Pharmacology for Nurses Unit 9 Review: Nervous System Basics for Nurses

Key Concepts and Terminology

• Neurons specialized cells that transmit electrical and chemical signals throughout the nervous system
  • Consist of a cell body, dendrites, and an axon
  • Classified as sensory neurons, motor neurons, or interneurons based on their function
• Neurotransmitters chemical messengers released by neurons to communicate with other cells
  • Examples include acetylcholine, dopamine, serotonin, and norepinephrine
• Synapse junction between two neurons where neurotransmitters are released and received
• Action potential electrical impulse that travels along the axon of a neuron to transmit information
• Myelin sheath insulating layer surrounding axons that facilitates rapid signal transmission
  • Produced by Schwann cells in the peripheral nervous system and oligodendrocytes in the central nervous system
• Neuroplasticity ability of the nervous system to adapt and reorganize in response to experience or injury
• Neurodegenerative disorders progressive loss of structure or function of neurons (Alzheimer's disease, Parkinson's disease)

Anatomy and Structure of the Nervous System

• Central nervous system (CNS) consists of the brain and spinal cord
  • Brain divided into regions such as the cerebrum, cerebellum, and brainstem
  • Spinal cord extends from the brainstem and is protected by the vertebral column
• Peripheral nervous system (PNS) includes nerves that connect the CNS to the rest of the body
  • Divided into the somatic nervous system (voluntary control of skeletal muscles) and the autonomic nervous system (involuntary control of organs and glands)
• Autonomic nervous system further divided into the sympathetic and parasympathetic divisions
  • Sympathetic division responsible for "fight or flight" response
  • Parasympathetic division responsible for "rest and digest" functions
• Blood-brain barrier selective semipermeable barrier that separates the brain from the circulatory system
  • Protects the brain from toxins and pathogens while allowing essential nutrients to pass through
• Meninges protective membranes that cover the brain and spinal cord (dura mater, arachnoid mater, pia mater)
• Ventricles and cerebrospinal fluid (CSF)
  • Ventricles are cavities within the brain that produce and circulate CSF
  • CSF provides cushioning, nourishment, and waste removal for the brain and spinal cord

Neurotransmitters and Synaptic Transmission

• Neurotransmitter synthesis occurs in the cell body of the neuron
  • Precursor molecules are transported to the axon terminal, where they are packaged into synaptic vesicles
• Synaptic vesicles store neurotransmitters until they are released into the synaptic cleft
• Neurotransmitter release triggered by the arrival of an action potential at the axon terminal
  • Calcium ions enter the axon terminal, causing synaptic vesicles to fuse with the cell membrane and release their contents
• Neurotransmitters diffuse across the synaptic cleft and bind to receptors on the postsynaptic cell
  • Binding can result in excitation (depolarization) or inhibition (hyperpolarization) of the postsynaptic cell
• Neurotransmitter reuptake and degradation mechanisms terminate the signal
  • Reuptake involves the neurotransmitter being transported back into the presynaptic neuron or glial cells
  • Degradation occurs through enzymatic breakdown of the neurotransmitter in the synaptic cleft
• Neuromodulators substances that modify the effects of neurotransmitters (endorphins, cannabinoids)
• Neurotransmitter imbalances can contribute to various neurological and psychiatric disorders
  • Example: Dopamine deficiency in Parkinson's disease, serotonin imbalance in depression

Nervous System Functions and Pathways

• Sensory pathways transmit information from sensory receptors to the CNS for processing
  • Ascending pathways carry sensory information from the spinal cord to the brain
  • Examples include the spinothalamic tract (pain and temperature) and the dorsal column-medial lemniscus pathway (touch and proprioception)
• Motor pathways transmit signals from the CNS to effector organs (muscles and glands)
  • Descending pathways carry motor commands from the brain to the spinal cord
  • Examples include the corticospinal tract (voluntary movement) and the reticulospinal tract (posture and locomotion)
• Reflex arcs simple neural circuits that allow rapid, automatic responses to stimuli
  • Involve sensory neurons, interneurons, and motor neurons
  • Examples include the knee-jerk reflex and the withdrawal reflex
• Limbic system group of brain structures involved in emotion, motivation, and memory formation
  • Includes the amygdala, hippocampus, and hypothalamus
• Basal ganglia group of subcortical nuclei involved in motor control, learning, and decision-making
  • Includes the striatum, globus pallidus, and substantia nigra
• Cerebellum region of the brain responsible for coordination, balance, and fine motor control
• Autonomic nervous system regulates involuntary functions such as heart rate, blood pressure, and digestion
  • Sympathetic division increases arousal and prepares the body for action
  • Parasympathetic division promotes rest and restoration

