Unit 1 Nerve Cells and Impulses

Question 1

What is the absolute refinery period?

Answer 1

a time when the membrane is unable to produce an action potential because sodium channels are closed. It is the first phase of the refractory period.

Question 2

Define action potential

Answer 2

all-or-none message sent by an axon.

Question 3

all-or-non law

Answer 3

principle that the amplitude and velocity of an action potential are independent of the stimulus that initiated it

Question 4

concentration gradient

Answer 4

difference in distribution of ions across the neuron’s membrane. it is one of the forces that acts on the sodium and potassium ions

Question 5

depolarize/depolarization

Answer 5

to reduce polarization toward zero across a membrane. Happens right before action potential peal when NA+ channels open, and rushes into the neuron.

Question 6

Electrical Gradient

Answer 6

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

Question 7

Graded potential and when does it happen

Answer 7

a membrane potential that varies in magnitude in proportion to the intensity of the stimulus (happens when a local neuron receives information from other neurons)

Question 8

Hyperpolarization and when does it happen in the actional potential process

Answer 8

increased polarization (increasing neg charge inside neuron) final stage of action potential due to potassium leaving

Question 9

local anesthetic

Answer 9

drugs, such as Novocain, that attaches to the sodium channels of the membrane, stopping action potentials

Question 10

Local Neurons

Answer 10

Neurons without an axon, and neurons that don’t follow the all-or-none law

Question 11

Myelin

Answer 11

an insulating material composed of fats and proteins

Question 12

myelinated axons

Answer 12

axons covered with myelin sheaths

Question 13

polarization

Answer 13

difference in electrical charges between the inside and outside of the cell

Question 14

propagation of the action potential

Answer 14

transmission of an action potential down an axon

Question 15

Refractory period

Answer 15

time when the cell resists the production of further action potentials, results of sodium gates shutting at peak of action potential

prevents continuous action potentials

Question 16

relative refractory period

Answer 16

2nd part of refractory period/time after absolute refractory period that requires a stronger stimulus to initiate an action potential due to potassium (K+) flowing out at a higher rate

Question 17

resting potential

Answer 17

condition of a neuron’s membrane when it has not been stimulated or inhibited

Question 18

saltatory condition

Answer 18

the jumping of action potentials from node to node

Question 19

selective permeability

Answer 19

ability of some chemicals to pass more freely than others through a membrane

Question 20

sodium-potassium pump

Answer 20

Protein complex that actively transports sodium ions out of the cell while drawing in two potassium ions,

Question 21

threshold

Answer 21

minimum amount of membrane depolarization necessary to trigger an action potential

Question 22

voltage gated channels

Answer 22

membrane channel whose permeability to sodium (or some other ion) depends on the voltage difference across the membrane

Question 23

active transport

Answer 23

a protein mediated process that expends energy to pump chemicals (i.e. glucose, amino acids, vitamins, iron) from the blood into the brain

Question 24

afferent axon

Answer 24

a type of axon that brings information INTO the structure (**remember/HINT ** = admit)

Question 25

astrocytes

Answer 25

star shaped glia that wrap around synapes of functionally related axons, pass chemicals back and forth beween neurons, and blood among neighbouring neurons

Question 26

axon

Answer 26

thin fiber of constant diameter that conveys impulse toward other neurons, an organ, or muscle

Question 27

neurons

Answer 27

receive information and transmit it to other cells

Question 28

glia

Answer 28

serve many functions, such as supporting neurons, regulation, recovery, homeostasis, and myelin production

Question 29

membrane

Answer 29

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

Question 30

nucleus

Answer 30

structure that contains the chromosomes

Question 31

mitochondrion

Answer 31

the structure that performs metabolic activities, providing the energy that the cell uses for all activities

Question 32

ribosomes

Answer 32

sites within a cell that synthesize new protein molecules

Question 33

endoplasmic reticulum

Answer 33

a net work of thin tubes that transport newly synthesized proteins to other locations

Question 34

soma (cell body)

Answer 34

structure containing the nucleus, ribosomes, and mitochondria

Question 35

dendrites

Answer 35

branching fibers that get narrower near their ends, surface is lined with specialized synaptic receptors

Question 36

dendritic spines

Answer 36

short outgrowths that increase the surface area available for synapses

Question 37

blood brain barrier

Answer 37

mechanisms that excludes most chemicals form the vertebrate brain (brains immune defense)

