Chapter 2: Communication Within the Nervous System

Question 1

What is a neuron?

Answer 1

Cells that convey sensory info into the brain and carry operations and transmit commands to the body

Question 2

What is the structure of a neuron? (5 structures)

Answer 2

Soma (cell body), axon, dendrites, axon terminals, nucleus

Question 3

What are the three different types of neurons? What are their functions?

Answer 3

Motor neuron: carries commands to muscles and the organs
Sensory neuron: carry info from the body and outside world to brain/spinal cord
Interneuron: neurons that connect neurons to each other in the same part of the brain or spinal cord

Question 4

What are the two different types of sensory neurons?

Answer 4

Unipolar: dendrites and axon are on one side of the cell body
Bipolar: has two extension, dendrites on one side and then axon on the other side of the cell body

Question 5

What type of neuron is a motor neuron?

Answer 5

Multipolar (typical image of a neuron), with dendrites around the cell body and axon extends to the other side

Question 6

What is polarization and voltage?

Answer 6

Polarization is a state in which there is a difference in electrical charge between inside/outside of the neuron, and voltage is a measure of the difference in electrical charge between two points

Question 7

What is resting potential?

Answer 7

Difference in charge between the inside and outside of membrane of a neuron at rest

Question 8

What are the positive and negative ions that are involved in the neuron?

Answer 8

Positive: Na+ and K+
Negative: Cl- and A-

Question 9

What is the force that moves ions in the neuron?

Answer 9

Force of diffusion moves ions through a membrane to a less concentrated side

Question 10

What is electrostatic pressure?

Answer 10

Force where ions are repelled from similarly charged and attracted to oppositely charged

Question 11

What is the sodium potassium pump?

Answer 11

Large protein molecules that move sodium ions out of the cell and potassium ions back inside of the cell.

Question 12

What are three ways that ions can move across a cell membrane?

Answer 12

Force of diffusion, sodium potassium pump, electrostatic pressure

Question 13

What is an ion channel and the two ways it can be gated?

Answer 13

Gated pores in membrane formed by proteins that limit the flow of ions in and out of the cell
Chemically: neurotransmitters or hormones bind and cause channel opening
Electrically: Change in electrical potential of the membrane causes channel opening

Question 14

What is local potential, partial depolarization, and graded potential?

Answer 14

Local potential is the polarity in a specific area, partial depolarization is when the local potential of an area shifts towards 0, and graded potential is a potential that varies in magnitude with the strength of the stimulus that produced it

Question 15

Is local potential considered a graded potential?

Answer 15

YES

Question 16

What is depolarization?

Answer 16

When local potential exceeds the threshold for activating electrically gated channels, creating an action potential, the membrane potential becomes about +10 rather than the resting potential of -70

Question 17

What is an action potential?

Answer 17

Abrupt depolarization of membrane that allows neurons to communicate

Question 18

Is an action potential graded or ungraded? Why?

Answer 18

It is ungraded because an action potential is always the same strength and size, it abides by the all or none law (occurs at full strength or not at all

Question 19

What does it mean that an action potential is nondecremental?

Answer 19

It means that it travels down the axon with no decrease in strength as it travels, and it is propagated at each successive point along the way

Question 20

What is the absolute refractory period?

Answer 20

When sodium ion channels are unresponsive to further stimulation, no matter how intensive a new action potential cannot occur

Question 21

What is a relative refractory period?

Answer 21

Sodium ions could support another action potential but potassium channels are still open therefore the stimulation for a new action potential must overcome the charge

Question 22

What is rate law?

Answer 22

An axon encodes the stimulus intensity NOT in the size of its action but in its firing rate. Therefore you get stronger signal by firing many neurons/action potentials at once, not by how bid the action size is.

Question 23

What are glial cells?

Answer 23

Nonneuronal cells that provide many supporting functions to neurons in the CNS, and they help with conduction speed of action potentials

Question 24

What is myelin?

Answer 24

Fatty tissue that wraps around an axon to insulate it (gives the allusion that the axon is larger than it is therefore leading to faster conduction), they also keep cells separate from extracellular fluid and other neurons

Question 25

What are the Nodes of Ranvier?

Answer 25

Gaps in the myelin sheath that are important for saltatory conduction because they have an increased density of Na channels that allow action potentials to travel quicker

Question 26

What is saltatory conduction?

Answer 26

A form of transmission in which action potentials appear to jump from node to node

Question 27

What are three benefits of myelin sheath?

