Midterm #1 Flashcards
(287 cards)
1
Q
What is the definition of physiology?
A
The study of the normal functioning of a living organism and its component parts, including its chemical and physical processes
2
Q
How is physiology an integrative science?
A
It states that the structure of a cell, tissue, or organ must provide a physical base for its function
3
Q
What are cells?
A
Smallest unit of structure capable of carrying out life processes
4
Q
What is a tissue?
A
Collection of cells carrying out related functions
5
Q
What is an organ?
A
Formation of tissues into a structural and functional unit
6
Q
What is an organ system?
A
integrated groups of organs
7
Q
What are emergent properties?
A
Properties of a complex system that cannot be explained by a knowledge of a system’s individual components
8
Q
What is the difference between the function and the mechanism?
A
Function: why
Mechanism: how
9
Q
What is the definition of homeostasis?
A
The ability to maintain a relatively stable internal environment despite exposure to external variability
10
Q
What are some examples of external changes that can be considered threats to homeostasis?
A
Toxic chemicals, physical trauma, foreign invaders
11
Q
What are some examples of internal changes that can be considered threats to homeostasis?
A
Abnormal cell growth, autoimmune disorders, genetic disorders
12
Q
What is the proper term for someone who is ill or diseases?
A
They are in a pathophysiological state
13
Q
What is the Extracellular fluid (ECF)?
A
Is a buffer between cells and the external environment
14
Q
What is the law of Mass Balance?
A
If the amount of a substance in the body is the remain constant, any gain must be offset by an equal loss
15
Q
The body compartments are in a dynamic steady state, but are not in equilibrium, but rather a _____ ________.
A
stable disequilibrium
16
Q
Regulated variables are kept within a normal range by what?
A
control mechanisms
17
Q
Control systems can be i._____ or ii.______
A
i. local, smaller, and more specific
ii. reflex, widespread
18
Q
Describe local control
A
It is restricted to the tissues or cells involved
19
Q
Reflex control uses what kind of signalling?
A
Long-distance
20
Q
Reflex control refers to any long-distance pathway that uses the ____ system, the _____ system, or both
A
nervous, endocrine
21
Q
Reflex control is broken down into two parts: 1 and 2
A
- Response loop
- Feedback loop
22
Q
What is the purpose of the response loop?
A
Its only job is to sense the cell
23
Q
What is the purpose of the feedback loop?
A
Response alters the initial stimulus. It modulates the response loop and feeds back to ultimately influence the input
24
Q
What are the 7 components of the feedback loop?
A
- Stimulus
- Sensor
- Input signal
- Integrating center
- Output signal
- Target
- Response
25
Describe a negative feedback loop
A pathway in which the response opposes/removes the stimulus signal
26
True or False: negative feedback loops destabilize a system?
False
27
True or False: are negative feedback loops homeostatic?
True
28
Negative feedback loops can restore the ____ ____ but cannot prevent the ____ _____
initial state, initial disturbance
29
What is a common example of a negative feedback loop?
Blood-glucose concentration
30
Describe positive feedback loops
They reinforce a stimulus to drive the systems away from a normal value rather than decreasing/removing it
31
True or False: positive feedback loops are homeostatic?
False
32
How do you stop a positive feedback loop?
It requires intervention, or an event outside the loop to cease the response
33
What is one of the few examples of a positive feedback loop?
Childbirth
34
What is feedforward control?
Reflexes that have evolved that allow the body to predict a change is about to occur
35
What are biorhythms?
variables that change predictable and create repeating patterns or cycles of changes
36
What are the 4 functions of a cell membrane?
1. Physical isolation
2. Regulation of exchange with the environment
3. Communication between the cell and its environment
4. Structural support
37
What is the average composition of a cellular membrane?
~55% proteins
~45% lipids
~small amount of carbohydrate
38
In general, the more _____ _____ the membrane is, the more _____ it contains
metabolically active, proteins
39
What are the three types of lipids found in the cell membrane?
Phospholipid, sphingolipid, and cholesterol
40
Out of the three lipids found in the cell membrane, which is the primary, secondary, and tertiary lipid?
Primary - phospholipid
Secondary - sphingolipid
Tertiary - cholesterol
41
When placed in aqueous solution phospholipids orient themselves so hydrophilic head interacts with water molecules and hydrophobic tails hide. What is the "sheet," the "droplet," "and the "aqueous center" called respectively?
