Motor Speech Disorder Lecture Flashcards

Purkinje Cells

Large inhibitory neurons of the cerebellar cortex that refine motor output.

Central Nervous System (CNS)

The brain and spinal cord, responsible for integrating and coordinating all nervous functions.

Peripheral Nervous System (PNS)

All neural structures outside the CNS, including 12 cranial nerves and 31 spinal nerves.

Pyramidal Tract

Major CNS pathway containing most cortical motor neurons; mediates voluntary, fine motor control.

Brainstem

Midbrain, pons, and medulla; houses cranial nerve nuclei III–XII and vital centers.

Corticospinal Pathway

UMN tract from motor cortex to spinal nerves; controls limb and trunk movements.

Corticobulbar Pathway

UMN tract from cortex to brainstem cranial nerve nuclei; controls face, head, and neck muscles.

Neurons

Electrochemically active cells that transmit signals; functional units of the nervous system.

Cell Body (Soma)

Gray-matter portion of a neuron containing the nucleus and metabolic machinery.

Dendrite

Short projections that receive impulses from other neurons or sensory receptors.

Axon

Long fiber conducting impulses away from the soma toward muscles, glands, or other neurons.

Myelin

Fatty white sheath surrounding many axons, speeding impulse conduction.

Neuromuscular Junction

Synapse where a lower motor neuron communicates with a muscle fiber.

Gray Matter

Regions rich in neuron cell bodies, giving a gray appearance (e.g., cortex, nuclei).

White Matter

Myelinated axonal pathways that appear white; includes tracts and commissures.

Glial Cells

Supportive brain cells (e.g., astrocytes, oligodendroglia) that outnumber neurons.

Oligodendroglia

Glia that form myelin in the CNS.

Schwann Cells

Glia that form myelin in the PNS.

Astrocytes

Star-shaped glia aiding neuronal metabolism, repair, and blood–brain barrier maintenance.

Ependymal Cells

Cells lining ventricles; form choroid plexus and secrete cerebrospinal fluid.

Microglia

Phagocytic glia that transform into macrophages during CNS injury or infection.

Meninges

Three connective-tissue layers (dura, arachnoid, pia) protecting brain and spinal cord.

Pia Mater

Delicate inner meningeal layer adhering to brain surface; part of blood–brain barrier.

Arachnoid

Middle meningeal layer with web-like trabeculae and cerebrospinal-fluid circulation.

Dura Mater

Tough outer meningeal layer lining skull and brain fissures.

Epidural Space

Potential space between skull and dura; common site for hematoma.

Subdural Space

Space beneath dura; can fill with blood in head injury.

Subarachnoid Space

CSF-filled cavity beneath arachnoid surrounding brain and spinal cord.

Ventricular System

Interconnected brain cavities producing, circulating, and draining cerebrospinal fluid.

Anterior Cerebral Artery (ACA)

Supplies medial frontal and parietal lobes and anterior corpus callosum.

Middle Cerebral Artery (MCA)

Feeds lateral frontal, parietal, and superior temporal lobes; most common stroke site.

Basilar Artery

Midline brainstem vessel supplying pons and cerebellum.

Posterior Cerebral Artery (PCA)

Supplies occipital lobe, inferior temporal lobe, and thalamic regions.

Circle of Willis

Arterial ring connecting carotid and vertebrobasilar systems at brain base.

Carotid System

Anterior circulation via internal and external carotid arteries; often implicated in aphasia.

Motor System

Neural network converting thought into voluntary movement.

Primary Cortex

Initial cortical area for processing sensory input or generating motor output.

Association Cortex

Cortical areas that interpret sensory data and plan voluntary actions.

Basal Ganglia

Subcortical nuclei (caudate, putamen, globus pallidus) that regulate movement initiation and tone.

Cerebellum

Structure coordinating posture, balance, and timing of skilled movements; damage causes ataxia.

Thalamus

Relay nucleus transmitting sensory and processed motor information to cortex.

Pyramidal System (Direct)

Conscious motor pathway controlling skilled, discrete movements (corticospinal & corticobulbar).

Extrapyramidal System (Indirect)

Subconscious pathways regulating posture, tone, and automatic movements.

Lower Motor Neuron (LMN)

Motor fibers of cranial and spinal nerves; lesions cause flaccid paralysis and atrophy.

Direct Activation Pathway

Another term for pyramidal system; delivers motor commands directly to LMNs.

Indirect Activation Pathway

Extrapyramidal routes that modulate LMNs via brainstem and basal ganglia circuitry.

Final Common Pathway

LMNs whose axons actually contact muscles; last link in motor execution.

Corticopontine Tract

Pyramidal fibers projecting to pontine nuclei en route to cerebellum.

Hypokinesia

Reduced movement, often due to basal ganglia dopamine deficiency (e.g., Parkinson disease).

Hyperkinesia

Excess involuntary movement from basal ganglia dysfunction (e.g., chorea, dystonia).

Ataxia

Uncoordinated movement resulting from cerebellar lesions.

Homunculus

Somatotopic map on primary motor and sensory cortices representing body parts.

Trigeminal Nerve (CN V)

Mixed nerve providing facial sensation and mastication muscle control.

Facial Nerve (CN VII)

Mixed nerve for facial expression, taste (anterior 2/3 tongue), and salivary glands.

Glossopharyngeal Nerve (CN IX)

Mixed nerve for stylopharyngeus motor, posterior 1/3 tongue taste, and swallow onset.

Vagus Nerve (CN X)

Mixed nerve innervating palate, pharynx, larynx; key for voice and swallowing.

Accessory Nerve (CN XI)

Motor nerve to sternocleidomastoid and trapezius; aids head turn and shoulder shrug.

