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Nervous System Vanessa Felix P.6, Mouse Party, Drugs of Abuse, networks…

- - - - interacts with prefrontal lobes (emotions "affective brain")
      - puts emotional responses to odors
      - Structures on medial aspects of cerebral hemispheres & diencephalon
      - inclusion of parts of diencephalon & cerebral structures that encircle brain stem
    - - extends through central core of brain stem
      - axonal connections w/ hypothalamus, thalamus, cerebral cortex, cerebellum & spinal cord
      - regulates visceral motor functions
        
        cardiac center
        
        respiratory centers
        
        vasomoto centers
      - helps control coarse limb movements
  - - - Somatic sensory fibers
        
        conveys impulses from skin, skeletal muscles and joints TO CNS
      - Visceral sensory fibers
        
        convey impulses from visceral organs to CNS
    - - Somatic nervous system (voluntary)
        
        conducts impulses from the CNS to skeletal muscles
        
        conscious control of skeletal muscles
      - Autonomic nervous system (involuntary)
        
        consists of visceral motor nerve fibers
        
        regulates smooth & cardiac muscle, and glands
        
        Sympathetic
        
        mobilizes body systems during activity
        
        Parasympathetic
        
        promotes house-keeping functions during rest
- - - - Microglial cells
        
        Small, ovoid cells with thorny processes that touch and monitor neurons
        
        Migrate toward injured neurons
      - Ependymal cells
        
        Range in shape from squamous to columnar
        
        May be ciliated
      - Astrocytes
        
        Most abundant, versatile, and highly branched of glial cells
        
        Cling to neurons, synaptic endings, and capillaries
      - Oligodendroctyes
        
        branched cells
        
        processes wrap CNS nerve fibers, forming insulating myelin sheaths in thicker nerve fibers
    - - Satellite cells
      - Schwann cells (neurolemmocytes)
  - - - Biosynthetic center of neuron
      - In most, plasma membrane is part of receptive region that receives input info from other neurons
      - Nuclei - in CNS
        Ganglia - in PNS
    - - Tracts: bundles of neuron processes in CNS
        Nerves: bundles of neuron processes in PNS
      - Dendrites
        
        Motor neurons can contain 100s of these short, tapering, diffusely branched processes
        
        Convey incoming messages toward cell body as graded potentials
      - Axon
        
        structure
        
        Each neuron has one axon that starts at cone-shaped area called axon hillock
        
        In some neurons, axons are short or absent; in others, axon comprises almost
        entire length of cell
        
        long axons = nerve fibers
        distal endings = axon terminals
        
        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
      - Myelin sheath
        
        Myelinated fibers: segmented sheath surrounds most long or large-diameter axons
        
        Nonmyelinated fibers: do not contain sheath
      - Myelination in PNS
        
        Formed by Schwann cells
        
        Myelin sheath gaps
        
        gaps between adjacent Schwann cells
        
        Nonmyelinated fibers
        
        surrounded by Schwann cells but no coiling
      - Myelination in CNS
        
        Formed by processes of oligodendrocytes, not whole cells
        
        White matter: regions of brain and spinal cord with dense collections of myelinated fibers
        
        Gray matter: mostly neuron cell bodies and nonmyelinated fibers
- - - - carry impulses from CNS to effectors
        
        Multipolar
        
        cell bodies located in CNS (except some autonomic neurons)
    - - lies between motor and sensory neurons
        
        shuttle signals through CNS pathways
        
        entirely within CNS
        
        99% body neurons are interneurons
    - - transmits impulses from sensory receptors toward CNS
        
        almost all unipolar
        
        cell body location; ganglia in PNS
  - - - rare
        
        ex. retina
    - - T-like process
        
        also called pseudounipolar
    - - most common
        
        major neuron type in CNS
- - - - Arachnoid mater
        
        Middle layer, spiderweb-like. separated from dura mater by subarachnoid space
      - Pia mater
        
        Delicate connective tissue that clings to the brain; contains tiny blood vessels that feed (into) the brain
      - Dura mater
        
        Strongest and most durable meninx; milky white appearance; most superficial layer
    - - Protect brain and spinal cord
      - Contain and hold cerebrospinal fluid
  - - - tough fibrous sheath around fascicles
    - - coarse CT that bundles fibers into fascicles
    - - Loose CT that encloses axons and schwann cells
- - - - Epithalamus
        
        contains:
        
        pineal gland (body)
        
        extends from posterior border
        
        secretes melatonin
        
        forms roof of third ventricle
      - Hypothalamus
        
        contains:
        
        mamillary bodies: paried anterior nuclei that act as olfactory relay stations
        
        Infundibulum: stalk that connects to pituitary gland
        
        regulates body temperature
        
        regulates hunger and satiety in response to nutrient blood levels or hormones
        
        regulates water balance
        
        regulates sleep-wake cycles
        
        controls endocrine system
        
        secretions of anterior pituitary gland
        
        production of posterior pituitary hormones
      - Thalamus
        
        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 integration
    - - midbrain
        
