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UC 8022 Exam 5 practice questions

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127 Questions

What stimulates osteoblasts to produce osteocalcin?

Vitamin D

Which type of bone cells follow Wolfe's law, shaping bone according to its function?

Osteoblasts

What is the main function of osteocytes in bone maintenance?

Coordinating osteoblast and osteoclast functions

Which cells are responsible for resorbing bone by secreting hydrochloric acid and enzymes?

Osteoclasts

Which type of bone is also known as cortical bone?

Compact bone

What do osteoclasts attach to bone through in order to resorb it?

Integrins by podosomes

What is the basic structural unit in compact bone?

Haversian system

What type of bone lacks the Haversian system and is filled with red bone marrow?

Spongy bone

In bone repair, what phase replaces the callus with lamellar bone or trabecular bone?

Callus formation

Which type of joints are directly united to bone by dense fibrous connective tissue?

Fibrous joints

What type of joint is characterized by bones being united by a pad or disk of fibrocartilage?

Symphysis

Which phase involves the activation of the remodeling cycle and the resorption of old bone in the bone-remodeling process?

Activation

What is the main difference between a sprain and an avulsion?

Sprain is a tear in a ligament, while avulsion is a complete separation of a tendon or ligament from its bony attachment site.

Which condition is characterized by the inflammation of a bursa?

Bursitis

Myositis ossificans is known to happen more often in athletes due to:

Repetitive trauma to the same area before the muscle has appropriate time to heal

What is the classic triad of symptoms seen in Rhabdomyolysis?

Muscle pain, weakness, dark urine

Compartment syndrome is mainly characterized by:

Pain out of proportion to the injury and paresthesia

What is the defining characteristic of osteoporosis?

Imbalance of bone resorption and formation

What is the primary function of muscle in the human body?

To accomplish work

Which type of muscle fibers are known for slow contractions?

Type I fibers

What is the purpose of the Ryanodine receptors (RyRs) in muscle contraction?

Control calcium release

Which phase of muscle contraction involves the formation of a cross-bridge between actin and myosin filaments?

Contraction phase

In which type of muscle contraction does the muscle maintain a constant length as tension is increased?

Isometric contraction

What is the primary characteristic of an open or compound fracture?

Skin is broken

What distinguishes a transverse fracture from an oblique fracture?

Occurs straight across the bone

What is the result of an improper reduction during bone healing processes?

Nonunion

Which term describes an injury involving a tendon connecting muscle to bone?

Strain

What happens during sarcopenia, an age-related muscular change?

Decrease in muscle mass

What stimulates osteoblasts to produce osteocalcin?

Parathyroid hormone

Which cells are responsible for signaling osteoblasts and osteoclasts to form and reabsorb bone?

Osteocytes

What is the main function of integrins attached to podosomes in osteoclasts?

Binding to bone

What kind of cells cause resorption of bone by secreting hydrochloric acid and a protease enzyme?

Osteoclasts

During bone repair, what do osteoblasts synthesize that brings on the formation of new bone?

Osteoid

What property of bones does Wolfe's law refer to?

Bone shape being determined by function

What is the primary function of the Haversian system in compact bone?

Providing channels for bone cell communication

In bone repair, what role does hematoma formation play?

Initiates clot formation

What is the main difference between symphysis joints and synchondrosis joints?

Type of cartilage connecting bones

During the remodeling phase of bone repair, what happens at the endosteal surfaces?

Resorption of old bone

What differentiates fibrous joints from cartilaginous joints structurally?

Type of connective tissue uniting bones

What distinguishes synarthrosis joints from diarthrosis joints based on their mobility?

Type of movement allowed

What is the primary function of proteoglycans in cartilage?

Ensure a fluid film is present on cartilage

Which ion channels control calcium release in skeletal muscles?

Ryanodine receptors

What is the main function of the sarcolemma in muscle contraction?

