Chapter 11Nervous System II
Meninges•
• protect CNS• three layers
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•
•
11-2
Meninges of the Spinal Cord
11-3
Cerebrospinal Fluid
• circulates in ventricles, central canal of spinal cord, and subarachnoid space• completely surrounds brain and spinal cord• clear liquid• nutritive and protective• helps maintain stable ion concentrations in CNS
11-5
Spinal Cord Structure
• extends foramen magnum to 2nd lumbar vertebra
11-6
Cross Section of Spinal Cord
11-7
Spinal Cord Functions
• center for spinal reflexes
• conduit for nerve impulses to and from the brain
11-8
Reflex Arcs
Reflexes –
11-9Reflex Ark.mov
Knee-jerk Reflex
•
11-10
Withdrawal Reflex• protective
11-11
Crossed-Extensor Reflex
• flexor muscles contract• flexor muscles on opposite side inhibited• extensor muscles on opposite side contract for balance
11-12
Tracts of the Spinal Cord
• Ascending • Descending
11-13
Brain
Functions• • determines perception• stores memory• • makes decisions• • regulates visceral activities• determines personality
Major Parts• cerebrum
• two cerebellar hemispheres• diencephalon• brain stem• cerebellum
11-16
Brain Development
Three Major Vesicles1. Forebrain2. Midbrain3. Hindbrain
11-17
Structure of Cerebrum
• corpus callosum•
• convolutions • bumps or gyri
• sulci•
• longitudinal fissure• separates hemispheres
• transverse fissure• separates cerebrum from cerebellum
11-19
Lobes of Cerebrum
• Frontal• Parietal• Temporal• Occipital• Insula
11-20
Functions of Cerebrum
• interpretation• initiating voluntary movements• storing memory• retrieving memory• reasoning• center for intelligence and personality
11-21
Functional Regions of Cerebral Cortex
Cerebral Cortex –
11-22
Motor Areas
• Primary Motor Areas• frontal lobes• control voluntary muscles
• Broca’s Area• anterior to primary motor cortex• usually in one hemisphere• controls muscles needed for speech
• Frontal Eye Field• above Broca’s area• controls voluntary movements of eyes and eyelids 11-23
Motor Areas
11-24
Sensory Areas
• Cutaneous Sensory Area
• parietal lobe• interprets sensations on skin
• Visual Area• occipital lobe• interprets vision
• Auditory Area• temporal lobe• interprets hearing
11-25
Sensory Areas
11-26
Association Areas
Frontal Lobe Association Areas• concentrating• planning• problem solving• judging
Parietal Lobe Association Areas• understanding speech• using words to express thought
Temporal Lobe Association Areas• remember visual scenes• remember music• remember complex patterns
Occipital Lobe Association Areas• combine visual images with other sensory experiences
11-28
Hemisphere Dominance
•
• Dominant hemisphere controls
• speech• writing• reading• verbal skills• analytical skills• computational skills
• Nondominant hemisphere controls
• nonverbal tasks• motor tasks• understanding and interpreting musical and visual patterns• provides emotional and intuitive thought processes
11-29
Memory
Short Term• working memory• closed circuit• circuit is stimulated over and over• when impulse flow stops, memory disappears
Long Term• changes structure and function of neurons• enhanced synaptic transmission
11-30
Limbic System
Consists of• portions of frontal lobe• portions of temporal lobe• hypothalamus• thalamus• basal nuclei• other deep nuclei
Functions• controls emotions• produces feelings• interpret sensory impulses
11-34
Brain Stem
Three Parts1. Midbrain2. Pons3. Medulla Oblongata
11-35
Types of Sleep
Slow Wave• person is tired• decreasing activity of reticular system• restful• dreamless• reduced blood pressure and respiratory rate• ranges from light to heavy• alternates with REM sleep
Rapid Eye Movement (REM)• some areas of brain active• heart and respiratory rates irregular• dreaming occurs
11-40
Peripheral Nervous System
• Cranial nerves • Somatic fibers connecting to the skin and skeletal muscles• Autonomic fibers connecting to viscera
• Spinal nerves • Somatic fibers connecting to the skin and skeletal muscles• Autonomic fibers connecting to viscera
11-42
Nerve Fiber Classification
• Sensory Nerves – • Motor Nerves – • Mixed Nerves – contain both sensory nerve fibers and motor nerve fibers; most nerves
11-44
Cranial Nerves
11-46
Spinal Nerves
• mixed nerves• 31 pairs
• 8 cervical (C1 to C8)• 12 thoracic (T1 to T12)• 5 lumbar (L1 to L5)• 5 sacral (S1 to S5)• 1 coccygeal (Co)
11-54
Dermatome
• an area of skin that the sensory nerve fibers of a particular spinal nerve innervate
11-56
Autonomic Nervous System
11-60
• functions without conscious effort• controls visceral activities• regulates smooth muscle, cardiac muscle, and glands• efferent fibers typically lead to ganglia outside CNS
Two Divisions• sympathetic – prepares body for fight or flight situations• parasympathetic – prepares body for resting and digesting activities
Sympathetic Division
11-64
Parasympathetic Division
11-66
Life-Span Changes
11-71
• Brain cells begin to die before birth• Over average lifetime, brain shrinks 10%• Most cell death occurs in temporal lobes• By age 90, frontal lobe has lost half its neurons• Number of dendritic branches decreases• Decreased levels of neurotransmitters• Fading memory• Slowed responses and reflexes• Changes increase risk of falling• Sleep problems common
Clinical Application
11-72
Cerebral Injuries and Abnormalities
Concussion• brain jarred against cranium• loss of consciousness• temporary loss of memory• mental cloudiness• headache• recovery usually complete
Cerebral Palsy• motor impairment at birth• caused by blocked cerebral blood vessels during development• seizues• learning disabilities
Cerebrovascular Accident• stroke• sudden interruption in blood flow• brain tissues die