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Nervous System, (15) Drugs of Abuse - Coggle Diagram

- - - - Na+ channels open
        
        depolarizing local currents open voltage-gated Na+ channels and Na+ (sodium) rushes into cell
        
        Na+ influx causes more depolarization -> opens more channels
    - - Na+ channels are inactivating and K+ channels open
        
        membrane permeability to Na+ declines to resting state
        
        K+ (potassium) exits cell down its electrochemical gradient
    - - all gated Na+ and K+ channels are closed
    - - Some K+ channels remain open and Na+ channels rest
        
        some K+ channels remain open, allowing excessive K+ efflux
        
        this causes hyperpolarization
        
        Repolarization resets electrical conditions, not ionic conditions
        
        after repolarization, Na+ & K+ pumps restore ionic conditions
- - - - Structures
        
        each neuron has one axon that starts at cone-shaped area called axon hillock
        
        long axons are called nerve fibers
        
        axons branch profusely at their ends ~ terminus
        
        distal endings are called axon terminals or terminal boutons
      - Functional Characteristics
        
        axon is the conducting region of neuron - generates nerve impulses and transmits them along axolemma to axon terminal
        
        Terminal: region that secretes neurotransmitters, which are released in extracellular space
        
        can excite or inhibit neurons it contacts
        
        carries on many conversations with different neurons at the same time
        
        quickly decay if vut or damaged
        
        movement occurs in towards and away from the cell body
  - - - Neuroglia of the CNS
        
        Oligodendrocytes
        
        branched cells
        
        processes wrap CNS nerve fibers, forming insulating myelin sheaths in thicker nerve fibers
        
        Ependymal Cells
        
        line the central cavities of the brain and spinal column
        
        form permeable barrier between CSF in cavities and tissue fluid bathing CNS cells
        
        Microglial Cells
        
        small, ovoid cells with thorny processes that touch and monitor neurons
        
        migrate toward injured neurons (immune)
        
        can transform to phagocytize microorganisms and neuronal debris
        
        Astrocytes
        
        highly branched of glial cells
        Functions:
        
        supporting neuron functions
        
        participate in information processing in brain
        
        play a role in exchange between capillaries and neurons
      - Neuroglia of PNS
        
        Schwann Cells
        
        surrond all periheral nerve fibers and form myelin receptors
        
        vital to regeneration of damaged peripheral nerve fibers
        
        Satellite Cells
        
        surround neuron cell bodies in PNS
        
        function similar to astrocyptes of CNS
- - - - Somatic Nervous System
        
        somatic (involuntary) motor nerve fibers
        
        conduct impulses from CNS to skeletal muscle
        
        conscious control of skeletal muscles
      - Autonomic Nervous System (ANS)
        
        visceral (involuntary) motor nerve fibers
        
        conducts impulses from the CNS to cardiac muscle, smooth muscle, and glands
        
        Sympathetic Division
        
        mobilizes body systems during activity
        
        Examples: exercise, excitement, emergency, embarrassment, activates sympathetic system
        
        Parasympathetic Division
        
        keeps body energy use as low as possible, even while carrying out maintenance activities
        
        directs digestion, diuresis, defecation
- - - - carry impulses from CNS to effectors
        
        multipolar
        
        most cell bodies are located in CNS (except some autonomic neurons)
    - - transmot impulses from sensory receptors toward CNS
        
        almost all are unipolar
        
        cell bodies are located in ganglia in PNS
    - - lie between motor and sensory neurons
        
        shuttle signals through CNS pathways
        - most are entirely within CNS
  - - - two processes | 1A:1D
        
        rare
    - - one T-like process (2 axons)
        
        also called pseudoinipolar
    - - three or more processes | 1A: other dendrites
        
        most common and major neuron type in CNS
- - - - Cerebellum
        
        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
        
        located dorsal to pons and medulla; 11% of brain mass
        
        Cerebellar Hemisphere connected by wormlike vermis
        
        Arbor Vitae: thin cortex of gray matter w/ distinctive treelike pattern of white matter
        
