Human Physiology 100 - Test 2 (Muscular, Cardiovascular, Respiratory, and Digestive System)

Smooth Muscle

Non-striated muscle found in hollow organs, blood vessels, and glands; involuntary control.

Cardiac Muscle

Striated muscle found in the heart wall; involuntary control.

Skeletal Muscle

Striated muscle attached to bones; voluntary control.

Musculoskeletal System Main Functions

Allows body movement, communication, posture maintenance, respiration, blood vessel flow control, and produces body heat.

Skeletal Muscle Main Functions

Provides structural support, sites for muscle attachment, stores minerals (calcium), protects organs, produces hormones and blood cells, and stores energy (yellow bone marrow).

Muscle Fascicle

A bundle of muscle fibers within a skeletal muscle, supplied by nerves and blood vessels.

Muscle Fiber

The basic cellular unit of muscle, containing mitochondria and surrounded by a sarcolemma.

Sarcolemma

The plasma membrane surrounding a muscle fiber.

Myofibril

Long, thread-like structures within a muscle fiber, composed of repeating sarcomeres.

Thin Filament

Filament in muscle fiber primarily made of actin; interacts with thick filaments during contraction.

Thick Filament

Filament in muscle fiber primarily made of myosin; interacts with thin filaments during contraction.

Sarcomere

The basic contractile unit of striated muscle, made of overlapping thin and thick filaments.

Muscle Contraction (Sliding Filament Theory)

Muscle contraction occurs when thin and thick filaments slide past each other within the sarcomere, shortening the muscle.

Initiating Muscle Contraction (5 Steps)

1. Neuron stimulates muscle (action potential). 2. Acetylcholine (Ach) released into synaptic cleft. 3. Ach binds to receptors on sarcolemma, generating action potential. 4. Action potential triggers calcium release from sarcoplasmic reticulum. 5. Calcium binds to troponin, exposing active sites for cross-bridge formation.

Contraction Cycle (5 Steps)

1. Myosin head binds to actin (cross-bridge forms). 2. ATP released, myosin head pivots (power stroke). 3. Power stroke slides filaments, causing contraction. 4. New ATP binds, breaking cross-bridge. 5. Myosin head resets by splitting ATP.

Ending Muscle Contraction (5 Steps)

1. Ach broken down, ending action potential. 2. Sarcoplasmic reticulum reabsorbs calcium. 3. Active sites covered; cross-bridge ends. 4. Contraction stops. 5. Muscle relaxes to resting length.

Role of Calcium Ions (Ca2+)

Calcium binds to troponin, exposing active sites on actin and allowing contraction.

Role of ATP in Muscle Contraction

ATP provides energy for filament sliding and resets myosin heads; lack of ATP causes rigor mortis.

Types of Skeletal Muscle Contraction

Isotonic: Muscle changes length (concentric shortens, eccentric lengthens). Isometric: Muscle tension without length change. Tetanus: Sustained contraction from rapid stimulation.

Motor Unit

One alpha motor neuron and all the skeletal muscle fibers it innervates.

Motor Neuron

Efferent neuron transmitting signals from the CNS to muscles.

Sensory Neuron

Afferent neuron transmitting signals from the PNS to the CNS.

Somatic Nervous System

Controls voluntary muscles and sensory information.

Autonomic Nervous System

Controls involuntary body functions.

Exercise Effects on Muscle

Endurance: Increases mitochondria, myoglobin, and capillaries for better oxygen and nutrient supply. Strength: Increases muscle fiber size and number of myofibrils, but not fiber number.

Exercise Effects on Bone

Adult activity increases bone mineral density (BMD); early-life activity increases peak BMD.

Bone Response to Compression

Compression increases bone formation via osteocytes, which sense mechanical strain and trigger osteoblasts.

Body Movements

Result from coordinated muscle contractions; fiber recruitment depends on movement type and intensity.

Muscle Fiber Types

Slow-twitch (Type I): Aerobic, endurance activities. Fast-twitch (Type II): Anaerobic, short, powerful bursts.

Epimysium

Surrounds whole muscle.

Perimysium

Divides muscle into fascicles.

