Chapter 34 Flashcards
what type of cell is a neuron?
excitable
excitable cell
cell membrane can generate and conduct signals called impulses or action potentials
action potential
state of reversed polarity
neuron
nerve cell, specially adapted to generate electric signals
synapse
cell-to-cell contact point that is specialised for signal transmission from one cell to another
presynaptic cell
how the cell arrives at the synapse
postsynaptic cell
how the cell leaves from the synapse
what are the anatomical regions of most neurons?
dendrites, cell body, axon, presynaptic axon terminals
dendrites
principle sites where incoming signals arrive from other cells
cell body
contains nucleus and other organelles, has to combine and integrate incoming signals
axon
anatomically specialised for long-distance signal conduction
presynaptic axon terminal
where the axon ends and branches, makes synaptic contact with other cells
nerves
bundles of neurons
tract
bundle of axons in the brain or spinal cord
glial cells
not excitable and do not conduct action potentials, but are still important in the nervous system
oligodendrocytes
glial cells that wrap around axons in the brain and spinal cord
Schwann cells
glial cells outside the brain and spinal cord
myelin
lipid-rich electrically non-conductive sheath
white matter
part of the nervous system that consists of myelinated axons
current
flow of electric charges from place to place
voltage
electric potential difference, exists if positive charges are concentrated in one place and negative charges are concentrated in a different place
bulk solutions
solutions that are not immediately in contact with a membrane
membrane potential
voltage that exists across a membrane, has a charge difference from one side to the other
resting potential
membrane potential in a neuron that is not carrying a signal, typically between -60 and -70 mV
why can charge differences exist across a neuron cell membrane?
because ions cannot pass through the membrane lipid bilayer
sodium-potassium pump
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
equilibrium potential
when there is no further net movement of K+ in a resting neuron
electrochemical equilibrium
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
Nernst equation
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
voltage gated channels
open or close in response to local changes in the membrane potential
stretch gated channels
open or close in response to stretch or tension applied to the cell membrane
ligand gated channels
have binding sites where they bind noncovalently with specific chemical compounds that control them
depolarisation
occurs whenever the charge on the inside of a neuron cell membrane becomes less negative
hyperpolarisation
occurs whenever the charge on the inside of a neuron cell membrane becomes more negative
grade
charges where any value of the potential is possible
action potential
large, brief, localised charge in the membrane potential such that the polarity reverses
nodes of Ranvier
uncovered spaces in between the axons
chemical synapses
signals pass from cell to cell by means of molecules released by the presynaptic cell
neurotransmitter
compound released by the cell when an action potential arrives
electrical synapse
signal transmission is all electrical, no neurotransmitter is involved
neuromuscular junction
synapse between a motor neuron and a skeletal muscle cell
what are the three major chemical categories of neurotransmitters?
amino acids, biogenic amines, peptides
ionotrophic receptors
ligand gated ion channels in the vertebrate neuromuscular junction
metabotropic receptors
commonly G protein-linked receptors
excitatory synapses
synapses that depolarise the postsynaptic membrane
excitatory postsynaptic potentials
graded membrane depolarisations produced by excitatory synapses
inhibitory synapses
shift the membrane potential away from the threshold and thus lower the likelihood of action potential production
inhibitory postsynaptic potentials
graded membrane hyperpolarisations produced by inhibitory synapses
synaptic plasticity
synapses in the nervous system can undergo long-term changes in their functional properties and even physical shape
centralisation
evolutionary trend towards clustering neurons together
cephalisation
major integrating areas became concentrated toward the head
central nervous system
contains relatively large structures that are composed of integrating neurons and glial cells
brain
largest part of CNS, contains the greatest number of neurons
effectors
cells or tissues that perform actions and carry o ut orders
peripheral nervous system
consists of neurons and parts of neurons that are located outside the CNS
what are the main functions of neurons in the CNS
bring sensory information to the CNS and carry orders from CNS to muscle cells or other effectors
interneurons
neurons confined to the CNS, information storage functions
sensory neurons
carry signals to the CNS from sensory cells or organs
efferent neurons
convey signals from the CNS to muscles or other effectors
motor neurons
efferent neurons that carry signals to skeletal muscles
autonomic nervous system
controls effectors other than the skeletal muscles
enteric division
division of the ANS composed of nerve cells internal to the gut wall
ganglion
discrete, anatomically clustered set of neuron cell bodies in the PNS
spinal reflexes
neuron-mediated responses that do not involve participation of the brain
medulla oblongata
all information travelling between the brain and spinal cord must pass through here
cerebral hemispheres
play major roles in sensory perception, learning, memory, and conscious behaviour
location specificity
various specific regions are specialised to carry out specific sensory and motor functions
