Chapter 48: Neurons synapses and signaling

Question 1

Presynaptic cell

Answer 1

The part which sends out an electric signal, always a neuron

Question 2

Postsynaptic cell

Answer 2

The cell that receives the electric signal

Question 3

Membrane potential

Answer 3

The electric charge of a membrane

Question 4

Resting potential

Answer 4

The base electric charge of a neuron before it is messed up

Question 5

Hyperpolarization

Answer 5

Cell becomes more negative

Question 6

Depolarization

Answer 6

Cell becomes more positive

Question 7

Threshold

Answer 7

The amount of depolarization that needs to happen for an action potential to occur

Question 8

Refractory period

Answer 8

The period in between action potentials where the neuron cannot activate another action potential

Question 9

Myelin sheath

Answer 9

Part of the PNS, surrounds a neuron so that signals can jump through neurons faster

Question 10

Nodes of ravier

Answer 10

Gaps between the myelin sheath’s where the action potential needs to regenerate itself

Question 11

Synaptic vesicle

Answer 11

a vesicle for neurotransmitters

Question 12

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

Answer 12

Sensory input, integration, motor output

Question 13

What parts make up the central nervous system (CNS) and what do they do? What parts make up the peripheral nervous system (PNS) and what do they do?

Answer 13

CNS: Brain and spinal chord
PNS: Nerves and everything else in the nervous system, brings in info and sends out response

Question 14

What is the anatomy of a neuron?

Answer 14

Several dendrites (postsynaptic neurons, receive info), one axon (presynaptic neuron, sends out info), axon hillock (just before axon, where all signals are sent to start action potential) and a soma (main body of neuron)

Question 15

What is a synapse?

Answer 15

The connection between a neuron and another cell (neuron or general body cell)

Question 16

What is a neurotransmitter?

Answer 16

A hormone released by the axon to a cell, diffuses over a short distance

Question 17

What are glia? What is their function?

Answer 17

Glial cells function in supporting the neurons in various different ways

Question 18

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

Answer 18

Outside: More Na+, less K+
Inside: Less Na+, more K+

Question 19

What is an ion channel?

Answer 19

A channel that can open or close to let only certain ions through

Question 20

What is meant by the term selective permeability?

Answer 20

Only certain molecules can pass through a membrane

Question 21

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

Answer 21

Maintained by sodium-potassium pumps which use ATP (energy) to make sure that Sodium stays out and potassium stays in unless they need to move. The neuron also has a lot of open potassium ion channels, letting potassium out because many anions get in, so the neuron wants to keep itself negative

Question 22

What two factors contribute to the equilibrium potential?

Answer 22

The concentration gradient of ions and the membrane permeability to certain ions

Question 23

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

Answer 23

Because it has more K+ inside it

Question 24

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

Answer 24

Gated ion channel: Can be opened by the cell to let certain ions in or out
Voltage gated ion channel: Can be opened using electricity to let certain ions in or out

Question 25

What is a graded potential?

Answer 25

A change in the membrane's potential

Question 26

What is an action potential and how is it generated?

Answer 26

It is a reaction by the cell caused by a depolarization which opens more sodium channels causing even more depolarization, causing a rapid surge in potential

Question 27

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

Answer 27

Positive feedback loop

Question 28

What is meant by the statement that an action potential is an all-or-none response?

Answer 28

The action potential either happens or it doesn't, either there is enough depolarization to cause it or there is not

Question 29

If an action potential is an all-or-none response, how can action potentials convey information concerning the strength of the stimulus that generated them?

Answer 29

More action potentials over a period of time means stronger stimuli

Question 30

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

Answer 30

1. Both sodium and potassium gated ion channels are closed 2. A stimulus opens some sodium channels, causing sodium to flow in, causing depolarization of the membrane, if that depolarization is enough then an action potential is reached 3. A lot of sodium keeps flowing in while potassium gated ion channels are still closed 4. Most sodium channels become inactive, blocking sodium from coming in, most potassium channels open which lets potassium leave, making the cell more negative 5. Sodium channels close, potassium channels start to close as they bring membrane back to resting potential

Question 31

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

Answer 31

Because then an action potential cannot travel backwards

Question 32

What causes the “undershoot” of the action potential?

Answer 32

Letting out too much potassium

Question 33

What happens to the cell membrane just behind the propagating action potential?

Answer 33

It enters the refractory period

Question 34

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

Answer 34

The bigger the diameter the more speed an action potential will have

Question 35

What is the effect of myelination on the speed of conductance of an action potential? What causes this effect?

Answer 35

The more myelinated a neuron is the faster it will travel down the axon, this is caused by saltatory conduction

Question 36

What is saltatory conduction?

Answer 36

The action potential "jumping" through the myelinated areas of the axon so it does not have to regenerate itself at every step of its journey

Question 37

What are postsynaptic potentials?

Answer 37

A change in the polarization of a postsynaptic cell, lots of postsynaptic potentials can cause an action potential

Question 38

How does an EPSP differ from an IPSP?

Answer 38

EPSP: Depolarizes the postsynaptic membrane, making it more likely for an action potential to occur IPSP: Hyperpolarizes the postsynaptic membrane, making it more likely for an action potential to occur

Question 39

What is temporal summation?

Answer 39

Signals add together because they are received close together in time in the same presynaptic neuron

Question 40

What is spatial summation?

Answer 40

Two signals add together in time and are from two different presynaptic neurons

Question 41

The summed effect of IPSPs and EPSPs at the ________________ will produce an action potential if ________________ is reached

Answer 41

Axon hillock, threshold

Question 42

What class of neurotransmitter is common in both invertebrates and vertebrates and is usually excitatory?

Answer 42

Acetylcholine

Question 43

What three amino acids are major neurotransmitters in the central nervous system?

Answer 43

GABA: Increases permeability of chloride ions Glutamate: Works on the muscles of vertebrates, long term memory of invertebrates Glycine: Found in the spinal cord

Question 44

Which class of neurotransmitter includes epinephrine and serotonin?

Answer 44

Biogenic amines, which are a chain of amino acids

Question 45

Which class of neurotransmitter includes NO and CO?

Answer 45

Gases

Question 46

What are relatively short chains of amino acids that function as neurotransmitters?

Answer 46

Neuropeptides, Substance P and endorphins