NUSCTX 11 Final Exam Questions and Answers Already Passed
How does the endocrine system work? - Answers Endocrine means "internal secretion" - it is a system of
glands that secrete or release signaling molecules called hormones that affect the physiology of
particular organs; the endocrine system regulates many different aspects of physiology (development,
growth, metabolism, mood, behaviors, specific tissue function)
The brain, especially the hypothalamus, produces regulatory hormones while the pituitary gland
secretes hormones controlling specific hormones secreted by the endocrine glands
What are hormones? - Answers Hormones are a class of substances that are produced by endocrine
glands that are secreted into the blood (circulatory system), which is why they can travel far int he body
and target specific organs
They are potent chemicals (powerful and don't need a very high concentration of molecules to exert
biological actions) - when measuring hormone levels in the body, they are in very low concentrations
(picomolar or nanomolar) because they are so potent and need to be maintained in a narrow range (too
much or too littel can cause different issues, leading to various diseases and disorders)
Three Main Categories of Hormones - Answers Peptide hormones: chains of amino acids (building blocks
for proteins); between 3-20 amino acids (longer chain that are protein hormones); have different
charges (positive, negative, neutral); the longer the chain, start forming tertiary structures and fold
together because of various charges; majority of hormones in the body are peptide hormones,
chemically water soluble - example: insulin, glucagon
Amine Hormones: in organic chemistry, an NH2 group attached to a carbon ring (derived from amino
acids as well - single amino acid, mostly tyrosine); also water-soluble since they come from amino acids,
except for thyroid hormones (which structurally contain iodine, making them lipophilic) - example:
catecholamines, thyroid hormones
Steroid Hormones: lipophilic (made of lipids), derived from cholesterol (lot of carbon rings and a
pentagon ring, methyl groups - do not see this in any of the hydrophilic groups) - examples: sex
hormone, glucocorticoids
Water-Soluble Signaling - Answers Receptors are embedded within the cell membrane - if it is secreted
from the original gland, it travels in the blood, only recognizes cell type that has the receptor in the
membrane; water-soluble hormones are unable to pass through cell-membranes (which is why
receptors are embedded in the membrane, so that they can bind to the receptor without having to pass
,through); membrane-bound receptors have a polar signal exposed to external cell environment (water-
soluble hormones travel in the blood, bind to polar part of receptor, and have internal signaling
molecules to carry out hormone signals and effects inside the cell)
Dissolve in water (hydrophilic) because they are formed from amino acids (cannot pass through target
cell membrane) - examples include insulin, glucagon, catecholamines (dopamine, epinephrine,
norepinephrine)
Because it binds to the cell surface receptors, for signaling effects to take place, pathway requires
second messengers to mediate the signaling (cAMP and cGMP - other proteins help amplify the signaling
from the hormone and carry it out inside of the cell)
Epinephrine Hormone Signaling - Answers Epinephrine is secreted from the adrenal gland, biological
function is to mediate fight-or-flight response; initial secretion is from the adrenal gland into blood
system, travel in circulatory system to identified targets; epinephrine acts on the cell because it is a
target cel (express its own specific receptor)
Binds to its receptor (without binding, receptor is inactivated with G protein bound to GDP molecule,
gamma and beta subunits inhibitory; when bound, it becomes activated - GDP exchanged from GTP,
beta and gamma unit come off); once bound to GTP, highly active and can bind to next part of signaling
pathway (enzyme adenylate cyclase, which converts ATP to cAMP, a second messenger)
cAMP can cause a robust response and mediate a lot of the downstream actions (ex: activate protein
kinase A)
Insulin and Glucagon - Answers Insulin: maintain glucose homeostasis by regulating plasma blood
glucose levels (regulates carbohydrates, fat, and proteins, has an anabolic action [absorbs or stores
energy], works to maintain and lower blood glucose levels by uptaking glucose from blood circulation
and depositing into fat and muscle tissue) - secreted when blood glucose levels are too high (usually
after eating a meal)
Glucagon: work to maintain glucose homeostasis by regulating plasma blood glucose levels; catabolic
(breaks down and is secreted from the pancreas); goal is to generate more plasma blood glucose
(glycogenolysis [breakdown of different tissue glycogen and glucose stores, release into blood, increase
blood plasma glucose levels when low] and gluconeogenesis [produce glucose from breaking down
