Patho2Final all ppts combined
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Questions and Answers

Which germ layer contributes to the development of the neural tube?

  • Mesoderm
  • Endoderm
  • Ectoderm (correct)
  • All of the above

    • At what stage of gestation does the formation of the neural tube begin?

  • 3-4 weeks (correct)
  • 1-2 weeks
  • 7-8 weeks
  • 5-6 weeks

    • What is the most common anomaly of the CNS?

  • Holoprosencephaly
  • Anencephaly
  • Microcephaly
  • Neural Tube Defects (correct)

    • What is the significance of maternal folate deficiency in relation to NTD?

    <p>It is associated with a significant risk of NTD</p> Signup and view all the answers

    What is the primary method of diagnosis for NTD?

    <p>Prenatal ultrasound</p> Signup and view all the answers

    What is the time frame for surgical repair of meningocele and myelomeningocele?

    <p>Within the first 72 hours of life</p> Signup and view all the answers

    What is the term for the closure of the neural tube in two directions?

    <p>Zipping</p> Signup and view all the answers

    What is the name of the structure formed by the embryo by day 14 of gestation?

    <p>Prechordal Plate</p> Signup and view all the answers

    What is the characteristic of Spina Bifida Occulta?

    <p>Small opening in the vertebrae, but defect is fully covered by skin</p> Signup and view all the answers

    What is the typical complication of Myelomeningocele?

    <p>Hydrocephalus in 85% of infants</p> Signup and view all the answers

    What is the characteristic of Type II Arnold Chiari Malformation?

    <p>Is associated with hydrocephalus from pressure that blocks the flow of CSF</p> Signup and view all the answers

    What is the purpose of Maternal serum alpha fetoprotein (MSAFP) testing?

    <p>To detect neural tube defects</p> Signup and view all the answers

    What is the detection rate of spina bifida using fetal ultrasound examination in a high-risk population?

    <p>92-95%</p> Signup and view all the answers

    What is the characteristic of Anencephaly?

    <p>Soft, bony component of the skull and part of the brain are missing</p> Signup and view all the answers

    What is the ideal gestation period for Maternal serum alpha fetoprotein (MSAFP) testing?

    <p>16-18 weeks</p> Signup and view all the answers

    What is the percentage of cases of neural tube defects that occur in pregnancies without any risk factors?

    <p>90-95%</p> Signup and view all the answers

    Which of the following types of receptors is responsible for detecting pain stimuli in the viscera?

    <p>Nociceptors</p> Signup and view all the answers

    Which of the following is a characteristic of the sympathetic nervous system?

    <p>Paravertebral ganglia are arranged in two longitudinal chains</p> Signup and view all the answers

    Which of the following is a target tissue of the autonomic nervous system?

    <p>Smooth muscle</p> Signup and view all the answers

    What is the function of the preganglionic neuron in the autonomic nervous system?

    <p>To transmit signals from the preganglionic neuron to the postganglionic neuron</p> Signup and view all the answers

    What is the main difference between the autonomic nervous system and the somatic nervous system?

    <p>The autonomic nervous system has a two-neuron system, while the somatic nervous system has a one-neuron system</p> Signup and view all the answers

    Which of the following is a characteristic of the parasympathetic nervous system?

    <p>It is responsible for promoting digestion and relaxation</p> Signup and view all the answers

    What is the function of the mechanoreceptors in the autonomic nervous system?

    <p>To detect changes in pressure and wall tension</p> Signup and view all the answers

    Which of the following receptors is responsible for bronchodilation?

    <p>β2-adrenergic receptors</p> Signup and view all the answers

    What is the effect of nicotine on nicotinic receptors?

    <p>Acts as an agonist</p> Signup and view all the answers

    What is the primary function of muscarinic receptors in the GI tract?

    <p>Contraction of smooth muscle</p> Signup and view all the answers

    What is the effect of atropine on the cardiac conduction system?

    <p>Blocks PSNS input to the cardiac conduction system</p> Signup and view all the answers

    What is the primary function of β1-adrenergic receptors in the heart?

    <p>Increases heart rate and contractility</p> Signup and view all the answers

    What is the effect of α2-adrenergic receptors on neurotransmitter release?

    <p>Decreases neurotransmitter release</p> Signup and view all the answers

    What is the mechanism of action of Varenicline in smoking cessation?

    <p>Acts as a nicotinic receptor antagonist</p> Signup and view all the answers

    What is the location of the sympathetic trunk in the body?

    <p>Near the spinal cord</p> Signup and view all the answers

    Which neurotransmitter is released directly into the bloodstream by the adrenal medulla?

    <p>Epinephrine</p> Signup and view all the answers

    What is the role of the parasympathetic nervous system?

    <p>To conserve and restore energy</p> Signup and view all the answers

    Which of the following organs is NOT innervated by the parasympathetic nervous system?

    <p>Uterus</p> Signup and view all the answers

    What is the characteristic of the postganglionic fibers of the parasympathetic nervous system?

    <p>Short and minimally branched</p> Signup and view all the answers

    What is the receptor type for the neurotransmitter acetylcholine in the autonomic nervous system?

    <p>Cholinergic</p> Signup and view all the answers

    What is the effect of α1-adrenergic receptors on the body?

    <p>Excitation and stimulation</p> Signup and view all the answers

    What is the primary neurotransmitter released by the sympathetic nervous system?

