Central Nervous System Chapter 13 Lecture Notes

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Central Nervous SystemChapter 13 Lecture Notes

• to accompany
• Anatomy and Physiology From Science to Life
• textbook by
• Gail Jenkins, Christopher Kemnitz, Gerard Tortora

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Chapter Overview

• 13.1 Central Nervous System
• 13.2 Protection and Nourishment of the CNS
• 13.3 Cerebrum
• 13.4 Limbic System
• 13.5 Signal Processing in the Cerebrum
• 13.6 Diencephalon
• 13.7 Brain Stem
• 13.8 Cerebellum
• 13.9 Spinal Cord
• 13.10 Propagation of Impulses

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Essential Terms

• Central Nervous System (CNS)
• brain and spinal cord
• control center for
• thoughts
• emotions
• creativity
• wisdom
• memories
• activities
• behaviors
• Tract
• bundle of axons

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Introduction

• CNS made up of 100 billion neurons
• Adult brain mass of 1300g (3 lbs)
• Spinal cord
• mediates rapid reactions
• reflexes
• pathway for sensory nerve impulses to brain
• pathway for motor nerve impulses from brain

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Concept 13.1Central Nervous System
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CNS

• Brain
• cerebrum
• cerebral hemispheres
• diencephalon
• brain stem
• cerebellum
• Spinal Cord
• medulla oblongata to superior edge of L2
• Protection of CNS
• two types of connective tissues
• bony skull
• cranial and spinal meninges
• cushion of cerebrospinal fluid

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Figure 13.1a
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Figure 13.1c
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Figure 13.2
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Skeletal Protection

• Brain is located in cranial cavity of skull
• Spinal cord is located within vertebral canal of
  vertebral column
• vertebral foramina of vertebrae stacked one on
  top of one another form the vertebral canal

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Meninges

• three connective tissue coverings that encircle
  brain and spinal cord
• cranial meninges
• spinal meninges
• superficial to deep
• dura mater
• arachnoid mater
• pia mater

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Figure 13.3a
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Figure 13.4a
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Dura Mater of Brain

• most superficial adheres to periosteum of cranial
  bones
• strongest menix
• extensions separate portions of brain
• falx cerebri
• two hemispheres of cerebrum
• falx cerebelli
• two hemispheres of cerebellum
• tentorium cerebelli
• separates cerebrum from cerebellum

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Dura Mater of Spinal Cord

• between dura mater and all of vertebral canal
• epidural space
• cushion of fat
• dura mater tissue
• sinuses that act as collection points for
  interstitial fluid and blood leaving brain
• return interstitial fluid and blood to internal
  jugular veins of neck

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Arachnoid Mater

• avascular
• collagen fibers
• some elastic fibers
• surrounds both brain and spinal cord
• subdural space
• thin space between dura mater and arachnoid
  matter
• contains interstitial fluid

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Pia Mater

• innermost membrane
• tightly adheres to surface of CNS
• interlacing bundles of collagen fibers
• some fine elastic fibers
• surrounds both brain and spinal cord
• subarachnoid space
• thin space between arachnoid mater and pia matter
• contains cerebrospinal fluid
• also covers surface blood vessels of CNS

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Meninges and Spinal Nerves

• All three
• cover spinal nerves
• up to point of exit from spinal column
• through intervertebral foramina

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Denticulate Ligaments

• suspend spinal cord in middle of dural sheath
• membranous extensions of pia mater
• project laterally and fuse with
• arachnoid mater and
• inner surface of dura mater
• between anterior and posterior nerve roots of
  spinal nerves on either side
• protect spinal cord against shock and sudden
  displacement

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Concept 13.2 Nourishment and Protection
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Blood Flow to CNS

• to brain via
• internal carotid and vertebral arteries
• flows into dural sinuses
• empties into internal jugular veins
• to spinal cord via
• posterior intercostal and lumbar arteries
• empties into posterior intercostal and lumbar
  veins

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Figure 20.20c
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Figure 20.20d
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Blood Flow to Brain

• Brain at rest uses 20 of oxygen and glucose
• even though only 2 of mass of adult
• Neurons synthesize ATP almost exclusively from
  glucose
• when activity increases in a particular region,
  blood flow to that area also increases

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Blood Flow to Brain

• decreased blood flow to brain
• short time can cause unconsciousness
• 1 to 2 minutes impairs neuronal function
• 4 minutes causes permanent injury
• virtually no glucose stored in the brain
• low blood glucose to brain can cause
• mental confusion
• dizziness
• convulsions
• loss of consciousness

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Blood Flow to Brain

• Blocked blood flow to brain
• arterial blockage can damage brain
• CVA cerebrovascular accident
• stroke
• most common brain disorder
• affect 500,000 people per year in US
• 1/3 leading cause of death

