The Nervous System
CNS/PNS
The Central Nervous System
Brain and spinal cord
Nervous System
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Receives sensory input from the environment
Processes the data
Responds to the info
2 basic parts
– CNS
– PNS
Central Nervous System (CNS)
• Major organs—brain and spinal cord
• The Brain—
– Incredible complexity—NOT by chance!
– 3% of body weight, uses 20% of total blood supply
– 4-8 mins w/o oxygen/glucose is fatal
• Major danger—stroke = loss of blood supply
– Ischemic—due to blood clot
– Hemorrhagic—usually to burst blood vessel
• 2 basic types
– Gray matter—typically the outer regions
• --contains numerous cell bodies and relatively few myelinated axons
• --involved in muscle control, and sensory perception such as seeing and
hearing, memory, emotions, speech, decision making, and self-control
– White matter—white b/c its covered w/ fatty tissue
• tissue through which messages pass between different areas of gray matter
within the central nervous system
Brain sections
Cerebral Lobes--Frontal, temporal, parietal, occipital—general processing
Cerebellum—coordinated muscle control
Brain stem—autonomic functions
Central Nervous System (CNS)
• The Brain lobes—
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Occipital lobe—visual cortex
Temporal lobe—primary auditory region
Frontal lobe—taste region
Parietal lobe—much of thought function
Wernicke’s and Broca’s areas have to do with speech
• Decussation—crossing over between brain halves
• Corpus callosum—largest commissure, allowing
communication between brain halves
• Limbic system—influences mood, emotion, fear and
sense fo pain/pleasure [desire for food, water and
pleasurable experience]
Brain protection--Meninges
Dura mater—tough membrane
Arachnoid mater—spider-like hollow spaces filled with lubricating fluid
Pia mater—softer membrane that adheres tightly to the brain surface
Cerebrospinal fluid (CSF)—cushions the brain
Spinal cord
Central grey matter, outer white matter
Cervical (upper limb nerves) and Lumbar (lower limbs) enlargements
“Horns”, so named because of appearance
Function of the reflex arc…
Central Nervous System (CNS)
• Pathways—
– Motor neurons–descending—carry signals away from
brain “down” to the body
– Sensory neurons-ascending—return signals “up” to
the brain
PERIPHERAL NERVOUS SYSTEM
(PNS)
Peripheral Nervous System
Spinal nerves, appendegeal nerves
Somatic motor nervous system—(SMNS)—controls skeletal muscle
Autonomic nervous system—(ANS)—controls smooth muscle tissue, cardiac
muscle and glandular tissue
Somatic motor nervous system
Somatic motor nervous system—(SMNS)—controls skeletal muscle
Autonomic Nervous System
Sympathetic—rouses your body to action
Parasympathetic—brings everything back to normal
Monitored and controlled by autonomic reflexes
Peripheral Nervous System (PNS)
• Afferent Division—
– Returns action potentials from sensory receptors
– Locational sensors• Somatic-in skin, muscle and tendons
• Visceral-in internal organs
• Specials-specific locations: taste, smell, hearing, sight
– Type of sensors
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Mechanoreceptors-respond to movement, touch, vibration or pressure
Thermoreceptors-heat or cold
Chemoreceptors-chemical substances
Photoreceptors-light
Nociceptors-excess stimulation, termed pain
– Simple or Complex
• Simple-widely distributed
• Complex-relaetd to the five senses
– Complex-relatd to the five senses
– Wernicke’s and Broca’s areas have to do with speech
• Corpus callosum—largest commissure, allowing communication between
brain halves
The Five Senses Plus…
SIMPLE AND COMPLEX SENSORY
RECEPTORS
Peripheral Nervous System (PNS)
• Afferent Division—
– Returns action potentials from sensory receptors
– Locational sensors• Somatic-in skin, muscle and tendons
• Visceral-in internal organs
• Specials-specific locations: taste, smell, hearing, sight
– Type of sensors
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Mechanoreceptors-respond to movement, touch, vibration or pressure
Thermoreceptors-heat or cold
Chemoreceptors-chemical substances
Photoreceptors-light
Nociceptors-excess stimulation, termed pain
– Simple or Complex
• Simple-widely distributed, relatively non-specific
• Complex-related to the five senses, very specific and minutely designed