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Chapter 29

BIOL 1001 Chapter Notes - Chapter 29: Motor Neuron Disease, Neurotransmitter, Neuroglia

5 pages89 viewsSpring 2013

Department
Biology
Course Code
BIOL 1001
Professor
Smutzer
Chapter
29

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Chapter 29 Neural Control
Neurons
The basic units of communication in nearly all nervous systems
Monitor info in and around body, issue commands for responsive actions
They are excitable cells – undergo a change in charge across the plasma membrane
3 Classes:
1. Sensory Neurons : converting external stimuli from the environment into internal
stimuli
2. Interneurons (relay neurons) : connects afferent neurons and efferent neurons in
neural pathways
3. Motor Neurons : project their axons outside the CNS and directly or indirectly control
muscles
*Lou Gehrigs Disease (ALS) is a motor neuron disease
Two Types:
1. Afferent Neurons : carry nerve impulses from receptors or sense organs to the central
nervous system
2. Efferent Neurons : motor or effector neurons, carry nerve impulses away from the central
nervous system to muscles or glands
Neuroglia (Glial Cells)
Make up more than half the volume of the vertebrate nervous system, half of brain
tissue
A variety of cells that metabolically assist, structurally support, and protect the
neurons
Cancers of the brain usually involve glial cells
Examples of glial cells
1. Astrocytes:
- Largest and most numerous of the glial cells in the brain and spinal cord
- Contribute to the blood-brain barrier,
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- Regulate the chemical environment around cells, release regulatory
sustances that influence nerve cells
- Maintenance of extracellular ion balance
- Respond to injury, have a role in the repair and scarring process of the
brain and spinal cord
- Provide nutrients
2. Microglia:
- Macrophages derived from bone marrow
- Scavengers, engulfing dead cells and other debris
- - In Alzheimer’s, they are found associated with dying nerve cells and
B-amyloid plaques
3. Oligodendrocytes:
- Wrap axons with myelin sheaths in CNS which improves the speed
and reliability of impulse conduction
- Main function is the myelination of axons exclusively to the central
nervous system, help insulate neurons
- Produce substances that inhibit the regeneration of axons in the adult
CNS
Synapse
The junction across which a nerve impulse passes from an axon terminal to the dendrite
of a second neuron, to a muscle cell, or to a gland cell
When a neuron is excited, calcium is released from small vesicles at the axon terminal,
and then neurotransmitters are released from vesicles into the synapse
Neurotransmitter release occurs by exocytosis
Acetylcholine and dopamine are neurotransmitters in the CNS
Resting Potential (of a neuron)
Charge difference across the plasma membrane of a neuron
Fluid just outside cell is more positive charged than fluid inside
Resting potential of plasma membrane of a neuron is -70 millivolts
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