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P&a unit 4   nervous system
 

P&a unit 4 nervous system

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    P&a unit 4   nervous system P&a unit 4 nervous system Presentation Transcript

    • P&A Unit 4
      Nervous System
    • I. Intro – 2 parts to Nervous System
      A. Central Nervous System – CNS
      Brain and spinal cord
      B. Peripheral Nervous System – PNS
      All the nerves that connect to CNS and other body parts
    • II. Nervous Tissue
      A. Neurons
      1. Def: Nerve cell – structural and functional unit of the nervous system
      B. Neuron Structure
      1. cell body
      Main portion of neuron
      Contains neurofibrils
      Conatains NISSIL BODIES
      Make protein
      Contains nucleus
      Mature neurons cannot reproduce
      DESTROY THEM AND THEY ARE GONE!!
    • 2. dendrites
      Short, highly branched parts off of cell body
      Each neuron may have many
      F: main RECEPTIVE surface of neuron
      Communicates with other neurons
      **BRINGS IMPULSES IN
    • 3. axon
      An extension of the cell body which sends impulses AWAY from the neuron
      Schwaan cells
      Cells which surround axon
      Make up myelin (lipoprotein) sheath
      MS – makes impulse travel very quickly
      A). Not all axons are myelinated
      GRAY MATTER
      Def: group of cells in NS which are unmyelinated
      WHITE MATTER
      Def: group of cells in NS which ARE myelinated
      Nodes of Ranvier
      Def: narrow gaps in myelin sheath b/n axon cells
    • III. Nerve Impulse Conduction
      A. Nerve impulse
      Def: the propagation (increase/transmission) of electrical charges along nerve cells
      B. Process of Conduction
      1. nerve fiber develops resting potential
      Def: state in which a net POSITIVE charge is on the OUTSIDE of the cell membrane = POLARIZED
      Cause: Na+ and K+ are key ions
      3 Na+ ions diffuse outside the nerve fiber – low to high conc.
      2 K+ ions diffuse inside the nerve fiber – low to high
      What is the charge? POSITIVE on OUTSIDE = resting potential
    • 2. Threshold stimulus is received
      Minimal stimulus needed for a nerve to fire
      Will be reached if a nerve is stimulated by:
      Nearby nerve stimulus
      Changes in light, temperature, pressure
      Resting potential decreases – net positive charge on outside of membrane decreases
      How?
      Sodium/Potassium pump = active transport
      Na+ channels open and Na+ starts flowing inside (L to H) cell membrane = DEPOLARIZED
      If stimuli are strong enough, THRESHOLD STIMULUS is reached
    • 3. Shortly after, K+ diffuses outside of cell (L to H) causing the cell to be REPOLARIZED
      4. Action potential occurs
      Def: rapid depolarization and repolarization of a nerve cell
      Lasts 1/1000 of a second
      Causes electric current to flow to next area of nerve cell
      5. Wave of APs continue through nerve = IMPULSE
      6. refractory period
      Time when nerve is repolarizing and will not respond to another stimulus
      http://people.eku.edu/ritchisong/301notes2.htm
    • C. Impulse conduction
      1. unmyelinated fibers
      Impulses travel slowly
      2. myelinated fibers
      Impulses travel quickly
      Jump from N of R to N of R
    • D. all or none response
      Nerve fiber ALWAYS responds completely when TS is reached
      Impulse always travels through entire nerve
      E. Synapse
      Def: the junction where 2 neurons meet and interact
      Sending neuron: PRESYNAPTIC NEURON
      Receiving neuron: POSTSYNAPTIC NEURON
      Synaptic cleft: space b/n pre and post neurons
      ** impulses jump this gap when traveling
    • F. Neurotransmitters
      1. def: chemical substance released by presynaptic neuron which may cause impulses to be conducted to postsynaptic neuron
      ** if enough NT is released, TS in postsynaptic is reached and impulse travels
      2. Types
      A. excitatory NT
      Cause impulse to quickly be transferred to postsynaptic neuron
      Allows ions to quickly diffuse through membrane
      B. inhibitory NT
      Cause impulse to die
      TS is raised because ions can’t diffuse
    • Examples
      Excitatory
      Acetylcholine
      Dopamine
      Inhibitory
      GABA – gamma amino butyric acid
      Mood, control many other excitatory NT
      Serotonin
      Slow the brain down, reduce stress, relax, effect mood
    • V. Types of Neurons/nerves
      A. Multipolar neurons – many nerve fibers
      Many dendrites/ 1 axon
      Located: brain and spinal cord
      B. bipolar neurons – 2 nerve fibers
      1 axon/ 1 dendrite
      Located: eyes, nose, ears
      C. unipolar neuron – 1 nerve fiber, splits into A and D
      1 dendrite/ 1 axon
      Axon connected to brain/ spinal cord
      Dendrite connected to peripheral body part