    <p>Norepinephrine</p> Signup and view all the answers

    What is the anatomical difference between the sympathetic and parasympathetic nervous systems?

    <p>All of the above</p> Signup and view all the answers

    What is the effect of the parasympathetic nervous system on cardiac conduction?

    <p>Decreases heart rate</p> Signup and view all the answers

    Where does the spinal cord originate from?

    <p>Medulla oblongata</p> Signup and view all the answers

    What is the function of the ventral horn in the spinal cord?

    <p>Transmit motor signals from the brain to the body</p> Signup and view all the answers

    What is the term for the nerve fibers projecting from the end of the spinal cord beyond L1?

    <p>Cauda equina</p> Signup and view all the answers

    What is the neurotransmitter used by upper motor neurons?

    <p>Glutamate</p> Signup and view all the answers

    What is the characteristic of spinal reflexes?

    <p>Involuntary, near-instant response to a stimulus that does not involve input from the brain</p> Signup and view all the answers

    What is the location of the cell bodies of lower motor neurons?

    <p>Ventral horn of the spinal cord</p> Signup and view all the answers

    Which type of reflex arc is responsible for maintaining posture?

    <p>Stretch reflex</p> Signup and view all the answers

    What type of muscle recruitment occurs in the stretch reflex arc?

    <p>Synergistic muscle recruitment</p> Signup and view all the answers

    What is the purpose of the Golgi Tendon Reflex?

    <p>To sense if there is too much muscle tension</p> Signup and view all the answers

    What type of fibers decussate immediately at their level of entry into the spinal cord?

    <p>Spinothalamic fibers</p> Signup and view all the answers

    What is the significance of dermatomes and myotomes in spinal cord organization?

    <p>They determine the sensation and motor function of a particular region</p> Signup and view all the answers

    What is the primary function of ascending tracts?

    <p>To transmit sensory information from the spinal cord to the brain</p> Signup and view all the answers

    What is the clinical significance of the stretch reflex arc?

    <p>It operates as a protective mechanism to prevent strain or tear of muscles and tendons</p> Signup and view all the answers

    What is the purpose of reciprocal innervation in the stretch reflex arc?

    <p>To relax the opposing muscle group</p> Signup and view all the answers

    In the corticospinal tract, which neurons are medial and which are lateral?

    <p>Cervical neurons are medial and sacral neurons are lateral</p> Signup and view all the answers

    What is the main difference between a complete and incomplete spinal cord injury?

    <p>Complete injuries result in total loss of motor and sensory function, while incomplete injuries result in partial loss</p> Signup and view all the answers

    What is the primary mechanism of injury in a cord concussion?

    <p>Rapid changes in velocity</p> Signup and view all the answers

    What is the characteristic clinical presentation of central cord syndrome?

    <p>Motor impairment greater in the arms than the legs</p> Signup and view all the answers

    What is the primary cause of cord compression?

    <p>All of the above</p> Signup and view all the answers

    What is the effect of excitotoxicity on neurons?

    <p>Influx of calcium and sodium ions, leading to cell death</p> Signup and view all the answers

    What is the primary location of hemorrhage in spinal cord injuries?

    <p>Central gray matter</p> Signup and view all the answers

    What is the primary difference between primary and secondary spinal cord injury?

    <p>Primary injury is due to the initial trauma, while secondary injury is due to subsequent events</p> Signup and view all the answers

    What is the effect of infarction on the spinal cord?

    <p>Decreased oxygen delivery, leading to tissue death</p> Signup and view all the answers

    Why do arms tend to be more affected than legs in central cord syndrome?

    <p>The corticospinal tract is more lateral in the cervical region</p> Signup and view all the answers

    What is the most common cause of Anterior Cord Syndrome?

    <p>Hyperflexion</p> Signup and view all the answers

    In Brown-Sequard Syndrome, which type of sensations would be preserved below the level of injury?

    <p>Bilateral</p> Signup and view all the answers

    What is the underlying cause of Subacute Combined Degeneration?

    <p>Vitamin B12 deficiency</p> Signup and view all the answers

    What is the primary method of treatment for Autonomic Dysreflexia?

    <p>Remove the stimulus</p> Signup and view all the answers

    Which type of spinal cord injury is characterized by motor impairment greater in the arms and sacral sparing?

    <p>Central Cord Syndrome</p> Signup and view all the answers

    What is the primary function of Vitamin B12 in the spinal cord?

    <p>Synthesis of DNA and myelin</p> Signup and view all the answers

    Which of the following is NOT a clinical manifestation of Autonomic Dysreflexia?

    <p>Paralysis below the level of injury</p> Signup and view all the answers

    In Brown-Sequard Syndrome, which tracts are damaged on the opposite side of the injury?

    <p>Spinothalamic tracts</p> Signup and view all the answers

    What is the level of spinal cord injury above which Autonomic Dysreflexia is more likely to occur?

    <p>T6</p> Signup and view all the answers

    What is the primary method of distinguishing between incomplete and complete Spinal Cord Injury (SCI)?

    <p>Rectal exam</p> Signup and view all the answers

    What is the primary mechanism by which autoimmune diseases originate?

    <p>An initiating event in a genetically predisposed individual</p> Signup and view all the answers

    What is the primary mechanism by which immune complexes cause injury in SLE?

