Chapter Objectives

• 10.01 Describe the functions and structures of the nervous system.
• 10.02 Identify the major divisions of the nervous system, and describe the structures of each by location and function.
• 10.03 Identify the medical specialists who treat disorders of the nervous system and mental health disorders.
• 10.04 Recognize, define, spell, and pronounce the primary terms related to the pathology and the diagnostic and treatment procedures of the nervous system.
• 10.05 Recognize, define, spell, and pronounce the primary terms related to the pathology and the diagnostic and treatment procedures of mental health disorders.

Functions of the Nervous System

• Nervous system overview: central role in controlling and coordinating all bodily activities.
• Brain as its center: coordinates and controls all bodily activities.
• Brain function is essential for life; when it ceases functioning, the body can no longer live on its own.

Structures of the Nervous System

Divisions of the Nervous System

• Central nervous system (CNS)
  • Includes the brain and spinal cord
  • Functions: to receive and process information and to regulate all bodily activity
• Peripheral nervous system (PNS)
  • 12 pairs of cranial nerves extending from the brain
  • 31 pairs of peripheral spinal nerves extending outward from the spinal cord
  • Function: to transmit nerve signals to and from the CNS
• Structural organization of the CNS and PNS depicted in standard diagrams

The Nerves

• Bundles of neurons that connect the brain and spinal cord with other body parts
• Tract: bundle or group of nerve fibers in the brain or spinal cord
  • Ascending nerve tracts: carry impulses toward the brain
  • Descending nerve tracts: carry impulses away from the brain
• Ganglion: nerve center outside the CNS
• Innervation: supply of nerves to a specific body part
• Plexus: network of intersecting spinal nerves
• Receptors: sites in sensory organs that receive external stimulation
• Stimulus: anything that excites (activates) a nerve and causes an impulse

The Neurons

• Basic cells of the nervous system; allow body parts to communicate with each other
• Three types of neurons (ACE and SAM):
  • Afferent → Sensory neurons
  • Connecting → Associative neurons
  • Efferent → Motor neurons

Neuron Structure and Neurotransmitters

• Neuron parts: Dendrites, Axons, Terminal end fibers, Synapses
  • Dendrites: receive impulses; conduct them to the cell body
  • Axons: conduct impulses away from nerve cells
  • Terminal end fibers: branching fibers; lead impulse from axon to synapse
  • Synapses: space between neurons
• Neurotransmitters: chemical substances that allow messages to cross from a synapse to a target receptor
  • Examples: acetylcholine, dopamine, endorphins, norepinephrine, serotonin
• Visual note: two neuron types shown — (A) Efferent (motor) neurons and (B) Afferent (sensory) neurons

Glial Cells and Myelin

• Glial cells provide support and protection for neurons
• Four main functions:
  • Surround neurons and hold them in place
  • Supply nutrients and oxygen to neurons
  • Insulate one neuron from another
  • Destroy and remove dead neurons
• Myelin sheath: protective covering made of glial cells
  • White matter of the brain: myelinated nerve fibers
  • Gray matter of the brain: unmyelinated nerve fibers

The Central Nervous System (CNS) – Membranes and CSF

• Meninges: membranes enclosing the brain and spinal cord
  • Dura mater: thick, tough, outermost membrane
  • Arachnoid membrane: resembles a spider web; second layer
  • Pia mater: closest layer to brain and spinal cord
• Cerebrospinal fluid (CSF): spinal fluid produced by special capillaries
  • Functions: cools and cushions the brain and spinal cord; nourishes brain and spinal cord
• Cross-section notes: meninges shown; CSF shown in purple in diagrams

The Parts of the Brain

• Cerebrum: largest uppermost portion; cerebral hemispheres (left and right); cerebral lobes (frontal, parietal, occipital, temporal)
• Thalamus: located below the cerebrum
• Hypothalamus: located below the thalamus
• Cerebellum: located at the back of the head below the posterior portion of the cerebrum
• Brainstem: stalk-like portion; connects cerebral hemispheres with the spinal cord; three parts: midbrain, pons, medulla oblongata
• Spinal cord: long, fragile, tube-like structure; pathway to and from the brain
• Exterior view note: left lateral view shows the four lobes of the cerebrum along with the medulla oblongata and the cerebellum; cerebral cortex is the outer layer of the cerebrum

