SPPA 2050 Speech Anatomy & Physiology 1 Outline I.Anatomy of the Nervous System i.Central Nervous...

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SPPA 2050 Speech Anatomy & Physiology

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

Spinal cord

Netter

Ventral

Dorsal

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

“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

“Segmental” Organization

Figure 39.22

Reminder: The stretch reflex is mediated within the spinal

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

i. Central Nervous System

ii. Peripheral Nervous System

iii. Nourishment and Protection• Blood supply and return• Meninges• Ventricles and cerebrospinal fluid

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

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)

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

Arterial supply for CNS

Fig 7-29

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

Figure 40.8

Inferior View (Circle of Willis)

anterior cerebral a.

internal carotid a.

middle cerebral a.

posterior cerebral a.

basilar a.

vertebral a. Anterior inferior cerebellar a.

superior cerebellar a.

16Figure 40.10

Middle Cerebral Artery (MCA)

Supplies

• most of brain’s lateral surface

• Most of – frontal lobe– temporal lobe– basal ganglia– thalamus

• insula

Anterior Cerebral Artery

• Supplies front and medial surface of the brain.

Posterior Cerebral Artery

• Supplies posterior temporal lobe and occipital lobe

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

Protecting the Brain

• Meninges– Layered “wrapping” of the brain

• Ventricular system– Internal cavities filled with cerebrospinal fluid

Meninges

• Consists of three layers:– Dura mater– Arachnoid membrane– Pia mater

Meninges

• Mater = “mother”

• Pia = “delicate”

delicate mother

• Arachnoid = “spider”

spider mother

• Dura = “tough”

tough mother

Meninges

Figure 39.25

Dura mater

• Thick, tough, fibrous layer

• Headaches arise from sensory receptors within the dura mater

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

Pia mater

• Layer closest to the brain surface

• Actually follows the surface into sulci

“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

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)

30Figure 39.20

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

Ventricles

Netter

34Figure 39.31

35Figure 39.30

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

II. Afferent and Efferent Pathways– Motor Pathways– (Somato)Sensory Pathways

III. Centers and Circuits for the Neural Control of Speech

“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

Midbrain

Medulla

Brainstem: ventral

Figure 39.19

decussation

pyramids

Medulla

pyramids

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

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

Primary Motor Cortex

(Fig 7-38)

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

Somatosensory Cortex

(Fig 7-38)

• Some body parts have more cortical space dedicated to them

• e.g. Face, lips, tongue jaw

• Indicates– Greater motor precision– Richer sensory information

A real case study

(Fig 7-40)

Primary Somatosensory Pathways

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

(Fig 7-43)

Pyramidal Motor Pathway

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

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)

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

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

Sensorimotor Regulation

• Sensory and motor function are inextricably linked

• Movement generates afferent signals

• Movement relies on knowledge of environment (via afferent signals)

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

II. Afferent and Efferent Pathways

III. Centers and Circuits for the Neural Control of Speech

Localization of speech/language?• Distributed function• However, language is prominently

represented in the dominant hemisphere (which in most is the left hemisphere)

Some speech & language circuits

Figure 7-49

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

Figure 7-49

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

Figure 7-49

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

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

Figure 7-49

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

Figure 7-49

Cerebellum

Clinical

• Damage: does not result in paralysis of speech musculature

• Can results in ataxic dysarthria

ataxia: poorly scaled and coordinated movement

Other important areas

• Thalamus

• Somatosensory cortex

• Primary & association areas of auditory cortex

Figure 7-49

SPPA 2050 Speech Anatomy & Physiology 1 Outline I.Anatomy of the Nervous System i.Central Nervous...

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