    <p>Deposition in renal tubular basement membranes, leading to inflammatory lesions</p> Signup and view all the answers

    What is the primary reason why SLE is difficult to diagnose?

    <p>Intermittent and variable symptoms affecting multiple body systems</p> Signup and view all the answers

    Which of the following organs is least likely to be affected by SLE?

    <p>Skeletal muscles</p> Signup and view all the answers

    What is the characteristic of the primary pathogenesis in osteoarthritis?

    <p>Degeneration, loss, and disordered repair of articular cartilage</p> Signup and view all the answers

    What is the most common joint disease?

    <p>Osteoarthritis</p> Signup and view all the answers

    What is the leading cause of disability in middle-aged and older populations in the US?

    <p>Osteoarthritis</p> Signup and view all the answers

    What is the characteristic of proteoglycans in articular cartilage?

    <p>They regulate the movement of water and synovial fluid into and out of the cartilage</p> Signup and view all the answers

    What is the effect of the loss of proteoglycans from articular cartilage?

    <p>The cartilage becomes less able to withstand the stresses of weightbearing</p> Signup and view all the answers

    What is the characteristic of the relationship between age and osteoarthritis?

    <p>Osteoarthritis is more common in older populations</p> Signup and view all the answers

    What is the effect of obesity on the risk of osteoarthritis?

    <p>Obesity increases the risk of osteoarthritis</p> Signup and view all the answers

    What is the characteristic of Ankylosing Spondylitis?

    <p>It is an autoimmune disorder</p> Signup and view all the answers

    What is the characteristic of Rheumatoid Arthritis?

    <p>It is an autoimmune disorder</p> Signup and view all the answers

    What is the characteristic of Gout?

    <p>It is an inflammatory arthropathy caused by crystals</p> Signup and view all the answers

    What percentage of the body's phosphate is found in the bones?

    <p>85%</p> Signup and view all the answers

    Which type of bone is characterized by being longer than they are wide?

    <p>Long bones</p> Signup and view all the answers

    What is the primary function of osteoblasts?

    <p>To synthesize and secrete collagen and other organic components of bone matrix</p> Signup and view all the answers

    Which of the following bones protects the spinal cord?

    <p>Vertebrae</p> Signup and view all the answers

    What is the function of the skeletal system in movement?

    <p>To provide a framework for skeletal muscles to move the body</p> Signup and view all the answers

    What percentage of bone cells are osteocytes?

    <p>90-95%</p> Signup and view all the answers

    Which type of tissue is found in bones, supporting the bone cells?

    <p>Connective tissue</p> Signup and view all the answers

    Which of the following bones is an example of a flat bone?

    <p>Scapula</p> Signup and view all the answers

    What is the primary function of canaliculi in spongy bone?

    <p>To allow exchange of nutrients, wastes, and chemical signals between osteocytes</p> Signup and view all the answers

    What is the process by which the bony skeleton is formed in embryos?

    <p>Intramembranous ossification</p> Signup and view all the answers

    What is the function of osteoblasts in intramembranous ossification?

    <p>To secrete organic components of bone matrix and differentiate into osteocytes</p> Signup and view all the answers

    What is the characteristic of trabeculae in spongy bone?

    <p>They are only a few cell layers thick and align along positions of stress</p> Signup and view all the answers

    What is the purpose of step 3 in intramembranous ossification?

    <p>Vascularization of the developing bone</p> Signup and view all the answers

    What is the primary function of osteoclasts in bone growth, development, maintenance, and repair?

    <p>To secrete digestive enzymes to digest bone matrix</p> Signup and view all the answers

    What is the characteristic of endochondral ossification?

    <p>It involves the replacement of hyaline cartilage with bone</p> Signup and view all the answers

    What is the function of the periosteum in intramembranous ossification?

    <p>To provide a layer of connective tissue around the bone</p> Signup and view all the answers

    What type of bone marrow is responsible for producing blood cells?

    <p>Red bone marrow</p> Signup and view all the answers

    What is the term for the delicate mesh of reticular tissue saturated with immature red blood cells and scattered adipocytes?

    <p>Red bone marrow</p> Signup and view all the answers

    What is the characteristic of compact bone formed through intramembranous ossification?

    <p>It is formed around trapped blood vessels</p> Signup and view all the answers

    What is the purpose of the periosteum?

    <p>To cover the external surface of the bone</p> Signup and view all the answers

    What is the name of the structural units in compact bone?

    <p>Osteons</p> Signup and view all the answers

    What is the function of Volkman's canals?

    <p>To bring in blood and nerve supply from the periosteum</p> Signup and view all the answers

    What is the term for the incomplete lamellae that fill the gaps between osteons or are remnants of bone remodeling?

    <p>Interstitial lamellae</p> Signup and view all the answers

    What is the primary component of the inorganic part of bone matrix?

    <p>Calcium phosphate and calcium hydroxide</p> Signup and view all the answers

    What is the delicate connective tissue membrane that covers internal bone surfaces?

    <p>Endosteum</p> Signup and view all the answers

    What occurs when large chondrocytes grow in endochondral ossification?

    <p>Big spaces are created in the middle of the bone.</p> Signup and view all the answers

    What happens to the cartilage near the epiphysis in endochondral ossification?