Sheet: phospholipid bilayer
Droplet: micelle
Aqueous center: liposome
42
Describe phospholipids
They are the major lipid
43
Describe sphingolipids
Lipid rafts, specialized regions of the membrane
44
Describe cholesterol
Positioned between phospholipid heads to add viscosity and help make the membrane impermeable to small water-soluble molecules. Glycoproteins and glycolipids are carbohydrates
45
What is the fluid mosaic model?
Where proteins are dispersed throughout, and the extracellular surface contains glycoproteins and glycolipids
46
Describe peripheral proteins
Attach to integral proteins, and are loosely attached to the phospholipid head
47
What are the roles of peripheral proteins?
Participate in intracellular signaling, and form submembraneous cytoskeleton
48
What do integral proteins include?
Transmembrane proteins and lipid anchored proteins
49
What are the roles of
integral proteins?
- Membrane receptors
- Cell adhesion molecules
- Transmembrane movement
- Enzymes
- Mediators of intracellular signaling
50
Lipid rafts commonly contain an abundance of proteins important in what?
cell signal transduction
51
Describe glycoproteins
A protein with a carbohydrate attached, it forms a protective coat (glycocalyx), and is useful for cell-to-cell recognition
52
Describe glycolipids
A lipid with a carbohydrate attached, it forms a protective coat (glycocalyx), and is useful for cell-to-cell recognition
53
What percentage of the body is considered water?
~60%
54
___, ___, and ____ _____ composition can alter the total water content in the body
Age, sex, body fat
55
Compare adipose tissue with skeletal muscle
Adipose: ~90% lipids, small fraction of water, higher in women
Skeletal: ~75% water, ~18% protein, higher in men
56
Extracellular and intracellular compartments are in _____ equilibrium
osmotic
57
What is osmosis?
The movement of water across a membrane in response to a solute concentration gradient
58
Water moves from a region of ___ solute concentration to a region of ___ solute concentration.
low, high
59
Water can move freely between the intracellular and extracellular spaces via what?
Aquaporin channels
60
True or False: osmotic equilibrium does not equal chemical or electrical equilibrium?
True
61
What is the distribution of ions that are higher in the extracellular fluid?
Na+, Cl-, Ca2+, HCO3-
62
What is the distribution of ions that are higher in the intracellular fluid?
K+, anions (HPO4-, H2PO4-), proteins
63
What is osmotic pressure?
The pressure that would have to be applied to oppose and prevent osmosis
64
Osmolarity describes..?
The # of particles in solution. Osmol/L
65
What is isosmotic?
Solutions have identical osmolarities
66
What is hyperosmotic?
Describes the solution with the higher osmolarity
67
What is hyposmotic?
Describes the solution with the lower osmolarity
68
What is tonicity?
Describes a solution and how that solution would affect the cell volume if a cell were placed in the solution and allowed to come to equilibrium
69
Compare tonicity vs osmolarity in terms of units
Osmolarity has units: mOsm/L
Tonicity has no units
70
Compare tonicity vs osmolarity in terms of what they compare
Osmolarity compares two solutions
Tonicity compares solution and a cell
71
Tonicity depends on the concentration of ___-______ _____
non-penetrating solutes
72
Why does tonicity focus on non-penetrating solutes rather than penetrating solutes?
Penetrating solutes can cross the cell membrane and will do so until reaching equilibrium across the membrane when the cell is exposed to the solution, which is why they do not contribute to cell volume changes
73
What is the difference between osmolarity and osmolality?
Osmolarity: osmol/L
Osmolality: osmol/kg
74
Osmolarity is often used when ____ and ___ are relatively constant
temperature, pressure
75
Diffusion is the movement of molecules from an area of ___ concentration to an area of _____ concentration
higher, lower
76
Diffusion uses what kind of energy, and does it require an outside source?
Kinetic energy of molecular movement, and does not require an outside energy source
77
Under what conditions can diffusion be accelerated?
1. Along higher concentration gradients
2. Over shorter distances
3. At higher temperatures
4. For smaller molecules
78
Under what conditions can the rate of diffusion through a membrane becomes accelerated?
