Objectives

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Objectives

• 1. Describe the organization of the nervous
  system identifying organs belonging to the
  central and peripheral divisions
• 2. Explain the relationship between the PNS, CNS,
  ANS, somatic, sympathetic and parasympathetic
  divisions of the nervous system

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Objectives

• 3. Compare the structure and function of the
  somatic and autonomic nervous systems
• 4. Describe the layers protecting the brain and
  spinal cord
• 5. Illustrate cross sectional and longitudinal
  spinal cord structures

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Objectives

• 6. Identify the principal sensory and motor
  tracts within the spinal cord
• 7. Describe the components of a reflex arc

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Objectives

• 8. Explain the development of the brain
• 9. Discuss the formation, location and function
  of cerebrospinal fluid
• 10. Explain the blood supply to the brain and the
  function of the blood-brain barrier

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Objectives

• 11. Describe the structures and functions
  associated with the brain stem, diencephalon,
  midbrain, reticular formation, limbic system,
  cerebrum and cerebellum and basal nuclei
• 12. Describe the relationship between the
  hypothalamus and the pituitary
• 13. Discuss the structural and functional
  divisions of the pituitary and the hormones
  produced by each

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Objectives

• 14. Explain why the pituitary is often referred
  to as the master gland
• 15. Identify the 12 pairs of cranial nerves by
  name, number, type, location and function

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Objectives

• 16. Describe the principal sensory modalities and
  organs associated with each
• 17. Explain the structure and function of the eye
  as an organ of special sense
• 18. Explain the structure and function of the ear
  as an organ of special sense

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Objectives

• 19. Define and use the correct terminology
  associated with the nervous system
• 20. Discuss the effects of aging on the nervous
  and sensory systems

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Nervous System
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Anatomical Divisions

• Central (CNS)
• Peripheral (PNS)

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Central Nervous System CNS

• Brain
• Spinal cord

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Peripheral Nervous System PNS

• Cranial nerves
• Spinal nerves

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PNS

• Cranial and spinal nerves contain
• Afferent/sensory neurons
• carries sensory information into CNS
• Efferent/motor neurons
• carries impulses from CNS to muscle or glands

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Functional Divisions PNS

• Efferent PNS
• Somatic nervous system (SNS)
• voluntary control of skeletal muscle
• Autonomic nervous system (ANS)
• automatic, involuntary control of cardiac muscle,
  smooth muscle and glands

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Autonomic Nervous System (ANS)

• Two Divisions (Efferent)
• Parasympathetic
• Sympathetic

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Parasympathetic Division

• Stimulates visceral responses
• Maintains vegetative functions
• Continuously active
• Uses acetylcholine type transmitter substances,

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Sympathetic Division

• Responds to environmental stress
• fight or flight
• Epinephrine transmitter substances
• Multiple systems activated simultaneously

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Spinal CordLongitudinal Profile

• From medulla oblongata to L-2.
• Cylindrical.
• Cervical enlargement C-3 to T-2.
• Lumbar enlargement T-9 to T-12.

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Spinal CordLongitudinal Profile

• Conus medullaris - tapered region from T12 to
  L-2.
• Cauda equina - exiting spinal nerves at distal
  end.
• Filum terminale - extension of Pia from conus to
  coccyx.

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Spinal Cord
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Spinal CordLongitudinal Profile

• Divided into 31 spinal segments spinal cord
  plus associated spinal nerve pairs.
• Longitudinal grooves.
• Anterior median fissure on ventral surface (deep,
  wide).
• Posterior median sulcus on dorsal surface
  (shallow, narrow).

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Spinal Cord Cross Section

• Central canal.
• Contains CSF.
• Lined with ependymal cells.
• Continuous with 4th ventricle.

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Spinal Cord Cross Section

• Gray matter (unmyelinated).
• H or butterfly shaped.
• Location of synapses, cell bodies, nuclei, glial
  cells.
• 6 Horns extend from center.
• anterior/ventral horns.
• posterior/dorsal horns.
• lateral horns (not in cervical region).

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Spinal Cord
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Spinal Cord Cross Section

• White matter (myelinated).
• Organized into 6 columns/funiculi by gray matter
  landmarks and fissures.
• anterior/ventral columns.
• posterior/dorsal columns.
• lateral columns.

