MCAT Biology - The Endocrine System

Chapter 5

Hormones

Signaling molecules secreted directly into the blood stream to distant target tissue

Peptide Hormone

Made up of amino acids ranging in size from small to relatively large

Chemical Precursor of peptide hormone

Amino acid

Chemical precursor of steriod hormone

Chloesterol

Location of receptor peptide hormone

Extracellular (cell membrane)

Location fo receptor Steriod Hormone

Intracellular or intranuclear

Mechanism of action Peptide hormone

Stimulates a receptor affecting levels of second messengers initiates signal cascade

Mechanism of Action Steriod Hormone

Binds to receptor induces conformational change and regulates transcription level of DNA

Method Travel in blood stream peptide hormone

dissolves and travels freely

Method of Travel in bloodstream steriod hormone

Bind to a carrier protein

Speed of onset peptide hormone

quick

Speed of onset steroid hormone

slow

Duration of action peptide hormone

short lived

Duration of action steriod hormone

long lived

Signaling cascade

connection between hormone at the surface and the effect brough about by second messenger within the cell

Common Second Messengers

cAMP, IP3,, calcium

Adenylate cyclase

Inhibit or activates levels of cAMP

Steriod Hormones

derived from chloestrol and produced by gonads or adrenal cortex.

Dimerization

Pairing of two receptor hormone complexes

Amino acid derative hormones

Derived from one or two amino acids, usually with few additional modification

Direct hormones

secreted and act directly on target tissue

Tropic Hormone

Require an intermediate to act

Gonadotropin Releasing Hormone GnRH, Hormone from anterior pituitary

Follicle stimulating hormone and lutenizing hormone

Gonadotropin Releasing Hormone GnRH Target organs

Gonads

Hormone released by gonads

Testosterone estrogen and progesterone

Corticotropin Releasing factor Hormone from anterior pituitary

Adrenocorticotropic Hormone (ACTH)

Corticotropin Releasing factor target organ

Adrena Cortex

Hormone released by adrenal cortex

Glucocorticoids

Thyroid Releasing Hormone, hormone from anterioir pituitary

Thyroid stimulating hormone

Thyroid Releasing Hormone Target organ

Thyroid

Hormone released from Thyroid

Triidothyronre and thyroxine

Dopamine, hormone from anterior pituitary

Prolactin

Dopamine target organ

Breast tissue

Growth Hormone, Releasing Hormone, Hormone from anterior pituitary

Growth Hormone

Growth Hormone Target Organ

Bone, Muscle

Negative Feedback

When a hormone later in the pathway inhibits hormone earlier in the pathway

Axes

Three organ systems

Tropic Hormone of anterior pituitary

FSH LH ACTH TSH

Direct hormones of anterior pituitary

Prolactin, Endorphins, GH

Hypothyroidism

defiency of iodine or inflammation of thyroid

Hyperthyroidism

Result from excess thyroid

Class of Sterior Hormone

Glucocorticoids, Mineralocorticoids, Cortical Sex Hormone

Type I Diabetes

Caused by autoimmune destruction B cells of pancreases low insulin production

Type II Diabetes

Receptor level resistance to effects of insulin

Follicle Stimulating Hormone Source

Anterior Pituitary

Follicile Stimulating Hormone Type

Peptide

Follicile Stimulating Hormone Action

Stimulates follicle maturation in females, spermatogensis in males

lutenizing Hormone Source

Anterior pituitary

lutenizing Hormone type

Peptide

lutenizing Hormone action

Stimulates ovulation in females, testosterone synthesis in males

Adrenocorticotropic Hormone Source

Anterior Pituitary

Adrenocorticotropic Hormone Type

Peptide

Adrenocorticotropic Hormone Action

Stimulates the adrenal cortex to synthesize and secrete glucocorticoids

Thyroid Stimulating Hormone Source

Anterior Pituitary

Thyroid Stimulating Hormone Type

Peptide

Thyroid Stimulating Hormone Action

Stimulates the thyroid to produce thyroid hormones

Prolactin Source

Anterior Source

Prolactin Type

Peptide

Prolactin Action

Stimulates milk production and secretion

Endorphins Source

Anterior Pituitary

Endorphin Type

Peptide

Endorphin Action

Decrease sesnation of pain, promote euphoria

Growth Hormone Source

Anterior Pituitary

Growth Hormone Type

Peptide

Growth Hormone Action

Stimulates bone and muscle growth, raises blood glucose levels

Antidiuretic Hormone Source

Hypothalamus (released by posterior pituitary)

Antidiuretic Hormone Type

Peptide

Antidiuretic Hormone Action

Stimulates water reabsorption in kidneys by increasing permeability of collecting duct

Oxytocin Hormone Source

Hypothalamus (released by posterior pituitary)

Oxytocin Hormone Type

Peptide

Oxytocin Action

Stimulates uterine contractions during labor and milk secretion during lactation, may promote bonding behavior

Triidothyronine T3 and Thyroxine T4 Source

Thyroid (follicular cells)

Triidothyronine T3 and Thyroxine T4 Type

Amino Acid Deratitive

Triidothyronine T3 and Thyroxine T4 Action

Stimulate metabolic activity

Calcitonin Source

Thyroid (parafollicular or C cells)

Calcitonin Type

Peptide

Calcitonin Actions

Decrease blood calcium concentrations

Parathyroid Hormone Source

Parathyroid

Parathyroid Hormone Type

Peptide

Parathyroid Hormone Action

Increase blood calcium concentration

Glucocorticoids (Cortisol and Cortisone) Source

Adrenal Cortex

Glucocorticoids (Cortisol and Cortisone) Type

Steroid

Glucocorticoids (Cortisol and Cortisone) Action

Increase blood glucose concentrations, decrease protein synthesis anti inflammatory

Mineralocorticoids (aldosterone) Source

Adrenal Cortex

Mineralocorticoids (aldosterone) Type

Steroid

Mineralocorticoids (aldosterone) Action

Increase water reabsorption in the kidneys by increasing sodium reabsorption, promote potassium and hydrogen ion excretion

Epinephrine and Norepinephrine Source

Adrenal Medulla

Epinephrine and Norepinephrine Source

Amino acid derative

Epinephrine and Norepinephrine Action

Increase blood glucose concentrations and heart rate, dilate bronchi, alter blood flow patterns

Glucagon Source

Pancreas (a cells)

Glucagon Type

Peptide

Glucagon Action

Stimulates glycogen breakdown, increase blood glucose concentrations

Insulin Source

Pancreas (B cells)

Insulin type

peptide

Insulin action

lowers blood glucose concentrations and promotes anabolic processes

Somatostatin Source

Pancreas (delta cells)

Somatostatin Type

Peptide

Somatostatin Action

Suppresses secretion of glucagon and insulin

Testosterone Source

Testis and adrenal cortex

Testosterone Type

Steriod