    • D. Nerve types
      Nerves: group of neurons held together by connective tissue
      1. sensory nerves
      Send messages to brain/SC
      2. motor nerves
      Send messages to muscles/glands
      3. mixed nerves
      Send messages to both
      4. interneurons
      Connect nerves in brain/SC
    • VI. Nerve pathways
      A. reflex arc
      1. def: the simplest pathway an impulse may take
      ** never reaches the brain
      Process:
      1. Sensory receptor at end of sensory nerve fiber takes in stimulation
      2. SNF takes it to reflex processing center in Spinal Cord
      3. interneurons communicate in SC
      4. motor neuron carries response to effector
      5. effector does action – muscle, gland etc
    • B. reflex behavior
      1. def: automatic unconscious responses to changes occurring within or outside the body
      2. controls:
      Heart rate
      Breathing rate
      Blood pressure
      Digestion
      Sneezing
      Coughing
      Vomiting
    • 3. example: knee jerk
      A. sensory receptor sense touch to petallar ligament
      B. sensory nerve fiber dendrite takes in info
      C. impulse sent to SC where sensory axon meets an interneuron which connects to motor neuron dendrite
      D. motor axon carries impulse to effector in quad
      E. quad flexes
      4. withdrawal reflex
      Person touches something hot, pulls away body part
      P. 214
    • VII. Impulse processing
      A. convergence
      1. def: neuron impluses from 2 or more axons converge on 1 neuron
      Allows NS to bring different information together
      B. divergence
      1. def: impulses leaving 1 axon pass into several other neurons
      Allows impulse effect to be amplified
      Ex: send message to all motor neurons in muscle so all contract
    • VIII. Coverings of CNS
      A. Intro
      1. brain lies in: cranial cavity
      2. SC lies in: vertebral canal
      3. both surrounded by membranes called MENINGES
      Between bone and nerve tissue
    • B. meninges
      3 layers
      Dura mater
      Arachnoid mater
      Pia mater
      1. dura mater
      Outermost
      Tough, white connective tissue
      Many vessels & nerves
      May extend into lobes of brain
    • 2. arachnoid mater
      Thin, weblike
      Middle layer
      No blood vessels
      ** Cerebrospinal fluid between arachnoid and pia mater – CSF
      3. pia mater
      Thin
      Innermost
      Many vessels to nourish brain and SC
    • VIII. Spinal Cord
      A. Intro
      Cord begins at foramen magnum and end at intervertebral disk b/n 1st and 2nd lumber vertebrae
      B. structure
      1. 31 segments, each with a pair of nerves that branches off peripherally
      Spinal nerves
      8 cervical
      12 thoracic
      5 lumbar
      5 sacral
      1 coccygeal
      CAUDA EQUINA – last group of nerves, taillike
    • 2. Cross Section
    • 3. Functions of SC
      1. to conduct nerve impulses to and from Brain
      Involves only white matter
      A. ascending tract
      Carry impulses TO brain
      B. descending tract
      Carry impulses FROM brain to muscles/glands
      2. to be the center of the reflex arc
      Involves grey matter
    • IX. Brain
      A. Intro
      100 billion multipolar neurons
      3 major portions:
      1. cerebrum
      Largest
      Nerve centers for sensory and motor functions
      Memory and reasoning centers here
      2. cerebellum
      Posterior/dorsal region
      Coordinates complex skeletal voluntary muscle movements
      Maintains posture
      Position of body parts
      3. brain stem
      Connects nerve pathways that connect many nerves between SC and brain
      Regulate many organ activities
    • B. Cerebrum
      1. Structure
      A. cerebral hemispheres (2)
      2 equal halves of cerebrum
      B. corpus callosum
      Bridge of nerve fibers that connects cerebral hemisheres
      Allows R and L sides to communicate
      C. convolutions
      Ridges of cerebrum
      D. sulcus
      Groves b/w convolutions
      E. fissures
      DEEP groves b/n parts of the brain
    • F. frontal lobe
      G. parietal lobe
      H. occipital lobe
      I. Temporal lobe
      J. cerebral cortex
      Thin layer of grey matter over cerebrum
      Covers convolutions, sucli, and fissures
      Contains nearly 75% of all neuron cell bodies
      Just beneath is a mass of White Matter that makes up cerebrum
    • 2. functions
      A. frontal lobe
      1. motor speech area – Broca’s Area
      Moves mouth, tongue, pharynx, larynx
      2. frontal eye field
      Controls voluntary movements of eyes and eyelids
      3. Concentration, planning, problem solving area
      4. emotions and reasoning
      5. motor areas which control voluntary muscles
    • B. parietal lobe
      Sensory areas involved with sensations of skin
