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Nervous System :explode: Ezequiel Herrera Period 4 Yang (Drugs that…

- - - - Somatic NS
        
        Somatic (voluntary) motor nerve fibers
        
        conduct impulses from the CNS to skeletal muscles
      - autonomic NS (ANS)
        
        consists of visceral motor nerve fibers
        
        regulate the activity of smooth muscles, cardiac muscle, and glands.
        
        sympathetic division
        
        -Conserves energy
        -Promotes house-keeping functions during rest
        
        parasympathetic division
        
        Mobilizes body systems during activity
- - - - forms the roof of the third ventricle
      - secretes the hormone melatonin and helps regulate the sleep-wake cycle.
    - - consists of bilateral egg-shaped nuclei, which form the superolateral walls of the third ventricle
      - The thalamus is the relay station for information coming into the cerebral cortex.
      - virtually all other inputs ascending to the cerebral cortex funnel through thalamic nuclei
    - - caps the brain stem and forms the inferolateral walls of the third ventricle
      - It's chief homeostatic roles are
        
        Control the autonomic nervous system
        
        Initiate physical responses to emotions
        
        Regulate body temperature
        
        Regulate food intake
        
        Regulate water balance and thirst
        
        Regulate sleep-wake cycles
        
        Control endocrine system function
  - - - Midbrain
        
        located between the diencephalon and pons
        
        superior colliculi
        
        visual reflex centers that coordinate head and eye movements when we visually follow a moving object
        
        inferior colliculi
        
        act in reflexive responses to soun
  - - - Pons
        
        brain stem region wedged between the midbrain and the medulla oblongata
        
        -Connects the medulla with the midbrain
        -Provides linkage with the upper and lower levels of the NS
    - - Function: Motor Output, Ensuring Coordination and Balance
        
        calculates the best way to coordinate the force, direction, and extent of muscle contraction to prevent overshoot, maintain posture, and ensure smooth, coordinated movements
  - - - Medulla Oblangata
        
        The medulla contains these important functional groups of visceral motor nuclei
        
        Respiratory centers
        
        Various other centers
        
        regulate such activities as vomiting, hiccuping, swallowing, coughing, and sneezing
        
        Cardiovascular center
        
        several nuclei associated with ascending sensory tracts
        
        two longitudinal ridges called pyramids
- - - - prepare the body's muscles for the exact movements the will make
    - - responsible for producing language. It controls motor functions involved with speech production.
    - - responsible for the comprehension of speech
- - - - the dura mater, arachnoid mater, and pia mater
      - 1) Dura Mater
        
        the strongest meninx, it is a two-layered sheet of fibrous connective tissue
        
        The more superficial periosteal layer attaches to the inner surface of the skull
        
        The deeper meningeal layer forms the true external covering of the brain and continues caudally in the vertebral canal as the spinal dura mater
        
        2)Arachnoid Mater
        
        forms a loose brain covering, never dipping into the sulci at the cerebral surface
        
        It is separated from the dura mater by the subdural space
        
        Beneath the arachnoid membrane is the wide subarachnoid space
        
        filled with cerebrospinal fluid
        
        arachnoid granulations protrude superiorly through the dura mater and into the superior sagittal sinus
        
        absorb cerebrospinal fluid into the venous blood of the sinus
        
        3)Pia mater
        
        Composed of delicate connective tissue and contains many tiny blood vessels
        
        only meninx that clings tightly to the brain like plastic wrap, following its every convolution
        
        Small arteries entering the brain tissue carry ragged sheaths of pia mater inward with them for short distances
        
        the meningeal dura mater extends inward to form flat partitions that subdivide the cranial cavity
        
        AKA dural septa
        -Limit excessive movement of the brain
        
        Falx cerebri
        
        A large fold that dips into the longitudinal fissure between the cerebral hemispheres
        
        Falx cerebelli
        
        runs along the vermis of the cerebellum
        
        Tentorium cerebelli
- - - - Each lateral ventricle communicates in the diencephalon with the narrow third ventricle
      - Communication w/ other ventricles allowed via a channel called an interventricular foramen
      - 4) Fourth ventricle
        
        Continuous with the 3rd ventricle
        
        via the canal-like cerebral aqueduct that runs through the midbrain
        
        lies in the hindbrain dorsal to the pons and superior medulla.
        
        Three openings mark the walls of the fourth ventricle: the paired lateral apertures and the median aperture
- - - - conduct messages in the form of nerve impulses from one part of the body to another
  - - - lose their ability to divide
  - - - Other Functions
        
        cell body is the major biosynthetic center and metabolic center of a neuron
        
        The plasma membrane of the cell body acts as part of the receptive region that receives information from other neurons
      - Consists OF:
        
        A spherical nucleus
        
        surrounded by cytoplasm.
        
