TEAS Test of Essential Academic Skills - Set 3 - Part 2

Correct Answer: Medulla oblongata

The medulla oblongata, located at the lower brainstem, contains centers that control vital involuntary functions including breathing rate, heart rate, blood pressure, and reflexes such as swallowing. Option b is incorrect because the cerebellum coordinates voluntary movement, balance, and fine motor control; it does not regulate breathing or heart rate. Option c is incorrect because the thalamus serves as a sensory relay station to the cerebral cortex; it does not control vital autonomic functions like breathing. Option d is incorrect because the cerebrum handles higher-level functions such as thought, language, and voluntary movement, not the involuntary regulation of vital signs.

Correct Answer: Axon

The axon is a long projection extending from the neuron cell body. It carries action potentials away from the soma toward axon terminals, where neurotransmitters are released. Option a is incorrect because dendrites are short branched extensions that receive incoming signals from other neurons and conduct them toward the cell body, not away. Option b is incorrect because the synapse is the gap between two neurons where neurotransmitters cross; it is a junction, not a projection of a single neuron. Option c is incorrect because the cell body, or soma, contains the nucleus and integrates signals; it does not itself function as the long signal-carrying projection.

Correct Answer: Sympathetic nervous system

The sympathetic nervous system mediates the fight-or-flight response, raising heart rate, dilating pupils, slowing digestion, and mobilizing glucose. These changes prepare the body to respond to perceived threats. Option a is incorrect because the parasympathetic system promotes rest-and-digest activities, slowing the heart, constricting pupils, and stimulating digestion, the opposite of the described response. Option b is incorrect because the somatic nervous system controls voluntary skeletal muscle movement; it does not regulate heart rate, pupil size, or digestive activity. Option d is incorrect because the central nervous system includes the brain and spinal cord; it processes signals but does not itself directly drive sympathetic responses.

Correct Answer: Acetylcholine

Motor neurons release acetylcholine at the neuromuscular junction. The acetylcholine binds receptors on the muscle fiber, triggering depolarization and calcium release that begin the contraction sequence. Option a is incorrect because dopamine is involved in movement coordination, reward, and motivation in the central nervous system, not in direct neuromuscular junction signaling. Option c is incorrect because serotonin influences mood, sleep, and appetite within the central nervous system; it does not initiate skeletal muscle contraction at junctions. Option d is incorrect because GABA is the main inhibitory neurotransmitter in the brain, decreasing neuronal firing rather than activating muscle fibers at the neuromuscular junction.

Correct Answer: Skeletal muscle

Skeletal muscle is striated and voluntary and attaches to bones through tendons. Each fiber is multinucleated, and contraction is consciously controlled by motor neurons of the somatic nervous system. Option b is incorrect because smooth muscle is non-striated and involuntary; it is found in walls of hollow organs and is not attached to bones by tendons. Option c is incorrect because cardiac muscle is striated but involuntary; it is found only in the heart and is not connected to bones by tendons. Option d is incorrect because visceral muscle is another term for smooth muscle in organ walls; it is non-striated, involuntary, and not attached to skeletal bones.

Correct Answer: Actin and myosin

During contraction, myosin heads bind to actin filaments and pull them toward the center of the sarcomere. The thin actin filaments slide past the thick myosin filaments, shortening the sarcomere. Option a is incorrect because tubulin forms microtubules of the cytoskeleton, and keratin is structural protein in skin and hair; neither participates in muscle contraction. Option b is incorrect because collagen and elastin are connective tissue fibers that provide strength and stretch in tissues; they do not generate force in sarcomeres. Option c is incorrect because troponin and tropomyosin regulate access to actin binding sites but are not the primary sliding filaments themselves in the sarcomere.

Correct Answer: Calcium

Calcium ions stored in the sarcoplasmic reticulum are released into the cytoplasm when the muscle fiber depolarizes. Calcium binds troponin, exposing actin binding sites so myosin can attach. Option a is incorrect because sodium influx depolarizes the muscle membrane and triggers signaling but does not directly expose actin binding sites for contraction. Option b is incorrect because potassium efflux contributes to repolarization of the membrane after action potentials; it does not unmask actin binding sites. Option d is incorrect because chloride helps stabilize the resting membrane potential; it is not the regulatory ion that unblocks actin during muscle contraction.

