Musculoskeletal System Overview

Musculoskeletal System

• Hematopoietic stem cells reside in the bone marrow
• Hematopoietic stem cells give rise to all types of blood cells.
• Muscle fibers are single cells with multiple nuclei.
• Troponin is a protein complex, located in striated muscle
• Tropomyosin regulates the interaction between actin and myosin filaments.
• Tropomyosin plays a crucial role in muscle contraction.
• The sliding filament model involves thin filaments sliding across thick filaments.
• The sliding filament model shortens the sarcomere without shortening the filaments.
• Bones provide support, protection, and facilitate movement.
• Bones serve as sites for mineral storage and blood cell formation.
• Blood cell formation occurs in marrow cavities.
• Bones facilitate fat storage within the marrow.
• The axial skeleton includes the skull, vertebral column, ribs, and sternum.
• The appendicular skeleton consists of the arms, legs, pelvic, and pectoral girdles.
• Bone shapes include flat, long, irregular, short, and sesamoid.
• Osteoprogenitor cells develop into osteoblasts.
• Osteoblasts form the bone extracellular matrix.
• Osteocytes maintain bone tissue.
• Osteoclasts function in bone resorption to breakdown the extracellular matrix.
• Compact bone makes up the hard outer layer of bones.
• Spongy bone is located in the interior and at the ends of long bones.
• Lamellae (bone cells arranged in rings) are identifiable in diagrams of bone tissue.
• Haversian canals contain blood vessels and nerves.
• Osteons are also identifiable in diagrams of bone tissue.
• Canaliculi allow nutrient and oxygen flow between cells.
• Trabeculae are found in spongy bone tissue instead of lamellae.
• Red marrow produces blood cells, while yellow marrow does not.
• All marrow is red in children.
• Red marrow is primarily in flat and irregular bones in adults.
• The diaphysis is the bone shaft.
• The epiphysis is at the end of a bone.
• Articular cartilage is present at joints.
• The medullary cavity is filled with marrow.
• Bone marrow transplants can treat leukemia, aplastic anemia, and other immune/blood disorders.
• The embryonic skeleton is made primarily of hyaline cartilage
• Ossification replaces cartilage with bone, for bone growth (length and width).
• The epiphyseal plate facilitates lengthwise bone growth.
• The epiphyseal plate closes and is replaced by bone 3-5 years after puberty.
• Widthwise bone growth involves osteoblasts forming bone; osteoclasts destroy bone.
• Osteoblasts create new bone tissue.
• Osteoclasts break down bones and remodel them.
• Parathyroid hormone activates osteoclasts in response to low calcium levels.
• Hormonal imbalances cause bone remodeling.

Bone Healing After Fracture

• Reactive stage: formation of fracture hematoma leads to bony callus formation
• Reparative phase: fibrocartilaginous callus formation
• Bone remodeling phase: final stage in bone healing

Rickets

• Rickets cause: calcium or vitamin D deficiency
• Rickets symptom: bones become soft, weak, and bend under gravity

Osteoporosis

• Osteoporosis cause: family history makes females more susceptible with age
• Osteoporosis symptom: bones become weak and brittle
• Inadequate calcium intake is a risk factor for osteoporosis.
• Correlation studies on calcium intake and bone health have yielded mixed results.

Muscle Types Comparison

• Skeletal muscles attach to bones via tendons and control voluntary body movements.
• Skeletal muscles contract due to signals from a somatic motor neuron.
• Cardiac muscle is found only in the heart and moves blood involuntarily.
• Cardiac muscle can contract without neuronal signals and are controlled by the autonomic branch of the nervous system.
• Smooth muscle lines the GI tract and blood vessels, and influences involuntary movement of materials.
• Smooth muscle contraction is controlled by the autonomic branch of the nervous system.

Skeletal Muscle Fiber Structures

• T-tubules spread electrical signals.
• Sarcoplasmic reticulum stores Ca2+.
• Myofibrils contain contractile proteins.
• Mitochondria produce ATP.
• Glycogen stores glucose.
• Thick filaments contain myosin protein.
• Thin filaments contain actin protein and regulatory proteins.
• The two myosin head binding sites: ATP and actin binding sites
• Motor neurons initiate skeletal muscle contraction.
• Acetylcholine is the neurotransmitter for initiating skeletal muscle contraction.

