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Chapter 9

PHSI 208 Chapter 9: PHSI 208.6 Chapter 9 Notes (VC14)


Department
Physiology
Course Code
PHSI 208
Professor
Baillie Landon
Chapter
9

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PHSI 208.6 – University of Saskatchewan
Prof. Veronica Campanucci
Chapter 9: The Central Nervous System
Lecture 14
Organization of the Nervous System
Central nervous system (CNS): brain, spinal cord.
Peripheral nervous system (PNS): nerve tissue outside outside the CNS. Crainial nerves and
branches, spinal nerves and branches, ganglia, plexuses and sensory receptors.
Subdivisions:
Somatic: muscle, skin, sense organs.
Autonomic: sympathetic and parasympathetic.
Enteric: gastrointestinal system.
Spinal Cord
Contains nuclei with cell bodies of efferent neurons and tracts of axons going to and from the
brain. The spinal cord and vertebrae come in segments.
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PHSI 208.6 – University of Saskatchewan
Prof. Veronica Campanucci
The spinal cord is the major pathway for information flowing back and forth between the brain
and the skin, joints and muscle. It is split into four sections: cervical, thoracic, lumbar and
sacral. It is subdivided into spinal segments. Each segment has the following structure:
White matter: myelinated axons. Consists of tracts of axons that carry information to and from
the brain.
White matter
Ascending tracts carry sensory information to the brain (axons going up).
Descending tracts carry commands to the motor neurons (axons going down).
Gray matter: cell body & myelinated axons
Each segment is organized in layers, and different layers receive different types of information.
The spinal cord is the connection between the peripheral nervous system and the brain. Most
somatic senses (except smell) go through the spinal cord to the brain.
Spinal Reflexes
Sensory information entering the spinal cord is acted on without input from the brain.
However, sensory information about the stimulus may be sent to the brain.
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PHSI 208.6 – University of Saskatchewan
Prof. Veronica Campanucci
Reflex-arc example:
1) Stimulus arrives and activates receptor.
2) This activates a sensory neuron. Sensation is relayed to the brain by collateral.
3) Information is processed in the CNS. This is when you become aware of the stimulus.
4) Motor neuron is activated.
5) Response by the effector.
*This process happens very fast, and without the brain.
Anatomy of the Brain
Cerebrum Components: cerebral cortex, basal ganglia, amygdala, hippocampus.
Cerebral cortex fxns: Contains sensory areas for perception, and motor areas for
skeletal muscle movement. Association areas are involved in the integration of information and
direction of voluntary movement.
Basal ganglia fxns: Movement.
Amygdala fxns: Emotion, memory.
Hippocampus fxns: Learning, memory.
Cerebellum:
Cerebellum fxns: Movement coordination.
**See following page for diagram.
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