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Nervous System - Coggle Diagram

- - - - Repolarization: Na+ channels are inactivation & K+ channels open
        
        Repolarization: Membrane returns to resting membrane potential
        
        membrane permeability to Na+ declines to resting state, Ap spike stops rising
        
        voltage gated K+ channels open, K+ exits cell down its electrochemical gradient
      - Hyperpolarization: Some K+ channels remain open, & Na+ channels remain open, allowing excessive K+ efflux
        
        inside membrane becomes more negative than in resting state
        
        causes hyperpolarization of membrane and Na+ channels begin to rest when K+ channels remain open
        
        resets electrical conditions not ionic conditions
        
        after repolarization, Na+/K+ pumps thousands of them in an axon restore ionic conditions
      - Depolarization: Na+ channels open
        
        Depolarization local currents open voltage gated Na+ channels & Na+ rushes into cell
        
        Na+ influx causes more depolarization which open more Na+ channel
        
        At thereshold (-55 to -50 mv) positive feedback causes opening of all Na+ channels, results in large AP spike
        
        membrane polarity jumps to +30 mV
      - Reesting state: ALl gated Na+ & K+ channels are closed
        
        only leakage channels for NA+ & K+ are open
        
        maintains the resting membrane potential
- - - - Released at neuromuscular junctions
      - Synthesized from acetic & choline by enzyme choline acetyltransferase
      - 1st identified & best understood
      - Degraded by enzyme acetylcholine sterase (AchE)
    - - makeup all proteins: difficult to prove which are neurotransmitters
      - Amino acids are proven neurotransmitter
    - - Indolamines
        
        serotonin: Made from amino acid tryptophan
        
        Histamine: Made from amino acid histidine
        
        Imbalances are associated w/ mental illness
        
        Widely used in brain: Play roles in emotional behaviors & biological clock, used by some ANS motor neurons especially NE
      - atecholamines
        
        dopamine, norepinephrine (NE) & epinephrine made from the amino acid tyrosine
    - - strong of amino acids have divesity
      - Endorphines: Beta endorphine, dynorphin & enhephatin act as natural opiates, reduce pain perception
    - - gases & lipids
      - Endocamabinoids: Act at samereceptors as TLTC (active ingredient in marijuana)
  - - - Effects: Excitatory versus inhibitory
        
        Neurotransmitter effects can be excitatory (depolarizing) &/or inhibiroty (hyperpolarizing)
        
        Effect determined by receptors to which it binds
      - Actions: Direct versus indirect
        
        Direct action: neurotransmittter binds directly to & open ions channels
        
        Indirect action: Neurotransmitter acts through intracellular second messenger
- - - - hypothalamus
        
        located below thalamus
        
        inferolateral walls of 3rd ventricle, contains many important nuclei such as, mamilary body, and infudibulum
        
        the main visceral control regulating center
        
        regulated body temperature, regulates water balance and thirst
      - epithalamus
        
        Most dorsal, forms roof of 3rd ventricle, contains pineal gland, secreted melatonin that helps regulate (sleep-wake cycle)
      - thalamus
        
        main thalamus function, acts as relay station for infor coming into cortex
        
        sorts, edits, and relays ascending input such as impulses
  - - - located between midbrain & medulla oblongata
      - 4th ventricle separates pons from cerebellum
      - Reticuluar formation & some help maintain normal rhythm of breathing
    - - AKA medulla: Blends into spinal cord at formen magnum
      - contains 4th ventricle- chroid plexus: capillary-rich membrane that forms cerebral spinal fluid
      - Functions
        
        cardiovascular center: cardiac center adjusts force & rate of the heart
        
        contraction: casomtor center adjusts blood vessel diameter for blood pressure regulation
        
        Respiratory centers: Generate respirtatory rhythm
        
        control rate & dept of breathing w/ pontine centers
    - - located between diencephalon pons
      - cerebral peduncles: 2 ventral bulges that contain pyramidal motor tracts
        
        form pillars that hold up cerebrun
      - cerebral aqueduct: channel running through midbrain that connects 3rd & 4th ventricles
      - midbrain nuclei scattered through out white matter include
        