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Spinal Cord Tracts

• Ascending, sensory tracts/fasciculi, from sensory
  organs to brain,
• some named according to major landmarks,
  crossover points,

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Spinal Cord Tracts
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Spinal Cord Tracts

• many are contralateral i.e., enter on one side,
  crossover to opposite side of brain
  (decussation),
• three general divisions according to pathway
  region.

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Ascending Tracts Spinothalamic Pathways.

• Lateral spinothalamic tract.
• Pain.
• Temperature.
• Ventral spinothalamic tract.
• Pressure.
• Touch.

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Ascending TractsPosterior Column

• Fasciculus gracilis (lower body).
• proprioception.
• fine touch.
• )pressure.
• Fasciculus cuneatus (upper body).
• Proprioception.
• fine touch.
• pressure.

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Ascending TractsSpinocerebellar Pathways

• Dorsal spinocerebellar.
• proprioception.
• Ventral spinocerebellar.
• proprioception.

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Descending Tracts

• Descending motor tracts/fasciculi - from brain to
  skeletal muscles
• Divided into pyramidal and extrapyramidal groups

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Descending Pyramidal Tracts

• Voluntary control of skeletal muscles.

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Descending Spinal Cord Pyramidal Tracts

• Named because of pyramid shaped cells of motor
  cortex from which these arise and because they
  travel along pyramid shaped bands of ventral
  medulla.

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Descending Spinal Cord Pyramidal Tracts

• lateral corticospinal.
• fine motor control limbs.
• anterior corticospinal.
• fine motor control - limbs.
• corticobulbar tract.
• motor control - face and neck.

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Descending Spinal Cord Extrapyramidal Tracts

• Travel outside of pyramids,
• regulate involuntary motor action,
• may override pyramidal tract information,
• generally involved in maintaining posture,
  balance, muscle tone,
• named according to location of processing
  centers.

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Extrapyramidal Tracts

• Rubrospinal
• Tectospinal
• Vestibulospinal
• Reticulospinal

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Descending Spinal Cord Extrapyramidal Tracts

• rubrospinal.
• arises in red nucleus.
• affects axial skeleton.
• tectospinal.
• arises in tectum (midbrain).
• triggered by auditory and visual stimuli.
• affect muscle of the head, neck, arms.

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Descending Spinal Cord Extrapyramidal Tracts

• vestibulospinal.
• arises in inner ear (posture balance).
• affects muscles of head, neck, eyes limbs.
• reticulospinal.
• arise in reticular formation, pons, medulla.
• adjusts flexors extensors to avoid opposition,
  maintain muscle tone.

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Reflex Arc

• Protective mechanism, maintain homeostasis
• Fast
• Bell-Magiendie law
• 5 essential components
• Sense organ
• Afferent sensory neuron
• CNS
• Efferent motor neuron
• Effector organ

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Reflex Arc
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Reflex Arc Components

• Sense organ
• Afferent sensory neuron
• part of spinal nerve
• enters into spinal cord via dorsal root

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Reflex Arc Components

• CNS
• commonly gray matter of spinal cord
• may have interneurons
• simplest form - monosynaptic, no interneurons
• Efferent motor neuron
• exits spinal cord via ventral root
• does not synapse once it leaves spinal cord
• Effector organ
• somatic skeletal muscle
• visceral smooth muscle, cardiac muscle or gland

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Reflex Arc
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Meninges and Spaces

• Epidural space between bone and outer meningeal
  layer, CT, adipose.
• Dura mater.
• Outermost.
• Dense, irregular CT.

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Meninges and Spaces

• Subdural space - interstitial fluid.
• Arachnoid mater.
• Cobweb-like appearance.
• Collagen and elastic fibers.

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Meninges and Spaces

• Subarachnoid space - CSF circulates, provides
  nutrients, oxygen to underlying brain, spinal
  cord tissue.
• Pia mater.
• Delicate mother.
• Adheres to brain, spinal cord.
• Attaches blood vessels.
• Attaches outwardly to Dura m. via denticulate
  ligaments.

