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Neuron
An electrically excitable (can be inhibitory too) cell that communicates with other cells via specialized connections called synapses
Human brain contains 100 billion
They are modified by experience (they learn, remember, and forget
Make up the grey matter in the brain
Have the capacity to receive information, transmit information, and adapt to environmental stimulation
Will have thousands of synapses
Proliferation Stage of Neuronal Development
The stage when the young neuron forms its axons and dendrites - prepares for migration
Nuceli
Aggregated communities of neurons that have special behavioral functions
Apoptosis
Programmed cell death - neurons that die due to neuronal pruning - helps with growth, immune surveillance, and neuroplastic development
Soma
The bulbous, non-process portion of a neuron or other brain cell type, containing the cell nucleus.
Cell body - contains RNA and DNA
Axon
Long projection fiber from the cell body that transmits nerve impulses away from the cell body to the terminal buttons (where neurotransmitters are stored and released into the synapse)
Begins to grow during the prenatal period with the anterior commissure visible at three months gestation
Myelin Sheath
Covers the axon of some neurons and helps speed neural impulses - insulates axons to facilitate neurotransmission
Makes up the brains white matter
Spinal cord and sensory motor tracts are first to myelinate
Prefrontal cortex probably not fully myelinated until young adulthood -> why teenagers are impulsive and risky
Correlated with acquisition and development of visual, motor, cognitive, and social skills
Myelination
The process by which axons become coated with myelin, a fatty substance that speeds the transmission of nerve impulses from neuron to neuron
facilitates efficient neurotransmission (i.e., sending and receiving of impulses from presynaptic neuron to the postsynaptic neuron)
White Matter
Myelinated axons - can be destroyed or damaged as a result of TBI and neurologic disease such as MS (a disease in which the immune system eats away at the myelin sheath or nerve cells
Corpus Callosum
Connects left and right hemispheres - connections between cortical and subcortical structures
Grey Matter
Unmyelinated neuron cell bodies and short, unmyelinated axons
Dendrite
The bushy, branching extensions of a neuron that receive messages and conduct impulses toward the cell body
Structure that radiates out from the cell body and receives impulses from other neurons
Growth visible at about 7 months gestation
Growth and formation of synapses is heavily dependent on environmental stimulation following birth
Node of Ranvier
A gap between successive segments of the myelin sheath where the axon membrane is exposed.
Part of axon that has no sheath so that potassium and sodium can enter into the axon
Neurotransmission
The process of transferring information from one neuron to another at a synapse
Too many neurons firing at once can cause a seizure
Neuron is sitting there with a negative charge (-.70 millivolt) and a ratio of ions factor the negative (chloride)
Outside of the neuron is more positive ions (potassium and sodium) - creates electrical gradient -> too much crowding of similar ions so they want to get inside where there is more room
Dendrites pick up stimulation, open nodes, positive ions go rushing in and the charge becomes positive (+.40 millivolt) and pops open all the nodes down to the terminal buttons which then open as well
Channels close and become more negative than originally started - slowly creep back to resting state
Action Potential
The change in electrical potential associated with the passage of an impulse along the membrane of a muscle or nerve cell
Absolute Refractory Period
When an action potential will not occur no matter how much stimulation is received by the neuron
-Need this period so that the neuron doesn't burn out, it is a measure of control
Relative Refractory Period
When stronger than normal stimulation is needed to cause an action potential - as the channels become more negative and need more positives to change
Propagation
The spread of the action potential down an axon, caused by successive changes in electrical charge along the length of the axon's membrane - when nodes open to allow chemicals in to charge the neuron
Nuclei
clusters of cell bodies in the CNS - aggregated community of neurons that are related in function
Neurons not directly connected, rather they send neurotransmitters across the synaptic gap
Aggregation
Process by which neurons mass to form major nuclei including the corpus callosum and basal ganglia
Neuroplasticity
Learning stronger connections, making room for what is important (adaptation)
Plasticity after a brain injury: neurons borrow from each other or assume new position - adults recover better than children because they already have the learned skills
Neuroglia (Glial cells)
Cells that support and protect neurons - repairs damaged neurons - insulate synapses
Make up 50% of the total volume of the CNS - will fill cavities with scar tissues caused by brain damage/lesions
Produces cerebral spinal fluid
Astrocytes
Regulate blood flow, but also transfer mitochondria to neurons, and supply the building blocks of neurotransmitters, which fuel neuronal metabolism - synchronize activity of the axon by taking up chemicals released by the axon
