WARM UP “The secret of action is to begin.” What does this mean to you? How can you apply this to Biology II?

Nerve Tissue

Levels of Organization Organism Organ System Organ Tissue Cell Organelle Molecule – Atom… Each level depends on many cooperating structures at the levels below

Nervous System Quick control over all body functions Electrochemical signals

Nervous Organs Brain 100 billion neurons forming connections

Nervous Organs Spinal cord Bundled neuron pathway Protected by meninges and vertebrae

Nervous Organs Spinal cord con’t…. Structure White matter: axons w/ sheath Gray matter: dendrites, cell bodies, neuroglials Central canal

Nerve Tissue Made of connected neurons and neuroglial cells Control over responses Transmit electrical and chemical signals

Nerve Cell – The Neuron Dendrites receive info Cell body, with trigger zone at end Axon sends impulses

Nerve Cell – The Neuron Axon sends impulses Myelin sheath, made of Schwann cells, wraps around axons and speeds up signals

Electrochemical Nerve Signal Reversal of charge (– to + to –) Travels down axon

Electrochemical Nerve Signal Controlled by ion flow Sodium+ pumped in Potassium+ pumped out

Electrochemical Nerve Signal Neurotransmitters cross synapse Acetylcholine Serotonin Norepinephrine Dopamine GABA Received by receptors

WRAP UP Which part of a neuron is most important, and why?

WARM UP Explain why nerve signals are described as “electrochemical.”

WRAP UP List the 3 parts of a neuron and describe the function of each.