Propagates impulse

What is the 'all or nothing' principle in muscle contraction?

Either a muscle fiber contracts completely or not at all

Which type of muscle contraction maintains a constant length as tension is increased?

Isometric contraction

What is the result of an open or compound fracture?

Skin is broken

During aging, what happens to muscle strength and bulk?

Decrease significantly

What occurs during a strain injury?

Tear or injury to a tendon

Which type of fractures runs parallel to the long axis of the bone?

Linear

What is the key difference between epicondylitis and tendinopathy?

Epicondylitis is inflammation of a tendon's attachment to bone, while tendinopathy refers to painful degradation of collagen fibers.

What differentiates Myositis Ossificans from Rhabdomyolysis?

Myositis Ossificans is a reaction to a bruise causing bone-like structure in the muscle, whereas Rhabdomyolysis results in rapid muscle breakdown.

What are the clinical manifestations of Compartment Syndrome?

Paresthesia, dark urine, and pulselessness

How does Rhabdomyolysis differ from Osteoporosis?

Rhabdomyolysis involves life-threatening muscle breakdown, while Osteoporosis is characterized by reduced bone mass and density.

What characterizes the pathophysiology of Avulsion injuries?

Complete separation of a tendon or ligament from its bony attachment site

How does Subluxation differ from Dislocation?

Subluxation leads to complete loss of motion in the joint, while Dislocation only partially loses connection between bones.

What skin lesion is characterized by an irregular red line produced by capillary dilation?

Wheal

Which of the following represents full-thickness skin loss involving damage to muscle, bone, or supporting structures?

Stage IV pressure ulcer

Which skin lesion is caused by excessive collagen formation during the healing process?

Keloid

What type of lesion presents as an elevated, circumscribed, and superficial lesion filled with serous fluid?

Vesicle

What skin manifestation results from a loss of part of the epidermis and appears as a depressed, moist, and glistening area?

Erosion

Which factor is NOT related to the mechanisms for crystal deposition in gout?

Increased uric acid secretion in the kidneys

What is the distinguishing characteristic between physiologic and pathologic contractures?

Cause of muscle fiber shortening

Which symptom is NOT typically seen in patients with fibromyalgia?

Nausea

What element does NOT contribute to disuse atrophy in muscles?

Increased protein synthesis

What is the primary source of muscle weakness in polymyositis?

Humoral dysregulation

What distinguishes osteosarcoma from chondrosarcoma based on their clinical manifestations?

Infiltration of spongy bone

Which factor contributes to the classification of a malignant bone tumor?

Prominent nucleolus

What differentiates fibrosarcoma from myelogenic tumors based on their characteristics?

Development from bone marrow cells

How does osteosarcoma differ from myelogenic tumors based on their location?

Frequently affects the metaphyses of long bones

What distinguishes chondrosarcoma from fibrosarcoma based on their composition?

Contains lobules of hyaline cartilage

What type of skin disorder is characterized by a T-cell autoimmune-mediated mechanism?

Psoriasis

Which skin condition involves acute recurring episodes with 'bull's eye' or target lesions?

Erythema Multiforme

Which skin disease is caused by circulating IgG autoantibodies directed against cell surface adhesion molecules?

Pemphigus

Which skin disorder involves a butterfly pattern over the nose and cheeks and can lead to systemic lupus erythematosus?

Discoid Lupus Erythematosus

Which skin condition involves involvement of T cells, adhesion molecules, inflammatory cytokines, and antigen-presenting cells?

Lichen Planus

Which skin infection is caused by candida albicans and is normally found on skin, in the gastrointestinal tract, and in the vagina?

Candidiasis

What skin infection is characterized by cauliflower-like lesions occurring in moist areas such as the glans of the penis, vulva, and anus, and is highly contagious and sexually transmitted?

Warts

Which viral infection presents with initial pain and paresthesia localized to a dermatome, followed by vesicular eruptions along specific dermatome areas like the face, neck, or lower back?

