what i don't know for exam 2

Question 1

describe the general characteristics of nervous tissue

Answer 1

excitable and capable of sending an receiving electrochemical signals that provide the body with information

Question 2

unipolar neurons

Answer 2

sensory neurons, one nerve process extending from the cell body - an axon extends into dendrites

Question 3

bipolar neurons

Answer 3

sensory neurons, two extensions (one axon, one dendrite)

Question 4

multipolar neurons

Answer 4

motor neurons and interneurons, single axon and many dendrites, allows for integration of a great deal of information from other neurons

Question 5

schwann cells

Answer 5

PNS, help form myelin sheath

Question 6

oligodendrocytes

Answer 6

CNS, help form myelin sheath

Question 7

explain the function of structural multipolar neurons within a circuit

Answer 7

often interneurons sending signals from afferent to efferent neurons or motor neurons

Question 8

explain the function of structural pseudounipolar neurons within a circuit

Answer 8

typically sensory or afferent neurons

Question 9

dorsal horn

Answer 9

crescent shaped projection of gray matter within the spinal cord where sensory neurons enter the spinal cord

Question 10

ventral horn

Answer 10

somatic motor neurons whose axons exit the cord via ventral roots

Question 11

current

Answer 11

the flow of charged particles from one point to another, requires an electrical potential (potential)

Question 12

potential

Answer 12

a difference in electrical charge between the inside and outside of the cell membrane

Question 13

electrochemical gradient

Answer 13

determines which way ions flow, composed of the chemical gradient and electrical gradient

Question 14

how is the chemical gradient established

Answer 14

constantly working Na+/K+ protein pumps

Question 15

how is the electrical gradient formed

Answer 15

the active transport of ions across the cell membrane

Question 16

the three main cellular events or characteristics that contribute to the resting membrane potential

Answer 16

1. membrane is more permeable to potassium ions than sodium ions, ION PERMEABILITY
2. Na+/K+ pump removes more positive charges from the ICF, PUMP FUNCTION
3. large anions (-) stuck in the cell, ANIONS CREATE AN ELECTRICAL GRADIENT (UNEVEN DISTRIBUTION OF CHARGE)

Question 17

concentration gradients of sodium and why

Answer 17

lower inside the cell, due to the action of a membrane active transport system which pumps sodium out of the cell and potassium in

Question 18

concentration gradients of chloride

Answer 18

lower inside the cell

Question 19

concentration gradients of potassium

Answer 19

greater inside the cell, due to the action of a membrane active transport system which pumps sodium out of the cell and potassium in

Question 20

explain the importance of the resting membrane potential in relation to communication in the nervous system

Answer 20

neurons can be equally inhibited or excited by a graded potential - one stimulus can cause the same reaction in multiple neurons

Question 21

how do ligand (chemically) gated ion channels open and what neurons are they in

Answer 21

open when a specific molecule binds to the channel protein, in interneurons and efferent neurons

Question 22

mechanically gated ion channel

Answer 22

open when a physical force changes the shape of the channel protein, afferent neurons

Question 23

when do voltage gated ion channels open

Answer 23

when the membrane potential (voltage) changes

Question 24

depolarization - what gates open and why?

Answer 24

becoming more positive, gated channels open, Na+ ions diffuse into the cell, membrane potentials become more positive as positively charged Na+ ions enter the cell

Question 25

hyperpolarization

Answer 25

becoming more negative, gated channels open, Cl- ions enter the cell or K+ ions diffuse out of the cell, membrane potential becomes more negative

Question 26

Na+ and K+ voltage-gated channels at RMP (-70mV)

Answer 26

Na+ and K+ channels (in axons) are closed

Question 27

Na+ and K+ voltage-gated channels at threshold (-55mV) and what happens to the membrane

Answer 27

Na+ channels open in axon - sodium diffuses in membrane depolarizes (more positive)

K+ channels are still closed

Question 28

Na+ and K+ voltage-gated channels at peak depolarization (+30 mV)

Answer 28

K+ channels open - cell begins to repolarize (becomes more negative) as potassium diffuses out of the cell

Na+ channels close

Question 29

steps of an action potential

Answer 29

1. RESTING POTENTIAL - RMP (-70mV), pumps remain active
2. DEPOLARIZING STIMULUS - a few Na+ channels open and Na+ ions (positve) enter the cell and depolarizes the membrane and brings it closer to threshold
3. POTENTIAL REACHES THRESHOLD (-55mV) - excitation causes the potential at the axon hillock to become more positive, when potential passes threshold neuron starts an action potential
4. MEMBRANE POTENTIAL REACHES PEAK DEPOLARIZATION (+30mV) - Na+ channels close, K+ channels open - cell begins to repolarize (becomes more negative)
5. POTASSIUM CHANNELS STAY OPEN LONGER - more K+ leaves the cell than Na+ enters resulting in hyperpolarization (below RMP), K+ channels then close and Na+/K+ pumps bring the membrane back to the original state

Question 30

refractory period

Answer 30

time when a region of a neuron cannot fire another action potential

Question 31

absolute refractory period

Answer 31

an occurrence after a neuron has fired an impulse where the neuron cannot fire another pulse for a short time directly after, due to the nervous systems inability to work at an even faster rate

Question 32

relative refractory period

Answer 32

the time during which a stronger than normal stimulus is needed in order to elicit an action potential

Question 33

describe how myelination affects the conduction of a neuron

Answer 33

allows for very fast propagation of signal, allows ions to diffuse further because they cannot be transported to the extracellular fluid by pumps

Question 34

propagation

Answer 34

transmission of motion, light, sound, etc in a particular direction or through a medium

Question 35

saltatory conduction

Answer 35

the propagation of action potentials along myelinated axons from one node of Ranvier to the next node

this increases the conduction velocity of action potentials