The Nervous System

CNS/PNS

The Central Nervous System

Brain and spinal cord

Nervous System

• 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 sectionsCerebral Lobes--Frontal, temporal, parietal, occipital—general processingCerebellum—coordinated muscle controlBrain stem—autonomic functions

Central Nervous System (CNS)• The Brain lobes—– 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--MeningesDura mater—tough membraneArachnoid mater—spider-like hollow spaces filled with lubricating fluidPia mater—softer membrane that adheres tightly to the brain surfaceCerebrospinal fluid (CSF)—cushions the brain

Spinal cordCentral grey matter, outer white matterCervical (upper limb nerves) and Lumbar (lower limbs) enlargements“Horns”, so named because of appearanceFunction 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 SystemSpinal nerves, appendegeal nervesSomatic motor nervous system—(SMNS)—controls skeletal muscleAutonomic nervous system—(ANS)—controls smooth muscle tissue, cardiac muscle and glandular tissue

Somatic motor nervous systemSomatic motor nervous system—(SMNS)—controls skeletal muscle

Autonomic Nervous SystemSympathetic—rouses your body to actionParasympathetic—brings everything back to normalMonitored 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• 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

SIMPLE AND COMPLEX SENSORY RECEPTORS

The Five Senses Plus…

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• 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