Neuro Structure and Function Guide

Amygdala

Almond-shaped structure that attaches to the caudate nucleus. It mediates fear and anger and assists in perception of social cues.

Brainstem

Connects the spinal cord to the cerebrum and contains multiple structures that regulate vital functions. Structures include medulla (lies at the most inferior end and contains life support centers), pons (superior to the medulla and supports respiration), midbrain (most superior segment, supports wakefulness/alertness and processing visual/auditory info)

Cerebellum

Processes proprioceptive input; coordinates and fine-tunes voluntary movements ensuring smooth, coordinated, & precise motor control; regulates tone, posture, and balance; and helps the brain learn and improve motor movements. Includes three lobes: anterior, posterior, flocculonodular.​

Fornix

Pair of arch-shaped fibers that begin in the uncus and wrap around to the mammillary bodies. It functions as a relay system for messages generated by the limbic system.

Frontal Lobe

General functions include mediation of higher cognitive functions such as planning (ideation), decision making, working memory, and regulating behavior; planning and sequencing movements (motor planning); initiation of voluntary movements of specific body parts (through the motor homunculus); personality; and control of motor movement critical for speech production. Structures include prefrontal cortex, premotor cortex, primary motor cortex, supplementary motor area, and Broca's area.

Hippocampus

Is essential for converting short-term memories into long-term memories; plays a critical role in associating memories with emotional experiences; assists us in making complex decisions by weighing potential outcomes; and creates and maintains mental maps of our environments.

Hypothalamus

A structure consisting of several nuclei that regulate visceral and endocrine functions to keep us in homeostasis

Limbic System

Group of structures that regulate emotions and help us learn safe/unsafe situations. Structures include amygdala, hippocampus, fornix. Mnemonic MOVE helps us understand its functions related to survival.

Mammillary Body

A pair of small rounded nuclei on the ventral aspect of the brain and are crucial for episodic memory, consolidating emotions, and regulating reward behaviors

Occipital Lobe

Interpretation of incoming visual information. Specific areas of interest: dorsal and ventral streams

Olfactory bulb and tract

A structure in the forebrain that contains the smell receptors, processes smell, and sends it to other brain areas for interpretation

Optic Chiasm

Cross-shaped connection between the optic nerves and carries visual information from the optic nerves to the optic tracts (decussation)

Parietal Lobe

General functions include primary integration of somatosensory inputs; primary integration of somatosensation; integration of somatosensory input with visual and auditory inputs; development of perception. Specific areas of interest: sensory homonculus, posterior parietal cortex

Pituitary gland

Regulates bodily functions such as metabolism, reproduction, and stress responses by producing/releasing hormones

Temporal lobe

General functions include audition (hearing); comprehension of language; support in the development of long-term memory. Specific area of interest: Wernicke's area

Thalamus

Constellation of paired nuclei that relay all but one sensation to cerebral cortex and is a critical structure in the motor feedback loop

Uncus

Structure likely involved in olfaction, memory, emotional processing, spatial navigation, and supporting the hypothalamus

Ventricles

Hollow spaces in the brain that contain cerebral spinal fluid (CSF). There are four ventricles.

Action Potential (AP)

Brief fluctuation in cell membrane potential caused by the rapid opening and closing of voltage gated ion channels; aka spike, nerve impulse, or discharge

Afferent

Conducting toward the CNS

Brain Vascular System

Complex network of blood vessels that support brain function. The brain's vascular system includes capillaries and arteries that supply the brain with oxygen and nutrients and sinuses that carry the waste away.

Bundle

A collection of axons that run together but do not necessarily have the same origin or destination

Capsule

A collection of axons that connect the cerebrum with the brain stem (ex. Internal capsule)

Cerebral Spinal Fluid (CSF)

Clear solution of sodium chloride and other salts that fills the ventricles and subarachnoid space. Circulates around brain and spinal cord to protect and cushion them. Also provides nourishment by transporting essential nutrients to neurons and removes waste.

Commissure

A band of nerve fibers (axons) that connect areas of the brain (ex. Corpus collosum)

Cortex

Any collection of neurons that form a thin sheet, usually at the brain's surface (ex. Cerebral cortex)

Convolutions

Collective names for gyri and sulci

Efferent

Conducting away from the CNS

Fissures

Deep groove dividing the brain into lobes and hemispheres

Ganglia

A cluster of nerve cell bodies, typically found in the PNS (ex. Dorsal root ganglia - take sensory data from periphery into CNS)

Glial cells (Neuroglia)

Cells of the nervous system that insulate, support, and nourish neurons.

