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Outline I. 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 1 Spinal cord Dorsal Ventral Netter SPPA 2050 Speech Anatomy & Physiology 2 Spinal cord Gray 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 SPPA 2050 Speech Anatomy & Physiology 3 “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 SPPA 2050 Speech Anatomy & Physiology 4 “Segmental” Organization Figure 39.22 SPPA 2050 Speech Anatomy & Physiology 5 Reminder: The stretch reflex is mediated within the spinal cord SPPA 2050 Speech Anatomy & Physiology 6 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 SPPA 2050 Speech Anatomy & Physiology 7 Outline I. Anatomy of the Nervous System i. ii. iii. Central Nervous System Peripheral Nervous System Nourishment and Protection • • • Blood supply and return Meninges Ventricles and cerebrospinal fluid SPPA 2050 Speech Anatomy & Physiology 8 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 SPPA 2050 Speech Anatomy & Physiology 9 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) SPPA 2050 Speech Anatomy & Physiology 10 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 SPPA 2050 Speech Anatomy & Physiology 11 Arterial supply for CNS Fig 7-29 SPPA 2050 Speech Anatomy & Physiology 12 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 SPPA 2050 Speech Anatomy & Physiology 13 Figure 40.8 SPPA 2050 Speech Anatomy & Physiology 14 Inferior View (Circle of Willis) anterior anterior cerebral a. internal carotid a. middle cerebral a. posterior cerebral a. superior cerebellar a. basilar a. vertebral a. Anterior inferior cerebellar a. posterior SPPA 2050 Speech Anatomy & Physiology 15 Figure 40.10 SPPA 2050 Speech Anatomy & Physiology 16 Middle Cerebral Artery (MCA) Supplies • most of brain’s lateral surface • Most of – frontal lobe – temporal lobe – basal ganglia – thalamus • insula SPPA 2050 Speech Anatomy & Physiology 17 Anterior Cerebral Artery • Supplies front and medial surface of the brain. Posterior Cerebral Artery • Supplies posterior temporal lobe and occipital lobe SPPA 2050 Speech Anatomy & Physiology 18 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 SPPA 2050 Speech Anatomy & Physiology 19 Outline I. Anatomy of the Nervous System i. ii. iii. Central Nervous System Peripheral Nervous System Nourishment and Protection • • • Blood supply and return Meninges Ventricles and cerebrospinal fluid SPPA 2050 Speech Anatomy & Physiology 20 Protecting the Brain • Meninges – Layered “wrapping” of the brain • Ventricular system – Internal cavities filled with cerebrospinal fluid SPPA 2050 Speech Anatomy & Physiology 21 Meninges • Consists of three layers: – Dura mater – Arachnoid membrane – Pia mater SPPA 2050 Speech Anatomy & Physiology 22 Meninges • Mater = “mother” • Pia = “delicate” delicate mother • Arachnoid = “spider” spider mother • Dura = “tough” tough mother SPPA 2050 Speech Anatomy & Physiology 23 Meninges Figure 39.25 SPPA 2050 Speech Anatomy & Physiology 24 Dura mater • Thick, tough, fibrous layer • Headaches arise from sensory receptors within the dura mater SPPA 2050 Speech Anatomy & Physiology 25 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 SPPA 2050 Speech Anatomy & Physiology 26 Pia mater • Layer closest to the brain surface • Actually follows the surface into sulci SPPA 2050 Speech Anatomy & Physiology 27 “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 SPPA 2050 Speech Anatomy & Physiology 28 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 29 Figure 39.20 SPPA 2050 Speech Anatomy & Physiology 30 Outline I. Anatomy of the Nervous System i. ii. iii. Central Nervous System Peripheral Nervous System Nourishment and Protection • • • Blood supply and return Meninges Ventricles and cerebrospinal fluid SPPA 2050 Speech Anatomy & Physiology 31 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 SPPA 2050 Speech Anatomy & Physiology 32 Ventricles Netter SPPA 2050 Speech Anatomy & Physiology 33 Figure 39.31 SPPA 2050 Speech Anatomy & Physiology 34 Figure 39.30 SPPA 2050 Speech Anatomy & Physiology 35 SPPA 2050 Speech Anatomy & Physiology 36 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 SPPA 2050 Speech Anatomy & Physiology 37 Outline I. II. Anatomy of the Nervous System Afferent and Efferent Pathways – – Motor Pathways (Somato)Sensory Pathways III. Centers and Circuits for the Neural Control of Speech SPPA 2050 Speech Anatomy & Physiology 38 “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 SPPA 2050 Speech Anatomy & Physiology 39 Brainstem: ventral Midbrain Pons pyramids decussation Medulla Figure 39.19 SPPA 2050 Speech Anatomy & Physiology 40 Medulla