Nervous-System - Communication Center Nervous System...

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2/16/2012 1 Communication Center Regulation Neural vs. Hormonal Nervous System •The Neural System is only 3% of your body weight, but is the most complex organ system. •Nervous impulses are fast acting (milliseconds) but short lived. Overview •The nervous system includes all neural tissue in the body. Basic units are: a. Neurons (individual nerve cells) b. Neuroglia supporting cells separate & protect the neurons provide supporting framework act as phagocytes regulate composition of interstitial fluid a.k.a. glial cells outnumber neurons Two Anatomical Divisions of The Nervous System 1.CNS : Central Nervous System Brain & Spinal Cord Responsible for integrating, processing, & coordinating sensory data and motor commands. i.e.- stumble example The brain is also the organ responsible for intelligence, memory, learning, & emotion
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2/16/2012 2 2. PNS : Peripheral Nervous System All nervous tissue outside CNS Carries sensory data to CNS, carries motor commands from the CNS. Bundles of nerve fibers carry impulses in the PNS k i h l j t PNS are known as peripheral nerves or just “nerves”. Nerves attached to the brain are called cranial nerves. Nerves attached to the spinal cord are called spinal nerves. PNS has 2 functional divisions Afferent Division (Sensory) •Bring sensory information to CNS from receptors in peripheral nervous tissue & organs. Efferent Division (Motor) •Carries motor commands from CNS to muscles & glands, these target organs are called effectors . The Efferent Division is broken into Somatic & Autonomic Components (SNS) Somatic System : controls skeletal muscle contractions these can be voluntary (conscious) or involuntary (unconscious) {reflexes}. (ANS) A t i S t (ANS) Autonomic System : * a.k.a. visceral motor units *control autonomic, involuntary regulation of smooth muscle, cardiac muscle, & glandular activity. The ANS has a: sympathetic division } antagonistic effects parasympathetic •The sympathetic (Fight or Flight) increases heart rate, parasympathetic decrease heart rate, etc.
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2/16/2012 3 Perikaryon: contains 1. numerous mitochondria 2. free & fixed ribosomes 3. membranes of rough ER (give perikaryon a grainy appearance) Some areas of perikaryon contain RER & free ribosome clusters which stain darkly. These are called Nissl Bodies. These give the tissue a grey color and are therefore present in “ gray matter ”. Typically, perikaryon lacks centrioles which are required for cell division, so the CNS is not generally repaired after an injury. Dendrites •Typically highly branched •Sensitive processes •Each branch has small processes of its own called dendrite spines •Specialized to receive nervous impulses •Impulse travel to soma Axon •Long cytoplasmic process • Can propogate an action potential •Impulses travel away from soma •The axon has it’s own axoplasm and membranous axolemma •The axonal trunk may have branches called collaterals
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