Chickenpox

What characterizes cellulitis as an infection of the skin?

Infection of dermis and subcutaneous tissue

What skin infection is a rapidly spreading inflammation starting in the fascia, muscles, and subcutaneous fat with subsequent necrosis of the overlying skin?

Necrotizing Fasciitis

Which factor contributes to the progression of albicans from a commensal organism to a pathogen?

Systemic administration of antibiotics

What is the main cause of the thin-walled pustule producing a whitish-yellow, curdlike substance?

Histamine release causing endothelial cell contraction

What distinguishes ticks from other insects in terms of feeding behavior?

Releasing toxins during feeding

Which gene mutation is associated with Squamous Cell Carcinoma of the skin?

TP53

How does Kaposi Sarcoma primarily manifest on the skin?

Purple-brown macules progressing into nodules

Which type of cells line the CSF-filled cavities of the CNS?

Ependymal cells

What is the term for the degeneration of a nerve fiber separated from its nutritive source by injury or disease?

Wallerian degeneration

What is the process where myelin sheath reforms into Schwann cells after nerve injury?

Schwann cell remyelination

Where are neurotransmitters stored before release across the synaptic cleft?

Synaptic knobs

Which cells are responsible for removing debris through phagocytosis in the CNS?

Microglia

What is the function of the reticular formation in the Central Nervous System?

Regulates vital reflexes like cardiovascular and respiratory function

Which lobe of the Forebrain is responsible for the reception and interpretation of speech?

Temporal lobe

What is a characteristic feature of the cerebellum's function?

Conscious and unconscious muscle synergy

Which structure in the Brain Stem controls important activities like heart rate, respiration, swallowing, and vomiting?

Medulla Oblongata

Which area in the cerebral cortex is primarily responsible for goal-oriented behavior and short-term memory?

Prefrontal cortex

What is the main cause of Glaucoma?

Increased pressure that compresses and damages the optic nerve

Which type of hearing loss is age-related and usually affects high frequencies?

Sensorineural hearing loss

What does vertigo refer to?

Sensation of spinning due to inflammation of the ear's semicircular canals

What do cognitive functions related to awareness embody?

Awareness of self, environment, and affective states

Which condition is characterized by a lack of verbal response to external stimuli?

Coma

What causes functional hearing loss?

Emotional or psychologic factors

What is the main cause of tinnitus?

Ringing of the ears due to emotional factors

What is the primary function of the reticular-activating system?

Mediating wakefulness and consciousness

What differentiates conductive hearing loss from sensorineural hearing loss?

Impaired sound conduction characterizes conductive, Organ of corti impairment characterizes sensorineural.

How does mixed hearing loss differ from functional hearing loss?

Mixed hearing loss involves both conductive and sensorineural losses, Functional hearing loss is related to emotional or psychologic factors.

What is the distinguishing feature between aseptic meningitis and fungal meningitis?

Type of inflammatory reaction

Which characteristic is common among the most common forms of encephalitis?

Caused by arthropod-prone viruses

What is the primary cause of demyelination in Multiple Sclerosis?

Viral infection

What is a characteristic symptom of Cerebellar type multiple sclerosis?

Motor ataxia

Which type of motor neurons are diffusely affected by Amyotrophic Lateral Sclerosis (ALS)?

Lower and upper motor neurons

What is the primary cause of muscle weakness in Myasthenia Gravis?

Defect in nerve impulse transmission at NMJ

What is the distinguishing feature of encephalitis from meningitis?

Involvement of the optic nerve

Which condition results in scarring or plaque formation in the CNS?

Multiple Sclerosis

What distinguishes Amyotrophic Lateral Sclerosis (ALS) from Myasthenia Gravis?

Disease progression leading to respiratory failure

Which neurological condition primarily involves upper motor neurons?

