ch 8 human phys

What are the two main divisions of the nervous system?

CNS: brain and spinal cord. PNS: nerves connecting the body.

What do dendrites do?

Receive incoming signals.

What do axons do?

Carry outgoing information to other cells.

What are glial cells?

Cells that provide chemical and physical support to neurons.

What is the resting membrane potential?

About −70 mV.

What is depolarization?

A positive change in membrane potential; generally excitatory.

What is hyperpolarization?

A negative change in membrane potential; generally inhibitory.

What is a graded potential?

A small, local membrane-potential change proportional to stimulus size.

What happens when membrane potential reaches threshold?

An action potential is triggered.

What is the threshold voltage?

About −55 mV.

Which ion enters during the rising phase of an action potential?

Na⁺ enters through voltage-gated Na⁺ channels.

Which ion leaves during repolarization?

K⁺ leaves through voltage-gated K⁺ channels.

What is the refractory period?

A short period when the neuron cannot be stimulated.

What increases action potential speed?

Larger axon diameter and myelination.

What is saltatory conduction?

Action potentials jump between nodes of Ranvier on myelinated axons.

What is a synapse?

The junction between a neuron and its target cell.

What happens at an electrical synapse?

Electrical signals pass directly through gap junctions.

What happens at a chemical synapse?

Neurotransmitters are released into the extracellular fluid.

What ion triggers neurotransmitter release?

Ca²⁺ entering the axon terminal.

What is the most common excitatory CNS neurotransmitter?

Glutamate.

What is the most common inhibitory CNS neurotransmitter?

GABA.

What are ionotropic receptors?

Receptor-channels causing rapid changes in membrane potential.

What are metabotropic receptors?

G protein-coupled receptors causing slower cellular effects.

What is intensity coding?

Larger inputs produce more action potentials and neurotransmitter release.

What is spatial summation?

Multiple inputs are active at the same time in different locations.

What is temporal summation?

Repeated inputs combine over a short time period.

What is synaptic plasticity?

The ability of synapses to change over time.

What is long-term potentiation (LTP)?

A synapse becomes more powerful through repeated use.

What is long-term depression (LTD)?

A synapse becomes weaker when it is seldom used.

What is the neuromuscular junction (NMJ)?

A large, powerful synapse between a motor neuron and muscle fiber