EXSS 155; 8A, Neurons and synapses

What are neurons?

A functional unit of the nervous system

What do neurons do?

• Form complex processing network in brain

• Connect all parts of nervous system to CNS

• Electrically excitable

What are neurons responsible for?

• Sensing

• Thinking

• Remembering

• Muscle control

• Gland regulation

What are neuroglia

• Glial cells

• Are smaller but greater in number than neurons

• Provide support for neurons

• Form myelin

• Maintain homeostasis

What are the three main components of a neuron?

• Dendrites

• Cell body (soma)

• Axon (forms nerve)

What do dendrites do?

Receive stimuli from chemically gated channel activation

What does the cell body(soma) do?

Recieves stimuli and produces EPSP or IPSP

What does the axon do?

• Propagates impulses

• Terminals and end bulbs: inflow of Ca2+, vesicles with neurotransmitters, neurotransmitters release

What is a myelin sheath

• Multilayered lipid

• Insulates axon

• Increase nerve conduction velocity

• The nucleus is a Schwann cell

• Nodes of ranvier in between sheaths

What is multiple sclerosis

• Degradation of myelin sheaths

• Neurons become ineffective and cause muscle atrophy and decreased coordination

What is a synapse?

Junction between neuron and effector cell or two neurons

What is the difference between post/presynaptic terminals

• Presynaptic sends impulse

• Postsynaptic recieves inpulse

What are the two different synapses

• Electrical are called gap junctions

• Chemical are called synaptic cleft

How do electrical synapses work

• Ion current spreads to the next cell through gap junctions

• Faster, two way transmission, capable of synchronizing neurons

How do chemical synapses work

• One way transfer from pre to postsynaptic neuron

• Neurons/cells don’t and are separated by synaptic cleft

How can neurotransmitter effects be modified

• Synthesis

• Release

• Removal

• Receptor site blocked or activated

What is the difference between an agonist and antagonist

• Agonist enhances effect of neurotransmitter

• Antagonist blocks neurotransmitter

What are some common neurotransmitters?

Small molecule:

• ATP

• ACh

• Amino acids

• Amines (dopamine, serotonin)

Neuropeptides

• Substance P

• Endorphins

• Horomones

• CCK