TEAS Science: Human Body Systems and Anatomy 1 — Questions and Answers
Question 1: Which chamber of the heart pumps oxygenated blood to the body's systemic circulation?
- Right ventricle
- Left ventricle (Correct answer)
- Right atrium
- Left atrium
Correct answer: Left ventricle
The left ventricle pumps oxygenated blood received from the left atrium out through the aorta to the systemic circulation.
The heart has four chambers: right atrium, right ventricle, left atrium, and left ventricle. The left ventricle is the most muscular chamber because it must generate enough pressure to push blood through the entire systemic circulation. Oxygenated blood flows from the lungs into the left atrium, then into the left ventricle, which contracts to send it through the aorta to all body tissues. The right side handles deoxygenated blood going to the lungs.
Question 2: What is the primary function of the nephron in the kidney?
- Producing hormones
- Filtering blood and forming urine (Correct answer)
- Storing bile
- Regulating blood pressure only
Correct answer: Filtering blood and forming urine
The nephron is the functional unit of the kidney responsible for filtering blood, reabsorbing nutrients, and excreting waste as urine.
Each kidney contains about one million nephrons. Each nephron consists of a glomerulus (filtration unit) and a tubule (reabsorption/secretion unit). Blood is filtered under pressure in the glomerulus, and the filtrate travels through the proximal tubule, loop of Henle, distal tubule, and collecting duct. Along the way, glucose, amino acids, water, and ions are reabsorbed back into the bloodstream while waste products like urea and creatinine remain to form urine.
Question 3: Which type of muscle tissue is found in the walls of the digestive tract and blood vessels?
- Skeletal muscle
- Cardiac muscle
- Smooth muscle (Correct answer)
- Striated voluntary muscle
Correct answer: Smooth muscle
Smooth muscle is involuntary and non-striated, found in hollow organs such as the digestive tract, bladder, and blood vessels.
The three types of muscle tissue are skeletal, cardiac, and smooth. Smooth muscle lacks the striations seen in skeletal and cardiac muscle. It is under involuntary (autonomic) control and is responsible for peristalsis in the gut, vasoconstriction/dilation in blood vessels, and contraction of the bladder and uterus. Smooth muscle contractions are slower and more sustained than skeletal muscle contractions.
Question 4: The sinoatrial (SA) node is best described as the heart's:
- Oxygen reserve
- Natural pacemaker (Correct answer)
- Valve between atria and ventricles
- Blood pressure regulator
Correct answer: Natural pacemaker
The SA node is the heart's natural pacemaker, initiating the electrical impulse that triggers each heartbeat.
Located in the right atrium, the SA node spontaneously generates electrical impulses approximately 60–100 times per minute at rest. This impulse spreads across both atria, reaches the atrioventricular (AV) node, then travels down the bundle of His and Purkinje fibers to stimulate ventricular contraction. If the SA node fails, the AV node can take over at a slower rate (40–60 bpm).
Question 5: Which organ system is primarily responsible for regulating body temperature through sweating and shivering?
- Endocrine system
- Nervous system and integumentary system (Correct answer)
- Lymphatic system
- Muscular system only
Correct answer: Nervous system and integumentary system
The nervous system detects temperature changes and coordinates responses like sweating (via sweat glands in the skin/integumentary system) and shivering (via muscles).
Thermoregulation is controlled by the hypothalamus, a region of the brain that acts as the body's thermostat. When body temperature rises, the hypothalamus signals sweat glands in the skin to produce sweat (evaporative cooling) and causes vasodilation to release heat. When temperature drops, it triggers shivering (rapid muscle contractions generating heat) and vasoconstriction to conserve heat. This involves both the nervous system (control center and pathways) and the integumentary system (sweat glands, skin blood vessels).
Question 6: Where does gas exchange (oxygen and carbon dioxide) occur in the lungs?
- Bronchi
- Trachea
- Alveoli (Correct answer)
- Bronchioles
Correct answer: Alveoli
Gas exchange occurs in the alveoli, tiny air sacs with thin walls surrounded by capillaries, allowing efficient diffusion of O2 and CO2.