Amyotrophic Lateral Sclerosis (ALS)

What autoimmune disease results from a defect in nerve impulse transmission at the neuromuscular junction?

Myasthenia Gravis

Which clinical manifestation is common between Myasthenia Crisis and Cholinergic Crisis?

Respiratory insufficiency

What distinguishes myasthenic crisis from cholinergic crisis?

Onset time from taking anticholinesterase medication

What is the primary cause of muscular fatigue in Myasthenia Gravis?

Defect in nerve impulse transmission at the NMJ

What causes progressive weakness leading to respiratory failure in Amyotrophic Lateral Sclerosis?

Degeneration of lower and upper motor neurons

Which autoimmune disease results from degeneration of non-motor neurons in the cortices and spinal cord?

Amyotrophic Lateral Sclerosis (ALS)

What is the characteristic sign that differentiates encephalitis from meningitis?

Specific cranial nerve dysfunction

Which virus is NOT commonly associated with causing encephalitis?

Influenza virus

Which autoimmune disease is characterized by scarring or formation of plaque in the central nervous system?

Multiple Sclerosis (MS)

In which type of Multiple Sclerosis do patients typically experience weakness, numbness, or both in one or more limbs?

Spinal type

Which feature is NOT characteristic of Amyotrophic Lateral Sclerosis (ALS)?

Progressive weakness leading to bradycardia

What distinguishes Myasthenia Crisis from Cholinergic Crisis?

Onset time after drug intake

Study Notes

Cold Injuries

  • A skin injury from exposure to extreme cold temperatures, affecting fingers, toes, ears, nose, and cheeks
  • Burning reaction caused by alternating cycles of vasoconstriction and vasodilation
  • Inflammation and reperfusion are part of the pathophysiology
  • Clinical manifestations: skin appears white or yellowish, waxy, and firm to the touch

Burns

  • A cutaneous injury resulting from thermal, chemical, or electrical causes
  • Multisystem injuries with interactions with shock, inflammation, and immunocompromised state
  • Burn wound depths:
    • Partial-thickness injury: involves only the epidermis, no injury to underlying dermal and subcutaneous tissue
    • Clinical manifestations: local pain, erythema, and no blisters until 24 hours after injury
    • Superficial partial-thickness injury: thin-walled, fluid-filled blisters develop within minutes after injury
    • Deep partial-thickness injury: involves the entire dermis, sparing skin appendages
    • Clinical manifestations: waxy white skin, surrounding margins of superficial partial-thickness injury
    • Full-thickness injury: entire epidermis, dermis, and subcutaneous tissue destroyed
    • Clinical manifestations: burn color is white, cherry, red, or black; blisters are rare

Burn Shock

  • Consequences of a major burn injury, leading to a life-threatening hypovolemic shock
  • Phenomenon consisting of both hypovolemic and cardiovascular components, and cellular components
  • Capillary seal indicates the end of burn shock

Types of Cells

  • Neuron:
    • Primary information/communication cell of the nervous system
    • Variable size and structure throughout the nervous system
    • Primary fuel is glucose, no insulin required for cellular glucose uptake in CNS
    • Cell body (soma) located mainly in the CNS
    • Dendrites carry nerve impulses toward the cell body
    • Axons carry nerve impulses away from the cell body
    • Myelin: segmented layer of lipid material, insulating substance
    • Functional classification: sensory, associational, and motor neurons

Synapses

  • Region between adjacent neurons
  • Impulses transmitted across the synapse by chemical and electrical conduction
  • Presynaptic neurons: proximal to the synapse, relay impulses toward the synapse
  • Postsynaptic neurons: distal to the synapse, relay impulses away from the synapse
  • Neurotransmitters formed in the neuron, stored in synaptic knobs or boutons

Central Nervous System (CNS)