different tissues like adipose and muscle])
, Insulin works to lower blood glucose levels (if blood glucose levels are low, do not want to increase
insulin); glucagon works to increase blood glucose levels (glucagon is higher when blood glucose levels
are low)
When blood glucose is low, there is no reason to have insulin; as eat, levels start to climb (body will
work to try and lower blood glucose levels, insulin spikes); when blood glucose levels are higher because
of eating, no reason to continue raising levels (glucagon tapers down after meals)
Fat-Soluble Hormone Signaling - Answers Lipophilic, can pass through lipid bilayer without tissue,
receptors inside cell in cytosol - once hormones bind to the receptor, the function of nuclear receptors
are that they can add a transcription factor (bound, enter nucleus, mediate actions of causing and
affecting gene expression)
Dissolve in fat rather than water because they are made from cholesterol and can pass through the cell
membrane (can enter cell, receptors located intracellularly) - examples include glucocorticoids, thyroid
hormones, estrogen, aldosterone, and testosterone
Example: Glucocorticoid receptor is intracellular and works as a transcription factor (bind to promoters
of target genes, help induce transcription of a gene); don't always want transcription factors to be active
(gene expression and protein synthesis need to be controlled) - nuclear receptors are inactive in cytosol
when there is no hormone bound to it (HSP complex is a chaperone protein complex that holds receptor
inactive when there is no steroid hormone, comes off when steroid hormone binds, allows receptor to
enter nucleus)
How to regulate hormone secretion? - Answers Insulin and Glucagon are counter-regulatory (one
promotes and other suppresses glucose levels) - not all hormones int he body have a pair
Negative Feedback Inhibition System: starts with hypothalamus (secretes particular "releasing"
hormones to anterior pituitary), anterior pituitary secretes "stimulating" hormones that travel in the
blood to target peripheral endocrine glands (which secrete hormones to carry out physiological actions)
Example: HPT Axis - hypothalamus secretes TRH, which signals to the anterior pituitary to secrete TSH
(Thyroid-Stimulating Hormone); TSH enters the blood stream, travels to thyroid gland, and tells the
thyroid gland to create thyroid hormones T3 and T4; when there is enough T3 and T4, negative signal
feeds into upper layers of axis to suppress the anterior pituitary and hypothalamus (less TRH and less
How does the endocrine system work? - Answers Endocrine means "internal secretion" - it is a system of
glands that secrete or release signaling molecules called hormones that affect the physiology of
particular organs; the endocrine system regulates many different aspects of physiology (development,
growth, metabolism, mood, behaviors, specific tissue function)
The brain, especially the hypothalamus, produces regulatory hormones while the pituitary gland
secretes hormones controlling specific hormones secreted by the endocrine glands
What are hormones? - Answers Hormones are a class of substances that are produced by endocrine
glands that are secreted into the blood (circulatory system), which is why they can travel far int he body
and target specific organs
They are potent chemicals (powerful and don't need a very high concentration of molecules to exert
biological actions) - when measuring hormone levels in the body, they are in very low concentrations
(picomolar or nanomolar) because they are so potent and need to be maintained in a narrow range (too
much or too littel can cause different issues, leading to various diseases and disorders)
Three Main Categories of Hormones - Answers Peptide hormones: chains of amino acids (building blocks
for proteins); between 3-20 amino acids (longer chain that are protein hormones); have different
charges (positive, negative, neutral); the longer the chain, start forming tertiary structures and fold
together because of various charges; majority of hormones in the body are peptide hormones,
chemically water soluble - example: insulin, glucagon
Amine Hormones: in organic chemistry, an NH2 group attached to a carbon ring (derived from amino
acids as well - single amino acid, mostly tyrosine); also water-soluble since they come from amino acids,
except for thyroid hormones (which structurally contain iodine, making them lipophilic) - example:
catecholamines, thyroid hormones
Steroid Hormones: lipophilic (made of lipids), derived from cholesterol (lot of carbon rings and a
pentagon ring, methyl groups - do not see this in any of the hydrophilic groups) - examples: sex
hormone, glucocorticoids
Water-Soluble Signaling - Answers Receptors are embedded within the cell membrane - if it is secreted
from the original gland, it travels in the blood, only recognizes cell type that has the receptor in the
membrane; water-soluble hormones are unable to pass through cell-membranes (which is why