The alveoli are microscopic sac-like structures at the terminal end of the respiratory tree. Their walls are only one cell thick (simple squamous epithelium) and are surrounded by pulmonary capillaries. Oxygen diffuses from the alveolar air into the blood, while carbon dioxide diffuses from the blood into the alveoli to be exhaled. There are approximately 300 million alveoli in adult lungs, providing a large surface area (~70 m²) for gas exchange.
Question 7: Which part of the brain is responsible for coordinating voluntary movements and balance?
- Cerebrum
- Medulla oblongata
- Cerebellum (Correct answer)
- Thalamus
Correct answer: Cerebellum
The cerebellum coordinates smooth voluntary movements, balance, and fine motor control.
The cerebellum ('little brain') receives input from the sensory systems, the spinal cord, and the cerebral cortex. It processes this information to fine-tune motor activity, coordinate movements, and maintain posture and balance. Damage to the cerebellum results in ataxia (loss of coordination), tremors, and difficulty with fine motor tasks. It does not initiate movements — that is the cerebral cortex's role.
Question 8: The large intestine's primary function is to:
- Digest proteins
- Absorb water and form feces (Correct answer)
- Secrete digestive enzymes
- Absorb fats
Correct answer: Absorb water and form feces
The large intestine absorbs water and electrolytes from indigestible material and consolidates it into feces for elimination.
The large intestine (colon) receives the remaining undigested material from the small intestine. Its primary functions are: (1) absorbing water and electrolytes (sodium, chloride, potassium), converting the liquid chyme into semi-solid feces; (2) housing beneficial gut bacteria that ferment some fiber; and (3) storing feces in the rectum until defecation. It does not play a significant role in chemical digestion or absorption of nutrients.
Question 9: Which gland produces insulin and glucagon to regulate blood glucose levels?
- Thyroid gland
- Adrenal gland
- Pancreas (Correct answer)
- Pituitary gland
Correct answer: Pancreas
The pancreas has endocrine cells (islets of Langerhans) that secrete insulin (lowers blood glucose) and glucagon (raises blood glucose).
The pancreas has both exocrine and endocrine functions. Its exocrine portion secretes digestive enzymes into the small intestine. Its endocrine portion (islets of Langerhans) contains beta cells that secrete insulin (promoting glucose uptake by cells) and alpha cells that secrete glucagon (stimulating the liver to release glucose). Dysfunction leads to diabetes mellitus — Type 1 involves destruction of beta cells; Type 2 involves insulin resistance.
Question 10: The mitral (bicuspid) valve is located between which two heart chambers?
- Right atrium and right ventricle
- Left ventricle and aorta
- Left atrium and left ventricle (Correct answer)
- Right ventricle and pulmonary artery
Correct answer: Left atrium and left ventricle
The mitral valve sits between the left atrium and left ventricle, preventing backflow when the ventricle contracts.
The heart has four valves: the tricuspid (right AV), pulmonary (right semilunar), mitral/bicuspid (left AV), and aortic (left semilunar). The mitral valve has two cusps (leaflets) and prevents blood from flowing back into the left atrium when the left ventricle contracts. Mitral valve prolapse and mitral stenosis are common cardiac conditions affecting this valve. Its name comes from its resemblance to a bishop's miter (hat).
Question 11: Which type of joint allows the greatest range of motion?
- Hinge joint
- Pivot joint
- Ball-and-socket joint (Correct answer)
- Gliding joint
Correct answer: Ball-and-socket joint
Ball-and-socket joints (like the hip and shoulder) allow movement in all planes including rotation, providing the greatest range of motion.
Ball-and-socket joints consist of a rounded head (ball) that fits into a cup-shaped socket. Examples include the glenohumeral (shoulder) and hip joints. They permit flexion, extension, abduction, adduction, rotation, and circumduction — the widest range of motion of any joint type. In contrast, hinge joints (elbow, knee) permit only flexion and extension; pivot joints (atlantoaxial) allow rotation only; and gliding joints (intercarpal) permit limited sliding movements.
