Lab 8
postsynaptic potential
changes in membrane potential of postsynaptic terminal of chm synapse
8. Identify the location within a neuron where a graded potential and an action potential occur.
graded is at dendrite/ cell body. action- on axon
repolarization
phase of the action potential in which the membrane potential returns toward the resting membrane state and becomes more negative
after-hyperpolarization.
phase of the action potential that comes after the repolarization phase in which the plasma membrane may be slightly hyperpolarized for a short period. K open, more toward negative
4. Define, describe and/or identify the trigger zone
trigger zone-receives inputs from blood borne drugs or hormones and communicates w/ other structures in the vomiting center to initiate vomiting. more excitable than any other part. between axon hillock and initial segment .
events that take place at a synapse.
Action potential arrives at axon terminal. Voltage-gated calcium channels open. Neurotransmitter released into synaptic cleft. Neurotransmitter binds to receptors. Graded potential generated in postsynaptic cell. Neurotransmitter is removed from the synaptic cleft -The correct sequence starts with a neural signal at the presynaptic cell, followed by the release of neurotransmitter, the creation of a graded potential in the postsynaptic cell, and degradation of the neurotransmitters. Look in notes**
19. Differentiate between a graded potential, an action potential and a compound action potential.
Compound Action Potentials The activity of many cells firing at once graded potential-Changes in the membrane potential that are confined to a relatively small region of the plasma membrane. The magnitude of the potential change can vary. action potential -A brief all-or-none depolarization of the membrane, reversing polarity in the neurons; it has a threshold and refractory period and is conducted without decrement
14. Describe, in detail, the events of an action potential in a neuron, including the types of ion channels involved.
Concentration gradients are key behind how action potentials work. In terms of action potentials LOOK on printed sheet for steps**
equilibrium potential
Equilibrium potential: membrane potential when cell is at electrochemical equilibrium [K+]out=5nM [K+]in=150nM [Na+]out=150 [Na+]in=15 Plug numbers into Nernst to get equilibrium potentials Differences in equilibrium potential: smaller gradient for Na so magnitude is less. Na is positive because conc. outside the cell is greater than in therefore, Na would move into the cell, making it more positive.
6. Describe and/or identify the type of mylenation associated with the peripheral nervous system and the nodes of Ranvier.
PNS myelin is produced by Schwann cells. distance between nodes of Ranvier determines the conduction rate.
9. Calculate the equilibrium potential for an ion using the Nernst equation given the ICF and ECF concentrations for the ion.
R=.002 T+=210 F=.023 Z=valence Look in notes at example
24. Describe the effects of tetrodotoxin (TTX) and lidocaine on the generation of an action potential.
Works by blocking voltage-gated sodium channel necessary for producing an action o
depolarization
a decrease in the membrane potential in which the charge difference, or polarity, across the plasma membrane decreases. more postitive
16. Define the term refractory period.
a time when the action potential causes the sensitivity on that given point on the plasma membrane to decrease
subthreshold stimulus
brief weak stimuli producing sub threshold depolarization
sensory transduction
conversion of a sensory stimulus from one to another
13. Define the terms sensory transduction,
conversion of specific type of energy into electrial signal
3. List, describe and/or identify the three parts of a neuron.
dendrite, axon-axon terminal, call body\
Neuron
dendrites: receive signals from neighboring neurons (like a radio antenna) axon: transmit signals over a distance (like telephone wires) axon terminal: transmit signals to other neuron dendrites or tissues (like a radio transmitter) myelin sheath: speeds up signal transmission along the axon
1. Describe irritability and conductivity as they relate to a neuron.
excitability/ irritability respond to stimuli and convert them to AP conductivity- transmit AP along length of cell
receptor potential,
graded potentials produced in response to stimulus acting on sensory recceptor. caused by opening and closing of ion channels.
5. Define and/or describe the terms action potential
in memberanes of excitable tissues in response to graded potentials that depolarize the membrane to threshold
synapse
junction between 2 nerve cells, consisting of a minutee gap across which impulses pass by diffusion of a neurotransmitter.
12. Describe the physiological basis of a graded potential.
ligand and mechanical channels cause some changes but not AP. Hyperpolarizing is making more polar (negative)
conduction velocity
measuring the distance traveled (length of the nerve in m) and dividing by the time (sec) taken to complete the reflex arc, also called the latency.
2. Distinguish between a nerve and a neuron.
nerve-bundle of fibers composed of neurons neurons- specialized cells which are capable of transmitting signals between different parts of the body
electrochemical gradient
net effect of chm and electrical forces on ion
11. Describe the physiological basis for the resting membrane potential of a neuron.
potential differences across membrane of resting cell generated by differences in ionic makeup of ICF and ECF. slightly permeable to NA, very perm to K. NA/K pump stabliizes RMP (3 Na out, 2 K in )
7. Describe, in general, the structures involved in a synapse
presynaptic membrane formed by terminal button on an axon. postsynaptic membrane- segment of dendrite or cell body. synaptic cleft lies between
propagation
process of AP transmission down axons
saltatory conduction
process that describes how an action potential is conducted from one node of Ranvier to another
threshold stimulus
produces a graded potential that is just strong enough to reach threshold an cause the production of a single action potential
physiological basis for the propagation of action potentials in unmyelinated and myelinated axons
propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials.(saltatory conduction) Unmyelinated????
conduction
rate AP are propagated down axon ( conduction velocity)
graded potential
relatively small charge in Vm produced by stimulus that opens chm regulated ion channels. strength related to stimulus strength
local potential
small charge in resting membrane of a neuron caused by a stimulus that opens a ligand regulated Na gate in the membrane of a neuron
nodes of ranvier
small gaps in mylin sheath of medullated axons
Describe the effects of nerve size and myelination on conduction velocity.
small myelinated fibres conduct action potentials more rapidly . while the unmyelinated more slowly
axon hillock
specialized part of the cell body of a neuron that connects to the axon. AP initiated
absolute refractory period
the first part of the refractory period; complete insensitivity exists to another stimulus
action potential frequency
the number of action potentials produced per unit of time in response to a stimulus
relative refractory period
the second part of the refractory period; a stronger-than-threshold stimulus can initiate another action potential during the relative refractory period
22. Describe the role of Ca2+ in neurotransmitter release.
when Ca2+ channels are blocked, neurotransmitter release is inhibited.