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Lina Le Period 6 Nervous - Coggle Diagram

- - - - Information gathered by sensory receptors about internal and external changes
    - - Processing and interpretation of sensory input
    - - Activation of effector organs (muscles and glands) produces a response
  - - - Integration and control center : Interprets sensory input and dictates motor output
      - Brain and spinal cord of dorsal body cavity
    - - The portion of nervous system outside CNS
      - Consists of nerves that extend from the brain and spinal cord
        
        Spinal nerves to and from spinal cord
        
        Cranial nerves to and from brain
      - Functional Divisions
        
        Sensory (afferent) division
        
        Somatic sensory fibers : convey impulses from skin, skeletal muscles, and joints to CNS
        
        Visceral sensory fibers : convey impulses from visceral organs to CNS
        
        Motor (efferent) division
        
        Transmits impulses from CNS to effector organs
        
        Muscles and glands
        
        Two divisions
        
        Somatic nervous system (voluntary)
        
        Somatic motor nerve fibers conduct impulses from CNS to skeletal muscle
        
        Conscious control of skeletal muscles
        
        Autonomic nervous system (involuntary)
        
        Consists of visceral motor nerve fibers
        
        Regulates smooth muscle. cardiac muscle, and a glands
        
        Two functional subdivisions
        
        Sympathetic
        
        Parasympathetic
- - - - Resulted in increased number of neurons
      - Evolutionary development of rostral (anterior) portion of the Central Nervous System
      - Highest level reached in human brain
    - - Diencephalon
      - Brain Stem
        
        Pons
        
        Medulla
        
        Midbrain
      - Cerebellum
      - Cerebral hemispheres
      - Gray Matter
        
        short
        
        nonmyelinated neurons
        
        cell bodies
      - White Matter
        
        myelinated axons
        
        nonmyelinated axons
      - Basic pattern found in Central Nervous System
        
        central cavity surrounded by gray matter
        
        white matter external to gray matter
      - Features and changes of the pattern
        
        Spinal cord exhibits this basic pattern
        
        pattern changes with ascent into brain stem
        
        Brain stem has additional gray matter nuclei scattered within white matter
        
        Cerebral hemispheres and cerebellum contain outer layer of gray matter called the cortex
        
        Cerebrum and cerebellum also have scattered areas of gray matter nuclei amid white matter
  - - - Autonomic nervous system (involuntary)
        
        Parasympathetic
        
        Sympathetic
      - Somatic Nervous system (voluntary)
- - - - Small cells that surround and wrap delicate neurons
      - Four main neuroglia
        
        Ependymal cells
        
        May be ciliated
        
        Cilis beat to circulate CSF
        
        Line the central cavities of the brain and spinal column
        
        Range in shape from squamous to columnar
        
        Form permeable barrier between cerebrospinal fluid (CSF) in cavities and tissue fluid bathing CNS cells
        
        Microglial cells
        
        Can transform to phagocytize microorganisms and neuronal debris
        
        Migrate toward injured neurons
        
        Small, ovoid cells with thorny processes that touch and monitor neurons
        
        Astrocytes
        
        Most abundant, versatile, and highly branched of glial cells
        
        Cling to neurons, synaptic endings, and capillaries
        
        Functions
        
        Guide migration of young neurons
        
        Control chemical environment around neurons
        
        Play role in exchanges between capillaries and neurons
        
        Respond to nerve impulses and neurotransmitters
        
        Support and brace neurons
        
        Influence neuronal functioning
        
        Participate in information processing in brain
        
        Oligodendrocytes
        
        Branched cells
        
        Processes wrap CNS nerve fibers, forming insulating myelin sheaths in thicker nerve fibers
      - Two major neuroglia seen in PNS
        
        Satellite cells
        
        surround neuron cell bodies in PNS
        
        function similar to astrocytes of CNS
        
        Schwann cells (neurolemmocytes)
        
        surround all peripheral nerve fibers and form myelin sheaths in thicker nerve fiberssimilar function as oligodendrocytes
        
        vital to regeneration of damaged peripheral nerve fibers
    - - excitable cells that transmit electrical signals
      - Neurons are structural units of nervous system
      - Large, highly specialized cells that conduct impulses
      - Special characteristics
        