Endomysium

Surrounds muscle fibers.

Myofibrils

Located inside muscle fibers.

Muscle Tension Regulation

Determined by motor unit recruitment, fiber type, and sarcomere length; also influenced by calcium and cross-bridge cycling.

Cardiovascular System

A circulating transport system that moves material to and from cells, consisting of a pump (heart), conducting system (blood vessels), and a fluid medium (blood).

Blood

A fluid connective tissue made of 55% plasma and 45% formed elements (erythrocytes, leukocytes, thrombocytes), responsible for transport, pH and ion regulation, clotting, defense, and temperature stabilization.

Plasma

The liquid component of blood, making up 55% of its volume, containing water, proteins, electrolytes, and other solutes.

Erythrocytes (Red Blood Cells, RBCs)

Cells responsible for oxygen and carbon dioxide transport; lack nucleus and mitochondria, have a high surface area-to-volume ratio, and live about 120 days.

Leukocytes (White Blood Cells, WBCs)

Nucleated cells involved in immune response and inflammation, including neutrophils, eosinophils, basophils, B cells, T cells, and natural killer cells.

Thrombocytes (Platelets)

Cell fragments involved in the clotting response, releasing chemicals, patching vessel walls, and contracting tissue after clot formation.

Hemocytoblasts

Stem cells in bone marrow that differentiate into myeloid or lymphoid stem cells, forming all blood cell types.

Erythropoiesis

The process of red blood cell production, regulated by erythropoietin from the kidneys in response to low oxygen or RBC count.

Blood Typing

Classification based on surface antigens (A, B, AB, O) and Rh factor on RBCs, determining compatibility for transfusions.

Rh Factor

A protein on RBCs; presence (Rh positive) or absence (Rh negative) determines blood type compatibility.

Haemostasis

The process of preventing bleeding, involving three phases: vascular, platelet, and coagulation.

Vascular Phase

Initial phase of haemostasis with vascular spasm and vasodilation to reduce blood flow and activate platelets.

Platelet Phase

Platelets adhere to damaged tissue, aggregate, and form a plug to prevent blood loss.

Coagulation Phase

Formation of a blood clot via conversion of prothrombin to thrombin, which turns fibrinogen into fibrin, creating a mesh to trap elements.

Pericardium

A fibrous collagen network lined by a double serous membrane that encloses and stabilizes the heart.

Epicardium

The outer layer of the heart wall, also known as the visceral layer of the serous pericardium.

Myocardium

The thick, muscular middle layer of the heart wall, made of cardiac muscle tissue responsible for contraction.

Endocardium

The inner layer of the heart wall, continuous with the endothelial lining of blood vessels.

Intercalated Discs

Specialized connections between cardiac muscle cells containing gap junctions and desmosomes, allowing electrical and structural connectivity.

Atria

The two upper chambers of the heart that receive blood returning to the heart.

Ventricles

The two lower chambers of the heart that pump blood out to the lungs (right ventricle) and the body (left ventricle).

Pulmonary Circuit

The pathway that carries deoxygenated blood from the right ventricle to the lungs and returns oxygenated blood to the left atrium.

Systemic Circuit

The pathway that carries oxygenated blood from the left ventricle to the body and returns deoxygenated blood to the right atrium.

Atrioventricular (AV) Valves

Valves between atria and ventricles (tricuspid on the right, mitral/bicuspid on the left) that prevent backflow into the atria.

Semilunar Valves

Valves at the bases of the large arteries leaving the heart (pulmonary and aortic) that prevent backflow into the ventricles.

Cardiac Cycle

The period from the start of one heartbeat to the start of the next, involving coordinated contraction (systole) and relaxation (diastole) of the heart chambers.

Systole

The contraction phase of the heart chambers, pumping blood out.

Diastole

The relaxation phase of the heart chambers, allowing filling with blood.

Stroke Volume (SV)

The volume of blood pumped out of each ventricle during a heartbeat; calculated as SV = EDV - ESV.

End Diastolic Volume (EDV)

The volume of blood in the ventricles after diastole (filling phase).

End Systolic Volume (ESV)

The volume of blood remaining in the ventricles after systole (contraction phase).