Excitation-Contraction Coupling

• Action potential spreads along the sarcolemma to the T-tubules.
• Calcium is released into the sarcoplasmic reticulum.
• Calcium binds to actin, removing tropomyosin's blocking action.
• Myosin heads attach to begin contraction.
• Calcium is removed, and tropomyosin blocks actin binding sites again.
• The muscle then relaxes.
• Troponin and tropomyosin regulate skeletal muscle fiber contraction.
• Calcium ions control the interaction between actin and myosin.

Contraction Cycle

• Active site on actin is exposed as Ca2+ binds troponin.
• Myosin head forms a cross-bridge with actin.
• ATP attaches to the myosin head, which detaches the cross-bridge.
• ATP hydrolysis returns myosin to the "cocked" position.

Respiratory System Terms

• Ventilation facilitates the exchange of air between lungs and the atmosphere.
• The mucociliary escalator entraps inhaled debris via mucus, then cilia moves debris to the pharynx.
• Saline (water + NaCl) thins mucus.
• Components of respiration: ventilation, O2 and CO2 exchange, O2 and CO2 transport, and cells exchange of O2 and CO2
• The nasal cavity is the primary site for breathing.
• The larynx contains the vocal cords to allow vocalization.
• The trachea leads to primary, secondary, and tertiary bronchi.
• Alveoli are at the end of bronchioles.
• Diaphragm facilitates breathing.
• Pulmonary capillaries participate in gas exchange.
• Trachea and bronchi are held open by cartilage rings to keep airways open.
• Bronchiole diameter adjusts to remove harmful substances
• Gas exchange in alveoli delivers oxygen and removes carbon dioxide.
• Mucus protects the respiratory system and traps microorganisms; cilia moves the mucus to the pharynx.

Lung Volumes

• Tidal volume is the normal amount of air that comes in and out of lungs of a regular breath.
• Inspiratory capacity is the maximum air volume that can be inhaled after a normal exhale.
• Inspiratory reserve volume is the additional breath that can be inhaled.
• Expiratory reserve volume is the amount of air that can forcefully exhaled.
• Residual volume is the air remaining in the lungs after maximum forced exhalation.
• Total lung capacity is the total lung size or amount of air that can be put into the lungs.
• During inhalation, the diaphragm contracts (moves down) and the rib cage expands.
• Diaphragm relaxes (moves up) to reduce rib cage size during normal exhalation.
• P1V1=P2V2: Mathematical relationship between lung pressure and lung volume
• Abdominal muscles are used for intense breathing.
• Diaphragm and intercostal muscles are used for normal breathing.
• Changes in blood pH reflect carbon dioxide (CO2) levels, which monitors respiratory function.
• Carotid artery pH sensors send signals to the brain.
• Hyperventilation: lowers your CO2, breathing abnormally and quickly and raises your pH levels.
• Surfactant reduces surface tension in alveoli.
• Type 2 alveolar cells produce surfactant at 25-34 weeks of gestation.
• Oxygen enters and exits blood vessels due to partial pressure differences.
• Patm refers to atmospheric pressure.

Respiratory System Pathologies

• Asthma: increased airway resistance decreases alveolar ventilation
• Cystic fibrosis: genetic mutation that affect their ability to make saline which causes repeat respiratory infections
• Infant respiratory distress syndrome
• Emphysema: destruction of alveoli means less surface area for gas exchange
• Fibrotic lung disease: thickened alveolar membrane slow gas exchange loss of lung compliance and may decrease alveolar ventilation
• Pulmonary edema: fluid in interstitial space increases diffusion distance

Hemoglobin Structure and Function

• Hemoglobin A comprises protein globin chains with a heme group.
• Adult hemoglobin has 2 alpha and 2 beta chains.
• The iron atom is found in the heme group.
• Pulse oximetry measures hemoglobin color using light sensors to measure the color of hemoglobin
• Oxygenated hemoglobin presents a bright red, while deoxygenated hemoglobin is a dark red.
• Hemoglobin oxygen binding is determined by pH, carbon dioxide, and temperature.
• Carbon monoxide has higher affinity and displacing oxygen from hemoglobin.
• Fetal hemoglobin binds oxygen more strongly transfer of oxygen from mother to fetus.
• Carbon dioxide is transported primarily as bicarbonate ions in the blood.
• Carbon dioxide dissolves better in water than oxygen.
• Bicarbonate helps resist pH changes in solution.

