Chapter 34

Question 1

what type of cell is a neuron?

Answer 1

excitable

Question 2

excitable cell

Answer 2

cell membrane can generate and conduct signals called impulses or action potentials

Question 3

action potential

Answer 3

state of reversed polarity

Question 4

neuron

Answer 4

nerve cell, specially adapted to generate electric signals

Question 5

synapse

Answer 5

cell-to-cell contact point that is specialised for signal transmission from one cell to another

Question 6

presynaptic cell

Answer 6

how the cell arrives at the synapse

Question 7

postsynaptic cell

Answer 7

how the cell leaves from the synapse

Question 8

what are the anatomical regions of most neurons?

Answer 8

dendrites, cell body, axon, presynaptic axon terminals

Question 9

dendrites

Answer 9

principle sites where incoming signals arrive from other cells

Question 10

cell body

Answer 10

contains nucleus and other organelles, has to combine and integrate incoming signals

Question 11

axon

Answer 11

anatomically specialised for long-distance signal conduction

Question 12

presynaptic axon terminal

Answer 12

where the axon ends and branches, makes synaptic contact with other cells

Question 13

nerves

Answer 13

bundles of neurons

Question 14

tract

Answer 14

bundle of axons in the brain or spinal cord

Question 15

glial cells

Answer 15

not excitable and do not conduct action potentials, but are still important in the nervous system

Question 16

oligodendrocytes

Answer 16

glial cells that wrap around axons in the brain and spinal cord

Question 17

Schwann cells

Answer 17

glial cells outside the brain and spinal cord

Question 18

myelin

Answer 18

lipid-rich electrically non-conductive sheath

Question 19

white matter

Answer 19

part of the nervous system that consists of myelinated axons

Question 20

current

Answer 20

flow of electric charges from place to place

Question 21

voltage

Answer 21

electric potential difference, exists if positive charges are concentrated in one place and negative charges are concentrated in a different place

Question 22

bulk solutions

Answer 22

solutions that are not immediately in contact with a membrane

Question 23

membrane potential

Answer 23

voltage that exists across a membrane, has a charge difference from one side to the other

Question 24

resting potential

Answer 24

membrane potential in a neuron that is not carrying a signal, typically between -60 and -70 mV

Question 25

why can charge differences exist across a neuron cell membrane?

Answer 25

because ions cannot pass through the membrane lipid bilayer

Question 26

sodium-potassium pump

Answer 26

actively transports ions by using one ATP to expel 3 Na+ ions from inside the neuron and to pump two K+ ions into the neuron from the outside

Question 27

equilibrium potential

Answer 27

when there is no further net movement of K+ in a resting neuron

Question 28

electrochemical equilibrium

Answer 28

a state in which the electrical effect causes diffusion in one direction and the concentration effect causes diffusion of equal magnitude in the opposite direction

Question 29

Nernst equation

Answer 29

``` potential difference at electrochemical equilibrium = 2.3*(RT/zF)*log([ion outside]/[ion inside]) z = number of charges per ion T = absolute temperature R = universal gas constant F = Faraday constant ```

Question 30

voltage gated channels

Answer 30

open or close in response to local changes in the membrane potential

Question 31

stretch gated channels

Answer 31

open or close in response to stretch or tension applied to the cell membrane

Question 32

ligand gated channels

Answer 32

have binding sites where they bind noncovalently with specific chemical compounds that control them

Question 33

depolarisation

Answer 33

occurs whenever the charge on the inside of a neuron cell membrane becomes less negative

Question 34

hyperpolarisation

Answer 34

occurs whenever the charge on the inside of a neuron cell membrane becomes more negative

Question 35

grade

Answer 35

charges where any value of the potential is possible

Question 36

action potential

Answer 36

large, brief, localised charge in the membrane potential such that the polarity reverses

Question 37

nodes of Ranvier

Answer 37

uncovered spaces in between the axons

Question 38

chemical synapses

Answer 38

signals pass from cell to cell by means of molecules released by the presynaptic cell

Question 39

neurotransmitter

Answer 39

compound released by the cell when an action potential arrives

Question 40

electrical synapse

Answer 40

signal transmission is all electrical, no neurotransmitter is involved

Question 41

neuromuscular junction

Answer 41

synapse between a motor neuron and a skeletal muscle cell

Question 42

what are the three major chemical categories of neurotransmitters?

Answer 42

amino acids, biogenic amines, peptides

Question 43

ionotrophic receptors

Answer 43

ligand gated ion channels in the vertebrate neuromuscular junction

Question 44

metabotropic receptors

Answer 44

commonly G protein-linked receptors

Question 45

excitatory synapses

Answer 45

synapses that depolarise the postsynaptic membrane

Question 46

excitatory postsynaptic potentials

Answer 46

graded membrane depolarisations produced by excitatory synapses

Question 47

inhibitory synapses

Answer 47

shift the membrane potential away from the threshold and thus lower the likelihood of action potential production

Question 48

inhibitory postsynaptic potentials

Answer 48

graded membrane hyperpolarisations produced by inhibitory synapses

Question 49

synaptic plasticity

Answer 49

synapses in the nervous system can undergo long-term changes in their functional properties and even physical shape

Question 50

centralisation

Answer 50

evolutionary trend towards clustering neurons together

Question 51

cephalisation

Answer 51

major integrating areas became concentrated toward the head

Question 52

central nervous system

Answer 52

contains relatively large structures that are composed of integrating neurons and glial cells

Question 53

brain

Answer 53

largest part of CNS, contains the greatest number of neurons

Question 54

effectors

Answer 54

cells or tissues that perform actions and carry o ut orders

Question 55

peripheral nervous system

Answer 55

consists of neurons and parts of neurons that are located outside the CNS

Question 56

what are the main functions of neurons in the CNS

Answer 56

bring sensory information to the CNS and carry orders from CNS to muscle cells or other effectors

Question 57

interneurons

Answer 57

neurons confined to the CNS, information storage functions

Question 58

sensory neurons

Answer 58

carry signals to the CNS from sensory cells or organs

Question 59

efferent neurons

Answer 59

convey signals from the CNS to muscles or other effectors

Question 60

motor neurons

Answer 60

efferent neurons that carry signals to skeletal muscles

Question 61

autonomic nervous system

Answer 61

controls effectors other than the skeletal muscles

Question 62

enteric division

Answer 62

division of the ANS composed of nerve cells internal to the gut wall

Question 63

ganglion

Answer 63

discrete, anatomically clustered set of neuron cell bodies in the PNS

Question 64

spinal reflexes

Answer 64

neuron-mediated responses that do not involve participation of the brain

Question 65

medulla oblongata

Answer 65

all information travelling between the brain and spinal cord must pass through here

Question 66

cerebral hemispheres

Answer 66

play major roles in sensory perception, learning, memory, and conscious behaviour

Question 67

location specificity

Answer 67

various specific regions are specialised to carry out specific sensory and motor functions