MCAT BIOLOGY UPDATED 2026 EXAM EVALUATION
QUESTIONS AND ANSWERS SURE A+
✔✔Hypothalamus
-location and mode of action? - ✔✔Bridge between nervous and endocrine systems.
They regulate the pituitary gland via tropic hormones. It acts on the pituitary gland
through paracrine release of hormones into a portal system directly connecting the 2
organs. It is regulated via negative feedback from a later hormone or product.
Located in forebrain
✔✔What does suprachiasmatic nucleus do? - ✔✔Receives light input from retina to
control sleep-wake cycle
In hypothalamus
✔✔Anterior Pituitary and Hypothalamus - ✔✔The anterior pituitary is regulated by the
hypothalamus via the hypophyseal portal system, that connects the two of them.
Hypophysis also means pituitary.
The hormone travels down the pituitary stalk and binds to receptors in the anterior
pituitary, releasing other hormones.
✔✔Tropic Hormones Released by the Hypothalamus and anterior pituitary's response -
✔✔GnRH -> FSH and LH
Growth hormone-releasing hormone GHRH -> increases Growth Hormone
Thyroid Releasing Hormone (TRH) -> increases Thyroid Stimulating Hormone (TSH)
Corticotropin-Releasing Factor (CRF) -> increases Adrenocorticotropic Hormone
(ACTH)
Prolactin Inhibiting Factor(PIF aka dopamine) -> DECREASES prolactin secretion
✔✔Describe how cortisol is released and the negative feedback system of cortisol -
✔✔So the hypothalamus releases CRF which tells Mr. Anterior Pituitary to release
ACTH which then tells the adrenal cortex to secrete cortisol. When cortisol levels get
too high, cortisol receptors in hypothalamus are like..."we better stop producing CRF"
which then tells anterior pituitary "we need to stop releasing ACTH" and adrenal cortex
doesnt secrete cortisol no more.
✔✔Axes - ✔✔Three organ systems to describe feedback control: hypothalamic-
pituitary-adrenal axis, hypothalamic-pituitary-ovarian axis, etc
,✔✔Posterior Pituitary - ✔✔Contains the nerve terminals of neurons with cell bodies in
the hypothalamus. Travel down the pituitary stalk to directly act on the posterior
pituitary.
Hormones: ADH and Oxytocin
✔✔Anterior Pituitary Products - ✔✔Tropic Hormones: FSH, LH, TSH, ACTH (FLAT)
Direct Hormones: Prolactin, Endorphins, Growth Hormone (PEG)
Mnemonic: FLAT PEG
✔✔What happens when hypothalamus releases Thyroid-releasing hormone -
✔✔Stimulates anterior pituitary to release TSH thyroid stimulating hormone, which acts
on thyroid gland
✔✔Anterior pituitary Tropic Hormones?
Anterior pituitary Direct Hormones? - ✔✔Tropic: FSH, LH, TSH (thyroid stim horm), and
adrenocorticotropic hormone (ACTH)
Direct: Prolactin, endorphins, growth hormone
✔✔Prolactin - ✔✔Stimulates milk production in the mammary glands. Decreased by
dopamine (Prolactin-inhibiting factor).
High level of estrogen and progesterone during pregnancy allow development of milk
ducts..after expulsion of placenta, estrogen, progesterone and dopamine levels drop
and the block on milk production is removed and lactation begins
First, nipple stimulation activates hypothalamus. Oxytocin release contracts breast's
smooth muscle and ejects milk from nipple. Hypothalamus also stops releasing
dopamine onto anterior pit., allowing prolactin release, causing milk production.
✔✔Endorphins - ✔✔Decrease the peception of pain.
✔✔Growth Hormone (GH) - ✔✔Promotes the growth of bone and muscle. Requires a
large amount of glucose, and prevents uptake in tissues that are not growing. GH is
stimulated by GHRH
-Gigantism, dwarfism (excess or deficit in GH before puberty, before growth plate
closure (epiphyseal plates)) and acromegaly (in adults) can result from too much/little
GH after they were shut
✔✔Posterior Pituitary and Hypothalamus interactions
what hormones are released by pituitary? - ✔✔Neurons in the hypothalamus send their
axons down the stalk. The released hormones are oxytocin and antidiuretic hormone
(vasopressin).
,✔✔ADH - ✔✔Secreted in response to low blood volume or increased blood osmolarity.