Question 12: The lymphatic system plays a critical role in:
- Digesting carbohydrates
- Filtering blood in the kidneys
- Immune defense and returning interstitial fluid to circulation (Correct answer)
- Producing red blood cells
Correct answer: Immune defense and returning interstitial fluid to circulation
The lymphatic system collects excess interstitial fluid, filters it through lymph nodes, and returns it to the bloodstream while also transporting immune cells.
The lymphatic system consists of lymph capillaries, vessels, lymph nodes, and lymphoid organs (spleen, thymus, tonsils). It performs three key functions: (1) drains excess interstitial fluid back into the venous circulation; (2) transports dietary fats absorbed in the small intestine (via lacteals) to the bloodstream; and (3) is a major component of the immune system — lymph nodes filter lymph and contain lymphocytes that attack pathogens. Swollen lymph nodes often indicate infection or immune activation.
Question 13: Which hormone is produced by the adrenal medulla in response to stress?
- Cortisol
- Aldosterone
- Epinephrine (adrenaline) (Correct answer)
- Testosterone
Correct answer: Epinephrine (adrenaline)
The adrenal medulla releases epinephrine (adrenaline) and norepinephrine as part of the 'fight-or-flight' stress response.
The adrenal gland has two parts: the cortex and medulla. The adrenal medulla is derived from neural tissue and secretes catecholamines — primarily epinephrine and norepinephrine — in response to sympathetic nervous system activation during acute stress. These hormones increase heart rate, dilate airways, redirect blood to muscles, and elevate blood glucose. The adrenal cortex (not medulla) produces cortisol, aldosterone, and androgens.
Question 14: The process by which bone tissue is broken down and rebuilt throughout life is called:
- Ossification only
- Bone remodeling (Correct answer)
- Calcification
- Chondrogenesis
Correct answer: Bone remodeling
Bone remodeling is the continuous process of bone resorption by osteoclasts and bone formation by osteoblasts.
Bone remodeling involves two types of cells: osteoclasts (break down bone matrix releasing calcium) and osteoblasts (build new bone matrix). This process allows bones to respond to mechanical stresses, repair microfractures, and regulate blood calcium levels. Approximately 10% of the adult skeleton is remodeled each year. Imbalance — more resorption than formation — leads to osteoporosis. Hormones like parathyroid hormone (PTH), calcitonin, and estrogen regulate this balance.
Question 15: Which part of the neuron receives incoming signals from other neurons?
- Axon
- Myelin sheath
- Dendrite (Correct answer)
- Axon terminal
Correct answer: Dendrite
Dendrites are the branched extensions of a neuron that receive incoming signals (synaptic inputs) from other neurons and transmit them toward the cell body.
A neuron consists of a cell body (soma), dendrites, and an axon. Dendrites are highly branched extensions that increase the surface area for receiving synaptic inputs from thousands of other neurons. Signals received by dendrites are integrated at the axon hillock, and if threshold is reached, an action potential travels down the axon to the axon terminals, where neurotransmitters are released to communicate with the next neuron or effector organ.
Question 16: The skin's outermost layer, which acts as a barrier against pathogens and water loss, is the:
- Dermis
- Hypodermis
- Epidermis (Correct answer)
- Subcutaneous layer
Correct answer: Epidermis
The epidermis is the outermost layer of skin, composed mainly of keratinocytes, providing a waterproof barrier.
The skin (integument) has three layers: epidermis (outermost), dermis (middle), and hypodermis/subcutaneous (deepest). The epidermis is avascular (no blood vessels) and consists of multiple layers of keratinocytes. The outermost sublayer (stratum corneum) is composed of dead, keratinized cells that form a tough, waterproof barrier. Melanocytes in the epidermis produce melanin for UV protection. Cells originate in the deepest epidermal layer (stratum basale) and migrate upward, dying and flattening as they go.
Question 17: Which part of the brain controls vital autonomic functions such as breathing, heart rate, and blood pressure?
