The Endocrine SystemThe Endocrine System

Janie GuJanie GuTimothy JuwonoTimothy Juwono

Alick ShiuAlick ShiuRichard ZhangRichard Zhang

Endocrine Vs. Endocrine Vs. NervousNervous

• The endocrine The endocrine system coordinates system coordinates slower and longer slower and longer response to response to stimulus.stimulus.

• Regulates growth Regulates growth and homeostatic and homeostatic processes.processes.

• The nervous The nervous system coordinates system coordinates response to sudden response to sudden environmental environmental changes through changes through high-speed high-speed electrical signals.electrical signals.

Negative and Positive Negative and Positive FeedbackFeedback• Negative Feedback: the response from the Negative Feedback: the response from the

effector reduces the initial stimulus.effector reduces the initial stimulus.

• Positive Feedback: the response triggers Positive Feedback: the response triggers amplification of the stimulus, leading to a amplification of the stimulus, leading to a greater response greater response

HormonesHormonesProtein vs. SteroidsProtein vs. Steroids

• Protein hormones Protein hormones are water-soluble.are water-soluble.

• Protein hormones Protein hormones bind to the bind to the receptor receptor extracellularly (on extracellularly (on the surface of a the surface of a target cell).target cell).

• Steroid hormones Steroid hormones are not water-are not water-soluble.soluble.

• Steroid hormones Steroid hormones bind to the bind to the receptor receptor intracellularly intracellularly (inside the cell).(inside the cell).

Hormone and Receptor Hormone and Receptor InteractionInteraction

• Hormone and receptor interactions are Hormone and receptor interactions are based on the target cell, the receptor, and based on the target cell, the receptor, and the species.the species.

Paracrine SignalingParacrine Signaling

• Paracrine Signaling is Paracrine Signaling is

the process in which localthe process in which local

regulators convey messages regulators convey messages

between neighboring cells. between neighboring cells.

(Short distance signaling)(Short distance signaling)

• An example of this would be An example of this would be prostagladins, which help induce prostagladins, which help induce fever and inflammation as well as fever and inflammation as well as intensify pain. intensify pain.

Ligands and Ligand-gated Ligands and Ligand-gated ChannelsChannels

• A ligand is a molecule that binds A ligand is a molecule that binds specifically to a receptor side of another specifically to a receptor side of another molecule.molecule.

• A ligand-gated channel is a type of A ligand-gated channel is a type of membrane receptor, which has a “gate.”membrane receptor, which has a “gate.”

• When the ligand binds to the receptor, When the ligand binds to the receptor, the gate opens and specific ions can flow the gate opens and specific ions can flow through and change the concentration of through and change the concentration of that ion in the cell. This may directly that ion in the cell. This may directly change the activity of the cell.change the activity of the cell.

Ligand/Receptor Ligand/Receptor InteractionsInteractions• G-protein linked G-protein linked

receptor is a receptor is a plasma plasma membrane that membrane that works with G works with G proteins.proteins.

• When activated When activated by a signal by a signal molecule, the molecule, the receptor causes a receptor causes a G protein to G protein to activate. activate.

• The G protein The G protein then binds to an then binds to an enzyme and enzyme and alters its activity.alters its activity.

• Receptor tyrosine kinases is Receptor tyrosine kinases is characterized by enzymatic characterized by enzymatic activity.activity.

• When bonded to a signal When bonded to a signal molecule, the two molecule, the two polypeptide receptors touch. polypeptide receptors touch.

• When fully activated, the When fully activated, the receptor proteing is receptor proteing is recognized by proteins in the recognized by proteins in the cell.cell.

• The proteins bind to a The proteins bind to a phosphorylated tyrosine and phosphorylated tyrosine and undergo structural change.undergo structural change.

• Each activated protein Each activated protein triggers a transduction triggers a transduction pathway.pathway.

Second MessengersSecond Messengers

• A second messenger relays a signal A second messenger relays a signal to a cell’s interior in response to a to a cell’s interior in response to a signal received by a signal receptor signal received by a signal receptor protein.protein.

• Second messengers are small, Second messengers are small, nonprotein, water-soluble molecule nonprotein, water-soluble molecule or ion.or ion.

• Examples: calcium ion, or cyclic AMP. Examples: calcium ion, or cyclic AMP.

Duct and Ductless GlandsDuct and Ductless Glands

• Duct glands are Duct glands are glands that secrete glands that secrete their messengers their messengers through ducts.through ducts.

• Ductless glands are Ductless glands are glands that secrete glands that secrete their chemical their chemical messengers messengers directly to directly to extracellullar fluid.extracellullar fluid.

A duct is a vessel, canal, or tube that A duct is a vessel, canal, or tube that conveys body fluids, especially conveys body fluids, especially secretions and excretions.secretions and excretions.