Common Neurological Disorders

• Alzheimer's disease progressive neurodegenerative disorder characterized by memory loss and cognitive decline
  • Associated with the accumulation of amyloid plaques and neurofibrillary tangles in the brain
• Parkinson's disease movement disorder caused by the loss of dopamine-producing neurons in the substantia nigra
  • Symptoms include tremor, rigidity, bradykinesia (slowness of movement), and postural instability
• Multiple sclerosis (MS) autoimmune disorder that attacks the myelin sheath, causing inflammation and demyelination
  • Can lead to a wide range of symptoms, including muscle weakness, sensory disturbances, and cognitive impairment
• Epilepsy neurological disorder characterized by recurrent, unprovoked seizures
  • Seizures result from abnormal, excessive, or synchronous neuronal activity in the brain
• Stroke sudden disruption of blood supply to the brain, causing damage to brain tissue
  • Can be ischemic (caused by a blockage) or hemorrhagic (caused by a bleed)
• Migraine recurrent headache disorder often accompanied by sensory disturbances (aura) and nausea
  • Believed to involve changes in brain chemistry and blood vessel function
• Amyotrophic lateral sclerosis (ALS) progressive neurodegenerative disorder affecting motor neurons
  • Leads to muscle weakness, atrophy, and eventual paralysis
• Traumatic brain injury (TBI) damage to the brain caused by an external force (concussion, contusion, diffuse axonal injury)

Pharmacological Interventions in Neurology

• Acetylcholinesterase inhibitors (donepezil, rivastigmine) used to treat Alzheimer's disease
  • Increase the availability of acetylcholine in the brain, which can improve cognitive function
• Dopamine agonists (levodopa, ropinirole) used to treat Parkinson's disease
  • Mimic the effects of dopamine or stimulate dopamine receptors to improve motor function
• Beta interferons (interferon beta-1a, interferon beta-1b) used to treat multiple sclerosis
  • Modulate the immune system to reduce inflammation and slow the progression of the disease
• Antiepileptic drugs (carbamazepine, valproic acid) used to control seizures in epilepsy
  • Work by various mechanisms to reduce neuronal excitability and prevent seizure activity
• Thrombolytics (alteplase) used to treat acute ischemic stroke
  • Break down blood clots to restore blood flow to the affected area of the brain
• Triptans (sumatriptan, rizatriptan) used to treat acute migraine attacks
  • Bind to serotonin receptors and cause vasoconstriction, reducing inflammation and pain
• Riluzole used to slow the progression of ALS
  • Modulates glutamate neurotransmission to reduce excitotoxicity and protect motor neurons
• Neuroprotective agents (amantadine, progesterone) used to minimize secondary damage after TBI
  • Reduce inflammation, oxidative stress, and excitotoxicity to promote neuronal survival and recovery

Nursing Considerations and Patient Care

• Assess neurological function using tools such as the Glasgow Coma Scale (GCS) and the National Institutes of Health Stroke Scale (NIHSS)
• Monitor vital signs, including blood pressure, heart rate, and respiratory rate
  • Ensure adequate oxygenation and perfusion to the brain
• Administer medications as prescribed and monitor for side effects
  • Educate patients and caregivers about proper medication use and potential adverse reactions
• Provide wound care and pressure ulcer prevention for patients with impaired mobility
  • Use specialized mattresses, cushions, and repositioning techniques to reduce the risk of skin breakdown
• Assist with activities of daily living (ADLs) and promote independence as appropriate
  • Encourage the use of adaptive equipment and techniques to maintain function and quality of life
• Offer emotional support and resources for patients and families coping with neurological disorders
  • Connect them with support groups, counseling services, and community resources
• Collaborate with interdisciplinary team members (neurologists, physical therapists, occupational therapists, speech therapists) to provide comprehensive care
• Educate patients and caregivers about the disease process, treatment options, and self-care strategies
  • Provide written materials and demonstrate techniques for managing symptoms and promoting wellness
• Advocate for patients' rights and preferences in decision-making and goal-setting
  • Respect advance directives and facilitate discussions about end-of-life care when appropriate

Clinical Applications and Case Studies

• Case study: A 75-year-old woman presents with gradually worsening memory loss and difficulty performing familiar tasks. She is diagnosed with Alzheimer's disease and started on donepezil.
  • Nursing interventions: Assess cognitive function using tools like the Mini-Mental State Exam (MMSE), monitor for side effects of medication, provide support and education for the patient and family, and promote a safe and stimulating environment.
• Case study: A 62-year-old man with a history of hypertension and high cholesterol experiences sudden weakness on the left side of his body and slurred speech. He is diagnosed with an acute ischemic stroke and receives alteplase.
  • Nursing interventions: Perform a rapid neurological assessment using the NIHSS, monitor for signs of hemorrhagic transformation, maintain blood pressure within target range, and initiate early rehabilitation to maximize functional recovery.
• Case study: A 28-year-old woman presents with episodes of involuntary muscle contractions and loss of consciousness. She is diagnosed with epilepsy and started on carbamazepine.
  • Nursing interventions: Educate the patient about seizure triggers and safety precautions, monitor drug levels and adjust dosage as needed, teach the patient and family how to respond to seizures, and provide emotional support and resources for coping with the diagnosis.
• Case study: A 55-year-old man with a history of depression reports a severe, throbbing headache accompanied by visual disturbances and nausea. He is diagnosed with a migraine and treated with sumatriptan.
  • Nursing interventions: Assess pain intensity and characteristics, administer medication as prescribed, provide a quiet and dark environment for rest, and educate the patient about lifestyle modifications and trigger avoidance.
• Case study: A 40-year-old woman presents with muscle weakness, numbness, and tingling in her legs. She is diagnosed with multiple sclerosis and started on interferon beta-1a.
  • Nursing interventions: Monitor for signs of disease progression and relapse, teach the patient how to self-administer injections, provide education about the disease process and treatment options, and encourage adherence to the treatment plan and follow-up appointments.