        Purkinje Fibers originate in cortex, synapse with cerebellum
        
        Cerebellar homunculi show sensory maps of entire body
      - Brain Stem
        
        Pons
        
        located between midbrain and medulla oblongata
        
        fourth ventricle separates pons from midbrain
        
        some nuclei play a role in reticular formation or help maintain normal rhythm of breathing
        
        Medulla Oblongata
        
        blends into spinal cord at foramen magnum; contains fourth ventricle
        
        continuation of central canal of spinal cord
        
        medulla and pons from ventral wall
        
        contains choroid plexus: capillary-rich membrane that forms cerebral spinal fluid
        
        Cardiovascular Center
        
        cardiac center adjusts force and rate of heart contraction
        
        rasomotor center adjusts blood vessel diameter for blood pressure regulation
        Respiratory Centers
        
        generate respiratory rhythm
        
        control rate and depth of breathing
        Various Other Centers Regulate:
        
        vomiting, swallowing, sneezing, coughing, and hiccupping
        
        Midbrain
        
        located between diencephalon and pons
        
        Cerebral peduncles: two ventral bulges that contain pyramidal motor tracts
        
        Cerebral Aqueduct: channel running through midbrain that connects 3rd and 4th ventricles
        
        Midbrain nuclei scattered throughout white matter include:
        
        Corpora Quadrigemina: paired dorsal protrusions
        
        Superior Colliculi: visual reflex centers
        
        Inferior Colliculi: auditory relay centers
        
        Substantial Nigra: functionally linked to basal nuclei
      - Diencephalon
        
        Epithalamus
        
        most dorsal portion of diencephalon; forms roof of third ventricle
        
        contains the pineal gland
        
        extends from posterior border
        
        secretes melatonin that helps regulate sleep-wake cycle
        
        Hypothalamus
        
        located below thalamus; forms inferolateral walls of third ventricle
        
        Mammilary Bodies: paired anterior nuclei that act as olfactory relay stations
        
        Infundibulum: stalk that connects to pituitary gland
        
        main vessel control and regulating center that is vital to homeostasis
        
        controls autonomic nervous system
        
        initiates physical responses to emotions
        
        regulates body temperature: sweating or shivering
        
        regulates satiety in response to nutrient blood levels or hormones
        
        regulates hunger, thirst, water balance, and sleep-wake cycle
        
        Thalamus
        
        main thalamic function is to act as relay station for information coming into cortex
        
        overall, it acts to mediate sensation, motor activities, cortical arousal, learning, and memory
        
        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 information
      - Cerebrum
        
        Cerebral Hemisphers
        
        Surface Markings
        
        Sulci
        
        shallow grooves
        
        Fissures
        
        deep grooves
        
        Gyri
        
        ridges
        
        Lobes
        
        Frontal
        
        involves motor function, problem-solving, and social and sexual behavior
        
        Parietal
        
        Processes sensory information it receives
        
        Temporal
        
        responsible for processing auditory (hearing) information and important for the processing of semantics in speech and vision
        
        Occpital
        
        Primarily responsible for visual processing
        
        Insula
        
        Buried under portions of temporal, parietal, and frontal lobes
        
        involved in self-awareness, emotions, and taste and automatic control
        
        Left Hemisphere
        
        controls language, math, and logic
        
        Right Hemisphere
        
        visual-spatial skills, intuition, emotion, and artistic and musical skills
        
        Association Areas
        (integrate diverse information)
        
        receive inputs from multiple sensory areas
        
        send outputs to multiple areas
        
        allows us to give meaning to information received, store in memory, tie to previous experience, and decide on actions
        
        broadly divided into: anterior association area, posterior association area, limbic association area
        
        Sensory Areas
        (conscious awareness of sensation)
        
        areas of cortex concerned with conscious awareness of sensation
        
        occur in parietal, insular, temporal, and occipital lobes
        
        eight main areas include: visual areas, auditory areas, vestibular cortex, olfactory (smell) cortex, gustatory cortex, visceral sensory area, primary somatosensory cortex, and somatosensory association cortex
        