Question 38

efferent axons

Answer 38

carries info AWAY from a structure (exit)

Question 39

synaptic receptors

Answer 39

where dendrite receives info from other neurons

Question 40

presynaptic terminal

Answer 40

end of each axon branch, where axon releases chemicals that cross through the junction between that neuron and another cell

Question 41

nodes of Ranvier

Answer 41

interruptions in the myelin sheath that are essential for transmission of electrical impulses

Question 42

intrinsic neuron/ interneuron

Answer 42

neuron whose axons and dendrites are all confined within a given structure

Question 43

types of glia

Answer 43

astrocytes, microglia, oligodendrocytes, Schwann Cells, Radial glia

Question 44

glucose

Answer 44

a simple sugar, vertebrate neurons require it

Question 45

tripartite synapes

Answer 45

a hypothesis that states the tip of an axon releases chemicals that cause the neighbouring astrocyte to release chemicals of its own, modifying message to next neuron

Question 46

microglia

Answer 46

act as the part of the immune system, removing viruses and fungi from the brain

Question 47

Oligodendrocytes:

Answer 47

are in the brain + spinal cord, build myelin sheaths that surround and insulate necessary for proper functioning, produce myelin sheaths that insulate certain vertebrate axons in the central nervous system

Question 48

Schwann Cells

Answer 48

in periphery of the body, build myelin sheaths that surround and insulate necessary for proper functioning

Question 49

Radial Glia

Answer 49

guide the migration of neurons and their axons and dendrites during embryonic development, most differentiate into neurons

Question 50

why do vertebrate neurons depend on glucose

Answer 50

b/c its the only nutrient that crosses blood brain barrier (BBB) in large quantities

Question 51

Why do we need the BBB

Answer 51

Immune system fights viruses by killing infected cells (suited for replaceable cells like skin & blood) Brain cannot easily replace neurons, therefor has a barrier to block harmful invaders

Question 52

What substances freely cross the BBB and by what mechanism

Answer 52

small uncharged molecules (oxygen, CO2) and fat soluble molecules (i.e. vitamins A & D, psychiatric drugs, illegal drugs) active transport

Question 53

thiamine

Answer 53

vit B1 that helps body convert food into energy, required to process glucose (prevalent in chronic alcoholism)

Question 54

what are the forces involves with the maintenance f the action potential

Answer 54

electrochemical gradient (NA+ more concentrated outside, K+ more concentrated outside making neuron more neg charged at rest attracting positive NA+ inside cell) Selective Permeability of Membrane (prevents depolarization) Sodium-Potassium Pump ( NA+ out and K+ in, helps restore and maintain resting membrane potential) Voltage Gated Ion Channels (depolarization, repolarization, and hyperpolarization)

Question 55

describe the function of an action potential

Answer 55

to enable neural communications, allows neurons to send signals to other neurons, muscles, glands, playing a crucial role in sensory perception, movement, and cognition

Question 56

What is the molecular basis of the action potential (stages)

Answer 56

Resting potential (inside neg charge, NA+ mostly inside, K+ mostly out) depolarization (NA+ channels open, NA+ rushes inside making cell more positive) action potential peak (Neuron becomes highly positive, NA+ channels close) repolarization (K+ channels open, K+ leaves the cell, restoring neg charge) hyperpolarization (too much K+ leaves, making neuron extra neg) recovery/resting potential (sodium potassium pump restores balance by pushing NA+ out, and K+ in)

Question 57

why does saltatory conduction preserve energy

Answer 57

Because depolarization (Letting K+ in) only happens at nodes

Question 58

Describe the propagation of the action potential

Answer 58

AP moves along axon as a wave due to sequential opening of ion channels AP begins at first Node of Ranvier After AP, NA+ enter axon and diffuse, pushing a chain of positive charge along the axon to the next node, where they regenerate a new AP

Question 59

what moves sodium (NA+) into the cell when the membrane is at rest

Answer 59

the concentration gradient and the electrical gradient

Question 60

what mechanisms moves K+ in and out when membrane is at rest

Answer 60

concentration gradient: moves K+ OUT (bc potassium is more concentrated on the inside than outside) electrical gradient: moves K+ INTO (because they are positively charged, and inside is neg charged)