It increases permeability of the collecting duct to water so more water can passively
diffuse out of renal collecting duct. This results in greater reabsorption of water from the
filtrate in the nephron. This increases blood volume and blood pressure. Produced by
HYPOTHALAMUS but released by posterior pituitary
✔✔Does posterior pituitary make its hormones? - ✔✔no, hypothalamus makes ADH
and oxytocin and Posterior Pituitary simply secretes them
✔✔Oxytocin - ✔✔Secreted during childbirth, allows for contraction of uterine smooth
muscle, also involved in milk ejection through smooth muscle contraction in the breasts.
It is also involved in bonding.
It follows a positive feedback loop. Release of oxtocin promotes uterine contraction
which promotes more oxytocin release, which promotes stronger uterine contractions.
Produced by HYPOTHALAMUS but released by posterior pituitary
✔✔Thyroid Hormones: - ✔✔Controlled by Thyroid Stimulating Hormone, from the
anterior pituitary. It has two functions: setting basal metabolic rate and calcium
homeostasis.
Hormones: triiodothyronine (T3), and Thyroxine (T4) control metabolic rate
-Calcitonin is another hormone that controls calcium levels thats also secreted by
thyroid
✔✔T3 and T4 - ✔✔Triiodothyronine and thyroxine
-Both produced by the iodination of the amino acid tyrosine in the follicular cells of the
thyroid. They are capable of resetting the basal metabolic rate of the body by making
energy production more or less efficient, as well as altering the utilization of glucose and
fatty acids. Great amounts of T3 and T4 lead to increased cellular respiration and
greater protein and FA turnover by speeding up of synthesis and degradation.
Negative feedback, Increased levels decreases sensitivity of the anterior pituitary gland
which will decrease TSH secretion from hypothalamus
We have it more simple, T3 and T4 act on the APG.
-controlled by TSH from anterior pituitary
✔✔Hypothyroidism - ✔✔Too little thyroid hormones are secreted in insufficient amounts
or not at all. This results in lethargy, decreased body temperature, slowed respiration
and heart rate, cold intolerance, and weight gain. It can cause cretinism (mental
retardation/development delay) in children with low amounts.
, ✔✔Hyperthyroidism - ✔✔Excess thyroid hormone. Causes heightened activity, heat
intolerance, weight loss, higher HR, tumors
✔✔Calcitonin - ✔✔Produced by C-cells, it decreases calcium absorption from the gut,
increases storage of calcium in the bone, and increases calcium excretion from the
kidneys in attempts to lower plasma calcium levels.
Calcitonin TONES DOWN calcium levels in blood when they are too high
✔✔Parathyroid Glands - ✔✔4 small structures (Pea-sized) on the posterior surface of
the thyroid.
Hormones: Parathyroid Hormone (PTH)
✔✔Parathyroid Hormone - ✔✔-Antagonistic hormone to calcitonin, raises blood calcium
levels by decreasing excretion of calcium by the kidneys, increasing absorption of
calcium in the gut via Vitamin D, and increasing bone resorption which frees up Ca2+
-Affects phosphorus homeostasis by resorbing phosphate from bone and absorbing it in
the gut(increases Phosphate), and by reducing reabsorption of phosphate in kidney
(promotes excretion in urine) — cancel each other out
-It also activates Vitamin D, which is required for the absorption of calcium and
phosphate in the gut.
**** Overall effect is significant increase in blood calcium with little effect on phosphate
levels
✔✔What are roles of Calcium in body? - ✔✔bone structure, neutrotransmitter release,
regulates muscle contraction, clotting (calcium is cofact0r), exoctyosis, cell mvmt
✔✔Adrenal Cortex - ✔✔Secretes corticosteriods, which are steroid Hormones. 3 types:
Glucocorticoids, Mineralocorticoids, and Cortical Sex Hormones
✔✔Glucocorticoids - ✔✔Steroid hormones that regulate glucose levels and affect
protein metabolism. The two most common are cortisol and cortisone.
-They raise blood glucose by increasing gluconeogenesis and decreasing protein
synthesis. They decrease inflammation and immunologic response.
-Cortisol is released during stress, increasing blood sugar for dangerous situations.
-Glucocorticoid release is triggered via ACTH. CRF—>ACTH—>glucocort.
✔✔Mineralocorticoids - ✔✔Used in salt and water homeostasis, most profound effects
are on the kidneys. The most notable one is aldosterone, which increases sodium
reabsorption in the distal convoluted tubule and collecting duct of the nephron.