        Somatosensory association cortex
        
        posterior to primary somatosensory cortex
        
        determines size, texture, and relationship of parts of objects being felt
        
        integrates sensory input from primary somatosensory cortex for understanding of object
        
        Primary Somatosensory Cortex
        
        located in postcentral gyri of parietal lobe, receives general sensory information from skin and proprioceptors
        
        capable of spatial discrimination: identification of body region stimulated
        
        somatosensory homunculus: upside-down caricatures represent contralateral sensory input from body regions
        
        Motor Areas
        (control voluntary movement)
        
        Premotor Cortex
        
        helps plan movement
        
        controls learned, repetitions, or patterned motor skills
        
        coordinates simultaneous or sequential actions
        
        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
        
        Primary motor cortex
        
        located in precentral gyrus of frontal lobe
        
        Somatotopy: all muscles of the body can be mapped to area on primary motor
        
        Motor Homunculi: upside-down caricatures represent contralateral motor innervation of body regions
    - - Limbic System
        
        structure on medial aspects of cerebral hemispheres and diencephalon
        
        puts emotional responses to odors
        
        most output relayed via hypothalamus
        
        limbic system interacts with prefrontal lobes
        
        allows us to react emtionally to thingd we consciously understand to be happening
        
        makes us consciously aware of emtional richness in our lives
        
        Fornix: fiber tract that links limbic system regions
        
        Hippocampus and amygdaloid body also play a role in memory
      - Reticular Formation
        
        extends through central core of brain stem
        
        motor function of reticular formation helps control coarse limb movements
        
        reticular automatic centers regulate visceral motor functions
        
        vasomotor centers, cardiac center, and respiratory centers
    - - Language
        
        Broca's area
        
        Involved in speech production
        
        patients with lesions in Broca's understand words, but cannot speak
        
        Wernicke's area
        
        involved in understanding spoken and written words
        
        patients with lesions in Wernick's can speak, but words are nonsensible
        
        language implementation system involves association cortex of left hemisphere
      - Memory
        
        Short-term memory
        
        Temporary holding of information
        
        limited to seven or eight pieces of information
        
        Long-term memory
        
        Limitless capacity
        
        storage and retrieval of information
  - - - provides two-way communication to and from brain and body
      - major reflex center: reflexes are initiated and completed at spinal cord
    - - Cauda Equina
        
        collection of nerve roots at inferior end of vertebral canal
      - Conus Medullaris
        
        spinal cord terminated in cone-shaped structure
      - Spinal Nerves
        
        attach to the spinal cord by 31 paired roots
        
        each spinal cord segment is designated by paired spinal nerves that arise from it
      - Denticulate Ligaments
        
        extensions of pia mater that secure cord to dura mater Cervical and lumbar enlargements: areas where nerves servicing upper and lower limbs arise from spinal cord
      - Filum Terminale
        
        extends to coccyx
        
        fibrous extension of conus covered with pia mater
        
        anchors spinal cord
      - CSF
        
        fills subarachnoid space between arachnoid and pia mater
      - Epidural Space
        
        cushion of fat and network of veins in space between vertebrae and spinal dura mater
- - - - arise from retinas; a brain tract - pass through optic canals, converge, and partially cross over at optic chiasma
        
        optic tracts continue to the thalamus, where they synapse
        
        optic radiation fibers run to the occipital (visual) cortex
        
        purely sensory (visual) function
    - - fibers extend from ventral midbrain through superior orbital fissures to four of six extrinsic eye muscles
        
        function in raising eyelid, directing eyeball, constricting iris, and controlling lens shape
    - - fibers from dorsal midbrain enter orbits via superior orbital fissures to innervate superior oblique muscle
        
        primarily motor nerve that directs eyeball
    - - largest cranial nerves; fibers extend from pons to face
        
        convey sensory impulses from various areas of face (V1 and V2)
        
        supply motor fibers (V3) for mastication
        
        ▪ Ophthalmic (V1) passes through superior orbital fissure
        
        ▪ Maxillary (V2) passes through foramen rotundum
        
        ▪ Mandibular (V3) passes through the foramen ovale
    - - fibers from inferior pons enter orbits via superior orbital fissures
        
        primarily a motor, innervating lateral rectus muscle
    - - Fibers from pons travel through internal acoustic meatuses and emerge through stylomastoid foramina to the lateral aspect of the face
        
