Neurons And Synapses

Front 1

Presynaptic cell

Back 1

A neuron, sends information to a postsynaptic cell

Front 2

Postsynaptic cell:

Back 2

A neuron, muscle, or gland cell that receive the information sent by the presynaptic cell

Front 3

Membrane potential:

Back 3

A voltage (difference in electrical charge) across their plasma membrane

Front 4

Resting potential:

Back 4

The membrane potential of a resting neuron, a neuron that is not sending signals (-60 to -80 mV). Neuron has positive charge outside cell and negative inside cytoplasm due to large negative proteins. There is a higher concentration of potassium inside the cell and a higher concentration of sodium outside the cell. There are more potassium channels than sodium channels into the cell, and the sodium-potassium pump takes in some potassium but sends out more sodium. This maintains the polarity of the membrane.

Front 5

Hyperpolarization:

Back 5

Increase in magnitude of the membrane potential that results from a stimulus increasing either the outflow of positive ions or the inflow of negative ions. This causes the inside of the membrane to become more negative and the outside to become more positive, thus increasing the polarity of the membrane.

Front 6

Depolarization:

Back 6

Decrease in magnitude of the membrane potential that results from opening ion channels that decrease the polarity of the membrane.

Front 7

Threshold:

Back 7

The potential that an excitable cell membrane must reach for an action potential to be initiated

Front 8

Refractory period:

Back 8

Temporary inactivation of Na+ channels during the falling phase and early part of the undershoot that prevents the initiation of a second action potential.

Front 9

Myelin sheath:

Back 9

Insulation of axons in vertebrate neurons, increases action potential’s speed, produced by oligodendrocytes in the CNS and Schwann cells in the PNS

Front 10

Nodes of Ranvier:

Back 10

Gaps in the myelin sheath with voltage-gated sodium channels, where action potential’s can form

Front 11

Synaptic vesicle:

Back 11

Packages containing neurotransmitters, located in the synaptic terminal

Front 12

What are the three stages of information processing in the nervous system?

Back 12

1. Sensory input: Sensors detect stimuli, transmit info. along sensory neurons
2. Integration: Interneurons in brain or ganglia integrate the information
3. Motor output: Output message leaves brain or ganglia via motor neurons and triggers muscle or gland activity

Front 13

What parts comprise the central nervous system (CNS)? peripheral nervous system (PNS)?

Back 13

CNS: Brain and cord
PNS: Everything else

Front 14

Know the anatomy of a neuron

Back 14

KNOW IT!!!!!!! :D

Front 15

What is a synapse?

Back 15

Junction between an axon and another cell

Front 16

What is a neurotransmitter?

Back 16

Chemical messenger released by presynaptic neurons that diffuses across the synapse to bind with receptors on the postsynaptic cell.

Front 17

What is glia? What is their function?

Back 17

Glia are cells that nourish and insulate neurons and regulate extracellular fluid around neurons. Glia far outnumber neurons

Front 18

How do the concentrations of K+ and Na+ differ inside and outside the cell?

Back 18

Outside: There is a greater concentration of Na+ ions. The Na+ channels on the membrane are mostly closed (at resting potential)
Inside: There is a greater concentration of K+ ions. Many K+ channels are open (at resting potential)

Front 19

What is an ion channel?

Back 19

A pore in the membrane that allows ions to diffuse back and forth across the membrane. They have selective permeability.

Front 20

What is meant by the term selective permeability?

Back 20

Only certain ions may pass through a particular channel

Front 21

What properties of the cell membrane are responsible for producing the resting potential?

Back 21

Many K+ channels are open, allowing potassium to diffuse in and out of the membrane. Very few sodium channels are open, keeping Na+ outside the cell. Sodium-potassium pumps work to maintain the potassium and sodium gradients across the plasma membrane. There is a positive charge outside the cell and a negative charge inside the cell due to large, negative proteins.

Front 22

What two factors contribute to the equilibrium potential?

Back 22

Equilibrium potential is the membrane voltage for a particular ion at equilibrium. The equilibrium potential of K+ is negative, while Na+ is positive. This is based on the chemical and electrical gradients.

Front 23

Why is the membrane potential of a resting cell closer to the K+ equilibrium potential than the Na+ equilibrium potential?

Back 23

The concentration of K+ is higher inside the cell, which causes a favorable chemical gradient for K+. This creates many open potassium channels but only a small number of open sodium channels.

Front 24

What is a gated ion channel? a voltage-gated ion channel?

Back 24

Gated ion channel: Ion channels that open or close in response to stimuli
Voltage-gated ion channel: Ion channels that open or close in response to a change in membrane potential.

Front 25

What is a graded potential?

Back 25

A change in polarization where the magnitude of the change varies with the strength of the stimulus.

Front 26

What is an action potential (AP) and how is it generated?