        Protein- and membrane-making machinery
        
        Cytoskeletal elements
        
        Pigment inclusions
  - - - Armlike processes extend from the cell body
      - The brain and spinal cord (CNS) contain both neuron cell bodies and their processes. The PNS consists chiefly of neuron processes
      - dendrites and axons
        
        Dendrites
        
        short, tapering, diffusely branching extensions
        
        all organelles present in the cell body also occur in dendrites
        
        the main receptive or input regions, provide an enormous surface area for receiving signals from other neurons
        
        In many brain areas, the finer dendrites are highly specialized for collecting information
        
        Dendrites convey incoming messages toward the cell body
        
        Axons
        
        The axon arises from a cone-shaped area of the cell body called the axon hillock
        
        Very in length
        
        Any long axon is also called a nerve fiber
        
        Bundles of axons are called tracts in the CNS and nerves in the PNS
        
        Functional Characteristics
        
        When the impulse reaches the axon terminals, it causes neurotransmittersto be released into the extracellular space
        
        The axon is the conducting region of the neuron
        
        It generates nerve impulses and transmits them
        
        it lacks rough endoplasmic reticulum and a Golgi apparatus
        
        depends on its cell body to renew the necessary proteins and membrane components
        
        Depends on efficient transport mechanisms to distribute them
        
        Axonal Transport
        
        Anterograde movement
        
        movement away from the cell body
        
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        Retrograde movement
        
        is movement toward the cell body
        
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- - - - Sensory, or afferent, neurons
        
        transmit impulses from sensory receptors in the skin or internal organs toward or into the central nervous system
      - Motor, or efferent, neurons
        
        carry impulses away from the CNS to the effector organs of the body
        
        Motor neurons are multipolar
      - Interneurons
        
        lie between motor and sensory neurons in neural pathways
        
        shuttle signals through CNS pathways where integration occurs
        
        Almost all interneurons are multipolar
- - - - filled with a soft padding of fat and a network of veins
    - - lumbar (L)
      - thoracic (T)
      - cervical (C)
      - sacral (S)
    - - Each spinal cord segment is designated by the paired spinal nerves that arise from it
        
        Each nerve exits from the vertebral column by passing adjacent to its corresponding vertebra via the intervertebral foramen
    - - two grooves mark its surface
        
        dorsal (posterior) median sulcus
        
        ventral (anterior) median fissure
        
        The cerebrospinal fluid–filled central canal runs the length of the spinal cord
      - Gray Matter and Spinal Roots
        
        In cross section the gray matter of the cord looks like the letter H
        
        It consists of mirror-image lateral gray masses connected by a crossbar of gray matter, the gray commissure
        
        The two dorsal projections of the gray
        
        ventral (anterior) horns
        
        dorsal (posterior) horns
        
        All neurons whose cell bodies are in the spinal cord gray matter are multipolar
        
        The amount of ventral gray matter present at a given level of the spinal cord reflects the amount of skeletal muscle innervated
        
        ventral horns are largest in the limb-innervating cervical and lumbar regions of the cord and are responsible for the cord enlargements
        
        spinal gray matter can be divided further according to relative involvement in innervating the somatic and visceral regions of the body
        
        somatic sensory (SS), visceral sensory (VS), visceral (autonomic) motor (VM), somatic motor (SM)
    - - composed of myelinated and nonmyelinated nerve fibers
        
        allows communication between different parts of the spinal cord and between the cord and brain
        
        Descending, meaning down to the cord from the brain or within the cord to lower levels
        
        motor outputs
        
        Transverse
        
        across from one side of the cord to the other
        
        Ascending, up to higher centers
        
        The white matter on each side of the cord is divided into three white columns,
        
        named according to their position as dorsal (posterior), lateral, and ventral (anterior) funiculi
        
        each tract is made up of axons with similar destinations and functions
        
        Ascending and descending tracts make up most of the white matter
    - - Poliomyelitis
        
        results from the poliovirus
        
        paralysis develops and the muscles served atrophy
        
        The patient may die from paralyzed respiratory muscles
        
        survivors of the great polio epidemic have begun to experience burning pains in their muscles, and progressive muscle
        
        postpolio syndrome
      - Spinal Cord Trauma
        
        paresthesias
        
        Comes from damage to the dorsal roots or sensory tracts
        
        paralysis
        
        Comes from damage to ventral roots or ventral horn cells
        
        Flaccid paralysis
        
        occurs when the spinal cord or ventral roots are injured
        
        Nerve impulses do not reach the affected muscles, which consequently cannot move either voluntarily or involuntarily
        
