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BIO 132

BIO 132. Lecture 2 Neurons. Neurophysiology. Lecture Goals:. Understanding the basic function of the nervous system. Understanding the parts of a neuron.

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BIO 132

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  1. BIO 132 Lecture 2 Neurons Neurophysiology

  2. Lecture Goals: • Understanding the basic function of the nervous system. • Understanding the parts of a neuron.

  3. Neuron – A specialized cell of the body that can communicate information quickly by using ionic currents and chemical signals called neurotransmitters. • Nerve - Many neurons that are bundled together and covered by a connective tissue sheath. • Nervous System – The entire network of interconnecting neurons.

  4. Overall function of the nervous system: To control motor output of the body based on sensory information it detects from both the internal and external environments of the body.

  5. There are ~100 billion neurons in the brain. (Current population is less than 7 billion people.) • Each neuron can make one to thousands of connections with other neurons. • Glial cells are support cells of the nervous system • There are ~10 times as many glial cells as there are neurons. • Used to nourish, insulate, direct growth of neurons.

  6. Neuron Morphology • Parts of a typical neuron: Dendrites Cell body Axon terminal Axon

  7. Cell Body (soma) • Contains most of the cellular machinery of the neuron (nucleus, ER, mitochondria, golgi complex, etc). • Is where most the synthesis of new cellular products occurs. Cell body

  8. Dendrites • Means “tree” in Latin. • Main site where input is received from other neurons. Dendrites

  9. Axon • Long projection from cell body that carries an ionic signal, called an action potential, to other neurons. • Can be very short or very long (up to 6 feet in humans). • Can send off many branches (collaterals). Axon

  10. Axon Terminal • Is at the end of each axon. • Contains vesicles filled with neurotransmitter. • Forms a connection with another neuron, called a synapse. Axon terminal

  11. Classifying Neurons • There are several conventions for classifying neurons: • By neurites (projections from the cell body). • By dendrite shape. • By connections. • By neurotransmitter released

  12. Classification By Neurites • Unipolar neuron - A single neurite (projection from cell body: • Bipolar – Two neurites (both part of the axon) • Multipolar – Many neurites (usually one axon and many denrites)

  13. Classification By Connections • Primary sensory – dendrites detect external stimuli. • Motor - makes a direct connection with skeletal muscle. • Interneuron - only makes connections with other neurons. (Most numerous type) Stimuli

  14. Classification By Neurotransmitter • Based on the type of neurotransmitter released. • Examples: • Cholinergic • Noradrenergic • GABAergic • Glutamatergic • Dopaminergic Acetylcholine (ACh) Norepinephrine (NE) GABA Glutamate (Glu) Dopamine (DA)

  15. Classifying Glia • Astrocytes • Most numerous • Fill the space between neurons • Envelope synapses to limit the spread of neurotransmitters • Regulate chemical content of extracellular fluid • Remove neurotransmitters from synapse • Myelinating glia – insulate axons from ion leakage • Oligodentrites • Found in Central NS and spinal cord • Can wrap around several axons • Schwann cells • Found in peripheral NS • Wrap around a single axon

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