        Corpora quadrigemina: Paired dorsal protusions
        
        substantia nigra: functionally linked to basal nuclei
        
        parkinson's disease
  - - - central suluc separates frontal and parietal lobe
      - Precentral gyru: Of frontal lobe & postcentral of parietal lobe
      - Parietal-occipia=tal sulcus: Separates occipital & Parietal lobes
      - Lateral sulcus: Outlines temporal lobes ( from parietal & frontal)
    - - White matter internally
      - Basal nuclei deep within white matter
      - cerebral cortex: Gray matter superficially (sensory perception
        
        Cerebral cortex is 40% of the brain's mas
        
        Each hemisphere is concerned w/ contralateral side of body
        
        Lateralization of cortical function can occur in only 1 hemishpere
        
        Conscious behavior involved entire cotrex in 1 way or another
        
        1.contains 3 type of functional areas
        
        association areas: integrate diverse information
        
        conscious awareness of sensarion
        
        motor areas: control voluntary movement
  - - - processes input from cortex brain stem, & sensory receptors to provide, precise coordinated movements of skeletal muscles
      - plays role in thinking, language & emotion
      - Balance & coordination
  - - - lateral ventricle: large c shaped separated by membranous interventricle connected to 3rd ventricle
      - 3rd: lies in diencephalon, connected to 4th ventricle via cerebral aqueduct
      - 4th: lies in hinbrain continuous w/ central canal of spinal cord
      - 3rd opening connect 4th ventricle to subrachnoid space that surrounds the brain
  - - - Storage & retrieval of information
      - 2 stages of declarative memory storage
        
        short-term memory (STM, or working memory): temporary holding of information
        
        long-term memory (LTM) has limitless capacity
    - - Implement system involves association cortex of left involves association cortes of left hemisphers
      - broca area: invovled in speech production
      - wernicken's area: Involved in understanding spoken & written words
      - corresponding areas on right side are involved w/ nonverbal language components
- - - - Microglial cells
        
        small oviod cells with throny processes that touch & monitor neurons
        
        migrate toward injured neurons
        
        can transform to phagocytize migroorganisms & neuronal debris
      - Ependymal cells
        
        Range in shae from squamous to columnar
        
        May be ciliated
        
        cilia beat to cavities of brain & spnal column
        
        Line central cavities of brain and spinal cord
        
        Form permeable barrier between cerebrospinal fluid (CSF) in cavities & tissue fluid bathing CNS cells
      - Astrocytes
        
        Most abundant, versatile, & highly branched of gial cells
        
        Cling to neurons, synaptic endings & capilaries
        
        Functions include:
        
        Control chemical enviornment around neurons
        
        Guide migration of young neurons
        
        play role in exchanges between capilaries & neurons
        
        respond to nerve impulses & neurotransmitters
        
        Dupport & brace neurons
        
        influences neuronal functioning
        
        participate in information processing in brain
      - Oligodendrocytes
        
        Branched cells
        
        processes wrap CNS nerve fibers forming insulating myelin sheaths in thicker nerve fibers
    - - Satelite cells: surrond neuron cell bodies in PNS
        
        function similar to astrocytes of CNS
      - Schwann cells (neurolemmocytes)
        
        Surround all peripheral nerve fibers & form myelinat
        
        Vital to regeneration of damaged peripheral nerve fibers
  - - - extreme longetivity (lasts a person lifetime), Amitotic, with few exceptions
    - - Also perikayan or soma
      - Biosythetic center of neuron
        
        Synthesizes proteins, membranes, chemicals
        
        Rough Tr ( Chromatopic substances, or Nissl bodies)
        
        Contains nucleu w/ nucleolous; some contain pigments
        
        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
  - - - Dendrities
        
        Motor neurons can contain 100s of these short, tapering, diffusely branch processes, contain same organelles as in cell body
        
        receptive (input) region of neuron, convey incoming messages toward cell body as graded potentials
        
        Finer dendrities are highly specialized in collect info in many brain areas
        
        contains dendritic spines appendages w/ bulbous ends
      - Axons
        
        The axon: structure
        
        each neuron has 1 axon that starts at cone-shaped area called axon hillock, in some neurons, axons are short or absent; in other, axon comprises almost entire length of cell
        
        long axons are called nerve fibers
        
        axons branch profusely at their end (terminus)
        
