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
What type of muscle does not have sarcomeres?
-thick and thin filaments that are not arranged in sarcomeres **appears more homogenous rather than striated
120
What are examples of multiunit smooth muscle throughout the body?
-iris, ciliary mm of the lens and vas deferens
121
How does multiunit smooth muscle function?
-behaves as separate motor units -has little or no electrical coupling between cells -densely innerves; contraction is controlled by neural innervation
122
What are examples of unitary (single-unit) smooth muscle?
-uterus, gastrointestinal tract, ureter & bladder
123
How does unitary (single-unit) smooth muscle function?
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
Vascular smooth muscle has properties of
both multiunit and single-unit smooth muscle
125
What makes the mechanism of excitation-contraction coupling is different fromt hat in skeletal muscle
**there is no troponin; instead, Ca regulates myosin on the thick filaments
126
What are the steps in the contraction of smooth muscle
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
Describe the differences in excitation- contraction coupling between skeletal mm, smooth mm and cardiac muscle?
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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