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Brain Development

• Hollow tube
• 3 Primary vesicles (3-4 weeks)
• Prosencephalon (forebrain)
• Mesencephalon (midbrain)
• Rhombencephalon (hindbrain

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Brain Development
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Brain Development

• 5 Secondary vesicles (5 weeks)
• Telencephalon
• Diencephalon
• Mesencephalon
• Metencephalon
• Myelencephalon

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Brain Development
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Brain Ventricles

• Remnants of hollow neural tube development

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Brain Ventricles

• Four interconnected chambers
• I II right and left lateral ventricles
  separated medially by septum pellucidum
• communicate with third ventricle via
  interventricular foramen/foramen of Munro

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Brain Ventricles

• III - vertically flat region between diencephalon
  hemispheres
• surround massa intermedia of thalamus
• communicate with fourth ventricle via cerebral
  aqueduct/aqueduct of Sylvius
• IV - located between the cerebellum and pons
• dumps CSF into subarachnoid space via median
  aperture/foramen of Magiendie and 2 lateral
  apertures/foramina of Lüschka
• communicates directly with central canal of
  spinal cord

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Brain Ventricles
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Cerebrospinal Fluid

• Provides mechanical protection for brain by
  acting as shock absorber/floating cushion for
  brain
• Provides chemical support for brain by providing
  nutrients
• CSF constantly manufactured via choroid plexus at
  roof of third ventricle and floor of lateral
  ventricles and underlying the 4th ventricle

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Cerebrospinal Fluid

• Formed as plasma escapes the vascular choroid
  plexus
• Constantly being produced at a rate of 20 ml/hr
  and reabsorbed via arachnoid villi
• Total volume of CSF 150ml in ventricles and
  subarachnoid space

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Cerebrospinal Fluid Circulation
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Blood-brain Barrier (BBB)

• Physiological barrier created by endothelium of
  brain capillaries that is tightly connected
• Molecules must be actively (and selectively)
  transported
• Vessels are leaky in choroid plexus, material
  must pass through the CSF first before reaching
  brain tissue
• Exceptions to BBB at hypothalamus and pineal

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CSF Pathology Hydrocephalus

• Mechanical defect (drainage pathway)
• Physiological defect (rate of CSF production
  exceeds reabsorption)

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Hydrocephalus
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Brain Stem

• Medulla
• Pons
• Midbrain /mesencephalon
• Reticular formation

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Brain Stem
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Brain Stem
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Brain Stem
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Medulla Oblongata

• 3 cm long
• Functionally part of reticular formation

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Medulla
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Medulla

• White matter
• Contains ascending and descending tracts and
  decussation points (pyramidal tracts)

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Medulla

• Gray matter
• Origin of CN- VIII (part), IX, X, XI, XII
• Olive - ventrolateral bulge, relay point
• Autonomic reflex functions
• respiratory rhythm
• Digestion
• heart rate, strength
• vasoconstriction vasodilation

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Pons

• 2.5 cm long, oval
• Links cerebellar hemispheres
• Functionally part of reticular formation
• Origin of CN - V, VI, VII, VIII (part)
• Relays commands from cerebellum
• Regulate respiration via
• pneumotaxic center
• apneustic center

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Pons
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Midbrain / Mesencephalon

• 2.5 cm from pons to diencephalon
• Tectum corpora quadrigemina
• 2 superior colliculi
• reflex center for visual stimuli - eyes, head,
  neck
• 2 inferior colliculi
• reflex center for auditory stimuli - head, neck
• contains some basal nuclei
• substantia nigra
• red nucleus
• part of medial lemniscus

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Midbrain / Mesencephalon

• Superior cerebellar peduncles attach midbrain to
  cerebellum
• Cerebral peduncles attach cerebrum to pons,
  medulla
• Cerebral aqueduct of Sylvius passes through
  midbrain

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Mesencephalon
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Reticular Formation

• Reticular formation
• Functional area rather than anatomically discreet
  area
• Gray matter nuclei among white matter of
• Medulla
• Pons
• Midbrain
• Wakefulness center, alerts cerebrum to incoming
  sensory information

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Diencephalon

• Thalamus
• Hypothalamus
• Epithalamus
• Subthalamus
• Pituitary/hypophosis

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Thalamus

• 3cm oval shape
• 80 of diencephalon
• Hemispheres joined at massa intermedia

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Thalamus

• Major relay station of all communication and
  sensory information (except smell) to cerebrum,
  as part of relaying function, it must sort info
  to direct to appropriate cortical area

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Thalamus

• Four major groups of nuclei, separated by
  internal medullary lamina
• anterior - part of limbic system, emotions,
  memory
• medial - integrates, projects sensory
  information to cerebrum

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Thalamus
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Thalamus

• ventral - touch, pressure, pain, taste,
  proprioception senses projected to sensory
  cortex, cerebellar relay
• ventral posterior - general sensory
• ventral lateral - cerebellar input
• ventral anterior - cortical relay