Circulatory System Definitions

• Septum: the heart wall (10.1)
• Veins carry blood towards the heart.
• Arteries carry blood away from the heart.
• Capillaries allows for exchange
• Plasma is the liquid part of blood..
• The cardiac cycle is contraction and relaxation patterns in the heart.
• Systole is contraction.
• Diastole is relaxation.
• If SA node fails, AV node can work as pacemaker: junctional rhythm (50 bpm)
• Artificial pacemakers may have an internal defibrillator.
• Defibrillators (10.4) are used to correct heart rhythms.
• Systolic blood pressure (bp) results during ventricular systole.
• Diastolic blood pressure is bp during ventricular diastole.
• A thrombus is a blood clot.
• An embolus is a free thrombus.
• The Circulatory system pumps blood to transport oxygen and nutrients, hormones, gasses, and waste products.
• The systemic circuit is deoxygenated, while the pulmonary circuit is oxygenated.
• The systemic circuit pumps to the pulmonary circuit.
• Blood enters the atria and leaves from the ventricles on the left side of the heart.
• The diagram structures: right/left atrium, right/left ventricle, AV valves, and semilunar valves

Blood Composition and Function

• Blood is 55% plasma and 45% cells.
• Erythrocytes transport O2 and some CO2.
• Platelets clot blood.
• Leukocytes provide defense and immunity.
• Erythrocytes contain hemoglobin.
• Erythropoietin increases erythrocyte production to increase the oxygen capacity in the tissues
• The ABO blood groups presence of A or B antigen in the cell.
• O type is the universal donor.
• Thrombin triggers blood clotting.
• Platelets are involved in hemophilia
• Hemophilia is an X-linked genetic disorder that affects the clotting factor genes.
• Valves ensure unidirectional blood flow in the correct direction.
• AV valves open when atrial pressure exceeds ventricular pressure
• To close AV valves atrial pressure is less than ventricular pressure.
• Semilunar valves open when ventricles contract increases intraventricular pressure.
• To close semilunar valves, the ventricles relax, decreasing the pressure.
• Heart valves can be damaged as they are constantly under pressure.
• A heart murmur results from noisy valves.
• Valve therapies are surgically replaced with cadaver or artificial valves
• The SA node generates electrical signals that then travel to the AV node which serves as a gatekeeper.
• Both the SA and AV nodes can generate their own electrical signals.
• The AV node delays and routes signals to ensure atrial contraction and blood emptying before ventricular contraction.

