Module 7 Vocabulary

myelin sheath

a fatty wrapping which speeds up the conduction of the action potential down the axon

potential difference

a measure of the charge difference across the cell membrane

as you read this question, cells in your eyes are sending information to your brain, which your brain uses to form an image of the words that you read. Is this information being sent along afferent (towards the CNS) or efferent nerves (away from the CNS)?

afferent nerves

collateral axons

axons that split off the main branch

oligodendrocyte

bings together and insulates CNS neurons

nerves

bundles of neuron axons and their coverings which are found outside the CNS

presynaptic neuron

carries signals to the synapse

soma

cell body that houses the nucleus

unit of a neuron

cell body, axons, and dendrites

ganglia

collections of neuron cell bodies that are found outside the CNS

peripheral nervous system (PNS)

composed of all the parts of the nervous system (PNS) that are not in the central nervous system (CNS)

central nervous system (CNS)

composed of the brain and the spinal cord

PNS

consists of nerves and ganglia

epineurium

covering of a nerve

endoneurium

covering of an axon

the strength of the stimulus

determines the frequency of the action potential

sympathetic division

division of the ANS that generally prepares the body for increased energy expenditure (the fight-or-flight division)

parasympathetic division

division of the ANS that regulates resting and nutrition related functions such as digestion, defecation, and urination

what are the differences between a sensory nerve, a motor nerve, and a mixed nerve? What is the most common kind of nerve in the body?

sensory neurons, which make up sensory nerves, can only send incoming messages to the CNS. Motor neurons, which make up motor nerves, can only send outgoing messages from the CNS to muscles or glans when a nerve carries both neurons, it is a mixed nerve. Most nerves in the body are mixed nerves.

nerves in the human body are either

sensory, motor, or mixed. The most common type is the mixed nerve

presynaptic terminals

terminal boutons or axon terminals

excitability

the ability to undergo an action potential in response to a stimulus

perineurium

the covering of a fascicle

oscillating neuron

the message stimulates itself

depolarization

the potential difference basically become zero

refractory period

the time when no action potential can be generated on the neuron because one in already in progress

inhibitory synapse

this type of synapse makes up the majority of neuron to neuron synapses in the body

resting potential

where the axon is not carrying any signal

name the 6 types of neuroglia and their functions

-oligodendrocytes: binds together and insulates CNS neurons -schwann cell: insulates PNS neurons -microglia: fight infection with phagocytosis -astrocyte: form the blood-brain barrier -ciliated ependymal cells: move cerebrospinal fluid -non-ciliated ependymal cells: secrete cerebrospinal fluid

somatic motor nervous system

PNS neurons that transmit action potentials from the CNS to the skeletal muscles

autonomic nervous system

PNS neurons that transmit action potentials from the CNS to smooth muscles, cardiac muscles, and glands

an axon is covered by several schwann cells. If it is severed, will it definitely heal? Why or why not?

No, not definitely. Unless the branching axon is pointing in the general direction of the severed end, it will not be able to heal

association neuron

a neuron that conducts action potentials from one neurons to another neuron within the CNS

multipolar neuron

a neuron with many processes: several dendrites but only one axon

unipolar neuron

a neuron with only one process and the cell body is suspended from that process

bipolar neuron

a neuron with two processes: an axon and a dendrite

local potential

a small change in the potential difference that just dies out because the stimulus that produced it was subthreshold

when you are digesting food, smooth muscles contract your stomach. Is this controlled by the afferent division of the PNS? You can be even more specific than that. What would be the most specific way to describe the nerves involved in this situation?

efferent neurons; autonomic division

microglia

fight infection with phagocytosis

astrocyte

form the blood-brain barrier

nodes of Ranvier

gaps in the myelin sheath

schwann cell

insulates PNS neurons

an axon is covered by an oligodendrocyte. Is it part of the CNS or the PNS? Will it regenerate a new axon, if severed?

it is part of the CNS. It is not able to regenerate an axon

convergent

many inputs lead to one limited output

spinal nerves

nerves that originate from the spinal cord (part of the PNS)

cranial nerves

nerves that originates from the brain (part of the CNS)

oligodendrocytes

neuroglia in the CNS

schwann cells

neuroglia in the PNS

afferent neurons

neurons that transmit action potentials from the sensory organs to the CNS (also called the sensory division). It carries signals from the sensory neurons: the tongue, ears, nose, etc.

efferent neurons

neurons that transmit action potentials to the effector organs (a.k.a. the motor division) It carries signals from the CNS to the effector organs

divergent

one message gets spread to different parts of the body

ependymal cells

one of the 6 types of neuroglia. There are 2 types of ependymal cells: non-ciliated ependymal cells which secrete cerebrospinal fluid and ciliated ependymal cells which move that cerebrospinal fluid