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Thalamus

• posterior -three subdivisions
• pulvinar - general sensory projection
• lateral geniculate - projection of vision to
  occipital cortex
• medial geniculate- projection of audition to
  temporal cortex

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Hypothalamus

• Inferior portion of diencephalon below the
  thalamus, between optic chiasma and mammillary
  bodies
• Attaches inferiorly to pituitary/hypophysis via
  infundibulum
• Blood-brain barrier absent
• Primary link between nervous and endocrine
  systems

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Hypothalamus
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Hypothalamic Regions

• supraoptic region - regulates water loss
• preoptic region - regulates body temperature

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Hypothalamic Regions

• Four regions
• mammillary region
• mammillary bodies - swallowing reflex
• posterior nucleus - autonomic activity
• tuberal region
• tuber cinerum (gray matter) - inhibits some
  hormones
• infundibulum - physical attachment to pituitary
• medial eminence emotions

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Hypothalamus Functions

• Homeostasis
• autonomic regulation of smooth, cardiac and
  endocrine activity
• regulates body temperature
• coordinates between voluntary and autonomic
  influences

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Hypothalamus Functions

• rage and aggression
• hunger and satiety
• thirst
• wakefulness

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Phineas Gage
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Epithalamus

• Epithalamus and pineal gland/epiphysis cerebri
• Superior edge of diencephalon
• Pineal produces melatonin hormone
• melatonin formed from serotonin
• involved in circadian rhythms, sleep
  wakefulness
• slows maturation of gametes

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Subthalamus

• below the thalamus
• Part of substantia nigra and red nucleus extend
  here

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Pituitary/Hypophysis

• Spherical, in sella turcica of sphenoid
• Two portions
• Anterior
• Posterior

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Anterior Pituitary

• anterior/adenohypophysis
• 75 of gland
• true glandular tissue

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Anterior Pituitary

• regulated by releasing and inhibiting factors of
  the hypothalamus
• blood supply via superior hypophyseal arteries
  and hypophyseal portal veins

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Pituitary Circulation
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Anterior Pituitary

• divided into
• pars distalis
• pars intermedia
• produces 7 hormones from 5 cell types, some are
  tropic/trophic hormones, all are peptide-protein
  type

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Ant. Pit. Hormones

• hGH/human growth hormone somatotroph

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Ant. Pit. Hormones

• ACTH/adrenocorticotropichormone- corticotroph

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Ant. Pit. Hormones

• TSH/thyroid stimulating hormone thyrotroph

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Ant. Pit. Hormones

• PRL/prolactin (LTH) lactotroph

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Ant. Pit. Hormones

• FSH/follicle stimulating hormone- gonadotroph

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Ant. Pit. Hormones

• LH/ICSH/leuteninzing hormone/interstitial cell
  stimulating hormone

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Ant. Pit. Hormones

• MSH/ melanocyte stimulating hormone

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Posterior Pituitary

• posterior/ neurohypophysis/pars nervosa
• stores and releases hormones produced in the
  hypothalamus
• two hormones
• OT/oxytocin
• ADH/antidiuretic hormone/vasopressin

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Pituitary Circulation
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Pituitary Pathologies

• Diabetes insipidus - ADH
• Pituitary dwarfism - hGH
• Giantism - hGH
• Acromegaly - hGH

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Acromegaly
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Limbic System
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Limbic System

• Genesis of some emotional responses and behaviors
  e.g. pain, pleasure, maternal behavior, circadian
  rhythms

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Limbic System Brain Stem, Diencephalon,
Cerebrum

• Reticular formation of brain stem
• Thalamus anterior
• Hypothalamus anterior
• Hippocampus
• Fornix
• Mammillary bodies

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Limbic System Brain Stem, Diencephalon,
Cerebrum

• Amygdala
• Limbic lobe
• Parahippocampal gyrus
• Cingulate gyrus
• Dentate gyrus
• Olfactory bulbs

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Basal Nuclei / Basal Ganglia

• Concentrations of gray matter synapses within
  the CNS
• Two general locations
• Mesencephalon
• Diencepphalon

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Basal Nuclei
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Basal Nuclei / Basal Ganglia Mesencephalon

• Red nucleus - integrates cerebral and cerebellar
  output, posture and balance
• Substantia nigra- regulates cerebral output

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Basal Nuclei / Basal GangliaDiencephalon

• Corpus striatum
• Caudate nucleus - maintain pattern and rhythm of
  skeletal muscle movement
• Lentiform nucleus
• putamen - gross movements of skeletal muscle
• globus pallidus -regulate muscle tone
• internal capsule