Answer 27

Reduces capacitance (increase speed of transmission therefore allowing for small neurons), signal regeneration at nodes of Ranvier (jumps), use less energy because there is a reduced need for Na/K pumps which take a lot of energy to make

Question 28

What are two different glial cells?

Answer 28

Oligodendrocytes and Schwann cells

Question 29

What are oligodendrocytes?

Answer 29

Type of glial cell which produce myelin in the brain and spinal cord (75% of brain glial cells are oligodendrocytes)

Question 30

What are Schwann cells? Where do they exist?

Answer 30

Glial cells that produce myelin for the rest of the nervous system (PNS). The exist between the nodes of Ranvier

Question 31

Does removing Schwann cells or oligodendrocytes have a more detrimental effect on the body and why?

Answer 31

Oligodendrocyte damage has a more detrimental effect because they exist between many neurons to anchor them to each other where as Schwann cells exist in one myelin.

Question 32

Which glial cells form scaffolds during fetal development that guide new neurons to their destinations?

Answer 32

Radial Glia

Question 33

What do microglia do?

Answer 33

Provide energy

Question 34

What are astrocytes and their function?

Answer 34

Type of glial cell that triggers the formation of seven times as many connections as neurons. Larger and more complex astrocytes correlates with more complex functions

Question 35

What are the two types of receptors at the post synaptic membrane?

Answer 35

ionotropic and metabotropic

Question 36

How do ionotropic receptors work?

Answer 36

They are receptors that form an ion channel, they open quickly to produce the immediate reactions once a NT binds to the channel, mostly found in the sensory system

Question 37

How to metabotropic receptors work?

Answer 37

They are receptors that open channels indirectly through a second messenger, once a NT binds a second messengers detaches and causes a separate ion channel to open. These are slower and play a role in LTP and LTD

Question 38

What is partial depolarization?

Answer 38

Depolarization that is excitatory and facilitates the occurrence of an action potential. NT triggers opening of Na+ channels but not enough to trigger an action potentia

Question 39

What is hyperpolarization?

Answer 39

Increased polarization which is inhibitory and makes an action potential less likely to occur (K+ flows out and makes neurons more -)

Question 40

What does EPSP stand for and what is it?

Answer 40

Excitatory postsynaptic potential. When receptors open sodium channels to produce a partial depolarization of the dendrites and cell body.

Question 41

What does IPSP stand for and what is it?

Answer 41

Inhibitory postsynaptic potential. When receptors open K+, Cl- or both to produce a hyperpolarization of the dendrites and cell body.

Question 42

What are the two types of postsynaptic integration?

Answer 42

Spatial summation and temporal summation

Question 43

What is spatial summation?

Answer 43

Combines potentials occurring simultaneously at different locations on the dendrites and cell body

Question 44

What is temporal summation?

Answer 44

Combines potentials arriving a short time apart, from either the same or separate inputs

Question 45

How are neurotransmitters removed from the synapse?

Answer 45

Via reuptake. Transmitters are taken back up into the presynaptic terminals by transporter proteins where they are repackaged into vesicles for reuse. They become toxic if they are in there for two long

Question 46

What is presynaptic excitation?

Answer 46

Increases the presynaptic neuron’s release of neurotransmitters onto the postsynaptic neuron (via a third cell)

Question 47

What is presynaptic inhibition?

Answer 47

Decreases the presynaptic neuron’s release of neurotransmitters onto the postsynaptic neurons (via third cell)

Question 48

What is axo-axonic synapse?

Answer 48

The interaction between the third cell with presynaptic neuron

Question 49

What are autoreceptors?

Answer 49

Receptors on presynaptic terminals which sense the amount of transmitters in the cleft

Question 50

What is Dale’s principle? Is this true or false?

Answer 50

Erroneous belief that a neuron was capable of releasing only a single transmitter. FALSE

Question 51

What are the three ways that neurotransmitters are released?

Answer 51

Corelease, cotransmission, release of different transmitters from different terminals

Question 52

What is corelease?

Answer 52

Also known as partial vesicle opening, each vesicle contains both types of NT and therefore both get released, depending on the stimulus a vesicle may be able to partially open and release only one

Question 53

What are the two types of cotransmission?

Answer 53

1. Differential Ca+ sensitivity: each NT has its own vesicles and depending on the stimulus only one gets released
2. Spatial segregation: 2 axon terminals paired together at all times, each with their own NT