All Free Biology MCQs with Answers
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19844 questions · page 705 of 1985
7041. Proprioceptive stimuli differ from tactile stimuli in that _.
- A. Tactile neurons are able to differentiate a range of sensations, while proprioceptive neurons are specific to a particular quantity of force
- B. Tactile stimuli are transmitted through the spinal trigeminal pathway, while proprioceptive stimuli are transmitted through the main sensory trigeminal pathway
- C. Tactile stimuli result in a general sensation, while proprioceptive signals the intensity of the sensation
- D. Proprioceptive stimuli are internal and generated by body position and movement, while tactile stimuli are external
Explanation: The only entirely true statement is that proprioceptive stimuli are internal and generated by body position and movement, while tactile stimuli are external. Proprioception is the awareness of the body in space, which allows animals to have the sensation of the placement of their bodies without needing to see what they are doing or feel their way. Tactile perception is the body's interaction with an external stimulus, such as pain, temperature, or pressure. While most tactile stimuli are transmitted through the spinal trigeminal pathway, certain sensations use the main sensory trigeminal pathway.
Correct answer: Proprioceptive stimuli are internal and generated by body position and movement, while tactile stimuli are external7042. The basal cells of the gustatory system _.
- A. Serve as structural support for neuro-epithelial cells
- B. Contain synaptic structures that transport sensory information
- C. Are dependent on ion channels to produce action potentials
- D. Will eventually differentiate into taste receptor cells
Explanation: Taste buds are bulb-shaped and open to the environment through a small pore. Chemical compounds bind to small cellular hairs of taste receptor cells to stimulate an action potential, relaying the taste to the brain. Basal cells are located at the bottom of the taste bud. As taste receptors die, basal cells will differentiate into new receptors to maintain the taste bud.
Correct answer: Will eventually differentiate into taste receptor cells7043. A person who has over-functioning pancreatic alpha cells may display what clinical feature?
- A. Decreased glucose levels
- B. Increased digestion
- C. Constipation
- D. Elevated glucose levels
Explanation: The pancreatic alpha cells produce the hormone glucagon, which is responsible for stimulating gluconeogenesis and glycogenolysis. Gluconeogenesis is the formation of glucose, while glycogenolysis is the breakdown of glycogen into glucose. An increase in glucagon production through hyperactive alpha cells will result in increased blood glucose levels, at least temporarily. In a healthy individual, this will be combated by an increase in insulin production from the pancreatic beta cell.
Correct answer: Elevated glucose levels7044. Which hormone is responsible for stimulating glucocorticoid release from the adrenal cortex?
- A. Prolactin
- B. Adrenocorticotropic hormone
- C. Growth hormone
- D. Thyroid-stimulating hormone
Explanation: Adrenocorticotropic hormone (ACTH) is released from the anterior pituitary, and is responsible for stimulating secretion of glucocorticoids from the adrenal cortex. While cortisol is the most common and physiologically relevant glucocorticoid, others may also be synthesised. Adrenocorticotropic hormone release is stimulated by stress.
Correct answer: Adrenocorticotropic hormone7045. The hypothalamus uses two specialised types of neuron to stimulate the pituitary. Magnocellular neurons carry hormones directly to the posterior pituitary. Parvocellular neurons secrete hormones into the hypophyseal portal system, where they are delivered to the anterior pituitary.The magnocellular neurons of the hypothalamus are responsible for secreting which hormone?
- A. Thyrotropin-releasing hormone (TRH)
- B. Dopamine
- C. Oxytocin
- D. Thyroid-stimulating hormone (TSH)
Explanation: The hypothalamus is divided up into two parts: the magnocellular neurons and the parvocellular neurons. The magnocellular neurons synthesise antidiuretic hormone (ADH) and oxytocin, which are then transported to the posterior pituitary for secretion. The parvocellular neurons secrete hormones such as corticotropin-releasing hormone (CRH).
Correct answer: Oxytocin7046. Which of the following statements concerning hormonal transport is true?
- A. The thyroid hormones are able to move freely in the bloodstream
- B. Pancreatic hormones are able to move freely through the bloodstream
- C. All hormones require chylomicrons in order to move through the bloodstream
- D. Steroid hormones are able to move freely through the bloodstream
Explanation: The correct answer is B) Pancreatic hormones are able to move freely through the bloodstream, specifically referring to Insulin and Glucagon, which are water-soluble (peptide) hormones that do not require carrier proteins to be transported through the water-based blood plasma. Options A and D are wrong because thyroid hormones and steroid hormones are lipid-soluble and are mostly (over 99% for thyroid hormones) bound to transport proteins like globulins and albumin in the blood, with only a small "free" fraction being biologically active. Option C is also wrong, as chylomicrons primarily transport dietary lipids like triglycerides, not all hormones.