Hypoglossal Nerve (CN XII)

Motor nerve controlling intrinsic and extrinsic tongue muscles (except palatoglossus).

UMN Facial Palsy

Contralateral lower-face weakness sparing upper face due to cortical lesion.

LMN Facial Palsy

Ipsilateral total facial weakness with atrophy and fasciculations (e.g., Bell palsy).

Trigeminal Neuralgia

Sudden, severe facial pain along one trigeminal branch (V1, V2, or V3).

Phrenic Nerve

C3–C5 spinal nerve branch innervating the diaphragm for respiration.

Ansa Cervicalis

C1–C3 loop supplying infrahyoid muscles; sometimes used in laryngeal reinnervation.

Cerebrocerebellum

Lateral cerebellar hemisphere region implicated in planning and coordination of movement.

Genioglossus

Extrinsic tongue muscle protruding tongue; innervated contralaterally by CN XII.

Suprahyoid Muscles

Muscles above hyoid (e.g., mylohyoid) elevating hyoid and aiding jaw opening.

Infrahyoid Muscles

Muscles below hyoid that depress or stabilize it; innervated by ansa cervicalis.

Intrinsic Tongue Muscles

Muscles altering tongue shape (e.g., superior longitudinal); all CN XII.

Extrinsic Tongue Muscles

Muscles moving tongue position (e.g., styloglossus); mostly CN XII.

Corticobulbar Tract Damage

Produces spasticity or flaccidity in cranial-nerve-supplied muscles, affecting speech.

Extrapyramidal Lesion

Causes involuntary movements (dyskinesias) or altered muscle tone.

Hypesthesia

Reduced sensation; may follow trigeminal nerve lesion.

Fasciculations

Involuntary LMN muscle twitches indicating denervation.

Atrophy

Muscle wasting due to LMN loss or disuse.

Pyramidal Decussation

Crossing of corticospinal fibers in medulla leading to contralateral limb control.

Internal Capsule

White-matter structure containing all cortical afferent and efferent projections.

Cranial Nerve Modalities

Categories of function: general sensory, visceral sensory, special sensory, somatic motor, branchial motor, visceral motor.

Upper Motor Neuron (UMN)

Motor pathways (direct and indirect) that originate in the cerebral cortex and synapse on cranial- or spinal-motor nuclei; lesions produce contralateral weakness, spasticity, hyperreflexia, and other UMN signs.

Lower Motor Neuron (LMN)

Final common pathway neurons (cranial and spinal nerves) that directly innervate muscles; not damaged in isolated UUMND.

Pyramidal (Direct) Activation Pathway

Corticobulbar and corticospinal tracts that transmit voluntary movement commands; unilateral lesions cause weakness and loss of fine, skilled movement.

Extrapyramidal (Indirect) Activation Pathway

Brain-stem pathways that modulate posture, tone, and reflexes; unilateral lesions can yield spasticity, hyperreflexia, and Babinski’s sign.

Contralateral Innervation

Pattern in which most corticobulbar fibers cross to supply cranial nerves on the opposite side, explaining unilateral facial and lingual weakness in UUMND.

Cranial Nerve VII (Facial)

Supplies facial muscles; its lower-face branch receives primarily contralateral UMN input, making it vulnerable to weakness after a unilateral cortical lesion.

Cranial Nerve XII (Hypoglossal)

Innervates tongue muscles; primarily contralaterally driven, so unilateral UMN damage leads to contralateral tongue weakness.

Central Facial Weakness

Unilateral weakness of the lower face caused by UMN (supranuclear) damage, sparing emotional facial movements.

Central Lingual Weakness

Unilateral tongue weakness resulting from UMN damage, distinguished from hypoglossal (LMN) lesions by absence of atrophy or fasciculations.

Articulatory Imprecision

Common UUMND speech symptom characterized by distorted or slurred consonants due to facial and tongue weakness.

Irregular Articulatory Breakdowns

Intermittent, unpredictable distortions during speech, reflecting unilateral weakness or incoordination.

Slow Alternating Motion Rates (AMRs)

Reduced speed in rapid syllable repetition, indicating UMN weakness or spasticity.

Hypernasality

Excessive nasal resonance; mild and infrequent in UUMND because of bilateral innervation to velar muscles.

Spasticity

Velocity-dependent increase in muscle tone and tightness (hypertonia) due to hyperexcitable stretch reflexes and exaggerated tendon reflexes. Associated with Upper Motor Neuron (UMN) lesions and a characteristic feature of spastic dysarthria, often giving speech a strained or harsh quality.

Incoordination

Ataxia-like timing or force errors sometimes present in UUMND when white-matter pathways are involved.

Stroke (CVA)

Most common etiology of UUMND, especially small unilateral infarcts in the internal capsule, corona radiata, or brain-stem.

Lacunar Infarct

Small, deep cerebral stroke leaving a cavity (lacuna); frequently causes isolated UUMND without cortical signs.

Pure Motor Hemiparesis

Lacunar syndrome with unilateral weakness of face, arm, and leg, often accompanied by dysarthria.

Dysarthria-Clumsy Hand Syndrome

Lacunar syndrome featuring facial weakness, dysarthria, dysphagia, and ipsilateral hand clumsiness.

Pure Dysarthria

Lacunar variant where sudden-onset dysarthria (± facial/lingual weakness) is the main deficit; recovery is usually rapid.

Hemiplegia/Hemiparesis

Paralysis/weakness of one side of the body due to pyramidal tract damage.

Hyporeflexia

Reduced reflex responses that can appear acutely after UMN injury before spasticity develops.

Clonus

Rhythmic, involuntary muscular contractions following sudden stretch, linked to UMN lesions.