Neuronal Excitation

What is a synapse

Communication point between a neuron and another cell

What is a neuromuscular junction

Synapse between a motor neuron and muscle fiber

What is synaptic transmission

Communication of information across a synapse

What is a presynaptic neuron

Neuron that sends the communication signal

What is a postsynaptic neuron

Neuron that receives the communication signal

What is an action potential

Electrical signal that travels along an axon

What is a neurotransmitter

Chemical messenger released by a neuron

What type of neurotransmitter is glutamate

Excitatory neurotransmitter

What type of neurotransmitter is GABA

Inhibitory neurotransmitter

What type of neurotransmitter is acetylcholine

Excitatory neurotransmitter

What type of neurotransmitter is norepinephrine

Excitatory neurotransmitter

What are the main parts of a neuron

Dendrites, cell body, nucleus, axon, and axon terminal

What do dendrites do

Receive incoming neuronal information

What does the axon do

Carries action potentials away from the cell body

What does the axon terminal do

Releases neurotransmitters to the next cell

What is the charge inside a resting neuron

Negative relative to the outside of the neuron

What does polarized mean

Different electrical charges exist across the cell membrane

What is depolarization

Inside of the neuron becomes more positive

What causes depolarization in the postsynaptic neuron

Binding of an excitatory neurotransmitter

What does excitation make more likely

Generation of an action potential

What is hyperpolarization

Inside of the neuron becomes more negative

What causes hyperpolarization

Binding of an inhibitory neurotransmitter

What does inhibition make less likely

Generation of an action potential

What is the axon hillock

Region where an action potential can be triggered

What is summation

Adding together excitatory and inhibitory neuronal inputs

Where do neuronal inputs summate

Across the neuronal cell body

What is threshold

Voltage level needed to trigger an action potential

What happens when threshold is exceeded

The neuron generates an action potential

Where are many voltage-gated channels located

At the axon hillock

What are voltage-gated channels

Ion channels opened by changes in membrane voltage

What is repolarization

Membrane returns toward its resting electrical state

Why does repolarization occur

Prepares the neuron for another action potential

What does myelin do to conduction speed

Increases action potential conduction speed

What else does myelin do

Helps protect the neuronal axon

What is saltatory conduction

Faster action potential conduction along a myelinated axon

What happens when an action potential reaches the axon terminal

The neuron releases neurotransmitters

What do released neurotransmitters act on

Receptors on the postsynaptic cell

What happens at the neuromuscular junction

Neurotransmitters act on muscle fibers causing contraction

What must happen for an action potential to occur

Summed neuronal inputs must exceed threshold

What determines a neuron's effect on the next cell

The type of neurotransmitter released

What direction do afferent signals travel

Toward the central nervous system

What type of information is afferent

Sensory information traveling toward the CNS

What neuron orders carry sensory information

1st, 2nd, and 3rd order neurons

What do Group I fibers detect

Proprioceptive sensory information

What are Group I fibers associated with

Proprioceptors for proprioception

What is the myelination of Group I fibers

Group I fibers are myelinated

What size are Group I fibers

Largest diameter afferent fibers

How fast are Group I fibers

Fastest conducting afferent fibers

What do Group II fibers detect

Light touch and vibration

What are Group II fibers associated with

Mechanoreceptors for mechanical sensation

What is the myelination of Group II fibers

Group II fibers are myelinated

How do Group II fibers compare with Group I

Slightly smaller and slower than Group I

What do A-delta fibers detect

Sharp pain and cold temperature

What receptors are associated with A-delta fibers

Nociceptors and cold thermoreceptors

What is the myelination of A-delta fibers

A-delta fibers are myelinated

What size are A-delta fibers

Small diameter afferent fibers

How fast are A-delta fibers

Slower conducting afferent fibers

What do C fibers detect

Dull pain and warm temperature

What receptors are associated with C fibers

Nociceptors and warm thermoreceptors

What is the myelination of C fibers

C fibers are unmyelinated

What size are C fibers

Smallest diameter afferent fibers

How fast are C fibers

Slowest conducting afferent fibers

What is proprioception

Sense of body position and movement

What is a proprioceptor

Sensory receptor that detects proprioception

What is a mechanoreceptor

Sensory receptor that detects mechanical stimuli

What is a nociceptor

Sensory receptor that detects painful stimuli

What is a thermoreceptor

Sensory receptor that detects temperature

What direction do efferent signals travel

Away from the central nervous system

What type of information is efferent

Motor information traveling from the CNS

What motor neurons are part of motor pathways

Upper and lower motor neurons

What is a lower motor neuron

Motor neuron carrying signals toward muscle

What type of motor neuron innervates skeletal muscle

Alpha motor neuron

What are gamma motor neurons associated with

Motor control related to reflexes

What is a motor unit

One alpha motor neuron and its innervated muscle fibers

What size neuron innervates a small motor unit

Small alpha motor neuron with small axon

How many muscle fibers are in small motor units

Relatively few muscle fibers

What size muscle fibers are in small motor units

Small diameter muscle fibers

How much force do small motor units produce

Relatively small amounts of force

How do small motor units respond to fatigue

They are relatively fatigue resistant

When are small motor units recruited voluntarily

First during voluntary contractions

What size neuron innervates a large motor unit

Large alpha motor neuron with large axon

How many muscle fibers are in large motor units

Relatively many muscle fibers

What size muscle fibers are in large motor units

Large diameter muscle fibers

How much force do large motor units produce

Relatively large amounts of force

How do large motor units respond to fatigue

They fatigue relatively quickly

When are large motor units recruited voluntarily

Last during voluntary contractions

What is voluntary motor unit recruitment order

Small motor units first then large motor units

What motor units are important for posture

Small fatigue-resistant motor units

How can voluntary force increase

Increase firing rate or recruit additional motor units

What is extracellular stimulation

External electrical stimulation of nerve fibers

What are examples of extracellular stimulation

TENS and NMES electrical stimulation

Which nerve fibers activate first externally

Large nerve fibers activate first

How does external recruitment compare with voluntary recruitment

External stimulation recruits fibers in reverse order