MDS PREP
In the presence of which substance does vitamin B12 combine in the stomach to prevent its degradation by gastric acid?
1) Intrinsic factor
2) Pepsin
3) Gastric acid
4) Pancreatic amylase
Physiology
Answer: 1
Vitamin B12 combines with intrinsic factor to form a complex that is protected from degradation by gastric acid.
Which hormone is primarily responsible for increasing the force and frequency of uterine contractions during parturition?
1) Oxytocin
2) Estrogen
3) Progesterone
4) Prolactin
E. Cortisol
Oxytocin is synthesized in the paraventricular nucleus of the hypothalamus and acts on the uterus to increase the force and frequency of contractions during childbirth. It is released during labor and stimulated by the stretching of the cervix and vagina as the baby descends. Estrogens increase the sensitivity of the uterus to oxytocin, while progesterone decreases it. Prolactin is involved in milk production and let-down reflex. Cortisol is a stress hormone that prepares the body for parturition but does not directly increase uterine contractions.
What is the function of the thick ascending limb of the loop of Henle?
1) Reabsorption of water
2) Secretion of hydrogen ions
3) Reabsorption of sodium, chloride, and bicarbonate
4) Reabsorption of urea
The thick ascending limb of the loop of Henle is responsible for the reabsorption of sodium, chloride, and bicarbonate, contributing to urine concentration.
What type of aphasia is associated with lesions in the temporal lobe's auditory association area?
1) Broca's aphasia
2) Wernicke's aphasia
3) Global aphasia
4) Sensory aphasia
Wernicke's aphasia is associated with lesions in the temporal lobe's auditory association area, particularly Brodmann's area 22. It is characterized by fluent speech with impaired comprehension and repetition.
What is the function of calcidiol in the body?
1) It is the active form of vitamin D
2) It is the precursor to calcitriol (active vitamin D)
3) It has no known function
4) It inhibits calcium absorption
Physiology
Answer: 2
Calcidiol (25 hydroxy cholecalciferol) is a precursor to calcitriol (1,25 dihydroxy vitamin D3), which is the active form of vitamin D. Calcitriol is formed in the kidneys by the action of 1-? hydroxylase and plays a critical role in calcium homeostasis.
What is the primary function of the epididymis in the male reproductive system?
1) Storage and maturation of sperm
2) Secretion of androgens
3) Formation of the spermatozoa
4) Fusion of gametes during fertilization
The primary function of the epididymis in the male reproductive system is the storage and maturation of sperm, allowing them to gain motility and the ability to fertilize an egg.
What is the primary function of type A? fibers?
1) Proprioception and motor function in muscle spindles
2) Pain and temperature sensation
3) Touch and pressure sensation
4) Autonomic regulation of smooth muscles
Type A? fibers are thinly myelinated and conduct pain and temperature signals rapidly. They are involved in the transmission of the initial sharp pain sensation, often in response to noxious stimuli such as pinpricks or intense heat.
Which of the following is the correct statement regarding mammalian nerve fibers?
1) A-alpha fibers have the lowest conduction velocity and are responsible for pain and temperature sensation.
2) A-beta fibers have the highest conduction velocity and are responsible for motor supply to skeletal muscles.
3) A-gamma fibers are heavily myelinated and have the fastest conduction velocity.
4) C fibers have a large diameter and are responsible for fine motor control.
Answer: 2) A-beta fibers have the second highest conduction velocity after A-alpha fibers and are responsible for touch, kinesthetic sense, and pressure sensation, not motor supply to skeletal muscles. A-alpha fibers have the highest conduction velocity and are indeed responsible for motor supply to skeletal muscles.