Communication within the Nervous Service

Question 1

What is the nervous system made of?

Answer 1

• Neuroscientist Santiago Ramon y Cajal identified that the nervous system was composed of distinct cells using various strains
  ~ Nissl stain: only labels cell bodies
  ~ Golgi stain: labels cell bodies AND dendrites/axons
• “The Neuron Doctrine”

Question 2

What are the 3 main parts of a neuron?

Answer 2

dendrites, soma (cell body), and axon

Question 3

What are dendrites?

Answer 3

• receive signals from other neurons

Question 4

What is a soma (cell body)?

Answer 4

• contains normal cellular stuff (nucleus, etc)

Question 5

What are axons?

Answer 5

• transmit (sends) signals to other neurons

Question 6

What is unipolar?

Answer 6

• contains one axon

Question 7

What is bipolar?

Answer 7

• contains one axon and one dendrite

Question 8

What is multipolar?

Answer 8

• contains one axon and multiple dendrites

Question 9

Sensory neurons

Answer 9

• directly receive information from the world around us

Question 10

Interneurons

Answer 10

• the “middleman”
• processes incoming sensory information and plans/executes the response

Question 11

Motor neurons

Answer 11

• connects to muscles and leads to movements/behaviors

Question 12

Other types of neurons

Answer 12

• pyramidal and stellate neurons

Question 13

What are the two types of signals in the nervous system ?

Answer 13

electrical and chemical

Question 14

What does electrical signals do?

Answer 14

• action potentials
• typically used within a neuron ~ one side to another

Question 15

What does chemical signals do?

Answer 15

• neurotransmitters
• typically used between neurons

Question 16

What are the main players in the electrical signal?

Answer 16

• Ions (something that has a charge)
  ~ Sodium (Na+)
  ~ Potassium (K+)
  ~ Chloride (A-)
• other anions (A-)

Question 17

A cell at rest, what is the cell membrane?

Answer 17

• it is a fence with gates around the cell
• gates in cell membrane are called channels

Question 18

A cell at rest, what is it resting potential?

Answer 18

• a voltage difference between the inside and outside of the neuron
  ~ - 70 mV, will always be negative in the inside

Question 19

What are the two main forces at work with resting potential?

Answer 19

• concentration gradient (more goes to less)
• electrostatic force (opposites attract, like charges repel)

Question 20

What is the starting arrangement in resting potential?

Answer 20

• Na+ is outside
• Cl- is outside
• K+ is inside
• A- is inside

Question 21

What does the stimulus do when at rest?*

Answer 21

• opens Na+ channels
• Excitatory Post- Synaptic Potential (EPSP)
• Na+ enters the cell

Question 22

What is threshold?

Answer 22

• usually set at approximately -55mV
• action potentials are all or none
• once it reaches threshold, an action potential is guaranteed

Question 23

What are voltage gated channels?

Answer 23

• triggered by a change in voltage
• Na+ channels open and Na+ floods the cell called depolarization

Question 24

When at the peak, how does K+ feel?

Answer 24

• Na+ channels close
• K+ channels open and leaves the cell called repolarization
• it overshoots the -70 mV resting potential called hyperpolarization

Question 25

What happens when the cell is getting back to rest?

Answer 25

- the Na+/K+ pumps 3 Na out and 2 k in - helps to "reset" conditions to the original resting potential state so that the neuron can have another action potential

Question 26

What are the three other parts of an axon?

Answer 26

1) axon hillock 2) Myelin Sheath 3) Nodes of Ranvier

Question 27

What does the axon hillock do?

Answer 27

- the beginning of the axon - where the action potential begins

Question 28

What does the Myelin Sheath do?

Answer 28

- fatty tissue for insulation

Question 29

What does the Nodes of Ranvier do?

Answer 29

- breaks in the myelin (VERY important)

Question 30

What does the saltatory conduction do?

Answer 30

- impulse moves down the axon - passively moves through myelinated axons - regenerated at the voltage channels in each node of Ranvier

Question 31

What is at the end of an axon?

Answer 31

- terminal buttons

Question 32

What is terminal buttons?

Answer 32

- contain vesicles of neurotransmitters - when the action potential arrives at the end of the axon, Ca2+ is released Ca2+ leads to exocytosis of the vesicles

Question 33

What happens in the synapse?

Answer 33

- neurotransmitters cross the synaptic gap and bind to channels on receiving neuron dendrites ~ ligand gated channels - if the input is enough to reach threshold, the process repeats

Question 34

What does the neurotransmitter also do?

Answer 34

- instead of opening Na+ channels, neurotransmitters can also open K+ or Cl- channels - brings the voltage of the receiving neuron further away from threshold called an Inhibitory Post-Synaptic Potential (IPSP)

Question 35

What is Temporal Summation?

Answer 35

- the combination of postsynaptic events that leads to an action potential or not - each receiving neuron receives input from multiple presynaptic neurons - if one synaptic is repeatedly stimulated, that can get the receiving neuron passed threshold

Question 36

What is Spatial Summation?

Answer 36

- if multiple synapses together stimulate a neuron, the combination of them can get the receiving neuron passed threshold

Question 37

What are Ionotropic receptors?

Answer 37

- single step receptor - fast acting - neurotransmitter binds and opens channel - ions flow through the open channel

Question 38

What are Metabotropic receptors?

Answer 38

- multi- step receptors - slow acting - uses second messengers ~ longer lasting impacts than ionotropic receptors