CELL PHYSIOLOGY Flashcards
1
Q
Composition of Cell membranes
A
Phosphlipids and proteins
2
Q
Lipid Bilayer
A
- Phopholipids
- glycerol backbobe (hydrophilic)
- Fatty acid tails (hydrophobic)
3
Q
Lipid-soluble subtances
A
can cross the cell membrane
- O2
- CO2
- steroid hormones
4
Q
Water soluble substances
A
Cannot dissole in the lipid membranes
- water filled channels
- pores
- carriers
- Na, Cl, glucose, H20
5
Q
Types of Proteins in the Cell membrane
A
- Integral proteins
- anchored, imbedded through hydrophobic interactions
- span the cell membrane
- ion channels, transport proteins, receptors, and GTP binding proteins
- Peripheral proteins
- not imbedded
- not cobalently bound
- loosely attached via ELECTROSTATIC interactions
6
Q
Intercellular junstions in the Cell Membrane
A
-
Tight junctions (zonula occludens)
- between cells (epithelial)
- intercellular pathway
- may be permeable (DCT) or impermeable (PCT)
-
Gap junctions
- permit intercellular communication
- current flow and elctrical coupling between myocardial cells
7
Q
Characteristics of Different Types of Transport across cell membranes
A
- Simple diffusion
- Facilitated Diffusion
- Primary active
- Co transport
- Countertransport
8
Q
Only form of tansport that is not carrier mdiated
occurs down an electrochemical gradient
does not require metabolic energy and therefore is passive
A
Simple Diffusion
9
Q
Formula for Diffusion
A
J = -PA (C1-C2)
- J = flux (flow) mmol/sec
- P = permeability (cm/sec)
- A = Area (cm2)
- C1= concentration (mmol/L)
- C2 = concentraition (mmol/L)
10
Q
Describes the ease with which a solute diffuses through a membrane
Depends on the characteristics of the solute and the membrane
A
Permeability
11
Q
Facors that increases permeablility
A
- Increase oil/water coefficient of the solute increases solubility in the lipid of the membrane
- Decrease radius of the solute increases the diffusion coefficient and speed of diffusion
- Decrease membrane thickness decreases the diffusion distance
12
Q
Includes facilitated diffusion and primary and secondary active transport
A
Carrier mediated transport
13
Q
Characteristics of Carrier mediated transport
A
- Stereospecificity
- Satutration
- the transport maximum (Tm) is analogous to the the maximum velocity (Vmax) in enzyme kinetics
- Competition
14
Q
- Occurs down an electrochemical gradient (“downhill”)
- Does nt require metabolic energy
- more RAPID than simple diffusion
- carrier mediated
A
Facilitated diffusion
15
Q
Occurs against an electrochemical gradient
requires direct inut of metabolic energy in the form of ATP
carrier mediated
A
Primary active transport
16
Q
Examples of Primary active transport
A
- Na, K, ATPase (or Na-K pump)
- 3 Na 2 K
- specific inhibitors:
- cardiac glycosides
- ouabain
- digitalis
- Ca-ATPase (or calcium pump)
- Sarcoplasmic and endoplasmic reticulum
- SERCA
- H, K ATPase (or proton pump)
- gastric parietal cells
- Renal alpha intercalated cells
- Inhibited by PPI
- Omeprazole
17
Q
Concentraion of smotically active particles in a solution
Colligative propert that can bemeasured by freezing point depression
A
Osmolarity
18
Q
The transport of two or more solutes is coupled
One of the solutee (usually Na) is transported downhill and provides energy for the uphill tansport
Metabolic energy is provided INDIRECTLY from the sodium gradient
A
Secondary active transport
- Cotransport/symport = same direction
- Na-glucose cotransport
- Na-K-2Cl
- Countertransport/exchange/antiport = opposite direction
- Na-Ca exchange
- Na-H exchange
19
Q
Flow of water across a semipermeable membrane from a solution with low solute concentrationto a solution with high solute concentration
A
Osmosis
20
Q
OSmotic pressure can be calculated by __________
states that osmotic pressure depends on the concentration of osmotically active particles.
A
van’t Hoff’s law
- g X C X RT
21
Q
The Osmotic Pressure ________ when the solute concentration increses.
