module 5

Neurons

are the basic elements of the nervous system.

glial cells

Neurons are physically

held in place by

glial cells

•  provide nourishment to neurons, insulate them, help repair damage, and generally support neural functioning

Dendrites

there’s a cluster of fibers at the end of every neuron that are called

Dendrites

are the part of the neuron that receives messages from other neurons.

axon

On the opposite side of every neuron is a long, slim, tube-like extension called

axon

carries messages received by the dendrites to other neurons.

terminal buttons

Axons end in small

bulges called

terminal buttons

send messages to other neurons.

myelin sheath

axons are insulated by

myelin sheath

•  a protective coating of fat and protein that wraps around the axon like the casing on links of sausage.

Myelin sheath

• Also serves to increase the velocity with which electrical impulses travel through axons.

myelin

Those axons that carry the most important and most urgently required information have the greatest

concentrations of

all or none law

• states that a neuron always fires an action potential at maximum strength once a specific electrical threshold is met, and it will not fire at all if that threshold is missed 

resting state

when a neuron is not giving signals

action potential

When the positive charge reaches a critical level, the “trigger” is pulled, and an electrical impulse, known as an travels along the axon of the neuron

action potential

moves from one end of the axon to the other like a flame moving along a fuse.

mirror neurons

•  neurons that fire not only when a person enacts a particular behavior but also when a person simply observes another individual carrying out the same behavior

synapse

is the space between two neurons

synapse

where the axon of a

sending neuron communicates with the dendrites of a receiving neuron by using chemical messages.

neurotransmitter

When a nerve impulse comes to the end of the axon and reaches a terminal button, the terminal button

releases a chemical messenger called a .

neurotransmitter

carry messages from one neuron

to another neuron.

excitatory messages

are chemical messages that

make it more likely that a receiving neuron will fire and an action potential will travel down its axon.

inhibitory messages

provide chemical information that

prevents or decreases the likelihood that the receiving neuron will fire.

reuptake

is the process in which a neurotransmitter produced by a terminal button is reabsorbed by the

terminal button.

acetylcholine

• is involved in our every physical move because—among other things—it transmits messages relating to our skeletal muscles.

acetylcholine

• also aids in memory capabilities. In fact, diminished production of it may be related to Alzheimer’s disease

glutamate

memory

gamma amino butyric acid

which is found in both the brain and the spinal cord, appears to be the nervous system’s primary inhibitory neurotransmitter.

gamma amino butyric acid

• It moderates a variety of behaviors, ranging from eating to aggression.

dopamine

which is involved in movement, attention, and

learning.