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Basal Nuclei / Basal Ganglia

• Claustrum - visual coordination
• Amygdala
• Subthalamic nuclei

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Basal Nuclei
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Basal Nuclear Pathologies

• Parkinsonism - substantia nigra
• Huntingtons Chorea - corpus striatum

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Cerebellum

• Function in skeletal muscle coordination, adjusts
  afferent and efferent inputs, organizes agonist
  and protagonist muscles
• Rapid automatic adjustments to maintain posture
  and balance
• Fine motor control, learned patterns of movement
• Located in posterior cranial fossa
• Separated from cerebrum via transverse fissure

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Cerebellum
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Cerebellum
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Cerebellum

• 2 hemispheres held together at vermis
• Gray matter in folia with white central core -
  arbor vitae
• Attached to brain stem via cerebellar peduncles -
  superior, middle and inferior
• 3 lobes
• Anterior - voluntary action and posture
• Posterior - subconscious skeletal movements
• Flocculonodular balance

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Cerebellum
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Cerebellar Pathologies

• Ataxia
• Intention tremor
• Dysmetria

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Cerebrum

• Largest mass of brain
• Superficial gray matter cortex
• Raised gyri convolutions
• Grooves sulci

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Cerebrum
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Sulci Gyri
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Cerebral Fissures

• Longitudinal/midsagittal - right and left
  hemispheres
• contains falx cerebri (cranial dura)
• Central/fissure of Rolando - frontal and parietal
  lobe
• Lateral/fissure of Sylvius - frontal and temporal
• Parieto occipital - parietal and occipital
• Transverse - cerebrum and cerebellum

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Cerebrum
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Hemispheres Lobes

• Frontal
• Parietal
• Temporal
• Occipital

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Cerebral Functional Areas

• Functional area identified by number
• Brodmanns classification

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Functional Areas

• Sensory areas receive sensory information
• Motor areas initiate motor stimuli
• Association areas address complex integration of
  functions
• Brain lateralization

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Frontal Cortex

• Motor cortex 4
• Premotor cortex 6
• Frontal eye field 8
• Social center
• Abstract intellectual functions

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Frontal Cortex

• Motor speech (left) 44
• Mathematical/scientific (left)
• Spatial relationships (right)
• Music and art (right)
• Visualization (right)

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Frontal Cortex
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Parietal Cortex

• sensory cortex 3
• somesthetic association area 1,2,
• Taste 43

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Temporal Cortex

• auditory cortex 42
• auditory association (Wernickes)22
• language
• Olfaction
• Gnostic (common integration) 5, 7, 39

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Temporal Cortex
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Occipital Cortex

• visual cortex 17
• visual association 18,19

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Homunculus

• graphic representation of the relative amount of
  cortex devoted to addressing sensory
  interpretation or motor control

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Homunculus
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Cerebrum White Matter

• Myelinated
• Communication fibers
• association fibers - within hemisphere
• projection fibers - ascending and descending
• commissural - between hemispheres

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Corpus Callosum

• Commissural fibers
• Rostrum
• Genu
• Splenium
• Fornix
• Septum pellucidum

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Cranial Nerves

• Names mnemonic
• Numbers
• Type
• Sensory
• Motor
• mixed

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Sense Organs

• Sensation a function of specialized organs that
  receive stimuli (external and internal), convert
  (transduce) that stimulus into electrical signals
  that can then be relayed (conducted) to the CNS
  for interpretation (translation)
  
• Stimulus---gtTransduction-gtConduction---gtTranslati
  on

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Sense Organs

• Sense organs respond to one form of energy most
  efficiently
• Sensory neurons convey only one modality

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Sense Organ Classification

• Kind of energy
• Chemical
• Mechanical
• Thermal
• Photo
• Pain

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Pain

• Naked nerve endings
• Located superficially, skin, periosteum, blood
  vessel walls
• Warning of tissue damage
• Can be caused by several kinds of stimuli

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Pain Classification

• Fast/sharp/prickling - immediate response,
  referred to cortex
• Slow/burning/aching - persist due to thalamic and
  reticular formation involvement
• Referred - arising viscerally, referred
  superficially
• Phantom - pain sensed in an organ not present

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Sense Organ Classification

• location of stimulus
• teleceptor distant
• interoceptor internal
• exteroceptor superficial
• proprioceptor - body position