        Cerebral penducles:
        two ventral bulges that contain pyramidal motor tracts
        
        Cerebral aqueduct:
        channel running through midbrain that connects third and fourth ventricles
        
        nuclei
        
        Corpora quadrigemina:
        paired dorsal protrusions
        
        inferior colliculi: auditory relay centers
        
        superior colliculi: visual reflex centers
        
        Substantia nigra:
        functionally linked to basal nuclei
      - pons
        
        4th ventricle separates pons from cerebellum
        
        some nuclei play role in reticular formation & help maintain normal rhythm of breathing
      - medulla oblongata
        
        functions
        
        Respiratory centers
        
        control rate and depth of breathing
        
        other centers
        
        vomiting, hiccupping, swallowing, coughing, sneezing
        
        Cardiovascular center
        
        cardiac center: adjusts force and rate of heart contraction
        vasomotor center: adjusts blood vessel diameter for blood pressure
        
        contains fourth ventricle & choroid plexus
    - - surface markings
        
        Sulci
        
        shallow grooves
        
        Major sulci
        
        Central sulcus
        
        separates precentral gyrus of frontal lobe & postcentral gyrus of parietal lobe
        
        Parieto-occipital sulcus
        
        separates occipital and parietal lobes
        
        Lateral sulcus
        
        outlines temporal lobes
        
        Fissures
        
        deep grooves
        
        Longitudinal fissures
        
        separates two hemispheres
        
        Transverse cerebral fissure
        
        separates cerebrum and cerebellum
        
        Gyri
        
        ridges
      - sulci divide lobes
        
        Parietal
        
        Temporal
        
        Frontal
        
        Occipital
        
        Insula
      - each hemisphere has three basic regions
        
        White matter internally
        
        Basal nuclei deep within white matter
        
        Cerebral cortex of gray matter superficially
    - - cerebellar hemispheres connected by wormlike vermis
      - contains arbor vitae
      - functions
        
        plays role in thinking, language and emotion
        
        balance and coordination
        
        processes from input from cortex, brain stem and sensory receptors to provide precise, coordinated movements of skeletal muscles
    - - Cerebral cortex
        
        4 general considers of cerebral cortex
        
        Each hemisphere is concerned with contralateral side of body
        
        lateralization of cortical function can occur in one hemisphere
        
        three types of functional areas
        
        Motor areas: control voluntary movement
        
        Sensory area: conscious awareness of sensation
        
        Association areas: integrate diverse information
        
        conscious behavior involves entire cortex in one way or another
        
        motor areas
        
        Primary motor cortex
        
        located in precentral gyrus of frontal lobe
        
        somatotopy: all muscles of body can be mapped to area on primary motor cortex
        
        Motor homunculi: upside-down caricatures represent contralateral motor innervation of body regions
        
        Premotor cortex
        
        helps plan movements;; skilled motor activities
        
        controls voluntary actions
        
        Broca's area
        
        present in one hemisphere (left)
        
        motor speech area, active in planning speech;; voluntary motor activities
        
        Sensory areas
        
        primary somatosensory cortex
        
        somatosensory association cortex
        
        visual areas
        
        auditory areas
        
        vestibular cortex
        
        olfactory cortex
        
        gustatory cortex
        
        visceral sensory area
- - - - cushion of fat and network of veins in space between vertebrae and spinal dura mater
    - - extends to coccyx
        
        fibrous extension of conus covered with pia mater
        
        anchors spinal cord
    - - extensions of pia mater that secure cord to dura mater
        
        cervical & lumbar enlargements: areas where nerves servicing upper and lower limbs arise from spinal cord
    - - part of PNS
        
        attach to spinal cord by 31 paired roots
        
        each spinal cord segment is designated by paired spinal nerves that arise from it
    - - collection of nerve roots at inferior end of vertebrae canal
    - - Ventral (anterior) median fissure
        
        central canal runs length of cord;;
        grey matter in core, white matter outside
        
        Gray matter
        
        three areas of grey matter found on each side (mirror images)
        
        Ventral horns
        
        some interneurons; somatic motor neurons
        
        Lateral horns
        
        sympathetic neurons
        
        Dorsal horns
        
        interneurons that receive somatic and visceral sensory input
        
        Gray commisure:
        bridge of gray matter that connects masses of gray matter on either side
        
        Ventral roots
        
        bundle of motor neuron axons that exit the spinal cord
        
        Dorsal roots
        
        sensory input to cord
        
        Dorsal root (spinal) ganglia
        
        cell bodies of sensory neurons
        
        Spinal nerves
        
        formed by fusion of dorsal and ventral roots
        
        Gray matter divided into four groups based on of somatic of visceral innervation
        
        Visceral sensory (VS)
        
        Visceral (autonomic) motor (VM)
        