Correct Answer: Flexor

A flexor muscle decreases the angle at a joint. The biceps brachii flexes the elbow by pulling the forearm toward the upper arm and shortening the joint angle. Option b is incorrect because an extensor increases the joint angle; the triceps brachii is the elbow extensor, working in opposition to the flexing biceps brachii muscle. Option c is incorrect because an abductor moves a limb away from the midline of the body, such as the deltoid lifting the arm; it does not bend the elbow. Option d is incorrect because a rotator turns a body part around its long axis; flexion of the elbow specifically describes a hinge bending action.

Correct Answer: Sperm production

Spermatogenesis takes place inside the seminiferous tubules of the testes. Damage to these tubules directly impairs sperm production, even when other reproductive organs and hormonal pathways remain functional. Option a is incorrect because testosterone is produced by Leydig cells located between the seminiferous tubules; impaired tubules can spare hormone secretion to a large degree. Option c is incorrect because erection involves vascular and nervous mechanisms in the penis; it is not directly dependent on the function of seminiferous tubules. Option d is incorrect because sperm motility activation is largely produced by prostate gland secretions added during ejaculation, separate from seminiferous tubule function.

Correct Answer: Fallopian tube

After ovulation, the egg enters the fallopian tube. Sperm travel up through the uterus and meet the egg here, so fertilization usually occurs within the fallopian tube. Option a is incorrect because the ovary releases the egg at ovulation but is not where fertilization typically occurs; the egg leaves the ovary before meeting sperm. Option b is incorrect because the uterus is where the fertilized embryo implants and develops; fertilization itself usually happens earlier in the fallopian tube. Option c is incorrect because the vagina serves as the receptive canal for sperm and as the birth canal; sperm pass through but fertilization rarely occurs there.

Correct Answer: Luteinizing hormone

A surge of luteinizing hormone from the anterior pituitary around day fourteen causes the mature follicle to rupture and release its egg, the event known as ovulation. Option a is incorrect because follicle-stimulating hormone develops the ovarian follicle during the early follicular phase but does not itself trigger the ovulation event. Option b is incorrect because estrogen produced by the follicle thickens the endometrium and triggers the luteinizing hormone surge; it does not directly cause ovulation. Option d is incorrect because progesterone is released by the corpus luteum after ovulation has already occurred to maintain the uterine lining for possible pregnancy.

Correct Answer: Uterus

The uterus is a pear-shaped muscular organ. A fertilized egg implants in its endometrial lining, and the uterus stretches and contracts to accommodate and ultimately deliver the fetus. Option b is incorrect because the cervix is the narrow lower opening of the uterus into the vagina; it is not the muscular chamber where the fetus develops. Option c is incorrect because the ovary produces eggs and hormones but does not house or support a developing fetus during pregnancy. Option d is incorrect because the vagina serves as the birth canal and receives the penis; it is not the chamber where fetal development occurs.

Correct Answer: Epidermis

The epidermis is the outermost skin layer and is avascular. New cells form at its base and migrate upward, keratinize, and ultimately slough off from the surface. Option a is incorrect because the hypodermis is the deepest skin-related layer and is mostly fat tissue; it is not the outermost layer with keratinized cells. Option b is incorrect because the subcutaneous layer is another name for the hypodermis, lying below the dermis; it cushions and insulates rather than producing keratin. Option c is incorrect because the dermis lies beneath the epidermis and contains blood vessels, nerves, and glands; it is not the avascular outer keratinizing layer.