        Axon: Axon functional characteristic
        
        conducts region of neuron
        
        generates nerve impulses & transmits them along axolemma (neuron cell) membranes to axon terminal
        
        terminal: Region that secretes neurotransmitters, which are release into extracellular space
        
        carries on many converstations w/ different neurons at same time
    - - protect & electrically insulate axon
      - Nonmyelinated fibers: do not contain sheath
        
        conduct impulses more slowly
      - myelinate fibers: Segmented sheath surrounds most long or large-diameter axon
      - Myelination in PNS: Formed by schwann cells: wraps around axon in jelly roll fashion, 1 cell forms 1 segment of myelin sheath
        
        myeline sheath geaps: gaps between adjacent schwann cells, formerly called nodes of raniver
        
        1ǹonmyelinated fibers: thins fibers not wrapped in myelin; surounded by schwann cells but no coiling; 1 cell may surround 15 different fibers
      - Myelin sheaths in CNS: Formed by processes of oligodendrocytes, each cell can wrap up to 60 axons at once
        
        myelin sheath gap is present
        
        white matter: regions of brain & spinal cord w/ dense collections of myelinated fibers usually fiber tracts
        
        gray matter: mostly neuron cell bodies & nonmyelinated fibers
  - - - Unipolar: 1 T-like process (C2 axons), also called pseudounipolar
      - Bipolar: 2 processes (1 axon, 1 dendrite) rare
      - Multipolar: 3 or more processes ( 1 axon, others dendrites), most common & major neuron type in CNS
    - - 3 types of neurons grouped by direction in which nerve impulses travel relative to CNS
        
        Sensory: transmitt impulses from sensory receptores toward CNS, almost all are unipolar
        
        Motor: Carry impulses from CNS to effectores
        
        multipolar
        
        most cell bodies are located in (CNS), except some autonomic neurons
        
        Interneurons: Also called association neurons, lie between motor & sensroy neurons
        
        shuttle signals through CNS pathways
        
        most entirely within CNS
        
        99% of bodyś nurons are internurons
- - - - processing & interpretation of sensory output
    - - information gathered, by sensroy receptors about internal and external changes
    - - activation of effector organs (muscles & glands) produces a response
  - - - Integration & control center interprets sensory input & dictates motor output
      - Brain & Spinal cord of dorsal body cavity
    - - Consists mainly of nerves that extend from brain spinal cord
        
        Cranial nerves to & from brain
        
        spinal nerves to & from spinal cord
      - Portion of Nervous Syste, outside of CNS
- - - - can be caused by blockage of cerebral artery by blood clot
  - - - progressive degenerative disease of brain that results in dementia
        
        key proteins apppear to be misfolded & malfunction
      - memory loss, short attention span, disorientation, eventual language loss, irritability, moodiness, confusion, hallucinations
      - plaques of beta-amyloid peptides form in brain
      - Neurofibrillary tangles inside neurons interfere w/transport mechanisms, eventually killing neurons
        
        As brain cells die, brain shrinks
      - Brains activity decreases by this
    - - Degeneration of dopamine-releasing neurons of substantia migra
      - Basal nuclei seprived of dopamine become overactive, resulting in tremors at rest
        
        cause unknown, but theories include mitochondria abnormalitties or protein degradation pathways
      - treatment includes
        
        L-dopa (dopamine, precursor), deep brain simulation, gene therapy
    - - Fatal hereditary disorder caused by accumulation of proetein huntingtin in brain cells
        
        leads to degeneration of basal nuclei & cerebral ortex
      - symptoms: wild, jerky, flapping movements
      - Fatal within 15 years of onset
      - treated w/ drugs that block dopamine effects
  - - - subdural or subarachoid
  - - - simple test can include knww-jerk reflex w/ hammer tapped against quadriceps tendon
      - Adnormal responses may indicate intracranial nemorrhage, multiple sclerosis or hydrocephalus
    - - radioactive tracers help visualize specific areas
    - - ultrasound can be used to evaluate blood flow through arteries feeding the brain
- - - - strongest meninx
    - - separatd from dura mater by subdural space
      - Subarachnoid space contains CSF & largest blood vessels of brain
      - middle layer w/ spider web-like extensions
    - - Delicate connective tissue that clings tightly to brain, following every convolution
        