Gray matter

Sits on the surface of the cerebrum and cerebellum. It appears grayish because it consists primarily of neuronal cell bodies (soma).

Gyri

Small protrusion or bump formed by the folding of the cerebral cortex

Lemniscus

A band of nerve fibers that carry sensory information from the PNS to CNS (ex. Medial lemniscus)

Meninges

3 layers or protective tissue that encase the brain and spinal cord (dura, arachnoid, pia maters)

Myelin

A lipid that is yellowish in color. It insulates nerve fibers.

Nerve

A bundle of axons in the PNS. There is only one collection of CNS axons called a nerve (the optic nerve)

Nerve cells (Neurons)

Basic units of information processing and communication in the nervous system. They carry out the brain's main functions.

Neural Propagation

The process by which nerve impulses, or action potentials, travel along neurons; aka nerve conduction

Neurotransmitter uptake/reuptake

The process of absorbing neurotransmitters from the extracellular space (synaptic cleft) in the postsynaptic neuron, without chemically modifying them

Nucleus

A clearly distinguishable mass of neurons in the CNS that share similar connections and functions. NOT the same thing as the nucleus of a cell (ex. Ventral lateral nucleus)

Resting membrane potential

The membrane potential, or membrane voltage, maintained by a cell when it is not generating action potentials (closed ion channels). Neurons have a resting potential of approximately -65mV

Substantia

A group of related neurons deep within the brain, but usually with less distinct borders than those of nuclei (ex. Substantia nigra - cell group involved in movement)

Sulci

A shallow groove in brain matter, usually found in the cerebrum

Tract

A collection of CNS axons having a common site of origin and a common destination (ex. Corticospinal tract, which originates in the cerebral cortex and ends in the spinal cord)

Vesicle

Tiny sac in the presynaptic nerve terminal that stores and releases neurotransmitters into the synaptic cleft. Vesicles fuse with the presynaptic membrane, a process called exocytosis, to allow the releasing of their neurotransmitters.

White Matter

Located beneath the gray matter, in the internal regions of the cerebrum and cerebellum. White matter consists primarily of myelinated and unmyelinated nerve fiber tracts.

Brain Plane

A slice through the body

Vertebral Column

the bones that reach from the base of the skull to the tailbone

Spinal Cord

Long, tube-like band of nerve fibers that carry signals to and from the brain

Spinal Canal

Subarachnoid space that contains the CSF that surrounds the spinal cord

Spinal Nerves

Individual nerve fibers that carry afferent and efferent messages connecting the CNS and PNS

Spinal Arteries

Carry oxygenated blood from the heart to the spinal cord

Spinal Veins

Carry deoxygenated blood from the spinal cord back to the heart

Funiculi

Columns of white matter that contain the spinal cord tracts

Upper Motor Neuron (UMN)

A first-order neuron (cell bodies) that carries motor information from the CNS to either interneurons or LMN's in the ventral horn of the spinal cord or CN nuclei

Lower Motor Neuron (LMN)

A motor neuron that carries information from the UMN in the ventral horn to the skeletal muscles in the PNS

Interneuron

Transmits impulses between two neurons

Descending Spinal Cord Tracts

The axons of UMN that are part of the CNS that carry motor information to the ventral horn of the spinal cord. They may or may not connect with interneurons.

Ventral Horn

Part of the CNS that contains cell bodies (somas) of the LMN. Delivers motor messages to the LMN. Where UMN and LMN meet in the spinal cord.

Ventral Rootlets

Are made up of the axons of the LMN in the PNS that leave the ventral horn of the spinal cord

Ventral Roots

Axon bundles of descending spinal nerves of the PNS that innervate skeletal muscles of the body

Skeletal Muscles

Highly organized tissues composed of bundles of muscle fibers that support and move the skeletal system

Hyperacusis

Low tolerance for sound, causing discomfort or pain in response to everyday noises that most would find tolerable

Diplopia

Double vision

Anosmia

Loss of smell

Nystagmus

Involuntary back and forth movements of the eye in a quick, jerky, oscillating fashion

Ptosis

Drooping of a body region

Strabismus

Deviation of the eyeball laterally (lateral strabismus/exotropia) or medially (medial strabismus/esotropia)

Dysphagia

Difficulty swallowing

Dysphonia

Difficulty projecting one’s voice audibly

Dysarthria

Difficulty articulating words clearly, slurring words

Spinal Reflex

An action performed in involuntary response to a stimulus without conscious thought. It allows sensory data to be acted on quickly.