1. The membrane's surface area is larger
2. The membrane is thinner
3. The concentration gradient is larger
4. The membrane is more permeable to the molecule
79
Membrane permeability to a molecule depends on..?
1. The molecule's lipid solubility
2. The molecule's size
3. The lipid composition of the membrane
80
What is Fick's Law of Diffusion?
Rate of Diffusion ∝ surface area × concentration gradient × membrane permeability
81
What is the membrane permeability relationship to lipid solubility and molecular size?
Membrane permeability ∝ (lipid solubility/molecular size)
82
Channel proteins create a ___-filled pore
water
83
What is the composition of channel proteins?
Made of membrane spanning proteins subunits that create a cluster of cylinders with a pore through the center
84
Gated channels are normally closed, so they need a _____ to open the gate
stimulus
85
What are the three kinds of gated channels?
Chemically gated (ligand)
Voltage gated
Mechanically gated
86
Selectivity in channel proteins is determined by the ? and the ? lining the pore, which is usually negative
size of the pore, charge of the amino acids
87
Describe carrier proteins
Large complex proteins, change conformation to move molecules, only open one compartment at a time, it is very slow, and they can move small organic molecules that cannot pass through channels
88
Carrier proteins can be classified into 3 kinds on transporters...?
1. Uniport carriers: one kind of substrate in one direction
2. Symport carriers (co-transporters): +2 substrates in the same direction
3. Antiport carriers (exchangers): move +2 substrates in opposite directions
89
Describe facilitated diffusion
Use channels or carrier proteins, they move down their concentration gradient, there is no energy required, and stops once equilibrium is reached
90
Describe active transport
Moves molecules against their concentration gradients (from low to high)
Support a state of disequilibrium
Requires energy
Uses carrier proteins
91
What are the two kinds of active transport?
Primary and secondary
92
Describe primary active transport
The energy to move molecules comes directly from hydrolyzing ATP
93
Describe secondary active transport
Uses the potential energy stored in the concentration gradient of one molecules to push another molecule against their concentration gradient
94
What is specificity?
Refers to the ability of a transport to move one molecule or a closely related group of molecules
95
What is competition?
A carrier may move several members of a related group of substances but these substances compete with one another
96
What is saturation?
Rate of transport depends on concentration and number of transporters. Transport normally increases with increasing concentration until transport maximum is reached
97
What is phagocytosis?
Creates vesicles using the cytoskeleton. It requires ATP to move the cytoskeleton and for intracellular transport of the vesicles
98
How does endocytosis differ from phagocytosis?
Membrane indents
Vesicles are much smaller
Can be constitutive
Also requires ATP
99
What is the non-selective and selective kinds of endocytosis?
Non-selective: pinocytosis (allows ECF to enter)
Selective: receptor mediated transport
100
_____ can be used instead of clathrin coated pits
Caveolae
101
Substances entering and exiting the body or moving between compartments often cross a layer of _____ cells
epithelial
102
What is absorption?
From lumen/organ to ECF
103
What is secretion?
From ECF to lumen/organ
104
What is another word for the free surface of an epithelial cell?
Apical
105
What are the 3 kinds of epithelial transport?
Transcellular, Paracellular, Transcytosis
106
Describe transcellular transport
across epithelial cell
107
Describe paracellular transport
between tight junctions
108
Describe transcytosis
extracellular cargo is endocytosed, shuttled across the cytoplasm in membrane‐bound vesicles, and secreted at a different plasma membrane surface
109
Why are transporting epithelia polarized?
Polarized distribution of membrane transporters ensures one-way movement
110
Compare passive vs. active vs. vesicular vs. epithelial transport in terms of energy
Passive: does not require energy
Active: require energy
Vesicular: requires energy
Epithelial: sometimes requires energy
111
Compare passive vs. active vs. vesicular vs. epithelial transport in terms of types
Passive: simple and facilitated
Active: primary and secondary
Vesicular: phago, endo, and exocytosis
Epithelial: paracellular, transcellular, and transcytosis
112
The body as a whole is electrically ______
neutral
113
What is the membrane potential difference or membrane potential (Vm)?
The electrical disequilibrium that exists between the ECF and ICF
114
What is the electrochemical gradient?
The combination of electrical and concentration gradients
115
What is equilibrium potential?