The Peripheral Nervous System (PNS)

• Specialized peripheral nerves:
  • Autonomic nerve fibers
  • Sensory nerve fibers
  • Somatic nerve fibers (motor nerve fibers)
• Cranial nerves: 12 pairs identified by Roman numerals; named for area or function they serve
• Cranial nerves are identified with Roman numerals and named for their area or function
• Peripheral spinal nerves: 31 pairs
  • Cervical nerves: C1–C8
  • Thoracic nerves: T1–T{12}
  • Lumbar nerves: L1–L5
  • Sacral nerves: S1–S5
• Most spinal cord plexuses are named for the corresponding vertebrae; within each spinal region, nerves are referred to by number

The Autonomic Nervous System

• Two divisions:
  • Sympathetic nerves: prepare body for emergencies and stress; increase respiratory rate, heart rate, and blood flow to muscles; aroused as part of fight-or-flight
  • Parasympathetic nerves: return body to normal after a response to stress; maintain normal body functions during ordinary circumstances

Medical Specialties Related to the Nervous System and Mental Health

• Anesthesiologist: physician specializing in administering anesthesia
• Anesthetist: nonphysician specializing in administering anesthesia
• Neurologist: physician specializing in the nervous system
• Neurosurgeon: physician specializing in surgery of the nervous system
• Psychiatrist: physician specializing in chemical dependencies, emotional problems, and mental illness
• Psychologist: doctoral degree (PhD or PsyD); not a medical doctor; evaluates and treats emotional problems and mental illness
• Social worker: trained therapist, usually with a Master of Social Work (MSW)

Pathology of the Nervous System (overview of 14 subsections)