Correct Answer: Melanocytes

Melanocytes in the basal epidermis produce melanin, a brown pigment that absorbs ultraviolet radiation. Melanin transferred to surrounding cells helps protect deoxyribonucleic acid from sun damage. Option a is incorrect because keratinocytes produce keratin, the tough protein that gives skin its barrier strength; they do not synthesize the pigment melanin. Option b is incorrect because fibroblasts are connective tissue cells of the dermis that secrete collagen and elastin fibers, not the melanin pigment in the epidermis. Option d is incorrect because Langerhans cells are immune cells in the epidermis that detect pathogens; they do not produce protective skin pigment.

Correct Answer: Vasodilation and active sweating

When body temperature rises, dermal blood vessels dilate to bring warm blood near the surface, and sweat glands secrete fluid that evaporates, cooling the skin and dissipating excess heat. Option a is incorrect because vasoconstriction of dermal vessels conserves heat by limiting blood flow to the surface; this is the response to cold, not overheating. Option c is incorrect because arrector pili contraction raises body hair to trap air against the skin, a heat-conserving response rather than a heat-releasing one. Option d is incorrect because shivering generates heat through rapid skeletal muscle contraction; it warms the body in cold conditions instead of helping cool it down.

Correct Answer: Pituitary gland

The pituitary gland is called the master gland because it releases hormones that regulate the thyroid, adrenal cortex, gonads, and other targets, coordinating the wider endocrine system. Option b is incorrect because the thyroid gland produces hormones regulating metabolism and calcitonin for calcium control, but it is itself controlled by pituitary thyroid-stimulating hormone. Option c is incorrect because the adrenal gland produces cortisol, aldosterone, and epinephrine; its activity is largely regulated by pituitary adrenocorticotropic hormone. Option d is incorrect because the pineal gland secretes melatonin to regulate sleep-wake cycles and does not exert broad control over other endocrine glands.

Correct Answer: Insulin

Insulin from pancreatic beta cells lowers blood glucose by stimulating cells, especially in muscle and liver, to take up glucose and store it as glycogen or use it for energy. Option a is incorrect because glucagon, produced by pancreatic alpha cells, raises blood glucose by stimulating glycogen breakdown; it does not lower glucose levels. Option b is incorrect because cortisol from the adrenal cortex actually increases blood glucose during stress through gluconeogenesis; it does not lower elevated glucose. Option c is incorrect because epinephrine from the adrenal medulla raises blood glucose during fight-or-flight responses; it opposes insulin rather than supporting glucose lowering.

Correct Answer: Antidiuretic hormone

Antidiuretic hormone, released by the posterior pituitary, acts on collecting ducts of the nephron to increase water reabsorption, concentrating urine and conserving body water during dehydration. Option a is incorrect because aldosterone, from the adrenal cortex, promotes sodium reabsorption in the distal tubule; water follows secondarily and it is not pituitary-derived. Option b is incorrect because oxytocin is also stored in the posterior pituitary, but it stimulates uterine contractions and milk ejection, not renal water reabsorption. Option d is incorrect because atrial natriuretic peptide is released by the heart in response to high blood pressure and promotes sodium and water excretion, opposite to retention.

Correct Answer: Parathyroid gland

The four parathyroid glands sit on the back of the thyroid. They secrete parathyroid hormone in response to low blood calcium, raising calcium by releasing it from bone. Option b is incorrect because the pituitary gland controls many endocrine glands but does not produce parathyroid hormone or directly regulate blood calcium concentration. Option c is incorrect because the adrenal medulla releases epinephrine and norepinephrine for fight-or-flight responses; it does not secrete parathyroid hormone. Option d is incorrect because the thymus produces thymosins that mature T-lymphocytes; it has no role in calcium regulation through parathyroid hormone secretion.

Correct Answer: Nephron

The nephron is the functional unit of the kidney. Each nephron filters blood at the glomerulus, then reabsorbs and secretes substances along its tubule to form urine. Option a is incorrect because the renal pelvis collects urine produced by many nephrons before passing it to the ureter; it does not perform filtration itself. Option c is incorrect because the ureter is a transport tube carrying urine from the kidney to the bladder; it does not filter blood or generate urine. Option d is incorrect because the collecting duct receives urine from many nephrons and adjusts water reabsorption; it is part of, but not the entire functional unit.