The membrane potential that exactly opposes the concentration gradient
116
What is the resting membrane potential?
The membrane potential of a cell when it is not active
117
What is the function of Na-K ATPase?
Sets up concentration gradients that determines membrane potential, and maintains the concentration gradients for Na+ and K+
118
If the membrane potential becomes less negative than the resting potential the cell ____
depolarizes
119
If the membrane potential becomes more negative, it ______
hyperpolarizes
120
Describe the nervous system?
Coordinates voluntary and involuntary actions and transmits signal to and from different parts of its body
121
What is the term Afferent?
Carry information towards CNS
122
What is the term Efferent?
Carry information away from CNS
123
What is included in the Central Nervous System?
Brain and spinal cord
124
What is included in the Peripheral Nervous System (PNS)?
Nerve tissue outside the CNS: cranial nerves and branches, spinal nerves and branches, ganglia, plexuses, and sensory receptors
125
What are the 2 subdivision of the peripheral nervous system?
Afferent (sensory) division
Efferent (motor and autonomic) division
126
What comprises the efferent division?
Somatic motor and autonomic
127
What three components feed into the afferent division?
Somatic sensory
Visceral sensory
Special sensory
128
What are neurons?
Basic signaling units of the nervous system
129
What are glia?
support cells
130
What is the cell body (soma)?
Considered the control center, with processes that extend outward; dendrites and axons
131
What are dendrites?
Receive incoming signals from neighboring cells
132
What are axons?
Carry outgoing signals from the integrating center to target cells
133
What are presynaptic terminals?
Contain transmitting elements
134
What is the synapse?
The region where an axon terminal communicates with its postsynaptic target cell
135
Describe afferent (sensory) neurons
Carry information about temperature, pressure, light, and other stimuli to the CNS
Specialized receptor converts stimulus to electrical energy
136
What are interneurons?
Complex branching neurons that facilitate communication between neurons
137
Describe efferent (motor and autonomic) neurons
Motor: control skeletal muscles
Autonomic: influences many internal organs
Usually have axon terminals or varicosities
138
What are the two categories of the autonomic neuron?
Sympathetic and parasympathetic
139
What are nerves?
Bundles of peripheral neurons, they can be efferent, afferent or mixed
140
The axon is specialized to convey ____ and ____ _____ that require a variety of different types of proteins
chemical and electrical signals
141
The axon contains many types of ____ and _____ but lacks ____ and ___ necessary for protein production
fibers and filaments, ribosomes and ER
142
Arrange the following statements into the proper order of axonal transport:
1. Synaptic vesicle recycling
2. Fast axonal transport walks vesicles and mitochondria along microtubule network
3. Vesicle contents are released by exocytosis
4. Retrograde fast axonal transport
5. Old membrane components digested in lysosomes
6. Peptides are synthesized on rough ER and packaged by the Golgi
6, 2, 3, 1, 4, 5
143
What is considered fast axonal transport?
Membrane bound proteins and organelles (vesicles or mitochondria). Anterograde (up to 400mm/day) and retrograde (up to 200mm/day)
144
What direction is anterograde?
cell body to axon terminal
145
What direction is retrograde?
axon terminal to cell body
146
What is slow axonal transport?
Cytoplasmic proteins (enzymes) and cytoskeleton proteins. Not well characterized, may be due to frequent periods of pausing of movements
147
What are kinesins?
Anterograde transport
148
What are dyneins?
Retrograde transport
149
___ ____ drives movement of proteins to "walk" along filaments
ATP hydrolysis
150
In the synapse, the space contains ____ ____ that hold the pre and post synaptic cells in close proximity
extracellular matrix
151
Axons of embryonic neurons contain _____ _____ that sense and move towards particular chemical signals
growth cones
152
Growth cones depend on..?
Growth factors
Molecules in the extracellular matrix
Membrane proteins
153
Synapse must be maintained through ?
Repeated use
154
Where are glial cells found?
Ependymal cells - CNS
Astrocytes - CNS
Microglia - CNS
Oligodendrocyte - CNS
Schwann cells - PNS
Satellite cells - PNS
155
What is myelin?
A substance composed of multiple concentric layers of phospholipid membrane wrapped around an axon
156
What is the purpose of myelin?
