Lecture 7: Hormones/Endocrine System

Neurohormones are released into the _____________, and then taken to target cell

blood (capillaries)

Prolactin stimulates __________________________ and is inhibited by this hormone

breast development/milk production inhibited by DOPAMINE

The endocrine system is a group of organs that secrete hormones directly into ________________________ to be carried to distant organs

circulatory system

Neural control center for all endocrine systems

hypothalamus

Regulatory hormones are produced in the _________________

hypothalamus *controls production of hormones in pituitary gland

Hormones can activate genes via amplification. Amplification is at the level of ___________ and ___________ synthesis

mRNA and protein ------------ 1. steroid/thyroid hormone diffuses through membrane of target cell 2. hormone enters nucleus and binds to intranuclear receptor 3. hormone-receptor complex binds to specific DNA sequence 4. binding initiates TRANSCRIPTION of gene to mRNA 5. mRNA → protein synthesis

In the anterior pituitary gland, the neurohormones are stored in the ________________________

median eminence

Hormone synthesis is controlled via this mechanism

negative feedback

Posterior pituitary gland = _____________ tissue Anterior pituitary gland = _______________ tissue

posterior = neural tissue anterior = endocrine tissue

Hypothalamus secretes neurohormones into the ___________________ for storage

posterior pituitary gland

The _______________ gland stores neurohormones and has its own arterial blood supply

posterior pituitary gland

5 hormones released by anterior pituitary gland

1) ACTH (adrenocorticotrophic hormone) 2) TSH (thyroid-stimulating hormone) 3) LH (leutinizing hormone) 4) FSH (follicle-stimulating hormone) 5) GH (growth hormone) 6) PRL (prolactin)

2 hormones released by the posterior pituitary gland

1) ADH (anti-diuretic hormone) 2) OCT (oxytocin)

Paracrine vs Autocrine agents (2 forms of chemical signaling)

1. Paracrine agent: secreted from one cell and then act on nearby cells 2. Autocrine agent: acts on the SAME cell that secreted them

4 metabolic fates of plasma hormones (prohormones) (What happens to hormones after they are released?)

1. excreted 2. inactivated by metabolism 3. activated by metabolism → action on target cell 4. catalyzes formation of active hormone from plasma protein → action on target cell *secreted hormone may be unable to act upon a target cell until metabolism transforms it into a substance that can act

3 types of hormones

1. hormone (from hormone-secreting gland cell) 2. neurotransmitter (from nerve cell) 3. neurohormone (from nerve cell)

Cortisol Pathway 1. hypothalamus → 2. anterior pituitary → 3. adrenal cortex → short-negative feedback loop = long-negative feedback loop =

1. hypothalamus → CRH (cortisol-releasing hormone) 2. anterior pituitary → ACTH (adrenocorticotrophic hormone) 3. adrenal cortex → cortisol short-negative feedback loop = cortisol to ACTH long-negative feedback loop = cortisol to CRH

Growth hormone pathway 1. hypothalamus → 2. anterior pituitary → 3. various organs and tissues →

1. hypothalamus → GHRH 2. anterior pituitary → GH 3. various organs and tissues → stimulates PROTEIN SYNTHESIS and influences carbohydrate and lipid metabolism ex) liver → IGF-1 (insulin-like growth factor)

Gonadotropin pathway 1. hypothalamus → 2. anterior pituitary → 3. gonads →

1. hypothalamus → GnRH 2. anterior pituitary → FSH and LH 3. gonads → stimulates germ cell development; stimulates sex hormones (testosterone, estrogen, progesterone)

Thyroid hormone pathway 1. hypothalamus → 2. anterior pituitary → 3. thyroid →

1. hypothalamus → TRH 2. anterior pituitary → TSH, prolactin 3. thyroid → T3, T4 *regulates METABOLISM

This hormone is released in response to stress

Cortisol

The cAMP second messenger system is an example of hormone __________________

amplification -second messenger = cAMP -most signaling molecules are found in such low concentrations that their effects in the cytoplasm would be minimal unless the signal were AMPLIFIED

This hormone is released in response to exercise, stress, fasting, low plasma glucose, and sleep

Growth hormone

Master gland of hormone regulation

Pituitary gland

This hormone inhibits both GH and TSH

Somatostatin (SS) aka GHIH (growth hormone-inhibiting hormone)

Epinephrine and norepinephrine is secreted by the

adrenal medulla