Motor and Sensory Pathways in Speech and Hearing Anatomy

Precentral gyrus

The portion of the cortex identified by #1.

Upper Motor Neuron

The type of neuron indicated by #2.

Pyramids

The portion of the medulla indicated by #3.

Pyramidal decussation

The landmark/decussation indicated by #4.

Lower motor neuron

The type of neuron indicated by #5.

Corticospinal tract

The name of this pathway.

Voluntary motor commands

The kind of information carried by this pathway.

Descending pathway

The direction this pathway is traveling, starting in the primary motor cortex (precentral gyrus) and traveling to the spinal cord.

Four points of weakness

Cortex, Internal capsule, Brainstem, Spinal cord.

Motor weakness or paralysis

What happens when there is damage to any of the four points of weakness.

Upper motor neurons

Found in the primary motor cortex.

Weakness or paralysis, Spasticity, Hyperreflexia, Possible Babinski sign

What happens when upper motor neurons are damaged.

Lower motor neurons

Found in the anterior horn of the spinal cord or cranial nerve motor nuclei in the brainstem.

Weakness or paralysis, Flaccidity, Hyporeflexia or areflexia, Muscle atrophy, Fasciculations

What happens when lower motor neurons are damaged.

Motor homunculus representation

The size of a body part's representation reflects how much fine motor control it requires.

Innervation density

The term that describes how densely an area of the body is innervated.

Efferent pathway

A synonym for 'motor' pathway.

Neuromuscular junction (NMJ)

At the NMJ, the postsynaptic cell is a muscle fiber, not another neuron.

Acetylcholine (ACh)

The one and only neurotransmitter present at the neuromuscular junction.

Femoral nerve

The nerve labeled in the reflex arc.

Dorsal root ganglion

The nerve landmark labeled in the reflex arc.

Sensory (afferent) nerve

The nerve labeled in the reflex arc.

Motor (efferent) nerve to the quadriceps

The nerve labeled in the reflex arc.

Motor (efferent) nerve to the hamstrings

Nerve responsible for transmitting signals from the spinal cord to the hamstring muscles, causing them to contract.

Sensory receptor

GTO or spindle afferent that detects changes in stretch or tension.

Sensory (afferent) nerve

Nerve that carries sensory information from the sensory receptors to the spinal cord.

Motor (efferent) nerve to the antagonist muscle

Nerve that transmits signals to the muscle opposing the action of the effector muscle.

Motor (efferent) nerve to the effector muscle

Nerve that carries signals from the spinal cord to the muscle that produces movement.

Effector muscle

The muscle that is stimulated to contract in response to a motor nerve signal.

Primary somatosensory cortex

Region of the brain responsible for processing sensory information from the body.

Primary motor cortex

Region of the brain that generates motor commands to initiate movement.

Upper motor neuron

Neuron that originates in the brain and carries signals to lower motor neurons in the spinal cord.

Lower motor neuron

Neuron that directly innervates skeletal muscles and carries signals from the spinal cord to the muscles.

Spasticity

A condition characterized by increased muscle tone and exaggerated reflexes due to upper motor neuron damage.

Hyperactive reflexes

Reflexes that are exaggerated or increased, often due to upper motor neuron damage.

Flaccid paralysis

A condition where muscles are weak and unable to contract, typically due to lower motor neuron damage.

Hyporeflexia

Reduced or absent reflexes, often associated with lower motor neuron damage.

Areflexia

The absence of reflexes, commonly due to lower motor neuron damage.

Muscle atrophy

The wasting away or decrease in muscle mass, often resulting from lower motor neuron damage.

Fasciculations

Involuntary muscle twitching, often seen in lower motor neuron damage.

Dorsal column-medial lemniscus (DCML) pathway

Pathway that carries fine touch, vibration, proprioception, and pressure information to the brain.

Ascending pathway

Pathway that carries sensory information from peripheral receptors to the brain.

Spinothalamic tract

Pathway that carries pain, temperature, crude touch, and pressure information to the brain.

Dermatome map

A map that shows areas of skin innervated by sensory nerves from individual spinal nerve roots.

Second-order neuron

Neuron that transmits signals from the spinal cord or brainstem to the thalamus.

Third-order neuron

Neuron that transmits signals from the thalamus to the primary somatosensory cortex.

Sensory decussation

The crossing over of sensory pathways in the caudal medulla.

First-order neuron

Neuron that carries sensory information from peripheral receptors to the spinal cord.

Sensory homunculus

The size of a body part's representation on the sensory homunculus reflects the density of sensory receptors and the level of fine sensory discrimination, not the physical size of the body part.

Anterior cerebral artery (ACA)

Blood supply distribution labeled #1.

