MCAT Biology › Hormone Origins and Targets
A male gymnast is suspected for using anabolic steroids (i.e. testosterone) to enhance in his athletic performance. Which of the following would you expect to be decreased in his blood?
Luteinizing hormone, follicle-stimulating hormone, and gonadotropin-releasing hormone
Luteinizing hormone and follicle-stimulating hormone
Luteinizing hormone only
Gonadotropin-releasing hormone only
Gonadotropin-releasing hormone and luteinizing hormone
All three hormones—luteinizing hormone, follicle-stimulating hormone, and gonadotropin-releasing hormone—are part of the hypothalamic-pituitary-gonadal axis. One should be familiar with this axis and with the fact that testosterone exerts negative control at both the level of the hypothalamus and the anterior pituitary.
Both the sympathetic and the parasympathetic nervous systems are essential for homeostasis and for survival. For example, when we are trying to run away from a threat, the sympathetic nervous system is in full effect to allow us to escape from danger. However, when there is no obvious threat, the parasympathetic nervous system tends to be more in control.
There are similarities and differences between the sympathetic and the parasympathetic nervous systems. In preganglionic nerve fibers, both the sympathetic and the parasympathetic nervous system utilize the neurotransmitter acetylcholine. Closer to the target organ, the parasympathetic nervous system remains dependent on acetylcholine whereas norepinephrine and epinephrine are the predominant neurotransmitters utilized by the sympathetic nervous system.
When norepinephrine and epinephrine bind to their receptors, different effects are carried out based on the type of receptor, affinity, and location of the receptor. For example, epinephrine has a higher affinity for the beta-2 receptor. When epinephrine binds to the beta-2 receptor, common effects include vasodilation and bronchodilation. Norepinephrine has a stronger affinity for the alpha-1, alpha-2 and beta-1 receptors. When norepinephrine binds to its receptor, common effects on the body include vasoconstriction (alpha-1), increased heart rate (beta-1) and uterine contraction (alpha-1).
Patient A has a genetic disorder which prevents him from producing sufficient amount of catecholamines. Which of the following events will be affected in this patient.
I. Digestion
II. Pupil dilation
III. Erection
II only
I only
I and II
III only
II and III
Catecholamines consist of epinephrine and norepinephrine. Without these neurotransmitter, the nervous system cannot illicit a sympathetic response. Of the answer choices, only pupil dilation is an event mediated by the sympathetic nervous system.
Which hormone is responsible for stimulating glucocorticoid release from the adrenal cortex?
Adrenocorticotropic hormone
Prolactin
Growth hormone
Thyroid-stimulating hormone
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 synthesized. Adrenocorticotropic hormone release is stimulated by stress.
Which of the following answer choices contains only hormones secreted by the anterior pituitary gland?
FSH and ACTH
TSH and Estrogen
ADH and ACTH
LH and Oxytocin
Oxytocin and ADH
The correct answer choice is the one containing FSH and ACTH. FSH, or Follicle-stimulating hormone, and ACTH, or Adrenocorticotropic hormone, are each secreted by the anterior pituitary gland. The anterior pituitary hormones can be remembered by the mnemonic, FLATPEG (FSH, LH, ACTH, TSH, Prolactin, Endorphins, Growth Hormone).
Each of the other answer choices contains no more than one anterior pituitary hormone, along with either Estrogen (secreted by the ovaries), Oxytocin (secreted by the posterior pituitary), or ADH/Vasopressin (secereted by the posterior pituitary).
Which of the following hormones secreted by the pituitary directly acts on the adrenal cortex as its target?
ACTH
TSH
ADH
FSH
LH
The only hormone listed that directly stimulates that adrenal cortex is ACTH, which stands for Adrenocorticotropic Hormone. This anterior pituitary-secreted hormone stimulates the adrenal cortex to release cortisol.
The other hormones listed are also secreted by the pituitary gland, but do not act on the adrenal cortex directly.
Which of the following is NOT one of the tropic hormones released by the anterior pituitary?
Prolactin
LH
ACTH
TSH
FSH
Prolactin is an example of a non-tropic hormone released by the anterior pituitary.
The brain is a very delicate structure with little room to move around. Surrounding the brain and the spinal cord are three protective layers in addition to the skull and the vertebral column. Directly surrounding the brain and spinal cord is the pia mater. Following the pia mater is the arachnoid mater. Between the pia mater and the arachnoid mater is the sub-arachnoid space where the cerebrospinal fluid circulates. Finally, the protective layer is the dura mater is loosely attached to the arachnoid mater but is strongly associated with the skull bone.
Depending on the type of injury, a certain type of vein and/or artery are more susceptible to injury. For example, the meningeal artery and vein run through the foramen spinosum and travel between the two layers making up the dura mater. As the artery and the vein are traveling in between the dura mater, there is a vulnerable region at the temple. A strike to the temple region could rupture these vessels and result in a epidural hematoma.
Traveling from the cerebral cortex to the venous dural sinus (located at certain regions between the two layers of the dura mater) is the cerebral vein. When an injury results in the dura mater shifting away from the arachnoid mater, the cerebral vein could rupture and lead to a subdural hematoma.
During a hematoma, the intercranial pressure could increase and push on certain regions of the brain. The compression of a certain region could either excite or inhibit the area. If patient A's laboratory results showed an increase blood concentration of antidiuretic hormone, which region of the brain is being compressed?
Posterior pituitary
Anterior pituitary
Optic chiasm
Cerebral cortex
Adrenal gland
Antidiuretic hormone is produced by the hypothalamus and is released by the posterior pituitary. Therefore, compression either of these structures could provoke the release of antidiuretic hormone.
