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SPPA 2050 Speech Anatomy & Physiology
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OutlineI. Anatomy of the Nervous System
i. Central Nervous System• Basic Organization• Cerebral Hemispheres• Basal Nuclei (Basal Ganglia)• Thalamus & Hypothalamus• Cerebellum• Limbic System• Brainstem• Spinal Cord
SPPA 2050 Speech Anatomy & Physiology
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Spinal cord
Netter
Ventral
Dorsal
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Spinal cordGray matter
– Butterfly-shaped (“H”-shaped) area within spinal cord white matter
– Each “wing” is called a horn– Ventral horn – contains bodies of motor neurons– Dorsal horn – receives sensory information– Tracts from white matter terminate and often arise from this
area as well as synapses from reflexes
White matter– Tracts that project up to the brain from the body– Tracts that project from the brain to the body– Communication between segmental levels of the spinal cord
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“Segmental” Organization• Spinal cord is organized length-wise as a
series of segments that are quite similar in structure
• Each segment is associated with a pair of spinal nerves
• There is a tendency for a segment to be associated with function at a level of the body
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“Segmental” Organization
Figure 39.22
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Reminder: The stretch reflex is mediated within the spinal
cord
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Outline• Anatomy of the Nervous System
– Central Nervous System– Peripheral Nervous System
• Cranial Nerves– Know all 12 cranial nerves by name– Know sensory and motor function associated with
CN V, VII, IX, X, XI, XII
• Spinal Nerves– Remember there are 31 spinal nerves
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OutlineI. Anatomy of the Nervous System
i. Central Nervous System
ii. Peripheral Nervous System
iii. Nourishment and Protection• Blood supply and return• Meninges• Ventricles and cerebrospinal fluid
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Nourishing the CNS
• Blood is the means by which the brain is supplied oxygen and nutrients
• Brain is 2 % of body mass, but uses about 20 % of blood in the body
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Nourishing the CNS
• Glycogen: energy source for the brain• brain can’t keep stores of glycogen• Without blood, the brain quickly becomes
“malnourished” without oxygen and nutrients• Neural cell death occurs rapidly (within a few
minutes)
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Nourishing the CNS
• Blood is supplied to the body from the heart via arteries
• Blood is returned to the heart via veins– In CNS the term sinus refers to a collection of
veins
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Arterial supply for CNS
Fig 7-29
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Important Arterial Branches
• Internal Carotid Artery– Middle cerebral artery (MCA)– Anterior cerebral artery
• Vertebral Artery– Combines to form basilar artery– Basilar artery has branches that supply brainstem and
cerebellum– Basilar artery splits to become the posterior cerebral
artery
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Figure 40.8
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Inferior View (Circle of Willis)
anterior cerebral a.
anterior
posterior
internal carotid a.
middle cerebral a.
posterior cerebral a.
basilar a.
vertebral a. Anterior inferior cerebellar a.
superior cerebellar a.
SPPA 2050 Speech Anatomy & Physiology
16Figure 40.10
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Middle Cerebral Artery (MCA)
Supplies
• most of brain’s lateral surface
• Most of – frontal lobe– temporal lobe– basal ganglia– thalamus
• insula
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Anterior Cerebral Artery
• Supplies front and medial surface of the brain.
