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The Levels of Control
- High Levels: Forebrain (integration of sensory and motor control; thought, memory, learning).
- Lower Levels: Brainstem (vegetative functions).
- Lowest Levels: Spinal Cord (reflexes).
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Divisions and Subdivisions of the Nervous System
- 1. Central Nervous System (CNS)
- *Brain and Spinal Cord
- 2. Peripheral Nervous System (PNS)
- *Somatic Nervous System: Voluntary; Skeletal Muscle
- *Autonomic Nervous System: Involuntary; Cardiac & Smooth Muscles, Glands
- −Sympathetic: Stress Functions
- −Parasympathic: Vegetative Functions
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Neuralgia
- Nerve Cell
- Support and Protection of neurons
- 50% are brain cells
- 90% make up all nervous system
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Neurons
- Nerve Cell
- Conduct nerve impulses.
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White Matter
- General Term of NS
- An aggregation of myelinated axons from many neurons supported by neuralgia.
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Gray Matter
- General Term of NS
- Can either be nerve cell bodies and dendrites or bundles of unmyelinated axons and neuralgia.
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Nerve
- General Term of NS
- Most Myelinated
- Bundle of nerve fibers found in the Peripheral Nervous System (PNS).
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Tract
- General Term of NS
- All Myelinated
- Bundle of nerve fibers found up and down the spinal cord and between the segments in the brain.
- Central Nervous System (CNS).
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Ganglion
- General Term of NS
- Group of nerve cell bodies found in the Peripheral Nervous System (PNS).
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Nucleus
- General Term of NS
- Group of nerve cell bodies found in the Central Nervous System (CNS).
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Brain Stem
- A major division of the brain between the spinal cord and diencephalon.
- Consists of the Medulla Oblongata, Pons, and Midbrain.
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Diencephalon
- A major division of the brain.
- Includes the Thalamus and Hypothalamus.
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Cerebrum
- A major division of the brain.
- Two Parts: Cerebral Cortex and Basal Ganglia
- Cerebral Cortex has 6 outer layers of brain cells.
- Basal Ganglia is the inner gray matter of the cerebrum and coordinates slow, maintained muscle movement.
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Cerebral Cortex
- Part of the Cerebrum.
- Comprises the 6 outer layers of the brain.
- Interprets incoming sensory information as well as execution of motor responses.
- Higher level integrative functions which govern the emotional and intellectual processes (will, reasoning, personality, intelligence, judgement, consciousness).
- Sensory Areas: Interpret sensations to form perceptions.
- Motor Areas: Control muscular movement.
- Association Areas: process the incoming sensory information in order to execute the appropriate motor response.
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Cerebellum
- A major division of the brain.
- Consists of two cerebral hemispheres.
- Controls subconscious skeletal muscle contraction required for balance and posture.
- Coordination and planning of skilled voluntary muscle activity.
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Meninges
- CNS, Protection of the Brain
- 3 connective tissues that lie external to the CNS organs.
- Dura Mater: "Tough Mother", tough outer layer
- Arachnoid: "Spider-like", middle layer
- Pia Mater: "Delicate Mother", innermost layer adjacent to the brain
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Cerebrospinal Fluid
- CNS, Protection of the Brain
- Clear fluid (i.e. blood plasma) formed in the choroid plexuses (networks of capillaries found in ventricles).
- CSF formation = CSF absorption (80-150 mls are replaced every 3-4 hrs)
- Shock absorber
- Circulation, delivers some nutrients/removes some wastes to some tissues of the CNS.
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Ventricle
Channels througout the brain through which cerebralspinal fluid pass through.
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Blood-Brain Barrier (BBB)
- Decribes the "differential rates of movement" of substances into the brain due to the special structure of the brain capillaries.
- The brain capillaries along with their associated connective tissue contain very tight junctions permitting only limited movement on certain substances.
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Medulla
- Part of the Brain Stem
- Relays motor and sensory impulses between the brain and spinal cord.
- Reflex centers regulate heartbeat, breathing, and blood vessel diameter.
- Part of R.A.S. functioning in consciousness and arousal.
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Pons
- Part of the Brain Stem
- Relays impulses within the brain and between parts of the brain and spinal cord.
- Pneumotaxic area and apneustic area help coordinate breathing.
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Midbrain
- Part of the Brain Stem
- Relays motor impulses from the cerebral cortex to the pons and spinal cord.
- relays sensory impulses for the spinal cord to the thalamus.
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Thalamus
- Part of the Diecephalon
- Relay station for all sensory impulses to the cerebral cortex.
- Relays motor impulses from cerebral cortex to the spinal cord.
- Portions function in emotion and memory.
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Hypothalamus
- Part of the Diecephalon
- Helps control and integrate ANS.
- Recieves sensory impulses from viscera.
- Regulates and controls many endocrine functions.
- Controls the feelings of rage and aggression.
- Controls body temp., and the intake/outtake of both food and fluid.
- Helps maintain waking state (part of the R.A.S.)
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Limbic System
- Includes: Cerebral Cortex, Basal Ganglia, Thalamus, and Hypothalamus.
- Controls emotional aspects of behavior related to survival such as aggression, feeding, motivation, fear sex, reward/punishment.
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Reticular Formation (R.A.S.)
- Interconnected neurons that run throughout the entire brain stem and into the thalamus.
- Receives and integrates all synaptic input.
- Part of the reticular formation called the reticular activating system (R.A.S.) which carries signals upward to arouse and activate the cerebral cortex.
- R.A.S. controls the overall degree of cortical alertness and is important in the ability to direct attention toward specific events.
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Spinal Cord
- Divided into ascending and descending pathways (tracts).
- Ascending Tracts: Convey sensory info from various receptors (cutaneous and visceral receptors, proprioceptors) to the opposite side of the brain.
- Descending Tracts: Convey motor impulses from different parts of the brain to the spinal cord.
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Reflex
A quick response to a specific stimulus for the maintenance of homeostasis.
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Reflex Arc
- Receptor -> Sensory Neurons -> CNS -> Motor Neurons -> Effectors
- Reflexes may be classified according to the processing site, the tissue responding, and the complexity of the circuitry.
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