Human Phys: chapter 8 endocrine/hormones

Hormones

chemical messengers released by a cell or group of cells into the blood for transport (mainly long-distance) to target cells

from endocrine cells or cytokines from any cell

can be neurohormones (chemicals released by neurons into the blood for action at distant targets)

COMES FROM hypothalamus (pituitary glands), pineal gland, thyroid gland, parathyroid gland, thymus, pancreas, adrenal glands, ovaries/testes

• can change enzyme activity

• change membrane transport

• change gene expression

more functions:

• exerts concentrations at low concentrations (10^-9 M to 10^-12 M)

• can act as a ligand (signal molecule) w/ target cell receptors in one location and paracrine/autocrine signals at another

• effects may vary in different cells/areas/effects

• long-term duration, short term response

Endocrinology

Study of hormones & endocrine system

How can hormones be degraded

into inactive metabolites by enzymes in livers + kidneys or directly in bloodstream/in cell via endocytosis (swallowing destroying)

Ectohormones

signal molecules secreted to external molecules

3 step method of removal of endocrinal organ, replacement, excess of hormone

Secretion

movement of substance inside a cell to external

Pheromones

special ectohormones that act on others to elicit a psych/behavior response

What is considered classic hormones

Hormones discovered via approach come from glands easier to identify remove (pancreas, thyroid, adrenal, pituitary, testes/ovaries) — “discrete endocrine glands”

3 types of hormones

• peptide/protein hormones

• steroid hormones

• amine-acid derived hormones

Peptide/Protein hormones

small link of AA to larger proteins and glycolipids

PRE-PROHORMONE → PROHORMONE → HORMONE (w/ carrier bind)

• soluble in water (half-life in minds) hypophilic

• lipophobic → cant enter target cell

• usually binds w/ surface membrane receptors

Steroid Hormones

derived from cholesterol (SYNTHESIZED @ SMOOTH ER)

made only in adrenal cortex, gonads, skin, placenta

• not stored in secretory vesicles due to LIPOPHILIC + HYDROPHOBIC

• synthesized on demand

• diffuses out of endocrine cell (simple diffusion)

Types of steroid hormones

• Testosterone/Dihydrotestosterone (DHT)

• Estradiol

• Estrone

• Cortisol

• Aldosterone

Primary Action v. Secondary Action in Steroid Hormones

Primary Action… Intracellular + Nucleus Receptors

→ goes directly as transcription factors for new proteins

→ binds to protein carrier, binds to intracellular receptor to go to nucleus

Secondary Action… Cell Surface Receptors

→ bind to cell surface receptors

→ acute, rapid responses

Amine Acid Derived Hormones

derived from single amino acid (mainly tyrosine)

• catacholamines (made by modifying side groups of tyrosine) - lipophobic

dopamine, norepinephrine, epinephrine

NEUROTRANSMITTERS that are synthesized and loaded into synaptic vesicles

-hormones when adrenal glands secreted, acts as neurotransmitters in nervous system

• thyroid hormones (synthesized from tyrosine + iodine atoms) - lipophilic

thyroxine (T4), triiodothyronine (T3)

• Trp tryptophan (melatonin) - lipophobic

pineal gland

Hypothalamus

key control system for body homeostasis and releasing neurohormones such as catecholamine, hypothalamic neurohormones in both anterior & posterior pituitary glands

Posterior pituitary gland

extension of brain, neurohormones made that secrete directly into blood circulation

HORMONES MADE FROM HYPOTHALAMUS and stored when needed, pituitary post is place of release

MAINLY for storage/release site

faster, simple

• oxytocin (milk let down, uterine contract)

• vassopressin (ADH antidiuretic hormone to kidney that concentrates urine + water loss, water balance)

Anterior pituitary gland

Endocrine gland of epithelial origin that secretes both releasing and inhibitory neurohormones (synthesize and secretes own hormones not hypothalamus itself)

CONTROLLED BY HYPOTHALAMUS TO BE SECRETED ON DEMAND AND MADE

Uses portal system

slower, complex

• prolactin

• thyrotropin + thyroid-stimulating hormone (TSH)

• adrenocorticotropin, ACTH

• growth hormone, somatotropin

• gonadotropics (follice-stimulating FSH and luteinizing hormone LH)

What is portal system of anterior pituitary gland?

2 sets of capillaries connected in series by set of small veins (special network of blood vessels connecting to hypothalamus allowing instant synthesis + release) without needing to return to heart, allows small set of hormones to be concentrated

Long loop negative feedback v. Short negative feedback

Long loop

• hormone blocks secretion of entire cascade all the way to hypothalamus and anterior pituitary glands BOTH TERTIARY AND SECONDARY (Thyroid, adrenal cortex, gonads)

Short loop

• hormone blocks secretion of hypothalamus, only tertiary DIRECT ONE STOP block for one response (GH and Prolactin)

Synergism

combo of hormones enhances cell response

Permissive

one hormone can’t fully function well without the other

Antagonistic

two hormones have opposing function; cell response depends on relative ratio

Hypersecretion

excess product or release of hormones in the body; exaggerates hormonal effects mainly caused by tumors

Hyposecretion

not enough hormone secreted, may diminish or remove hormone effects mainly caused by atrophy (cell shrinkage)

effects of hypersecretion/hypo via cortisol

• in adrenal cortex (primary)

HYP: CRH lvl LOW

Ant Pit: ACTH lvl LOW

Cortisol → high

• Pituitary problem (secondary)

HYP: CRH lvl low

Ant Pit: ACTH lvl high

Cortisol → high

• in hypothalamic (tertiary)

HYP: CRH high

Ant Pit: ACTH high

Cortisol → high

DEPENDS ON TERTIARY LEVEL