Posterior Cerebral Artery
• Supplies posterior temporal lobe and occipital lobe
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Clinical note
stroke or cerebrovascular accident (CVA)• A blockage of blood vessels in the brain• May be due to
– thrombosis (clot)– embolism (object floating through the
bloodstream)– hemorrhage (bursting blood vessel)
• can have devastating effects on communication
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OutlineI. Anatomy of the Nervous System
i. Central Nervous System
ii. Peripheral Nervous System
iii. Nourishment and Protection• Blood supply and return• Meninges• Ventricles and cerebrospinal fluid
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Protecting the Brain
• Meninges– Layered “wrapping” of the brain
• Ventricular system– Internal cavities filled with cerebrospinal fluid
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Meninges
• Consists of three layers:– Dura mater– Arachnoid membrane– Pia mater
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Meninges
• Mater = “mother”
• Pia = “delicate”
delicate mother
• Arachnoid = “spider”
spider mother
• Dura = “tough”
tough mother
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Meninges
Figure 39.25
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Dura mater
• Thick, tough, fibrous layer
• Headaches arise from sensory receptors within the dura mater
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Arachnoid membrane
• Is a web-like structure between the dura and pia mater
• There is space within the web, which is filled with cerebrospinal fluid
• This arrangement sets up a fluid cushion to protect against injury
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Pia mater
• Layer closest to the brain surface
• Actually follows the surface into sulci
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“Spaces” between mater
• Space between skull and dura mater– Extradural space
• Space between dura and arachnoid mater– Subdural space
• Space between arachnoid and pia mater– Subarachnoid space
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Clinical note
• Disease and disorder associated with the brain can actually be traced to the meninges
• Meningitis (inflammation of the meninges) – can result in impaired neurologic function
• Meningioma (tumor of the meninges)– can invade the brain and cause serious impairment in
function
• Hematoma (bruising) or hemorrhage (bleeding) can occur into spaces (extradural, subdural, subarachnoid)
SPPA 2050 Speech Anatomy & Physiology
30Figure 39.20
SPPA 2050 Speech Anatomy & Physiology
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OutlineI. Anatomy of the Nervous System
i. Central Nervous System
ii. Peripheral Nervous System
iii. Nourishment and Protection• Blood supply and return• Meninges• Ventricles and cerebrospinal fluid
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Ventricles
• 4 interconnecting fluid filled spaces within the brain
• Fluid is cerebrospinal fluid (CSF)• CSF
– produced by the choroid plexus within the ventricles
– considered to be principally protective– may be nutritive function
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Ventricles
Netter
SPPA 2050 Speech Anatomy & Physiology
34Figure 39.31
SPPA 2050 Speech Anatomy & Physiology
35Figure 39.30
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Clinical note
• Excess CSF is called hydrocephalus (literally, water on the brain), which can occur for a number of reasons and impair normal nervous system function
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OutlineI. Anatomy of the Nervous System
II. Afferent and Efferent Pathways– Motor Pathways– (Somato)Sensory Pathways
III. Centers and Circuits for the Neural Control of Speech
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“Crossed” function
• Central neural representation is often “crossed”• L cortex – sensation/motor to R side of body• R cortex – sensation/motor to L side of body• When fibers cross, they are said to decussate
Contralateral – opposite side
Ipsilateral – same side
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Midbrain
Pons
Medulla
Brainstem: ventral
Figure 39.19
decussation
pyramids
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Medulla
pyramids
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Selected Structure Side of Body
Cerebral cortex ContralateralBasal ganglia ContralateralThalamus ContralateralCerebellum IpsilateralBrainstem* Rostral-Contralateral
Caudal-IpsilateralSpinal cord Ipsilateral
*depends on body part & site within brainstem
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Cortical Representation: Motor Function
• Primary motor area is strip of cortex anterior to the central sulcus
• Names for this area– precentral gyrus– Motor strip– Motor cortex– Primary motor cortex– Brodmann Area 4
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Primary Motor Cortex
(Fig 7-38)
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Cortical Representation: Somatosensory Function
• Primary somatosensory area is a strip of cortex posterior to the central sulcus
• Names for this area– post central gyrus– Sensory strip– Primary sensory cortex– Somatosensory cortex– Brodmann Area 1, 2, 3, 5
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Somatosensory Cortex
(Fig 7-38)
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• Some body parts have more cortical space dedicated to them
• e.g. Face, lips, tongue jaw
• Indicates– Greater motor precision– Richer sensory information
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A real case study
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(Fig 7-40)
Primary Somatosensory Pathways
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Neural Pathways of Motor Control