QUESTIONS AND ANSWERS SURE A+
✔✔Hypothalamus
-location and mode of action? - ✔✔Bridge between nervous and endocrine systems.
They regulate the pituitary gland via tropic hormones. It acts on the pituitary gland
through paracrine release of hormones into a portal system directly connecting the 2
organs. It is regulated via negative feedback from a later hormone or product.
Located in forebrain
✔✔What does suprachiasmatic nucleus do? - ✔✔Receives light input from retina to
control sleep-wake cycle
In hypothalamus
✔✔Anterior Pituitary and Hypothalamus - ✔✔The anterior pituitary is regulated by the
hypothalamus via the hypophyseal portal system, that connects the two of them.
Hypophysis also means pituitary.
The hormone travels down the pituitary stalk and binds to receptors in the anterior
pituitary, releasing other hormones.
✔✔Tropic Hormones Released by the Hypothalamus and anterior pituitary's response -
✔✔GnRH -> FSH and LH
Growth hormone-releasing hormone GHRH -> increases Growth Hormone
Thyroid Releasing Hormone (TRH) -> increases Thyroid Stimulating Hormone (TSH)
Corticotropin-Releasing Factor (CRF) -> increases Adrenocorticotropic Hormone
(ACTH)
Prolactin Inhibiting Factor(PIF aka dopamine) -> DECREASES prolactin secretion
✔✔Describe how cortisol is released and the negative feedback system of cortisol -
✔✔So the hypothalamus releases CRF which tells Mr. Anterior Pituitary to release
ACTH which then tells the adrenal cortex to secrete cortisol. When cortisol levels get
too high, cortisol receptors in hypothalamus are like..."we better stop producing CRF"
which then tells anterior pituitary "we need to stop releasing ACTH" and adrenal cortex
doesnt secrete cortisol no more.
✔✔Axes - ✔✔Three organ systems to describe feedback control: hypothalamic-
pituitary-adrenal axis, hypothalamic-pituitary-ovarian axis, etc
,✔✔Posterior Pituitary - ✔✔Contains the nerve terminals of neurons with cell bodies in
the hypothalamus. Travel down the pituitary stalk to directly act on the posterior
pituitary.
Hormones: ADH and Oxytocin
✔✔Anterior Pituitary Products - ✔✔Tropic Hormones: FSH, LH, TSH, ACTH (FLAT)
Direct Hormones: Prolactin, Endorphins, Growth Hormone (PEG)
Mnemonic: FLAT PEG
✔✔What happens when hypothalamus releases Thyroid-releasing hormone -
✔✔Stimulates anterior pituitary to release TSH thyroid stimulating hormone, which acts
on thyroid gland
✔✔Anterior pituitary Tropic Hormones?
Anterior pituitary Direct Hormones? - ✔✔Tropic: FSH, LH, TSH (thyroid stim horm), and
adrenocorticotropic hormone (ACTH)
Direct: Prolactin, endorphins, growth hormone
✔✔Prolactin - ✔✔Stimulates milk production in the mammary glands. Decreased by
dopamine (Prolactin-inhibiting factor).
High level of estrogen and progesterone during pregnancy allow development of milk
ducts..after expulsion of placenta, estrogen, progesterone and dopamine levels drop
and the block on milk production is removed and lactation begins
First, nipple stimulation activates hypothalamus. Oxytocin release contracts breast's
smooth muscle and ejects milk from nipple. Hypothalamus also stops releasing
dopamine onto anterior pit., allowing prolactin release, causing milk production.
✔✔Endorphins - ✔✔Decrease the peception of pain.
✔✔Growth Hormone (GH) - ✔✔Promotes the growth of bone and muscle. Requires a
large amount of glucose, and prevents uptake in tissues that are not growing. GH is
stimulated by GHRH
-Gigantism, dwarfism (excess or deficit in GH before puberty, before growth plate
closure (epiphyseal plates)) and acromegaly (in adults) can result from too much/little
GH after they were shut
✔✔Posterior Pituitary and Hypothalamus interactions
what hormones are released by pituitary? - ✔✔Neurons in the hypothalamus send their
axons down the stalk. The released hormones are oxytocin and antidiuretic hormone
(vasopressin).
,✔✔ADH - ✔✔Secreted in response to low blood volume or increased blood osmolarity.