Deep tendon reflex (aka stretch reflex, myotatic reflex, monosynaptic reflex)

An involuntary response to stretching muscle. Contributes to overall posture and tone.

Withdrawal Reflex

An involuntary spinal response to protect the body from damaging stimuli while simultaneously adjusting posture to keep balanced. Involves a sensory neuron, spinal interneuron, and motor neuron.

Sensory Receptors

Specialized cells that detect specific stimuli, such as light, sound, or heat, and act as transducers by converting these stimuli into electrical signals (action potentials) that the nervous system can process.

Dorsal (Root) Ganglia

Cluster of sensory neuron cell bodies located in the dorsal root of the spinal nerve.

Dorsal Rootlets

Are made up of the axons of the nerves who have their cell bodies in dorsal ganglia that enter the dorsal horn of the spinal cord.

Dorsal Horn

Part of the CNS that receives the sensory information from the periphery.

Ascending Spinal Cord Tracts

The axons in the CNS that carry sensory information into the brain.

Disease

A condition of the brain or body or of one of its parts that impairs normal functioning and is typically manifested by distinguishing signs and symptoms. Ex: infection, degenerative disease

Lesion

A general term to describe an area of injured or damaged tissue. A lesion can occur anywhere in/on the body, brain, organ, nerves, etc. Ex: wounds, ulcers, abscesses, sores

Spasticity

Increase in muscle tone with an associated inability to voluntarily control the muscles. Results from UMN lesions. Spasticity is velocity dependent: spasticity can be elicited by passively moving an affected limb quickly, while performing it slowly may not elicit increased muscle tone.

Flaccidity

Loss of muscle tone and paralysis resulting from denervation of a peripheral nerve. It always occurs in a LMN injury.

Hyporeflexia

Decreased or absent deep tendon reflexes. Occurs when there is a peripheral neuropathy (damage).

Unimodal Sensation

Relating to a single sensory modality

Multimodal Sensation

Relating to more than one sensory modality

Stereognosis

The ability to identify the shape and form of a three-dimensional object

Pain

Sharp, throbbing, burning, or aching sensation that signals potential tissue damage

Itch

An unpleasant or uncomfortable sensation that signals the need to scratch

Primary Motor Cortex / M1 / Precentral Gyrus

Initiates motor commands through the motor homunculus allowing conscious control over skeletal muscles of the body.

Premotor Cortex / Area 6

Involved in motor planning of all movements and initiation of motor commands to axial and proximal limb skeletal muscles.

Frontal Eye Fields

Initiation of motor commands to muscles of the eye to support voluntary saccades and smooth visual pursuit

Secondary Motor Cortex

Located on the lateral surface of the cerebral cortex at the bottom of the precentral gyrus. Functions unknown. Aka MII

Anterior Lobe of the Cerebellum

Coordinates and fine-tunes body and limb movements in real-time through comparison; helps maintain posture and regulate tone. aka paleocerebellum, spinocerebellum

Posterior Lobe of the Cerebellum

Receives input from M1 and works with the thalamus as part of a motor feedback loop to facilitate smooth execution of planned movements. Aka neocerebellum, cerebrocerebellum

Flocculonodular Lobe of the Cerebellum

Works with the vestibular nuclei to integrate vestibular information; controls balance and equilibrium reactions; coordinates head and eye movements; contributes to coordination of the motor coordination between the two sides of the body (such as in jumping jacks). aka vestibulocerebellum, archicerebellum

Caudate Nucleus

A basal ganglia structure involved in the planning and execution of automatic movements. The neurons in this structure act to inhibit certain "purposeless" movements

Putamen and Global Pallidus

Basal ganglia structures involved in stereotypic or automatic movement patterns. The neurons in these structures produce excitatory neural messages. aka lenticular nucleus

Voluntary Movements

Are purposefully initiated to accomplish a specific goal. These movements vary, can be improved with practice, and can be corrected in real-time with sensory feedback.