Week 3 - Biological Foundations of Behaviour - Neurons and Action Potentials

The Nervous System (create a chart)

• Central nervous system (CNS)

  • brain and spinal cord

  • Nerves are always encased in bone

• Peripheral nervous system (PNS)

  • Branches that go outwards from the spinal cord

  • No encased in bone

  • Types of systems

    • Somatic nervous system

    • Autonomic nervous system

      • Sympathetic nervous system

      • Parasympathetic nervous system

Neurons

• what are they

• How do they operate

• How to communicate with other neurons

The Types of neurons

• 3

• are the basic units of the nervous system

• Operate through electrical impulses

• Communicate with other neurons through chemical signals

Types of neurons

• Sensory neurons: toward the central nervous system

• Motor neurosurgeon : away from the central nervous system to glands muscles, etc

• Interneurons: between sensory and motor neurons (back and forward)

Parts of the neuron

• Dendrites: branch-like sensations from the neuron and detect information from other neurons (increase receptive feel with the increase of branches)

• Cell body: collecting all the information coming in from the thousand of neurons sending information

• Nucleus

• Axon: transmit to other neurons (the connection) (axon can be as long of the base of the spine to the base of the foot)

• Myelin Sheath (myelinated axon): an insulating layer around axons that increases conductions between neurons and rapid transmutations of action potentials

  • very helpful if you need to react to burns, heat, pain faster

• Glial cell (Schwann cell): help form the myelin sheet

• Nodes of Ranvier: information jumps on node of ranvier

• Terminal buttons: when firing an action potential, information goes to the synaptic cleft

Neurons Communicate via Action potentials

When do neurons fire?

• types of signals

• What is resting potential

• excitatory signals will make the neurons less negative, depolarize, increasing the likelihood that the neuron will fire

• Inhibitory signals will hyper polarize and decrease the likelihood of the neuron firing

When do neurons generate an action potential

• only if the extort input will reach a certain threshold

What is the all-or-none principle

• a neuron will fire with the same magnitude each time

• Will or will not fire

• but the frequency of firing will vary

What occurs during the resting potential

• the ions

• Neurons are polarized at rest (-70 mV)

• More sodium ions outside

• more potassium ions inside

  • Contributes to the polarized nature of the cell

  • More negative inside than outside

• gated channels

  • Sodium channels: closed

  • Potassium channel: closed

  • Prevent them from moving around to balance the solution

  • Na+ and K+ transporter ion moves Na out and K in

Depolarization

• sodium channels open up

  • Sodium ions come into the cell, into the axon

• shifts the electric potential: making inside more positive

Peace action potential and hyper polarization

• Potassium gates open: potassium will flow up, and the gate quickly closes - creating hyperpolarization

• Will make the inside more negative

• the refractory period: 3 Na out and 2 potassium inside with one ATP molecule

  • Allows to restore resting potential for another action potential

Local current

• the flow sodium ions isn’t enough for the action potential begins

• Therefore must reach -55 mV

Saltatory Conduction

• myelated vs unmyelinated axons

• Saltatory spread: slow spread of information travelling for unmyleated

  • Results in the jumping

  • Up to 50 times faster

• Slow spread