  • Reticular Formation: network of connected nuclei regulating vital reflexes
  • Forebrain (telencephalon):
    • Cerebrum: largest portion of the brain
    • Cerebral cortex: gray matter, organized into columns perpendicular to the surface
    • White matter: numerous tracts, composed of myelinated nerve fibers
    • Lobes: frontal, parietal, occipital, and temporal
    • Functions: voluntary motor, sensory, and cognitive processes

Brain Stem (Hindbrain)

  • Midbrain: relay center for motor and sensory tracts
  • Cerebellum: maintains balance and posture
  • Pons: important center for control of respiration
  • Medulla oblongata: lowest portion of the brainstem, controls reflex activities

Cranial Nerves (Peripheral Nervous System)

  • CN I: Olfactory (sensory)- smell
  • CN II: Optic (sensory)- vision
  • CN III: Oculomotor (motor)- pupil reaction, extraocular movement
  • CN IV: Trochlear (motor)- extraocular movement, superior oblique muscles
  • CN V: Trigeminal (motor & sensory)- mastication, face sensation
  • CN VI: Abducens (motor)- EOM, lateral rectus
  • CN VII: Facial (motor & sensory)- facial expression, taste on anterior of tongue
  • CN VIII: Vestibulocochlear (sensory)- hearing
  • CN IX: Glossopharyngeal (motor & sensory)- motor fibers serve pharynx and salivary glands
  • CN X: Vagus (motor & sensory)- motor and sensory for pharynx, parasympathetic motor fiber
  • CN XI: Spinal Accessory (motor)- sternocleidomastoid and trapezius muscles
  • CN XII: Hypoglossal (motor)- tongue muscles

Spinal Cord

  • Lies within the vertebral canal, protected by the vertebral column
  • Connects the brain and the body, conducts somatic and autonomic reflexes
  • Modulates sensory and motor function
  • Regions: cervical, thoracic, lumbar, sacral, and coccygeal
  • Conus medullaris: end of the spinal cord
  • Cauda equina: nerve bundle at the end of the spinal cord

Upper and Lower Motor Neurons

  • Upper Motor Neurons:
    • Motor pathways completely contained within the CNS
    • Efferent pathways primarily relaying information from the cerebrum to the brainstem or spinal cord
    • Disruptions result in initial paralysis, followed by partial recovery
  • Lower Motor Neurons:
    • Neurons having direct influence on muscles
    • Cell bodies originate in the gray matter of the spinal cord
    • Destruction leads to permanent paralysis

Meninges

  • Protective membranes surrounding the brain and spinal cord
  • Dura mater, arachnoid, and pia mater
  • Falx cerebri: dips between the two cerebral hemispheres along the longitudinal fissure
  • Form potential and real spaces important in understanding functional and pathologic mechanisms

Blood Supply to the Brain

  • Blood supplied by two pairs of large blood vessels: carotid arteries and vertebral arteries
  • Circle of Willis: anterior, middle, and posterior cerebral arteries
  • ACA: supplies blood to the frontal lobe
  • MCA: supplies blood to the middle part of the brain
  • PCA: supplies blood to the back of the brain

Blood Brain Barrier

  • Cellular structures that selectively inhibit certain substances from entering the brain or CSF
  • Functions: protects the brain, maintains a constant biochemical environment
  • Increases permeability or breakdowns: hypertension, dilutional hyponatremia, high doses of anesthetics, vasodilation, and hypercapnia

Peripheral Nervous System (PNS) and Autonomic Nervous System (ANS)

  • PNS: cranial nerves and spinal nerves, peripheral nerve pathways
  • ANS: motor and sensory pathways regulating the body's internal environment
  • Somatic Nervous System: motor and sensory pathways regulating voluntary motor control of skeletal muscle
  • Autonomic Nervous System: motor and sensory pathways regulating the body's internal environment
  • Sympathetic Nervous System: mobilizes energy stores, increases HR and BP, and diverts blood from gut to skeletal muscle
  • Parasympathetic Nervous System: conserves and restores energy, promotes visceral activity and repose