Astrocytoma: giant tumor of astrocytes that are overproduced because of a lack of apoptosis
Microglia
Remove waste material and other microorganisms that could prove harmful to the neuron
Oligodendrocytes (Brain) and Schwann Cells (Spinal)
Build the myelin sheath that surrounds the axon of some neurons
Radial Glia
Guide the migration of neurons and the growth of their axons and dendrites during embryonic development
If the radial glia don't work -> abnormality in neural migration (i.e., dyslexia)
Brain Development
Neural tube forms at 25 days gestation - when it doesn't close, spina bifida occurs
At 40 weeks gestation: the spinal cord, brain stem, and a substantial amount of forebrain (cerebral cortex and some subcortical structures like the thalamus) develop
Birth-First Year: Cerebellum's maximum growth rate
3-33: Myelination finishes at 23-24 years of age
Cell Development
Nerve cells form via mitosis in the ventricular lining of the brain
Fastest rate of brain growth occurs prenatally when 250,000 brain cells are formed each minute of mitosis
Neuronal Migration
Consists of neurons being guided by the radial fibers of glial cells to the proper neuroanatomical destination
During the 5th month of fetal development - migration process is rapid as several layers of the cerebral cortex are visible
Nerve Growth Factor
Chemical that helps neurons figure out where to go
Abnormalities in Neuronal Migration
Lissencephaly - "smooth brain" - when brain fails to form sulci and gyri - the brain is equivalent to a 12-week embryo
Heterotopia - a neurodevelopmental disorder that is characterized by displaced pockets of grey matter (neurons) that appear in the ventricular walls or white matter due to aborted neural migration (seizures may result)
Brain Derived Neurotrophic Factor (BDNF)
A protein in the nervous system that promotes survival, growth, and the formation of new synapses - guides the axon
One area that an infant forms (myelinates) very early is lips to nurse
Stimulation may increase BDNF
Luria's Model of Brain Development
A proposed central theory that states that human development is a complex process that must be framed within social, cultural, and historical contexts - a model for cognitive psychophysiological research. It may be used to predict brain processing patterns both for constructive tasks of various levels of complexity and for high and low performance on these tasks.
Stage 1 of Luria's Model
Pre-post-birth - basic arousal systems and attention
Stage 2 of Luria's Model
Pre-post-birth - basic sensory and motor areas (ex. sucking)
Stage 3 of Luria's Model
Birth-4 years - refinement of stages 1 and 2, including smoothing out motor movements and development secondary auditory and visual skills
Stage 4 of Luria's Model
5-8 years - development of posterior areas of the brain - linking perception with academic skills for example
Stage 5 of Luria's Model
9 years and on - development of anterior (frontal) parts of the brain - planning a response to sensory input processed by the posterior regions of the brain
Luria's Model of Brain Functioning
Describes three functional units of the brain:
1. The unit for regulating tone and waking and mental states (Arousal)
2. The unit for receiving, analyzing, and storing information (Sensory)
3. The unit for programming, regulation, and verification of activity (Motor)
Each lobe has three functional zones:
Frontal lobe
-Primary zone: motor strip (basic, individual movements)
-Secondary zone: premotor (selects and directs more complex coordinated movements)
-Tertiary zone: prefrontal (executive functions)
Temporal Lobe
-Primary zone: primary auditory cortex (hearing)
Parietal lobe
-Primary zone: somatosensory cortex/strip
Occipital lobe
-Primary zone: pure vision
The secondary and tertiary zones of the temporal, parietal, and occipital lobes are not clearly defined
-temporo-parieto-occipital association zone; where intermodal sensory integration takes place (vision, touch, body awareness, and spatial organization)
Arousal Unit
Primary function: to make sure the CNS reaches and maintains sufficient level of arousal
Involves deep cortical structures of brain and brain stem - Reticular Activating System)
Sensory Input Unit
Primary function: process incoming information from the environment
Consists of occipital, temporal, and parietal lobes
Motor Output Unit
Primary function: process and interprets information from the sensory input unit to select, organize, and plan actions/responses
Frontal lobes
Maureen Dennis' Model of Brain Damage/Outcome
First Factor: Biological Risk
- severity of a neurological disorder - the severity of the injury significantly decreases the outcomes
Second Factor: Age and Development at time of injury or disorder
-Damage during infancy will affect emerging skills by delaying their onset or disrupting the sequential order of the arrival of a given skill
-Damage during childhood will affect the rate of skill development, the strategy to employ the skill, or the competent use of the skill
-Damage after the skill has bee established affects the control and long-term maintenance of the skill
Third Factor: Time since injury or onset
-time is not synonymous with recovery - functioning can sometimes worsen over time
-Improvement occurs in the first 12 months
Fourth Factor: Reserve or variables associated that will buffer or exacerbate deficits
