Redo Ch 12

absolute refractory period

Period during an action potential when another action potential cannot be generated because voltage-gated Na+ channels are inactivated.

acetylcholine (ACh)

One of the most common neurotransmitters functioning at neuromuscular junctions and many autonomic synapses.

acetylcholinesterase (AChE)

Enzyme that breaks down acetylcholine within synapses to regulate its effects.

action potential

An all-or-nothing rapid reversal of membrane potential that propagates down the length of an axon.

afferent neuron

Neuron that carries sensory signals toward the CNS.

anterograde transport

Movement of substances from the neuron soma toward the axon terminal using kinesin.

aspartate

Excitatory amino acid neurotransmitter of the spinal cord.

astrocyte

CNS glial cell that supports neurons and helps form the blood-brain barrier.

autonomic nervous system (ANS)

Division of the PNS that automatically controls cardiac muscle smooth muscle and glands.

axon

Single neuron process that carries action potentials away from the cell body.

axon hillock

Region of the neuron cell body where the axon originates and action potentials are initiated.

axon terminal

End of the axon where neurotransmitters are released.

axoplasm

Cytoplasm within the axon.

biogenic amine

Class of neurotransmitters derived from amino acids lacking a carboxyl group.

bipolar neuron

Neuron with one axon and one dendrite.

blood-brain barrier (BBB)

Physiological barrier that restricts movement of substances between blood and CNS.

brain

Organ of the CNS composed of gray and white matter.

calcium (Ca++) pumps

Proteins that remove Ca++ from the cytoplasm into ER or extracellular fluid.

central nervous system (CNS)

Brain and spinal cord.

cerebrospinal fluid (CSF)

Fluid produced in the CNS that cushions and supports the brain and spinal cord.

chemical synapse

Junction where neurotransmitters diffuse across a synaptic cleft.

cholinergic

Neurotransmitter system involving acetylcholine.

continuous conduction

Slow propagation of an action potential along an unmyelinated axon.

converging circuit

Neural circuit where multiple neurons synapse on one neuron.

current

Movement of charged particles.

dendrite

Branchlike extension of a neuron that receives signals.

diverging circuit

Neural circuit where one neuron signals multiple neurons.

dynein

Motor protein responsible for retrograde transport.

efferent neuron

Neuron that carries motor signals away from the CNS.

electrical synapse

Connection where ions pass directly between cells through channels.

enteric nervous system (ENS)

Division of the nervous system controlling the gastrointestinal tract.

enzymatic degradation

Breakdown of neurotransmitters after release into the synaptic cleft.

ependymal cell

CNS glial cell that produces cerebrospinal fluid.

gamma-amino-butyric acid (GABA)

Primary inhibitory neurotransmitter in the brain.

ganglion (ganglia)

Cluster of neuron cell bodies in the PNS.

gated

Property of ion channels that determines how they open.

glial cell (neuroglia)

Support cells that maintain and protect neurons.

glutamate

Primary excitatory neurotransmitter in the brain.

glycine

Primary inhibitory neurotransmitter in the spinal cord.

G-protein coupled receptor (GPCR)

Receptor that activates second messenger systems via G-proteins.

graded potential

Variable local change in membrane potential.

gray matter

Regions containing neuron cell bodies and unmyelinated axons.

Guillain-Barré syndrome

PNS disorder caused by demyelination of neurons.

hyperpolarize

Membrane becomes more negative than resting potential.

inhibitory postsynaptic potential (IPSP)

Hyperpolarizing graded potential reducing likelihood of action potential.

integration

Nervous system function combining and processing information.

ionotropic receptor

Neurotransmitter receptor that acts as a ligand-gated ion channel.

kinesin

Motor protein responsible for anterograde transport.

leakage channel

Always-open ion channel allowing passive ion movement.

ligand-gated channel

Ion channel that opens when a chemical binds.

local potential

Small change in membrane potential near an open channel.

mechanically gated channel

Ion channel that opens in response to physical force.

metabotropic receptor

Receptor that activates intracellular signaling pathways.

motor neuron

Neuron that sends signals to muscles and glands.

multipolar neuron

Neuron with one axon and multiple dendrites.

multiple sclerosis

CNS disease involving progressive demyelination.

muscarinic receptor

Metabotropic acetylcholine receptor.

myelin

Lipid-rich insulating material around axons.

myelination

Process of forming myelin around axons.

myelin sheath

Layers of myelin that increase conduction speed.

nerve

PNS bundle of axons.

nerve fiber

Single axon within a nerve.

neuron

Specialized cell that generates and transmits electrical signals.

neuronal pool

Group of neurons functioning together.

neuropeptide

Neurotransmitter made of short amino acid chains.

neurosoma (soma)

Cell body of a neuron.

neurotransmitter

Chemical messenger released at synapses.

nicotinic receptor

Ionotropic acetylcholine receptor.

Nissl body

Rough ER in neurons.

nodes of Ranvier

Gaps in myelin where action potentials regenerate.

nucleus (nuclei)

Cluster of neuron cell bodies in the CNS.

Ohm's law

Current is proportional to voltage and inversely proportional to resistance.

oligodendrocyte

CNS glial cell that forms myelin.

peripheral nervous system (PNS)

All neural tissue outside CNS.

polarized

Membrane state where inside is negative relative to outside.

postsynaptic neuron

Neuron receiving neurotransmitter signals.

presynaptic neuron

Neuron releasing neurotransmitters.

process

Extension of a neuron cell body.

propagation

Spread of an action potential along an axon.

relative refractory period

Period requiring stronger stimulus for another action potential.

repolarized

Return of membrane potential to resting state.

resistance

Opposition to electrical current flow.

resting membrane potential (RMP)

Baseline electrical charge across neuron membrane.

retrograde transport

Movement from axon terminal back to soma using dynein.

reuptake

Transport of neurotransmitters back into presynaptic neuron.

reverberating circuit

Neural circuit that self-stimulates rhythmic activity.

saltatory conduction

Rapid conduction of action potentials along myelinated axons.

satellite cell

PNS glial cell supporting neuron cell bodies in ganglia.

Schwann cell

PNS glial cell forming myelin around axons.

sensory input (sensation)

Detection of stimuli and conversion to electrical signals.

sensory neuron

Neuron that carries afferent signals toward CNS.

serotonin-specific reuptake inhibitor (SSRI)

Drug that increases serotonin by blocking reuptake.

somatic motor neuron

Neuron controlling voluntary skeletal muscle.

somatic nervous system (SNS)

Division of PNS controlling voluntary movement.

somatosensory neuron

Afferent neuron carrying sensory information from body surface.

spatial summation

Addition of signals from multiple synapses at once.

spinal cord

CNS structure that relays signals and controls reflexes.

stimulus

Any change that produces a response.

subthreshold

Graded potential that does not reach action potential threshold.

summate

To combine graded potentials over time or space.