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.