Neuro Exam 3

Vestibular System

A sensory system that maintains balance, posture, and spatial orientation.

Semicircular Canals

Three canals (anterior, posterior, lateral) in the inner ear that detect rotational movements.

Otolith Organs

Consist of the utricle and saccule that detect linear movements and gravitational forces.

Endolymph

Fluid found within the membranous labyrinth of the inner ear, essential for detecting motion.

Otoliths

Calcium carbonate crystals that rest on top of the gelatinous layer in the otolith organs.

Hair Cells

Sensory cells in the inner ear that transduce mechanical stimuli into neural signals.

Euler Angles

Angles used to describe the orientation of objects, specifically yaw, pitch, and roll.

Kinocilium

The single long cilium in hair cells that acts as a reference point for directional movement.

Cupula

A gelatinous diaphragm in the ampulla of the semicircular canals that is displaced by endolymph movement.

Striola

The reversal region in the utricle where hair cell polarity is organized.

Oculomotor Nucleus

Nucleus in the brain that coordinates eye movement and is connected to vestibular signals.

Bithermal Caloric Test

A test used to assess vestibuloocular reflexes by introducing cold or warm stimuli into the ear.

Vestibular Nuclei

Groups of neurons in the brain stem that process inputs from the vestibular system.

Multisensory Cortex

Regions that integrate information from multiple sensory modalities to create a comprehensive understanding of the environment.

Nystagmus

Involuntary eye movements often triggered by vestibular stimulation.

Bilateral Symmetry

The arrangement where paired structures (like semicircular canals) are similar on both sides of the body.

Perilymph

Fluid that fills the space between the bony labyrinth and membranous labyrinth in the inner ear.

Vestibulospinal Tracts

Pathways that relay vestibular information to the spinal cord for motor control.

Equivalent Acceleration

A term referring to the linear acceleration that produces similar effects on the otolithic membrane as gravitational forces.

Ambiguous Information

The phenomenon where the postural system cannot distinguish between tilt and linear movements.

Reflexes

Rapid, automatic, and involuntary movements; stereotyped responses that occur the same way each time.

Rhythmic motor patterns

Movements initiated and terminated voluntarily but maintained through reflex mechanisms, like walking or chewing.

Voluntary movements

Purposeful and learned movements that improve with practice, such as writing or dancing.

Upper motor neurons

Located in higher motor centers like the cortex; they influence lower motor neuron circuits.

Lower motor neurons

Found in the brainstem and spinal cord; directly control skeletal muscles and regulated by local circuits.

Cerebellum

A brain structure that contributes essential and distinct roles to motor control by coordinating voluntary movements.

Basal ganglia

A group of nuclei in the brain associated with the control of voluntary motor movements, procedural learning, and routine behaviors.

Corticospinal tract

Pathway from the motor cortex to the spinal cord, crucial for voluntary motor control.

Reticulospinal tract

Regulates muscle tone and coordinates voluntary movements, adjusting muscle activity for balance.

Golgi tendon organs

Sensory receptors located at the junction of muscle and tendon that regulate muscle tension through feedback.

Muscle spindles

Sensory receptors arranged parallel to muscle fibers that detect changes in muscle length and the rate of that change.

Size principle of motor unit recruitment

Smaller motor neurons are activated before larger ones in response to increasing force demands.

Crossed extension reflex

A spinal reflex that causes the opposite limb to extend when one limb is flexed, providing balance.

Stretch reflex

A negative feedback mechanism that regulates muscle length by triggering contraction in response to stretch.

Presynaptic inhibition

Inhibition of neurotransmitter release from sensory axon terminals, allowing selective modulation of sensory input.

Renshaw cells

Interneurons that provide recurrent inhibition of motor neurons to stabilize firing rates.

Gamma motor neurons

Neurons that adjust the sensitivity of muscle spindles during muscle contraction.

Neural circuitry

Interconnected neurons that work together to control specific functions, such as locomotion or reflexes.

Basal Ganglia

A group of subcortical nuclei involved in the modulation and coordination of movement.

Striatum

Part of the basal ganglia that includes the caudate and putamen, responsible for receiving movement-related signals.

Globus Pallidus

A structure in the basal ganglia that plays a key role in regulating voluntary movement via its internal and external segments.