        contains many tiny blood vessels that feed brain
- - - - fibrous extension of conus covered w/ pia mater anchors spinal cord
  - - - Ventral (anterior) median fissure
      - Dorsal (posterior) median sulcus
    - - Gray matter & spinal roots
        
        cross section of cord resembles butterfly
        
        3 areas of gray matter are found on each side of center & are mirror images
        
        lateral horns: sympathetic neurons
        
        ventral horns: somatic motor neurons
        
        dorsal horns: interneurons that receive somatic & visceral sensory input
      - white matter: myelinated or nonmyelinated nerve fibers allows communication between parts of spinal cord & spinal cord and brain
        
        divided into 3 white columns (funiculi) on each side Lateral
        
        Ventral (anterior)
        
        Dorsal (posterior)
        
        Lateral
    - - Dorsal roots: Sensory input to cord
      - Dorsal root (spinal) gangilia: Cell bodies of sensory neurons
      - ventral roots: bundle of motor neuron axons that exit the spinal cord
      - spinal nerves: formed by fusion of dorsal & ventral roots
  - - - injury to spinal cord or its roots leads to functional tosses
        
        paralysis: Caused by damage to ventral roots or ventral horn cells- leads to motor function loss 2 types of paralysis flacid or spastic
        
        parethesials: caused by damage to dorsal roots or sensory tracts- leads to sensory function loss
        
        spinal shock: transient period of functional loss caudal lesion
        
        Amytrophic lateral sclerosis (ALS)
        
        also called Lous Genrig's disease
        
        destruction of ventral horn motor neurons and fibers of pynamidal tract
        
        symptoms: Lost of ability to speak, swallow and breathe
        
        death typically occurs within 3 years
        
        caused by enviornment to factors & genetic mutations involuntary RNA processing
        
        involves glutamate excitotxicity
- - - - contains sensorty (afferent) fibers from sensory neurons in dorsal root gangila that conduct impules from periperal receptors
    - - contain motor (efferent) fibers from ventral horn motor neurons that innervates skeletal muscles
- - - - examples: maintain posture, control visceral activites
      - can be modified by learning & conscious effect
    - - example: driving skills
- - - - somatic sensory fibers: Convey impulses from skin, skeletal muscles & joints to CNS
      - Visceral sensor fibers: Convey impulses from visceral organs to CNS
    - - transmits impulses from CNS to effector organs
      - muscles & glands
      - carried signals to CNS
    - - Somatic nervous system (voluntary/concious activities
        
        conscious control of skeletal muscles
        
        somatic motor nerve fibers conduct impulses from CNS to skeletal muscle
      - autonomic nervous system (involuntary)
        
        consists of visceral motor nerve fibers
        
        regulates smooth muscle, cardac muscle & glands
        
        2 functional subvisions
        
        parasympathetic: Promotes maintanence functions conserves energy
        
        keeps body energy use as slow as possible, even while carrying our maintenance activities
        
        Referred as rest-digest system
        
        also called caniosacral division
        
        sympathetic: Mobolized body during activity
        
        referred as fight-flight system
        
        increased heart rate
        
        dilated bronchioles
        
        thoracolumbar
        
        shunts blood to areas that need it & adjusts heart rate blood pressure digestive process etc.
        
        Also called involuntary nervous system or general visceral motor system
- - - - Bipolar: 2 processes (1 axon, 1 dendrite)
        
        rare (ex: retina & olfactory mucosa)
      - unipolar: 1 T-like process (2 axons)
        
        also called pseudounipolar
      - Multipolar: 3 or more processes (1 axon, others dendrites), most common & major neuron type in cns
  - - - sensory
        
        transmit impulses from sensory receptors toward CNS
        
        almost all are unipolar
        
        cell bodies are located in gangila in PNS
      - Motor
        
        Carry impulses from CNS to effectors
        
        Multipolar
        
        Most cell bodies are located in CNS (except some autonomic neuorns)
      - Interneurons
        
