BS Nursing Entry Test Biology Syllabus

What is crossing over and in which phase of meiosis does it occur?

Crossing over is the exchange of genetic material between homologous chromosomes, increasing genetic variation. It occurs during Prophase I of meiosis at the chiasmata.

What is the role of the enzyme amylase (ptyalin) in digestion?

Salivary amylase, secreted in the mouth, begins the digestion of starch into maltose (a disaccharide).

Where is bile produced and stored, and what is its function in digestion?

Bile is produced by the liver and stored in the gallbladder. It emulsifies fats (breaks large fat globules into smaller droplets) to increase surface area for lipase action.

Where does most absorption of digested nutrients occur and what structures aid it?

In the small intestine, mainly the ileum. Finger-like villi and microvilli greatly increase surface area; each villus contains capillaries and a lacteal for absorption.

What are the components of gastric juice and their roles?

Hydrochloric acid (kills microbes, activates enzymes, provides acidic pH), pepsin/pepsinogen (digests proteins), and mucus (protects the stomach lining).

Trace the path of blood through the four chambers of the human heart.

Deoxygenated blood enters the right atrium, flows to the right ventricle, then to the lungs; oxygenated blood returns to the left atrium, passes to the left ventricle, and is pumped to the body via the aorta.

What is the difference between arteries, veins, and capillaries?

Arteries carry blood away from the heart (thick, muscular walls, high pressure); veins carry blood toward the heart (thinner walls, valves to prevent backflow); capillaries are one-cell-thick vessels for exchange of materials.

What is the function of the SA node (sinoatrial node) in the heart?

The SA node is the heart's natural pacemaker; it initiates the electrical impulse that triggers each heartbeat, setting the rhythm of contraction.

Differentiate systemic circulation from pulmonary circulation.

Pulmonary circulation carries blood between the heart and lungs (for gas exchange). Systemic circulation carries oxygenated blood from the heart to the rest of the body and returns deoxygenated blood.

What is the role of hemoglobin and where is it found?

Hemoglobin is an iron-containing protein in red blood cells (erythrocytes) that binds and transports oxygen (as oxyhemoglobin) and some carbon dioxide.

Describe the pathway of air during inhalation.

Air passes through the nostrils, pharynx, larynx, trachea, bronchi, bronchioles, and finally the alveoli, where gas exchange occurs.

Where does gas exchange occur in the lungs and why are alveoli suited for it?

Gas exchange occurs in the alveoli. They are thin-walled, moist, numerous (large surface area), and surrounded by capillaries, allowing efficient diffusion of O2 and CO2.

What is the role of the diaphragm in breathing?

During inhalation the diaphragm contracts and flattens, increasing thoracic volume and drawing air in. During exhalation it relaxes and domes upward, pushing air out.

What is the functional unit of the kidney and what does it do?

The nephron is the functional unit of the kidney; it filters blood and forms urine through filtration, reabsorption, and secretion.

Name the three main processes of urine formation in the nephron.

Ultrafiltration (in the glomerulus/Bowman's capsule), selective reabsorption (in the tubules), and tubular secretion. The remaining filtrate becomes urine.

What is the main nitrogenous waste excreted by humans and where is it formed?

Urea is the main nitrogenous waste. It is formed in the liver from the breakdown (deamination) of excess amino acids and excreted by the kidneys.

What are the structural and functional units of the nervous system?

The neuron (nerve cell) is the structural and functional unit. It consists of a cell body, dendrites (receive signals), and an axon (transmits signals).

Differentiate the central nervous system (CNS) from the peripheral nervous system (PNS).

The CNS consists of the brain and spinal cord (integration and control). The PNS consists of nerves connecting the CNS to the rest of the body, including sensory and motor neurons.

What is a reflex arc and what is its significance?

A reflex arc is the neural pathway of a reflex action: receptor, sensory neuron, interneuron (in spinal cord), motor neuron, and effector. It allows rapid, involuntary responses to protect the body.

What is a synapse and how is a nerve impulse transmitted across it?

A synapse is the junction between two neurons. The impulse is transmitted chemically by neurotransmitters (e.g., acetylcholine) released from the presynaptic neuron, which diffuse across the gap and bind receptors on the next neuron.

What is the difference between the sympathetic and parasympathetic nervous systems?

The sympathetic system prepares the body for 'fight or flight' (increases heart rate, dilates pupils). The parasympathetic system promotes 'rest and digest' (slows heart rate, stimulates digestion).

How do the endocrine and nervous systems differ in communication?

The nervous system uses electrical impulses and neurotransmitters for fast, short-lived, localized responses. The endocrine system uses hormones via the blood for slower, longer-lasting, widespread effects.

Which hormone lowers blood glucose, which raises it, and where are they produced?

Insulin lowers blood glucose and glucagon raises it; both are produced by the islets of Langerhans in the pancreas (beta cells make insulin, alpha cells make glucagon).

Why is the pituitary gland called the 'master gland'?

Because it secretes hormones that control many other endocrine glands (e.g., thyroid, adrenals, gonads) through hormones like TSH, ACTH, FSH, and LH.

Which hormone is secreted by the thyroid gland and what is its main function?

Thyroxine (T4) and triiodothyronine (T3), which contain iodine and regulate the body's metabolic rate, growth, and development.

What are the main functions of the human skeletal system?

Support and shape, protection of organs, movement (with muscles via joints and levers), blood cell production (in red bone marrow), and storage of minerals like calcium and phosphorus.

What is the difference between the axial and appendicular skeleton?

The axial skeleton includes the skull, vertebral column, ribs, and sternum (central axis). The appendicular skeleton includes the limbs and the girdles (pectoral and pelvic) that attach them.

What causes osteoporosis and how does it differ from rickets?

Osteoporosis is loss of bone mass/density making bones brittle (common with aging and calcium/estrogen deficiency). Rickets is softening/deformity of bones in children due to vitamin D, calcium, or phosphate deficiency (osteomalacia in adults).

What are the three types of muscle tissue and an example of each?

Skeletal (voluntary, striated; attached to bones), cardiac (involuntary, striated; in the heart), and smooth (involuntary, non-striated; in walls of internal organs like the gut).

What are the male reproductive structures that produce sperm and testosterone?

The testes produce sperm (in the seminiferous tubules) and secrete the hormone testosterone (from the interstitial cells of Leydig).

What is gametogenesis, and what are its two types?

Gametogenesis is the formation of gametes by meiosis. The two types are spermatogenesis (sperm formation in the testes) and oogenesis (egg formation in the ovaries).

What is fertilization, and where does it normally occur in humans?

Fertilization is the fusion of a sperm and an egg (ovum) to form a diploid zygote. In humans it normally occurs in the ampulla of the fallopian tube (oviduct).

What are the four phases of the menstrual cycle and which hormones dominate?

Menstrual phase (shedding of the endometrium), follicular phase (FSH stimulates follicle growth, estrogen rises), ovulation (LH surge releases the egg around day 14), and luteal phase (corpus luteum secretes progesterone to maintain the endometrium).