BERNSTEIN PHSC 2301 Action Potential and Synapse

a neural impulse; a brief electrical charge that travels down an axon

action potential

nerves can be easily stimulated or depressed y chemical substances, mechanical stimulation, electrical stimulation, and temperature (true or false)

true

nerves consist of a big number of what

single neurons

registered action potential (compound action potential) is essentially a combination of what

single action potentials

the action potential is initiated where

axon hillock (trigger zone)

axon hillock contains a high density of what two channels

VOC sodium and potassium

action potential is also known as what

information

five major elements of action potential

depolarization, depolarization, threshold, all or none law, refractory period

major element of action potential:
increase in sodium permeability - opening of VOC sodium channels

depolarization

major element of action potential:
increase in potassium permeability - opening of VOC potassium channels

repolarization

major element of action potential:
critical membrane potential that must be reached before action potential

threshold

major element of action potential:
excitable membrane responds to stimuli with a maximal action potential

all or none law

major element of action potential:
a period when new action potential cannot be initiated

refractory period (absolute/relative)

depolarization occurs in approximately how fast

1 ms

depolarization and resting level is achieved in how long

1-2 ms

conduction by local currents, saltatory conduction, axon diameter, and myelin are all part of what effect

self propagating ("domino effect")

Rapid transmission of a nerve impulse along an axon, resulting from the action potential jumping from one node of Ranvier to another, skipping the myelin-sheathed regions of membrane.

saltatory conduction

A gap between successive segments of the myelin sheath where the axon membrane is exposed.

node of ranvier

what are the axon classifications

group a, b, c, and squid giant axon

which axon classification is described:
myelinated, 15-130 m/s, 5-20 mm

group A

which axon classification is described:
ANS fibers, 3-15 m/s, 1-3 mm

group B

which axon classification is described:
unmyelinated, 1 m/s, 0.5-1 mm

group C

which axon classification is described:
unmyelinated, 25 m/s, 500 mm

squid giant axon

myelinated increases or decreases velocity

increases

increase in diameter of the axon increases or decreases velocity

increases

velocity of group A axon

15-130 m/s

velocity of group B axon

3-15 m/s

velocity of group C axon

1 m/s

velocity of squid giant axon

25 m/s

diameter of group a axon

5-20 mm

diameter of group b axon

1-3 mm

diameter of group c axon

0.5-1 mm

diameter of squid giant axon

500 mm

different physical factors (pressure, temperature) and chemical agents (general anesthetics, local anesthetics, and alcohol) can ____________ the ability of the neuron to propane action potential

inhibit

typical equipment to conduct nerve physiology may include electrical stimulator, oscilloscope, and a bio-amplifier (true or false)

true

who coined the term synapse in 1897

(charles) sherrington

who explained the mechanism of chemical synaptic transmission in 1921

(otto) loewi

how many neurons are in the human brain

100 billion

neuron branches in about how many presynaptic terminals

1000

neurons receives approximately __________ synaptic inputs from other neurons

1000

acetylcholine was first discovered when

1921

what are the two types of synapse

electrical and chemical

space between electrical synapses

2-4 nm

electric synapse includes what

gap junction

proteins that form gap junctions

connexin

how many protein connexins make up gap junction

12

synapses are found in cardiac muscle, some brain regions, and embryonic tissue (true or false)

true

gap junctions consists of what two channels

presynaptic and postsynaptic

gap junctions allow massage of metabolites, ions, and molecules less than ____________ dalton

1000

electrical synapses are unidirectional (true or false)

false (bidirectional)

a type of synapse at which a chemical (a neurotransmitter) is released from the axon of a neuron into the synaptic cleft, where it binds to receptors on the next structure (either another neuron or an organ)

chemical synapse

conducts impulses toward the synapse

presynaptic neuron

The narrow gap that separates the presynaptic neuron from the postsynaptic cell.

synaptic cleft

synaptic cleft length

20-40 nm

transmits impulses away from the synapse

postsynaptic neuron

typical elements of a chemical synaptic transmission:
neurotransmitters synthesis and storage in a _________

vesicle

typical elements of a chemical synaptic transmission:
neurotransmitter release in where

synapse

typical elements of a chemical synaptic transmission:
receptor activation on which neuron

postsynaptic

store various neurotransmitters that are released at the synapse

neurotransmitter vesicles

what is the size of a neurotransmitter vesicle?

