Exam I Flashcards
(167 cards)
1
Q
Intracellular fluid-
A
The fluid found with in the cell, composing most of the cytoplasm
2
Q
Extracellular fluid
A
Fluid found outside cells, maintaining cell elasticity and moisture externally
3
Q
Plasma
A
The fluid within the vessels of the body
4
Q
Interstitial fluid
A
The fluid found outside of cells in the body, often serving to transport nutrients and signals between cells
5
Q
Which fluid is described by each statement?
The major cation is Na+,
the major anions are Cl- and HCO3-
and there are a lot of proteins.
A
Plasma
6
Q
Which fluid is described by each statement?
The major cation is Na+
the major anions are Cl- and HCO3-
and there are no proteins.
A
Interstitial fluid
7
Q
Which fluid is described by each statement?
The major cations are K+
and the major anions are proteins and organic phosphates (low Na+ and Cl-)
A
Intracellular fluid
8
Q
Which types of solutes can move through the phospholipid bilayer?
Do these move from high
concentration to low concentration, low to high, or both?
A
Small sometimes charged molecules such as O2 and H+ can move through, while larger molecules like water cannot. These move from high to low concentration either into or out of the cell
9
Q
Is facilitated diffusion a form of active or passive transport?
Which types of solutes can move
via facilitated diffusion?
Which part of the membrane do they move through?
A
Passive transport,
solutes moving down their concentration gradient such as glucose
water, and ions can pass through the membrane with the help of a channel protein.
10
Q
Does each of the following describe active transport, passive transport, or both?
A) Solutes move from high concentrations to low.
A
Passive
11
Q
Does each of the following describe active transport, passive transport, or both?
B) Solutes move from low concentrations to high.
A
Active
12
Q
Does each of the following describe active transport, passive transport, or both?
C) Requires the cell to expend energy.
A
Active
13
Q
Does each of the following describe active transport, passive transport, or both?
D) Solutes move through membrane proteins.
A
Both
14
Q
Briefly describe the difference between channel and carrier proteins.
A
Channel proteins form a gate of forms to allow ions and molecules to enter and exit the cell. Carrier proteins have 2 conformations, one inert and one activated when they bind their molecule of interest.
15
Q
Examples of solutes in cell fluids-
A
Ions (Na+, K+, Ca2+, etc.)
Small molecules
Non-polar (O2, CO2, etc.)
Polar (glucose, amino acids, etc.)
Large, polar molecules (peptides)
16
Q
What are the 2 requirements for membrane transport?
A
Driving force = energy
Pathway = membrane permeability
17
Q
What are the 2 energy sources for membrane transport?
A
Molecular motion
ATP
18
Q
3 types of molecular motion energy-
and what each entails~
A
Concentration gradients-
Solutes distribute equally in space
Electrical gradients-
Charged solutes are repelled by like charges
Electrochemical gradients-
Combination of concentration and electrical gradients
19
Q
Two types of ATP usage for membrane transport:
A
Primary active transport-
ATP used to move solute against its concentration gradient
Secondary active transport-
ATP establishes concentration gradient for one solute
Diffusion of that solute down its concentration gradient moves a second solute against its gradient
(think about the H+ATPase pump in plant phys with glucose)
20
Q
Primary active transport-
(ATP for membrane transport)
A
ATP used to move solute against its concentration gradient
21
Q
Secondary active transport-
(ATP for membrane transport)
A
ATP establishes concentration gradient for one solute
Diffusion of that solute down its concentration gradient moves a second solute against its gradient
22
Q
What are the 2 pathways for membrane transport?
A
1) Lipid bilayer
2) Proteins
23
Q
Channel vs Carrier proteins
A
Channel proteins-
Fast, bidirectional
Leak, gated
Carrier proteins-
Slower, unidirectional
Uniport, symport, antiport
24
Q
What is vesicular transport?
A
Used to move larger molecules
Endocytosis vs. exocytosis
**see 02 slide 11 form week 1 for this chart
25
What type of transport can occur via the lipid bilayer?
lipid bilayer only good for passive transport
26
What is osmosis?
Movement of water from a lower concentration to a higher concentration solution
Water moves through aquaporins
27
What are the 3 steps of cell signaling?
