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Chapter 13. The Spinal Cord, Spinal Nerves, and Spinal Reflexes. Organization:. President. VP (dean). division heads. department chair. faculty. brain. more processing centers. processing centers. senses. muscles. fig. 13-1. Chapter 12 neurons Chapter 13 spinal cord reflexes
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Chapter 13 The Spinal Cord, Spinal Nerves, and Spinal Reflexes
Organization: President VP (dean) division heads department chair faculty
brain more processing centers processing centers senses muscles
Chapter 12 neurons Chapter 13 spinal cord reflexes Chapter 14 brain and cranial nerves Chapter 15 brain-spinal cord interaction Chapter 16 autonomic NS
Spinal cord anatomy ~ 18 inches (not as long as vertebral column) ends about L1 or L2 (conus medullaris) deep groove on anterior (ventral) side roots attached to it (dorsal and ventral)
cervical thoracic lumbar fig. 13-2
white matter posterior white columns lateral white columns anterior white columns fig. 13-5
ascending tracts sensory descending tracts (motor) posterior white columns lateral white columns anterior white columns fig. 13-5
epineurium perineurium endoneurium fig. 13-6
Charlie epaxial hypaxial e axis h
distribution of spinal nerves dorsal and ventral dermatomes
Clinically significant: damage to spinal nerve or DRG may cause sensory loss to just a restricted part of the skin… …by mapping the deficit you may be able to pinpoint where the nerve has been damaged
Clinically significant: example: shingles virus attacks DRG painful rash area of dermatome of that spinal nerve
spinal cord Distribution of spinal nerves T1 to T12 is “typical”
cervical plexus C 3 , 4 and 5 keep the diaphragm alive fig. 13-10
lumbar plexus sacral plexus S 2 , 3 and 4 keep your anus off the floor
The human body contains: 10,000,000 sensory neurons 500,000 motor neurons 20,000,000,000 interneurons information to CNS control effectors (muscles) interpret, plan, coordinate incoming and outgoing info
all these neurons are organized into neuronal pools - functional groups of interconnected neurons 100’s to 1000’s ??
neuronal polls 100’s to 1000’s ?? each has limited input/output can be excitatory or inhibitory contain different circuit patterns
one neuron (neuronal pool) Divergence multiple neurons (neuronal pools) fig. 13-13a (vision)
many neurons Convergence single neuron fig. 13-13b (muscle control, breathing)
Serial Processing stepwise spread of info (pain) fig. 13-13c
Parallel Processing several neurons (pools) access same info divergence serial fig. 13-13d (ouch)
Reverberation positive feedback loop fig. 13-13e
conditions in or around the body can change suddenly and unexpectedly… reflex rapid, automatic response to specific stimulus make adjustments to maintain homeostasis
Homeostatic regulation: autoregulation extrinsic regulation adjustment within organ… nervous/endocrine system
Homeostatic regulation: • Three part mechanism: • receptor (stimulus) • control center • effector
wiring of a reflex is called… reflex arc
reflex arc step 1 arrival of stimulus activation of receptor
reflex arc step 2 activation of sensory neuron
reflex arc step 3 information processing
reflex arc step 4 activation of motorneuron
reflex arc step 5 response of effector
Classification of reflexes developmental origin nature of motor response complexity site of information processing
Classification of reflexes developmental origin innate acquired nursing driving
Classification of reflexes nature of motor response somatic visceral skeletal muscle later (#16)
Classification of reflexes complexity monosynaptic polysynaptic quicker slower
Classification of reflexes site of processing site spinal cord brain spinal reflexes cranial reflexes (later)
Monosynaptic reflexes very little delay rapid responses example: stretch reflex automatic regulation of length of skeletal muscle