42. The change in the concentration of _______ is the major factor that affects the breathing control centers.
(A)hemoglobin
(B) hydrogen ions
(C) bicarbonate ions
(D)carbon dioxide
(E)oxygen

38. Which one of the following hormones are not derived from cholesterol? (A)Testosterone. (B) Melatonin. (C) Cortisol. (D)Estradiol. (E)Aldosterone.

39. ________ is a water-soluble hormone derived from the nervous system that regulates blood volume and blood pressure? (A)Cortisol (B) Oxytocin (C) Aldosterone (D)Antidiuretic hormone (E)Adrenocorticotropic hormone

40. Which of the following correctly describes the path of urine from formation to excretion in the mammalian kidney? (A)collecting duct → ureter →  urinary bladder →  renal pelvis→  urethra (B) renal pelvis →  ureter →  urinary bladder →  urethra→ collecting duct (C) ureter →  collecting duct →  renal pelvis → urinary bladder → urethra (D)collecting duct→  renal pelvis→  ureter → urinary bladder →  urethra (E)urethra→ collecting duct→  renal pelvis → ureter →  urinary bladder

41. The major respiratory centers that control ventilation of the lungs in mammals are located in the______. (A)neck (B) hypothalamus (C) bronchi (D)cerebral cortex (E)brainstem

43. In vertebrates with four-chambered hearts, the ____ receives oxygenated blood directly from the _____. (A)left atrium, left ventricle (B) left ventricle, lungs (C) left ventricle, left atrium (D)right ventricle, lungs (E)right ventricle, right atrium

44. The most possible chemical compound for increasing cardiac output when animals are exercising is ___. (A)epinephrine (B) serotonin (C) dopamine (D)glutamate (E)acetylcholine

45. The stomach is majorly surrounded by which type of muscle? (A)Skeletal muscle. (B) Smooth muscle. (C) Cardiac muscle. (D)Voluntary muscle. (E)Striated muscle.

46. The _______ protein might contains an ATP binding site for further activation. (A)tropomyosin (B) troponin (C) myosin (D)actin (E)All of the choices are correct

47. The perception of a certain pitch of sound is possibly depends on which of the following? (A)Whether it is the round window or oval window that vibrates. (B) Which bones of the middle ear are moved. (C) The amplitude of the sound waves. (D)Where particles settle in the semicircular canals. (E)Which hair cells of the cochlea are stimulated.

48. The tough outer covering of the eye is mainly referred to as the ____. (A)sclera (B) retina (C) pupil (D)iris (E)fovea