Nervous System Overview

Nervous System

• CAD Diagnosis: Physical exam (listening to the carotid artery with a stethoscope for a bruit), carotid ultrasound (non-invasive sound wave images of carotid arteries), MRI, CT, and CT angiography (using contrast dye to image carotid arteries).

• Neurons: The fundamental unit of the nervous system, responsible for receiving, processing, and transmitting information throughout the body. Communicate by electrochemical signals.

• Basic Neuron Structure:

  • Soma (cell body): Contains the nucleus and organelles.
  • Dendrites: Branched extensions that receive signals from other neurons.
  • Axon: Carries nerve impulses away from the soma to other neurons, muscles, and glands. Action potentials start at the axon hillock. Terminal branches form synapses.
  • Multipolar Neurons: Most common type. Have sensory neurons (transmit impulses from peripheral receptors to the CNS), interneurons (decision-making neurons in the CNS), and motor neurons (transmit impulses from the CNS to effector organs).

• Motor Neurons: Transmit impulses from the CNS (brain and spinal cord) to effector organs (muscles & glands). Transmitted by efferent pathway, and primary function is initiating and controlling movement.

Upper and Lower Motor Neurons

• Upper Motor Neurons: Control fine motor movements, modify spinal reflexes, and initial paralysis followed by recovery.
• Lower Motor Neurons: Direct influence on muscles, axons in the peripheral nervous system (PNS), and permanent paralysis (destruction) if damaged.

Cerebellum

• Function: Maintaining balance and posture, coordination, conscious and unconscious muscle synergy.
• Damage: Ipsilateral loss of equilibrium, balance, and motor coordination.

Occipital Lobe

• Function: Mapping the visual world, color properties determination, assessing distance, size, and depth, identifying visual stimuli, transmitting visual info to other brain regions.

Frontal Lobe

• Function: Coordinating voluntary movements, assessing future consequences, forming long-term memories, language, emotional expression, and personality development.

Meninges

• Function: Protective membrane surrounding the brain and spinal cord. Includes dura mater (tough outer layer adhering to the skull), arachnoid mater (thin, impermeable layer beneath the dura), and pia mater (thin, vascular layer closely adhering to the brain and spinal cord). It includes the subdural space.

Cerebrospinal Fluid (CSF)

• Location: Located between the dura and arachnoid mater.
• Characteristics: Clear, colorless fluid similar to plasma; prevents brain from tugging on meninges, nerve roots, and blood vessels. Produced in the choroid plexuses and reabsorbed in the arachnoid villi; exerts pressure within the brain and spinal cord.

Afferent Pathway

• Ascending pathway carrying sensory information from peripheral sensory receptors to the CNS via sensory neurons.

Efferent Pathway

• Descending pathway carrying information from the CNS to muscles or glands; also known as motor neurons innervate effector organs, and impulses transmitted from the CNS to the effector organ via motor neurons.

Stroke Risk Factors

• Age, family history, race (African American, Hispanic, Native American), sex, hypertension, high cholesterol, heart disease, diabetes, smoking, obesity, poor diet, sleep apnea, and drug usage.

Stimulation of Nervous Systems

• Sympathetic: Decrease peristalsis, increase blood sugar levels, temperature, and blood pressure, regulates vasomotor tone.
• Parasympathetic: Promotes rest and tranquility, reduces heart rate, enhances visceral functions (digestion), controls pupil constriction, increase salivary secretion, and contract the urinary bladder.

Dermatome

• Area of skin related to specific sensory nerves originating from a particular spinal nerve level. Has a specific single sensory nerve fiber.

Dementia

• Progressive failure of many cerebral functions; onset gradual.
• Age is the greatest risk factor.
• Pathological process includes progressive nerve cell degeneration, and brain atrophy.
• Symptoms (s/s): Alterations in intellectual function, memory, and language, and behaviors.
• Treatment (Tx): No cure or specific treatment; goal is to delay the process, restore functions, and accommodate lost abilities.

Musculoskeletal System - Articular Cartilage

• Type of hyaline cartilage covering the ends of bones.
• Reduces friction in joints and distributes weight-bearing forces.
• Contains chondrocytes (cartilage cells) and intercellular matrix (collagen, polysaccharides & mostly water).

Musculoskeletal System - Muscles

• Pennate Muscles: Broad, flat, and slightly fan-shaped.
• Fusiform Muscles: Elongated, strap-like.
• Sensory Receptors (muscle stretching): Spindles are mechanoreceptors that signal the CNS and are responsible for muscle stretch response.

Musculoskeletal System - Oxygen Debt

• Amount of oxygen needed to convert the buildup of lactic acid to glucose to replenish ATP and phosphocreatine stores..

Effects of Aging on the Musculoskeletal System

• Bones: Loss of bone tissue, stiff, brittle decrease, lengthened bone remodeling cycle, slower mineralization, evidence of osteoporosis, and increased bone resorption.
• Joints: Cartilage more rigid, fragile, stiff, decreased range of motion.
• Muscles: Apoptosis of muscle cells (sarcopenia), decreased muscle strength and bulk, reduced oxygen intake, basal metabolic rate, and lean body mass.
• Amphiarthrosis: Slightly moveable joint. Examples are intervertebral disks, ribs, and pelvis joints.
• Comminuted fracture: Bone breaks in more than two fragments. Phases of healing in a fracture occur over inflammatory phase (lasting 3-4 days) and bone tissue destruction triggers inflammatory response, and hematoma formation; then the repair phase (lasting several days)..

