c2.2 neural signalling

nervous system

consists of millions of neurons which carry rapid electrical impulses around the body

motor neuron

neurons that carry outgoing information from the brain and spinal cord to the muscles and glands

sensory neuron

neurons that carry incoming information from the sensory receptors to the brain and spinal cord

dendrite

Branchlike parts of a neuron that are specialized to receive information.

cell body

Largest part of a typical neuron; contains the nucleus and much of the cytoplasm

axon

the neuron extension that passes messages through its branches to other neurons or to muscles or glands

nodes of Ranvier

Gaps in the myelin sheath to which voltage-gated sodium channels are confined.

Schwann cell

forms insulating myelin sheaths around the axons of neurons (in the peripheral nervous system).

myelin sheath

fatty layer that covers the axon of some neurons and helps speed up neural impulses

saltatory conduction

the jumping of action potentials from node to node

nerve impulse

the message carried by a neuron (via a change in electrical potential)

-70 mV

resting membrane potential of a neuron

active transport

transport that uses ATP energy to pump particles against their concentration gradient

passive transport

the movement of substances across a cell membrane without the use of energy by the cell

sodium-potassium pump

a carrier protein that uses ATP to actively transport sodium ions out of a cell and potassium ions into the cell

phosphorylation

the addition of a phosphate group to a molecule (providing energy for cellular processes)

ion location at resting potential

More Na+ outside and more K+ inside

depolarization

The process during the action potential when sodium is rushing into the cell causing the interior to become more positive.

repolarization

The process during the action potential where potassium ions diffuse out of the neuron.

leak channels

channels that are always open and allow ions to move along their gradient (passive transport). At resting potential, there are more K+ leak channels open than Na+ leak channels.

local currents

diffusion of ions in a neuron

result of myelination

prevents ions from entering or leaving the neuron along the myelinated segments = faster conduction of action potential

presynaptic neuron

conducts impulses toward the synapse

postsynapatic neuron

has receptors and receives neurotransmitters from the presynaptic neuron

neurotransmitters

chemical messengers that cross the synaptic gaps between neurons

synapse

the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron

acetylcholine

an example of a neurotransmitter