The Nervous System The Nervous System Introducion Introducion
Overview• Functions• Organization• Protection
Functions• Monitor activities of body parts -
sensory neurons
• Communicate between body parts - associative neurons
• Command necessary action - motor neurons
Functions• The nervous system is a fast acting
control center; it gathers, integrates, stores and recalls information, and acts upon that information to ensure survival.
Organization: Divisions of the Nervous System
• Central Nervous System (CNS)-brain-spinal cord
Organization: Divisions of the Nervous System
• Peripheral Nervous System (PNS)-cranial nerves-spinal nerves
• Has two subdivisions: somatic & autonomic
Organization: Divisions of the Nervous System - PNS• Somatic nervous system - voluntary,
contains sensory & motor neurons; stimulates skeletal muscle
Organization: Divisions of the Nervous System - PNS• Autonomic nervous system -
involuntary; controls action of cardiac and smooth muscle as well as glands
• Two subdivisions: sympathetic & parasympathetic
Organization: Divisions of the Nervous System - PNS
• Sympathetic system = “fight or flight” response activated during times of stress = increased heart rate, blood pressure, etc.
• Also referred to as the “E” system for exercise, excitement, emergency, & embarrassment
Organization: Divisions of the Nervous System - PNS
• Parasympathetic system = “housekeeping” in effect most of the time; maintains homeostasis
• Also referred to as the “D” system for digestion, defecation, and diuresis (urination)
Protection of the Nervous System
• Bones - skull protects brain; vertebrae protect spinal cord
• Cerebrospinal Fluid (CSF) - watery fluid formed from plasma that circulates through the central nervous system and function as a shock absorber
Protection of the Nervous System
• Blood-Brain Barrier - made of the least permeable capillaries in the body, keeps neurons separated from many substances in the body to help prevent uncontrolled neural activity
Protection of the Nervous System
• Blood-Brain Barrier - keeps out metabolic wastes such as urea, toxins, proteins, and most drugs -also keeps out nonessential amino
acids and potassium -does allow essential amino acid, water
and glucose
Protection of the Nervous System
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Protection of the Nervous System
• Meninges - 3 layered connective tissue membranes that cover & protect the brain and spinal cord
• Layers in order of outermost to innermost: Dura mater, Arachnoid membrane, and Pia mater
Meninges• Dura mater = “tough mother”, leathery
and made up of two layers that forms the outer covering of the brain as well as the periosteum of the skull
Meninges• Arachnoid membrane - middle layer with threadlike extensions giving a cobweb like appearance. Has subarachnoid filled with CSF
Meninges• Pia mater = “gentle mother”, innermost layer, delicate and highly vascularized (rich blood supply)
The End!