psych 101 ch.3- Biology and Behavior

central nervous system

the brain and the spinal cord

peripheral nervous system

all nerve cells in the body that are NOT part of central nervous system- includes autonomic and somatic nervous systems

somatic nervous system

controls voluntary reactions (walking, running, typing, moving head

autonomic nervous system

controls involuntary reactions (breathing, heartbeat, digestion, salivation)

neurons

cells that receive, integrate, transmit info into nervous system.

they operate through electrical impulses, communicate with each other thru chemical signals, and form neural networks

dendrite

branchlike extensions of a neuron that detect information from other neurons

cell body (soma) of neuron

site where info from other neurons is collected and integrated

axon

long, narrow outgrowth of neuron. here information is conducted from cell body to terminal buttons.

terminal buttons

at the end of axons, small nodules that release chemical signals from the neuron into the synapse

synapse

gap between the axon of the sending neuron and dendrite of the receiving neuron: the site at which chemical communication occurs between neurons

3 basic phases of neuron communication and what happens in each

1. reception: chemical signals received from neighboring neurons'

2. integration: incoming signals assessed

3. transmission: signals passed to other receiving neurons

sensory neuron function

detect information from physical world and pass onto brain

somatosensory nerve function

provide information from skin and muscles to brain

motor neurons

direct muscles to contract/release, thereby producing movement

interneuron function

communicate witin short-distance circuit (smooth out communication between neurons)

action potential

AKA neuron firing: the electrical signal that passes along the axon and causes the release of chemicals from the terminal buttons

membrane potential

the difference in electrical charge between the outside of a membrane and the inside

resting membrane potential

membrane potential of a neuron at rest (should be around -70)

K+ ion channels and Na+ ion channels

passive transport- allow either K+ or Na+ ions to travel through. there are more K+ channels than Na+, so K+ flow in and out at a higher rate, so there’s more Na+ outside than inside. The ion channels are trying to make equilibrium between sides of the membrane, but only care about their specific ion

neuron function: neurons are powered by ____ and communicate with ofther neurons through ______.

1. electrical impulses

2. chemical signals

explain the Na+/K+ transporter

pumps 3 Na+ out and 2 K+ in per cycle. This creates a -1 charge per cycle. This drives ion channels to leak to maintain equilibrium of their corresponding ion.hew

which are there more of? Na+ or K+ channels? what affect does this have?

there are more K+ ion channels. this means that more K+ leak out of neuron than Na+ leaking into neuron, meaning the inside becomes less positive (more negative)

explain resting membrane potential and why it’s -70

1. sodium-potassium pump moves 3 Na+ out for every 2 K+ coming in. this makes the outside have more Na+ and the inside have more K+.

2. ion channels are trying to maintain equilibrium for number of their corresponding ion in vs. out- more K+ flows out because there are more K+ channels

3. this leads to the inside having a slightly more negative charge (inside-outside charge= resting membrane potential (-70)

voltage gated ion channels

ion channels that operate based on the electrical charge of the neuron. threshold for them to open: when electrical charge reaches -55 mv

what’s happening during polarization phase

there’s more Na+ outside than inside bc there’s not that many channels to let it go in. the cell receives the signal from dendrites to fire and more ions flood through regular channels

what’s happening during depolarization phase

membrane potential reaches -55 mv, voltage gated ion channels open. Na+ starts flooding into cell and membrane potential dramatically increases as inside of the cell becomes more positive

repolarization phase

neuron reaches peak membrane potential (-30 mv) and vg Na+ channel closes. voltage gated K+ channel opens bc there are too many K+ inside the cell, so they flow out. This leads to dramatic decrease of membrane potential back to around -70

hyperpolarization phase

as K+ ions continue exiting, membrane potential drops down below the resting -70 mv. when it gets around -75 to -80, the vg K+ channel closes and the sodium potassium pumps and leak channels work to bring membrane potential back to -70.

relative refractory period

the brief amount of time after an action potential when a neuron’s membrane potential is more negative than -70, making it harder for it to fire again.

back to resting phase

leaky channels and pumps bring membrane potential back to -70

explain where action potentials occur

they occur in the cell body/soma. the signal travels down the axon to the terminal buttons by occuring at each unmyelinated area (node of ranvier). The Myelin sheath on the axon protects the signal as it travels.

nodes of ranvier

small parts of exposed axon that are unmyelinated. where action potentials take place during traveling

saltatory conduction

process of action potentials “jumping” from node to node down the axon preserving og signal.

synaptic communication/chemical transmission explained (trasmitting signal to next neuron)

neurotransmitters released out the terminal buttons into synapse swim around and try to meet their receptor at the next neuron’s dendrite and bind to it. Once they click, they open up ion channels and ions flow into the next neuron’s membrane. then action potential is changed

presynaptic vs postsynaptic

pre: gives signal to neuron

post: receives signal from neuron

excitatory signals

depolarize the membrane, increasing the likelihood that neuron will fire

inhibitory signals

hyperpolarize the membrane, decreasing the likelihood that neuron will fire

integration

information received from multiple dendrites should be strong enough to generated action potential at cell body

all or none principal

the principal that a neuron either fires or not, it cannot partially fire. and it fires with the same potency each time

when does an action potential occur

when the sum of inhibitroy and excitatory signals leads to a positive change in voltage that exceeds neuron’s firing threshold (-55)