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Lecture 14. CNS – Gross Anatomy Bio-5 Anatomy JPHubbard Hartnell College. Brain: 4 regions 12 pairs Cranial nerves Spinal Cord Begins at foramen magnum ~18 inches Cervical/thoracic/lumbar Cervical + lumbar enlargements Conus medullaris – tapered end 31pairs spinal nerves

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lecture 14

Lecture 14

CNS – Gross Anatomy

Bio-5 Anatomy

JPHubbard

Hartnell College

slide2

Brain:

    • 4 regions
    • 12 pairs Cranial nerves
  • Spinal Cord
    • Begins at foramen magnum
    • ~18 inches
    • Cervical/thoracic/lumbar
      • Cervical + lumbar enlargements
    • Conusmedullaris – tapered end
    • 31pairs spinal nerves
      • Caudaequina
    • Filumterminale: fibrous extension into sacral canal – part of coccygeal ligament
slide3
Coverings of CNS: Meninges
  • Continuous over brain and spinal cord
  • Dura mater – single layer
    • dense irregular CT + simple squamous
    • Epidural space: adipose + blood vessels
    • Subdural space filled with interstitial fluid
    • Dural sinuses -
  • Arachnoid mater =
    • Subarachnoid space = CSF
    • Extends to ~ S2
    • Spinal tap – L1-L2
  • Pia mater
    • thin layer covers BV
    • denticulate ligaments hold in place
slide5
Organization of Gray Matter - Nuclei:
    • Posterior Horn:
      • somatic and visceral (autonomic) sensory association nuclei – association or interneurons
    • Anterior Horn:
      • somatic motor nuclei (efferent: to skeletal muscles)
    • Lateral gray horns (only in thoracic & upper lumbar regions):
      • Autonomic motor : to viscera
        • Sympathetic outflow
  • Gray commissures
    • Axons of interneurons crossing spinal cord
slide6

Anterior median fissure

Ventral horn

Gray commissure

Central canal

Lateral horn

Spinal nerve

Dorsal horn

Posterior median sulcus

slide7
Sensory nuclei:

Somatic

Visceral

Motor Nuclei

Autonomic (in lateral horn)

Somatic

Gray Commissure

slide8
White matter
    • 3 paired Columns (funiculi) – named for location
      • Contain Tracts – similar origin/destination
        • Ascending: sensory information – largely dorsal and lateral
        • Descending: motor information – ventral or lateral
        • Transverse: commissural tracts
  • Generalities:
    • Cross (decussate)
    • Involve 2 or 3 neurons
    • Exhibit somatotopy
    • paired
slide9
Posterior funiculus (column)

Lateral funiculus

White commissure

Anterior funiculus

slide10

Spinal Nerves:

  • 31 pairs
  • Named: point of issue –
    • Cervical – 8 pairs
    • Thoracic – 12 pairs
    • Lumbar – 5 pairs
    • Sacral – 5 pairs
    • Coccygeal – 1 pair
slide11

Dorsal Root – sensory information

Dorsal Root Ganglion – cell bodies of sensory neurons

Ventral root - outgoing motor fibers

Spinal Nerves

Mixed nerves – sensory + motor information

slide12

Reflex Arcs

  • Monosynaptic:
    • single synapse in CNS
    • Simple, fast
      • sensory
      • motor neuron
  • Polysynaptic:
    • Multiple synapses – two or more
    • Sensory neuron
    • Motor neuron
    • 1 or more interneurons –
      • Complex control – more than one effector may be stimulated
4 principal parts of the brain
4 Principal Parts of the Brain

Cerebrum

Cerebellum

Diencephalon

Brain Stem

slide14

Fissure: deep groove

    • Longitudinal fissure
    • Transverse fissure
  • Gyri (gyrus): ridges
  • Sulci (sulcus): furrow, shallow groove
slide15

Dura mater

  • Cranial dural septa – stabilize and support
    • Falxcerebri = in longitid. fissure
      • Incl. superior and inf. sagital sinuses
      • Attaches to cristagalli and internal occipital crest
    • Tentoriumcerebelli – transverse fissure
    • Falxcerebelli = between hemispheres of cerebellum
    • Diaphragmasellae – over sellaturcica
  • Dural sinuses: between endosteal and meningeal layers of dura mater
    • Superior sagital sinus
    • Transverse sinus
    • Collect blood from circulation around brain + CSF
    • CSF drains via arachnoid granulations
slide18
Ventricles
  • Hollow spaces within brain – 4
  • 2 lateral ventricles (1 & 2) : cerebrum
    • Separated by septum pellucidum
  • Third ventricle: within diencephalon
    • Interventricular foramen connects to lateral ventricles
  • Forth ventricle: in brain stem
    • Cerebral aqueduct = aqueduct of midbrain connects to 3rd ventricle
    • Aperatures communicate with subarachnoid space
      • Lateral + median aperatures
  • Contain cerebrospinal fluid
  • Communicate with each other, central canal of spinal cord and with subarachnoid space
slide21
Cerebral Spinal Fluid
  • 20 ml/hr from plasma at choroid plexus
  • Composition regulated by ependymal cells –
  • Flow: ventricles  Central canal of spinal cord  sub-arachnoid space  returned to dural sinuses via arachnoid granulations
slide22

