NEET Biology Human Physiology and Animal Kingdom MCQs Set 03

Answer: (d) Peyer's patch

Explanation:
1. Parotid (salivary), pancreas and liver secrete digestive juices or bile.
2. Peyer's patches are lymphoid tissues in the ileum that take part in immunity and do not secrete digestive enzymes.

Teacher's Note:
1. Peyer's patches are part of the gut-associated lymphoid tissue.
2. Gastric and intestinal glands are also digestive glands.

Answer: (d) jaundice

Explanation:
1. If bile flow is blocked, bilirubin cannot be excreted into the intestine and accumulates in the blood.
2. This gives yellowing of the skin and eyes, called jaundice.

Teacher's Note:
1. Obstructive jaundice also gives pale stools since bile pigments do not reach the gut.
2. Uremia is the accumulation of urea in blood.

Answer: (a) Stimulus \(\rightarrow\) Sensory \(\rightarrow\) Motor \(\rightarrow\) Response

Explanation:
1. A stimulus is detected by a receptor, which sends an impulse along the sensory (afferent) neuron to the spinal cord.
2. The impulse passes through the motor (efferent) neuron to the effector, giving the response.
3. Hence stimulus, sensory, motor, response.

Teacher's Note:
1. The reflex arc bypasses the brain for speed.
2. The knee jerk is a simple two-neuron reflex.

Answer: (b) A is found in the cerebrum and cerebellum, and B in the spinal cord

Explanation:
1. In the cerebrum and cerebellum the cortex is made of gray matter (cell bodies) on the outside, with white matter (nerve fibres) in the middle.
2. In the spinal cord the arrangement is reversed, with the white matter outside and a butterfly-shaped core of gray matter inside.

Teacher's Note:
1. Gray matter = neuron cell bodies, white matter = myelinated axons.
2. The brain has gray matter outside, the spinal cord has it inside.

Answer: (a) squamous epithelium

Explanation:
1. Alveolar walls are made of a single layer of thin, flat squamous epithelial cells.
2. This gives a short diffusion distance for gas exchange.

Teacher's Note:
1. Squamous epithelium is also found in blood vessel walls (endothelium).
2. Cuboidal epithelium lines the kidney tubules and glands.

Answer: (b) incomplete metamorphosis

Explanation:
1. The nymph resembles the adult and grows through moulting, becoming an adult after about 13 moults.
2. This is paurometabolous or incomplete metamorphosis, without pupal stage.

Teacher's Note:
1. Nymphs of cockroaches lack wings and genitalia.
2. Butterflies and houseflies show complete metamorphosis.

Answer: (d) Aschelminthes

Explanation:
1. Aschelminthes (roundworms) have a body cavity that is not completely lined by mesoderm, so they are pseudocoelomates.
2. Chordata, Hemichordata and Annelida have a true coelom.

Teacher's Note:
1. Platyhelminthes are acoelomates.
2. The pseudocoelom lies between the ectoderm and endoderm with mesoderm only in scattered patches.

Answer: (b) Cephalochordata

Explanation:
1. In Urochordata the notochord is present only in the larval tail.
2. In Cephalochordata (for example Branchiostoma) the notochord extends from head to tail and stays throughout life.

Teacher's Note:
1. Cephalochordata means "head notochord".
2. In vertebrates the notochord is replaced by the vertebral column.

Answer: (c) both right and left

Explanation:
1. In reptiles the heart is typically three chambered (crocodiles have four) and the ventricle gives rise to both right and left systemic aortic arches.
2. Birds have only the right and mammals only the left systemic arch.

Teacher's Note:
1. Remember: Mammals have the left aortic arch; birds have the right.
2. Reptiles keep both arches.

Answer: (a) Earthworm: pharyngeal, integumentary and septal nephridia

Explanation:
1. The earthworm has three types of nephridia: septal, pharyngeal and integumentary.
2. In the cockroach the excretory organs are the Malpighian tubules (the enteric caeca are digestive). The frog excretes through kidneys, and humans through kidneys, skin and lungs, with sebaceous glands and tears playing a very small role.

Teacher's Note:
1. Earthworm nephridia are of three types by position.
2. Malpighian tubules are the excretory organs of insects.

