Campbell Biology Chapter 48

Neurons

Nerve cells that transfer information within the body

Electrical signals (long distance) and chemical signals (short distance)

two types of signals that neurons use to communicate

Ganglia

Simple clusters of neurons that process information

Brain

A more complex organization of neurons

Cell body

The part of the neuron where most organelles are located

Dendrites

highly branched extensions that receive signals from other nuerons

Axon

an extension of a neuron that transmits signals to other cells

Axon hillock

the cone shaped base of an axon

Neurotransmitters

Chemical messengers that pass information across the synapse

Synapse

a junction between an axon and another cell

Neuron structure

dendrite, nucleus, cell body, axon, synapse

Presynaptic cell

neuron

Postsynaptic cell

a neuron, muscle, or gland cell

Glia/Glial cells

Nourishment cells of neurons

Three stages of information processing in nervous systems

sensory input, integration, and motor output

Sensory neurons

Location where information is transmitted from sensors that detect external stimuli and internal conditions.

Interneurons

Cells where sensory information sent to the brain is integrated

Motor neurons

Transports motor outputs through the brain and trigger muscle or gland activity

Central nervous system

Location where tengration takes place; includes brain and a nerve cord

Peripheral nervous system

Carries information into and out of the CNS

Nerves

Neurons of the PNS bundled together

Membrane potential

A difference in electrical charge across the plasma membrane of a cell

Resting potential

The membrane potential of a neuron not sending signals

Concentration levels of a mammalian neuron

K+ highest inside the cell, Na+ highest outside the cell

Sodium-potassium pumps

use the energy of ATP to maintain K+ and Na+ gradients across the plasma membrane

Ion channels

opening in the plasma membrane that converts chemical potential to electrical potential

equilibrium potential

membrane voltage for a particular ion at equilibrium and can be calculated using the Nernst equation

Resting neuron

currents of K+ and Na+ are the same and opposite, the resting potential across the membrane remains steady

Gated ion channels

Channels inside neurons that open and close in response to stimuli

Gated K+ channels open

K+ diffuses out, making the inside of the cell more negative

Hyperpolarization

an increase in magnitude of membrane potential

Depolarization

a reduction in the magnitude of the membrane potential

Graded potentials

changes in polarization where the magnitude of the change varies with the strength of the stimulus

Action potential

A massive change in membrane voltage cause by depolarization

Voltage gated

Ion channels opening or closing when the membrane potential passes a certain level

Refractory period

period after an action potential where a second action potential cannot be initiated

Nodes of Ranvier

gaps in the myelin sheath where voltage-gated Na+ channels are found

Saltatory conduction

Process where action potentials in myelinated axons jump between the nodes of Ranvier

Gap junctions

Location where the electrical current flows from one neuron to another

Chemical neurotransmitter

In a chemical synapse, a transmitter that carries information between neurons

Ligand gated ion channels

For direct synaptic transmission; involves binding of neurotransmitters. located in the postsynaptic cell.

Postsynaptic potential

Happens when a neurotransmitter binding causes ion channels to open

Excitatory postsynaptic potentials

depolarizations that bring the membrane potential toward threshold

Inhibitory postsynaptic potentials

hyperpolarizations that move the membrane potential farther from threshold

Temporal summation

Occurs when two EPSP's are produced in rapid succession

Spatial summation

EPSPs produced nearly simultaneously by different synapses on the same postsynaptic neuron add together

Acetylcholine

a common neurotransmitter in vertebrates and invertebrates involved in muscle stimulation, memory formation, and learning.

Ligand gated and metabotropic

two major classes of acetylcholine receptor

Amino acids, biogenic amines, neuropeptides, and gases

Remainder of neurotransmitters

Major neurotransmitters

Acetlycholine, GABA, Dopamine, Nitric oxide