• Conditions of the head and meninges (1 of 14)
  • Cephalalgia (headache): pain in the head
  • Migraine headache: throbbing pain on one side; may be accompanied by nausea, vomiting, light/sound sensitivity
  • Cluster headaches: intensely painful; repeated in clusters
  • Encephalocele (craniocele): congenital herniation of brain tissue through skull
  • Meningocele: congenital herniation of meninges through skull or spinal column
  • Hydrocephalus: excess CSF accumulates in brain ventricles
  • Meningioma: common, slow-growing, usually benign meninges tumor
  • Meningitis (infectious meningitis): inflammation of meninges; caused by bacterial or viral infection
• Disorders of the brain (2 of 14)
  • Chiari malformation: cerebellum extends into spinal canal; congenital
  • Encephalitis: inflammation of brain
  • Reye’s syndrome (RS): in children; can follow a viral illness treated with aspirin
  • Tetanus (lockjaw): CNS infection caused by toxin from tetanus bacteria
  • Tourette syndrome (TS): neurological disorder with involuntary tics, grunts, utterances
  • Mild cognitive impairment: decline from normal function; short-term memory loss
  • Dementia: slowly progressive decline in mental abilities
  • Vascular dementia: dementia due to stroke or restricted blood flow
• Neurodegenerative diseases (3 of 14)
  • Alzheimer’s disease (AD): leading form of dementia; group of disorders
  • Huntington’s disease: genetic disorder
  • Parkinson’s disease (PD): chronic, degenerative CNS disorder
  • Tremor: repetitive, involuntary muscle movement
  • Lewy body dementia: abnormal proteins interfere with brain cell function
  • Amyotrophic lateral sclerosis (ALS) (Lou Gehrig’s disease): rapidly progressive; attacks nerve cells controlling voluntary muscles
• Brain injuries (4 of 14)
  • Amnesia: total or partial inability to recall past experiences
  • Concussion: shaking/jarring of brain
  • Cerebral contusion: bruising of brain tissue from impact
  • Cranial hematoma: collection of blood in brain tissues (epidural, subdural)
• Traumatic brain injury (TBI) (5 of 14)
  • Blow to the head or penetrating head injury damaging brain
  • Effects range from mild to severe
  • Coup: injury at the point of impact
  • Contrecoup (counterblow): injury opposite the impact
  • Shaken baby syndrome: results from violent shaking; Coup and contrecoup TBIs
• Levels of Consciousness (LOC) (6 of 14)
  • Conscious: awake, alert, aware, responsive
  • Unconscious: unable to respond to stimuli
  • Altered levels of consciousness (ALOC):
  • Lethargy: drowsiness/listlessness
  • Stupor: unresponsive state; aroused only briefly
  • Syncope: fainting; transient loss of consciousness due to decreased brain blood flow
  • Coma: profound unconsciousness
  • Persistent vegetative state: coma with sleep-wake cycles; unconscious when appearing awake
  • Delirium: acute confusion, disorientation, memory problems, agitation, hallucinations
• Brain tumor (7 of 14)
  • Abnormal growth inside skull
  • Glioblastoma (glioblastoma multiforme): fast-growing malignant tumor
  • Malignant tumor: destroys brain tissue
  • Benign brain tumor: does not invade brain tissue but can increase intracranial pressure
  • Intracranial pressure (ICP): pressure inside the skull
• Strokes (8 of 14)
  • Cerebrovascular accident (CVA): brain damage from disrupted blood flow
  • FAST: Facial droop, Arm drift, Speech abnormality, Time (next steps if detected)
  • Ischemic stroke: blockage or narrowing of an artery in the brain; most common in older people
  • Transient ischemic attack (TIA): mini-stroke; temporary interruption of blood flow
  • Aphasia: loss of ability to speak, write, or comprehend words
  • Location of CVA damage depends on the side of the brain affected
• Hemorrhagic stroke (9 of 14; often discussed as a type of stroke)
  • Bleed: rupture of a blood vessel in brain
  • Intracerebral and subarachnoid types
  • Arteriovenous malformation (AVM): abnormal connection between arteries and veins
  • In hemorrhagic stroke, rupture reduces blood flow to the affected brain area; infarct describes dead tissue from lack of blood (referenced to Chapter 5)
• Sleep disorders (11 of 14)
  • Insomnia: persistent inability to sleep
  • Narcolepsy: sudden, uncontrollable episodes of falling asleep during day
  • Sleep deprivation: lack of restorative sleep; causes physical or psychiatric symptoms
  • Parasomnia: abnormal events during sleep or awakening
  • Somnambulism (sleepwalking): performing activities while asleep
• Spinal cord conditions (12 of 14)
  • Myelitis: inflammation of the spinal cord
  • Acute flaccid myelitis (AFM): inflammation of spinal cord
  • Poliomyelitis (Polio): viral infection of brainstem and spinal cord
  • Myelosis: tumor of the spinal cord
  • Radiculitis (pinched nerve): cervical or lumbar radiculopathy
  • Multiple sclerosis (MS): autoimmune; demyelination and inflammation
• Nerves and related disorders (13 of 14)
  • Bell’s palsy: temporary paralysis of the seventh cranial nerve; affects one side of face
  • Guillain–Barré syndrome (GBS): inflammation of myelin sheath of peripheral nerves
  • Neuritis: inflammation of a nerve; pain and possible loss of function
  • Sciatica: inflammation of the sciatic nerve
  • Trigeminal neuralgia: chronic pain condition of the fifth cranial nerve
• Cerebral palsy (within Nerves section)
  • Group of disorders due to brain damage; poor muscle control, spasticity, speech defects, other neurologic issues
  • Usually caused by brain injury during pregnancy, birth, or shortly after birth
• Epilepsy and seizures (14 of 14)
  • Epilepsy: chronic neurological condition with recurrent seizures
  • Seizure (Sz): sudden surge of electrical activity in the brain; short-term effects on feelings/behavior
  • Types of seizures:
  • Tonic–clonic (grand mal): involves entire body
  • Absence (petit mal): brief disturbance in brain function; loss of awareness
  • Focal (partial): repetitive muscle movements
  • Febrile seizure: occurs in infants/young children
  • SUDEP: sudden unexpected death in epilepsy
• Abnormal sensations (15 of 14 would be out of sequence, but included in the same pathology section)
  • Causalgia: burning pain after nerve injury
  • Complex regional pain syndrome (CRPS): chronic nerve pain in one limb
  • Hyperesthesia: excessive sensitivity to touch, pain, or other stimuli
  • Paresthesia: burning or prickling sensation without physical cause
• Peripheral neuropathy (16 of 14 in sequence but included here)
  • Neuropathy: disease/damage to a nerve
  • Mononeuropathy: damage to a single peripheral nerve (e.g., carpal tunnel)
  • Polyneuropathy: damage to multiple peripheral nerves
• Neurological disorders (Restless Legs Syndrome) (17 of 14 in sequence but included here)
  • Restless legs syndrome (RLS): uncomfortable leg sensations with urge to move