1) Reception (a signal modecule will bind a receptor)
2) Transduction (receptor is activated by binding and changes shape)
3) Response (cell will respond to the given signal)
28
Direct communication allowed through
gap junctions between cells so molecules can be sent without going
through the cell membrane
29
Paracrine signaling allows for
one cell to signal another specific cell, ligands tend to not travel far (localized
signaling)
30
Endocrine signaling allows for
cells to signal to other cells at a far distance
31
Autocrine signaling is when a
cell that secretes certain molecules to cause a response in itself
32
Are hydrophilic signals more likely to bind to intracellular or cell membrane surface receptors?
Hydrophilic signals are most likely to bind to the cell membrane surface receptors,
because they have a difficult time passing through the cell membrane.
33
What are the 4 types of cell membrane surface receptors
1) Ligand-gated Ion channel
2) Voltage-gated ion channel,
3) G-protein linked receptor
4) Enzyme linked receptor
34
What are the 3 main means of indirect cell communication?
1) Paracrines (responding to nearby cells)
2) Hormones (emptied into the blood, longer distance communication signal)
3) Neurotransmitters (signals used by neurons) activate a cell located nearby
35
Which 2 cell signaling molecules are best for local communication?
Paracrines & Neurotransmitters
36
What are the steps of signal transduction?
Signal molecule
binds to
Membrane receptor protein
activates
Intracellular signaling molecule
alter
Target proteins
create
Response
37
How is glucose absorbed by the large intestine?
1) SGLT1 actively transports glucose into epithelial cells, using Na⁺ as a co-transporter.
2) Glucose moves across the epithelial cell cytoplasm.
3) GLUT2 facilitates glucose diffusion into the blood.
4) The Na⁺/K⁺ pump maintains the necessary sodium gradient.
5) Glucose enters the hepatic portal vein and reaches the liver for processing.
38
What is similar about simple and facilitated diffusion?
What makes them different?
Simple diffusion occurs directly through the lipid bilayer.
Facilitated diffusion requires a transport protein (channel or carrier) to help larger or charged molecules cross the membrane.
Both are passive transport
39
What is Signal transduction?
Converting an extracellular signal into an intracellular response
40
What are the 2 categories of signal molecules?
Polar and non-polar
41
Nonpolar
Bind to cytosolic or nuclear receptors
Change gene activity – slow, long lasting
(Some hormones like this, see these activate all the different steps)
42
Polar
Bind to membrane receptors
Change protein activity – fast, short duration
(most hormones are like this)
43
Describe the key differences between polar and non polar signaling molecules
Nonpolar-
Bind to cytosolic or nuclear receptors
Change gene activity – slow, long lasting
Polar-
Bind to membrane receptors
Change protein activity – fast, short duration
44
3 categories of membrane receptors: (in response to a signal molecule)
-receptor-channels
-receptor-enzymes
-G protein-coupled receptors
45
Receptor-channels
changes membrane permeability
46
Receptor-enzymes
protein with extracellular binding site, enzyme that can be turned on or off
47
G protein-coupled receptors
signaling molecule turns on the protein
48
Initiating a response-
What are the 3 main steps?
1) secondary messengers- relay info from receptors to target proteins
2) signal cascade that includes amplification
3) activation of target proteins causes a response
49
What are the 4 categories of cell response?
1) Enzyme regulation
2) Motor protein activation
3) Gene expression changes
4) Membrane protein changes
50
What are some examples of cell response?
Glucose intake by cells, olfaction, and cell division
-can have different receptor proteins that respond in different ways
51
What major factors influence cell response?
1) Signal molecule (ligand)
Agonist vs. antagonist
-primary ligand activates receptor
-agonist also activates
-antagonists blocks receptor activity
2) Receptor
“Same key, different locks”
Up/down-regulation
3) 2nd messenger pathway
52
What's the difference between a signal cascade and a signal amplification?
signal cascade- ensures the proper transmission of signals.
Signal amplification- ensures that a small number of molecules produce a strong and efficient response.
53
What is a signal cascade?
a step-by-step series of molecular interactions that occur after a receptor is activated by a ligand (signaling molecule).
