THE NEURONES+ SYNAPTIC TRANSMISSION

LECTURE 2 + 3

WHAT ARE NEURONS

receive and transmit information in electrochemical form

WHAT ARE GLIAL CELLS

act as helper cells - support the neuron’s in function- structure cleaning etc

WHAT ARE DENDRITES

• receives information from other neuron’s-

• the surface is lined with synaptic receptors responsible for bringing information into the neuron 

WHAT ARE AXONS

• thin fibre responsible for transmitting nerve impulses to other neuron's , organs or muscles

• covered in myelin sheath

WHAT ARE AXON TERMINALS

• transmits communication for the next neuron

• releases chemicals to communicate with other neurons

WHAT IS A MEMBRANE

• contains phospholipid bilayer 

• uncharged molecules- etc h2o co2 can pass through

WHAT IS THE ENDOPLASMIC RETICULUM

transports proteins to other cell locations

WHAT ARE DENDRITE SPINES

• they branch other and increase the surface area of the dendrite

• more surface area = more information can be received

WHAT IS MULTIPOLAR NEURON

many dendrites on a single axon

WHAT IS A BIPOLAR NEURON

single dendrite at one end a single axon at the other end

MONOPOLAR NEURONS

a single branch extending in two directions- soma is in the middle

WHAT IS AN AFFERENT NEURON

• receiver 

• information comes in 

• found in central nervous system and peripheral nervous system 

• eg- sensory neuron which receives sensory input

WHAT IS AN EFFERENT NEURON

• sends information away from the structure

• found in central nervous system and peripheral nervous system

• example- motor neurone - sends impulses to muscles or glands

WHAT ARE RELAY NEURONS

• the dendrites and axons are completely contained within a single structure

• an example is the spinal cord 

• connection point between motor and sensory neurone 

WHAT IS ASTROCYTES

• type of glial cell

• largest

• wraps around blood vessels and cell bodies

• removes waste materials created when neurons die

• also allows synapse formation

WHAT IS MICROGLIA

• smallest type of glial cells

• removes waste material-viruses fungi etc

• functions as part of the immune system 

• protects brain from invading microorganisms

WHAT ARE OLIGODENDROCYTES

• type of glial cell

• myelinates multiple axons in central nervous system

WHAT ARE SCHWANN CELLS

• type of glial cells 

• myelinates single axons in peripheral nervous system

WHAT ARE RADIAL GLIA

• type of glial cells

• guide migration of neurons growth of their axons and dendrites during embryonic development 

WHAT IS MYELINATION

• conduction

• sits around the axon and wraps around

WHAT IS MEMBRANE POTENTIAL

• the difference in electrical charge between the inside and outside of the cell 

• inside is more negative than the outside 

WHAT IS THE RESTING POTENTIAL

• state of the neuron at resting 

• prior to sending of a nerve impulse 

• ready to act at this state 

WHAT IS NEURON MEMBRANE

layer of fatty cells around the neuron maintains electrical gradient this is because it is semi permeable so it does not let ions of other charges in

WHAT IS THE ROLE OF PROTEIN CHANNELS 

open to allow certain specific ions to enter- this it to change the charge inside the cell

WHAT IS INRACELLULAR

within the cell

WHAT IS EXTRACELLULAR

outside the cell

WHERE IS SODIUM IONS FOUND DURING RESTING POTENTIAL

• many are found outside the cell

• 10x more outside than inside 

WHAT ARE ANIONS

they are inorganic ions which have a negative charge and remain on the inside of the cell- they contribute to the negativity of the inside of the cell

WHERE IS POTASSIUM FOUND

• inside the cell- has a positive charge

• 20x more inside than outside 

WHAT IS ELECTROSTATIC GRADIENT

• opposites attract 

• own charges repel

WHAT HAPPENS TO SODIUM IONS WHEN THE MEMBRANE IS OPEN

• Na+ diffuses down its concentration gradient inside neurone

• Na+ is also attracted to negative anions via electrostatic gradient and moves towards it on the inside of the cell

WHAT HAPPENS TO POTASSIUM IONS WHEN THE MEMBRANE OPENS

• electrostatic pressure pulls potassium ions inside the neurone - positive  is attracted to negative anions

• but concentration gradient pushes it  out of the neurone - because diffusion

• so forces are balanced 

• electrostatic gradient isn’t as strong 

HOW IS THE RESTING POTENTIAL MAINTAINED

• sodium potassium pump

• pumps 3 Na+ out of the cell

• pumps 2 k+ inside the cell 

• energy from mitochondria

• more positive charge out than in 

• works against concentration gradient and electrostatic gradient 

WHAT IS HYPERPOLARISATION

• increasing polarization or difference between the electrical charge of two places

• basically when the cell membrane potential becomes more negative than its resting potential

•  occurs during the refractory period 

WHAT IS DEPOLARISATION

• decreasing polarisation towards zero or no polarity

• basically inside is more positive than the outside 

WHAT IS THRESHOLD OF EXCITEMENT

• level above which any stimulation produces a massive depolarisation 

STAGES OF DEPOLARISATION

• depolarisation to excitation threshold 

• voltage gates Na+ channels open

• allowing Na+ ti enter the neurone 

• influx neuron until it is -40

• K+ membrane pushed out because inside is to positive and is repelled

• refractory period