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        Spastic paralysis
        
        occurs if only the upper motor neurons of the primary motor cortex are damaged
        
        muscles remain healthy longer, but their movements are no longer subject to voluntary control
      - Amyotrophic Lateral Sclerosis (ALS)
        
        progressively destroys ventral horn motor neurons and fibers of the pyramidal tracts
        
        the patient loses the ability to speak, swallow, and breathe
  - - - provides a two-way conduction pathway to and from the brain
        
        All major spinal tracts are part of multineuron pathways that connect the brain to the body periphery
        
        There are four key points in regard to spinal tracts and pathways
        
        Decussation
        
        Most pathways cross from one side of the CNS to the other
        
        Relay
        
        Most pathways consist of a chain of two or three neurons that contribute to successive tracts of the pathway
        
        Somatotopy
        
        a precise spatial relationship among the tract fibers that reflects the orderly mapping of the body
        
        Symmetry
        
        All pathways and tracts are paired symmetrically
- - - - Ecstasy affects mood, sleep, perception and appetite. The person under the influence will experience that good feeling due to the release of dopamine along the reward pathway
      - Serotonin neurotransmitters
  - - - The person will immediately have feelings of sedation and well-being. Also, the person will feel less physical and psychological pain
      - Dopamine and Inhibitory neurotransmitters
  - - - THC mimics anandamide and binds to cannabinoid receptors. Inhibition is turned off, allowing dopamine to enter the synapse
        
        Marijuana can cause memory loss. It also provokes the person to feel relaxed, calm and a sense that movement is slowed down
  - - - Alcohol first reacts with GABA receptors to make them more inhibitory. Then,it binds to glutamate receptors, exciting the cell
        
        Alcohol affects areas of the brain including memory formation, decision making and impulse control
  - - - Meth mimics dopamine and it is taken into the cell via dopamine transporters. It pushes real dopamine out the vesicle, causing an ancess amount of dopamine. Now, the brain works in reverse, and pumps dopamine into the synapse
        
        Meth works directly on the brain's reward pathway, making the user feel pleasure and exhilaration
  - - - Cocaine blocks dopamine transporters leaving dopamine trapped in the synaptic cleft. Thus, dopamine binds over and over again, overstimulating the cell
        
        Cocaine users will feel a sense of awareness and well-being. Cocaine users also fidget and are unable to stay still
  - - - LSD interacts with serotonin receptors, but not always in the same way. For example, there are several serotonin receptors in the brain, each responsible for a specific function. LSD triggers different receptors each time
        
        The person will experience complex sensory effects. They will have feelings of wakefulness and evoke startle response to unexpected stimulus
- - - - They are bundles of myelinated and nonmyelinated peripheral axons enclosed by
        connective tissue
        
        Two main types, cranial or spinal, depending on where they originate
        
        Connective tissue coverings include:
        
        Perineurium
        
        coarse connective tissue that bundles fibers into fascicles
        
        Epineurium
        
        tough fibrous sheath around all fascicles to form the nerve
        
        Endoneurium
        
        loose connective tissue that encloses axons and their myelin
        sheaths (Schwann cells)
  - - - 12 pairs of cranial nerves are associated with brain
        Each numbered (I through XII) and named from rostral to caudal
        
        I: Olfactory nerves
        
        • Sensory nerves of smell
        
        • Fibers synapse in olfactory bulbs
        
        • Pathway terminates in primary olfactory cortex
        
        • Purely sensory (olfactory) function
        
        II: Optic nerves
        
        Arise from retinas
        
        Purely sensory (visual) function
        
        III: Oculomotor nerves
        
        Function in raising eyelid, directing eyeball, constricting iris and controlling lens shape
        
        IV: Trochlear nerves
        
        Primarily motor nerve that directs eyeball
        
        V: Trigeminal nerves
        
        Largest cranial nerves; fibers extend from pons to face
        
        Convey sensory impulses from various areas of face
        
        Supply motor fibers for mastication
        
        VII: Abducens nerves
        
        Primarily a motor, innervating lateral rectus muscle
        
        VII: Facial nerves
        
        Fibers from pons travel through internal acoustic meatuses and emerge through stylomastoid
        
        Chief motor nerves of face with five major branches
        
        Motor functions include facial expression, parasympathetic impulses to lacrimal and salivary glands
        
        VIII: Vestibulocochlear nerves
        
        Afferent fibers from hearing receptors and equilibrium receptors pass from inner ear
        
        Mostly sensory function; small motor component for adjustment of sensitivity of receptors
        
        IX: Glossopharyngeal nerves
        
        Fibers from medulla leave skull via jugular foramen and run to throat
        
        Motor functions: innervate part of tongue or swallowing
        
        Sensory functions: fibers conduct taste and general sensory
        
        X: Vagus nerves
        
        Most motor fibers are parasympathetic fibers that help regulate activities of heart, lungs,
        and abdominal viscera
        