        Extreme longevity (lasts a person's lifetime)
        
        Amitotic, with few exceptions
        
        High metabolic rate : requires continuous supply of oxygen and glucose
      - All have cell body and one or more processes
      - Biosynthetic center of neuron
        
        Synthesizes proteins, membranes, chemicals
        
        Rough ER (chromatophilic substance, or Nissl bodies)
      - In most, plasma membrane is part of receptive region that receives input info from other neurons
      - Most neuron cell bodies are located in CNS
        
        Nuclei : clusters of neuron cell bodies in CNS
        
        Ganglia : clusters of neuron cell bodies in PNS
      - Also called perikaryon or soma
      - Contains nucleus with nucleolus ; some contain pigments
      - Neuron processes
        
        Armlike processes that extend from cell body
        
        CNS contains both neuron cell bodies and their processes
        
        PNS contains chiefly neuron processes
        
        Tracts
        
        Bundles of neuron processes in CNS
        
        Nerves
        
        Bundles of neuron processes in PNS
        
        Two types of processes
        
        Dendrites
        
        Motor neurons can contain 100s of these short, tapering, diffusely branched processes
        
        Contain same organelles as in cell body
        
        Receptive (input) region of neuron
        
        Convey incoming messages toward cell body as graded potentials (short distance signals)
        
        In many brain areas, finer dendrites are highly specialized to collect information
        
        Dendritic spines
        
        Appendages with bulbous or spiky ends
        
        Axon
        
        Structure
        
        In some neurons, axons are short or absent ; in others, axon comprises almost entire length of cell
        
        Some axons are be over 1 meter long
        
        Long axons are called nerve fibers
        
        Axons branch profusely at their end (terminus)
        
        Can number as many as 10,000 terminal branches
        
        Distal endings are called axon terminals or terminal buttons
        
        Each neuron has one axon that starts at cone-shaped area called axon hillock
        
        Functional characteristics
        
        axon is the conducting region of neuron
        
        Generates nerve impulses and transmits them along axolemma (neuron cell membrane) to axon terminal
        
        Terminal : region that secretes neurotransmitters, which are released into extracellular space
        
        Can excite or inhibit neurons it contacts
        
        Carries on many conversations with different neurons at same time
        
        Movement occurs in towards and away from the cell body
        
        Quickly decay if cut or damaged
        
        Myelin sheath
        
        Function
        
        Protect and electrically insulate axon
        
        Increase speed of nerve impulse transmission
        
        Myelinated fibers : segmented sheath surrounds most long or large diameter axons
        
        Composed of myelin, a whitish, protein-lipid substance
        
        Nonmyelinated fibers : do not contain sheath
        
        Conduct impulses more slowly
        
        Myelination in the PNS
        
        Formed by Schwann cells
        
        wraps around axon in jelly roll fashion
        
        one cell forms one segment of myelin sheath
        
        Myelin sheath gaps
        
        gaps between adjacent Schwann cells
        
        formerly called nodes of Ranvier
        
        Nonmyelinated fibers
        
        Thin fibers not wrapped in myelin; surrounded by Schwann cells but no coiling; one cell may surround 15 different fibers
        
        Myelin sheaths in the CNS
        
        Formed by processes of oligodendrocytes, not while cells
        
        Each cell can wrap up to 60 axons at once
        
        Myelin sheath gap is present
        
        Thinnest fibers are unmyelinated, but covered by long extensions of adjacent neuroglia
        
        White matter : regions of brain and spinal cord with dense collections of myelinated fibers
        
        usually fiber tracts
        
        Gray matter : mostly neuron cell bodies and nonmyelinated fibers
- - - - Bipolar : two processes (one axon, one dendrite)
        
        Rare
        
        retina
        
        olfactory mucosa
      - Unipolar : one T-like process (two axons)
        
        Also called pseudounipolar
      - Multipolar : three or more processes (1 axon, other dendrites)
        