      Understanding speech, using words
      C. occipital lobe
      Visual area
      Combines visual images from L and R eyes
      Recognition
      D. temporal lobe
      Interpretation of sensory experiences
      Memory of visual and audio patterns
      E. general interpretive area
      Overlaps all lobes
      Primary in complex thought and processing
      F. hemisphere dominance
      L= verbal, analytical, computational, detailed
      R= musical, visual, creative,
    • C. cerebrospinal fluid – CSF
      1. structure
      A clear liquid that is secreted by CHOROID PLEXUS in pia mater
      Tiny flowerlike masses
      Circulates around the brain and down central canal of SC – eventually reaches blood to deliver wastes etc
      2. function
      Surrounds brain and SC for support/protection
      Provide path to blood for waste
      ** always stays at same pressure b/c it is continually made and reabsorbed
      ** it not, pressure on the brain
    • D. cerebellum
      1. located below occipital lobe
      2. mostly white matter
      3. covered by CEREBELLAR CORTEX – grey matter
      4. involved in:
      Planning
      Personality
      Intelligence
      Interprets desired movements and causes body to do them
      5. damage = :
      Tremors
      Loss of muscle tone
      Uncoordinated walk
      Loss of equilibrium
    • E. brain stem
      Def: bundle of nerve tissue that connects cerebrum to spinal cord
      Several masses of grey matter
      1. Parts:
      A. diencephalon
      b/w cerebral hemispheres
      1) infundibulum here
      A piece which hangs down and attaches to pituitary gland
      2) thalamus here
      Receives all sensory impulses and relays them to appropriate region of cortex for interpretation
    • 3) hypothalamus here
      Regulates heart rate, blood pressure, body temp, hunger, release of hormones, regulates sleep
      4)limbic system here
      Combination of many areas
      Involved in emotional expression
      Fear, anger, pleasure, sorrow
      Recognizes things that threaten life – “fight or flight”
    • B. midbrain
      Below diencephalon
      Much grey matter as a reflex center
      Visual reflex = eyeballs move when head moves
      Auditory reflex = ears move close to sound
      C. pons
      Below midbrain – round bulge
      Relay impulses all over brain
      Ex: relays breathing rhythms to medulla oblongata
      D. medulla oblongata
      Extends from pons
      Controls:
      Cardiac center: speed or lower heart rate
      Vasomotor center: constrict/dilate blood vessels
      Respiratory center: rate/rhythm of breathing
    • X. Peripheral Nervous System - PNS
      A. def: nerves that branch out from the brain and SC
      SOMATIC NS: consists of cranial and spinal nerves that connect to skin and skeletal muscle
      AUTONOMIC NS: nerves that connect to organs/glands
    • B. Cranial nerves – 12 pair
      * go in order from front to back
      1. olfactory nerves (I)
      Sensory nerves
      Transmit smell impulses
      2. optic nerves (II)
      Sensory nerves
      Transmit vision impulses
      3. oculomotor(III)
      Mostly motor nerves
      Transmit impulses to: adjust lens, adjust pupil, move eyelid, move eye
    • 4. trochlear (IV)
      Mostly motor nerves
      Transmit eye movement impulses
      5. trigeminal (V)
      Mixed
      Sensory:
      Transmit impulses from: tear glands, scalp, forehead, upper eyelids, teeth, lips, skin of face
      Motor:
      Transmit impulses of chewing
    • 6. Abducens (VI)
      Mostly motor
      Transmit impulses of eye movement
      7. facial (VII)
      Mixed
      Sensory:
      Transmit impulses of tongue/taste
      Motor:
      Facial expression, tear glands, salivary glands
      8. vestibulocochlear (VIII)
      Sensory nerves
      Transmit impulses for equilibrium and hearing
    • 9. glossopharyngeal (IX)
      Mixed
      Sensory:
      Pharynx, tonsils, tongue, neck artery
      Motor:
      Swallowing, salivary
      10. vagus (X)
      Mixed
      Sensory:
      Pharynx, larynx, esophagus, organs
      Motor:
      Speech, swallowing, heart, glands
    • 11. accessory (XI)
      Mostly motor
      Pharynx, larynx, neck, back
      12. hypoglossal (XII)
      Mostly motor
      Muscles that move tongue
    • D. Spinal Nerves
      31 pair
      Communicate impulses from spinal cord and arms, legs, neck, trunk
    • D. Autonomic Nervous System
      Regulates heart rate, BP, breathing rate, body temp
      Respond to emotional stress and strenuous physical activity
      1. sympathetic division
      Prepares body for emergency situations
      Initiates activation and secretion of adrenaline
      2. Parasympathetic division
      Active during ordinary conditions
      Restores body back to normal after stress
    • XI. Clinical Terms