    <p>It is replaced by compact bone.</p> Signup and view all the answers

    What is the function of the epiphyseal plate?

    <p>To increase the length of the bone shaft.</p> Signup and view all the answers

    What is the process by which diaphyseal cartilage is transformed into bone?

    <p>Endochondral ossification.</p> Signup and view all the answers

    What is the purpose of the secondary ossification center in endochondral ossification?

    <p>To create a cartilaginous area in the epiphysis.</p> Signup and view all the answers

    What is the result of the division of epiphyseal cartilage in endochondral ossification?

    <p>The increase in length of the bone shaft.</p> Signup and view all the answers

    What is the primary function of osteoblasts beneath the periosteum?

    <p>To secrete bone matrix on the external surface of the bone</p> Signup and view all the answers

    What is the result of the combined activities of growth hormone, thyroid hormone, and the sex hormones during puberty?

    <p>An increase in bone length and width</p> Signup and view all the answers

    What is the purpose of Wolff's law in bone remodeling?

    <p>To respond to mechanical loading and repair microdamage</p> Signup and view all the answers

    Which of the following nutrients is necessary for bone growth and maintenance?

    <p>Vitamin D</p> Signup and view all the answers

    What is the function of osteoclastic cells in bone remodeling?

    <p>To mediate the first phase of remodeling and scoop out bone</p> Signup and view all the answers

    What is the percentage of calcium found in bone and teeth?

    <p>99%</p> Signup and view all the answers

    What is the purpose of calcitriol in the intestine?

    <p>To facilitate the absorption of calcium and phosphate salts</p> Signup and view all the answers

    What is the sequence of bone remodeling?

    <p>Activation, resorption, formation</p> Signup and view all the answers

    What type of fracture is common in the elderly due to brittle bones?

    <p>Comminuted</p> Signup and view all the answers

    What is the term for the new connective tissue and microscopic blood vessels that form on the surfaces of a wound during the healing process?

    <p>Granulation tissue</p> Signup and view all the answers

    What is the result of avascular necrosis in the proximal scaphoid bone?

    <p>Death of the proximal scaphoid but survival of the distal scaphoid</p> Signup and view all the answers

    What is the typical timeframe for the conversion of the fibrocartilaginous callus into a bony callus of spongy bone?

    <p>6-8 weeks</p> Signup and view all the answers

    What type of fracture occurs when the bone breaks incompletely, with one side bent and the other side broken?

    <p>Greenstick</p> Signup and view all the answers

    What is the significance of the periosteum/endosteum in fracture repair?

    <p>It supplies the blood vessels necessary for bone healing</p> Signup and view all the answers

    What is the result of vascular interruption in fracture repair?

    <p>Bone cells die due to lack of nutrients</p> Signup and view all the answers

    What percentage of calcium in the blood is ionized and metabolically active?

    <p>50%</p> Signup and view all the answers

    What is the primary function of parathyroid hormone?

    <p>To maintain ionized calcium levels adequate for metabolic needs</p> Signup and view all the answers

    What is the characteristic of osteomalacia?

    <p>Inadequate mineralization of osteoid</p> Signup and view all the answers

    What is the effect of glucocorticoids on bone?

    <p>Stimulation of osteoclast activity</p> Signup and view all the answers

    What is the primary cause of osteoporosis in postmenopausal women?

    <p>Decreased levels of estrogen</p> Signup and view all the answers

    What is the effect of calcitonin on bone?

    <p>Inhibition of osteoclast activity</p> Signup and view all the answers

    What is the primary function of insulin in bone?

    <p>Stimulation of bone formation</p> Signup and view all the answers

    What is the characteristic of rickets?

    <p>Inadequate mineralization of osteoid</p> Signup and view all the answers

    What is the effect of growth hormone on bone?

    <p>Stimulation of bone growth</p> Signup and view all the answers

    What is the primary function of thyroid hormone in bone?

    <p>Stimulation of osteoblast activity</p> Signup and view all the answers

    Study Notes

    Nervous System Development

    • Formation of the neural tube occurs between 3-4 weeks of gestation
    • Development of the forebrain from the neural tube occurs between 2-3 months of gestation
    • Neuronal proliferation and migration occur between 3-5 months of gestation
    • Formation of network connections and synapses occurs from 5 months gestation to many years postnatal
    • Myelination occurs from birth to many years postnatal

    Embryonic Development

    • By day 14 of gestation, the embryo develops into a disc-shaped structure called the Prechordal Plate
    • The Prechordal Plate consists of three main layers: Ectoderm, Mesoderm, and Endoderm
    • The neural tube develops from the Ectoderm
    • The Mesoderm contributes to the cardiovascular tube
    • The Endoderm contributes to the gut tube

    Neural Tube Defects (NTD)

    • NTDs are the most common anomaly of the CNS
    • They originate during the first month of embryonic development when the neural tube fails to close completely
    • Maternal folate deficiency is associated with a significant risk of NTD
    • Other risk factors include maternal diabetes and maternal use of some seizure medications like valproic acid

    Types of NTD

    • Spina Bifida: the most common NTD, characterized by a small opening in the vertebrae
    • Spina Bifida Occulta: a small opening in the vertebrae, but the defect is fully covered by skin and there is no visible exposure of meninges or neural tissues
    • Meningocele: a saclike cyst of meninges filled with spinal fluid that protrudes through a defect in the posterior arch of the vertebra
    • Myelomeningocele: a herniation of a saclike cyst containing meninges, spinal fluid, and a portion of the spinal cord with its nerves through a defect in the posterior arch of a vertebra