- Cerebral cortex
- Hypothalamus
- Medulla oblongata (Correct answer)
- Corpus callosum
Correct answer: Medulla oblongata
The medulla oblongata, part of the brainstem, contains autonomic control centers for breathing, heart rate, and blood pressure.
The medulla oblongata is the inferior portion of the brainstem. It contains the cardiac center (regulates heart rate and force), the vasomotor center (regulates blood vessel diameter and blood pressure), and the respiratory centers (controls breathing rhythm). It also controls reflexes like swallowing, coughing, sneezing, and vomiting. Because the medulla controls these vital functions, injury to this region — such as from a severe blow to the back of the head — can be rapidly fatal.
Question 18: Erythrocytes (red blood cells) are produced in the:
- Liver
- Spleen
- Thymus
- Red bone marrow (Correct answer)
Correct answer: Red bone marrow
Red blood cells are produced through erythropoiesis in the red bone marrow, stimulated by the hormone erythropoietin from the kidneys.
In adults, red bone marrow (found in flat bones like the sternum, vertebrae, and iliac crest, and in the epiphyses of long bones) is the site of erythropoiesis. The kidneys produce erythropoietin (EPO) when oxygen levels drop, stimulating red bone marrow to increase red blood cell production. Mature RBCs lack nuclei and organelles, maximizing space for hemoglobin. RBCs survive approximately 120 days before being recycled by the spleen and liver.
Question 19: The function of the epiglottis is to:
- Filter air entering the lungs
- Prevent food from entering the airway during swallowing (Correct answer)
- Produce mucus in the trachea
- Connect the pharynx to the esophagus
Correct answer: Prevent food from entering the airway during swallowing
The epiglottis is a flap of cartilage that covers the trachea during swallowing, directing food into the esophagus and preventing aspiration.
The epiglottis is a leaf-shaped flap of elastic cartilage attached to the entrance of the larynx. During swallowing, the larynx elevates and the epiglottis reflexively folds down over the glottis (opening to the trachea), routing food and liquids into the esophagus. When not swallowing, it remains upright, allowing airflow. Aspiration (food/liquid entering the lungs) can occur if this reflex is impaired, leading to aspiration pneumonia.
Question 20: Which structure connects a muscle to a bone?
- Ligament
- Cartilage
- Tendon (Correct answer)
- Fascia
Correct answer: Tendon
Tendons are fibrous connective tissue structures that attach muscle to bone, transmitting the force of muscle contraction to move bones.
Tendons are composed primarily of densely packed collagen fibers (type I collagen) arranged in parallel, making them strong and relatively inextensible. They transmit the mechanical force of muscle contraction to bones, producing movement. Common examples include the Achilles tendon (gastrocnemius to calcaneus) and the patellar tendon (quadriceps to tibia). In contrast, ligaments connect bone to bone at joints and provide joint stability. Tendon injuries include strains and ruptures.
Question 21: Bile, which helps emulsify fats in the small intestine, is produced by the:
- Pancreas
- Stomach
- Liver (Correct answer)
- Gallbladder
Correct answer: Liver
Bile is produced by liver hepatocytes and stored in the gallbladder; it is released into the duodenum to emulsify dietary fats.
Hepatocytes (liver cells) continuously produce bile, which contains bile salts, cholesterol, bilirubin, phospholipids, and water. Bile is stored and concentrated in the gallbladder between meals. When fatty food enters the duodenum, cholecystokinin (CCK) triggers gallbladder contraction, releasing bile through the common bile duct into the duodenum. Bile salts emulsify large fat globules into smaller droplets (emulsification), increasing the surface area for lipase enzymes to digest fats.
Question 22: Which blood vessels carry blood AWAY from the heart?
- Veins
- Capillaries
- Venules
- Arteries (Correct answer)
Correct answer: Arteries
Arteries carry blood away from the heart (regardless of whether the blood is oxygenated or deoxygenated).
