Thursday, October 13, 2016

ch. 7 | the nervous system

nervous system functions:
-info input
-info processing
-info output 
  • central nervous system (CNS): composed of brain & spinal cord
-processes info/sensory data
-makes decisions/initiates response 
  • meninges: 3 membranes covering the brain & spinal cord (superficial--> deep)
  1. dura mater
  2. arachnoid mater
  3. pia mater 
  • 4 ventricles:
  1. left lateral
  2. right lateral
  3. third
  4. fourth




spinal cord:
-gray matter is divided into horns: 
anterior horns: motor neurons  
posterior horns: sensory neurons
lateral horns: autonomic neurons 
-white matter: external part of spinal cord, myelinated axons of sensory/motor neurons
-nerve roots: connect spinal cord to PNS
ventral root: efferent, descending tracts, motor info
dorsal root: afferent, ascending tract, sensory info
-spinal nerve: where ventral & dorsal roots combine

-spinal cord does not extend through entire length of vertebrae
-thickest in cervical & lumbar regions (enlargements), thinnest at thorax

cranial nerves:
  • cerebrospinal fluid (CSF): fluid found in the brain & spine; produced in choroid plexuses of ventricles of brain; acts as a cushioning 
  • peripheral nervous system (PNS): consists of nervous tissue structures that lie outside the brain & spinal cord
-senses changes in environment
-sends info to CNS
-receives info from CNS

sensory (afferent) nervous system:
-somatosensory receptors
-special sense receptors
-autonomic sensory receptors 

motor (efferent) nervous system:
  • somatic nervous system: voluntary, controls skeletal muscles, 1 motor neuron
  • autonomic nervous system: involuntary, controls smooth/cardiac/glands, 2 motor neurons
        o sympathetic: fight or flight
-uses ACh as preganglionic neurotransmitter 
-epinephrine or norepinephrine as postganglionic neurotransmitter
-increases heart rate/blood pressure --> delivers oxygen & nutrients to working muscles
-increases rate of breathing --> bring more oxygen into body
-breaks down glycogen & releases glucose --> energy for working muscles
-inhibits digestion --> keeps blood from being diverted from muscles

        o parasympathetic: rest & repair/rest & digest
-uses ACh as pre/postganglionic neurotransmitter
-stimulation of digestive tract --> increased digestion
-vasoconstriction decreases blood flow --> shunts it toward digestive tract
-relaxes bladder & anal muscles --> increased urination & defecation

neurons:
-interneurons: extend for short distances, btwn afferent & efferent, found in gray matter
-ganglion: collection of nerve cell bodies found in PNS
  • synapse: junction btwn 2 neurons 
  • neurotransmitter: released into synaptic cleft in response to nerve impulse 
plexus: network of neurons formed from emerging branching spinal nerves from spinal cord
  • cervical: distributes to diaphragm
  • brachial: distributes to muscles of arm
  • lumbar: distributes to femur/knee
  • sacral: distributes to gluteus muscles, sciatic (runs down leg)

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