Hydrocephalus – failure to reabsorb CSF

  • Genetic
  • Birth defects
  • Disease – meningitis
  • Aneurism
  • Trama
  • tumors
slide23
Blood Brain Barrier
  • Provides constant environment in CNS
    • Endothelium of capillaries form tight junctions
    • Thick basal lamina
    • Bulbous feet of astrocytes
  • Specialized transport characteristics
    • In:
      • Glucose, essential AA, certain electrolytes
    • Not in:
      • Drugs, proteins, toxins, metab. Wastes
    • Pumped out:
      • Non-essential AA, K+
    • Get in anyhow:
    • Lipid soluble substances
  • Not uniform – more permeable in certain retgions
slide25
CSF is produced at ______________________ which are located (where?)____________________.
  • What regulates its composition?
  • Where does it go?
  • How does interstitial fluid in the brain differ from that in other tissues?
slide26

White matter: transmission of information in tracts

  • Gray matter: integration
  • Centers: aggregates of cell bodies
  • Nuclei: centers with defined borders
slide27

Cerebrum

  • Cortex: gray matter – 5 lobes
    • Contains:
      • Motor areas
      • Sensory areas
      • Association areas
    • Contralateral
    • Lateralization
    • Diff. areas involved in actions – communication
lobes and fissures
Longitudinal fissure (green)

Frontal lobe

Central sulcus (yellow)

precentral & postcentral gyrus

Parietal lobe

Parieto-occipital sulcus

Occipital lobe

Lateral sulcus (blue)

Temporal lobe

Insula

Lobes and Fissures
slide29

White Matter of Cerebrum

  • Myelinated fibers in tracts – 3 types
    • Commissures – transverse – connect corresponding areas in different hemispheres
      • Corpus callosum
      • Anterior commissure
      • Posterior commissure
    • Association fibers
      • Long and short – connect w/i hemisphere
    • Projection fibers: run vertically – tie to lower brain stem
      • Tie to sensory receptors/motor effectors
        • Internal capsule – fans out from top of brain stem (corona radiata)
slide30

Basal Nuclei

  • 3 masses
  • Caudate nucleus
  • Putnam + globus passidus = lentiform nucleus
    • Influence muscle movement
    • Disorders associated with Huntington’s Chorea, Parkinson’s Dosease
limbic system
Limbic System
  • System of tracts
  • Learning – retention and utilization of past memories
  • Blends emotions with higher mental functions
  • Hippocampus – modifies behavior based on prior experience
  • Amygdala – emotions/past experiences
slide34
Diencephalon
  • Thalamus
    • Paired lateral, egg shaped masses
  • Hypothalamus
    • Mammillary bodies
    • Homeostatic regulatory functions
  • Epithalamus
    • Pineal gland
functions of hypothalamus
Functions of Hypothalamus
  • Controls and integrates activities of the ANS which regulates smooth, cardiac muscle and glands
  • Synthesizes regulatory hormones that control the anterior pituitary
  • Contains cell bodies of axons that end in posterior pituitary where they secrete hormones
  • Regulates rage, aggression, pain, pleasure & arousal
  • Feeding, thirst & satiety centers
  • Controls body temperature
  • Regulates daily patterns of sleep
hypothalamus
Hypothalamus
  • Dozen or so nuclei in 4 major regions
    • mammillary bodies are relay station for olfactory reflexes;infundibulum suspends the pituitary gland
  • Major regulator of homeostasis
    • receives somatic and visceral input, taste, smell & hearing information; monitors osmotic pressure, temperature of blood
cerebellum
Cerebellum
  • Functions
    • Receives/acts on proprioception (muscle status) input
    • Sends motor impulses to skeletal muscles that maintain posture and balance.
slide41
2 cerebellar hemispheres and vermis (central area)
  • 3 lobes w/I each hemisphere
    • Anterior lobe
    • Posterior lobe
    • Flocculonodular lobe
slide42
Cerebellar cortex (folia) & central nuclei are grey matter
  • Arbor vitae = tree of life = white matter
  • Purkinje cells – extend from gray matter to cerebellar nuclei
  • Tracts in cerebellar peduncles carry info to other brain regions
slide43
Brain Stem
  • Midbrain (= mesencephalon)
  • Medulla oblongata (medulla)
  • Pons (‘bridge’)
  • Nuclei assoc. with CN III  XII
slide44

Midbrain:

  • Cerebral peduncles ‘little feet’ of cerebrum
    • Ventral
    • Connect to sp. cord motor tracts
  • Cerebellar peduncles – dorsal
  • Nuclei
    • Corpora quadregemina – dorsal domelike
      • Superior colliculi – eye movements
      • Inferior colliculi – auditory relay centers
    • Substantia nigra – prod. of dopamine
    • Red necleus – relay motor pathways
slide46
Pons
  • One inch long
  • White fiber tracts ascend and descend
  • Pneumotaxic & apneustic areas help control breathing
  • Middle cerebellar peduncles carry sensory info to the cerebellum
  • Cranial nerves 5 thru 7
slide47

Medulla Oblongata

  • Ascending sensory/ Descending motor tracts VIII-XII
  • Nuclei of 5 cranial nerves
  • Cardiovascular center
    • force & rate of heart beat
    • diameter of blood vessels
  • Respiratory center
    • medullary rhythmicity area sets basic rhythm of breathing
  • Information in & out of cerebellum
  • Reflex centers for coughing, sneezing, swallowing etc
reticular formation
Reticular Formation
  • Scattered nuclei in medulla, pons & midbrain
  • Reticular activating system
    • alerts cerebral cortex to sensory signals (sound of alarm, flash light, smoke or intruder) to awaken from sleep
    • maintains consciousness & helps keep you awake with stimuli from ears, eyes, skin and muscles
  • Motor function is involvement with maintaining muscle tone
brain injuries
Brain Injuries
  • Causes of damage
    • displacement or distortion of tissue at impact
    • increased intracranial pressure
    • infections
    • free radical damage after ischemia
  • Concussion---temporary loss of consciousness
    • headache, drowsiness, confusion, lack of concentration
  • Contusion--bruising of brain (less than 5 min unconsciousness but blood in CSF)
  • Laceration--tearing of brain (fracture or bullet)
    • increased intracranial pressure from hematoma
cranial nerves
Cranial Nerves
  • "On Old Olympic Towering Top A Finn And German Viewed A Hop.”
  • Olfactory- smell.
  • Optic- vision.
  • Oculomotor- eyelid & eyeball movement.
  • Trochlear-innervates superior oblique, turns eye downward and laterally.
  • Trigeminal- face & mouth touch & pain, chewing.
  • Abducens- turns eye laterally.
  • Facial-controls most facial expressions, tears & saliva secretion, taste.
  • Auditory (Vestibulocochlear)- hearing, equilibrium sensation.
  • Glossopharyngeal- taste, senses carotid blood pressure.
  • Vagus- senses aortic blood pressure, slows heart rate, stimulates digestive organs, taste, coughing, swallowing, voice production.
  • Accessory- controls trapezius, sternocleidomastoid, swallowing
  • Hypoglossal- controls tongue movement.
slide52

Olfactory – CN I

  • Olfactory bulbs, tracts, information to olfactory cortex
slide53

Visual Information – CN II – Optic

    • Optic chiasm – crossing of optic tracts  to visual cortex via optic projection tracts – visual information split
slide54

Motor information – mastication

  • Trigeminal – CN V – mandibular branch
slide56

Parasympathetic information to visceral organs

  • X – vagus
  • III, IV and IX also carry parasympathetic motor information but not to gut
aging the nervous system
Aging & the Nervous System
  • Years 1 to 2
    • rapid increase in size due to increase in size of neurons, growth of neuroglia, myelination & development of dendritic branches
  • Early adulthood until death
    • brain weight declines until only 93% by age 80
    • number of synaptic contacts declines
    • processing of information diminishes
    • conduction velocity decreases
    • voluntary motor movements slow down
    • reflexes slow down
cerebrovascular accident cva
Cerebrovascular Accident (CVA)
  • Third leading cause of death after heart attacks and cancer
  • 2 types of strokes
    • ischemic due to decreased blood flow
    • hemorrhagic due to rupture of blood vessel
  • Risk factors
    • high blood pressure, high cholesterol, heart disease, diabetes, smoking, obesity, alcohol
  • Tissue plasminogen activator (t-PA) used within 3 hours of onset will decrease permanent disability
transient ischemic attack tia
Transient Ischemic Attack (TIA)
  • Episode of temporary cerebral dysfunction
  • Cause
    • impaired blood flow to the brain
  • Symptoms
    • dizziness, slurred speech, numbness, paralysis on one side, double vision
    • reach maximum intensity almost immediately
    • persists for 5-10 minutes & leaves no deficits
  • Treatment is aspirin or anticoagulants; artery bypass grafting or carotid endarterectomy
alzheimer disease ad
Alzheimer Disease (AD)
  • Dementia = loss of reasoning, ability to read, write, talk, eat & walk
  • Afflicts 11% of population over 65
  • Loss of neurons that release acetylcholine
  • Plaques of abnormal proteins outside neurons
  • Tangled protein filaments within neurons
  • Risk factors -- head injury, heredity
  • Beneficial effects of estrogen, vitamin E, ibuprofen & ginko biloba
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