Diagnostic Procedures of the Nervous System

• Neuroimaging tools:
  • Magnetic resonance imaging (MRI)
  • Magnetic resonance angiography (MRA)
  • Computed tomography (CT)
• Diagnostic techniques:
  • Functional MRI (fMRI): detects changes in blood flow in the brain
  • Carotid ultrasonography: ultrasound study of the carotid artery
  • Electroencephalography (EEG): records electrical activity of the brain
  • Myelography: fluoroscopic and CT study
  • Electromyography (EMG): uses electrodes taped to or inserted into the skin
  • Lumbar puncture (LP, spinal tap): obtaining a sample of cerebrospinal fluid

Treatment Procedures of the Nervous System

• Sedative and Hypnotic Medications
  • Hypnotic: depresses CNS and typically induces sleep
  • Anticonvulsant: prevents seizures (e.g., epilepsy)
  • Barbiturates: provide calming or depressant effect
  • Sedative: depresses CNS; induces calm without sleep
  • Sedation: effect produced by a sedative
• Anesthesia (types and definitions)
• Anesthetic types:
  • Epidural anesthesia: injected into epidural space in lumbar or sacral region
  • General anesthesia: total loss of body sensation and consciousness
  • Conscious sedation: short-acting, shallow anesthesia; patient still breathes and responds
  • Local anesthesia: loss of sensation in a limited area
  • Regional anesthesia: numbs a larger area than local
  • Spinal anesthesia (spinal block): numbness from toes to waist or lower chest
  • Topical anesthesia: numbs surface tissue
• Clinical applications and notes:
  • Epidural anesthesia during childbirth numbs nerves from uterus and birth passage without stopping labor

Treatment Procedures of the Nervous System (Continued)

• Brain interventions and nerve procedures:
  • Deep brain stimulation (DBS): stimulator implanted near the collar bone
  • Stereotactic radiosurgery (SRS): three-dimensional coordinate system for precise targeting
  • Gamma Knife surgery: radiation treatment for brain tumors
  • Electroconvulsive therapy (ECT/electroshock therapy): small electric current passed through the brain
  • Lobectomy: removal of a portion of the brain
  • Thalamotomy: incision into the thalamus to destroy brain cells
  • Transcranial magnetic stimulation (TMS): electromagnetic pulses alter brain electrical pathways
• Nerve-targeted procedures:
  • Radiofrequency ablation (RFA, rhizotomy): relieves nerve pain by burning nerves
  • Neurotomy: surgical division or dissection (cutting) of a nerve; relieves pain or suppresses tremors

Mental Health Disorders (Overview)

• Mental Health Disorders (overview across 10 categories)
• Anxiety disorders: excessive, irrational dread; disproportionate fear
• Generalized anxiety disorder (GAD): chronic, excessive worrying
• Panic attack: sudden fear without danger
• Panic disorder: fear of panic attacks
• Post-traumatic stress disorder (PTSD): aftermath of war, disasters, trauma, or life-threatening experiences
• Phobias: persistent irrational fear of specific things or situations (examples: acrophobia, agoraphobia, claustrophobia)

Obsessive-Compulsive–Related Disorders and Neurodevelopmental Disorders

• Obsessive-compulsive disorder (OCD): recurrent obsessions and/or compulsions
• Hoarding disorder: excessive accumulation of belongings; potential safety/ sanitation hazards
• Neurodevelopmental disorders:
  • Attention deficit/hyperactivity disorder (ADHD)
  • Dyslexia: developmental reading disorder
  • Learning disabilities (intellectual developmental disorder): intellectual disability
  • Autism spectrum disorder (ASD)
  • Asperger's syndrome: subgroup of autism spectrum
• Example caption: therapist working with a boy with autism to develop communication skills