A
Increases
- The higher the osmotic pressure of a soultion, the greater the water flow into it
22
Q
The osmotic pressure created by proteins
A
Colloid osmotic pressure or oncotic pressure
23
Q
Number between zero and one that describes the ease with which a solute permeates a membrane
A
Reflection coeficient
- if the reflection coefficient is one, the soulte is impermeable. It creates an osmoti prssure
- albumin
- If the reflection coefficient is zero, the solutie is completely permeable. therefore it will not exert any osmotic effect
- urea
24
Q
osmotic pressure (calculated by van’t Hoff’s law) multiplies by the reflection coefficient
A
Effective osmotic pressure
25
Integral proteins that span the membrane and, when openm permit the passage of certain ions
Ion channels
26
Characteristics of Ion channels
* Selective
* based on the size and the distribution of charges
* May be open or closed
* The conductance of a channel depends on the probability that the channel is open
* the higher the probability that a channel is open the higher the conductance
27
\_\_\_\_\_\_\_ channels are opened or closed by changes in membrane potntial
Voltage gated channels
28
\_\_\_\_\_\_\_\_\_\_\_\_\_channels areopened or closed by hormones, second messengersm or neurotransmitters
Ligand gated channels
* Nicotinic receptors for ACh
* when open ot is permeable tto Na and K, causeing motor end plates to depolarize
29
the potential difference generated across a membrane because of a concentraion difference of an ion
created by the diffusion of very few ions and therefore, do not result in changes in concentration of the diffusion ions
Diffusion potential
* Size of the diffusion potential
* depends on the size of the concentration gradient
* whether the diffusing ion is positively or negatively charged
30
the potential differencethat woul exactly balance (oppose) the tendency for diffusion down a concentration difference
Equilibrium Potential
31
used to calculate the equilibrium potential at a given concentration difference of a permeable ion across a cell membrane
Nernst equation
32
the difference between the actual membrane potential (Em) and the ion's equilibrium poential (calcualted with the Nernst equation)
Driving force
33
Occurs if there is a driving force on the ion and the membrane is permeable to the ion.
Current flow
* The direction of current flow is in teh same directioon as the driving force
* The magnitude of current flow is determined by the size of the size of the driving force and the permeability
34
expressed as the measured potential difference across the cell membrane in millivolts (mV)
by convention, expressed as the intracellular potential relative to the extracellular potential.
Resting membrane potential
* established by diffusion potentials
* The Na-K pump contributes only indirectly to the resting membrane potential by maintaning across the cell membrane, the Na and K concentration gradients that then produce diffusion potentials
* The electrogenic contribution of the pump (3 Na pumped out of the cell for every 2K pumped into the cell) is small
35
makes the membrane potential **less negative** (the cell interior becomes less negative)
Depolarization
36
Makes the membrane potential **more negative** (the cell interior becomes more negative)
Hyperpolarization
37
The flow of positive charge into the cell, Inward current **depolarizes** the membrane potential
Inward current
38
The flow of positive charge out of the cell.
Outward current
39
Property of excitable cells that consists of arapid depolarization, or upstroke, followed by repolarization of the membrane potential
Action potential
* have stereotypical size and shape
* propagating
* all or none
40
membrane potential at which the acton potential is inevitable.
Threshold
* At threshold potential, net inward current becomes larger than the net outward current
* The resulting depolarization becomes self sustaining and gives rise to the upstroke of the action potential
41
Resting membrane potential of nerves
* -70 mV, cell negative
* result of the high resting conducatnce to K+
* At rest, although the inactivation gates on sodium channels are open, the activation gates on sodium channels are closed and thus the sodium channels are closed and sodium conductance is low
42
Upstroke of the nerve action potential
1. Inward current deplarizes the membrane potentia threshold
2. Depolarization causes rapid opening of the activation gates of the sodium channels
3. The sodium conductance becomes higher than the K conductance, and the membrane potential is driven toward th soium quilibrium potential. **UPSTROKE IS CAUSED BY INWARD SODIUM CURRENT**
4. The overshoot is a brie portion at the peak of the action potential
5. Tetrodotoxin and lidocaine blocks these voltage gated sodium channels and abolish action potential
43
Repolarization of nerve action potential
* Depolariation also close the inactivation gates of Na channels
* Depolarization slowly opens K channe;s and increases potassium conductance. Tetraethylammonium blocks these voldatge gated K channels
* **OUTWARD REPOLARIZATION IS CAUSED BY AN OUTWARD POTASSIUM CURRENT**
44
period during which another action potential cannot be elicited no matter how large the stimulus
Coincides with almost the entire duration of the action potential
Absolute refractory period
* the inactivation gates of sodium channels are closed when the membrane potential is depolarized. They remain closed until repolarization occurs.
