Chapter 3 - Biological Foundations of Bahaviour

Cell body/Soma - contains biochemical structure needed to keep neuron alive - nucleus carries genetic info that determines how cel will develop and function Dendrites - branch like emerging from cell body - collects messages from other neurons, send them to cell body Axon - extends from cell body, conducting electrical impulses to other neurons, muscles or glands - connects with dendrite branches from other neurons

100 billion, loosing 10,000 every day

They surround neurons and hold them in place - made up of fatty tissue - also manufacture nutrients from myelin sheath, absorb toxins and waste - guide newly divided neuron to place during brain development

prevents substances from entering brain

• neurons are surrounded by a positively charged liquid environment (Na+) • inside of the neuron is negative (Cl- and negative protein ions) • the resting potential across the membrane is -70mV

Action potential (nerve impulse) is a sudden reversal in neuron’s membrane voltage - depolarization occurs; changes from -70mV to +40 - only occurs if the graded potential reaches action potential threshold, about -55mV (obeys all or none law) - This change occurs due to ion channels, which open allowing a rushing in of Na+, making the neuron less negative (depolarization) - Ion channels then close, K+ channels open and the positive ions go back to their respective positions outside the cell - resting potential is restored

time period during which the membrane is not excitable and cannot discharge another action potential - occurs immediately after impulse passes - limits rate at which action potential can be triggered (300 impulses/sec in humans)

• a fatty, whitish insulation layer derived from glial cells that covers axons • thins out at regular intervals, called the nodes of renvier • allow for higher conduction speeds along axon and faster transmission time • prevents loss of signals

a neuron at resting potential

a neuron which sodium channels have opened and Na+ has rushed into the cell making it positive

a change in a cell’s membrane potential that makes it more negative

Bipolar - an axon and one dendrite extending from the cell body toward opposite poles Multipolar - multiple dendrites and a single axon. Unipolar - neurons have one axon (usually the cell body on the side of the axon)

Will depolarize postsynaptic membrane (EPSP) making it positive

Hyperpolarizes membrane (IPSP) making it negative

if you were to get two epsp’s you could add them together to get the total effect of both of them same with ipsps or if you have an ipsp and epsp that are equal, they will cancel each other out

Otto Loewi

• neurons don’t touch each other • tiny space between axon terminals to dendrite of the next neuron

Synthesis - chemical molecules formed inside neuron Storage - Molecules stored in synaptic vesicles Release - Action potential causes vesicle to move to surface of terminal, molecules are releases into fluid-filled space Binding - molecules cross the space and bind to receptor sites (large protein molecules embedded in the membrane) Deactivation

Sherrington he suggested that the transmission from neuron to neuron was not electrical but rather chemical

the chemicals found in synaptic vesicles that travel across synapse during synaptic transmission

Excitation - depolarizes next neuron - makes post-synaptic neuron more likely to fire - causes sodium to enter postsynaptic neuron Inhibition - hyperpolarizes (more negative), - causes action potential to not occur - changes the potential from -70mV to -72mV this makes it more difficult to excite the neuron to the threshold and cause action potential, thus inhibiting neuron

shape

seizures are caused by a lack of inhibition

True! depends on the type of receptor