54
What is a signal amplification?
refers to the ability of a signal cascade to magnify the original signal, producing a large cellular response from a small number of signaling molecules
55
What does it means that a neuron has a resting membrane potential?
Neurons have a stable seperation of charges across the membrane, they have a positively charged layer outside the membrane, and a negatively charged layer inside the membrane.
56
What is the charge like on the inside and outside of a neuron membrane?
-positively charged layer outside the membrane
-negatively charged layer inside the membrane
(they sad, positive outside, negative inside)
57
Is the resting membrane potential a positive or negative number?
Negative, ~-70mV
58
Which solutes are found in higher concentration outside the neuron cell?
Cl-, Ca2+ and Na+ are usually found outside
59
Which solutes are found in lower concentration outside the cell?
OA- (organic anions) Na+, K+, and Ca2+ mostly found inside
60
Which solutes are found in higher concentrations inside the cell?
Potassium ions (K⁺)
Proteins
Phosphate ions
Magnesium ions (Mg²⁺) –
Organic molecules
61
What is the membrane potential?
Separation of electrical charge across the cell membrane
Measured in millivolts (mV)
Size depends on # of separated charges
62
What is the Resting membrane potential?
Stable potential of a neuron cell at rest
~ -70mV
63
What influences the resting membrane potential?
Influenced by ion concentration gradients & permeabilities
64
If a cell only had Na+ leak channels, which direction would Na+ move, and how would that affect Vm? (membrane potential)
Sodium ions would likely move into the cell which would cause the resting membrane potential to become more positive (depolarization.)
65
Why isn’t resting Vm equal to EK+?
The resting membrane potential isn’t equal to the potassium equilibrium potential since the membrane is permeable to more than one ion, and the pump enzymes maintain the gradients for each ion.
66
As the cell depolarizes, what would happen to the rate of Na+ and K+ flow across the membrane?
The rate of Na+ ions entering the cell would increase, and the rate of K+ ions leaving the cell would increase.
67
Think of 2 changes in membrane permeability that would cause the cell to depolarize.
If Na+ permeability increased, the cell would be depolarized.
If less K+ ions left the cell, due to permeability decrease, the cell would also be depolarized.
68
Movement of ions across the membrane is dependent on what 2 things?
Electrochemical gradient
Permeability of membrane
69
Membrane potential chart-
see slide 5 of 04
70
How would lowering the concentration of extracellular K+ affect the resting membrane potential?
Lowering the concentration of extracellular K⁺ would make the resting membrane potential (Vm) more negative (i.e., hyperpolarized).
(this is bc the K+ ions are moving out of the cell)
71
Define equilibrium potential
The electrical potential difference across the cell membrane that exactly balances the concentration gradient for an ion
(resulting in no net movement of that ion across the membrane)
72
Define electrochemical gradient
a gradient of electrochemical potential, usually for an ion that can move across a membrane
73
Take a minute to draw and label a neuron
slayy, I have a screenshot for u for reference
74
For an action potential, what does threshold mean?
~-50mV
the level of membrane depolarization that must be achieved before an action potential can be initiated.
75
What are the main parts of a neuron?
1) Cell body (soma)
Serves basic metabolic needs
2) Dendrites
Receive incoming signals
3) Axon
Conducts action potentials
4) Myelin sheath
5) Nodes of ranvier
6) axon terminal
76
What are the stages of membrane potential changes?
-depolarization- gets more positive
Repolarization- gets more negative towards -70
-hyperpolarization more neg than -70
77
What direction does the electrical gradient pull Na+ and K+?
Both inward bc neg af inside the neuron
78
Gradient wise, what direction are Na+ and K+ pulled?
K+ gradient favors outward movement
Na+ gradient favors inward
79
What will dictate the duration and amplitude of a graded potential?
Amplitude/duration depend on stimulus amplitude/duration
80
Which type of potential experiences decremental spead?
Graded potential
(the decrease in amplitude of a signal as it moves over distance)
81
Are graded potentials depolarizing or hyperpolarizing?
Can be either
82
What is a graded potential?
a small, localized change in membrane potential that occurs in response to a stimulus.
(It can either depolarize or hyperpolarize the membrane.)
83
Describe the propagation and summation of graded potentials
Propagation: Decreases in strength as it spreads from the point of origin (decremental conduction).