Provides structural stability, acts as insulation around the axon to speed up electrical signals, supply trophic factors
157
Where do you find myelin in the CNS?
oligodendrocyte
158
Where do you find myelin in the PNS?
Schwann cells
159
Where do you find satellite glial cells?
Exist within ganglia in the PNS
160
What is the purpose of satellite glial cells?
Form a supportive capsule around the bodies of neurons. Supply nutrients, structural support, and provide a protective cushion
161
What are astrocytes?
Highly branched glial cells in the CNS believed to make up half of all cells in the brain. There are several subtypes that form a functional network
162
What are the four functions of astrocytes?
Take up and release chemicals at synapses
Provide neurons with substrates for ATP production
Help maintain homeostasis in the ECF
Surround vessels (part of the blood-brain barrier)
163
What are microglia?
Specialized immune cells that reside in the CNS
164
What is the purpose of microglia?
Serve to protect and preserve neuronal cells from pathogens and facilitate recovery from metabolic insults
165
If the signals that activate microglia pass a threshold with respect to intensity, or microglia remain activated past a certain time period, these cells start to display..?
Detrimental properties
166
What are ependymal cells?
Line fluid filled cavities in the brain and spinal cord
167
What is the purpose of ependymal cells?
Help to circulate cerebrospinal fluid that fills these cavities and surrounds the brain and spinal cord. Is for protection, chemical stability, and clearing wastes
168
What is the difference in the ability to repair a neuron injury between the PNS and CNS?
CNS repair is less likely to occur naturally, as the glia tend to seal off and form scar tissue. However, the PNS can repair naturally
169
Schwann cells can create a tube to ____ the regenerating axon
guide
170
What does the Goldman-Hodgkin-Katz equation predict?
That membrane potential that results from the contribution of all ions that can cross the membrane
171
How is the Goldman-Hodgkin-Katz equation determined?
As the combined contribution of each ion (concentration x permeability) to the membrane potential
172
How does the Goldman-Hodgkin-Katz equation and Nernst equation differ?
Goldman-Hodgkin-Katz equation: combined contribution of each ion
Nernst equation: calculates the equilibrium potential for a single ion
173
What is the resting membrane potential in most neurons? What mainly causes that?
~-70mV, mainly caused by K+
174
What alters the membrane potential?
A change in the K+ concentration or a change in permeability to ions
175
A significant change in membrane potential does not indicate ..?
A change in concentration gradient of a given ion
176
How many ions need to move to alter the membrane potential?
Very few
177
The concentration gradients for ions remain relatively ____ during most alterations in membrane potential
constant
178
Ion permeability is primarily altered by ..?
Opening/closing ion channels in the membrane
179
What are the 5 major types of ion channels?
1. Na+
2. K+
3. Ca2+
4. Cl-
5. Monovalent cation channels
180
What is conductance?
The ease with which ions flow through a channel
181
How do mechanically gated channels open?
Open in response to physical forces found in sensory neurons
182
How do chemically gated channels open?
In neurons respond to ligands including extracellular neurotransmitters and neuromodulators or intracellular signaling molecules
183
How do voltage gated channels open?
Respond to changes in the cells membrane potential
184
What are some examples of variation in gated channels?
1. Voltage required for channel opening
2. The speed at which channels open/close
3. Many channels that open to depolarizations will close during repolarization
4. Some channels spontaneously inactivate
5. Each major channel type has subtypes
185
What is the affect of this channelopathy: mutation alter permeation pathways?
Can disrupt how ions normally flow through the ion channel
186
What is the affect of this channelopathy: mutation changes channel activation?
Can alter channel activation
187
What is the affect of this channelopathy: mutation change channel inactivation process?
Can alter channel inactivation
188
What is current?
The flow of electrical charge carried by an ion
189
What is Ohm's law?
Current flow (I) is ∝ to the electrical potential different (V) between two points and inversely proportional to the resistance (R); I = V/R
190
What are two sources of resistance in a cell?
Membrane resistance (Rm) - resistance of phospholipid bilayer
Internal resistance of the cytoplasm (Ri) - cytoplasmic composition and size of the cell
191
Resistance will determine..?
How far current will flow in a cell before the energy is dissipated
192
Voltage changes across the membrane can be classified
in to two types of electrical signals..?
1. Graded potentials
2. Action potentials
193
What are graded potentials?