        Most common and major neuron type in CNS
  - - - Sensory
        
        Transmit impulses from sensory receptors toward CNS
        
        Almost all are unipolar
        
        Cell bodies are located in ganglia in PNS
      - Motor
        
        Multipolar
        
        Most cell bodies are located in CNS (except some autonomic neurons)
        
        Carry impulses from CNS to effectors
      - Interneurons
        
        Lie between motor and sensory neurons
        
        Shuttle signals through CNS pathways
        
        Also called association neurons
        
        Most are entirely within CNS
        
        99% of body's neurons are interneurons
- - - - Contain cerebrospinal fluid (CSF)
      - Protect blood vessels and enclose venous sinuses
      - Form partitions in skull
      - Cover and protect CNS
    - - Dura mater
        
        strongest meninx
      - Arachnoid mater
        
        Middle layer with spiderweb-like extensions
        
        Separated from dura mater by subdural space
        
        Subarachnoid space contains CSF and largest blood vessels of brain
      - Pis mater
        
        Delicate connective tissue that clings tightly to brain, following every convolution
        
        Contains many tiny blood vessels
  - - - Protects CNS from blows and other trauma
      - Gives buoyancy to CNS structure
        
        Reduces weight of brain by 97% by floating it so it is not crushed under its own weight
      - Nourishes brain and carries chemical signals
  - - - Simple diffusion : allows lipid-soluble substances, as well as blood gases to pass freely through cell membrane
      - Specific transport mechanisms : facilitated diffusion moves substances important to the brain such as glucose, amino acids and specific ion
    - - Chemical variations could lead to uncontrollable neuron firings
    - - Necessary to monitor chemical composition and temperature of blood
- - - - Longitudinal fissure
        
        Separates two hemispheres
      - Transverse Cerebral fissure
        
        Separates cerebrum and cerebellum
  - - - Central sulcus
        
        separates precentral gyrus of frontal lobe and postcentral gyrus of parietal lobe
      - Parieto-occipital sulcus
        
        separates occipital and parietal lobes
      - Lateral sulcus
        
        outlines temporal lobes
    - - Cerebral Cortex of gray matter superficially
        
        Site of conscious mind
        
        voluntary motor initiation
        
        communication
        
        sensory perception
        
        memory storage
        
        awareness
        
        understanding
        
        Thin (2-4 mm) superficial layer of gray matter
        
        neuron cell bodies
        
        dendrites
        
        glial cells
        
        blood vessels
        
        40% of mass of brain
        
        Four general considerations of cerebral cortex
        
        Contains three types of functional areas
        
        Sensory areas : conscious awareness of sensation
        
        Occur in parietal, insular, temporal, and occipital lobes
        
        Eight main areas
        
        Primary Somatosensory Cortex
        
        4 more items...
        
        Somatosensory Association Cortex
        
        3 more items...
        
        Visual Areas
        
        Auditory Areas
        
        Vestibular Cortex
        
        Olfactory Cortex
        
        Gustatory Cortex
        
        Visceral Sensory Area
        
        Association areas : integrate diverse information
        
        Allows us to give meaning to information received, store in memory, tie to previous experience, and decide on actions
        
        Sensations, thoughts, emotions become conscious
        
        Send outputs to multiple areas
        
        Broadly divided into three parts
        
        anterior association area
        
        posterior association area
        
        limbic association area
        
        Receive inputs from multiple sensory areas
        
        Motor areas : control voluntary movement
        
        Frontal eye field within and anterior to premotor cortex
        
        superior to Broca's area
        
        Broca's area anterior to inferior premotor area
        
        Premotor cortex anterior to precentral gyrus
        
        Primary motor cortex in precentral gyrus
        
        Located in frontal lobe
        
        Primary (somatic) motor cortex
        
        Located in precentral gyrus of frontal lobe
        
        Somatotopy : all muscles of body can be mapped to area on primary motor cortex
        
        1 more item...
        