Summation: Can be summed (multiple graded potentials can combine to bring the membrane to threshold or cancel each other out).
84
What is an action potential?
An action potential is a rapid, large depolarization that propagates along the axon of a neuron.
It is an all-or-nothing response
85
If the threshold is not met, will a smaller action potential still occur?
No, it is an all-or-nothing response
86
Where do graded potentials usually occur, and where do actions potentials usually occur?
Graded potentials-
usually occurs in the dendrites or cell body of a neuron
Action potentials- propagates along axon
87
What dictates the amplitude of an action potential?
Nothing, Always the same size (~100 mV, from ~ -70 mV to +30 mV), regardless of stimulus strength (as long as the threshold is reached)
88
Are action potentials depolarizing or hyperpolarizing?
Always depolarizing, followed by repolarization and often a short hyperpolarization
89
Can multiple action potentials build to a bigger response?
No
90
What direction does flow occur in in a neuron?
-One way direction flow starts in dendrite then zips to axon and axon terminals
91
Will an action potential lose energy through propagation, and can another potential begin shortly after one had occured?
Propagation: Does not decrease in strength; self-propagates down the axon.
NO- a new action potential cannot begin until the refractory period is over.
92
Why does an action potential not lose energy as it travels down the axon when a graded potential will?
self-propagates down the axon
93
After an action potential has occured, when can another occur?
once the refractory period is over.
94
Describe the directionality of graded vs action potentials
-graded potentials go in all directions, action potentials only go in one direction
95
What is a common cause of hyperpolarization? (gettin more neg)
K+ leaving the cell
96
What is a common cause of depolarization? (gettin' more positive)
Na+ entering the cell
97
What is the deep down connection between graded potentials and action potentials?
Graded potentials determine whether a neuron will reach threshold and generate an action potential.
If enough excitatory graded potentials summate and bring the membrane to threshold, an action potential will fire.
98
Which potential is dependent on the amplitude and duration of the stimulus?
Graded potentials,
NOT action potentials, they either do or dont no variance
99
Why is the trigger zone important to understanding action potentials?
-either get one or don’t, need threshold to be met at trigger zone, doesn't matter if happens at some other spot in cell
-Basically an action potential can only occur from a trigger zone, and that zone needs to reach the threshold through graded potentials
100
In regard to action potentials, what is the difference between Na+ channels and K+ channels?
K+ channels can pinch closed but wont lock
Na+ channels can pinch closed or lock.
101
Describe the state of the voltage-gated Na+ channels during each phase of an action potental
Resting membrane potential- closed but can open
Depolarization- open
Repolarization- closed and locked, cannot open (K+ channels begin to open)
Hyperpolarization- closed but now reset and could open for new action potential
102
What is the refractory period vs the repolarization after an action potential?
The refractory period is the time it takes for a cell to recover after an action potential
Repolarization is the phase of the action potential when the cell returns to its resting state.
103
What role do opening and closing the Na+ gates and K+ gates have during an action potential
Na+ gates open during the depolarizing phase
K+ gates open during the repolarizing phase (they exit the cell causing it to become more neg)
104
What actions will generate an action potential?
Often opening of Na+ channels, causing depolarization
105
What causes an action potential?
-a strong enough electrical signal reaching the neuron causes the sodium channels to open
-leads to a rapid change in membrane potential and the generation of an action potential.
106
Na+/K+ pump
when will it be doin during action potentials
kicks out Na+ brings in K+
-makes membrane more negative
107
Are our ion concentrations changing during or after an action potential?
No, movement not enough to change concentration gradient
(think picking up sand grains on the beach)
108
Does it take movement of a lot of ions to generate a big electrical signal?
No
109
True or false: After an action potential, Na & K concentration gradients are reversed and need to be restored by the Na/K pump.
False
110
True or false: At the end of an action potential, the resting membrane potential is restored by the Na/K pump.
False
111
What effect does the Na/K pump have on the membrane potential?