Variable strength signals that travel over short distances and lose strength as they travel. They can be depolarizing or hyperpolarizing. If graded potentials create a large enough depolarization, it can induce an action potential
194
What are action potentials?
Very brief, large depolarizations that travel for long distances through a neuron without losing strength. Rapid signals over long distances
195
Where are the graded/action potentials in the CNS and efferent neurons?
Graded: dendrites, nucleus, and soma
Action: axon, and axon terminals
196
Where are the graded/action potentials in sensory neurons?
Graded: sensory receptors
Action: peripheral process, central process, axon
197
Why are graded potentials considered "graded"?
Because amplitude (size) is directly proportional to the strength of the stimulus an can vary
198
How are graded potentials generated?
By the chemically gated (ligand gated) ion channels or closure of leak channels (CNS and efferent neurons)
199
What is local current flow?
A wave of depolarization or hyperpolarization that moves through the cell
200
Graded potentials lose strength as they move through the cell due to..?
1. Current leak: open channels allow ions to leak out
2. Cytoplasmic resistance
201
Between depolarization and hyperpolarization, which is excitatory and which is inhibitory?
Depolarization: excitatory postsynaptic potential (EPSP)
Hyperpolarization: inhibitory postsynaptic potential (IPSP)
202
What is the trigger zone?
AKA the axon hillock. There is a high concentration of voltage gated Na+ channels, and if the membrane potential is ~-55mV, and action potential will be generated
203
Where do action potentials travel?
Electrical signals of uniform strength that travel from the trigger zone to the axon terminals
204
____ opening of voltage gated ion channels in the axon membrane as electrical current moves down.
Sequential
205
What is conduction?
Movement of an action potential along the axon, they travel over long distances without losing energy
206
True or False: action potentials travel through the cell
False, not a single action potential that travels through the cell but rather a new action potential generated in each adjacent area
207
Conduction of the action potential requires a few types of ion channels..?
Voltage gated Na+ and K+ channels as well as the leak channels that help set the resting membrane potential
208
Voltage gated Na+ and K+ channels are both activated by _____, K+ channels just open more slowly
depolarization
209
Order these steps into the proper chronological order:
1. Na+ channels close and slower K+ channels open
2. Depolarizing stimulus
3. Cell returns to resting ion permeability and resting membrane potential
4. Rapid Na+ entry depolarizes cell
5. Resting membrane potential
6. K+ channels remain open and additional K+ leaves the cell, hyperpolarizing it
7. K+ moves from the cell to ECF
8. Voltage gated K+ channels close, less K+ leaks out of the cell
9. Membrane depolarizes to threshold. Voltage gated Na+ and K+ channels begin to open
5, 2, 9, 4, 1, 7, 6, 8, 3
210
What is the rising phase?
Depolarization
Depolarizing stimuli open voltage gated Na+ channels, allow Na+ to travel down electrochemical gradient
211
What is the falling phase?
Repolarization
Voltage gated K+ channels also open in response to depolarization, but do so more slowly than Na+ channels causing delayed efflux
212
What is the after-hyperpolarization phase?
Undershoot. Voltage gated K+ do not immediately close when reaching -70mV, causing the membrane potential to dip below the resting membrane potential. Leak channels bring the membrane potential back to -70mV
213
___ ___ returns ions to original compartments
Na-K ATPase
214
Compare graded and action potential in terms of what type of signal?
Graded: input signal
Action: regenerating conduction signal
215
Compare graded and action potential in terms of where it ocurs?
Graded: usually dendrites and cell boy
Action: trigger zone through the axon
216
Compare graded and action potential in terms of the types of gated ion channels involved?
Graded: mechanically, chemically, or voltage gated channels
Action: voltage gated channels
217
Compare graded and action potential in terms of the ions involved?
Graded: usually Na+, K+, Ca2+
Action: Na+, K+
218
Compare graded and action potential in terms of depolarizing/hyperpolarizing?
Graded: depolarizing or hyperpolarizing
Action: depolarizing
219
Compare graded and action potential in terms of the strength of the signal?
Graded: depends on the initial stimulus, can be summed
Action: all-or-none, cannot be summed
220
Compare graded and action potential in terms of what initiates the signal?