        Broca's area
        
        Present in one hemisphere (usually the left)
        
        Motor speech area that directs muscles of speech production
        
        Active in planning speech and voluntary motor activities
        
        Premotor cortex
        
        Helps plan movements
        
        Controls learned, repetitious, or patterned motor skills
        
        Coordinates simultaneous or sequential actions
        
        Controls voluntary actions that depend of sensory feedback
        
        Each hemisphere is concerned with contralateral (opposite) side of body
        
        Lateralization (specialization) of cortical function can occur in only one hemisphere
        
        Cerebral dominance : referws to hemisphere that is dominant for language
        
        90% of humans have left-sided dominance
        
        Usually results in right-handedness
        
        In other 10%, roles of hemispheres are reversed
        
        Left hemisphere
        
        Controls language, math, and logic
        
        Right hemisphere
        
        Visual-spatial skills, intuition, emotion, and artistic and musical skills
        
        Lateralization : division of labor between hemispheres
        
        hemispheres are not identical
        
        Hemispheres communicate almost instantaneously via fiber tracts and functional integration
        
        Conscious behavior involves entire cortex in one way or another
      - White Matter internally
        
        Cerebral white matter
        
        Responsible for communication between cerebral areas, and between cortex and lower CNS
        
        Consists of myelinated fibers bundled into large tracts
        
        Second of the three basic regions of cerebral hemispheres
        
        Classified according to direction they run
        
        Association
        
        Commissural
        
        Projection fibers
      - Basal nuclei deep within white matter
        
        Each hemisphere's basal nuclei include
        
        Caudate nucleus
        
        Putamen
        
        Globus pallidus
        
        Caudate nucleus + putamen = striatum
        
        Closely associated with subthalamic nuclei (diencephalon) and substantia nigra (midbrain)
        
        Third of the three basic regions of cerebrum
        
        Functions of basal nuclei are thought to :
        
        Influence muscle movements
        
        Play role in cognition and emotion
        
        Regulate intensity or slow or stereotyped movements
        
        Filter out incorrect/ inappropriate responses
        
        Inhibit antagonist/ unnecessary movements
    - - Consists of three paired gray-matter structures
        
        Hypothalamus
        
        Forms cap over brainstem and forms inferolateral walls of third ventricle
        
        Contains many important nuclei
        
        Mammillary bodies : paired anterior nuclei that act as olfactory relay stations
        
        Infundibulum : stalk that connects to pituitary gland
        
        The main visceral control and regulating center that is vital to homeostasis
        
        Chief homeostasis controls
        
        Controls autonomic nervous system
        
        Blood pressure
        
        Rate and force of heartbeat
        
        Digestive tract motility
        
        Pupil size
        
        Initiates physical responses to emotions
        
        Part of limbic system : perceives pleasure, fear, rage, biological rhythms, and drives (sex drive)
        
        Other functions
        
        Regulates hunger and satiety in response to nutrient blood levels or hormones
        
        Regulates water balance and thirst
        
        Regulates sleep-wake cycles
        
        Suprachiasmatic nucleus of thalamus sets our biological clock
        
        Regulates body temperature
        
        Sweating
        
        Shivering
        
        Controls endocrine system functions
        
        Secretions of anterior pituitary gland
        
        Production of posterior pituitary hormones
        
        Located below Thalamus
        
        Thalamus
        
        Main thalamic function is to act as relay station for information coming into cortex
        
        Sorts, edits, and relays ascending input such as
        
        Impulses from hypothalamus for regulating emotion and visceral function
        
        Impulses from cerebellum and basal nuclei to help direct motor cortices
        
        Impulses for memory or sensory intergration
        
        Acts to mediate sensation, motor activities, cortical arousal, learning, and memory
        
        Epithalamus
        
        Most dorsal portion of diencephalon
        
        Forms root of third ventricle
        
        Contains pineal gland (body)
        
        Extends from posterior border
        
        Secretes melatonin that helps regulate sleep-wake cycle
      - All three enclose third ventricle
  - - - Medulla Oblongata
        
        Blends into spinal cord at foramen magnum
        
        Contains fourth ventricle
        
        Continuation of central canal of spinal cord
        
        Medulla and pons form ventral wall
        
        Contains choroid plexus : capillary-rich membrane that forms cerebral spinal fluid
        
