Chapter 48: Neurons, Synapses, and Signaling

Question 1

Neurons

Answer 1

• Nerve cells
• Transfer information within the body
• Long and short-distance electrical signals
• Receive, transmit, and regulate flow of information

Question 2

Brain

Answer 2

Groups of neurons that sort neuronal paths and connections

Question 3

Ganglia

Answer 3

Simpler clusters of neurons

Question 4

Cell Body

Answer 4

Where most of a neuron’s organelles are located

Question 5

Dendrites

Answer 5

Branched extensions of a neuron

Question 6

Axon

Answer 6

• Each neuron has one
• Extension that transmits signals to other cells
• Much longer than dendrites

Question 7

Synapse

Answer 7

Junction that receives transmitted information from the branched end of an axon

Question 8

Neurotransmitters

Answer 8

• Chemical messengers

- Pass information from a transmitting neuron to a receiving cell at synapses

Question 9

Glial Cells/Glia

Answer 9

• Supporting cells
• Nourish neurons
• Insulate axons of neurons
• Regulate extracellular fluid surrounding neurons
• Replenish certain groups of neurons and transmit information
• There are more of them than neurons

Question 10

Sensory Neurons

Answer 10

Transmit info about an external stimuli (i.e. light, touch, smell, or internal conditions like blood pressure)

Question 11

Interneurons

Answer 11

• Most of the neurons in the brain

- Form local circuits connecting neurons in the brain

Question 12

Motor Neurons

Answer 12

Transmit signals causing muscle cells to contract

Question 13

Central Nervous System (CNS)

Answer 13

• In many animals
• Organization of neurons that carry out integration
• Brain and spinal cord

Question 14

Peripheral Nervous System (PNS)

Answer 14

Neurons that carry information in and out of the central nervous system

Question 15

Nerves

Answer 15

Bundles of axons of neurons

Question 16

Membrane Potential

Answer 16

Charge difference/voltage because of potential energy from the attraction of opposite charges across the membrane

Question 17

Resting Potential

Answer 17

• Membrane potential of a neuron that isn’t sending a signal

- Usually -60 to -80 mV (millivolts)

Question 18

Sodium-Potassium Pump

Answer 18

• Actively transports K+ in the cell and Na+ out

- Maintains K+ and Na+ gradients

Question 19

Ion Channels

Answer 19

Pores formed by clusters of specialized proteins across the membrane

Question 20

Equilibrium Potential (Eion)

Answer 20

• Magnitude of membrane voltage at equilibrium for a particular ion
• Can be calculated with Nernst equation

Question 21

Gated Ion Channels

Answer 21

• Ion channels that open/close in response to stimuli

- Opening/closing alters membrane’s permeability to ions and therefore alters potential

Question 22

Hyperpolarization

Answer 22

Ions flow across the membrane, increasing magnitude of membrane potential

Question 23

Depolarization

Answer 23

• Reduction in the magnitude of membrane potential

- Often involves gated sodium channels

Question 24

Graded Potential

Answer 24

• Shift in membrane potential
• Magnitude that varies with the strength of the stimulus (larger stimulus causes a greater change in membrane potential)
• Decays with time and distance from source

Question 25

Action Potential

Answer 25

• Massive change in membrane voltage
• Have constant magnitude and can regenerate in adjacent regions of the membrane
• Good for long distance signal transmission

Question 26

Voltage-Gated Ion Channels

Answer 26

Open/close when membrane potential passes a particular level

Question 27

Threshold

Answer 27

• Particular value that depolarization increases membrane voltage to
• In mammalian neurons it’s about -55 mV

Question 28

Refractory Period

Answer 28

Time when the second activation potential cannot be initiated (caused by inactivation of sodium channels)

Question 29

Myelin Sheath

Answer 29

Electrical Insulation that surrounds vertebrate axons

Question 30

Oligodendrocytes

Answer 30

• Produce myelin sheaths

- In the central nervous system

Question 31

Schwann Cells

Answer 31

• Produce myelin sheaths

- In the peripheral nervous system

Question 32

Nodes of Ranvier

Answer 32

Gaps in the myelin sheath

Question 33

Saltatory Conduction

Answer 33

• Mechanism for propagating action potentials

- Action appears to leap from node to node