Graded: entry of ions through gated channels
Action: above-threshold graded potential at the trigger zone opens ion channels
221
Compare graded and action potential in terms of unique characteristics?
Graded: no minimum level requires to initiate, two signals coming close together will sum, initial stimulus strength is indicated by the frequency of a series of action potentials
Action: threshold stimulus required to initiate, refractory period: two signals too close together in time cannot sum
222
How do voltage gated Na+ channels suddenly close at the peak of an AP?
Contains two gates: an activation gate and an inactivation gate.
223
What are the steps in closing a voltage gated Na+ channel?
1. With activation gate open. Na+ enters the cell
2. Inactivation gate closes and Na+ entry stops
3. During repolarization caused by K+ leaving the cell, the two gates reset to their original positions
224
Double gating of Na+ channels creates a ____ ____
refractory period
225
What is an absolute refractory period?
A second AP cannot be initiated 1-2msec
226
What is a relative refractory period?
A second AP can be initiated but requires a larger than normal depolarizing stimulus (graded potential) 2-5msec
227
What is the purpose of a refractory period?
Ensures an AP travels in one direction, and limits the rate at which signals can be transmitted down a neuron
228
When ____ ions enter the neuron, current flows to ____ sections of the axon
positive, adjacent
229
Order the steps in how action potentials are conducted:
1. Local current flow causes new section of the membrane to depolarize
2. Voltage-gated Na+ channels open, and Na+ enters the axon
3. Graded potential enters trigger zone
4. Positive charge spreads along adjacent sections of axon by local current flow
5. The refractory period prevents backwards conduction
6. Loss of K+ repolarizes the membrane
3, 2, 4, 1, 6, 5
230
What are the two physical parameters to determine the velocity of conduction?
1. The diameter of the axon
2. The resistance of the axon membrane to ion leakage
231
What is the relationship between the velocity of conduction and the diameter of the axon?
A larger diameter axon will offer less internal resistance to current flow
232
AP conduction is more rapid in axons with ___-____ membranes (decreased current leak)
high resistance
233
Nodes of Ranvier contain an abundance of ___ channels
Na+
234
____ axons are larger diameter axons (10µm ~120m/sec), ______ axons are smaller diameter axons (1.5µm ~2m/sec)
myelinated, unmyelinated
235
Due to the fact that only nodes contain Na+ channels, the AP cannot be maintained in the ____ region, due to a lack of Na+ channels
unmyelinated
236
Current leaks out of the _____ region, increasing the likelihood that the ___ __ _____ is subthreshold
unmyelinated, wave of depolarization
237
Chemicals exist that can interfere with ______ by binding to Na+, K+, or Ca2+ channels in the neuron
conduction
238
Electrical activity can also be altered through changes in _____ ____ of certain ions
extracellular concentration
239
The concentration gradient for ___ is crucial in setting the resting membrane potential
K+
240
Neurons communicate at ___
synapses
241
Neurons communicate at synapses: ______ ___ (neuron) to ______ ____ (neuron, muscle, taget cell)
presynaptic cell, postsynaptic cell
242
Describe electrical synapses and where they may be found
Ions flow from one cell directly to the next. May be found in: some CNS neurons, cardiac muscle, smooth muscle
243
Describe chemical synapses and where they may be found
Electrical signals from the presynaptic cell is converted to a neurocrine signal that crosses the synaptic cleft and binds to a receptor on the postsynaptic cell
May be found in: the majority of neurons in the nervous system
244
What is a neurocrine?
A chemical substance released from neurons used for cell-to-cell communication
245
What are the three types of neurocrine?
Neurotransmitters, neuromodulators, neurohormones
246
What are neurotransmitters?
A chemical that is released, acts on a postsynaptic cell in close vicinity and causes a rapid response in the postsynaptic cell
247
What are neuromodulators?
A chemical that is released, acts on a postsynaptic cell in close vicinity and causes a slow response in the postsynaptic cell
248
What are neurohormones?
Are secreted into the bloodstream and act on targets throughout the body
249
The ____ neurocrine can act as a ____ at one synapse and a _____ at another depending on the receptors present
same, neurotransmitter, neuromodulator
250
There are 2 categories of neurocrine receptors: ?