Substantia Nigra

A component of the basal ganglia, critical for movement regulation and affected in Parkinson's disease.

Dopaminergic Input

Neurotransmitter signals from dopaminergic neurons, crucial for the proper functioning of basal ganglia pathways.

Direct Pathway

Pathway in the basal ganglia that facilitates movement by inhibiting the globus pallidus, leading to increased excitation of the motor cortex.

Indirect Pathway

Pathway in the basal ganglia that inhibits movement by activating the globus pallidus external segment, which suppresses motor activity.

Parkinson’s Disease

A neurodegenerative disorder characterized by dopamine neuron loss in the substantia nigra, leading to movement impairments.

Huntington’s Disease

A genetic disorder resulting in the degeneration of basal ganglia, causing uncontrolled movements and cognitive decline.

Tourette’s Syndrome

A neurological disorder characterized by repetitive, involuntary movements and vocalizations known as tics.

Rheumatic Fever

An autoimmune response to a Streptococcus infection, causing inflammation in several body systems including the basal ganglia.

Wilson’s Disease

A genetic disorder resulting in copper accumulation in the body, particularly affecting the liver and brain.

Motor Learning

The process of improving and automating movements through practice, aided by the basal ganglia.

Cognitive Roles of Basal Ganglia

Functions related to decision making, learning, and reward processing, aside from movement.

Neural Plasticity

The ability of neural networks in the brain to change through growth and reorganization.

Cerebellum

Part of the brain responsible for coordination, balance, motor learning, and cognitive functions.

Dysmetria

A condition in which the movement trajectory is inaccurate, often seen in cerebellar patients.

Decomposition of movement

Movement is performed in a series of discrete, separate motions, rather than as a smooth, fluid action.

Cerebellar Ataxia

A lack of voluntary coordination of muscle movements, often caused by cerebellar damage.

Proprioception

The sense of body position and movement; impaired in cerebellar damage during active but not passive movement.

Cerebrocerebellum

The part of the cerebellum involved in planning and fine control of voluntary movements.

Spinocerebellum

Region of the cerebellum that receives sensory information, regulating posture and movement.

Vestibulocerebellum

Part of the cerebellum that maintains balance and controls eye movements.

Input Pathways

Paths through which sensory information is received by the cerebellum, including from the spinal cord and various brain regions.

Output Pathways

Paths through which signals are sent from the cerebellum to influence motor actions and coordination.

Learning in the cerebellum

Adaptive changes at synapses that refine motor responses based on experience, including classical conditioning and motor adaptation.

Mossy fibers

Fibers that carry sensory information to the cerebellum and excite granule cells.

Climbing fibers

Fibers originating from the inferior olivary nucleus that provide direct excitatory input to Purkinje cells.

Glomerulus (cerebellar)

A synaptic complex formed in the cerebellum involving mossy fibers and granule cells, integrating sensory input.

Plasticity

The ability of the brain to change and adapt as a result of experience, crucial for learning and memory.

Classical Conditioning

A learning process in which a conditioned stimulus is paired with an unconditioned stimulus to elicit a conditioned response.

Vestibular System Diagram

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Utricle Diagram

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Muscle Fiber Diagram

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Intrafusal and Extrafusal Fibers

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Golgi Tendon Organ Anatomy

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Golgi Tendon Organ Reflex

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Alpha-Gamma Coactivation

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Big Diagram

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Knee-Jerk Reflex Diagram

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Crossed Extension Reflex Diagram

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Big vs. Small Neurons

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Muscle Neurons Circuit (Extensor Muscle Contracted)

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Muscle Neurons Circuit (Flexor Muscle Contracted)

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Basal Ganglia Direct Pathway

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Basal Ganglia Indirect Pathway

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Nigrostriatal Pathway Modulation of Direct Pathway

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Nigrostriatal Pathway Modulation of Indirect Pathway

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D1r Membrane

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D2r Membrane

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Cerebellum Overall Anatomy

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Cerebellum Lobe Anatomy

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Cerebellum Neural Sharpening

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Dentothalmic / Dento-Rubro-Thalamic Pathway

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Interposed-Rubriospinal / Interposed-Thalamic-Cortical Pathway

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Fastigal-Reticular / Fastigal-Vestibular / Fastigal-Thalamic Pathways

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Visual and Vestibular Inputs

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