Correct answer: Pancreatic hormones are able to move freely through the bloodstream7047. Type II diabetes results from prolonged overstimulation of the pancreatic beta cells as a result of obesity and chronically elevated glucose levels. After the beta cells have been overactive for an extended period of time, they begin functioning poorly and the person is considered diabetic. In a type II diabetes, what are the expected levels of insulin and glucagon with respect to normal values?
- A. Insulin levels will be elevated and glucagon levels will be low
- B. Insulin levels will be low and glucagon levels will be low
- C. Insulin levels will be elevated and glucagon levels will be elevated
- D. Insulin levels will be low and glucagon levels will be elevated
Explanation: Type II diabetes results from an eventual lack of function of the pancreatic beta cells. The first step to this problem is remembering that the beta cells produce insulin. If the beta cells do not function, insulin levels will be decreased. The second step to this problem is remembering that insulin and glucagon have contrasting actions in the regulation of blood glucose levels. They act in a negative feedback loop: insulin inhibits glucagon release, and glucagon inhibits insulin release. If insulin levels are low, then glucagon will no longer be inhibited. As a result, we would observe low levels of insulin and elevated levels of glucagon.
Correct answer: Insulin levels will be low and glucagon levels will be elevated7048. Which of the following is NOT a direct effect of the anterior pituitary?
- A. Milk production
- B. Ovulation
- C. T4 production
- D. Water retention
Explanation: Milk production is influenced by prolactin (produced in the anterior pituitary). Bone growth is influenced by growth hormone (produced in the anterior pituitary). Ovulation is controlled by luteinizing hormone and follicle-stimulating hormone (both produced in the anterior pituitary). T4, a thyroid hormone, is controlled by thyroid-stimulating hormone (produced in the anterior pituitary). Water retention, on the other hand, is controlled by antidiuretic hormone (produced in the hypothalamus and released by the posterior pituitary).
Correct answer: Water retention7049. Scientists use a process called Fluorescent In-Situ Hybridization, or FISH, to study genetic disorders in humans. FISH is a technique that uses spectrographic analysis to determine the presence or absence, as well as the relative abundance, of genetic material in human cells. To use FISH, scientists apply fluorescently-labeled bits of DNA of a known colour, called probes, to samples of test DNA. These probes anneal to the sample DNA, and scientists can read the colours that result using laboratory equipment. One common use of FISH is to determine the presence of extra DNA in conditions of aneuploidy, a state in which a human cell has an abnormal number of chromosomes. Chromosomes are collections of DNA, the totality of which makes up a cell's genome. Another typical use is in the study of cancer cells, where scientists use FISH labels to ascertain if genes have moved inappropriately in a cell's genome. Using red fluorescent tags, scientists label probe DNA for a gene known to be expressed more heavily in cancer cells than normal cells. They then label a probe for an immediately adjacent DNA sequence with a green fluorescent tag. Both probes are then added to three dishes, shown below. In dish 1 human bladder cells are incubated with the probes, in dish 2 human epithelial cells are incubated, and in dish 3 known non-cancerous cells are used. The relative luminescence observed in regions of interest in all dishes is shown below.Aneuploidy can also affect some fertilized zygotes after abnormalities in fertilization or gametogenesis. Aneuploid zygotes are typically spontaneously aborted before a pregnancy comes to term. A normal zygote binds to uterine endometrium while it is at its thickest, supported by progesterone secretion from which of the following?
- A. Graafian follicle
- B. Hypothalamus
- C. Posterior pituitary
- D. Corpus luteum
Explanation: The corpus luteum forms after ovulation, when a pregnancy would be most expected. The corpus luteum secretes progesterone, which maintains the endometrium for potential implantation.
Correct answer: Corpus luteum7050. Glucose levels in the blood are maintained through the competing actions of two main hormones: insulin and glucagon. Other hormones, such as somatostatin, and catecholamines, such as acetylcholine, also serve to modulate glucose levels in the blood. Which molecule is produced by the alpha cells of the islets of Langerhans in the pancreas.
- A. Insulin
- B. Somatostatin
- C. Glucagon
- D. Acetylcholine
Explanation: Alpha cells in the islets of Langerhans are responsible for producing and secreting glucagon in response to high blood glucose levels. Insulin antagonises the alpha cells to prevent glucagon release. In diabetes, when the beta cells of the pancreas are not functional, extremely high levels of glucagon exist in the blood due to loss of the negative feedback loop. Beta and delta cells in the islets of Langerhans produce insulin and somatostatin, respectively. Neurons release acetylcholine to modulate glucose control through indirect processes.
Correct answer: Glucagon