Part 3: Neurons and Synapses

Ramon y Cajal

who established the Neuron Doctrine

Neuron Doctrine

what states that the brain is made of many small cells

100

there are almost _______ billion neurons in the human brain

membrane, nucleus, and specialized organelles

neurons, like other cells, have these three parts

dendrites, soma, axon, and axon terminals

the four important regions of neurons

dendrites

branching projections that collect information in neuron

soma (cell body)

contains the nucleus and integrates information

axon

conducts the neural signal in neuron. transmit electrical impulses to other neurons, muscles, and glands

axon terminals

small swellings that release signals to other neurons (outputs info)

synapses

neurotransmitters (chemical signals) cross small gaps, known as ________

neurotransmitters

___________ are released by the presynaptic cell to affect the postsynaptic cell

500

there are about _______ trillion synapses in the adult brain

sensory neurons

these neurons carry information to the brain

function

different types of neurons can be classified by their ___________

motor neurons

these neurons carry information from the brain to the muscles

interneurons

these neurons convey signals around the nervous system

glial cells

these cells speed up neuronal signaling, regulate extracellular chemicals, and enable neurons to modify connections

oligodendrocytes and Schwann cells

these two things wrap myelin around axons to speed up signals

astrocytes

these regulate extracellular chemicals and local blood flow

microglia

what provides immune system functions for the CNS

receptors

specialized proteins in the cell membrane

postsynaptic

neurotransmitters interact with receptors to affect the ____________ cell

ionotropic receptors

these receptors allow ions to flow across the membrane, changing the charge of the cell membrane

metabotropic receptors

these receptors relay information into the cell using a series of proteins

receptors

neurotransmitters only bind to _________ briefly and then are removed

degradation

when the neurotransmitter is broken apart

diffusion

when the neurotransmitter moves down the concentration gradient and out of the synapse

reuptake

when the neurotransmitter is transported back into the original cell

voltage difference

at rest, there is a _______ _______ between the inside and the outside of the cell

negative; -70

the inside of the cell is normally more _______ than the outside (about ______ mV)

excitatory postsynaptic potentials

________ _________ _________ move the membrane voltage closer to 0

inhibitory postsynaptic potentials

_________ __________ ________ move the voltage further from 0. they are small and fast

action potentials

_______ _______ are all or none

soma; membrane voltage

the ________ receives 100s or 1000s of PSPs at the time - EPSPs and IPSPs combine to affect the ______ _______

depolarize

EPSPs sum together to _____________ the cell

depolarization

when the voltage moves closer to 0

action potential

if the membrane voltage reaches threshold (approx -60 mV), an ________ _______ is generated

Na+; K+

How an action potential travels part 1: at rest, there are more ______ ions outside of the cell and more _______ ions inside the cell

Na+; chemical; electrical

How an action potential travels part 2: threshold, voltage-gated ______ channels open, allowing the ions to flow in, down the ________ concentration and _________ gradients

K+; repolarize

How an action potential travels part 3: voltage-gated ______ channels open, and the ions flow out to _______ the cell

Na+; depolarize

How an action potential travels part 4: current formed by the _______ ions flow down the neuron to ___________ the next part

refractory period

How an action potential travels part 5: a _______ _______ follows the action potential, when voltage gated Na+ ion channels are less likely to open

calcium; chloride

How an action potential travels part 6: ________ and ________ ions also contribute to the action potential

myelination

this makes action potentials travel faster

nodes of Ranvier

myelin is interrupted by _______ ___ _______, where the action potential is regenerated

transmission

action potentials jump from node to node which speed up ________

decreases

myelination ________ the amount of energy used by the neuron

communication

when myelin is damaged, ____________ in brain is critically compromised

voltage-gated

action potentials cause _____ ______ calcium channels to open in the axon terminals

calcium ions

_______ ______ cause vesicles with neurotransmitters to bind to the presynaptic neuron

synapse

when neurotransmitters are released, they cross the _______