It increases permeability of the collecting duct to water so more water can passively
diffuse out of renal collecting duct. This results in greater reabsorption of water from the
filtrate in the nephron. This increases blood volume and blood pressure. Produced by
HYPOTHALAMUS but released by posterior pituitary
✔✔Does posterior pituitary make its hormones? - ✔✔no, hypothalamus makes ADH
and oxytocin and Posterior Pituitary simply secretes them
✔✔Oxytocin - ✔✔Secreted during childbirth, allows for contraction of uterine smooth
muscle, also involved in milk ejection through smooth muscle contraction in the breasts.
It is also involved in bonding.
It follows a positive feedback loop. Release of oxtocin promotes uterine contraction
which promotes more oxytocin release, which promotes stronger uterine contractions.
Produced by HYPOTHALAMUS but released by posterior pituitary
✔✔Thyroid Hormones: - ✔✔Controlled by Thyroid Stimulating Hormone, from the
anterior pituitary. It has two functions: setting basal metabolic rate and calcium
homeostasis.
Hormones: triiodothyronine (T3), and Thyroxine (T4) control metabolic rate
-Calcitonin is another hormone that controls calcium levels thats also secreted by
thyroid
✔✔T3 and T4 - ✔✔Triiodothyronine and thyroxine
-Both produced by the iodination of the amino acid tyrosine in the follicular cells of the
thyroid. They are capable of resetting the basal metabolic rate of the body by making
energy production more or less efficient, as well as altering the utilization of glucose and
fatty acids. Great amounts of T3 and T4 lead to increased cellular respiration and
greater protein and FA turnover by speeding up of synthesis and degradation.
Negative feedback, Increased levels decreases sensitivity of the anterior pituitary gland
which will decrease TSH secretion from hypothalamus
We have it more simple, T3 and T4 act on the APG.
-controlled by TSH from anterior pituitary
✔✔Hypothyroidism - ✔✔Too little thyroid hormones are secreted in insufficient amounts
or not at all. This results in lethargy, decreased body temperature, slowed respiration
and heart rate, cold intolerance, and weight gain. It can cause cretinism (mental
retardation/development delay) in children with low amounts.
, ✔✔Hyperthyroidism - ✔✔Excess thyroid hormone. Causes heightened activity, heat
intolerance, weight loss, higher HR, tumors
✔✔Calcitonin - ✔✔Produced by C-cells, it decreases calcium absorption from the gut,
increases storage of calcium in the bone, and increases calcium excretion from the
kidneys in attempts to lower plasma calcium levels.
Calcitonin TONES DOWN calcium levels in blood when they are too high
✔✔Parathyroid Glands - ✔✔4 small structures (Pea-sized) on the posterior surface of
the thyroid.
Hormones: Parathyroid Hormone (PTH)
✔✔Parathyroid Hormone - ✔✔-Antagonistic hormone to calcitonin, raises blood calcium
levels by decreasing excretion of calcium by the kidneys, increasing absorption of
calcium in the gut via Vitamin D, and increasing bone resorption which frees up Ca2+
-Affects phosphorus homeostasis by resorbing phosphate from bone and absorbing it in
the gut(increases Phosphate), and by reducing reabsorption of phosphate in kidney
(promotes excretion in urine) — cancel each other out
-It also activates Vitamin D, which is required for the absorption of calcium and
phosphate in the gut.
**** Overall effect is significant increase in blood calcium with little effect on phosphate
levels
✔✔What are roles of Calcium in body? - ✔✔bone structure, neutrotransmitter release,
regulates muscle contraction, clotting (calcium is cofact0r), exoctyosis, cell mvmt
✔✔Adrenal Cortex - ✔✔Secretes corticosteriods, which are steroid Hormones. 3 types:
Glucocorticoids, Mineralocorticoids, and Cortical Sex Hormones
✔✔Glucocorticoids - ✔✔Steroid hormones that regulate glucose levels and affect
protein metabolism. The two most common are cortisol and cortisone.
-They raise blood glucose by increasing gluconeogenesis and decreasing protein
synthesis. They decrease inflammation and immunologic response.
-Cortisol is released during stress, increasing blood sugar for dangerous situations.
-Glucocorticoid release is triggered via ACTH. CRF—>ACTH—>glucocort.
✔✔Mineralocorticoids - ✔✔Used in salt and water homeostasis, most profound effects
are on the kidneys. The most notable one is aldosterone, which increases sodium
reabsorption in the distal convoluted tubule and collecting duct of the nephron.