receptors are embedded in the membrane, so that they can bind to the receptor without having to pass
,through); membrane-bound receptors have a polar signal exposed to external cell environment (water-
soluble hormones travel in the blood, bind to polar part of receptor, and have internal signaling
molecules to carry out hormone signals and effects inside the cell)
Dissolve in water (hydrophilic) because they are formed from amino acids (cannot pass through target
cell membrane) - examples include insulin, glucagon, catecholamines (dopamine, epinephrine,
norepinephrine)
Because it binds to the cell surface receptors, for signaling effects to take place, pathway requires
second messengers to mediate the signaling (cAMP and cGMP - other proteins help amplify the signaling
from the hormone and carry it out inside of the cell)
Epinephrine Hormone Signaling - Answers Epinephrine is secreted from the adrenal gland, biological
function is to mediate fight-or-flight response; initial secretion is from the adrenal gland into blood
system, travel in circulatory system to identified targets; epinephrine acts on the cell because it is a
target cel (express its own specific receptor)
Binds to its receptor (without binding, receptor is inactivated with G protein bound to GDP molecule,
gamma and beta subunits inhibitory; when bound, it becomes activated - GDP exchanged from GTP,
beta and gamma unit come off); once bound to GTP, highly active and can bind to next part of signaling
pathway (enzyme adenylate cyclase, which converts ATP to cAMP, a second messenger)
cAMP can cause a robust response and mediate a lot of the downstream actions (ex: activate protein
kinase A)
Insulin and Glucagon - Answers Insulin: maintain glucose homeostasis by regulating plasma blood
glucose levels (regulates carbohydrates, fat, and proteins, has an anabolic action [absorbs or stores
energy], works to maintain and lower blood glucose levels by uptaking glucose from blood circulation
and depositing into fat and muscle tissue) - secreted when blood glucose levels are too high (usually
after eating a meal)
Glucagon: work to maintain glucose homeostasis by regulating plasma blood glucose levels; catabolic
(breaks down and is secreted from the pancreas); goal is to generate more plasma blood glucose
(glycogenolysis [breakdown of different tissue glycogen and glucose stores, release into blood, increase
blood plasma glucose levels when low] and gluconeogenesis [produce glucose from breaking down
different tissues like adipose and muscle])
, Insulin works to lower blood glucose levels (if blood glucose levels are low, do not want to increase
insulin); glucagon works to increase blood glucose levels (glucagon is higher when blood glucose levels
are low)
When blood glucose is low, there is no reason to have insulin; as eat, levels start to climb (body will
work to try and lower blood glucose levels, insulin spikes); when blood glucose levels are higher because
of eating, no reason to continue raising levels (glucagon tapers down after meals)
Fat-Soluble Hormone Signaling - Answers Lipophilic, can pass through lipid bilayer without tissue,
receptors inside cell in cytosol - once hormones bind to the receptor, the function of nuclear receptors
are that they can add a transcription factor (bound, enter nucleus, mediate actions of causing and
affecting gene expression)
Dissolve in fat rather than water because they are made from cholesterol and can pass through the cell
membrane (can enter cell, receptors located intracellularly) - examples include glucocorticoids, thyroid
hormones, estrogen, aldosterone, and testosterone
Example: Glucocorticoid receptor is intracellular and works as a transcription factor (bind to promoters
of target genes, help induce transcription of a gene); don't always want transcription factors to be active
(gene expression and protein synthesis need to be controlled) - nuclear receptors are inactive in cytosol
when there is no hormone bound to it (HSP complex is a chaperone protein complex that holds receptor
inactive when there is no steroid hormone, comes off when steroid hormone binds, allows receptor to
enter nucleus)
How to regulate hormone secretion? - Answers Insulin and Glucagon are counter-regulatory (one
promotes and other suppresses glucose levels) - not all hormones int he body have a pair
Negative Feedback Inhibition System: starts with hypothalamus (secretes particular "releasing"
hormones to anterior pituitary), anterior pituitary secretes "stimulating" hormones that travel in the
blood to target peripheral endocrine glands (which secrete hormones to carry out physiological actions)
Example: HPT Axis - hypothalamus secretes TRH, which signals to the anterior pituitary to secrete TSH
(Thyroid-Stimulating Hormone); TSH enters the blood stream, travels to thyroid gland, and tells the
thyroid gland to create thyroid hormones T3 and T4; when there is enough T3 and T4, negative signal
feeds into upper layers of axis to suppress the anterior pituitary and hypothalamus (less TRH and less
