Nervous System Overview

Nervous System

• CAD Diagnosis: Physical exam (listening to carotid artery with stethoscope for bruit), carotid ultrasound (sound waves to create images of carotid arteries and plaque), MRI, CT, and CT angiography (contrast dye to create images of carotid arteries).

• Neurons: Fundamental unit of the nervous system, specialized cells for receiving, processing, and transmitting information throughout the body. Communicate with electrochemical signals.

• Basic Structure:

• Soma: Cell body (nucleus and organelles).

• Dendrites: Finger-like extensions of the soma 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, includes sensory neurons (transmit impulses from peripheral sensory receptors to the CNS), interneurons (decision-making neurons), and motor neurons (transmit impulses from the CNS to an effector organ).

• Motor Neurons:

• Transmit impulses from the CNS (brain and spinal cord) to an effector organ (muscles and glands).

• Transmitted by the efferent pathway

• Primary function to initiate and control movements.

Cerebellum

• Maintains balance and posture.
• Damage results in ipsilateral (same side) loss of equilibrium, balance, and motor coordination.
• Conscious and unconscious muscle synergy.

Occipital Lobe

• Maps the visual world.
• Determines color properties, size, depth/distance.
• Identifies visual stimuli.
• Transmits visual information to other brain regions.

Frontal Lobe

• Coordinates voluntary movements.
• Assesses the future consequences of current actions.
• Forms and retains long-term memories.
• Responsible for language.
• Involved in emotional expression and regulation, and personality development.

Meninges

• Protective membrane surrounding the brain and spinal cord.
• Dura mater: Tough outermost layer adhering to the skull.
• Arachnoid mater: Thin, impermeable layer beneath dura mater.
• Pia mater: Thin, vascular layer closely adhering to the brain and spinal cord.
• Has three spaces, subdural, subarachnoid, and epidural.

CSF

• Clear, colorless fluid similar to blood plasma, found in subarachnoid space.
• Prevents brain from tugging on meninges, nerve roots and blood vessels.
• Produced in choroid plexuses and reabsorbed in the arachnoid villi.
• Exerts pressure within the brain and spinal cord.

Afferent Pathway

• Ascending pathway carries information from sensory receptors to the spinal cord.
• Sends impulses to the CNS via sensory neurons.

Efferent Pathway

• Descending pathway carries information from the CNS to muscles and glands.
• Impulses transmitted to effector organs via motor neurons.

Stroke Risk Factors

• Age over 55
• Family history
• Race (African American, Hispanic, Native American)
• Sex
• Hypertension
• High cholesterol
• Heart disease
• Diabetes
• Smoking
• Obesity
• Poor diet
• Sleep apnea
• Drug usage

Stimulation of Sympathetic Nervous System

• Decreases peristalsis.
• Increases blood pressure, body temperature, and blood sugar level.
• Regulates vasomotor tone.

Stimulation of Parasympathetic Nervous System

• Promotes rest and tranquility ("rest and digest").
• Reduces heart rate.
• Enhances digestive processes.
• Controls pupil constriction and tear secretion.
• Increases salivary secretion.
• Contracts the urinary bladder.

Dermatome

• Area of skin on your body that relies on specific nerve connections on your spine, having a single sensory nerve fiber.

Dementia

• Progressive failure of many cerebral functions causing impairment.
• Onset is gradual.
• Progressive dementia produces nerve cell degeneration and brain atrophy.
• Age is the greatest risk factor.
• Pathologies can include compression of brain tissue, genetic predisposition, CNS infections, brain trauma, neuron degeneration, and atherosclerosis of cerebral vessels.
• Symptoms include impairment of intellectual function, memory, language, and alterations in behavior.

Musculoskeletal System

Articular Cartilage

• Type of hyaline cartilage covering the ends of bones.
• Reduction of friction in the joint.
• Distribution of weight-bearing forces.
• Has chondrocytes, intercellular matrix (collagen, polysaccharides, water).
• No blood vessels, lymph nodes, or nerves (insensitive to pain).
• Regenerates slowly.
• Layered structure.

