cells of the nervous system (2)

axons

nerves are bundles of __________

12

how many pairs of cranial nerves are there?

31

how many pairs of spinal nerves are there?

there is an equal number

are there more neurons or glial cells in the brain?

glial cells

support and protect neurons; provide energy and nutrients from the bloodstream

no

do glial cells generate action potentials?

glucose from the bloodstream

where do glial cells acquire the nutrients and energy they provide to neurons?

astrocytes, oligodendrocytes, microglia

3 types of glial cells

astrocytes

most abundant type of glial cell in the brain

forming the BBB, maintaining ion and NT concentrations, phagocytosis, gliosis

4 main functions of astrocytes

glutamate

NT that must be maintained in a specific range in the brain (by astrocytes)

phagocytosis

the process of engulfing and digesting dead cells and debris

phagocytosis

__________ is performed by astrocytes during concussion

gliosis

the process of forming scar tissue in the brain following injury

neurologically active

scar tissue in the brain prevents the area from being __________ but aids repair

blood vessels, neurons, glucose

tendrils from astrocytes attach to __________and __________; transport __________ to neurons

lactate

when highly active, neurons also use __________ in addition to glucose as a source of energy

organs, brain, BBB

study involving dye injected into animals: __________ were coloured but not the __________ due to the __________

2 layers, capillaries

the BBB is formed by __________ of tightly packed cells lining __________  in the brain

larger gaps between cells

in the rest of the body (besides the BBB), __________ allow greater movement of substances in and out of tissues

area postrema

weak area of the BBB

gag reflex, motor neurons

in the area postrema, the __________ can stimulate __________ to eliminate toxic chemicals

forming the myelin sheath

what is the main function of oligodendrocytes?

nodes of ranvier

areas along an axon without myelin

insulates, speeds up

myelin __________ neurons and __________ APs

CNS only

oligodendrocytes are found in the __________

schwann cells

PNS equivalent to oligodendrocytes

withstand injury

schwann cells can __________, which differentiates them from oligodendrocytes

phagocytosis, protecting from invasive viruses, secreting pro-inflammatory chemicals

3 main functions of microglia

cytokines

pro-inflammatory chemicals secreted by microglia

lymphocytes

due to the BBB, there are few __________ in the brain, which emphasizes the importance of microglia

electrical strength, weaken

longer dendrites degrade __________ , causing potentials to __________

anterograde flow

flow from the soma of a cell down the axon to the terminal buttons

retrograde flow

flow from the terminal buttons of a cell down the axon to the soma

microtubules

run the length of an axon and transport chemicals via motor proteins

contains DNA, transcribes genes for protein synthesis

2 important functions of the nucleus of a neuron

nucleus

which part of the neuron receives glucose from astrocytes?

cytoplasm

part of the neuron that contains organelles

ribosomes

organelles that are important for translation

cytoskeleton

part of the neuron containing microtubules

within the nucleus

where does transcription occur?

on ribosomes outside the nucleus

where does translation occur?

action potential

wave of changed polarity from negative to positive inside the axon

axon hillock

where do action potentials begin?

-70mV

resting membrane potential

-55mV

firing threshold

depolarization

when a cell becomes less negative inside

hyperpolarization

when a cell becomes more negative inside

+40mV

charge that the inside of axons suddenly reach after reaching the firing threshold

ion channels open and positively charged ions are able to enter the cell

how does a cell’s polarity rapidly change from the firing threshold to a positive charge?

outside the cell, inside the cell, closed

at rest, there is more Na+ __________ and more K+ __________ and ion channels are __________

voltage-gated

which type of channel are Na+ channels?

Na+ channels open, Na+ enters the cell rapidly, the inside of the cell becomes positive, K+ channels open, K+ exits which returns the cell to negative

5 steps which occur when a cells reaches the firing threshold

force of diffusion, electrostatic pressure

2 forces that cause ions to move in/out of cells

Na+/K+ pump

returns ions to their initial distribution after a cell fires

it has to push ions against the force of diffusion

why does the Na+/K+ pump require a lot of energy?

negatively charged proteins

in addition to Na+ and K+ ions, there are also __________ inside the cell that cannot leave

refractory period

period after firing during which a neuron cannot generate another action potential while the resting membrane potential is being restored

glucose and lactate

sources of energy for the Na+/K+ pump

3 Na+ out, 2 K+ in

how many ions of each type does the Na+/K+ pump transport in order to restore resting potential?

rate of firing

the rate law: since the magnitude of an AP is always the same, the strength of a stimulus is represented by the __________ of an axon

neurotransmitter

the rate of firing of a cell determines how much __________ will be released

nodes of ranvier

ion channels only exist at the __________

saltatory conduction

process by which APs “skip” along a myelinated axon

myelinated axons

saltatory conduction ONLY occurs in __________

saltare

the term “saltatory conduction” is derived from which latin word meaning “to dance” to “to skip”?

EPSP

depolarizing effect caused by neurotransmission

IPSP

hyperpolarizing effect caused by neurotransmission

gene expression

in addition to depolarizing/hyperpolarizing effects, neurotransmission can also alter __________

axodendritic

synapses located on the dendrites of post-synaptic neurons

axosomatic

synapses located on the somas of post-synaptic neurons

axoaxonal

synapses located on the axons of post-synaptic neurons

spines

axodendritic synapses can be __________ on some dendrites

calcium

if __________ channels are blocked, then all neurotransmission is blocked

calcium channels

when an AP reaches the nerve terminal, __________ open

diffusion

force by which calcium enters the pre-synaptic cell

rate of firing

the amount of calcium that enters the pre-synaptic cell is proportionate to the __________

vesicles

when calcium enters the cell, __________ fuse with the pre-synaptic membrane

pores

__________ on the pre-synaptic membrane open to expel molecules of NT into the synaptic cleft

diffuse

NT molecules __________ across the synapse to bind to post-synaptic receptors

polypeptides

type of NT produced in the soma and transported down the axon to the terminal

reuptake, enzymatic deactivation

2 mechanisms of termination of neurotransmission

reuptake

removal of a NT from the synaptic cleft by the terminal button, back into the presynaptic neuron

serotonin transporters

SSRIs block __________, which prevents reuptake

they protect NTs from being broken down by enzymes

why are vesicles necessary for transport?

ligand-gated

ion channels coupled to an ionotropic receptor are __________

immediate/direct

activation of ionotropic receptors has __________ effects

G protein

metabotropic receptors are coupled to a __________

second messengers

G proteins activate __________, which can then indirectly produce an intracellular change

take longer to begin and last longer

effects caused by activation of a metabotropic receptor __________

ions

do ions or NTs enter the post-synaptic neuron?

IPSP

potential caused by a negatively charged ion entering the cell

EPSP

potential caused by a positively charged ion entering the cell

direct

ionotropic receptor effects are __________

indirect

metabotropic receptor effects are __________

open an ion channel, activate a gene

2 functions that second messengers can do

synthesis and release of NTs

autoreceptors mostly regulate internal processes such as __________

negative feedback loop, inhibitory

due to autoreceptor regulation, too much NT located in the synapse creates a __________ which causes mainly __________ effects