pyramids SPPA 2050 Speech Anatomy & Physiology 41 Selected Structure Side of Body Cerebral cortex Basal ganglia Thalamus Cerebellum Brainstem* Contralateral Contralateral Contralateral Ipsilateral Rostral-Contralateral Caudal-Ipsilateral Ipsilateral Spinal cord *depends on body part & site within brainstem SPPA 2050 Speech Anatomy & Physiology 42 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 SPPA 2050 Speech Anatomy & Physiology 43 Primary Motor Cortex (Fig 7-38) SPPA 2050 Speech Anatomy & Physiology 44 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 SPPA 2050 Speech Anatomy & Physiology 45 Somatosensory Cortex (Fig 7-38) SPPA 2050 Speech Anatomy & Physiology 46 • Some body parts have more cortical space dedicated to them • e.g. Face, lips, tongue jaw • Indicates – Greater motor precision – Richer sensory information SPPA 2050 Speech Anatomy & Physiology 47 A real case study SPPA 2050 Speech Anatomy & Physiology 48 Primary Somatosensory Pathways (Fig 7-40) SPPA 2050 Speech Anatomy & Physiology 49 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 SPPA 2050 Speech Anatomy & Physiology 50 SPPA 2050 Speech Anatomy & Physiology 51 Pyramidal Motor Pathway (Fig 7-43) SPPA 2050 Speech Anatomy & Physiology 52 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 SPPA 2050 Speech Anatomy & Physiology 53 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) SPPA 2050 Speech Anatomy & Physiology 54 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 SPPA 2050 Speech Anatomy & Physiology 55 Contralateral vs. Bilateral Representation of Cranial Nerve Function Cranial N. Trigeminal N. Facial N. Upper Face Lower Face Glossopharyngeal N. Vagus N. Accessory N. Hypoglossal N. UMN Innervation Bilateral Bilateral Contralateral Bilateral Bilateral Bilateral Contralateral SPPA 2050 Speech Anatomy & Physiology 56 SPPA 2050 Speech Anatomy & Physiology 57 Sensorimotor Regulation • Sensory and motor function are inextricably linked • Movement generates afferent signals • Movement relies on knowledge of environment (via afferent signals) SPPA 2050 Speech Anatomy & Physiology 58 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 SPPA 2050 Speech Anatomy & Physiology 59 Outline I. Anatomy of the Nervous System II. Afferent and Efferent Pathways III. Centers and Circuits for the Neural Control of Speech SPPA 2050 Speech Anatomy & Physiology 60 Localization of speech/language? • Distributed function • However, language is prominently represented in the dominant hemisphere (which in most is the left hemisphere) SPPA 2050 Speech Anatomy & Physiology 61 Some speech & language circuits Figure 7-49 SPPA 2050 Speech Anatomy & Physiology 62 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 production Clinical • Damage: expressive or Broca’s aphasia* • Compromises expressive language • Preservation in receptive language *aphasia = loss of language function SPPA 2050 Speech Anatomy & Physiology 63 Some speech & language circuits Figure 7-49 SPPA 2050 Speech Anatomy & Physiology 64 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 language Clinical • Damage: receptive or Wernicke’s aphasia • Limited receptive language • Fluent expressive language with little content/meaning SPPA 2050 Speech Anatomy & Physiology 65 Some speech & language circuits Figure 7-49 SPPA 2050 Speech Anatomy & Physiology 66 Supplementary motor area Location • Medial surface of frontal lobe Presumed Function • Involved in planning motor sequences including preparation of movement • “Internally” generated motor plans • implicated in planning of propositional speech • Strong linkages to basal ganglia Clinical • Implicated in speech programming problems • Apraxia* of speech? *Apraxia of speech: problem with programming sequences of the speech movements SPPA 2050 Speech Anatomy & Physiology 67 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 SPPA 2050 Speech Anatomy & Physiology 68 Some speech & language circuits Figure 7-49 SPPA 2050 Speech Anatomy & Physiology 69 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 SPPA 2050 Speech Anatomy & Physiology 70 Some speech & language circuits Figure 7-49 SPPA 2050 Speech Anatomy & Physiology 71 Cerebellum Clinical • Damage: does not result in paralysis of speech musculature • Can results in ataxic dysarthria ataxia: poorly scaled and coordinated movement SPPA 2050 Speech Anatomy & Physiology 72 Other important areas • Thalamus • Somatosensory cortex • Primary & association areas of auditory cortex SPPA 2050 Speech Anatomy & Physiology 73 Some speech & language circuits Figure 7-49 SPPA 2050 Speech Anatomy & Physiology 74 SPPA 2050 Speech Anatomy & Physiology 75