        Also called association neurons
        
        Lie betweem motor & sensory neurons
        
        Shuttle signals through CNS pathways
        
        Most are entirely within CNS
        
        99% of body's neurons are interneurons
- - - - Chief motor nerves of face w/ 5 major branches
      - Motor functions include facial expression parasympathetic impulses to lacriminal & salivary glands
      - Fibers from pons travel through internal accoustic mentuses and emerge through stylomastoid foramina to lateral aspect of face
      - Sensory function ( taste from anterior 2/3 of tongue)
    - - Abducens nerves: Fibers from inferior ponsenter orbits via superior orbital fissures
      - primarily a motor, innervating lateral rectus muscle
    - - Fibers from dorsal midbrain enter orbits via superior orbitial fissures to innervate superior oblique muscle
      - Primary motor nerve that directs eyeball
    - - 3 divisions
        
        opthalmia (VI) passes superior orbital fissures
        
        Mamilary (V2) passes foramen votundary
        
        Madibulary (V3) passes foramen ovale
      - convery sensory impulses from various areas of face (V1 & V2)
      - supply motor fibers (V3) for mastication
      - facial expressions
    - - optic tract is continue to thalamus, where they synapse
      - optic vadiation fibers run to occipital visual cortex, purely sensory visual function
      - purely sensory (visual function)
    - - fibers extend from ventral mibrain through superior orbital fissures to 4 of 6 extrinsic eye muscle
      - function in raising eyelid direction eyeball, constricting, iris (parasympathetic, & controling lens shape
      - Directs eyeball, eyelid and controls lens shape and pupil size
    - - fiber synapse in olfactory bulbs
      - pathway reminates inprimary olfactory cortex
      - purely sensory (olfactory) function
    - - motor functions: Innervate part of tongue & parynx for swallowing & provide parasympathetic fibers to parotid salivary glands
      - Sensory functions: Fibers conduct taste & general sensory impulses from pharynx & posterior tongue, & impulses from carotid chemoreceptors & barroreceptors
      - Fibers from medulla leave skull via jugular foramen & run to throat
    - - Afferent fibers from hearing receptors (cochlear division & equilibrium receptors) vestibular division) pass from inner ear through internal accoustic meatuses & enter brain stem at pons medulla border
      - Mostly sensory functions; small motor component for adjustment of sensitivity of receptores
      - Formerly auditor nerve
    - - Fibers from medulla exit skull via jugular foreman
      - Most motor fibers are parasympathetic fibers that help regulate activities of heart, lungs, and abdominal viscera
      - Only canial nerves that extend beyond head & neck region
      - Sensory fibers carry impulses from thoracic & abdominal viscera, baroreceptors, chemoreceptors, & taste buds of posterior tongue & pharynx
    - - Formed from ventral rootlets from CI to C5 region of spinal cord (not brain)
      - Rootlets pass into cranium via each foramen magnum
      - Accessory nerves exit skull via jugular foramina to innervate trapezius & sternocleiodmastoid muscles
      - Formerly spinal accerssory nerve
    - - Innervate extrinsic & intrinsic muscles of tongue that contribute to swallowing & speech
      - Fibers from medulla exit skull via hypglassal canal
- - - - Efferent pathways & gangila
        
        SNS: cell body is in CNA and single, thick myelinated group a axon extends in spinal or cranial nerves directly 10 skeletal muscle
        
        ANS: pathways use 2 neuron chain
        
        preganglionic neuron: Cell body in CNS within lightly myelinated preganglionic axon extending to ganglion
        
        post (ganglionic) neuron outside CNS cell body synapse w/ preganglionic axon in autonomic ganglion w/ nonmyelinated postganglionic axon that extends to effector organ
      - Target organ responses to neurontransmitters
        
        somatic nervous system: All somatic nervous release Ach effect is always stimulatory
        
        ANS: Preganglionic fibers release Ach
        
        effect stimulary or inhibitory, depending on type of receptors
        
        post ganglionic fibers release nonrepinephrine or Ach at effectors
      - effectors
        
        somatic nervous system innervates skeletal muscles
        
        ANS innervates cardiac muscles, smooth muscles & glands