1. Ionotropic receptors (ligand gated channels)
2. Metabotropic receptors (g-protein coupled receptors)
251
Ligand binding to ionotropic receptors causes a ______ change leading to the opening of the channel
conformational
252
True or False: ionotropic receptors are only specific for one ion?
False: they can be specific or a non-selective cation channel
253
Do ionotropic receptors mediate fast/slow postsynaptic responses? And which neurocrine can this be aligned with?
Fast, neurotransmitter
254
Do metabotropic receptors mediate fast/slow postsynaptic responses? And which neurocrine can this be aligned with?
Slow, neuromodulators
255
The cytoplasmic tail of the receptor is linked to ? (aka the g-protein)
three part membrane transducer protein
256
Ligand binding to metabotropic receptor leads to 2 different g-protein mediated cellular responses: ?
1. Interact directly with ion channels
2. Activate membrane bound enzymes
257
In metabotropic receptors, when they interact directly with ion channels, what does this lead to?
Can lead to the opening or closing of a channel depending on the g-protein
258
In metabotropic receptors, there are two main types of interactions with a membrane bound enzyme: ?
A. Phospholipase C Signal transduction pathway
B. Adenylyl cyclase signal transduction pathway
259
Describe the phospholipase C signal transduction pathway
There is an increase in intracellular Ca2+ that mediates a cellular response. PKC can also mediate a cellular response
260
Describe the adenylyl cyclase signal transduction pathway
PKA phosphorylates proteins to cause a cellular response
261
True or False: one neurocrine can have multiple receptors?
True
262
Vesicles containing neurotransmitter accumulate in the ___ ____ ready to be released on demand
axon terminal
263
Describe synthesis in terms of neurotransmitters in vesicles
Large peptide neurotransmitters are produced and packaged into vesicles at the soma and transported by fast axonal transport. They are dense core vesicles
264
Small neurotransmitters are synthesized and packaged at the ___ ____ (empty vesicles transported from soma or recycled vesicles)
axon terminal
265
The enzymes for synthesis are brought to the terminal via ___ axonal transport
slow
266
Neurotransmitter release occurs via..?
Ca2+ mediated exocytosis
267
The presynaptic terminal contains a high concentration of ____-_____ __ channels
voltage-gated Ca+
268
Neural signaling of ___ duration is due to the..?
short, rapid removal or inactivation of neurotransmitter in the synaptic cleft
269
Neurotransmitter binding depends on the ____ in the cleft
concentration
270
Order these statements into the proper order:
1. Enzymes inactivate neurotransmitters
2. Neurotransmitters can diffuse out of the synaptic cleft
3. Neurotransmitters can be returned to axon terminals for reuse or transported into glial cells
3, 1, 2
271
A single AP releases a ___ ____ of neurotransmitter in one neuron
set amount
272
Increased AP firing leads to ? and ?
A greater influx of Ca2+
Increased neurotransmitter release
273
True or False: one excitatory event is often not enough to reach threshold in the postsynaptic cell?
True
274
What is convergence?
Many presynaptic neurons may converge on one or a small number of postsynaptic neurons
275
What is divergence?
Neurons can have branching axons that contact many different postsynaptic neurons
276
Input from ? on a single postsynaptic neuron is summated to determine the output of the postsynaptic neuron
multiple presynaptic neurons converging
277
In terms of neurons, what is the meaning of spatial?
Different locations
278
Spatial summation occurs when..?
Currents from multiple nearly simultaneous graded potentials combine
279
Each individual EPSP is subthreshold, but..?
All reach a trigger zone simultaneously and summate
280
True or False: spatial summation is only promotional in nature?
False: it can be inhibitory
281
Graded potentials from the ___ presynaptic neuron arriving at the trigger zone nearly ______ may be summated
same, simultaneously
282
What is postsynaptic integration?
When both temporal and spatial graded potentials are incorporated in a neuron
283
What is an axo-axonic synapse?
Excitatory or inhibitory neurons may synapse on synaptic terminals and augment communication
284
What is presynaptic inhibition?
Inhibits neurotransmitter release
285
What is presynaptic facilitation?
Increases neurotransmitter release
286
Synaptic activity can be altered by changing the target (postsynaptic) cell's ______ to a neurotransmitter
responsiveness
287
How can a cell's responsiveness to a neurotransmitter be altered?
Usually be changing the structure, affinity, or number of neurotransmitter receptors