Hypothalamus and Anterior Hypothalamus and Anterior PituitaryPituitary

• It is on the underside of the brain that It is on the underside of the brain that receives information from throughout the receives information from throughout the body and brain and initiates endocrine body and brain and initiates endocrine signals to adapt to the conditions. signals to adapt to the conditions.

• The anterior pituitary is a fold of tissue at The anterior pituitary is a fold of tissue at the roof of the embryonic mouth. It is the roof of the embryonic mouth. It is stimulated by the tropic hormones of the stimulated by the tropic hormones of the hypothalamus. It secretes at least six hypothalamus. It secretes at least six different hormones.different hormones.

• Both the hypothalamus and anterior Both the hypothalamus and anterior pituitary control the secretion of the pituitary control the secretion of the thyroid gland.thyroid gland.

Thyroid & Parathyroid Thyroid & Parathyroid GlandsGlands

• The thyroid gland The thyroid gland stimulates and stimulates and maintains maintains metabolic metabolic processes.processes.

• It also secretes It also secretes calcitonin to lower calcitonin to lower blood calcium blood calcium levels.levels.

• The parathyroid The parathyroid gland secretes gland secretes prathyroid hormones prathyroid hormones to raise calcium to raise calcium blood levels.blood levels.

• They are four small They are four small structures, structures, embedded in the embedded in the surface of the surface of the thyroid.thyroid.

Iodine DeficiencyIodine Deficiency• A Deficiency in Iodine in a person’s diet can A Deficiency in Iodine in a person’s diet can

result in a goiter. result in a goiter.

• A goiter is an enlargement of the thyroid gland.A goiter is an enlargement of the thyroid gland.

• Without sufficient iodine, the thyroid gland Without sufficient iodine, the thyroid gland can’t synthesize adequate amounts of can’t synthesize adequate amounts of triiodothyronine and thyroxine.triiodothyronine and thyroxine.

• This causes low blood levels of the two and This causes low blood levels of the two and negative feedback on the hypothalamus and negative feedback on the hypothalamus and anterior pituitary to be altered. anterior pituitary to be altered.

• This causes the anterior pituitary to This causes the anterior pituitary to continuously secrete TSH and enlarge the continuously secrete TSH and enlarge the thyroid.thyroid.

Thymus GlandThymus Gland

• The thymus gland is a peptide that The thymus gland is a peptide that secretes thymosin. secretes thymosin.

• This stimulates the production of certain This stimulates the production of certain infection-fighting cells, especially the infection-fighting cells, especially the maturation of T cells.maturation of T cells.

The PancreasThe Pancreas• The pancreas regulates blood sugar in The pancreas regulates blood sugar in

the body.the body.• It secretes insulin and glucagon.It secretes insulin and glucagon.• When blood glucose levels become to When blood glucose levels become to

low, glucagon is secreted and broken low, glucagon is secreted and broken down by the liver into glucose and down by the liver into glucose and released into the blood.released into the blood.

• When blood glucose levels become to When blood glucose levels become to high, insulin is secreted to cause liver high, insulin is secreted to cause liver to take and store glucose as glucagon.to take and store glucose as glucagon.

EpinephrineEpinephrine

• Epinephrine is secreted from the adrenal Epinephrine is secreted from the adrenal medulla.medulla.

• They are part of the class of compounds, They are part of the class of compounds, catecholamines. catecholamines.

• It works directly on several target tissues and It works directly on several target tissues and give the body a rapid bioenergetic boost. give the body a rapid bioenergetic boost.

• It also increases both the rate and the stoke It also increases both the rate and the stoke volume of the heartbeat and dilate the volume of the heartbeat and dilate the bronchioles in the lungs, which increase the bronchioles in the lungs, which increase the rate of oxygen delivery to body cells.rate of oxygen delivery to body cells.

Gonadotropic HormonesGonadotropic Hormones

• FSH and LH are secreted by GnRH in FSH and LH are secreted by GnRH in the hypothalamus.the hypothalamus.

• These hormones control the These hormones control the synthesis of androgens and synthesis of androgens and estrogens. estrogens.

Gonadal Sex HormonesGonadal Sex Hormones

• The gonads secrete three types of hormones.The gonads secrete three types of hormones.

• Androgens- stimulate the development and Androgens- stimulate the development and maintenance of the male reproductive maintenance of the male reproductive system and human male secondary sex system and human male secondary sex characteristics.characteristics.

• Estrogens- responsible for the maintenance Estrogens- responsible for the maintenance of the female reproductive system and of the female reproductive system and female secondary sex characteristics.female secondary sex characteristics.

• Progestins- involved in preparing and Progestins- involved in preparing and maintaining the uterus in mammals, which maintaining the uterus in mammals, which supports the growth and development of the supports the growth and development of the embryo.embryo.