Biological Bases of Behavior

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