Neuroanatomy of Pain

  • Nociception: transduction, transmission, perception, and modulation
  • Primary-order neurons: nociceptors, bare nerve endings responding to chemical, mechanical, and thermal stimuli
  • Second-order neurons: interneurons in the dorsal horn of the spinal cord
  • Third-order neurons: afferent neurons in the spinothalamic tract
  • Types of pain: somatic, visceral, referred, and neuropathic pain

Types of Acute Pain

  • Somatic pain: superficial, arises from connective tissue, muscle, bone, and skin
  • Visceral pain: internal, transmitted by sympathetic afferents, poorly localized
  • Referred pain: present in an area distant from its origin, supplied by the same spinal segment

Chronic Pain and Neuropathic Pain

  • Chronic pain: persistent or intermittent, no physiological signs, significant behavior and psychological changes
  • Neuropathic pain: result of trauma or disease of the PNS and CNS, leads to abnormal central pain processing
  • Conditions: myofascial pain syndromes, chronic postoperative pain, low back pain, and chronic pain associated with cancer
  • Peripheral neuropathic pain: injured nerves become hyperexcitable
  • Central neuropathic pain: caused by lesion or dysfunction in brain or spinal cord
  • Clinical manifestations: paroxysmal with hyperesthesia and paresthesia, burning, shooting, or stabbing sensations### Temperature Regulation
  • Achieved through precise balancing of heat production, heat conservation, and heat loss
  • Mediated by the hypothalamus
  • Body temperature is maintained around 37°C (98.6°F)
  • Varies in response to: location, activity, environment, circadian rhythm, and gender
  • Peripheral thermoreceptors in the skin and central thermoreceptors in the hypothalamus, spinal cord, and abdominal organs provide information about skin and core temperatures

Fever

  • Triggered by release of pyrogens from leukocytes and other cells involved in the immune response (endogenous pyrogens) and bacteria (exogenous pyrogens)
  • Both a symptom of a disease and a normal immunologic mechanism
  • Involves resetting of the hypothalamic thermostat to a higher level
  • Benefits of fever:
    • Kills many microorganisms
    • Decreases serum levels of iron, zinc, and copper needed for bacteria replication
    • Promotes lysosomal breakdown and auto-destruction of cells
    • Increases lymphocytic and phagocyte motility
    • Augments antiviral interferon production and phagocytosis

Hyperthermia

  • Marked warming of core temperature
  • Not mediated by pyrogens
  • No resetting of the hypothalamic set point
  • Consequences:
    • 41°C (105.8°F): nerve damage produces convulsions
    • 43°C (109.4°F): death results
  • Forms of accidental hyperthermia:
    • Heat cramps
    • Heat exhaustion
    • Heatstroke (potentially lethal)
    • Malignant hyperthermia (potentially lethal)

Sleep

  • Active, multiphase process
  • Hypothalamus is the major sleep center
  • Suprachiasmatic nucleus (SCN) controls the timing of the sleep-wake cycle
  • Hypocreatins (orexins) promote wakefulness and REM sleep
  • Two phases:
    • Rapid eye movement (REM) sleep (20% to 25% of sleep time)
    • Non-rapid eye movement (NREM) sleep (75% to 80% of sleep time)
  • Stages of NREM sleep:
    • Stage N1: light sleep (3% to 8% of sleep time)
    • Stage N2: longest sleep (45% to 55% of sleep time)
    • Stage N3: slow-wave sleep (15% to 20% of sleep time)

Obstructive Sleep Apnea (OSAS)

  • Disorder of breathing during sleep, related to upper airway obstruction
  • Associated with reduced blood oxygen saturation and hypercapnia
  • Risk factors: obesity, male gender, and age
  • Clinical manifestations:
    • Loud snoring
    • Gasping
    • Intervals of apnea lasting 10-30 seconds
    • Fragmented sleep
    • Chronic daytime sleepiness