Answer: (a) pulmonary vein

Explanation:
1. The pulmonary vein brings oxygenated blood from the lungs to the left atrium.
2. The other veins carry deoxygenated blood.

Teacher's Note:
1. Pulmonary arteries are the only arteries carrying deoxygenated blood.
2. Veins are defined by the direction of flow towards the heart.

Answer: (b) The cardiac muscles will not contract in a coordinated, rhythmic manner

Explanation:
1. The SA node initiates the impulse that spreads to the whole heart.
2. Without it the heart loses its coordinated rhythm, and a slower, uncoordinated activity from other parts may occur.
3. That is why an artificial pacemaker is implanted.

Teacher's Note:
1. SA node is the natural pacemaker and is located in the right atrium.
2. Its normal rate is about 70-75 beats per minute.

Answer: (d) Expulsion of air from the lungs

Explanation:
1. Contraction of the external intercostal muscles lifts the ribs and sternum, increasing the thoracic volume in the dorso-ventral axis.
2. The lung volume rises and the intrapulmonary pressure falls below atmospheric pressure, so air is drawn in (inspiration).
3. Expulsion of air is expiration, which occurs when these muscles relax.

Teacher's Note:
1. Inspiration is active, expiration is passive in normal breathing.
2. The diaphragm contracts together with the external intercostals.

Answer: (c) less \(\mathrm{CO_2}\) in blood

Explanation:
1. Deep breathing washes out \(\mathrm{CO_2}\) from blood, lowering its pCO\(_2\).
2. The respiratory centre in the medulla is mainly stimulated by \(\mathrm{CO_2}\) (through H\(^+\)), so with less \(\mathrm{CO_2}\) the urge to breathe is lost for a while.

Teacher's Note:
1. The respiratory rhythm centre is sensitive to \(\mathrm{CO_2}\) and \(\mathrm{H^+}\), not much to \(\mathrm{O_2}\).
2. Hyperventilation can cause temporary apnoea.

Answer: (a) PCT

Explanation:
1. About 65-70 percent of the filtrate (nearly 99 percent of the filtrate is reabsorbed in the whole nephron) is reabsorbed in the PCT.
2. The loop of Henle and DCT reabsorb smaller amounts.
3. So among the choices the PCT shows maximum reabsorption of water in the nephron.

Teacher's Note:
1. The PCT has a brush border to increase surface area.
2. The collecting duct reabsorbs water under ADH control.

Answer: (b) hepatic vein

Explanation:
1. Urea is formed in the liver from ammonia by the ornithine cycle.
2. The blood leaving the liver through the hepatic vein is therefore the richest in urea.

Teacher's Note:
1. Urea is later filtered in the kidney, so renal vein has less urea than renal artery.
2. The hepatic portal vein brings digested food, not urea.

Answer: (d) all of the above

Explanation:
1. Smooth muscle cells are spindle shaped with tapering ends, unbranched, uninucleate and involuntary.
2. They have no striations, and they are found in the walls of hollow organs.

Teacher's Note:
1. Cardiac muscle is striated and branched.
2. Skeletal muscle is multinucleate and voluntary.

Answer: (d) posterior pituitary

Explanation:
1. The posterior pituitary (neurohypophysis) stores and releases oxytocin and vasopressin, which are made by hypothalamic neurons and carried down their axons, so it is under direct neural control.
2. The anterior pituitary is regulated by releasing and inhibiting hormones through the portal system, and the thyroid and adrenal cortex are controlled by hormones.

Teacher's Note:
1. Posterior pituitary hormones are made in the hypothalamus.
2. The hypothalamus controls the anterior pituitary through hypophysial portal blood vessels, not nerves.

Answer: (b) Two

Explanation:
1. (a) is false, since cretinism is caused by hypothyroidism in childhood (dwarfism from GH deficiency is different).
2. (b) is false, since thyrocalcitonin is secreted by the thyroid.
3. (c) is true, as PTH raises blood calcium.
4. (d) is true, since renin leads to angiotensin II formation, which stimulates the release of aldosterone.
5. Two statements, (c) and (d), are true.

Teacher's Note:
1. Calcitonin lowers blood calcium and PTH raises it.
2. Renin is secreted by the juxtaglomerular cells.