Reflexes and Reaction Times - Bio 162

Cell body (soma)

The large part of the neuron containing the nucleus and organelles

Dendrites

Short projections continuous with the soma and function to receive information

Axon

The single long projection responsible for transmitting information to the cell body to the next cell

Axon hillock

The portion of the axon connecting the cell body (often swollen) - the cite of action potential generation

Axon terminal

The end of an axon that is branched, responsible for converting electrical impulses into a chemical signal and passes information to the next cell in line

Synapse

A junction between two nerve cells

Pre-synaptic neuron

The neuron sending the signal

Post-synaptic neuron

The neuron receiving the signal

Action potential

An electrical impulse that travels down the axon of a neuron

Neurotransmitter

A chemical that is used to communicate between neurons

Local potential

Triggered when a neurotransmitter is bound to protein in the post-synaptic cell membrane

Excitatory

Can cause the neuron to initiate an action potential in its axon

Inhibitory

Can cause the neuron to be less likely to initiate an action potential

Afferent neurons

Sensory, convey impulses towards the CNS from receptors throughout the body

Efferent neurons

Motor, convey impulses away from the CNS to a target - can be muscle or gland

Interneurons

Found within the CNS, connect afferent and efferent neurons and integrate sensory input and motor output

Reflex

A very fast, involuntary response to a stimulus

Latency

Refers to the amount of time that passes between the initial stimulus and the response

Muscle stretch reflex

Follows the five steps of a typical reflex arc and is triggered when a muscle is rapidly stretched

Muscle spindles

Muscle fibers with sensory neuron axon terminals wrapped around them

White matter

Contains axons of neurons that are wrapped in an insulating sheath known as myelin

Grey matter

Contains primarily cell bodies of the neurons of the spinal cord, not covered in myelin

Dorsal horn

The location of axon terminals of sensory neurons

Lateral horn

The location of cell bodies of neurons of the autonomic nervous system

Ventral horn

The location of cell bodies of somatic motor neurons

Dorsal root

Bundle of axons, collectively called a nerve, that travel to the posterior horn

Dorsal root ganglion

The location of cell bodies of sensory neurons

Ventral root

Bundle of axons, collectively called a nerve, that travel from the lateral and ventral horns