    Complications of Myelomeningocele

    • Hydrocephalus occurs in 85% of infants with myelomeningocele
    • Almost always associated with Type II Arnold Chiari malformation
    • Spinal cord and nerve roots may be malformed distal to the lesion, resulting in loss of motor, sensory, reflex, and autonomic function

    Arnold Chiari Malformation

    • A complex malformation of the brainstem and cerebellum
    • Type I: does not involve the brainstem and may be asymptomatic
    • Type II: associated with hydrocephalus from pressure that blocks the flow of CSF
    • Type III: the brainstem or cerebellum extends into a high cervical myelomeningocele
    • Type IV: the cerebellum does not develop

    Anencephaly

    • A condition where the soft, bony component of the skull and part of the brain are missing
    • Infants are stillborn or die within the first few days of life
    • Diagnosis is usually made during prenatal ultrasound or with screening maternal serum alpha fetoprotein levels

    Prenatal Screening for NTD

    • All pregnant people are offered screening for NTDs
    • 90-95% of cases occur in pregnancies without any risk factors
    • Screening tests include:
      • Maternal serum alpha fetoprotein (MSAFP): a fetal-specific globulin that is synthesized by the yolk sac, GI tract, and liver; elevated MSAFP levels are associated with NTDs
      • Fetal ultrasound: detection of NTDs on ultrasound examination depends on the size and location of the defect, the position of the fetus, the volume of amniotic fluid, maternal body habitus, and the skill and equipment of the sonographer/sonologist

    Autonomic Nervous System (ANS)

    • Function: Maintains steady state among organs; regulates cardiac muscle, smooth muscle, and glands
    • Targets: smooth muscles, glands, cardiac muscle, and cardiac electrical conduction system

    Target Tissues

    • Smooth muscles: blood vessel walls, alimentary canal, and urinary bladder
    • Glands: sweat glands, respiratory and GI tract glands
    • Cardiac muscle and cardiac electrical conduction system

    Peripheral Nerves

    • Special sensory receptors: gather and communicate information from target tissues, including skin, internal organs, and associated blood vessels
    • Receptors: chemoreceptors, mechanoreceptors, and nociceptors

    Sensory Component (Afferent)

    • Long processes: from specialized receptors in peripheral tissues to cell bodies in the dorsal root ganglia of the spinal cord

    Motor Component (Efferent)

    • Two-neuron system: preganglionic (myelinated) and postganglionic (unmyelinated)
    • Most prominent: Vagus nerve

    Autonomic Nervous System Divisions

    • Sympathetic: "Fight or Flight" response
    • Parasympathetic: conserves/restores energy

    Sympathetic Nervous System

    • Organization: paravertebral ganglia (two longitudinal chains) and prevertebral ganglia (nerve tissue nodes anterior to the spinal column)
    • Primary neurotransmitters: epinephrine and norepinephrine
    • Preganglionic neurons: travel in the sympathetic trunk and synapse with postganglionic neurons at various levels

    Parasympathetic Nervous System

    • Organization: neuroanatomically distinct from the sympathetic nervous system, with ganglia located near or embedded in target organs
    • Primary neurotransmitters: acetylcholine
    • Affects cardiac conduction
    • Does not innervate uterus, sweat glands, skeletal muscles, or adrenal gland

    Anatomical Differences between Sympathetic and Parasympathetic Divisions

    • Origin: sympathetic (thoracolumbar region) vs. parasympathetic (craniosacral region)
    • Location of ganglia: sympathetic (close to spinal cord) vs. parasympathetic (close to target organs)
    • Length of postganglionic fibers: sympathetic (long) vs. parasympathetic (short)
    • Postganglionic branching: sympathetic (lots) vs. parasympathetic (little)

    Adrenal Medulla

    • Endocrine gland that behaves like a sympathetic ganglion
    • Sympathetic nerve fibers from sympathetic trunk → Adrenal Medulla → Epi/Norepi released directly into bloodstream

    Autonomic Nervous System - Neurotransmitters

    • Sympathetic preganglionic fibers: acetylcholine (cholinergic receptor)
    • Sympathetic postganglionic fibers: norepinephrine (adrenergic receptor)
    • Parasympathetic preganglionic and postganglionic fibers: acetylcholine (cholinergic receptor)

    Adrenergic Receptors

    • Class of G-protein coupled receptors that are the target for catecholamines (epinephrine, norepinephrine)
    • α-adrenergic receptors: α1 (excitation/stimulation), α2 (relaxation/inhibition)
    • β-adrenergic receptors: β1 (increases heart rate and contractility), β2 (relaxes muscles in bronchi, bladder, and facilitates other β receptors)

    Clinical Correlations

    • Vasopressors/Inotropes: give patients with shock "exogenous sympathetic nervous system support" with Norepinephrine, Epinephrine, Dopamine, and inotropic drugs like Dobutamine, Milrinone
    • Smoking: nicotine acts as a nicotinic receptor agonist, involved in reward pathways with dopamine
    • Quitting smoking: use a nicotinic receptor antagonist, such as Varenicline (Chantix)
    • Atropine: muscarinic receptor antagonist, used to treat bradycardia, dilate pupils, and as an antidote for organophosphate poisoning

