Lecture 3 - neurons, glia, membrane potentials

multicellular organisms require - to coordinate body functions and respond to the environment

signalling mechanisms

chemical signals travel via the

endocrine system

chemical signals include

hormones

electrical signals travel via the

nervous system

electrical signals travel along - in a cell to cell fashion

neurons

both chemical and electrical signals travel - to reach target cells, but in neuronal pathway there is a - between the neuron and target cell

long distances, direct cell to cell connection

endocrine system usually leads to

slower, more sustained responses

multiple sclerosis is when the

myelin sheath is degrading

afferent neurons are sensory neurons

conduct action potentials towards the CNS

efferent neurons are motor neurons

conduct action potentials away from the CNS to the organs

interneurons conduct action potentials - in the

between neurons, CNS

glial cells are more - than neurons

abundant

glial cells do not - and do not form - w neurons

generate or conduct AP, synapses

glial cells are non-neuronal cells that maintain -, form -, provide -

homeostasis, myelin, support and protection

schwann cell

a type of glial cell, forms myelin on motor and sensory neurons

oligodendrocyte

type of glial cell, forms myelin on neurons in CNS

astrocyte

type of glial cell, transport nutrients, remove debris in CNS

glial cells hold neurons in -, supply -, insulate -, destroy - and remove -

place, nutrients and oxygen, one neuron from another, pathogens, dead neurons

microglia

type of glial cell, removes debris and dead cells from CNS

ependymal cells

line fluid-filled cavities of CNS

white matter are

nerve axons that are mostly myelinated

grey matter is mostly

neuron cell bodies, unmyelinated axons and glial cells

white matter does what

transmits signals to grey matter

grey matter does what

processes information

neuronal membrane serves as barrier between

cytosol and extracellular fluid

neuronal membrane is embedded with

proteins that form channels and pumps

- varies in different parts of neuron

protein composition

• of neuronal membrane determines signals

membrane properties

three types of membrane transport

passive diffusion, facilitated diffusion, active transport

gated ion channels change - of membrane to certain ions

permeability

voltage gated ion channels open or close in response to

change in membrane potential

ligand gated ion channels open when

specific regulatory molecule binds

mechanogated ion channels open or close inn response to changes in

cytoskeleton with which they are interacting

sodium potassium ATPase pumps - the cell, both against gradient to maintain -

3 sodium ions out while pumping 2 potassium ions inside, resting membrane potential

gradients are a form of energy storage,

potential energy

uncharged molecules across a membrane can only form a

chemical gradient

charged molecules can form

electrochemical gradients

all transport processes affect -, some transport processes affect -

chemical gradients, electrical gradients

electroneutral carriers transport - molecules or exchange an -

uncharged, equal number of particles with the same charge

electrogenic carriers transfer a

charge

membrane potential is a difference in

charge inside and outside the cell membrane due to ion concentration gradients formed by active transport

two main functions of the membrane potential:

provide - for -, and changes in membrane potential are used by cells in

energy, membrane transport, cell-cell signalling

electrical potential difference across membrane exactly balances the

concentration gradient

ion diffuses down its concentration gradient until a charge gradient is built up that exactly counterbalances the chemical gradient, resulting in an equilibirum at which there is

no further net movement of the ion

• at which the ion is at electrochemical equilibrium

Eion is the Vm

membrane potential is the difference in - between -

electrical potential, interior and exterior of a cell

goldman equation accounts for varying

ion permeability and multiple ion gradients

the gradients of sodium and potassium across the cell membrane largely determine the

resting membrane potential

factors that contribute to membrane potential

distribution, permeability, and charges of ions

when voltage-gated channels are closed, the membrane is much more permeable to

K+ than to Na+

changes in membrane potential act as - signals

electrical

neurons depolarize or hyperpolarize by selectively altering membrane - via -

permeability, ion channels

gated ion channels that open or close in response to a stimulus is an example of

ligand gated ion channels

depolarization is when cell becomes more - on the inside, if - ions enter

positive, Na

hyperpolarization is when cell becomes more - on the inside, if - ions leave

negative, K

at rest, all gated ion channels are

closed