CNS DEPRESSANTS

• Neuron

  Structural unit of the nervous system, also called nerve cells, unable to reproduce but able to regenerate lost dendrites and axons, consists of afferent (sensory) and efferent (motor) fibers
• Synapse


  Site of transmission of electric nerve impulses between two neurons or between a neuron and a gland or a muscle cell (effector)
• Ions


  Sodium or potassium action transmitters, maintained by the Na-K pump, cells communicate by releasing chemicals that are detected by target cells which can operate systemically or adjacent to other cells
• Ion Channels


  Integral proteins that span the cell membrane, may be open or closed via voltage-gated or ligand-gated mechanisms
• Resting Membrane Potential


  Inside of the cells is relatively negative as compared from the outside which establishes an electrical potential, depolarization is stimulation of a neuron and repolarization is the cell returning to the resting membrane potential
• Action Potential


  Nerve cells send messages by electrical impulses, transmission of information between nerves, glands, and muscles is chemical
• Neurotransmitter


  A chemical that is released by the nerve axon (presynaptic nerve), can be excitatory or inhibitory
• Synaptic Transmission


  1. Synthesis of neurotransmitter

  2. Uptake into storage vesicles

  3. Release by an action potential

  4. Diffusion across the synaptic cleft

  5. Combination with a receptor

  6. Activation of second messengers with post synaptic nerve

  7. Change of permeability of postsynaptic membrane to one or more ions

  8. IPSP/EPSP
• Responses of a Postsynaptic Cell

  Gland secretes hormone, muscle cells have an action potential, muscle contracts
• Types of Neurotransmitters


  • Acetylcholine
  • Norepinephrine & Epinephrine
  • Dopamine
  • Gamma-Aminobutyric Acid (GABA)
  • Serotonin
• Termination of Neurotransmitters


  Inactivation by an enzyme, diffusion out of the synaptic cleft, reuptake into the presynaptic nerve
• Parts of the Brain

  • Hind Brain
  • Cranial Nerves
  • Midbrain
  • Thalamus
  • Hypothalamus
  • Limbic System
  • Forebrain
• Functions of the Central Nervous System

  • Sensory, Motor, Intellectual and Emotional
• Sleep


  State of unconsciousness, normal sleep is cyclic and repetitive, patient can be aroused, important to maintain body function, phases are Non-Rapid Eye Movement (NREM) and Rapid Eye Movement (REM)
• Stages of NREM Sleep

  • Stage I
  • Stage II
  • Stage III
  • Stage IV
• Insomnia


  Inability to sleep, not a disease but a symptom, can be initial, intermittent, or terminal, can be transient, short-term, or chronic
• Anxiety


  Unpleasant feeling of tension, fear, or nervousness in response to an environmental stimulus, whether real or imaginary, accompanied by signs and symptoms of sympathetic stress reactions
• Central Nervous System Depressants

  Anxiolytics prevent feeling of tension or fear, sedatives calm the patient and make them unaware of the environment, hypnotics help people fall asleep, minor tranquilizers can produce a state of tranquility in an anxious client
• Sedative-Hypnotics


  Used to induce deep sleep, low doses calm the CNS without inducing sleep, high doses calm the CNS to the point of causing sleep, suppress REM sleep and dreams
• Mechanism of Action: Sedative-Hypnotics


  Site of action is the brainstem reticular formation and cerebral cortex, promote gamma-aminobutyric acid (GABA) which inhibits nerve impulses in the cerebral cortex
• Barbiturates


  First introduced in 1903 as a standard agent for insomnia and sedation, highly addictive with a narrow therapeutic index, can cause respiratory depression, rarely used today due to the safety and efficacy of benzodiazepines
• Sedative-hypnotics are a vital part of CNS depressants
• Barbiturates are used for their highly addictive effect and are for short-term use only
• Barbiturates


  • Reversibly depress activity of excitable tissue
  • Have variable depressive effects
  • Suppress REM sleep
• Benzodiazepines


  Most frequently prescribed sedative-hypnotics, classified as either Sedative Hypnotic or Anxiolytic
• Azapirones


  Anti-anxiety agent, partial serotonin and dopamine agonists, interacts in the midbrain, no effect on GABA receptors, lower sedative properties
• Nonbarbiturate/Nonbenzodiazepine


  Miscellaneous Sedative-Hypnotic Agents, cause CNS Depression, H1 Blockers, Benzodiazepine Receptor agonists
• Nonbarbiturate/Nonbenzodiazepine


  • Melatonin, Ramelton, Valerian
• Seizures are symptoms of abnormality in the nerve centers of the brain, brief abnormal electrical activity, can be convulsive or non-convulsive
• Convulsion


  Involuntary spasmodic contractions of any or all voluntary muscles throughout the body
• Epilepsy


  Chronic, recurrent pattern of seizures, most common of all neurologic disorders
• Primary (Idiopathic) Epilepsy


  Cause cannot be determined, more than 50% of epilepsy cases
• Secondary Epilepsy


  Distinct cause identified, such as trauma, infection, cerebrovascular disorder
• Generalized Seizure


  Affecting both hemispheres, with loss of consciousness, can be convulsive and non-convulsive
• Partial Seizure


  Localized area in one hemisphere, can be simple or complex, can lead to secondary generalization
• Generalized Convulsive Seizures


  • Tonic-Clonic (Grand Mal) Seizures, Atonic or Akinetic Seizures, Myoclonic Seizures
• Phases of Tonic-Clonic Seizures

  1. Tonic Phase: Sudden intense contractions, fall, loss of consciousness, rigid, apnea and cyanosis

  2. Clonic Phase: Bilateral symmetrical jerks, becomes more violent, bites tongue, incontinence

  3. Recovery Phase: Flaccid paralysis and sleep, post ictal state
• Generalized Nonconvulsive Seizures


  Absence (Petit Mal) Seizures, Partial (Localized) Seizures
• Anti-Epileptic Drugs


  Drugs used to treat the abnormal and excessive energy bursts in the brain that are characteristic of epilepsy
• The primary concern with seizures is safety, the airway is second. Employ seizure precautions, do not restrain, put in side-lying position after seizures to avoid aspiration