Surface Layer

• Dense protective layer.
• Middle layer: Interlaced fibers for weight bearing.
• Perpendicular fibers resisting shear forces.
• Calcified layer anchors structure to the bone.

Pennate Muscles

• Broad, flat, and slightly fan-shaped.

Fusiform Muscles

• Elongated, strap-shaped, running from one joint to another.

Sensory Receptors

• Spindles: Mechanoreceptors responding to muscle stretching.
• Responsible for muscle stretch response and maintaining muscle tone.

Oxygen Debt

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

Effects of aging on the musculoskeletal system

• Bones: Loss of bone tissue, stiffness, brittleness, decreased strength, lengthened bone remodeling cycle, slow mineralization, evidence of osteoporosis, increased bone resorption.
• Joints: Degenerative change in cartilage (more rigid, fragile, stiff), increased risk of fraying, decreased range of motion.
• Muscles: Apoptosis of cells, sarcopenia (loss of muscles), decreased muscle strength and bulk, reduced oxygen intake, altered basal metabolic rate, reduced lean body mass.

Amphiarthrosis

• Slightly moveable joint, examples include intervertebral disks, ribs, and pelvis joints.

Comminuted Fracture

• Bone fracture into more than two fragments.

Phases of healing in a fracture:

• Inflammatory phase: lasts 3-4 days, bone tissue destruction triggers an inflammatory response, hematoma formation.
• Repair phase: lasts several days.

Capillary Ingrowth, mononuclear cells, and fibroblasts

• Transform hematoma into granulation tissue.
• Osteoblasts synthesize collagen and matrix to form callus.

Remodeling Phase

• Unnecessary callus is resorbed and trabeculae are formed.
• The bone can withstand normal stress at the end of the process.

Gout

• Metabolic disorder disrupting uric acid control in blood and body fluids.
• High levels of uric acid crystallizing (tophi).
• Low body temperature, decreased albumin or glycosaminoglycan levels, and trauma or changes in ion concentration or pH.

Pain in the great toe

• Usually worse at night.
• Increase in serum urate concentration (hyperuricemia)
• Recurrent attacks of monoarticular arthritis involving one joint.
• Deposits of tophi in and around the joints.
• Renal disease involving glomerular, tubular, and interstitial tissues and blood vessels.
• Formation of kidney stones.

Myoblasts

• Primary cells for muscle growth and regeneration.
• Aka satellite cells in an inactive state.
• Become activated to form myoblasts and assist in muscle injury repair.

Osteoarthritis

• Common age-related disorder of synovial joints.

Inflammatory Joint Disease

• AKA degenerative joint disease.
• Local areas of damage, loss of articular cartilage, bone spurs, and thickening of the joint capsule.
• General signs; Pain, stiffness, enlargement of joint, tenderness, limited motion, and deformity.
• Joint swelling (Heberden or Bouchard nodes)
• Joint Effusion (exudate or blood entering the joint).

Compact Bone

• AKA cortical bone
• 85% of the skeleton
• Solid and strong
• Haversian system: haversian canal, lamellae, lacunae, osteocytes, and canaliculi.

Long Bones

• Diaphysis: Long shaft containing fat (yellow marrow) in the medullary cavity.
• Metaphysis: Broad neck.
• Epiphysis: End of long bone. Medullary cavity contributes to blood formation (red marrow). Epiphyseal plate (growth plate) present in kids.
• Endosteum: Lines the medullary cavity.

Renal/Urinary System

• Acute Kidney Injury: Sudden decline in kidney function with decreased glomerular filtration and accumulation of nitrogenous waste products in the blood (increasing CRT & BUN). Oliguric urine output <400 ml/day.
• Tubular obstruction: Backleak of glomerular filtrate.

Chronic Kidney Disease

• Progressive loss of renal function, associated with systemic diseases.
• No symptoms until renal function drops below 25%.