        Motor functions include facial expression, parasympathetic impulses to lacrimal and salivary glands
        
        Sensory function (taste) from anterior 2/3 of tongue
    - - Afferent fibers from hearing receptors (cochlear division) and equilibrium receptors (vestibular division) pass from the inner ear through internal acoustic meatuses and enter the brain stem at the pons-medulla border
        - Mostly sensory function; small motor component for adjustment of the sensitivity of receptors
        
        Formerly auditory nerve
    - - fibers from the medulla leave the skull via the jugular foramen and run to the throat
        
        Motor functions: innervate part of tongue and pharynx for swallowing and provide parasympathetic fibers to parotid salivary glands
        
        Sensory functions: fibers conduct taste and general sensory impulses from the pharynx and posterior tongue, and impulses from carotid chemoreceptors and baroreceptors
    - - only cranial nerve that extend beyond head and neck region
        
        fibers from medulla exit skull via jugular foramen
        
        most motor fibers are parasympathetic fibers that help regulate activites of hear, lung, and abdominal viscera
        
        sensory fibers carry impulses from thoracic and abdominal viscera, baroreceptors, chemoreceptors, taste buds of posterior tongue and pharynx
    - - accessory nerves exit the skull via jugular foramina to innervate trapezius and sternocleidomastoid muscles
        
        formerly spinal accessory nerve
    - - fibers from the medulla exit the skull via the hypoglossal canal
        
        innervate extrinsic and intrinsic muscles of the tongue that contribute to swallowing and speech
    - - sensory nerves of smell
        
        pathway terminates in primary olfactory cortex
        
        purely sensory (olfacttory) function
- - - - Peptides (neuroprptides)
        
        strings of amino acids that have diverse functions
        
        Endorphins: beta endorphin, dynorphin. and enkephalins: act as natural opiates; reduce pain perception
      - Purines
        
        monomers of nucleic acids that have an effect in CNS and PNS
      - Amino Acids
        
        make up all proteins; it is difficult to prove which are neurotransmitters
        
        are proven neurotransmitters
      - Gases and Lipids
      - Biogenic Amines
        
        Catecholamines
        
        Dopamine, norepinephrine. and epinephrine made from the amino acid tyrosine
        
        Indolamines
        
        Serotonin: made from the amino acid tryptophan
        
        Histamine: made from the amino acid histidine
        
        all widely used in the brain: play roles in emotional behaviors and biological clock
        
        used by some ANS motor neurons
        
        imbalances are associated with mental illness
      - Endocannabinoids
        
        act as the same receptors as THC
      - Acetylcholine (ACh)
        
        released at neuromuscular junctions
        
        used by many ANA neurons and some CNA neurons
        - synthesized from acetic acid and choline by enzyme choline acetyltransferase
        
        degraded by enzyme acetylcholinesterase (AChE)
    - - Effects
        
        neurotransmitter effects can be excitatory (depolarizing) and/or inhibitory (hyperpolarizing)
        
        effect determined by receptor to which it binds
      - Actions
        
        Direct Action: neurotransmitter binds directly to and opens ion channels
        
        Indirect Action: neurotransmitter acts through intracellular second messengers
- - - - either monosynaptic or polysynaptic region within CNS
    - - conducts efferent impulses from integration center to effector organ
    - - transmits afferent impulses to CNS
    - - muscle fiber or gland cell that responds to efferent impulses by contracting or secreting
    - - site of stimulus