45
Beigns at the end of the absolute refractory period and continues until the membrane potential returns to the resting level
An action potential can be elicitd during this period only if a larger than usual inward current is provided
Relative refractory period
* The K conductance is higher than at rest, and the membrane potential is closer to the K equilibrium potential and therefore, ferther from threshold; more inward current is required to bring the membrane to threshold
46
Occurs when the cell membrane is held at a depolarized level such that the threshold potential is passed without firing an action potential
occurs because depolarization closes inactivation gates on the sodium channels
Accomodation
* demonstrated in **hyperkalema**, in whcih skelatal muscle membranes are depolarized by the high serum K concentration. Although the membrane potential is closer to threshold, action potentials do not occur because inactivation gates on sodium channels are closed by depolarization causing muscle weakness
47
occurs by the spread of local currents to adjacent areas of membrane, which are then depolarized to threshold and generate action potentials
propagation of action potentials
48
Condction velocity is increased by \_\_\_\_\_\_
* Increase in fiber size
* this will decrase internal resistance; thus, conduction velocity down the nerve is faster
* Myelination
* acts as an insulator around the nerve axons and incrases conduction velocity
49
Myelinated nerves exhibit __________ conduction
50
Saltatory conduction
* action potentials can be generated only at the nodes of ranvier, where there are gaps in the myelin sheath
51
Nerve action potential and ssociated changes in sodium and potassium
52
General Characteristics of Chemical Syanpses
* An action potential in the presynaptic cell causes depolarization of the presynaptic terminal
* as a result of the depolarization
* **Calicium enters the presynaptic terminal causing release of neurotransmitter into the synaptic cleft**
* Neurotansmitter diffuses across the synaptic cleft and combines with **receptors on the postsynaptic cell membrane**, causing a change in its permeability to ions and, consequently, a change in its membrane potential
* **Inhibitory neurotransmitters** hyperpolarizr the postsynaptic membrane
* **excitatory neurotransmitters** depolarizee the postsnaptic membrane
53
Hyperpolarize the postsynaptic membrane
Inhibitory neurotransmitters
54
depolarize the postsynaptic membrane
Excitatory neurotransmitters
55
Neuromuscular junctions
1. Synthesis and storage of ACh in the presynaptic terminal
2. Depolarization of the presynaptic terminal and calcium uptake
3. Calcium uptake causes release of ACh into the synaptic cleft
4. Diffusion of ACh to the postsynaptic membrane (muscle end plate) and binding of ACh to nicotinic receptors
5. End plate potential in the postsynaptic membrane
6. Depolarization of adjacent muscle membrane to threshold
7. Degradation of ACh
56
catalyzes the formation of ACh from acetyl coenzyme A and choline in the presynaptic terminal
Choline acetyltransferase
57
ACh is stored in ___________ with ATP and proteoglycan for later release
syanptic vesicles
58
Depolarization of the presynaptic terminal opens _____ channels
Calcium
59
The synaptic vesicles fuse with the plasma membrane and empty their contents into the cleft by \_\_\_\_\_\_\_\_\_\_
Exoctosis
60
the nicotinic ACh receptor is also a \_\_\_\_\_\_\_
Na and K ion channel
* binding of ACh to alphaa subunits of the receptor causes a conformational change thatopens the central core of the channel and increases its conductance to Na and K
* Ligand gated channels
61
the contents of one synaptic vesicle (one quantum) produce a \_\_\_\_\_\_\_\_\_\_\_\_\_(MEEP), the smallest possible EPP
Miniature end plate potential
62
The EPP is tansient because ACh is degraded to acetyl CoA and choline by ________ on the muscle end plate
acetylcholinesterase
63
Drug that block the degradation of ACh, prolong its action at the muscle end plate, and increase he size of the EPP
