Biopsychology Chapter 4

Front 1

The Ionic Basis of the Resting Membrane Potential
When intracellular and extracellular electrodes are outside a neuron, the difference between the electrical potentials at their tips is _____; when the intracellular electrode penetrate the neuron, the potential jumps to about _____. This is the _____ of the neuron.

Back 1

Zero
-70 millivolts
Resting Potential

Front 2

The resting potential exists because positively and negatively charged ions are distributed unequally on the two sides of the neural membrane; the concentration of _____ and _____ are higher outside the neuron, and the concentration of _____ and various negatively charged _____ are higher inside the neuron.

Back 2

Na+ and Cl-
K+
Protiens

Front 3

Describe Random Motion (passive)

Back 3

*Ions in solution are in random motion
*Thus, any time there is an accumulation of a particular class of ions in one area, the probability is increased that random motion will move ions out of this area (because there are more ions available to leave) and the probability is decreased that random motion will move more ions into this area (because there are fewer ions available to come in).

Front 4

Electrostatic Pressure (passive)
_____ and _____; therefore, electrostatic pressure disperses any accumulation of positive or negative charges in an area.

Back 4

Like charges repel and opposite charges attract

Front 5

Differential Permeability of the Membrane (passive)
Ions pass through the cell membrane at special pores called _____.

Back 5

Ion channels

Front 6

Describe Sodium-Potassioum Pumps (active)

Back 6

Active (energy-comsuming) mechanisms in the neural membrane continuously transfer Na+ ions out of the neuron and K+ ions in.
This occurs at a ratio of 3 Na+ ions moved out for every 2 K+ ions moved in; thus, there is a loss of one positive charge every time the pump.

Front 7

______ how electrical signals are created in a resting neuron.

Back 7

Postsynaptic potential

Front 8

Postsynaptic potentials are changes in the membrane potential produced by the action of _____ released by _____.

Back 8

Neurotransmitters
Presynaptic neurons

Front 9

_____ are _____; they increase the likelihood that a neuron will fire.

Back 9

Excitatory postsynaptic potentials (EPSP)
Depolarized

Front 10

_____ are _____; they decrease the likelihood that that a neuron will fire.

Back 10

Inhibitory postsynaptic potentials (IPSP)
Hyperpolarizations

Front 11

They are _____: Like electricity through a cable, so rapidly that transmission is usually regarded as being instantaneous.

Back 11

Transmitted rapidly

Front 12

_____ (AP; neuron firing) are triggered at the _____ when a neuron is depolarized to the point that the membrane potential at the axon hillock reaches about _____mV the _____ for many neurons.

Back 12

Action Potential
Axon hillock
-65
Threshold of excitation

Front 13

Unlike EPSPs and IPSPs, APs are _____; they are _____ (full-blown or not at all).
Most neurons receive hundred of synaptic contacts--what happens at any one synapse has very little effect on the firing of the neuron. Whether or not a neuron fires is determined by the integration of what goes on at many neurons.

Back 13

Not graded
All-or-none

Front 14

When the threshold of excitation (about -65mV) is reached, _____ open momentarily, and Na+ ions rush int the neuron under tremendous pressure from their concentration and electrostatic gradients. This drives the membrane potential to about +50mV.

Back 14

Voltage-gated Na+ channels

Front 15

At the same time, _____ slowly begin to open. Most of these channels open at about the time that the membrane potential is about +50mV. At this point, K+ ions. are driven out by the +50mV charge and their high internal concentration; this repolarizes the neuron and leaves it slightly ______ for a few milliseconds.

Back 15

Voltage-gated K+ channels
Hyperpolarized

Front 16

Many axons are myelinated by _____ in the CNS and by _____ in the PNS; myelination insulates the semipermeable axon membrane, blocking the flow of ions through the axon at all but the _____; paradoxically, this actually improves transmission.

Back 16

Oligodendroglia
Schwann cells
Nodes of Ranvier

Front 17

In myelinated axons, APs travel passively (decrementally and rapidly) between the nodes of Ranvier; but at each node, there is a "pause" while a full-blown AP is generated.
This is called _____.

Back 17

Saltatory conduction ("saltatory" means to skip or jump)

Front 18

There are two main types of neurotransmitters; _____, synthesized in the cytoplasm and packed into ____ by the _____;
and _____, synthesized in the soma by _____ and then moved down to the terminals by _____.

Back 18

Small-molecule transmitters
vesicles
Golgi complex
Large-molecule transmitters
Ribosomes
Microtubes

Front 19

The arrival of an AP at a terminal button opens ____ in the button membrane and Ca++ ions enter the button.

Back 19

Voltage-gated calcium channels

Front 20

The entry of the Ca++ ions causes the synaptic vesicles to fuse with the _____ and empty their contents into the _____ - a process called ______.

Back 20

Presynaptic membrane
Synaptic cleft
Exocytosis

Front 21

After its release, neurotransmitters diffuse across the synaptic cleft to the ______; there it binds to _____ in the postsynaptic membrane. Specific receptors for each neurotransmitter.

Back 21

Post-synaptic membrane
Receptors

Front 22

Neurotransmitters can act at an _____ directly associated with a channel in the postsynaptic membrane and induce brief EPSPs or IPSPs.

Back 22

Ionotropic Receptor

Front 23

Neurotransmitters can act at a _____ associated with a signal protein that is attached to a _____ inside the neuron. _____ can have more enduring and far reaching effects on the sensitivity of the neuron.

Back 23

Metabotropic Receptor
G-protien
Second messengers

Front 24

Neurotransmitters can be deactivated in the synapse by one of two mechanisms:
*??????
*??????

Back 24

*Some neurotransmitters are broken down int the synapse by enzymes.
*Other neurotransmitters are deactivated by reuptake into the presynaptic neuron, where they are recycled.

Front 25

Amino Acid Neurotransmitters
Individual building blocks of proteins. There is conclusive evidence that _____, _____, ______, and _____ are neurotransmitters.

Back 25

Aspartate, Glutamate, Glycine, and Gamma-Aminobutyric Acid (GABA)

Aspartate, Glutamate, and Glycine come from proteins that we eat; GABA is synthesized from glutamate.

Front 26

There are four _____ and they belong to one of ____.

Back 26

Monoamine neurotransmitters
Two subclasses
*Catecholamine
*Indolamine

Front 27

What are the different catecholamine neurotransmitters and how are they synthesized?

Back 27

Catecholamine neurotransmitters: Epinephrine, Dopamine, Norepinephrine; all 3 are synthesized from the amino acid Tyrosine, and tyrosine is converted to L-Dopa, to Epinephrine, Dopamine, Norepinephrine.

Front 28

What are the different Indolamine neurotransmitters and how are they synthesized?

Back 28

Indolamine neurotransmitter: Serotonin; synthesized from Tryptophan.