Back 26

A massive change in membrane voltage. It is the nerve impulse, or signal, that carries information along an axon. It is generated by depolarization (opened sodium channels) in the membrane. If the membrane potentiation goes past the threshold, the rise of the action potential (an increased number of open sodium channels, causing the inside of the cell to become positive) begins. Once it reaches a certain point, the sodium channels close and the potassium channels open, causing the fall of the membrane potential to the eventual undershoot (below resting potential). Sodium-potassium pumps work to bring the cell back to resting potentional.

Front 27

What type of feedback loop best describes the depolarization and channel opening associated with an AP?

Back 27

Positive feedbackDepolarization opens voltage-gated sodium channels, and these open channels cause further depolarization.

Front 28

What is meant by the statement that an AP is an all or none response?

Back 28

Action potentials occur fully or not at all. Once started, the AP is independent of the strength of the stimulus, it merely requires a certain strength of stimulus to begin.

Front 29

If an AP is an all or none response how can it convey information concerning the strength of the stimulus that generated it?

Back 29

The frequency. A stronger stimulus means a higher frequency.

Front 30

Know the stages of an AP and the changes in the state of the ion channels that contribute to each stage.

Back 30

Resting state: Gated Na+ and K+ channels closed. Ungated channels, mostly K+, maintain resting potential. Inside of membrane negative with respect to outside.
Depolarization: Stimulus opens Na+ channels. If threshold is reached, rising phase begins
Rising phase of the AP: Depolarization opens most Na+ channels, K+ channels closed. Inside of membrane is now positive with respect to outside.
Falling phase of the AP: Na+ channels inactivated, K+ channels open. Inside of membrane is now negative with respect to outside.
Undershoot: Na+ channels close, some K+ still open. Membrane returns to resting state as K+ channels close and Na+ become unblocked

Front 31

Why is the inactivation of voltage-gated Na+ channels important for the unidirectional transmission of an AP?

Back 31

Action potential is propelled by a process of depolarization-repolarization. As AP moves, it depolarizes the neighboring region. The inactivation of Na+ behind the zone of depolarization prevents the AP from going backwards.

Front 32

What causes the “undershoot” of the AP?

Back 32

The undershoot is caused by the closing of sodium channels and the opening of potassium channels. This keeps sodium out of the cell but also allows potassium to exit the cell. This shoots the membrane potential past its resting state, known as the undershoot. Then some of the potassium channels close and some of the sodium channels are unblocked, allowing the membrane to return to its resting state.

Front 33

What happens to the cell membrane just behind the propagating AP?

Back 33

The membrane behind the AP is repolarized. The sodium channels are inactivated, allowing the AP to continue forward, while the potassium channels are open to allow outflow of K+ which repolarizes the membrane.

Front 34

What is the relationship between the speed of conductance of an AP and the axon diameter?

Back 34

The speed of an AP increases with the axon diameter. (Ex. Water hose)

Front 35

What is the effect of myelination on the speed of conductance of an AP?

Back 35

Myelination increases the speed of AP. It provides electrical insulation for the axon, and causes the depolarizing current from AP to spread farther along the interior of the axon, bringing more distant regions of the membrane to the threshold sooner (same effect as wider axon)

Front 36

What is the mechanism involved in question 25?

Back 36

Saltatory conduction

Front 37

What is saltatory conduction?

Back 37

AP in myelinated axons jump between the nodes of Ranvier.

Front 38

What are postsynaptic potentials?

Back 38

A change in the membrane potential of the postsynaptic cell. It is graded, not all or none.

Front 39

How does an EPSP differ from an IPSP?

Back 39

Excitatory postsynaptic potential: Depolarization that bring the membrane potential toward threshold
Inhibitory postsynaptic potential: Hyperpolarization that move the membrane potential farther from the threshold

Front 40

What is temporal summation?

Back 40

When two EPSPs/IPSPs are produced in rapid succession from a single synapse and then combine.

Front 41

What is spatial summation?

Back 41

EPSPs/IPSPs that are produced by different synapses almost simultaneously but also combine.

Front 42

The summed effect of IPSPs and EPSPs at the ?????????(the neuron’s integrating center) will produce an AP if ???????? is reached.

Back 42

axon hillock, threshold

Front 43

This class of neurotransmitter is common in both invertebrates and vertebrates and is usually excitatory.

Back 43

Acetylcholine

Front 44

These two amino acids are major neurotransmitters in the CNS.

Back 44

Gamma-aminobutyric acid (GABA) (excitatory) and glutamate (inhibitory)

Front 45

This class of neurotransmitter includes epinephrine and serotonin

Back 45

Biogenic amines: epinephrine, serotonin, norepinephrine, dopamine

Front 46

This class of neurotransmitter includes NO and CO

Back 46

Gases: local regulators in the PNS, nitric oxide and carbon monoxide

Front 47

These are relatively short chains of amino acids that function as neurotransmitters.

Back 47

Neuropeptides: includes substance P and endorphins, both affect pain perception