Neostigmine
64
Blocks choline reuptake and depletes the presynaptic endings of ACh stores
Hemicholinium
65
Caused by the presence of antibodies to the ACh receptor,
Characterized by skeletal muscle weakness and fatigability resulting from a reduced number of ACh receptors on the muscle end plate
The size of EPP is reduced; therefore it is more difficult to depolarize the muscle membrane to threshold and to produce action potentials
Myasthenia gravis
66
treatment for myasthenia gravis
neostigine
67
Blocks release of ACh from presynaptic terminals
total blockade of the neuromuscular transmission
Botulinum toxin
68
Prolongs and enhancesaction of ACh at muscle end plate
Neostigmine
69
Depletes ACh stores from presynaptic terminal
Hemicholinium
70
Typees of arrangements of synaptic transmission
* One to one synapses
* neuromuscular junction
* Many to one synapses
* spinal motorneurons
71
are inputs that depolarize the postsynaptic cell, bringing it closer to threshold and closer to firing an action potential
caused by opening of cchannels that are permeable to sodium and potssium
Excitatory postsynaptic potentials (EPSPs)
* Excitatory neurotransmitters include ACh, norepinephrine, epinephrine, dopamine, glutamate, and serotonin
72
inputs that hyperpolarie the postsynaptic cell, moving it away from the threshold and farther from firing an action potential
caused by opening Cl channels
Inhibitory postsynaptic potentials (IPSPs)
* Inhibitory neurotransmitters are **GABA** and **glycine**
73
occurs when two excitatory inputs arrive at a postsynaptic neuron simultaneosly
Spatial summation
74
Occurs when two excitatory inouts arrive at a postsynaptic neuron in rapid succession. Because the resulting postsynaptic depolarizaations overlap in time, they add in stepwise fashion
Temporal summations
75
occur after tatanic stimulation of the presynaptic neuron. In each of these, depolarization of the postsynaptic neuron is greater than expected because greater than the normal amounts of neurotransmitter are released, possibly beacuse of the accumulation of calcium in the presynaptic terminal
Facilitation, augmentation, and posttetanic potentiation
* Long-term potentiation (memory) involves new protein synthesis
76
Primary transmitter released from postganglionic sympathetic neurons
synthesized in the nerve terminal and released into the synapse to bind with alpha or beta receptors in the postsynaptic membrane
removed from the synapse by reuptake or is metabolized in the presynaptic terminal by monoamine oxidase (MAO) and catechol-O-methyltransferase
Norepinephrine
77
The metabolites of norepinephrine
* 3,4 dihydroxymandelic acid (DOMA)
* Normetanephrine (NMN)
* 3-methoxy-4-hyddroxyphenylglycol (MOPEG)
* 3-methoxy-4-hydroxymandelic acid or vanilylmandelic acid (VMA)
78
Tumor of the adrenal medulla that secretes ccatecholamines, urinary excretion of VMA is increased
Pheochromocytoma`
79
synthesized from the norepinephrine by the action of phenylethanolamine-N-methyltransferase in the adrenal medulla
a methyl group is transferred to NE fro, S-adenosylmethionine
Epinephrine
80
Dopamine is prominent in ______ neurons
Midbrain
81
Inhibits prolacctin secretion
dopamine
82
Dopamine is metabolized by \_\_\_\_\_\_
MAO and COMT
* D1 reeptors activate adenylate cyclase via Gs protein
* D2 receptors inhibit adenylate cyclase via Gi protein
83
Involves degeneration of dopaminergic neurons that use D2 receptors
Parkinson disease
84
Involves increased levels of D2 receptors
Schizophrenia
85
Present high concentrations in the brain stem
formed from tryptophan
converted to melatonin in the pineal gland
Serotonin
86
Formed from histidine
present in the neurons of the hypothalamus
Histamine
87
most prevalent excitatory neutrotransmitter in the brain
Glutamate
88
How many suntypes of glutamate receptors?
4
89
inhibitory neurotranmitter
synthesized from glutamate by glutamate decarboxylase
GABA
90
How many types of GABA receptors?