30-150 nm

neurotransmitter vesicles use ___________ which is a dependent process to uptake and concentrate neurotransmitters

ATP

neurotransmitter vesicles do not contain other molecules (true or false)

false (contains other molecules that assist in packaging (often ATP))

the old theory about neurotransmitters is that majority of neurons contain multiple neurotransmitters (true or false)

false (that is the new theory, old theory is one neuron one neurotransmitter)

majority of neurons contain multiple neurotransmitters (true or false)

true

neurotransmitter release:
the release of a neurotransmitter is dependent on what secretory process

calcium

neurotransmitter release:
the calcium ion signal is detected by a vesicle associated Ca2+ binding protein which is called ________________

synaptotagmin

neurotransmitter release:
the vesicle associated calcium ion fuses with the ________________ membrane at an active zone

presynaptic

neurotransmitter release:
each vesicular packet represents a single _____________ of neurotransmitter

quantum

neurotransmitter release:
discarded vesicles are typically recycled by what process

endocytosis

what are the different types of termination of a neurotransmitter?
_____________ from the synapse, enzymatic degradation, and ___________ (neurons/neuroglia)

diffusion, reuptake

examples of neurotransmitters

acetylcholine, norepinephrine, dopamine, serotonin, histamine, amino acids, polypeptides, gases

what are the two most important neurotransmitters studied in this lecture

acetylcholine and norepinephrine

A neurotransmitter that enables learning and memory and also triggers muscle contraction

acetylcholine

A neurotransmitter involved in arousal, as well as in learning and mood regulation

norepinephrine

A neurotransmitter associated with movement, attention and learning and the brain's pleasure and reward system.

dopamine

A neurotransmitter that affects mood, hunger, sleep, and arousal; linked to depression and treated by Prozac.

serotonin

a neurotransmitter that plays an important role in stimulating wakefulness

histamine

what are the two groups under amino acid neurotransmitters?

excitatory and inhibitory

examples of excitatory amino acids

glutamic acid and aspartic acid

examples of inhibitory amino acids

GABA (gamma-aminobutryric acid) and glycine

examples of polypeptides

glucagon, insulin, endogenous opioids

examples og gases

nitric oxide and carbon monoxide

Acetylcholine undergoes what type of signal transduction

ligand operated

what is the duration of acetylcholine receptor interaction

2 ms

acetyl coa + choline

acetylcholine

what makes up acetylcholine?

acetyl coa and choline

after diffusion out of the synapse, Ach breaks up into what

acetate and choline

after Ach breaks up, ____________ diffuses and gets removed while __________ is reuptaken

acetate, choline

what breaks down Ach

acetylcholinesterase

insecticides, zarin, zoman, and neuromuscular relaxants inhibits what

Ach E

norepinephrine undergoes what type of signal transduction

protein coupled

a class of enzymes that destroy the monoamines: dopamine, norepinephrine, and serotonin

MAO (monoamine oxidase)

norepinephrine goes into what structure in the synapse

mitochondria

when norepinephrine goes through the synapse, how many types of reuptake are there

two

which reuptake is used more with norepinephrine

reuptake I

_______________ --> l-dopa

tyrosine

tyrosine --> ______________ --> dopamine

l-dopa

l-dopa --> _________________ --> norepinephrine (in the nerve)

dopamine

dopamine --> ___________________ --> epinephrine (in adrenal gland)

norepinephrine

norepinephrine --> _________________

epinephrine