    The Spinal Cord

    • Lies within the vertebral column and is covered by the meninges
    • Originates in the medulla oblongata and carries two types of information:
      • Efferent motor neuron outputs from the brain
      • Afferent sensory neural inputs to the brain from the body
    • In the adult, the spinal cord extends to the lower border of L1, with the conus medullaris at L1/L2 and the cauda equina at S5

    Spinal Cord: Gray Matter Horns

    • Dorsal Horn:
      • Axons/interneurons of sensory (afferent) neurons
      • Sensory fibers travel through the dorsal roots to the posterior horn of the gray matter
    • Ventral Horn:
      • Cell bodies for motor (efferent) pathways leaving the spinal cord
      • Motor fibers travel out through the ventral roots from the anterior horn of the gray matter

    Upper and Lower Motor Neurons

    • Upper Motor Neurons:
      • Cell bodies live in the motor cortex of the brain with axons reaching down to a certain vertebral level in the corticospinal tract
      • Crosses from one side of the body to the other at the level of the brain stem
      • Use glutamate as their neurotransmitter
    • Lower Motor Neurons:
      • Cell bodies live in the ventral horn of the spinal cord with axons reaching out into the peripheral nervous system (PNS)
      • Use acetylcholine as their neurotransmitter at the neuromuscular junction

    Spinal Reflexes

    • Definition: Involuntary, near-instant response to a stimulus that does not involve input from the brain
    • Types of reflex arcs:
      • Autonomic (visceral organs)
      • Somatic (muscles)
      • Stretch reflexes (maintaining posture, deep tendon reflex, Golgi tendon reflex)
      • Crossed extensor reflexes (compensating for a stimulus on one side of the body)
      • Flexor/withdrawal reflexes (response to noxious stimulus)

    Stretch Reflex Arc

    • Four processes:
      • Monosynaptic response (information only goes through one synapse)
      • Reciprocal innervation (opposing muscle group receives efferent message)
      • Synergistic muscle recruitment (accessory muscle group receives efferent message)
      • Ascending information (afferent fibers travel to the brain)

    Clinical Correlation – Stretch Reflex

    • Operates as a protective mechanism to prevent strain/tear of muscles and tendons
    • When the muscle is stretched/engaged, an automatic impulse to contract helps to protect it from being pulled forcefully or stretched beyond normal ROM
    • Clinically, we can get information about the spinal cord, peripheral nerves, and muscle tone/strength by checking reflexes

    Spinal Cord Organization

    • Dermatomes and myotomes:
      • Sensory (dermatomes)
      • Motor (myotomes)
    • Ascending and descending tracts:
      • Ascending tracts (afferent/sensory): spinothalamic, dorsal column
      • Descending tracts (efferent/motor): corticospinal
    • Afferent pathways (ascending):
      • Spinothalamic (vague touch, pain, temperature)
      • Dorsal columns (basic perception of touch, proprioception, vibration)
    • Efferent pathways (descending):
      • Corticospinal tracts (efferent/motor control below the head, contain upper motor neurons)

    Spinal Cord Injuries

    • Complete vs incomplete spinal cord injury:
      • Complete spinal cord transection: interrupts all three tracts with complete loss of motor/sensory function below the level of injury
      • Incomplete spinal cord injury: variable degree of dysfunction due to only part of the spinal cord being affected
    • Types of spinal cord injuries:
      • Cord concussion (transient dysfunction with or without vertebral damage)
      • Cord contusion (bruising of the spinal cord leading to bleeding, edema, and tissue death)
      • Cord compression (pressure on the spinal cord from an external source)
      • Cord transection (tear within the spinal cord itself, compromising blood supply and CSF)
    • Hemorrhage and infarct:
      • Hemorrhage: typically due to trauma or vascular malformation, leading to edema and tissue destruction
      • Infarct: blockage of vertebral arteries due to atherosclerosis, inflammation, or blood clots, leading to tissue death

    Evolution of Spinal Cord Injury

    • Primary cord injury: the actual trauma/compression/transaction
    • Secondary cord injury: cascade of events leading to swelling and tissue destruction, starting within minutes and lasting for weeks

    Incomplete Spinal Cord Injuries (SCI)

    • Central cord syndrome:
      • Most common incomplete spinal cord injury
      • Most common cause: hyperextension injury
      • Clinical presentation: motor impairment greater in the arms than the legs, variable sensory loss below the level of injury, sacral sparing
    • Anterior cord syndrome:
      • Most common cause: hyperflexion
      • Clinical presentation: variable loss of motor/sensory function below the injury, but posterior/dorsal column is intact
    • Brown-Sequard syndrome:
      • Injury damaging one side of the cord
      • Clinical presentation: motor/dorsal column sensory loss on the same side of injury, and spinothalamic sensory loss on the opposite side

    Other Spinal Cord Diseases

    • Subacute combined degeneration:
      • Cause: B12 deficiency
      • Seen more often in elderly, malnourished patients
      • Demyelination of dorsal/posterior columns and lateral corticospinal tracts
      • Clinical presentation: sensory deficits, weakness, ataxia, and gait disturbances
    • Autonomic dysreflexia (hyperreflexia):
      • Massive, sudden sympathetic discharge that can be life-threatening
      • Seen in spinal cord lesions above T6, with a higher risk at higher levels of injury
      • Clinical manifestations: severe hypertension, bradycardia, headache, blurred vision, flushed skin, and sweating

    Autoimmune Reaction and Autoimmune Diseases

    • Autoimmune reaction causes inflammation in areas of the body where it is not needed, leading to pain, swelling, and organ damage.
    • Autoimmune diseases originate from an initiating event in a genetically predisposed individual, leading to an autoimmune mechanism that affects specific target tissues or cells.