Actively maintains a negative membrane potential by pumping three sodium ions (Na+) out of the cell for every two potassium ions (K+) it pumps in
112
The Refractory period-
which 2 are there
Absolute
-Na+ channels open or inactive
-additional Aps cant occur
Relative
-Na+ channels resting form inactive state to closed but ready to open
-additional Aps smaller
-Larger stimulus needed to reach threshold
113
During the relative refractory period, why would the action potential be smaller than normal and require a stronger stimulus?
The action potential would need a stronger stimulus because the membrane potential will be more negative, requiring a larger gap to be spanned.
The action potential would
likely be smaller because less sodium will be entering the cell due to there not being
enough open sodium channels.
114
What are the mechanisms that can be behind action potentials?
1) Local current flow
Graded potential that depolarizes adjacent section of axon
2) APs propagate down axon
One way conduction
No change in size
115
Local current flow, what is?
(think ions moving somewhere when you hear current)
-graded potential that depolarizes adjacent section of axon
116
APs propagate down axon via what mechanism
-one way conduction
-no change in size
-kind of like dominos toppling each other over
-depolarize next section, causing action potential to be regenerated
idk pretend to understand
117
If local current flows in both directions, why is the action potential only conducted in one direction?
Even though local currents (the movement of ions in and out of the membrane) spread in both directions, the action potential only moves forward because of the refractory period of voltage-gated sodium (Na⁺) channels
118
What would you expect to happen if we artificially started an action potential midway down the axon?
If an action potential is artificially triggered in the middle of the axon (e.g., by electrical stimulation), it would propagate in both directions
119
Synaptic transmission is __________ meaning_______
one-way, meaning signals only go from pre- to postsynaptic neurons
120
Saltatory conduction is what
a process by which electrical impulses (action potentials) rapidly propagate along myelinated axons
121
Saltatory conduction is made possible by what 2 components of the axon?
Myelin- insulating lipid sheath around axon (not continuous)
Nodes of Ranvier: breaks in myelin sheath
122
What is the insulating lipid sheath around axon (not continuous)
Myelin
123
What are the breaks in the myelin sheath
Nodes of Ranvier
124
Nodes of Ranvier, what do they do? Why helpful?
-cell membrane is a lil leaky, some charge will be lost across membrane
-need graded potential, need to regenerate action potential (all the way down along the axon)
-nodes pots where the action potential is gonna be regenerated
125
Are myelinated axons faster or slower?
-myelinated axon faster
126
Why is myelin helpful?
-reduces leakage of ions (myelin) so can travel further, then time taken to regenerate charge
127
What factors effect Action potential conductance?
1) Myelin: insulating lipid sheath around axon
2) Nodes of Ranvier
3) Diameter
128
Why is diameter helpful to action potential conductance?
-big diameter less resistance to flow, easier for sodium ions to flow and depolarize next section
-axon diameter affects resistance to local current flow
129
Why is it advantageous to have myelinated axons vs just thickening the diameter?
-myelin advantage bc pack axons together, have more, bigger brain with more power
-invertebrates can only make bigger diameter
130
Who is our main big model axon?
-squid giant axon allowed for a lotta discoveries so that’s cool
131
What main 4 components that synapses use to communicate with each other?
1) Presynaptic cell
2) Postsynaptic cell
3) Synaptic cleft
4) Neurotransmitters
132
What triggers the release of neurotransmitters?
Voltage-gated Ca2+ channels open, triggers
release of neurotransmitters from synaptic vesicles
133
The idea of neuronal signaling is essentially
they need to take an electrical signal, convert to chemical signal that can then electrical signal to another neuron
134
When an action potential spreads to terminals, will change the Ca2+ gates to being open. What next?
(concentration of Ca2+ is higher in ECF, so calcium rushes in)
-calcium will enter the axon terminal
-activate some synaptic vesicles to move towards the membrane
135
How will some synaptic vesicles open?
-some will fuse with plasma membrane causing exocytosis and release into synaptic cleft
-others will just open inside the cell and diffuse out
136
Postsynaptic cell-
composed of who?
Postsynaptic receptors
Chemically-gated ion channels
Postsynaptic potentials
Excitatory (EPSPs)
Inhibitory (IPSPs)
137
What are postsynaptic receptors
a protein on the receiving end of a synapse that detects neurotransmitters and causes ion channels to open or close
(Chemically-gated ion channels)
138
What are the two postsynaptic potentials?