        Also known as medulla
        
        Functions of the medulla oblongata functional groups
        
        Cardiovascular center
        
        Cardiac adjusts force and rate of heart contraction
        
        Vasomotor center adjusts blood vessel diameter for blood pressure regulation
        
        Respiratory centers
        
        Generate respiratory rhythm
        
        Control rate and depth of breathing (with pontine centers)
        
        Various other centers regulate
        
        Vomitting
        
        Hiccupping
        
        Swallowing
        
        Coughing
        
        Sneezing
      - Pons
        
        Located between midbrain and medulla oblongata
        
        Fourth ventricle separated pons from cerebellum
        
        Some nuclei play role in reticular formation, and some help maintain normal rhythm of breathing
      - Midbrain
        
        Cerebral peduncles : two ventral bulges that contain pyramidal motor tracts
        
        Form pillars that hold up cerebrum
        
        Cerebral aqueduct : channel running through midbrain that connects third and fourth ventricles
        
        Located between diencephalon and pons
        
        Midbrain nuclei scattered throughout white matter
        
        Corpora quadrigemina : paired dorsal protrusions
        
        Superior colliculi : visual reflex centers
        
        Inferior colliculi : auditory relay centers
        
        Substantia nigra : functionally linked to basal nuclei
  - - - Processes input from cortex, brain stem, and sensory receptors to provide precise coordinated movements of skeletal muscles
      - Plays role in thinking, language, and emotion
      - Balance and coordination
  - - - Limbic System
        
        Large part of meotional or affective brain
        
        Limbic system puts emotional responses to odors
        
        Includes parts of diencephalon and some cerebral structures that encircle brain stem
        
        Most output relayed via hypothalamus
        
        Hypothalamus plays a role in psychosomatic illnesses
        
        Fornix : fiber tract that links limbic system regions
        
        Limbic system interacts with prefrontal lobes
        
        Aloows us to react emotionally to things we consciously understand to be happening
        
        Makes us consciously aware of emotional richness in our lives
        
        Structures on medical aspects of cerebral hemispheres and diencephalon
        
        Hippocampus and amydaloid body also play a role in memory
      - Reticular Formation
        
        Extends through central core of brain
        
        Has far-flung axonal connections with hypothalamus, thalamus, cerebral cortex, cerebellum, and spinal cord
        
        Connections allow it to govern brain arousal
        
        Motor functions of reticular formation helps control coarse limb movements
        
        Reticular autonomic centers regulate visceral motor functions
        
        Vasomotor centers
        
        Cardiac center
        
        Respiratory centers
  - - - storage and retrieval of information
      - Two stages of declarative memory storage
        
        Short-term memory (STM, or working memory) : temporary holding of information
        
        limited to seven or eight pieces of information
        
        Long-term memory (LTM) : has limitless capacity
    - - Main areas
        
        Broca's area : involved with speech production
        
        Wernicke's area : involved in understanding spoken and written words
      - Corresponding areas on right side are involved with nonverbal language components
      - Language implementation system involves association cortex of left hemisphere
- - - - Somatic sensory (SS)
      - Visceral sensory (VS)
      - Visceral (automatic) motor (VM)
      - Somatic motor (SM)
    - - Encloses central canal
    - - Ventral horns : some interneurons; somatic motor neurons
      - Dorsal horns : interneurons that receive somatic and visceral sensory input
      - Lateral horns (only in thoracic and superior lumbar regions) : sympathetic neurons
  - - - Ascending
      - Descending
      - Transverse
- - - - Resting state : all gated Na+ and K+ channels are closed
        
        Only leakage channels for Na+ and K+ are open
        
        Maintains the resting membrane potential
      - Depolarization : Na+ channels open
        
        Depolarizing local current open voltage-gated Na+ channels, and Na+ rushes into cell
        
        Na+ influx causes more depolarization, which opens more Na+ channels
        
        At threshold (-55 to -50 mV), positive feedback causes opening of all Na+ channels
        
        Results in large action potential spike
        
        Membrane polarity jumps to +30mV
      - Repolarization : Na+ channels are inactivating and K+ channels open
        