ADH (Antidiuretic Hormone)

• Controls final urine concentration.
• Increases water permeability in the distal tubules and collecting ducts.
• Stimulation by angiotensin II in RAAS (renin-angiotensin-aldosterone system).
• Main function is to increase water reabsorption back into the bloodstream from the urine.

Urea

• End-product of protein metabolism.
• Major constituent of urine (50% excreted in urine, 50% recycled by kidneys).

Renal System Primary Functions (except)

• Maintains stable internal environment for optimal cell and tissue metabolism.
• Balances solute and water transport.
• Excretes metabolic waste products.
• Conserves nutrients (vitamins).
• Regulates acids and bases.
• Forms urine.
• A nephron is the functional unit of the kidney.

Glomerular Hypertension

• Increased pressure in the glomerular capillaries (caused by DM and HTN).
• Leads to hyperfiltration (increased glomerular filtration rate).

Angiotensin II

• Stimulates aldosterone secretion by adrenal cortex.

• Increases sodium reabsorption and potassium secretion.

• Increases water retention and blood volume/blood pressure.

• Powerful vasconstrictor (constricts blood vessels).

• Stimulates ADH secretion.

Loop of Henle

• Enables kidneys to concentrate urine and conserve water.
• Establishes a hyperosmotic state within the medullary interstitial fluid.
• Countercurrent exchange system—fluid moves up and down parallel loops. Longer loops result in greater concentration gradients.

Protective Urinary Mechanisms (UTIs)

• Washed out of the urethra during urination.
• Lower pH and high osmolarity of urea.
• Presence of Tamm-Horsfall protein (urothelium secretions) that is bactericidal.
• Ureteroveical Junction closes to prevent reflux.
• Women: mucus-secreting glands.
• Men: longer urethra.

Effects of aging on renal function

• Decrease in kidney size,
• Decreased renal blood flow (RBF), and glomerular filtration rate (GFR)
• Decreased number of nephrons.
• Decreased tubular transport.

Ureters

• 30 cm long, smooth muscle.
• Oblique passage through the bladder.
• Peristaltic activity moves urine.
• Micturition compresses ureter ends to prevent urine reflux.

Skin System

• Candidiasis: Normally found on skin, GI tract, and vagina; can be widespread if environment supports it (warm, moist).
• Function of fibroblasts: Secrete connective tissue matrix and collagen; help with structural integrity and tissue repair; during wound healing, they proliferate and synthesize new matrix components, helping with collagen regeneration.
• Effects of aging on skin: Skin becomes thinner, drier, wrinkled, less elastic, changes in pigment (fewer melanocytes), decreased capillary loops, reduced melanocytes and Langerhans cells, decreased sebaceous, eccrine, apocrine glands (atrophy), compromised temperature regulation, decreased pressure receptors and free nerve endings, compromised protective function (increased infections and delayed wound healing).

Erysipelas

• Acute superficial infection of upper dermis (superficial form of cellulitis).
• Tx: Cold compresses, systemic antibiotics.

Folliculitis

• Infection of hair follicles caused by staph.
• Tx: Soap, water, topical antibiotics.

Furuncles

• Inflammation of hair follicles (boils) caused by staph.
• Develop from folliculitis.

Carbuncles

• Collection of infected hair follicles (clump of boils).
• Inflammation/development of abscesses.
• Redness, painful swollen mass that drains through multiple openings.

Impetigo

• Very common infection in children.
• Superficial skin lesion caused by staph and strep.
• Highly contagious crusty lesions.

Keloids

• Elevated, rounded, firm, claw-like margins extending beyond the original site.
• Hypertrophic scars, elevated erythematous fibrous lesions.
• Excessive collagen formation and abnormal fibroblast activity.
• Common in dark-skinned individuals.
• Treated with corticosteroids, 5-FU, cryotherapy, radiotherapy, and surgical or laser procedures.

Test your knowledge on the nervous system, including neurons and CAD diagnosis methods. This quiz covers the basic structure of neurons and their functions, as well as diagnostic techniques used in neurology such as ultrasound and MRI. Perfect for students and enthusiasts alike!