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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


  • 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


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



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


  • Anterior median fissure

    Ventral horn

    Gray commissure

    Central canal

    Lateral horn

    Spinal nerve

    Dorsal horn

    Posterior median sulcus


    Sensory nuclei:

    Somatic

    Visceral

    Motor Nuclei

    Autonomic (in lateral horn)

    Somatic

    Gray Commissure


    • 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


    Posterior funiculus (column)

    Lateral funiculus

    White commissure

    Anterior funiculus


    • Spinal Nerves:

    • 31 pairs

    • Named: point of issue –

      • Cervical – 8 pairs

      • Thoracic – 12 pairs

      • Lumbar – 5 pairs

      • Sacral – 5 pairs

      • Coccygeal – 1 pair


    Dorsal Root – sensory information

    Dorsal Root Ganglion – cell bodies of sensory neurons

    Ventral root - outgoing motor fibers

    Spinal Nerves

    Mixed nerves – sensory + motor information


    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


    • Fissure: deep groove

      • Longitudinal fissure

      • Transverse fissure

    • Gyri (gyrus): ridges

    • Sulci (sulcus): furrow, shallow groove


    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


    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


    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



    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




    Cerebrum (where?)____________________.

    • 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) (where?)____________________.

    Frontal lobe

    Central sulcus (yellow)

    precentral & postcentral gyrus

    Parietal lobe

    Parieto-occipital sulcus

    Occipital lobe

    Lateral sulcus (blue)

    Temporal lobe

    Insula

    Lobes and Fissures


    • White Matter of Cerebrum (where?)____________________.

    • 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)


    Basal Nuclei (where?)____________________.

    • 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 (where?)____________________.

    • 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


    Limbic system1
    Limbic System (where?)____________________.


    Diencephalon (where?)____________________.

    • Thalamus

      • Paired lateral, egg shaped masses

    • Hypothalamus

      • Mammillary bodies

      • Homeostatic regulatory functions

    • Epithalamus

      • Pineal gland


    Functions of hypothalamus
    Functions of Hypothalamus (where?)____________________.

    • 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 (where?)____________________.

    • 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 (where?)____________________.

    • Functions

      • Receives/acts on proprioception (muscle status) input

      • Sends motor impulses to skeletal muscles that maintain posture and balance.



    • Cerebellar (where?)____________________. 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


    Brain Stem (where?)____________________.

    • Midbrain (= mesencephalon)

    • Medulla oblongata (medulla)

    • Pons (‘bridge’)

    • Nuclei assoc. with CN III  XII


    • Midbrain: (where?)____________________.

    • 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


    Pons (where?)____________________.

    • 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


    Medulla Oblongata (where?)____________________.

    • 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 (where?)____________________.

    • 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 (where?)____________________.

    • 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 (where?)____________________.

    • "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.


    • Olfactory – CN I (where?)____________________.

    • Olfactory bulbs, tracts, information to olfactory cortex






    Aging the nervous system
    Aging & the Nervous System structures

    • 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) structures

    • 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) structures

    • 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) structures

    • 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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