Unit 2 - Nerve and Synapse Flashcards
the basic building blocks of the human brain
neurons
all brain functions involve the generation and transmission of __________ by and between nerve cells at ___________
electrical signals, neuromuscular junctions
what are the two key components of the central nervous system?
the brain and spinal chord
what are the two key components of the peripheral nervous system?
the crainial nerves and spinal nerves
a set of twelve nerves connected directly to the brain which are responsible for things like facial expressions and movements
cranial nerves
a set of nerves connected directly to the spinal chord that are responsible for modulating motor and sensory information
spinal nerves
neurons recieve synaptic inputs from other cells at their _________
dendrites
what are the three types of neurons?
1) sensory neuron
2) motor neuron
3) interneuron
all neurons have __________ for recieving/integrating inputs, conducting action potentials, and for sending __________ at synapses
specialized sub-regions, chemical signals
what is the equation for membrane potential?
Vm = Vi - Vo
by convention, the outside of the nerve cells is considered to be _____mV because ________
0, it is very stable
what is the resting membrane potential of a nerve cell?
-70mV
what is the net current of the resting membrane potential?
I = 0
the membrane is impermeable to what three key ions?
Na+, K+, Cl-
what is the Nerst equation?
Ex = (58/z)log([X]o/[X]i)
concentration gradients are maintained by _______, notably the ______ pump
ATPases, Na/K
compared to the outside of the cell, the inside has a __________ charge
negative
what are the four basic steps of an action potential?
1) depolarization
2) repolarization
3) hyperpolarization
4) return to rest
when negative ions move outside of the nerve cell, and positive ions move inside the nerve cell, this creates a _______
negative current
when negative ions move inside the nerve cell, and positive ions move outside the nerve cell, this creates a _______
positive current
a measure of easiness of ion flow across a resistor, with units in siemens
conductance (G)
the inverse of conductance, with units in ohms
resistance (R)
the electrival driving force to move charges
Voltage (V)
what is Ohm’s Law according to cell physiology?
I = G(Vm - Vrest)
the magnitude of a chemical driving force is proportional to the _______
concentration gradient
the electrical driving force on ions is provided by the _______
membrane potential
what does it mean for an ion channel to be selective?
the channels are permeable only to specific ions
what does it mean for ion channels to be non-selective?
the channels are permeable to most if not all ions
what does it mean for an ion channel to be gated?
has a specific trigger to open/close it, very regulated and controlled
ion flow across a membrane is driven by:
electrochemical gradient
how many ions flow through an open ion channel per second?
10^7-10^8
- ligands
- post-translational modifications
- depolarization/ hyperpolarization
- stretch, pressure, flow
- non-gated
these are all types of:
channel gating
ATPase is an example of what type of transport?
primary active transport
symporters and antiporters are an example of what type of transport?
secondary active transport
uniporters and ion channels, which are driven by their own electrochemical gradient, are an example of what type of transport?
passive transport
what is a symporter?
an ion channel where the driving molecule and the transport molecule move in the same direction
what is an antiporter?
an ion channel where the driving molecule and transporter molecule move in the opposite direction
in a transport cycle, the transporters undergo:
conformational changes
different cells have different _____ for their action potentials
shapes
what are the three main phases of an action potential?
1) depolarization
2) repolarization
3) hyperpolarization/ refractory period
the giant squid has an axon how large?
1mm
what is the role of tetrodotoxin (TTX)?
blocks voltage-gated Na+ channels
what is the role of tetraethylammonium (TEA)?
blocks voltage-gated K+ channels
the slow inactivating of K+ channels while the Na+ channels are already inactivated explains the prescence of:
hyperpolarization
as depolarization increases from 0 - +52 mV, the fast inward Na+ current ______, and the slow outward K+ current _______
decreases, increases
at +65mV, the fast Na+ current becomes:
positive
4 identical proteins embedded in the cell membrane that form the voltage gated K+ channel
tetramer
4 non identical proteins embedded in the cell membrane that form the voltage gated Na+ channel
monomer
how many activation segments does a K+ tetramer have?
4
how many activation segments does an Na+ monomer have?
1
in the Na+ channel, the voltage center moves up during _______, then down during ________
depolarization, repolarization
during the refractory period in the Na+ channel, what happens to the voltage centers?
the voltage centers are closed even tighter than at rest in order to prevent another depolarization
membrane potential at which a spike is initiated. always more positive than the resting potential
threshold
magnitude varies with the strength of the stimulus
graded potentials
true or false: graded potentials can be either depolarizing or hyperpolarizing
true
the time during which the axon is resistant to generating a spike. it results from Na+ channels being inactivated and relatively irresponsive to depolarization.
refractory period/ hyperpolarization
passive spread of current down a dendrite/axon depends on:
resistance to flow of current
smaller dendrites/axons have _________ and current flows with ________ down a smaller dendrite/axon.
higher resistance, difficulty
electrically insulating and mechanically supporting layers formed by the plasma membrane of a glial (or schwann) cell
myelin sheath
nodes of ranvier are:
“naked” or without myelin
what is the benefit of myelination along the axon?
the action potential ‘jumps’ and increases conduction speed by 100-10K folds
chemical synapses are _________, whereas electrical synapses are _________
unidirectional, bidirectional
the presence of vesicles in presynaptic terminals is indicative of:
chemical synapses
during the process of recycling neurotransmitters, the import of neurotransmitters to a vsicle requires:
ATP
during the process of recycling neurotransmitters, presynaptic uptake of a neurotransmitter requires:
the cotransport of the neurotransmitter with Na+
synaptic transmissions can be either _______ or _______
excitatory, inhibitory
what is an example of excitatory postsynaptic potential (EPSP)
the neurotransmitter glutamate causing Na+ channels in the postsynaptic neuron to open, causing depolarization
what is an example of inhibitory postsynaptic potential (IPSP)
the neurotransmitter GABA causes Cl- channels in the postsynaptic neuron to open, causing hyperpolarization
the neurotransmitter acetylcholine (ACh) opens non-selective cation channels, which conduct both Na+ and K+ ions, at the:
neuromuscular junction
which enzyme breaks down acetylcholine for recycling?
acetylcholinase (AChE)
what is the effect of acetylcholine opening a nonselective cation channel?
depolarization occurs because there is more Na+ entry than K+ efflux at rest
neurotransmitters and voltage-gated channels work together to create:
postsynaptic action potentials
presynaptic voltage-gated Ca2+ channel activation leads to:
postsynaptic currents
binds to calcium inside of the nerve terminal. this has no effect on presynaptic voltage spike, but blocks the postsynaptic potential by blocking the release of neurotransmitters.
Ca chelator
what is an end-point potential (EPP)?
an EPSP in a muscle cell
true or false: EPSPs decay in size over long distances
true
results from the release of a very small amount of a neurotransmitter, contained in a single vesicle:
miniature endplate potential (MEPP)
neurotransmitters are released in ________ packets: the smallest ________ will release a 0.4mV depolarization
quantal, quantum
one quantum of neurotransmitters is equivalent to:
one vesicle of neurotransmitters
the time between the onset of the presynaptic spike and the onset of EPSP
synaptic delay
what are the five basic steps of a reflex arc?
1) arrival of stimulus and activation of receptor
2) activation of a sensory neuron
3) information processing in the CNS (by interneurons)
4) activation of motor neuron
5) response by effector