Arteries carry blood away from the heart and must withstand high pressure, which is why they have thick, elastic, muscular walls. The aorta is the largest artery. Arteries branch into smaller arterioles, then into capillaries where gas and nutrient exchange occur. Blood returns to the heart through venules and veins. A common misconception is that arteries always carry oxygenated blood — the pulmonary arteries carry deoxygenated blood from the right ventricle to the lungs, but they are still arteries because they carry blood away from the heart.
Question 23: The hormone responsible for the 'fight-or-flight' response is primarily released by the:
- Thyroid gland
- Anterior pituitary
- Adrenal medulla (Correct answer)
- Pineal gland
Correct answer: Adrenal medulla
The adrenal medulla releases epinephrine and norepinephrine, triggering the fight-or-flight response to perceived threats.
When the sympathetic nervous system is activated by stress, preganglionic neurons directly stimulate the adrenal medulla (which is essentially a modified sympathetic ganglion) to release epinephrine (~80%) and norepinephrine (~20%). These catecholamines cause: increased heart rate and blood pressure, bronchodilation (easier breathing), glycogenolysis (releasing glucose for energy), pupil dilation, and decreased digestive activity. This prepares the body for rapid physical response to a threat.
Question 24: Which structure in the ear is responsible for maintaining balance and equilibrium?
- Cochlea
- Tympanic membrane
- Semicircular canals (Correct answer)
- Ossicles
Correct answer: Semicircular canals
The semicircular canals in the inner ear detect rotational movements and contribute to balance and equilibrium.
The vestibular system, located in the inner ear, includes the three semicircular canals (oriented in three planes) and the otolith organs (utricle and saccule). The semicircular canals detect rotational acceleration through movement of endolymph fluid over hair cell receptors (cristae). The utricle and saccule detect linear acceleration and head position relative to gravity. Signals are sent via the vestibulocochlear nerve (CN VIII) to the brain to coordinate balance, posture, and eye movements.
Question 25: The periosteum is:
- The inner cavity of bones containing marrow
- A dense fibrous membrane covering the outer surface of bone (Correct answer)
- The cartilage cap at the ends of long bones
- The network of canals inside compact bone
Correct answer: A dense fibrous membrane covering the outer surface of bone
The periosteum is the dense, fibrous connective tissue membrane covering the outer surface of bone (except at articular cartilage).
The periosteum consists of an outer fibrous layer (collagen fibers for attachment of tendons and ligaments via Sharpey's fibers) and an inner cellular (osteogenic) layer containing osteoprogenitor cells that can differentiate into osteoblasts. The periosteum is richly supplied with nerves and blood vessels that penetrate the bone. It is essential for bone growth in diameter (appositional growth), fracture repair, and bone nutrition. That's why fractures are so painful — the periosteum has many pain receptors.
Question 26: Antidiuretic hormone (ADH) acts on which organ to reduce urine output?
- Liver
- Stomach
- Kidney (Correct answer)
- Bladder
Correct answer: Kidney
ADH (vasopressin) acts on the collecting ducts of the kidneys, increasing water reabsorption and reducing urine volume.
ADH (vasopressin) is produced in the hypothalamus and released from the posterior pituitary gland when blood osmolality rises (dehydration) or blood volume falls. It binds to receptors on cells of the renal collecting ducts, causing insertion of aquaporin water channels into the cell membrane, dramatically increasing water permeability. Water is reabsorbed into the blood, producing concentrated urine. Alcohol suppresses ADH release, causing increased urination (diuresis). Diabetes insipidus results from ADH deficiency, causing excessive dilute urine output.
Question 27: The functional unit of skeletal muscle that generates contraction is the:
- Myosin filament
- Sarcomere (Correct answer)
- Motor unit
- Neuromuscular junction
Correct answer: Sarcomere
The sarcomere is the basic contractile unit of skeletal muscle, bounded by Z-lines and containing overlapping actin and myosin filaments.