-pre-cognitive and academic abilities, emotional status, and personality/temperament can provide a better understanding of post-injury functioning
Superior/Dorsal
Top of brain
Inferior/Ventral
Bottom of brain
Anterior/Rostral
Front view of brain
Posterior/Caudal
Back of brain
Medial/Mesial
Toward the midline/middle of the brain
Lateral/Sagittal
Side view of the brain
Coronal
Brain cut in half and the front view of it
Axial
Brain cut in half horizontally and looking at it
Meninges
Three protective membranes that surround the brain and spinal cord; Dura, Arachnoid, and Pia Mater
Dura Mater
Outermost layer of the meninges surrounding the brain and spinal cord - right under the skull
Arachnoid Mater
Weblike middle layer of the three meninges
CSF is located in the arachnoid space and cushions the brain from sudden and forceful movements
Pia Mater
Thin, delicate inner membrane of the meninges - right above the brain
Meningitis
Inflammation of the meninges
Viral: Can use antibiotics to treat
Bacterial: Can be treated at first, but needs to be caught early or will cause cognitive/sensory impairment or death
Cerebral Cortex
The intricate fabric of interconnected neural cells covering the cerebral hemispheres; the body's ultimate control and information-processing center.
Outer region of the cerebrum, containing sheets of nerve cells; gray matter of the brain
Gyri
Convolutions (hills) of the cerebral cortex
Sulci
Shallow valleys or grooves that separate gyri from each other
Longitudinal Fissure
Deep sulci that separates both hemispheres
Central Sulcus
Separates the frontal and parietal lobes
Sylvian Fissure/Lateral Sulcus
A deep fissure that demarcates the temporal lobe - separates the frontal and temporal lobes
Frontal Lobes
the portion of the cerebral cortex lying just behind the forehead; involved in speaking and muscle movements and in making plans and judgments - output lobes - where you decide what to do with input data
Precentral Gyrus
Located in the frontal lobes - the primary motor cortex is here
Primary Motor Cortex
The section of the frontal lobe responsible for voluntary movement - located in the pre central gyrus - controls muscles
Premotor Cortex
The region controlling learned motor skills - Area of the frontal cortex, active during the planning of a movement - directs more complex, coordinated movements, fluid movements - selects movements to be executed
Broca's Area
Controls language expression and speech production - an area of the frontal lobe, in the left hemisphere, that directs the muscle movements involved in speech - Within the premotor cortex
Supplementary Motor Cortex
Area of the frontal cortex; active during preparation of a rapid sequence of movements - planning an organizing rapid sequences - motor inhibition
Prefrontal Cortex
Part of frontal lobe responsible for thinking, planning, and language - executive functioning and consists of dorsolateral, medial, and orbitofrontal
-§ Receives information via projections from multiple cortical and subcortical regions including the temporal, parietal, and occipital association zones as well as the thalamus and limbic systems. This permits complex, integrative functions
Parietal Lobe
Portion of the cerebral cortex lying at the top of the head and toward the rear; receives sensory input for touch and body position - separated from the frontal lobe by the central sulcus
Postcentral Gyrus
Lateral part of parietal lobe - home of the primary somatosensory cortex
Primary Somatosensory Cortex
Area of the parietal lobe where messages from the sense receptors are registered - The region of the anterior parietal lobe whose primary input is from the somatosensory system - located on the post central gyrus
Occipital Lobe
A region of the cerebral cortex at the rear that processes visual information
Primary Visual Cortex
The region of the posterior occipital lobe whose primary input is from the visual system
Temporal Lobe
A region of the cerebral cortex on the side by the ears responsible for hearing and language - the sylvian fissure/lateral sulci separates the temporal from the frontal and parietal lobes
Primary Auditory Cortex
The region of the superior temporal lobe whose primary input is from the auditory system
Wernicke's Area
controls language reception and comprehension - a brain area involved in language comprehension and expression; in the left temporal lobe in the posterior region of the superior temporal gyrus
Arcuate Fasciculus
Nerve projections that connect the temporal and frontal lobes allowing Broca's area and Wernicke's Area to communicate
Hippocampus
A neural center located in the limbic system that helps process explicit memories for storage - buried deep within the medial region of the temporal lobes
Amygdala
A limbic system structure involved in memory and emotion, particularly fear and aggression - buried deep within the medial region of the temporal lobes
Sits right on top of hippocampus because evolutionary we should remember what is dangerous and what we fear
INTERhemispheric Fissure/Connection
Large bundles of nerve fibers (about 300 million) that allow rapid communication between the two hemispheres
Anterior Commissure
A white matter tract (a bundle of axons) connecting the two temporal lobes of the cerebral hemispheres across the midline, and placed in front of the columns of the fornix.