        Sensory fibers carry impulses
        
        XI: Accessory nerves
        
        Formerly spinal accessory nerve
        
        XII:Hypoglossal nerves
        
        Innervate extrinsic and intrinsic muscles of tongue that contribute
        to swallowing and speech
    - - 31 pairs of spinal nerves
      - Supply all body parts except head and part of neck
        
        8 pairs of cervical nerves (C1–C8)
        
        12 pairs of thoracic nerves (T1–T12)
        
        5 pairs of lumbar nerves (L1–L5)
        
        5 pairs of sacral nerves (S1–S5)
        
        1 pair of tiny coccygeal nerves (C0)
      - Innervation of skin: dermatomes
        
        area of skin innervated by cutaneous
        branches of single spinal nerve
        
        Extent of spinal cord injuries ascertained by affected dermatomes
        
        All spinal nerves except C1 participate in dermatomes
- - - - supplies motor impulses to cardiac muscle, to smooth muscle, and to glandular epithelium
      - parasympathetic divisions
        
        controls functions of the body at rest. It helps maintain homeostasis in the body. It causes muscles to relax and heart rate to decrease
      - sympathetic division
        
        prepares the body to react to stresses such as threat or injury. It causes muscles to contract and heart rate to increase
    - - supplies motor impulses to the skeletal muscles
        
        permit conscious control of the skeletal muscles, it is sometimes called the voluntary nervous system
- - - - Classification of Neurotransmitters by Chemical Structure
        
        Acetylcholine
        
        ACh is released by all neurons that stimulate skeletal muscles and by many neurons of the autonomic nervous system
        
        Peptides
        
        include a broad spectrum of molecules with diverse effects.
        
        Purines
        
        Two purines, ATP and adenosine, also have well-established roles as chemical messengers:
        
        Amino Acids
        
        include glutamate, aspartate, glycine,GABA
        
        Gases and Lipids
        
        Gasotransmitters
        
        nitric oxide, carbon monoxide, and hydrogen sulfide
        
        Endocannabinoids
        
        act at the same receptors as tetrahydrocannabinol (THC)
        
        Biogenic Amines
        
        include sero-tonin and histamine
        
        Classification of Neurotransmitters by Function
        
        Effects: Excitatory versus Inhibitory
        
        Effects: Excitatory versus Inhibitory
- - - - All voltage-gated Na+ and K+ channels are closed
    - - Voltage-gated Na+ channels open
    - - Na+ channels are inactivating, and voltage-gated K+ channels open
    - - Some K+ channels remain open, and Na+ channels reset
- - - - •Somatic nervous system innervates skeletal
        muscles
      - •ANS innervates cardiac muscle, smooth muscle, and glands
    - - SNS: cell body is in CNS, and a single, thick myelinated group
      - ANS: pathway uses a two-neuron chain
        
        Preganglionic neuron: cell body in CNS with thin, lightly myelinated preganglionic axon extending to ganglion
        
        Postganglionic (ganglionic) neuron
    - - •Somatic nervous system
        
        •All somatic motor neurons release acetylcholine (ACh)
        
        •Effect is always stimulatory
      - •ANS
        
        •Preganglionic fibers release ACh
        
        •Effect is either stimulatory or inhibitory, depending on type of receptors
- - - - Activate skeletal muscle
    - - Activate visceral effectors (smooth or cardiac muscle or glands)
- - - - The victim may be dizzy or lose consciousness
- - - - characterized by temporary numbness, paralysis, or impaired speech
- - - - kills the neurons by disrupting their transport mechanisms.
- - - - Commissural fibers
        
        connect corresponding gray areas of the two hemispheres
      - Projection fibers
        
        They tie the cortex to the rest of the nervous system and to the body’s receptors and effectors
        
        projection fibers run vertically
      - Association fibers
        
        Connect different parts of the same hemisphere
  - - - The basal nuclei receive input from the entire cerebral cortex
- - - - found in some of the special organs such as in retina of the eye and in the olfactory mucosa
  - - - peripheral process
        
        associated with a sensory receptor
      - central process
        
        enters the CNS
      - Unipolar neurons are found chiefly in ganglia in the PNS
  - - - most common neuron type in humans, with more than 99% of neurons in this class
        
        major neuron type in the CNS
- - - - an AP must be propagated along the axon’s entire length
        
        Once generated, all APs are independent of stimulus strength, and all APs are alike
        
        Strong stimuli generate nerve impulses more often in a given time interval than do weak stimuli
        
        Refractory Periods
        
        the neuron cannot respond to another stimulus
        
        Ensures that each AP is a separate, all-or-none event
        
        Enforces one-way transmission of the AP
        
        Conduction Velocity
        
        The rate of impulse propagation depends largely on two factors
        
        Axon diameter
        
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        Degree of Myelination
        
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