Arrhythmias

• Ventricular fib: life-threatening emergency, can sometimes be corrected with a defibrillator or CPR
• Atrial fibrillation: can cause dizziness and fainting
• Heart block: signals distribution through AV node; atria and ventricles follow separate rhythms
• Tachycardia: overly rapid heart rate
• Bradycardia: too slow heart rate
• Junctional rhythm: bradycardia that AV node causes (50 bpm); if the SA node fails Hypertension can cause heart attack, stroke, kidney failure, and blood vessel rupture.
• Risk factors of hypertension: genetics, overweight, and high sodium diet.
• Hypotension causes impaired blood flow and dizziness or fainting.
• Shock: circulatory failure that can result from loss of blood, immune reactions, bacterial infections etc
• As blood travels from arteries to veins blood pressure goes down due to vascular resistance.
• Blood pressure fluctuates in systemic arteries and arterioles.
• A sphygmomanometer is used to measure blood pressure, it inflates to stop the flow of blood in the artery.
• Systemic veins have valves to and muscle contraction keep blood flowing back to the heart as well as respiratory changes that create pressure gradients
• Prolonged inactivity leads to blood clots due to slow blood flow
• During exercise, extra blood sourced from organs such as the digestive system and skin tissues, which experience less blood flow
• Fenestrations and intercellular clefts increase permeability of capillary walls.
• Blood pressure pushes fluid out, while osmotic pressure draws fluid back in.
• Edema (swelling) results from accumulating fluid in tissues.
• Edema is can arise from inflammation, high blood pressure, protein starvation, and blocked lymphatic vessels
• The lymphatic system is a vessels that absorb fluid and return it to the cardiovascular system and plays for immunity.
• Atherosclerosis: plaque buildup that restricts blood flow and causes tissue damage
• Stents widen narrowed arteries.
• Myocardial infarction (heart attack) blocks blood flow, leads to permanent muscle damage,.to the heart
• Angina, chest pain which can accompany heart attacks, relates to coronary artery disease.
• Nitroglycerin treats angina by relaxing blood vessels.
• Coronary arteries are blocked due to atherosclerosis.
• CABG restores blood flow which bypasses the blocked area while using healthy blood vessel from another part of the body.
• Heart failure results from perfusing the body with blood, includes SOB, ankle/feet swelling, coughing.
• Causes for heart failure: myocardial infarction, smoking, hypertension, congenital heart defects.
• Congenital heart defects are a leading cause of childhood death.
• Prevalence of congenital defects around 1% of live births.
• Septal defects are the most common congenital defect.

Excretory System

• Micturition is the process of urinating.
• Diuresis is the removal of excess water in urine.
• Hypernatremia is too much sodium.
• Hyponatremia is too little sodium.
• Osmoregulation maintains a stable internal environment by regulating water and electrolyte balance.
• It also maintains cell function/organ perfusion and creates a balanced homeostasis to prevent cell swelling.
• Functions of kidney: extracellular fluid volume/blood pressure regulation, osmolarity/ion balance regulation, pH regulation, and waste excretion
• Urine indicates bloodstream-borne chemicals/hormones

Urinary System

• Ureters connect the kidneys to the urinary bladder
• Urinary bladder stores urine.
• Urethra conducts urine outside for micturition.
• Kidneys filter urine.
• Filtration: blood minus cells/proteins enters nephron at Bowman’s capsule
• Reabsorption: wanted substances transported back into blood in excretory tubule
• Secretion: substances not initially filtered transported into nephron
• Excretion: urine leaves kidney and body
• Renal arteries deliver blood.
• Renal veins collect blood, which carries to the inferior vena cava
• Kidneys account for 0.4% of body weight and receive 20-25% of cardiac output.
• Filtrate is blood without proteins/cells containing 20% of glomerulus fluid and 80% continues.
• High blood pressure damages glomerular capillaries and results in proteins in filtrate.
• Factors controlling GFR are blood flow to the kidneys and blood pressure.
• Without water reabsorption: 180L filtrate is excreted; water reabsorption accounts for 1.5L of urine.
• High daily filtration rate: efficient clearance of body waste

Secretion

• Transfers molecules
• K+
• H+
• Na+ transports in nephron to aids water reabsorption and balance osmotic pressure.
• Glucose excretes in urine in patient with uncontrolled diabetes.
• Glucose excreted: glucose levels exceed renal threshold.
• Water balanced on 24-hour schedule tightly controls deficits and excesses
• Water loss comes water gain includes: skin, lungs, urine, feces and food, drink, metabolism
• Kidneys conserve fluid which adjusts glomerular filtration rate.
• The kidneys regulate urine concentration by altering Na+ and water reabsorption.
• ADH regulates urine concentration which by increasing water permeability in the collecting duct.
• Triggers for ADH are: increased plasma osmolarity, increased Na+ in plasma, and also decreased plasma volume
• Aquaporins transport water down concentration gradient.
• Sodium drives water transport and maintains overall osmolarity.

Aldosterone

• Aldosterone increases Na+ reabsorption and K+ secretion.
• Allosteron raises blood pressure/increases blood volume.
• Renin from the kidneys activates angiotensin 1 that is activated by ACE becomes angiotensin 2.
• Angiotensin II stimulates aldosterone release from adrenal cortex.
• Angiotensin II increases blood volume/osmolarity.
• Atrial natriuretic peptide decreases blood volume/pressure.