Corpus Callosum
A large bundle of more than 200 million myelinated nerve fibers that connect the two brain hemispheres, permitting communication between the right and left sides of the brain.
INTRAhemispheric Connection
Consists of association fibers that allow different cortical regions within a hemisphere to communicate with each other
Each gyrus is connected by short association fibers
Longer fibers connect lobes to each other
Thalamus
The brain's sensory switchboard, located on top of the brainstem; it directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla
Consists of several nuclei tracts that each relay specific sensory information to the cortex - most sensory input comes in through the thalamus and then onto the cortex it needs to be projected to - deficits in certain areas without lesions on the brain that connect to those areas could be damage to the projecting area of the thalamus
Hypothalamus
A neural structure lying below the thalamus (anterior/in front of and inferior/below); it directs several maintenance activities (eating, drinking, body temperature), helps govern the endocrine system via the pituitary gland, and is linked to emotion and reward.
Has connections (nerve fibers/axons) to the autonomic nervous system, limbic system, midbrain, and forebrain
Basal Ganglia
Masses of grey matter (caudate nucleus) that provide connections between cortical and subcortical structures - damage causes problems in controlling speech, movement, and posture
Located lateral to the thalamus
Involved with the initiation and inhibition of several functions including motor functioning and the inhibition of emotional responses via connections to the prefrontal cortex
Also crucial to procedural memory and initiating the motor movements involved in expressive language
Caudate Nucleus
One of the major nuclei that make up the basal ganglia - implicated in Parkinson's disease and Huntington's Disease - functions not only in planning the execution of movement, but also in learning, memory, reward, motivation, emotion, and romantic interaction
Globus Pallidus
Component of the basal ganglia that connects to the thalamus which relays information to the motor areas and the prefrontal cortex - involved in motor modulation - control conscious and proprioceptive movements.
Putamen
Large subcortical structure, a part of the basal ganglia, that is involved in movement regulation - It is involved in a very complex feedback loop that prepares and aids in movement of the limbs. It is closely intertwined with the caudate nucleus, nucleus accumbens, and globus pallidus, which are together known as the corpus striatum.
Limbic System
Located within the cortical and subcortical regions - functions to facilitate memory storage and retrieval, establish emotional states, and link the conscious, intellectual functions of the cerebral cortex with the unconscious, autonomic functions of the brain stem.
Has numerous connections through the brain regions
Consists of the hippocampus, cingulate gyrus, amygdala, and hypothalamus
Cingulate Gyrus
A component of the limbic system; it is involved in processing emotions and behavior regulation. It also helps to regulate autonomic motor function.
Ventricles
Naturally occurring cavities in the brain that produce, store, and circulate cerebrospinal fluid
Lateral Ventricles
The two largest ventricles of the brain (located in the forebrain) and contain cerebrospinal fluid (CSF). Each cerebral hemisphere contains a lateral ventricle, known as the left or right ventricle, respectively
contain cerebrospinal fluid, a clear, watery fluid that provides cushioning for the brain while also helping to circulate nutrients and remove waste
Third Ventricle
One of the four connected ventricles of the ventricular system within the mammalian brain. It is a slit-like cavity formed in the diencephalon between the two thalami, in the midline between the right and left lateral ventricles, and is filled with cerebrospinal fluid (CSF).
Main function is to produce, secrete, and convey cerebrospinal fluid.
Fourth Ventricle
The most inferiorly located ventricle (located in the brain stem), draining directly into the central canal of the spinal cord. Superiorly, it connects to the third ventricle through a thin canal called the cerebral aqueduct of Sylvius
The main function of this ventricle is to protect the human brain from trauma (via a cushioning effect) and to help form the central canal, which runs the length of the spinal cord.
Cerebral Aqueduct
Connects the 3rd and 4th ventricles; allows cerebrospinal fluid to pass between them. - if it gets blocked it can cause brain damage
Hydrocephalus: CSF accumulates in the brain
Midbrain
A small part of the brain above the pons that integrates sensory information and relays it upward - generally beneath the limbic system and on top of the brain stem
Superior Colliculus
Receives visual sensory input - visual processing
Inferior Colliculus
A midbrain nucleus in the auditory pathway - auditory processing