Age-Related Macular Degeneration (AMD)

  • Drusen or retinal waste products accumulate in the deep retinal layers
  • An eye disease that can blur central vision
  • Happens when aging causes damage to the macula (the part of the eye that controls sharp, straight-ahead vision)
  • Two types:
    • Dry AMD (atrophic AMD): loss of retinal pigment epithelium photoreceptors with overall atrophy of cells
    • Wet AMD (neovascular AMD): abnormal blood vessels grow in the back of the eye and damage the macula

Glaucoma

  • Intraocular pressures above the normal pressures of 12 to 20 mmHg are maintained by the aqueous fluid
  • Increased pressure that compresses and damages the optic nerve
  • Clinical manifestations:
    • Eye pain
    • Pressures
    • Headaches
    • Rainbow-colored halos around lights
    • Low vision, blurred vision, narrowed vision (tunnel vision), or blind spots
    • Nausea and vomiting

Hearing Loss

  • Types:
    • Conductive hearing loss: impaired sound conduction from the outer to inner ear
    • Sensorineural hearing loss: impairment of the organ of corti or its central connections
    • Mixed hearing loss: combination of conductive and sensorineural losses
    • Functional hearing loss: no organic reason, thought to be caused by emotional or psychologic factors
    • Tinnitus: ringing of the ears

Vertigo

  • Sensation of spinning that occurs with inflammation of the ear's semicircular canals
  • State of being awake
  • Mediated by the reticular-activating system

Awareness

  • Cognitive functions that embody awareness of self, environment, and affective states (moods)
  • Content of thought

Coma

  • No verbal response to the external environment or to any stimuli
  • Noxious stimuli such as deep pain or suctioning yields motor movement
  • Produced by either:
    • Bilateral hemisphere damage or suppression
    • Brainstem lesions or metabolic derangement that damages or suppresses the reticular activating system

Brain Death

  • Brain has no potential for recovery and can no longer maintain the body's internal homeostasis
  • State laws: entire brain, brainstem, and cerebellum stops functioning or has already autolyzed on postmortem examination### Cerebral Edema
  • Increase in fluid (intracellular or extracellular) within the brain
  • Harmful effects cause distortion of blood vessels, displacement of brain tissues, and eventual herniation of brain tissue from one compartment to another
  • Results from infection, hemorrhage, tumor, ischemia, infarct, or hypoxia
  • Types of cerebral edema:
    • Vasogenic: most clinically important, caused by increased permeability of the capillary endothelium of the brain after injury to the vascular structure
    • Cytotoxic: metabolic, toxic factors directly affect cellular elements of the brain parenchyma, causing failure of the active transport system
    • Interstitial: seen most commonly with non-communicating hydrocephalus

Hydrocephalus

  • Excess fluid within the cranial vault, subarachnoid space, or both
  • Caused by interference in CSF flow:
    • Decreased reabsorption: blockage of arachnoid villi (absorption) from SAH or infection
    • Increased fluid production: choroid plexus tumor
    • Obstruction within the ventricular system: tumor or congenital malformation
  • Types of hydrocephalus:
    • Communicating (extraventricular) hydrocephalus: from impaired absorption, CSF can flow through ventricles
    • Non-communicating hydrocephalus: internal or intraventricular, blockage occurs along narrow pathways that connect the ventricular system
    • Normal pressure hydrocephalus: occurs mostly in middle-aged people, long-term presentation: memory decline, gait disturbance, and incontinence

Upper Motor Neuron Syndromes

  • Spastic paresis or paralysis:
    • Hemiparesis or hemiplegia: upper and lower extremities on one side
    • Paraparesis or paraplegia: affects lower extremities
    • Quadriparesis or quadriplegia: all 4 extremities
  • Associated with hyperreflexia, pyramidal motor syndrome
  • Spinal shock: complete cessation of spinal cord functions below the lesion, flaccid paralysis, absence of reflexes, and marked disturbances of bowel and bladder function

