Lecture 2 - The neuron

Specialised cells that receive, assimilate and pass on info. They are electronically excitable and generate an electircal impulse

Afferent Efferent Interneurons

Carry signals away from sensory organs, towards CNS E.g. pain/ stretch receptors

Opposite to afferent, carry signals from CNS to muscles and glands in PNS

Only found in CNS, make up 99% of neurons, change signals, intergrate info and relay it

Unipolar, Bipolar and Multipolar

• Dendrites dont come from soma, they’re on seperate branches • Transmits sensory info - touch/pain, temperature, pressure

• Soma is in middle, no dendrites, but a receptor cell instead • transmits just auditory/ visual sensory info

• Most common in cns • either motor or interneurons • Populate skeletal muscle

1) Astrocytes 2) Oligodendrocytes 3) microglia

• clean up debris (like dead cells) via phagocytosis - engulf them • Regulate chemical composion of extracellular fluid • Provide Nourishemtn (lactate) • Form scar tissue - flood area of dead cells • Provide physical support - keep in place • Stop signals getting scrambled

• Suppor axons, produce myelin sheath - fatty tissue wrapped around tightly • Electrical insulation to increase processing speed

• Act as phagocytes • Active immune system - protect brain from invadign mirco-organisms • Inflammatory reaction to brain damage

• Olig - only in CNS, branch out to wrap multiple sections of different neurons - but at the end of these branches are cells like scwhann, but are still prat of oligo • Schwann - only in pns, wrap axon in its entirety, not connected to oligo, dont branch out

Electircal (ions) • resting membran potential • graded potentials • AP

Biochemical • synapses • NT’s • Activation of post-synaptic cells

Its a lipid bi-layer • two layers of fat like molecules - act like a barrier • Inside is hydrophobic • outside is hydrophillic Inside = intracellular fluid, outside = extracellular fluid

Contains different electrically charged ions

Cations - POSITIVE CHARGE (e.g. potassium/ sodium) Anions - NEGATIVE CHARGE (e.g. chlorine)

Movement of ions in/ out of the cell via channels or pumps

Inside: RELATIVELY NEGATIVE - MORE K+ outside: RELATIVELY POSITIVE - MORE NA+ AND CL-

• Diffusion - ions want to move from areas of high concentration to low • Electrostatic pressure - ions want to move away from similar charged ions

They want to move outside, as they are usually inside - they want to go outside due to diffusion, as there is less oustide. But then they want to move back in as the inside is negatively charged, and they are in a positive outside - so move back in due to electrostatic pressure. This creates stability and a resting potential

Want to move inside where it is oppositely charged (opposites attract) but then want to move outside because of diffusion This creates stability and a resting potential