    Systemic Lupus Erythematosus (SLE)

    • More common in women (10:1) and in the 20-40 years old age group.
    • A chronic, multisystem, inflammatory disease with frequent remissions and exacerbations.
    • Pathophysiology involves production of a large variety of autoantibodies, including ANA, anti-DS DNA, anti-Smith, and APLA.
    • Autoantibodies are typically against nucleic acids, histones, ribonucleoproteins, and other nuclear materials.
    • Immune complexes (DNA + antibody) cause inflammatory lesions in various organs, including the kidneys, brain, heart, spleen, lung, gastrointestinal tract, skin, and peritoneum.
    • Most common clinical manifestations include:
      • Arthralgias or arthritis (90%)
      • Vasculitis and rash (malar and discoid)
      • Renal disease (40% to 50%)
      • Hematologic abnormalities (50% with anemia being the most common complication)
      • Cardiovascular diseases (30% to 50%)
    • Diagnosing SLE is challenging due to the intermittent nature of symptoms affecting almost every body system.

    Arthropathies

    • Joint diseases can be classified into:
      • Non-inflammatory arthropathy (Osteoarthritis)
      • Inflammatory Arthropathies (Rheumatoid Arthritis, Gout, Ankylosing Spondylitis)

    Osteoarthritis

    • Most common joint disease and leading cause of disability in middle-aged and older populations in the US.
    • Most often affects the knees, hip, neck, hands, and lower back.
    • Characterized by:
      • Local areas of loss and damage of articular cartilage
      • Bone spurs (osteophytes)
      • Subchondral bone changes
      • Variable degrees of mild synovitis
      • Thickening of the joint capsule
    • Susceptibility to osteoarthritis is influenced by:
      • Joint vulnerability (systemic factors: age, female, genetics, nutritional factors)
      • Intrinsic factors (previous damage, muscle weakness, malalignment, proprioception deficiency)
      • Joint load factors (obesity, physical activities prone to injury)
    • Pathogenesis involves degeneration, loss, and disordered repair of articular cartilage, leading to:
      • Increased remodeling of articular cartilage
      • Loss of the smooth, frictionless joint
      • Cartilage becomes thin and may be absent over some areas
      • Loss of proteoglycans from articular cartilage
    • Clinical manifestations include:
      • Joint pain and stiffness
      • Stiffness in the morning and usually brief

    Gout

    • Clinical manifestations:
      • Increase in serum urate concentration
      • Recurrent attacks of monoarticular arthritis
      • Severe pain, swelling, tenderness, erythema
      • 50% of initial attacks are in the great toe metatarsophalangeal joint
      • Tophi: Deposits of monosodium urate in and around the joints
      • Renal disease involving glomerular, tubular, and interstitial tissues and blood vessels
      • Formation of renal stones
    • Three clinical stages:
      • Asymptomatic Hyperuricemia
      • Acute Gouty Arthritis
      • Tophaceous Gout

    The Human Skeletal System

    • Composed of the body's bones and associated ligaments, tendons, and cartilages
    • Functions: support, protection, movement, reservoir for minerals/adipose tissue, and hematopoiesis

    Bone Classification

    • 4 types of bones: long, short, flat, and irregular
    • Long bones: longer than they are wide, found in limbs except patella and wrist/ankle bones, consists of shaft and 2 expanded ends
    • Short bones: roughly cube-shaped, found in wrist and ankle bones
    • Flat bones: thin, flattened, and curved, found in scapulae, sternum, ribs, and most skull bones
    • Irregular bones: have weird shapes, fit none of the previous classes, found in vertebrae, hip bones, sphenoid, and ethmoid bones

    Bone Components

    • Bones are organs composed of multiple tissue types
    • Components: osseous tissue, fibrous connective tissue, cartilage, vascular tissue, lymphatic tissue, adipose tissue, and nervous tissue

    Bone Functional Cells

    • Osteoblasts: bone-building cells, found in periosteum and endosteum, synthesize and secrete collagen and bone matrix, initiate calcification process
    • Osteocytes (90-95% of bone cells): mature bone cells, former osteoblasts trapped in matrix, maintain bone tissue, signal osteoblasts and osteoclasts
    • Osteoclasts: huge cells created by monocyte fusion, digest bone matrix, part of bone growth and development, concentrated in endosteum

    Bone Structure

    • Bone matrix: consists of 1/3 organic and 2/3 inorganic components
    • Organic component: proteins secreted by osteoblasts, mainly collagen, provides bone resilience and resistance to stretching
    • Inorganic component: mainly calcium phosphate and hydroxide, interacts to form hydroxyapatite, contains magnesium, fluoride, and sodium