        Somatic sensory (SS)
        
        Somatic motor (SM)
        
        White Matter
        
        divided into three while columns (funiculi)
        
        Lateral
        
        Ventral (anterior)
        
        Dorsal (posterior)
        
        runs in three directions
        
        Transverse
        
        Descending
        
        Ascending
      - Dorsal (posterior) median sulcus
- - - - In nonmyelinated axons, each successive segment of membrane depolarizes, then repolarizes
- - - - Sensory nerves of smell, fibers synapse in olfactory bulbs, purely sensory (olfactory) function
    - - Arise from retinas; really a brain tract, pass through optic canals, converge, and partially cross over at optic chiasma, 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 (parasympathetic), 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
    - - Fibers from inferior pons enter orbits via superior orbital fissures; Primarily a motor, innervating lateral rectus muscle
    - - Formed from ventral rootlets from C1 to C5 region of spinal cord (not brain); Accessory nerves exit skull via jugular foramina to innervate trapezius and sternocleidomastoid muscles
    - - Fibers from medulla exit skull via hypoglossal canal; Innervate extrinsic and intrinsic muscles of tongue that contribute to swallowing and speech
  - - - Afferent fibers from hearing receptors (cochlear division) and equilibrium receptors (vestibular division) pass from inner ear through internal acoustic meatuses and enter brain stem at pons-medulla border
    - - 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 pharynx and posterior tongue
    - - Fibers from pons travel through internal acoustic meatuses and emerge through stylomastoid foramina to lateral aspect of face; Motor functions include facial expression, parasympathetic impulses to lacrimal and salivary glands
    - - Only cranial nerves that extend beyond head and neck region; Most motor fibers are parasympathetic fibers that help regulate activities of heart, lungs, and abdominal viscera
    - - Largest cranial nerves; fibers extend from pons to face
        
        Maxillary (V2) passes through foramen rotundum
        
        Mandibular (V3) passes through the foramen ovale
        
        Ophthalmic (V1) passes through superior orbital fissure
- - - - 31 pairs, mixed nerves
        
        5 pairs of lumbar nerves (L1–L5)
        
        5 pairs of sacral nerves (S1–S5)
        
        12 pairs of thoracic nerves (T1–T12)
        
        1 pair of tiny coccygeal nerves (C0)
        
        8 pairs of cervical nerves (C1–C8)
- - - - Effects of neurotransmitter depends on whether it binds to cholinergic receptor or adrenergic receptor
        
        Cholinergic Receptors
        
        Muscarinic receptors
        
        Nicotinic receptors
        
        Adrenergic Receptors
        
        Alpha (α) receptors
        
        Beta (β) receptors
- - - - Higher brain centers regulate and coordinate both systems
      - Most spinal and many cranial nerves contain both somatic and
        autonomic fibers
    - - Parasympathetic
        
        Keeps body energy use as low as possible; "rest-and-digest" system
      - Sympathetic
        
        Mobilizes body during activity; "fight or flight" system
    - - innervates cardiac muscle, smooth muscle, and glands
    - - pathway uses a two-neuron 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 reganglionic axon in autonomic ganglion with nonmyelinated postganglionic axon that extends to effector organ
    - - Preganglionic fibers release ACh; Postganglionic fibers release norepinephrine or ACh at effectors
  - - - Control of body movements
    - - innervates skeletal muscles
    - - cell body is in CNS, and a single, thick myelinated group A axon extends in spinal or cranial nerves directly to skeletal muscle
    - - All somatic motor neurons release acetylcholine (ACh); Effect is always stimulatory
- - - - Activate skeletal muscle
    - - Activate visceral effectors (smooth or cardiac muscle or glands)
- - - - Contusion
        
        Permanent damage
      - Subarachnoid Hemorrhage
        
        Pressure from blood may force brainstem through the foramen magnum, resulting in death
      - Concussion
        
        Temporary alteration in function
      - Cerebral Edema
        
        Swelling of brain associated with traumatic head injury
    - - Parkinson's Disease
        
        Degeneration of dopamine-releasing neurons of substantia nigra
      - Huntington's Disease
        
        Fatal heredity disorder caused by accumulation of protein huntingtin in brain cells
      - Alzheimer's Disease
        
        Progressive degenerative disease of brain that results in dementia
  - - - Hypertension
        
        Overactive sympathetic vasoconstrictor response to stress; heart must work harder, and artery walls are subject to increased wear-and-tear
      - Raynaud's Disease
        
        Painful, exaggerated vasoconstriction in fingers and toes leaving the digits to turn pale, then cyanotic
      - Autonomic Neuropathy
        
        Damage to autonomic nerves that is a common complication of diabetes mellitus
      - Autonomic Dysreflexia
        
        Life-threatening, uncontrolled activation of autonomic neurons in quadriplegics and people with spinal cord injuries about T6; blood pressure skyrockets, posing increased risk for stroke