2
* GABAA - increases Cl conductance and is the siteof action of benzodiazepines and barbiturates
* GABAB - Increases K conductance
91
inhibitory neurotransmitter found primarily in the spinal cord and brain stem
increases Cl conductance
Glycine
92
short acting inhibitory neurotransmitter in the gastrointestinal tract, blood vessels, and CNS
Syntheisized in the presynaptic nerve terminals, where NO synthase converts arginine to citrulline and NO
Nitric oxide
* also fucntions in signal transduction of guanylyl cyclase in a variety of tissues, including vascular smooth muscle
93
Each muscle fiber is multinucleare and behaves as a signle unit. It contains bundles of \_\_\_a\_\_\_\_, surrounde by \_\_\_\_b\_\_\_\_ and invaginated by \_\_\_\_\_\_c\_\_\_\_\_
a. myofibrils
b. SR
c. transverse tubules
94
A sarcomere runs from \_\_\_\_\_\_\_\_
Z line to z line
95
Present in the A band in the center of the sarcomere
Thick filaments
| (contains myosin)
96
Myosin has 6 polypeptide chains, including one pair of \_\_\_\_a\_\_\_ and 2 pairs of\_\_\_\_\_b\_\_\_\_\_
a. heavy chains
B. light chains
97
Anchored at the Z lines
Present in the I bands
Thin filaments
| (contains actin,myosin, and troponin)
98
Regulatory protein that permits cross-bridge formation wen it binds calcium
Troponin
99
Atacches the troponin complex to tropomyosin
troponin T
100
Inhibits the interaction of actin and myosin
troponin I
101
Calcum binding protein that, when bound to calcium, permits the interaction of actin and myosin
troponin C
102
extensive tubular networks, open to the extracellular space, that carry the depolarization from the sarcolemmal membrane to the cell interior
T tubules
103
T tubules are located in the \_\_\_\_band and ____ Band
A and I
104
T tubules contain a coltage sensitive protein called\_\_\_\_\_
Dihydropyridine receptor
105
Is the internal tubular structure that is the site of calcium storae and release for excitation-contraction coupling
SR
106
SR has ______ that make intimate contact wit the t tubules in a triad arrangement
terminal cisternae
107
Steps in excitation-contraction coupling in skeletal muscle
1. action potential in muscle membrane
2. depolarization of T tubules
3. Opens calcium release channels in SR
4. Increase intracellular calcium
5. Calcium binds to troponin C
6. Cross-bridge cycling
7. Ca reaccumulated by SR
8. Relaxation
108
measured when length is held constant.
Isometric contractions
* Muscle length (preload) is fixed, the muscle is stimulated to contract, adn the developed tension is measured.
* No shortening
109
Measured when the load is held constant
Isotonic contractions
* The load against which the uscle contracts (afterload) isfixed
* Shorteninf is measured
110
in lenth tension relationship. It emasures tension developed during _____________ when the muscle is set to fixed lengths
isometric contractions
111
tension developed by stretching the muscle to different lengths
Passive tension
112
Tension developed when the muscle is stimulated to conract at different lengths
Total tension
113
The difference between total tension and passive tension
Active tension
114
Active tension is proportional to the \_\_\_\_\_\_
number of cross bridges formed
115
Fore velocity relationship measures the velocity of shortening of )\_\_\_\_\_\_\_ when the muscle is challenged with different afterload (the load against which the muscle contract)
isotonic contractions
116
The velocity of shortening _________ ad the afterload increases
Decreases
117
has thick and thin filaments that are not arranged in sarcomeres; therefore they appear homogenous rather than striated
Smooth muscle
118
Type of SM that is present in the iris, ciiary uscle of the lens, and vas deferens
they behave as separate motor untis
has little or no electrical coupling between cells
densely innervated
Multiunit smooth muscle
119
The most common type of SM and is present in the uterus, GI tract, Ureter and bladder
Unitary SM
120
spontaneously active (xhibit slow waves) and exhibits pacemake activity
Unittary smooth muscle
121
has properties of both multiunit and single unit smooth muscle
Vascular smooth muscle
122
Steps in excitation-contraction couping in smooth muscle
123
Comparison of Skeletal, smooth, and cardiac muscles
124
Excitation-contracton coupling of \_\_\_\_\_\_\_
* Action potential -\> T tubules
* Calcium released form nearby SR
* increase intracellular calcium
Skeletal muscle
125
Excitation-contracton coupling of \_\_\_\_\_\_\_
* Action potential opens voltage gated calcium channels in cell membrane
* hormones and transmitters open IP3-gated calcium channels in SR
Smooth muscle
126
Excitation-contracton coupling of \_\_\_\_\_\_\_
* Inward calcium current during plateau of action potential
* Calcium induced calcium release from SR
* increase Calcium concentration
Cardiac muscles
127
Molecular basis for contraction of \_\_\_\_\_\_\_\_\_
* Calcium-troponin C
Skeletal and cardiac muscle
128
Molecular basis for ccontraction of\_\_\_\_
* Calcium-calmodulin increases myosin light chain kinase
Smooth muscle