Capillary Ingrowth & Bone Formation

• After injury, capillaries grow into the damaged area.
• Mononuclear cells and fibroblasts transform the hematoma into granulation tissue.
• Osteoblasts within the procallus synthesize collagen and matrix to form a callus.
• Unnecessary callus is resorbed, and trabeculae are formed.

Gout

• Metabolic disorder disrupting uric acid production or excretion.
• High uric acid levels in blood lead to crystallization, leading to tophi (small white nodules.)
• Symptoms (s/s): Low body temperature, decreased albumin or glycosaminoglycan levels, and changes in ion concentration and pH. Poor uric acid secretion is a cause.
• Pain usually occurs in the great toe worse at night.
• Recurrent attacks of monoarticular arthritis with inflammation in one joint, deposits in & around joints, & renal disease.
• Formation of kidney stones.

Myoblast/Osteoarthritis

• Myoblast: Primary cells for muscle growth and regeneration, also known as satellite cells in the inactive state, that become activated to form myoblast when muscle is injured; essential for repair.
• Osteoarthritis: Common age-related synovial joint disorder.

Renal/Urinary System

• Acute Kidney Injury (AKI): Sudden decline in kidney function that decreases glomerular filtration and increases accumulation of nitrogenous waste products in the blood. Increase in Creatinine (CRT) and Blood Urea Nitrogen (BUN). Oliguric <400ml urine output per day.
• Chronic Kidney Disease (CKD): Progressive loss of renal function associated with systemic diseases. No symptoms until renal function is less than 25%.

Renal System - Function of ADH

• ADH (vasopressin) controls final urine concentration; increases water permeability in distal tubules and collecting ducts, causing less urine volume. Stimulation by Angiotensin II in RAAS and encourages fluid intake.

Renal System - Urea

• End-product of protein metabolism, major urine constituent, 50% excreted in the urine, with 50% recycled in kidneys.

Renal System - Primary Function (except)

• Maintains stable internal environment (homeostasis)
• Balances solute/water transport
• Excretes waste products
• Conserves nutrients
• Regulates acids/bases
• Forms urine

Renal System - Functional Unit

• Nephron

Renal System - Chronic Kidney Disease Progression Contributing Factors

• Glomerular hypertension (increased pressure in glomerular capillaries), hyperfiltration (increased glomerular filtration rate) leading to tubulointerstitial injury, or other factors like medication, toxins, or infections, which lead to fibrosis.

Urinary Tract Infections (UTIs): Protective Mechanisms

• Washed out during urination, low pH and high osmolarity of urea, presence of Tamm-Horsfall protein, secretions from the urothelium, and the ureterovesical junction (to prevent reflux).

Effects of Aging on Renal Function

• Decrease in kidney size, reduced renal blood flow (RBF), and glomerular filtration rate (GFR). Decreased number of nephrons, vascular and perfusion changes, and tubule transport response alterations.

Ureters

• 30 cm long, intertwining smooth muscle bundles, pass obliquely through the bladder, and have peristaltic activity. Urine moves to the bladder, and micturition compresses the lower end of the ureter to prevent urine reflux..

Skin System

• Candidiasis: Commonly found on skin, GI tract, and vagina.
• Fibroblasts: Involved in tissue repair, secret connective tissue matrix and collagen. Contribute to structural integrity and wound healing by proliferating and synthesizing new matrix components along with laying down new collagen for tissue regeneration.
• Aging Effects on Skin: Skin becomes thinner, drier, wrinkled, less elastic, changes in pigment, fewer capillary loops, less melanocytes and langerhans cells, sebaceous, eccrine, and apocrine glands atrophy, impaired temperature regulation, depressed pressure/touch receipts, decreased protective function. Infections increase and wound healing is delayed.

Erysipelas, Folliculitis, and Furuncles

• Erysipelas: Acute, superficial infection of upper dermis/superficial form of cellulitis (tx→cold compresses & systemic antibiotics).
• Folliculitis: Infection of hair follicles ( tx→soap, water & topical antibiotics)
• Furuncles: Inflammation of hair follicles (boils) caused by bacteria (staph), developed from folliculitis.

Carbuncles and Impetigo

• Carbuncles: Collection of infected hair follicles (clump of boils), abscesses.
• Impetigo: Highly contagious, superficial skin lesions caused by staphylococcus or streptococcus.

Keloids

• Elevated, round, and firm lesions with claw-like margins. Develop beyond the original wound. hypertrophic scar, excess collagen formation, and abdominal fibroblast activity commonly in darker skin tones..

Explore the essentials of the nervous system, including neuron structure, functions, and CAD diagnosis techniques. This quiz covers different types of neurons and their roles in transmitting information throughout the body.