brain and behavior week 3

• why you need sodium channels

  • axon wrapped in myelin, allows myelin to move without leaks along the way

  • like a pool w ripples

  • dense myelin sheath allows insulation to keep the charge from losing/dissipating across axon

    • increases conduction velocity significantly

    • 10x conduction velocity because of the myelin sheath

• axons without sheath (black border in picture) are diseases

• axons with thin sheath (thin black border) are in recovery

• What happens in the synapse when axon makes contact with dendrite?

  • *on picture, it’s when orange (pre synaptic neuron) meets blue (post synaptic neuron)

  • could be seen as soup

    • soup is diffusing from pre to post synaptic

  • could be seen as sparks

    • pre and post synaptic cell has tight contact or a channel, and direct zaps of current is allowing communication

• otto loewi wanted to prove that communication between neurons is chemical

  • vagus nerve is part of parasympathetic nervous system (thus HR will go down)

  • heart 1 connect to electrical stimulate and HR went down

  • heart 2 not connected and HR went down too

    • meaning heart 2 be

  • explains that chemical synaptic transmission is slow

• presynaptic axon

  • synaptic vesicle on left with black dots containing neurotransmitter, the chemical that will release and travel to the post synaptic cell

  • vesicle binds/fuses with membrane and its contents release into soupy environment between pre and post synaptic cell

  • synaptic cell contained inside pre synaptic cell

  • imagine a boat that docks, once it docks it’s almost like part of the dock, then allowing people to come off the boat

  • the binding of the vesicle to the membrane is aided by the cation CALCIUM (VERY IMPORTANT)

    • green ports in the picture are calcium channels allowing the vesicle to become one with the membrane

    • whatever is released will bind to the post synaptic cell

• post synaptic dendrite

  • neurotransmitter released from pre to post synaptic membrane binds to receptors

  • receptors open ion channels (protein), aka transformational change

  • if NT is excitatory, sodium enters, allowing positive charge to depolarize membrane closer to threshold

    • generates EPSP - excitatory postsynaptic potential

      • graded polarization (increases incrementally, not just a shoot up in charge)

    • balances by adding positive to negative charge existing in the membrane

  • if NT is inhibitory, chlorine enters, allowing negative charge to hyperpolarize membrane further from threshold

    • generates IPSP - inhibitory postsynaptic potential

      • graded hyperpolarization - decreases incrementally, not drastic change of charge immediately)

    • becomes even more negative (already negative inside)

    • you cannot generate an action potential if chlorine comes in

  • different receptors have different functions

• neurotransmitter released needs to be taken back up

  • pre synaptic cell has membrane that in pinched from the inside

  • when pinched, it takes the NT with it

  • then forms place for next synaptic vesicle to bind and fuse

3.2 (wed)

• catch up lecture 4

• catch up lecture 5 slide 9

• electrophysiology used in labs across the world

• coordination of excitation and inhibition

  • contracting muscles in leg, opposing muscles in the leg, information communicating to spinal cord (involuntary - your brain is not actively making the decision)

  • flexor and extensor, one pathway being excited, one pathway being inhibited, excitation pathway will win every time (think of a yo-yo)

• neural circuit slide, each example performs specified functions due to their wiring patters of excitation and inhibition

FOCUS POINT

• FAST NEUROTRANSMITTERS

  • glutamate

  • GABA

    • almost any drug you can think of works to inhibit or mimic glutamate or GABA

    • work to form object perception, speech, language, motor sequence initiation

• SLOW NEUROMODULATORS

  • noradrenaline

  • serotonin

  • histamine

  • hypocretin

  • dopamine

    • essentially change state of the brain

    • biasing of perceptual content

• ^^^you need both slow and fast as they attend to specialized functions’

• next slide shows binding of pre to post-synaptic cell involves glutamate and GABA, those are what is getting blocked when drugs are taken. that process is getting blocked.