Chapter 2 - Neurons and Action Potentials

Question 1

neurons

Answer 1

cells in nervous system that receive and transmit information

Question 2

how many neuwons does the human brain contain? (estimate)

Answer 2

100 billion neurons

Question 3

santiago ramon y cajal

Answer 3

developed staining techniques to show a small gap separates the tips of one neurons fibers from the surface of the next neuron.

Question 4

membrane

Answer 4

the surface of a cell that separates the inside of the cell from the outside environment

Question 5

what is the cell membrane composed of?

Answer 5

two layers of fat molecules.

Question 6

what chemicals can cross the membrane with the aid of a pump?

Answer 6

water, oxygen, sodium, potassium, calcium, chloride, and others

Question 7

nucleus

Answer 7

structure in the cell that contains the chromosomes

Question 8

mitochondrion (pl: mitochondria)

Answer 8

structure that performs metabolic activities

Question 9

ribosomes

Answer 9

sites at which the cell synthesizes new protein molecules

Question 10

endoplasmic reticulum

Answer 10

transports newly synthesized proteins to other locations. sometimes have ribosomes attached.

Question 11

motor neuron

Answer 11

soma in spinal cord. conducts impulses along its axon to a muscle

Question 12

sensory neuron

Answer 12

specialized at one end to be highly sensitive to a particular stimuli (i.e. light, sound or touch)

Question 13

dendrites

Answer 13

branching fibers that receive information from other neurons

Question 14

dendritic spines

Answer 14

short outgrowths that increase the surface area available for synapses

Question 15

soma / cell body

Answer 15

contains nucleus, ribosomes & mitochondria. most of metabolic work occurs here

Question 16

axon

Answer 16

thin fiber, sends information to other neurons, organs, or muscles.

Question 17

myelin sheath

Answer 17

insulation of axons in most vetebrates

Question 18

nodes of ranvier

Answer 18

interruptions of myelin sheath which help transmit signals faster down the axon

Question 19

presynaptic terminal / end bulb / bouton

Answer 19

point from which the axon releases chemicals that cross the junction to another neuron

Question 20

afferent axon

Answer 20

brings information into the structure (approach)

every sensory neuron is afferent

Question 21

efferent exon

Answer 21

carries information away from the structure (exit)

every nomtor neuron is efferent

Question 22

interneuron / intrinsic neuron

Answer 22

neuron with dendrites and axon entirely contained in a single structure

Question 23

glia

Answer 23

more numerous than neurons

astrocytes
microglia
oligodendrocytes
schwann cells
radial glia

Question 24

astrocytes

Answer 24

star shaped. help synchronize activity of axons to ehable messages in waves. also remove waste material. dialate blood vessels to bring more nutrients into an area of hightened brain activity.

Question 25

glutamate

Answer 25

transmitter used by neurons to communicate

Question 26

microglia

Answer 26

very small cells. remove waste material, viruses, fungi and other microorganisims.

Question 27

oligodendrocytes

Answer 27

build myelin sheath in central nervous system

Question 28

schwann cells

Answer 28

build myelin sheath in the peripheral nervous system

Question 29

radial glia

Answer 29

guide migration of neurons and axons and dendrites during embroyonic development

Question 30

blood-brain barrier

Answer 30

mechanism that excludesmost chemicals from the vertebrate brain

Question 31

electrical gradient / polarization

Answer 31

difference in electrical charge between the inside (negative) and outside (positive) of the cell

Question 32

resting potential

Answer 32

difference in negative (inside) and positive (outside) voltage in a resting neuron

Question 33

typical electrical levels of a neuron

Answer 33

-70 millivolts (mV)

Question 34

selectively permeable

Answer 34

some chemicals pass through this membrane more freely than others. keeps membrane from depolarize

Question 35

sodium-potassium pump

Answer 35

protein complex, transports 3 sodium ions out of the cell while drawing two potassium ions into it. active transport. requires energy.

Question 36

concentration gradient

Answer 36

difference in distribution of ions across the membrane

Question 37

which ions are outside/ inside the cell?

Answer 37

sodium ions are concentrated outside, potassium is more concentrated inside

Question 38

when membrane is at rest, what drives potassium ions out of the cell? what draws them into the cell?

Answer 38

concentration gradeitn drives potassium out of the cell, electrical gradient drawsthem into the cell. sodium-potassium pump also draws them in

Question 39

action potentials

Answer 39

messages sent by axons

Question 40

hyperpolarization

Answer 40

increased polarization, caused by stimulation by negative charge to an axon membrane

Question 41

depolarize

Answer 41

reduce polarization towards zero

Question 42

threshold of excitation

Answer 42

stimulation beyond this point produces a massive depolarization of the membrane. the membrane opens sodium channels and sodium ions flow into the cell. triggered by any stimulation beyond the threshold, regardless of how far.

Question 43

subthreshold stimulation

Answer 43

small response proportional to amount of current

Question 44

voltage-gated channels

Answer 44

changels with permeability dependant on the voltage difference across the membrane

Question 45

local anesthetics

Answer 45

attach to sodium channels of mjembrane, preventing sodium ions from entering and stopping action potentials. (i.e. novocain stop axons from transmitting pain messages to your brain)

Question 46

all-or-none-law

Answer 46

amplitude and veolicty of an action potential are independent of the stimulus that initiated it, provided that the stimulus reaches the threshold.

Question 47

refractory period

Answer 47

immediatly after action potential in shich a cell resists production of further action potentials

Question 48

absolute refractory period

Answer 48

membrane cannot produce an action potential, regardless of the stimulation

Question 49

relative refractory period

Answer 49

cell requires a stronger than usual stimulus to initiate an action potential.

Question 50

axon hillock

Answer 50

swelling where the axon exits the soma; where action potential begins

Question 51

propagation of the action potential

Answer 51

transmission of action potential down an axon

Question 52

saltatory conduction

Answer 52

the jumping of actio potentials from node to node to propogate the axon potential down the axon

Question 53

local neurons

Answer 53

neurons without an axon which exchange information only with closest neighbors

Question 54

graded potential

Answer 54

a membrane potential that varies in magnitude in proportion to the intensity of the stimulus.