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Chapter 12 the nervous system
 

Chapter 12 the nervous system

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    Chapter 12 the nervous system Chapter 12 the nervous system Presentation Transcript

    • Chapter 12: a glance at the nervous system
      By Shawna Miller
    • Functions and organs
      The functions of the nervous system are to coordinate and control body functions.
      Receives sensory output
      Makes decisions
      Orders body responses
      The organs of the nervous system are:
      Brain
      Nerves
      Spinal cord
    • Nervous tissue
      Consists of two cell types
      Neurons- individual nerve cells
      Dendrite- branched projections, receive impulses
      Nerve cell body- contains nucleus/other organelles
      Axon-projection from the nerve cell body, conducts electrical impulses to destination
      The point which the axon of one neuron meets the dendrite of another neuron is called a synapse.
      The gap between two neurons is called a synaptic cleft.
      The electrical impulses need help from chemical messengers caller neurotransmitters.
      Different neuroglial cells are in nervous tissue
      Some produce myelin-a fatty substance which acts like insulation for axons
      They do not conduct electrical impulses
    • Central nervous system
      Receives impulses from all over the body.
      The system is made of grey and white matter.
      Grey matter is uncovered cell bodies and dendrites.
      White matter is myelinated nerve fibers.
      The myelin sheath makes the nervous tissue look white.
      Tracts are bundles of nerve fibers that connect parts of the CNS.
      Meninges are what the CNS is encased and protected by. There are three of these membranes.
    • The Brain
      One of the largest organs in the body.
      Center for thought, judgement, memory, and emotion.
      Four sections:
      Cerebrum- largest section in the upper part of the brain. It processes problem solving, language, thoughts, and memory. It has an outer layer called the cerebral cortex which is made up of folds of grey matter.
      Diencephalon- below the cerebrum contains the thalmus and hypothalmus
      Thalmus- center for relaying impulses for eyes, ears, and skin to the cerebrum. What our pain perception is controlled by.
      Hypothalmus- below thalmus, controls body temperature, sleep appetite, and emotions.
      Cerebellum- second largest section, beneath the posterior part of the cerebrum. Helps to maintain body movements and maintain balance.
      Brain stem : has three parts
      Mid brain- acts as pathway between brain and spinal cord
      Pons- connects the cerebellum to rest of brain
      Medulla oblongata- most inferior portion of the brain; it connects the brain to the spinal cord
      A vital are that controls respiration, heart rate, and blood pressure
      Site where nerve tracts cross
      The brain has four interconnected cavities called ventricles. There is one in each hemisphere of the brain
      They contain CSF(cerebral spinal fluid) that protects the brain from shock/sudden movement to brain and spinal cord
    • A view of the brain
    • Spinal cord
      The spinal cord’s function is to provide a pathway for impulses traveling to and from the brain
      A column of nervous tissue that goes from the medulla oblongata down to the second level of the lumbar vertebra in the vertebral column
      Goes down to the center of the spinal cord in the central canal
      Outer portion is myelinated white matter- can be either ascending tracts(carrying sensory info to the brain) or descending tracts( carrying motor commands from the brain to a peripheral nerve
    • meninges
      Three layers of connective tissue membranes that surround the brain and spinal cord
      External to internal:
      Dura mater(tough mother)- tough fibrous sac around the CNS
      Subdural space- actual space between the dura mater and arachnoid layers
      Arachnoid layer(spiderlike)- thin, delicate layer attached to the pia mater by weblike filaments
      Subarachnoid space- space between the arachnoid and pia mater layers. It contains cerebrospinal fluid which cushions the brain from the outside
      Pia mater(soft mother)- innermost membrane layer which is applied directly to the spinal cord and surface of the brain
    • Peripheral nervous system
      Includes 12 pairs of cranial nerves and 31 pairs of spinal nerves
      Where the nerve originates determines if it is cranial or spinal
      The point where either type is attached to the CNS is called the nerve root
      Afferent neurons(sensory neurons)- carry sensory info from a sensory receptor to the CNS
      Efferent neurons(motor neurons)- carry activity instructions from the CNS to muscles/glands out in the body
      Nerves of the peripheral nervous system are subdivided into two areas: the autonomic nervous system(ANS) and somatic nerves which each serve a different part of the body
      The nerve cell bodies of the neurons are grouped together in a knot-like mass, called a ganglion
    • Autonomic nervous system
      Involved with control of involuntary or unconscious bodily functions
      May increase or decrease activity of smooth muscles
      Is divided into two divisions
      Sympathetic branch- control the “fight or flight” reaction during stress or crisis. These nerves increase heart rate, dilate airways, increase blood pressure, inhibit digestion, and stimulate adrenaline production
      Parasympathetic- counterbalance for sympathetic, the “rest and digest” reaction. They lower heart rate, decrease blood pressure, and stimulate digestion
      Somatic nerves- serve the skin and skeletal muscles. Mainly involved with the conscious/voluntary activities of the body. Largest ones found in dermis of skin like touch, pressure and pain. Also carry motor commands to skeletal muscles
    • Common terms
      Cerebrospinal, meningitis, analgesia, aphasia, dysphasia, quadriplegia, neuropathy, encephalitis, electroencephalogram
    • Definitions
      Cerebrospinal- pertaining to the cerebrum and spine
      Meningitis- meninges inflammation
      Analgesia- absence of pain or sensation
      Aphasia- lack of speech
      Dysphagia- difficult speech
      Quadriplegia- paralysis of four
      Neuropathy- nerve disease
      Electroencephalogram(EEG)- record of brain’s activity
    • tests
      Brain scan-image of the brain taken after an injection of radioactive isotopes into the circulation
      Echoencephalography- record of the ultrasonic echoes of the brain
      Myelography- injection of radiopaque dye into the spinal cord
      Positron emission tomography- use of positive radionuclides to reconstruct brain sections
    • treatments
      Nerve block- injection of regional anesthetic to stop the passage of sensory/pain impulses along a nerve path
      Laminectomy- removal of a portion of a vertebra in order to relieve pressure on the spinal nerve
      Tractotomy- surgical interruption of a nerve tract in the spinal cord
    • Medications
      Analgesics- non narcotics to treat pain(aspirin, tylenol, aleve, ibuprofen)
      Anesthetics- drug that produces a loss of sensation or loss of consciousness( propofol, novocain, lidocaine, nembutal)
      Hypnotic- drug that promotes sleep(restoril, seconal, temazepam)
      Sedative- drug that has a relaxing or calming effect(amytal, butisol, amobarbital)