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 sections Cerebral Lobes--Frontal, temporal, parietal, occipital—general processing Cerebellum—coordinated muscle control Brain 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--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 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