Sarcomeres are arranged in series along myofibrils inside muscle fibers. Each sarcomere is bounded by Z-discs (lines) and contains: thin actin filaments anchored to the Z-discs, thick myosin filaments in the center, I-bands (actin only), A-band (overlapping actin and myosin), H-zone (myosin only), and M-line (center). During contraction, myosin heads bind to actin, forming cross-bridges, and use ATP to pull actin filaments toward the center — the sliding filament theory. This shortens the sarcomere, contracting the muscle.
Question 28: Which digestive organ is responsible for the majority of nutrient absorption?
- Stomach
- Large intestine
- Small intestine (Correct answer)
- Esophagus
Correct answer: Small intestine
The small intestine absorbs approximately 90% of all nutrients (proteins, fats, carbohydrates, vitamins, minerals) into the bloodstream.
The small intestine (duodenum, jejunum, ileum) is approximately 6 meters long and is highly specialized for absorption. Its surface area is maximized by three structural features: (1) plicae circulares (circular folds of mucosa), (2) villi (finger-like projections covered in epithelial cells), and (3) microvilli (brush border on each epithelial cell). These increase surface area up to ~600-fold over a simple tube. Carbohydrates and proteins are absorbed primarily in the jejunum; fats are absorbed via lacteals; B12 and bile salts are reabsorbed in the ileum.
Question 29: The corpus callosum is a structure that:
- Regulates hunger and thirst
- Connects the two cerebral hemispheres (Correct answer)
- Controls the sleep-wake cycle
- Processes visual information
Correct answer: Connects the two cerebral hemispheres
The corpus callosum is a large band of white matter connecting the left and right cerebral hemispheres, allowing communication between them.
The corpus callosum is the largest white matter structure in the brain, consisting of approximately 200–250 million axonal fibers. It connects corresponding regions of the left and right cerebral hemispheres, enabling interhemispheric communication and coordination. 'Split-brain' patients (whose corpus callosum was surgically severed to treat epilepsy) demonstrated that the two hemispheres can function somewhat independently. The corpus callosum plays roles in language, motor coordination, and sensory processing across the midline.
Question 30: Which hormone stimulates milk production in the mammary glands?
- Oxytocin
- Prolactin (Correct answer)
- Estrogen
- Progesterone
Correct answer: Prolactin
Prolactin, secreted by the anterior pituitary, stimulates lactogenesis — milk production in mammary gland alveolar cells.
Prolactin is secreted by lactotroph cells in the anterior pituitary. During pregnancy, rising estrogen and progesterone inhibit milk production despite high prolactin levels. After delivery, when these hormones drop, prolactin can act and lactation begins. Suckling maintains prolactin release by reducing dopamine (prolactin-inhibiting factor) secretion from the hypothalamus. Oxytocin (from the posterior pituitary) causes milk ejection (let-down reflex) by contracting myoepithelial cells around alveoli — distinct from prolactin's role in milk synthesis.
Question 31: The pleural cavity refers to the space between:
- The two lungs
- The lung and the chest wall (pleural membranes) (Correct answer)
- The heart and the lungs
- The diaphragm and the lungs
Correct answer: The lung and the chest wall (pleural membranes)
The pleural cavity is the fluid-filled space between the visceral pleura (covers lung) and the parietal pleura (lines the chest wall).
Each lung is surrounded by two layers of pleura: the visceral pleura (adhered to the lung surface) and the parietal pleura (attached to the inner chest wall, diaphragm, and mediastinum). Between them is the pleural cavity, which contains a thin layer of pleural fluid (~5–15 mL) that reduces friction during breathing and creates surface tension that keeps the lungs expanded against the chest wall. Pneumothorax (air in the pleural cavity) breaks this seal and causes lung collapse. Pleuritis (pleurisy) is inflammation of the pleural membranes.
Question 32: Which blood type is considered the 'universal donor'?
- Type AB positive
- Type O negative (Correct answer)
- Type A positive
- Type B negative
Correct answer: Type O negative
Type O negative blood lacks A, B, and Rh antigens on red blood cells, making it safe to transfuse to most patients in emergencies.