Excitatory (EPSPs)
Inhibitory (IPSPs)
139
How do post synaptic receptors work
-membrane bound proteins ligand gated ion channels
-can be closed when no neurotransmitter molecule, open up when neurotransmitter appears
-channels could be open and then close with neurotransmitters
-will change the membrane permeability, changing the membrane potentials
140
What kinds of postsynaptic receptors would cause EPSPs? What about IPSPs?
idk man
141
Excitatory (EPSPs), do what
Will bring closer to threshold to fire an action potential
142
Inhibitory (IPSPs) do what
Hyperpolarizing, less likely cell will activate
143
What are the three (but secretly kinda two) ways to stop synaptic transmission?
1) Reuptake
2) Enzymatic inactivation
3) Diffusion
144
Examples of permeability changes that could lead to EPSPs
When neurotransmitter binding increases permeability to cations (Na⁺ or Ca²⁺) or decreases K⁺ permeability.
(makes sense bc depolarizing membrane)
145
What do EPSPs do to the likelihood of an action potential?
EPSPs increase the likelihood of an action potential by depolarizing the postsynaptic membrane.
146
What do IPSPs do to the likelihood of an action potential?
IPSPs decrease the likelihood of an action potential by hyperpolarizing the postsynaptic membrane.
147
Examples of permeability changes that could lead to IPSPs
This happens when neurotransmitter binding increases permeability to Cl⁻ (influx) or K⁺ (efflux).
(makes sense bc hyperpolarization)
148
Describe the difference between chemical and electrical synapses
A chemical synapse has a gap between the axon terminal and the target cell. An electrical synapse is physically connected with the membrane of the target cell.
(most are chemical)
149
What part of a neuron can receive incoming info?
via synapses on dendrites
150
Synaptic cleft what is
The space between an axon terminal and a target cell for a chemical synapse.
151
What is the presynaptic membrane?
The membrane on the axon terminal facing the target cell for chemical synapse.
152
What is the post-synaptic membrane?
The membrane on the target cell facing the axon terminal for chemical synapse.
153
Synaptic vesicle-
Pockets inside the presynaptic membrane of the neuron
154
Neurotransmitter-
A molecule that acts to send nervous signals to target cells.
155
Postsynaptic receptor
Receptors on the postsynaptic membrane of the target cell with a chemical synapse
156
Which ion comes into the axon terminal to cause neurotransmitter release?
Ca2+ ions
157
what happens when a neurotransmitter binds to a postsynaptic receptor
A change will be initiated within the cell. Some cause ligand gated ion channels will open causing changes in membrane potential, or second messenger systems may
become activated
158
What are the 3 ways a neurotransmitter can be removed from the synaptic cleft?
1) Diffuse away from the synaptic cleft
2) Degradation of the neurotransmitter by an enzyme
3) Reuptake of a neurotransmitter by a transporter protein
159
What are the two primary patterns of connections for neurons?
1) Convergence-
Multiple presynaptic cells synapse with one postsynaptic cell
2) Divergence-
One presynaptic cell synapses with multiple postsynaptic cells
160
Convergence-
Multiple presynaptic cells synapse with one postsynaptic cell
161
Divergence-
One presynaptic cell synapses with multiple postsynaptic cells
162
What are the 2 summations of inputs
1) Temporal summation-
Graded potentials from single presynaptic input combine
2) Spatial summation-
Graded potentials from multiple presynaptic inputs combine
163
Temporal summation-
Graded potentials from single presynaptic input combine
164
Spatial summation-
Graded potentials from multiple presynaptic inputs combine
-comes down to how many presynaptic excitations we have
-(generally send out one neurotransmitter or package of same group)
165
Neural summation is
the process by which multiple signals from neurons are combined to determine if an action potential is generated
166
What would you expect the postsynaptic response to be if we stimulated Ex1, Ex2, and In1 all at the same time?
I would expect that we would not see an action potential. This is because the excitatory and inhibitory will counteract each other.
167
You are recording from postsynaptic cells that all get input from the same presynaptic cell. When the presynaptic cell fires, some but not all of the postsynaptic cells fire. What might be happening?
There may be different types of post synaptic receptors, or there may be different inputs from other cells.