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Blood Brain Barrier

• Physiology
• protects CNS from harmful
• substances
• pathogens
• prevents passage from blood into interstitial
  fluid of neural tissue
• water soluble substances usually pass by active
  transport
• others pass slowly
• lipid soluble substances pass readily

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Blood Brain Barrier

• Anatomy
• cerebral arteries divide quickly into capillaries
• tight junctions seal together endothelial cells
  of CNS capillaries
• capillaries also surrounded by thick basement
  membrane
• astrocyte processes press against capillaries
• selectively pass some substances and inhibit
  others

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Cerebrospinal Fluid (CSF)

• 80-150 ml volume
• clear colorless liquid
• protects and nourishes brain spinal cord
• protects
• against chemical and physical injuries
• acting as shock absorber on which brain floats
• nourishes by carrying
• oxygen
• glucose
• other chemicals
• continuously circulates through cavities in and
  around CNS in subarachnoid space

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Cerebrospinal Fluid (CSF)

• Contributes to homeostasis in three ways
• mechanical protection
• shock absorber
• chemical protection
• circulation

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Figure 13.5a
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Formation of CSF

• CSF fills ventricles
• lateral ventricles
• located in each hemisphere of cerebrum
• separated by septum pellucidum
• third ventricle
• fourth ventricle
• CSF produced in choroid plexuses
• capillaries in walls of ventricles
• covered by ependymal cells that form CSF from
  blood plasma by filtration and secretion

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Circulation of CSF

• Cilia on ependymal cells assist with flow
• from lateral ventricles
• through interventricular foramina
• to third ventricle
• then through cerebral aqueduct
• into fourth ventricle
• enters subarachnoid space through
• median aperture
• pair of lateral apertures
• reabsorbed into blood
• arachnoid villi

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Figure 13.6a
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Figure 13.3a
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Figure 13.6c
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Concept 13.3 Cerebrum
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Cerebrum

• Seat of intelligence
• interprets sensory impulses
• controls muscular movements
• functions in emotional and intellectual processes
• Cerebral Cortex
• gray matter on outside
• receives integrates incoming outgoing
  information
• White matter on inside
• white is myelination
• Gray matter nuclei deep within white matter

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Cerebral Cortex

• enlarges faster during embryonic development than
  white matter
• rolls and folds forming
• gyri (singular gyrus)
• bulges or folds
• fissures
• deep grooves
• longitudinal fissure separates cerebrum into left
  and right hemispheres
• connected internally by corpus callosum
• sulci (singular sulcus)
• shallow fissures

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Figure 13.7a
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Figure 13.7b
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Figure 13.7c
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Cerebral White Matter

• has tracts
• myelinated and unmyelinated axons
• communicate between regions of CNS
• three types
• association tracts
• between gyri in same hemisphere
• commissural tracts
• from gyri in one hemisphere to corresponding gyri
  in other hemisphere
• projection tracts
• from cerebrum to lower parts of CNS

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Basal Nuclei

• mass of cell bodies
• two are side by side just lateral to thalamus
• globus pallidus and putamen
• third is caudate nucleus
• large head connected to smaller tail by long
  comma-shaped body
• receive input from cerebral cortex
• provide output to motor portions
• control subconscious contractions of skeletal
  muscles

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Table 13.2 part 1
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Table 13.2 part 2
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Table 13.2 part 3
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Table 13.2 part 4
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Table 13.2 part 5
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Concept 13.4 Limbic System
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Limbic System

• controls emotion, behavior, and memory
• encircles upper part of brain stem and corpus
  callosum
• ring of structures on inner border of cerebrum
  and floor of diencephalon
• controls most involuntary aspects of behavior
  related to survival
• intense pain
• extreme pleasure
• anger/rage
• affection
• recognition of fear

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Concept 13.5 Functional Areas of Cerebrum
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Functional Areas of Cerebrum

• Sensory areas
• receive sensory impulses
• Motor areas
• initiate movements
• Association areas
• complex integrative functions
• memory
• emotions
• reasoning
• will
• judgment
• personality traits
• intelligence

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Figure 13.10
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Sensory Areas

• Posterior half of both hemispheres
• behind central sulci
• most direct connections with peripheral sensory
  receptors
• primary somatosensory area
• receives impulses for touch, proprioception,
  pain, itching, tickle, thermal sensations
• localize exactly the points where sensations
  originate
• primary visual area
• receives impulses for vision
• eye to thalamus to primary visual area
• shape, color, movement of visual stimuli

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Sensory Areas

• primary auditory area
• receives impulses for basic characteristics of
  sound
• pitch and rhythm
• primary gustatory area
• receives impulses for taste
• primary olfactory area
• receives impulses for smell