    Bone Marrow

    • Bone marrow: soft tissue occupying medullary cavity, spaces among trabeculae, and haversian canals
    • 2 main types: red and yellow
    • Red bone marrow: hematopoietic tissue, produces blood cells, found in axial skeleton, pectoral girdle, pelvic girdle, and proximal heads of humerus and femur
    • Yellow bone marrow: inactive, no longer produces blood, but can transform back to red marrow in severe anemia

    Layers of Bone

    • Endosteum: delicate connective tissue membrane, covers internal bone surfaces, lines canals and trabeculae, contains osteoblasts and osteoclasts
    • Periosteum: double-layered membrane, covers external bone surface except joint surfaces, contains osteoprogenitor cells, blood vessels, nerves, and lymphatics

    Compact Bone

    • Consists of multiple cylindrical structural units (osteons or haversian systems)
    • Components: haversian canal, concentric lamellae, lacunae, osteocytes, canaliculi, veins, arteries, nerves, and lymphatics
    • Function: weight-bearing pillars, arranged parallel to long axis of long bone, withstand twisting forces

    Spongy Bone

    • Less organized than compact bone, no Haversian systems
    • Trabeculae: align along stress positions, creating cross-bracing for compact bone, contain irregularly arranged lamellae and osteocytes

    Bone Development and Remodeling

    • Ossification: process of bone tissue formation
    • Bone development: embryonic formation of bony skeleton, bone growth, and bone remodeling
    • Intramembranous ossification: development of bone from fibrous membrane, occurs in skull cap, facial bones, clavicles, pelvis, and scapulae
    • Endochondral ossification: replacement of hyaline cartilage with bone, most bones develop via this model

    Endochondral Ossification

    • Begins with a cartilaginous model of the bone
    • Large chondrocytes grow, creating big spaces in the middle of the bone
    • Death of chondrocytes leaves large spaces, which create a path for blood vessels to grow in
    • Blood vessels bring osteoblasts, which create ossification centers
    • Compact bone develops around the sides of the shaft
    • Bone replaces cartilage near the epiphysis
    • Secondary ossification centers are created within each epiphysis, forming the epiphyseal growth plate

    Growth in Bone Length

    • Epiphyseal cartilage (near epiphysis) of the epiphyseal plate divides to create more cartilage
    • Diaphyseal cartilage (near diaphysis) of the epiphyseal plate is transformed into bone, increasing shaft length

    Growth in Bone Thickness

    • Osteoblasts beneath the periosteum secrete bone matrix on the external surface of the bone, making it thicker.
    • Osteoclasts on the endosteum break down bone and widen the medullary cavity, resulting in an increase in shaft diameter.
    • At puberty, growth in bone length is increased dramatically by the combined activities of growth hormone, thyroid hormone, and the sex hormones.

    Bone Remodeling

    • Bone is a dynamic tissue that grows or remodels in response to the forces or demands placed upon it (Wolff's law).
    • Bone remodeling allows the skeleton to respond to mechanical loading, repair and prevent microdamage, and release growth factors and minerals stored in bone matrix to the circulation.
    • The process involves osteoclastic cells mediating the first phase of remodeling, followed by osteoblasts forming new bone that replaces the resorbed bone.
    • The sequence takes 4 to 6 months.

    Nutritional and Hormonal Effects on Bone

    • Bone density is governed by the amount of available calcium, phosphorus, vitamin D, and parathyroid hormone.
    • Normal bone growth and maintenance require sufficient dietary intake of calcium and phosphate salts.
    • Vitamins C, A, K, and B12 are necessary for bone growth.
    • Calcium is essential for bone growth, with 99% found in bone and teeth, and the remaining 1% in blood and extracellular fluid.

    Clinical Conditions

    • Osteomalacia: a term that encompasses many disorders in which osteoid is produced but inadequately mineralized, causing "soft bones".
    • Rickets: the children's form of osteomalacia, characterized by bowed legs, and deformities of the pelvis, ribs, and skull.
    • Osteoporosis: a group of diseases in which bone resorption occurs at a faster rate than bone deposition, leading to porous bones and increased risk of fractures.
    • Primary hyperparathyroidism: excessive secretion of parathyroid hormone, leading to elevated calcium levels and symptoms such as bone pain, fatigue, and GI complaints.

    Hormonal Effects on Bone

    • Insulin stimulates bone formation, while glucocorticoids stimulate osteoclast activity.
    • Parathyroid hormone and calcitonin antagonistically maintain blood calcium levels at homeostatic levels.
    • Parathyroid hormone increases calcium levels in response to low blood calcium, while calcitonin lowers calcium levels when they are too high.
    • Growth hormone and thyroid hormone stimulate bone growth, especially during pre-adolescence.
    • Sex hormones, particularly estrogen, stimulate bone growth and closure of the epiphyseal plate during adolescence.

    Fracture Repair

    • Fractures can occur due to extreme loads, sudden impacts, or stresses from unusual directions.
    • Fracture types include open, closed, comminuted, greenstick, spiral, and impacted.
    • Fracture repair involves four stages: inflammation, granulation tissue formation, bony callus formation, and remodeling.
    • Avascular necrosis can occur if the vascular supply to the bone is interrupted and not restored, leading to bone death.

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    This quiz covers the stages of nervous system development from embryonic ectoderm, including neural tube formation, neuronal proliferation, and myelination. Test your knowledge of this complex process!

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