phys lab exam (1-3)

What 3 things did we do in lab 3?

1. Apply multiple stimuli at different time delays to differentiate relative and absolute refractory period of an action potential 2. Apply different stimuli strength to differentiate relative and absolute refractory period of an action potential 3. Apply toxins to neurons to investigate postsynaptic potentials

Which neurotransmitters commonly have inhibitory effects at neuronal synapses?

GABA glycine

which ion has the greatest effect on membrane potential?

K+ because it has more leak channels and is therefore more permeable

Afterhyperpolarization

Membrane potential becomes more negative than resting potential at the end of an action potential

Repolarization

Membrane potential returning from peak towards resting membrane potential

Why can another action potential be elicited during the relative refractory period?

There are enough voltage-gated sodium (Na+) channels in the closed state before the next stimulus.

TEA

blocks K channel, high depolar, slow repolar,

steps of action potential propogation/NT release

1. presynaptic neuron fires action potential 2. AP reaches axon terminal 3. Voltage-gated Ca channels open 4. Increase of intracellular Ca concentrations 5. Synaptic vesicle fused to axon terminal 6. Exocytosis of NT into synaptic cleft 7. NTs activate receptors and postsynaptic potentials are produced

Which of the following is FALSE about the resting membrane potential? (A) The resting membrane potential is negative because the intracellular concentration of sodium (Na+) is higher than the intracellular concentration of potassium (K+). (B) It is the steady transmembrane potential of a cell that is not producing an electrical signal. (C)In mammalian cells, the value of the resting membrane potential is mainly determined by the permeability of K+. (D)The magnitude of the resting membrane potential is negative inside the cell relative to the outside the cell.

A - intracellular K+ is greater than Na+

excitatory postsynaptic potential (EPSP)

A depolarization in the membrane of a postsynaptic neuron caused by the activation of postsynaptic receptors

inhibitory postsynaptic potential (IPSP)

A hyperpolarization in the membrane of a postsynaptic neuron that makes it more difficult for a postsynaptic neuron to generate an action potential

Which correctly describes a DIFFERENCE between a graded potential and an action potential? (A) Graded potentials can only depolarize. (B) Graded potential magnitude can vary depending on the strength of the stimulus. (C) A graded potential is a type of membrane potential. (D) Graded potentials have a threshold and refractory period.

B

Which of the following statements is TRUE about action potentials? (A) The direction of action potential propagation is towards the membrane segment that is in absolute refractory period. (B) The generation of action potentials is never preceded by a graded potential. (C) Action potential propagation in a myelinated neuron is called saltatory conduction. (D) Action potentials decrease in magnitude with distance (from the stimulus) along the axon.

C

T or F: During the absolute refractory period of an action potential, another action potential can be elicited if the second stimulus is strong enough.

FALSE

spatial summation

Graded membrane potential produced as multiple inputs, occurring at different synapses, are added together

temporal summation

Graded membrane potential produced as repetitive inputs at one synapse, occurring at different times, are added together

Depolarization

Membrane potential becomes less negative

Hyperpolarization

Membrane potential becomes more negative than resting membrane potential

Alpha BT

N-Ach-R blocker, postsynaptic, IPSP

Overshoot

Reversal of membrane potential polarity

Cd2+

blocks Ca channel, presynaptic

Picrotoxin

blocks GABA and glycine, EPSP, postsynaptic

TTX

blocks Na channel, no AP, presynaptic

opening of what channels will produce an EPSP?

calcium nonspecific cation

opening of what channels with produce an IPSP?

chloride potassium

sodium channels during action potential

closed closed to open open to inactivated inactivated to closed

potassium channels during action potential

closed open transitioning from open to closed

Which neurotransmitters commonly have excitatory effects at neuronal synapses?

glutamate acetylcholine

In a biological system, the electrical charges that produce a membrane potential come from:

ions

artifacts

look like AP but are not -> no AP because not enough Na going into cell compared to K going out (conductance of Na must be greater than K)

What are the channel conformations of neuronal voltage-gated potassium (K+) channels?

open closed

What are the channel conformations for neuronal voltage-gated sodium (Na+) channels?

open closed inactive

Scorp Tx

prevents Na inactivation, high depolar, slow repolar

two point discrimination

small receptive fields and more nerve endings in face and fingertips

What does the nernst equation describe?

the membrane potential at which the chemical and electrical fluxes become equal in magnitude but opposite in direction for a particular ion

what does having 20/10 vision mean?

what you can see 20 ft away, the average person can only see 10 ft away

when will the initial segment of a neuron reach threshold?

when enough EPSPs summate

photobleaching

when staring at a certain color/overusing those cones, if you switch to white the other 2 cones will overcompensate and you will see that color