Lower Motor Neuron Syndromes

  • Flaccid paresis or paralysis:
    • Caused by dysfunction of lower motor neurons (anterior horn cells and motor nuclei of the brainstem)
    • Impairs voluntary and involuntary movement
    • Degree of paralysis or paresis proportional to the number of lower motor neurons affected
    • Associated with areflexia or hyporeflexia

Huntington Disease

  • Autosomal dominant hereditary degenerative disorder
  • Severe degeneration of the basal ganglia (caudate nucleus) and frontal cerebral atrophy
  • Clinical manifestations:
    • Abnormal movement (chorea)
    • Progressive dysfunction of intellectual processes (dementia)
    • Thought processes mark the onset of the disease
    • Choreiform movements begin in the face and arms and progresses to the rest of the body
    • Symptoms of frontal lobe dysfunction: executive attention deficits, short-term memory loss, reduced capacity to plan, organize, and sequence, bradyphrenia, and apathy
    • Euphoria and depression may be present

Parkinson Disease

  • Degeneration of the dopaminergic pathway to the basal ganglia
  • Results in inhibition of the motor cortex, manifested with bradykinesia and rigidity
  • Hallmark pathologic features of PD: loss of dopaminergic pigmented neurons in the substantia nigra pars compacta with dopaminergic deficiency in the putamen
  • Clinical manifestations:
    • Insidious onset of symptoms
    • Classic motor manifestations: bradykinesia, tremor at rest, muscle rigidity, hypokinesia, and stooped posture
    • Non-motor symptoms: hyposmia, fatigue, pain, autonomic dysfunction, sleep fragmentation, depression, and dementia with or without psychosis

Focal Brain Injuries

  • Contusion: bruising of the brain
  • Laceration: tearing of brain tissue
  • Extradural (epidural) hematoma: accumulation of blood above the dura mater
  • Subdural hematoma: blood between the dura mater and arachnoid membrane
  • Intracerebral hematoma: bleeding in the brain
  • Open head trauma: skull fracture with exposure of the cranial vault to the environment

Diffuse Brain Injuries

  • Result from the effect of head rotation or shaking
  • Brain experiences shearing stresses, resulting in axonal damage
  • Pathophysiology can only be seen with a microscope
  • Oxygen free radicals contribute to secondary injury

Concussions

  • Temporary axonal disturbance causing attention and memory deficits
  • Grade I: confusion, disorientation, and momentary amnesia, no loss of consciousness
  • Grade II: momentary confusion and retrograde amnesia, no loss of consciousness
  • Grade III: confusion with retrograde and anterograde amnesia, loss of consciousness for seconds to minutes
  • Grade IV: disconnection of cerebral systems from the brain stem and reticular activating system, loss of consciousness for more than 24 hours

Spinal Cord Trauma

  • Most commonly occurs due to vertebral injuries
  • Traumatic injury of vertebral and neural tissues, resulting in compression, pulling, exerting tension on tissue, or shearing tissues
  • Often causes spinal shock with cessation of all motor, sensory, reflex, and autonomic functions below the transected area
  • Loss of motor and sensory function depends on the level of injury

Cerebrovascular Accident (Stroke)

  • Thrombotic stroke: arterial occlusions caused by thrombi formed in arteries supplying the brain or in intracranial vessels
  • Embolic stroke: fragments that break from a thrombus formed outside the brain
  • Hemorrhagic stroke: bleeding into the brain, can occur secondary to TBI
  • Lacunar stroke: microinfarct smaller than 1cm in diameter, involves small perforating arteries, predominantly in the basal ganglia, internal capsules, and pons

Learn about the functions and characteristics of osteoblasts and osteocytes in bone formation and maintenance. Understand how osteoblasts produce osteocalcin and form new bone, while osteocytes play a role in maintaining bone health.

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