Middle cerebral artery (MCA)

Blood supply distribution labeled #2.

Posterior cerebral artery (PCA)

Blood supply distribution labeled #3.

Broca's area

Cortical area identified by #4.

Wernicke's area

Cortical area identified by #5.

Anterior cerebral artery

Vessel indicated by #1.

Internal carotid artery

Vessel indicated by #2.

Posterior cerebral artery (PCA)

Vessel indicated by #3.

Basilar artery

Vessel indicated by #4.

Vertebral arteries

Vessel indicated by #5.

Posterior communicating arteries

Vessel indicated by #6.

Circle of Willis

The name of this structure.

Collateral circulation

The purpose/function of the Circle of Willis is to provide collateral circulation to the brain, ensuring continuous blood flow even if one part of the arterial supply is blocked or narrowed.

Superior division of the middle cerebral artery (MCA)

Branch #1.

Inferior division of the middle cerebral artery (MCA)

Branch #2.

Internal carotid artery

Artery serving the MCA and ACA distributions, identified in the illustration as #3.

Dura mater

Layer of meninges identified by #1.

Dura mater structure

Tough, dense, fibrous connective tissue. Impermeable to cerebrospinal fluid (CSF) and most substances. Provides mechanical protection and forms venous sinuses.

Arachnoid mater

Meningeal layer identified by #2.

Arachnoid mater structure

Thin, web-like membrane. Contains trabeculae that extend into the subarachnoid space. Acts as a barrier but allows CSF flow beneath it.

Pia mater

Meningeal layer identified by #3.

Pia mater structure

Very thin, delicate layer directly adherent to the brain and spinal cord surface. Highly permeable to fluids and nutrients. Follows the contours (gyri and sulci) of the brain.

Lateral ventricle

Ventricle identified by #1.

Third ventricle

Ventricle identified by #2.

Fourth ventricle

Ventricle identified by #3.

Cerebral aqueduct (Aqueduct of Sylvius)

Structure identified by #4.

Ventricular system purpose

To produce, circulate, and drain cerebrospinal fluid (CSF), which cushions and protects the brain and spinal cord.

Cerebrospinal fluid (CSF) functions

1. Protection - cushions the brain and spinal cord from trauma; 2. Buoyancy - reduces the effective weight of the brain, preventing it from compressing itself against the skull; 3. Chemical stability - Maintains a stable environment by removing waste products and distributing nutrients.

Pre-motor cortex

Gyrus represented by #3, its function is planning and coordination of movement, especially complex and learned movements.

Precentral gyrus

Gyrus represented by #2.

Postcentral gyrus

The area responsible for sensory feedback necessary for precise and coordinated movement.

Collective function of areas 2 and 3

Sensorimotor integration, controlling movement and processing sensory feedback.

Presence of areas in both hemispheres

Yes, they are present in both hemispheres.

Blood supply distribution for areas 2 and 3

Middle cerebral artery (MCA) supplies the lateral portions (face, upper limbs); anterior cerebral artery (ACA) supplies the medial portions (lower limbs).

Central sulcus

The sulcus identified by #1.

Presentral gyrus

The gyrus identified by #2.

Function of gyrus #2

Executes voluntary motor movements.

Collective function of gyri #3 & 4

Broca's area is responsible for speech production and motor planning for language.

Presence of Broca's area in both hemispheres

Yes, the precentral gyrus is present in both hemispheres; Broca's area is usually lateralized to the dominant hemisphere.

Collective name for portions labeled #1-3

Posterior cortex (includes the parietal, temporal, and occipital lobes).

Functions of the parietal lobe

Processes somatosensory information, such as touch, proprioception, and spatial awareness.

Functions of the temporal lobe

Processes auditory information, language comprehension, and is involved in memory.

Functions of the occipital lobe

Processes visual information.

Blood supply distribution for posterior cortex

Middle cerebral artery (MCA) supplies lateral aspects; posterior cerebral artery (PCA) supplies occipital lobe and medial temporal lobe.

Broca's area

Responsible for speech production and motor planning for language.

Wernicke's area

Responsible for language comprehension.

Presence of Wernicke's area in both hemispheres

No, it is primarily found in the left hemisphere.

Functions of the cerebellum

Coordinates voluntary movements, refines motor activity, and helps maintain balance and posture.

Main movement refinement functions of the cerebellum

1. Coordination of voluntary movements; 2. Motor learning and timing.

Balance functions of the cerebellum

Maintains posture and equilibrium; coordinates eye movements and balance via the flocculonodular lobe.

Cognitive functions of the cerebellum

Involvement in attention, language processing, regulating emotional responses, and plays a role in executive function and planning.