        Na+ channel inactivation gates close
        
        Membrane permeability to Na+ declines to resting state
        
        AP spike stops rising
        
        Voltage-gated K+ channels
        
        K+ exits cell down its electrochemical gradient
        
        Repolarization : membrane returns to resting membrane potential
      - Hyperpolarization : some K+ channels remain open, and Na+ channels reset
        
        This causes hyperpolarization of the membrane (slight dip below resting voltage)
        
        Na+ channels also begin to reset
        
        Some K+ channels remain open, allowing excessive K+ efflux
        
        Inside of membrane becomes more negative than in resting state
- - - - Ophthalmic (V1) passes through superior orbital fissure
      - Maxillary (V2) passes through foramen rotundum
      - Mandibular (V3) passes through the foramen ovale
- - - - contain sensory (afferent) fibers from sensory neurons in dorsal root ganglia that conduct impulses from peripheral receptors
    - - contain motor (efferent) fibers from ventral horn motor neurons that innervate skeletal muscles
- - - - Acetylcholine (ACh)
        
        Released at neuromuscular junctions
        
        Also used by many neurons and some CNS neurons
        
        Synthesized from acetic acid and choline by enzyme choline acetyltransferase
        
        First identified and best understood
        
        Degraded by enzyme acetylcholineerase (AChE)
      - Biogenic amines
        
        Catecholanimes
        
        Made from amino acid tyrosine
        
        Dopamine
        
        Norepinephrine (NE)
        
        Epinephrine
        
        Indolamines
        
        Serotonin " made from the amino acid tryptophan
        
        Histamine : made from the amino acid histidine
        
        All widely used in brain: play roles in emotional behaviors and biological clock
        
        Used by some ANS motor neurons
        
        Especially NE
        
        Imbalances are associated with mental illness
      - Amino acids
        
        Amino acids make up all proteins: therefore, it is difficult to prove which are neurotransmitters
        
        Amino acids that are proven neurotransmitters
      - Peptides (neuropeptides)
        
        strings of amino acids that have diverse functions
        
        Endorphins : act as natural opiates; reduce pain perception
        
        Beta endorphin
        
        Dynorphin
        
        Enkephalins
      - Purines
        
        Monomers of nucleic acids that have an effect in both CNS and PNS
      - Gases and lipids
      - Endocannabinoids
        
        Act at same receptors as THC (active ingredient in marijuana)
    - - Classified into two groups
        
        Effects : excitatory versus inhibitory
        
        Neurotransmitter effects can be excitatory (depolarizing) and/or inhibitory (hyperpolarizing)
        
        Effect determined by receptor to which it binds
        
        Actions : direct versus indirect
        
        Direct action : neurotransmitter binds directly to and opens ion channels
        
        Indirect action : neurotransmitter acts through intracellular second messengers
- - - - shunts blood to areas that need it and adjusts heart rate, blood pressure, digestive processes
  - - - Somatic nervous system
        
        all somatic motor neurons release acetylcholine (ACh)
        
        Effect is always stimulatory
      - ANS
        
        Preganglionic fibers release ACh
        
        Postganglionic fibers release norepinephrine or ACh at effectors
        
        Effect is either stimulatory or inhibitory, depending on type of receptors
    - - Somatic nervous system : cell body is in CNS, and a single, thick myelinated group A axon extends in spinal or cranial nerves directly to skeletal muscle
      - ANS : pathway uses a tewo0neuron chain
        
        Preganglionic neuron : cell body in CNS with thin, lightly myelinated preganglionic axon extending to ganglion
        
        Postganglionic (ganglionic) neuron (outside CNS) : cell body synapses with preganglionic axon in autonomic ganglion with nonmyelinated postganglionic axon that extends to effector organ
    - - somatic nervous system innervates skeletal muscles
      - ANS innervates cardiac muscle, smooth muscle, and glands
- - - - muscle fiber or gland cell that responds to efferent impulses by contracting or secreting
    - - conducts efferent impulses from integration center to effector organ
    - - either monosynaptic or polysynaptic region within CNS
    - - transmits afferent impulses to CNS
    - - site of stimulus action
- - - - NMDA receptors are activated by long-lasting or intense pain
        