The brain is a very delicate structure with little room to move around. Surrounding the brain and the spinal cord are three protective layers in addition to the skull and the vertebral column. Directly surrounding the brain and spinal cord is the pia mater. Following the pia mater is the arachnoid mater. Between the pia mater and the arachnoid mater is the sub-arachnoid space where the cerebrospinal fluid circulates. Finally, the protective layer is the dura mater is loosely attached to the arachnoid mater but is strongly associated with the skull bone.
Depending on the type of injury, a certain type of vein and/or artery are more susceptible to injury. For example, the meningeal artery and vein run through the foramen spinosum and travel between the two layers making up the dura mater. As the artery and the vein are traveling in between the dura mater, there is a vulnerable region at the temple. A strike to the temple region could rupture these vessels and result in a epidural hematoma.
Traveling from the cerebral cortex to the venous dural sinus (located at certain regions between the two layers of the dura mater) is the cerebral vein. When an injury results in the dura mater shifting away from the arachnoid mater, the cerebral vein could rupture and lead to a subdural hematoma.
During a hematoma, the intercranial pressure could increase and push on certain regions of the brain. The compression of a certain region could either excite or inhibit the area. If patient A's laboratory results showed an increase blood concentration of antidiuretic hormone, which region(s) of the brain could be compressed?
I. Posterior pituitary
II. Anterior pituitary
III. Hypothalamus
I and III
I only
III only
III only
II and III
Antidiuretic hormone is produced by the hypothalamus and is released by the posterior pituitary. Therefore, compression either of these structures could result in increased blood concentrations of antidiuretic hormone.
There are a large variety of over-the-counter pregnancy tests, although all of them share a set of common principles.
These home pregnancy tests are immunoassays which detect the presence of the peptide hormone human chorionic gonadotropin (hCG). hCG is produced by the fertilized ovum and released into the mother's bloodstream, preventing the degradation of the corpus luteum and thereby preventing menstruation. By the time of the mother's first missed period, hCG levels in the urine are high enough to detect.
The home pregnancy test generally involves dipping a stick containing immobilized hCG monoclonal antibodies into a urine sample. If hCG is present in the urine, it will bind to the monoclonal antibodies on the dipstick. The dipstick is then placed in a solution containing a second monoclonal antibody which recognizes the bound hCG antibody complex on the surface of the dipstick. This second antibody is conjugated to colloidal gold particles which change color when they are immobilized, indicating a positive test result (i.e., pregnancy).
As described in the passage, the home pregnancy test __________.
lacks positive and negative controls
is only effective after at least one month of pregnancy
is inaccurate because hCG can be produced normally in the non-pregnant mother
is inaccurate because hCG is sometimes not produced by the fertilized zygote
accuracy improves when administered during early morning hours
The test, as described in the passage, simply assays for the presence of hCG in the urine. The person using the test would either obtain a positive or negative result. Whether or not this result is valid remains in question because there are no experimental controls involved. In other words, there is nothing to test whether the test reagents are faulty or the procedure was done incorrectly. A positive control would involve using a sample liquid containing hCG and testing to see whether the pregnancy test could actually detect it. If it can't, then something is wrong. A negative control might involve using a urine sample with no hCG in it and seeing if the test gives a false positive result. Such controls are not included in the test as described in the passage. The other answer choices can be eliminated. The answer: 'is only effective after at least one month of pregnancy' is wrong because the passage states that hCG levels are high enough to be detected by the time of the first missed period (anywhere from 7-14 days from the time of fertilization.)
The answer: 'is inaccurate because hCG can be produced normally in the non-pregnant mother,' can be eliminated because the mother does not produce hCG. If she did, the test would be entirely useless. Only the embryo produces the hormone. The answer choice, 'is inaccurate because hCG is sometimes not produced by the fertilized zygote,' is also incorrect because the embryo must produce hCG in order to prevent menstruation and maintain the corpus luteum. If it doesn't, menstruation will occur and the embryo will be sloughed off with the uterine lining.
The brain is a very delicate structure with little room to move around. Surrounding the brain and the spinal cord are three protective layers in addition to the skull and the vertebral column. Directly surrounding the brain and spinal cord is the pia mater. Following the pia mater is the arachnoid mater. Between the pia mater and the arachnoid mater is the sub-arachnoid space where the cerebrospinal fluid circulates. Finally, the protective layer is the dura mater is loosely attached to the arachnoid mater but is strongly associated with the skull bone.
Depending on the type of injury, a certain type of vein and/or artery are more susceptible to injury. For example, the meningeal artery and vein run through the foramen spinosum and travel between the two layers making up the dura mater. As the artery and the vein are traveling in between the dura mater, there is a vulnerable region at the temple. A strike to the temple region could rupture these vessels and result in a epidural hematoma.
Traveling from the cerebral cortex to the venous dural sinus (located at certain regions between the two layers of the dura mater) is the cerebral vein. When an injury results in the dura mater shifting away from the arachnoid mater, the cerebral vein could rupture and lead to a subdural hematoma.
During a hematoma, the intracranial pressure could increase and push on certain regions of the brain. The compression of a certain region could either excite or inhibit the area. If patient A has been diagnosed with Cushing's syndrome (excess cortisol), which region(s) could be compressed?
Anterior pituitary
Posterior pituitary
Adrenal cortex
Adrenal medulla
Pineal gland
The anterior pituitary releases adrenocorticotropic hormone (ACTH). ACTH then binds receptors in the adrenal cortex and promotes the release of cortisol.