The ABO blood type system classifies blood based on the presence or absence of A and B antigens on red blood cells. Type O blood has neither A nor B antigens, so anti-A and anti-B antibodies in the recipient won't attack the donated cells. The Rh factor (D antigen) is also critical — Rh-negative individuals can react to Rh-positive blood. Type O-negative blood has no A, B, or Rh(D) antigens, making it compatible with essentially all blood types in emergency transfusions when time prevents cross-matching. Type AB-positive is the 'universal recipient.'
Question 33: Synovial fluid is found in:
- The central canal of long bones
- Freely movable (diarthrotic) joints (Correct answer)
- The pleural cavity
- Lymph nodes
Correct answer: Freely movable (diarthrotic) joints
Synovial fluid is secreted by the synovial membrane and found in freely movable (synovial/diarthrotic) joints, lubricating the joint and nourishing articular cartilage.
Synovial joints (also called diarthrotic joints) are encapsulated by a joint capsule lined with a synovial membrane. This membrane secretes synovial fluid — a viscous, plasma-like fluid containing hyaluronic acid — which provides lubrication (reducing friction), shock absorption, and nutrients for the avascular articular cartilage. Examples of synovial joints include the knee, hip, shoulder, and elbow. Joint diseases like osteoarthritis degrade the articular cartilage, and rheumatoid arthritis inflames the synovial membrane.
Question 34: The primary structural component of red blood cells that carries oxygen is:
- Fibrinogen
- Albumin
- Hemoglobin (Correct answer)
- Globulin
Correct answer: Hemoglobin
Hemoglobin is the iron-containing protein in red blood cells that binds oxygen in the lungs and releases it to tissues.
Hemoglobin makes up about 33% of the RBC by weight. Each hemoglobin molecule consists of 4 polypeptide chains (globins), each with a heme group containing iron (Fe²⁺). Each iron ion can bind one oxygen molecule, so each hemoglobin carries up to 4 O2 molecules. In the lungs (high PO2), O2 binds to hemoglobin (forming oxyhemoglobin). In tissues (low PO2), O2 is released. Carbon monoxide (CO) binds hemoglobin ~250× more tightly than O2, displacing oxygen and causing CO poisoning. Anemia results from low hemoglobin levels or defective hemoglobin.
Question 35: Which of the following is NOT a function of the skeletal system?
- Support and structure for the body
- Producing digestive enzymes (Correct answer)
- Protecting internal organs
- Blood cell production in red bone marrow
Correct answer: Producing digestive enzymes
The skeletal system does not produce digestive enzymes — that is a function of glands like the pancreas, salivary glands, and stomach.
The skeletal system has five main functions: (1) support — provides structural framework; (2) protection — bones protect organs (skull protects brain, ribs protect lungs/heart); (3) movement — bones act as levers for muscles; (4) hematopoiesis — red bone marrow produces blood cells; and (5) mineral storage — bones store calcium and phosphorus. Digestive enzyme production is an exocrine function of the pancreas, salivary glands, stomach, and intestinal cells — entirely separate from the skeletal system.
Question 36: Which part of the brain is primarily responsible for emotion, memory formation, and the 'fight-or-flight' response?
- Cerebral cortex
- Cerebellum
- Limbic system (Correct answer)
- Brainstem only
Correct answer: Limbic system
The limbic system — including the amygdala and hippocampus — processes emotions, forms memories, and triggers the fight-or-flight response.
The limbic system sits between the brainstem and cortex and includes the amygdala (fear/emotion processing), hippocampus (memory consolidation), hypothalamus (hormonal regulation), cingulate gyrus, and others. When a threat is perceived, the amygdala triggers the hypothalamus to activate the sympathetic nervous system and adrenal medulla (fight-or-flight). The hippocampus converts short-term experiences into long-term memories — damage from Alzheimer's disease typically begins here. The limbic system interacts with the prefrontal cortex to regulate emotional responses.
TEAS Science: Human Body Systems and Anatomy 1
Which chamber of the heart pumps oxygenated blood to the body's systemic circulation?