        Allow spinal cord to "learn: hyperalgesia
        
        Early pain management critical to prevent
  - - - Digits turn pale, then cyanotic
      - Treated with vasodilators
  - - - Impulse conduction slows and eventually ceases
      - Demyelinated axons increase Na+channels, causing cycles of relapse and remission
      - Turns myelin into hardened lesions called scleroses
  - - - Paraplegia : transection between T1 and L1
      - Quadriplegia : transection in cervical region
    - - Paresthesias : caused by damage to dorsal roots or sensory tracts
        
        leads to sensory function loss
      - Paralysis : caused by damage to ventral roots or ventral horn cells
        
        leads to motor function loss
        
        two types of paralysis : flaccid or spastic
    - - Symptoms : loss of ability to speak, swallow, and breathe
      - Death typically occurs within 5 years
      - Destruction of ventral horn motor neurons and fibers of pyramidal tract
      - Caused by environmental factors and genetic mutations involving RNA processing
        
        involves glutamate excitotoxicity
      - Also called Lou Gehrig's disease
      - Drug riluzole interferes with glutamate signaling : only treatment
  - - - Sacral dimple or patch of hair may hint at underlying anomaly
    - - Child may also have hydrocephalus, paralysis, and bowel and bladder dysfunction
      - If portions of spinal cord and nerve roots protrude inside sac, it is called myelomeningocele
        
        larger cysts cause neurological impairment
      - Form a saclike cyst called a meningocele
    - - U.S. incidence has dropped with recommendations for supplementation
  - - - Genetic factors play a role, but brain injuries, stroke, infections, or tumors can also
        be causes
  - - - Can compress blood vessels and crush soft nervous tissue
  - - - Concussion: temporary alteration in function
      - Contusion: permanent damage
      - Subdural or subarachnoid hemorrhage: pressure from blood may force brainstem through foramen magnum, resulting in death
      - Cerebral edema: swelling of brain associated with traumatic head injury
  - - - Also referred to as “strokes”
      - Ischemia: tissue deprived of blood supply, leading to death of brain tissue
        
        Can be caused by blockage of cerebral artery by blood clot
        
        Glutamate acts as excitotoxin, worsening condition
      - Hemiplegia (paralysis on one side) or sensory and speech deficits may result
      - Transient ischemic attacks (TIAs): temporary episodes of reversible cerebral ischemia
      - Tissue plasminogen activator (TPA) is only approved treatment for stroke
  - - - Degeneration of dopamine-releasing neurons of substantia nigra
      - Basal nuclei deprived of dopamine become overactive, resulting in tremors at rest
      - Cause unknown, but theories include mitochondrial abnormalities or protein degradation pathways
      - Treatment includes L-dopa (dopamine precursor), deep brain stimulation, gene therapy
        
        Research into stem cell transplants is promising
    - - Fatal hereditary disorder caused by accumulation of protein huntingtin in brain cells
        
        Leads to degeneration of basal nuclei and cerebral cortex
      - Initial symptoms include wild, jerky “flapping” movements
      - Later marked by mental deterioration
        
        Usually fatal within 15 years of onset
      - Treated with drugs that block dopamine effects
      - Stem cell implant research is promising
    - - Plaques of beta-amyloid peptides form in brain
      - Neurofibrillary tangles inside neurons interfere with transport mechanisms, eventually killing neuron
      - As brain cells die, brain shrinks
      - Memory loss, short attention span, disorientation, eventual language loss, irritability, moodiness, confusion, hallucinations
      - Progressive degenerative disease of brain that results in dementia
        
        Key proteins appear to be misfolded and malfunction
  - - - Severe body wasting
      - Obesity
      - Sleep disturbances
      - Dehydration
      - Emotional imbalances
  - - - Example: damage to premotor area controlling movement of fingers would still allow fingers to move, but voluntary control needed to type would be lost
    - - Would require practice, just as the initial learning process did