Cardiac Output (CO)

The amount of blood pumped by the left ventricle in one minute; calculated as CO = HR x SV.

Sympathetic Nervous System

Part of the autonomic nervous system that increases heart rate and cardiac output ("fight or flight" response).

Parasympathetic Nervous System

Part of the autonomic nervous system that decreases heart rate and cardiac output ("rest and digest" response).

Baroreceptors

Sensors in the carotid sinus and aortic arch that monitor blood pressure and help regulate heart rate and vessel diameter.

Chemoreceptors

Sensors that monitor oxygen and carbon dioxide levels in the blood, influencing cardiovascular regulation.

Arteries

Large blood vessels that carry blood away from the heart, with thick, elastic walls to withstand high pressure.

Elastic Arteries

Large arteries with many elastic fibers in the tunica media, allowing them to stretch and recoil to maintain blood pressure.

Muscular Arteries

Medium-sized arteries with a high proportion of smooth muscle, controlling blood flow to organs by vasoconstriction and vasodilation.

Arterioles

Small vessels that regulate blood flow into capillaries and control vascular resistance through vasoconstriction and vasodilation.

Vasoconstriction

Narrowing of blood vessels, increasing blood pressure and reducing blood flow.

Vasodilation

Widening of blood vessels, decreasing blood pressure and increasing blood flow.

Capillaries

The smallest blood vessels, consisting of endothelium and basement membrane, allowing exchange of nutrients and waste.

Continuous Capillaries

Capillaries with uninterrupted endothelial lining, found in the nervous system, fat, and muscle tissue.

Fenestrated Capillaries

Capillaries with pores that allow greater exchange, found in kidneys and brain.

Sinusoidal Capillaries

Capillaries with large fenestrations and incomplete basement membrane, found in liver, spleen, and bone marrow.

Venules

Small veins that collect blood from capillaries and merge to form veins.

Veins

Blood vessels that return blood to the heart, have thinner walls than arteries, contain valves, and act as blood reservoirs.

Blood Flow (Haemodynamics)

The volume of blood moving through tissue per unit time, determined by pressure and resistance.

Blood Pressure

The force exerted by blood on vessel walls, measured as systolic (during contraction) and diastolic (during relaxation) pressure.

Systolic Pressure

Peak pressure in arteries during ventricular contraction, typically 120 mmHg.

Diastolic Pressure

Minimum pressure in arteries during ventricular relaxation, typically 80 mmHg.

Pulse Pressure

The difference between systolic and diastolic pressure (typically 40 mmHg).

Mean Arterial Pressure (MAP)

Average pressure in arteries during one cardiac cycle; calculated as MAP = diastolic pressure + (pulse pressure/3).

Venous Return

The volume of blood returning to the right atrium from systemic veins, directly affecting cardiac output.

Skeletal Muscle Pump

Muscle contractions that help push blood through veins toward the heart.

Respiratory Pump

Mechanism where breathing movements help return blood to the heart by reducing thoracic pressure.

Capillary Exchange

Movement of substances between blood and tissues via diffusion, transcytosis, and bulk flow (filtration and absorption).

Filtration (in Capillaries)

Movement of fluid out of capillaries due to hydrostatic pressure.

Absorption (in Capillaries)

Movement of fluid into capillaries due to osmotic pressure, mainly from plasma proteins.

Edema

Abnormal increase in interstitial fluid volume caused by imbalance between filtration and absorption.

Arrhythmias

Abnormal heart rhythms, such as atrial fibrillation, premature ventricular contractions, ventricular tachycardia, and ventricular fibrillation.

Cardiovascular Regulation

Homeostatic mechanisms ensuring adequate tissue perfusion, primarily regulated by MAP = CO x TPR.

Autoregulation

Local control of blood flow by tissues, adjusting vessel diameter in response to metabolic needs.

Neural Mechanisms

Regulation of cardiovascular function via the medulla oblongata, controlling heart rate, contractility, and vessel diameter.

Hormonal Mechanisms

Regulation by hormones such as adrenaline, antidiuretic hormone, angiotensin II, and erythropoietin, affecting blood pressure and volume.