Dissociative, Disruptive, and Mood Disorders

• Dissociative disorders: dissociative identity disorder (DID) – formerly multiple personality disorder; two or more distinct personalities
• Disruptive and impulse-control disorders:
  • Kleptomania: recurrent stealing not for personal use or value
  • Pyromania: repeated deliberate fire setting
  • Oppositional defiant disorder (ODD): angry, uncooperative, disruptive behavior toward authority figures

Bipolar and Depressive Disorders

• Bipolar disorder: cycles of mood changes between highs and lows
• Manic behavior: abnormally elevated mood; euphoria
• Depression: lethargy and sadness; loss of interest or pleasure
• Persistent depressive disorder (dysthymia): chronic low-grade depression
• Double depression: major depressive episode in the context of persistent depressive disorder
• Disruptive mood dysregulation disorder (DMDD): in children with frequent severe temper outbursts; persistently irritable
• Seasonal affective disorder (SAD): depression related to less daylight in winter

Eating Disorders and Body Image

• Anorexia nervosa: false perception of body appearance; fear of weight gain; voluntary starvation
• Bulimia nervosa: binge eating followed by induced vomiting; excessive exercise; laxative/diuretic misuse
• Binge eating disorder (BED): recurrent binge eating with loss of control and guilt/shame
• Note: Anorexia nervosa characterized by false body image perception and weight loss behaviors

Personality and Psychotic Disorders

• Antisocial personality disorder
• Borderline personality disorder: impulsive actions; self-harm risk
• Narcissistic personality disorder: excessive self-focus; lack of empathy
• Psychotic disorders:
  • Catatonic behavior: nonresponsive, stupor, fixed posture
  • Delusion: false personal belief despite evidence
  • Hallucination: sensory perception without external stimuli
  • Schizophrenia: psychotic disorder with withdrawal from reality
  • Schizoaffective disorder: schizophrenia symptoms with bipolar or depressive symptoms

Somatic Symptom and Related Disorders

• Somatic symptom disorders:
  • Illness anxiety disorder: excessive anxiety about having a serious illness
  • Factitious disorder: feigning illness; not actually sick
  • Factitious disorder by proxy: causing symptoms in another person (typically child)
  • Functional neurologic disorders: neurologic symptoms without a physical cause
  • Conversion disorder: changes in function triggered by psychological factors
  • Malingering: intentional fabrication or exaggeration of symptoms for external gain

Substance-Related and Gender-Identity Considerations

• Substance-related disorders:
  • Alcoholism
  • Delirium tremens (DTs)
  • Drug abuse
  • Drug overdose
  • Narcan®: brand-name antidote for opioid overdose
  • Methadone: opioid agonist used to treat addiction
• Gender identity:
  • Dysphoria: incongruence between experienced gender and birth sex appears to start early
  • Transgender: gender identity does not match sex assigned at birth

Medications to Treat Mental Disorders

• Psychotropic drugs:
  • Antidepressants: relieve depression
  • Antipsychotic drugs (neuroleptics): treat symptoms of severe disorders
  • Anxiolytic drugs (antianxiety/tranquilizers): relieve anxiety and reduce tension
  • Mood-stabilizing drugs: treat mood instability and bipolar disorders
  • Stimulants: increase brain activity to improve concentration and wakefulness

Psychological Therapies for Mental Disorders

• Psychoanalysis: gaining insight into feelings and behavior to overcome disorders
• EMDR (Eye Movement Desensitization and Reprocessing): evidence-based treatment for PTSD
• Behavioral therapy: replace problem behaviors with appropriate behaviors
• Cognitive behavioral therapy (CBT): change thoughts to affect emotions and actions
• Hypnotherapy: treatment for pain and anxiety; used for behavior modification
• CBT summary: focus on changing thoughts that affect emotions and actions

Abbreviations Related to the Nervous System

• Reference Table 10.4 lists abbreviations used in this chapter
• Examples:
  • AD = Alzheimer’s disease
  • CP = cerebral palsy
  • EEG = electroencephalography
  • MS = multiple sclerosis
  • OCD = obsessive-compulsive disorder
  • TIA = transient ischemic attack