Pyramidal (Direct) motor system• Contains projection fibers from the cerebral cortex to the
(lower) motor neurons• Includes primary motor cortex (60 %), premotor and
sensory cortex (40%)• Associated with voluntary (willful) movement
Extrapyramidal (Indirect) motor system• Neural circuitry that does not directly synapse onto
(lower) motor neurons• Includes basal ganglia and related structures• Indirectly modulates motor “instructions” sent to muscle
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SPPA 2050 Speech Anatomy & Physiology
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(Fig 7-43)
Pyramidal Motor Pathway
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Projection Fibers
• Corticospinal Tract– Fiber tract that connects cerebral cortex and
ventral horn of spinal cord
• Corticobulbar Tract– Fiber tract that connects cerebral cortex and
cranial nerve nuclei in the brainstem
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Upper vs. Lower Motor Neuron
• Upper Motor Neuron– Cell body/dendrite typically in cerebral cortex– Axon in corticospinal or corticobulbar tract– Synapses onto lower motor neuron
• Lower Motor Neuron– Cell body/dendrite in ventral horn of spinal cord or in a
cranial nerve nuclei of brainstem– Axon in peripheral nerve– Synapses onto muscle (neuromuscular junction)
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Clinical Note
• Damage to Upper Motor Neuron– Spastic paralysis– Increased muscle tone – Exaggerated reflexes
• Damage to Lower Motor Neuron– Flaccid paralysis– Absent or reduced reflexes– Decreased muscle tone– Atrophy of muscle
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Contralateral vs. Bilateral Representation of Cranial Nerve Function
Cranial N. UMN Innervation
Trigeminal N. Bilateral
Facial N.Upper Face Bilateral
Lower Face Contralateral
Glossopharyngeal N. Bilateral
Vagus N. Bilateral
Accessory N. Bilateral
Hypoglossal N. Contralateral
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SPPA 2050 Speech Anatomy & Physiology
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Sensorimotor Regulation
• Sensory and motor function are inextricably linked
• Movement generates afferent signals
• Movement relies on knowledge of environment (via afferent signals)
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Sensorimotor Regulation
• Speech production stimulates a number of sensory modalities– Tactile information– Kinesthesia/proprioception– Audition
• Short term disruptions to sensory systems do tend not to interfere with speech production
• Long term disruption may be more damaging– e.g. hearing loss
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OutlineI. Anatomy of the Nervous System
II. Afferent and Efferent Pathways
III. Centers and Circuits for the Neural Control of Speech
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Localization of speech/language?• Distributed function• However, language is prominently
represented in the dominant hemisphere (which in most is the left hemisphere)
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Some speech & language circuits
Figure 7-49
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Broca’s area
Location• anterior to the primary motor area (the face and mouth
area) on or near the inferior frontal gyrus of the dominant hemisphere (usually left)
Presumed Function• Associated with planning speech productionClinical• Damage: expressive or Broca’s aphasia*• Compromises expressive language• Preservation in receptive language
*aphasia = loss of language function
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Some speech & language circuits
Figure 7-49
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Wernicke’s area
Location• Planum temporale & posterior 2/3 of superior temporal
gyrus of dominant hemisphere (usually left)Presumed Function• Important for the understanding and formulation of
languageClinical• Damage: receptive or Wernicke’s aphasia• Limited receptive language• Fluent expressive language with little content/meaning
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Some speech & language circuits
Figure 7-49
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Supplementary motor areaLocation• Medial surface of frontal lobePresumed Function• Involved in planning motor sequences including preparation of
movement• “Internally” generated motor plans• implicated in planning of propositional speech• Strong linkages to basal gangliaClinical• Implicated in speech programming problems• Apraxia* of speech?
*Apraxia of speech: problem with programming sequences of the speech movements
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Primary Motor Cortex
Clinical
• Damage: can result in paralysis of speech musculature
• Can results in spastic dysarthria*
*dysarthria – neurologically based problem with executing speech motor patterns
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Some speech & language circuits
Figure 7-49
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Basal Ganglia
Clinical
• Damage: does not result in paralysis of speech musculature
• Can results in hypokinetic or hyperkinetic dysarthria
Hypokinetic: lack of movement
Hyperkinetic: excess movement
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Some speech & language circuits
Figure 7-49
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Cerebellum
Clinical
• Damage: does not result in paralysis of speech musculature
• Can results in ataxic dysarthria
ataxia: poorly scaled and coordinated movement
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Other important areas
• Thalamus
• Somatosensory cortex
• Primary & association areas of auditory cortex
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Some speech & language circuits
Figure 7-49
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