Chapter_12_Nervous_Tissue - Chapter 12 Nervous Tissue Pages...

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Chapter 12 Nervous Tissue Pages 404 – 434 1. Overview Of The Nervous System—weighs about 2 kg and about 3% of total body weight A. Structures of the Nervous System: CNS & PNS: Fig 12.1 CNS--brain and spinal cord Brain—highly organized structure 100 billion neurons and ten times more neuroglia cells Spinal Cord—connected to the brain through the foramen magnum of the skull and is encircled by the bones of the vertebral column; contains a 100 million neurons. PNS: Cranial Nerves—has 100 million neurons and have 5 to 50 times more neuroglia; 12 pairs of cranial nerve emerging from the base of the neck Cell body receded normally in CNS (because they are protected) and axons go out: Nerve- bundle of axons carry message away from cell body; has connective tissue, blood vessels; and lay outside the CNS ; a bundle of hundreds to thousands or axons plus associated connective tissue and blood vessels that lie outside the brain and spinal cord.; contains a well defined path and serves a specific region of the body Spinal Nerves—31 pairs of spinal nerves and emerge from the spinal cord Ganglia—small masses of nervous tissue, consisting primarily of neuron cell bodies; cell body that lies outside CNS; closely associated with cranial and spinal nerves Sensory Receptors—detect internal and external stimulus and use wither the sensory or afferent neurons to carry information into the brain and spinal cord through cranial and spinal nerves; job to bring info to the CNS; could be free or close dendrite or special cell; ex photoreceptors in the eye Enteric Plexuses—100 million neurons that are located in the gut and control the digestive tract many of them work independently of PNS and CNS B. Functions of the Nervous System Sensory—carry info to the CNS; sensory neurons or afferent neurons; could have internal or external stimuli such as change in acidity of blood or touching a hot surface (external) Integrative Function—integrates (processes) sensory info by analyzing and storing some of it and by making decisions for appropriate responses; rejects 90% of sensory information; neurons that play role in it are interneuron; perception is when conscious awareness of stimuli. Motor—once sensory info is integrated, the nervous system may elicit an appropriate motor response such as muscle contraction or gland secretion which the motor or efferent neuron function; such as writing down; tells the muscle and bones to move; motor neurons or efferent neurons; send info from brain to spinal cord or spinal cord to the effectors through the spinal and cranial nerves; connects rest of body to CNS 1
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C. Organization of the Nervous System: Fig 12.2 SNS—somatic nervous system; carries info from the rest of the body and from special sensory and receptors and sends to the CNS and conducts impulses from the CNS to skeletal muscles only ; external receptors; action is voluntary ANS-autonomic system—carries info from autonomic sensory receptors to the CNS;
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This note was uploaded on 04/11/2011 for the course BIO 301 taught by Professor Rupade during the Winter '09 term at Purdue.

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Chapter_12_Nervous_Tissue - Chapter 12 Nervous Tissue Pages...

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