Types of Regulatory Molecules
Endocrine Glands and Hormones
Paracrine Regulation
Hormones That Enter Cells
Hormones That Do Not Enter Cells
Posterior and Anterior Pituitary Gland
Thyroid and Parathyroid Glands
Adrenal Glands
Other Endocrine Glands
Types of Regulatory Molecules
Hormone – A regulatory chemical secreted into the blood by an endocrine gland, or an organ exhibiting endocrine function.
Target Cells respond to hormone
Neurohormone – A chemical messenger secreted by neuron into the blood rather than the synaptic cleft.
Paracrine - regulatory molecules work without being transmitted by the blood – not endocrine
Pheromone - communication messengers
Hormones secreted by the endocrine glands belong to four chemical categories:
Polypeptides - short chains of amino acids less than 100 amino acids (insulin & ADH)
Glycoproteins- longer than100 A.A. with carbs (FSH and LH)
Amines - Amines – A.A. derived from tyrosine and tryptophan – epinephrine and norepinephrine and melatonin
Steroids - lipids derived from cholesterol
sex steroids - testosterone, estadiol, progesterone, and cortisol – secreted by testes, ovaries, placenta and adrenal cortex
Corticosteroids - adrenal cortex cortisol and aldosterone (regulates glucose and salt balance)
All hormones can be categorized as lipophilic (fat soluble) or hydrophilic (water soluble).
Endocrine Glands and Hormones
Neural and endocrine interactions
Endocrine system also interacts and cooperates with the nervous system to regulate the activities of the other organ systems of the body.
Secretory activity of many endocrine glands controlled by nervous system like
Adrenal medulla, posterior pituitary, and pineal gland
major site for neural regulation is the brain’s regulation of the anterior pituitary by the hypothalmus
However many are not under neural control
Human Endocrine System major glands
Paracrine Regulation
Signaling between cells - Local effect and short-lived occurs in many organs
Regulatory molecules
cytokines - regulate different cells of the immune system
growth factors - promote growth and cell division in specific organs – stimulate cell division at target cells
Paracrine Regulation
Prostaglandins – most diverse group of paracrine regulators
participate in regulation of:
immune system – inflammation, pain and fever
reproductive system – reproductive function ovulation, labor,
digestive system – inhibit gastric secretions, incrfease motility and fluid absorption
respiratory system - blood vessels constriction and dilation in lungs
circulatory system - blood platelets in blood clotting
urinary system - renal blood flow vasodilation increasing urine excretion
Prostaglandin synthesis inhibited by aspirin.
nonsteroidal anti-inflammatory drug
Ibuprofen
Work to inhibit inflammation and pain by inhibiting enzyme necessary to produce prostaglandins – (cyclooxygenase -2)
Hormones That Enter Cells
Lipophilic hormones pass through the target cell’s plasma membrane and bind to intracellular receptor proteins.
hormone receptor complex then binds to specific regions of DNA
activate genes and regulate target cells
Steroid Hormone Action
Hormones That Do Not Enter Cells
Hormones that are too large or too polar to cross plasma membranes include all of the peptide and glycoprotein hormones, as well as catecholamine hormones epinephrine and norepinephrine.
bind to receptor proteins located on the outer surface of the plasma membrane
cyclic AMP second-messenger system
IP3/CA++ second-messenger system
Action of Epinephrine on a Liver Cell
1. Epinephrine is lipophobic and needs to bind to specific receptor proteins on cell surface.
2. Acting through intermediary G proteins the hormone bound receptor activates the enzyme adenenylyl cyclase which converts ATP to cAMP
3. Cyclic AMP performs as a 2ndary messenger and activates protein kinase-A an enzyme that was previously inactive
4. Protein kinase–A phosphorylates and activates the enzyme phosphorylase which catalyses the hydrolysis of glycogen into glucose.
IP3/CA++ Second-Messenger System
1. The hormone epinephrine binds to specific receptor proteins on the cell surface.
2. Acting through G- proteins, the hormone-bound receptor activates the enzyme phospholipase C, which converts membrane phospholipids into inositol triphosphate (IP3)
3. IP3 diffuses thru the cytoplasm and binds to receptors on the endoplasmic reticulum
4. The binding of IP3 to the receptor stimulates the endoplasmic reticulum to release Ca++ into the cytoplasm 5. Some of the released Ca++ binds to the receptor protein called calmodulin
6. The Ca++/Calmodulin complex activates other intracellular proteins – producing the horomone effects
Posterior Pituitary Gland
Pituitary gland hangs by a stalk from the hypothalamus of the brain.
anterior pituitary - appears glandular
posterior pituitary - appears fibrous
Neurons produce antidiuretic hormone (ADH) and oxytocin.
stored in, and released from, the posterior pituitary gland in response to neural stimulation from the hypothalamus
Effects of ADH
Anterior Pituitary Gland
Develops from a pouch of epithelial tissue that pinches off the roof of the embryo’s mouth.
produces the hormones it secretes:
growth hormone (GH) stimulates muscles and bones to grow
adrenocorticotropic hormone (ACTH) regulates glucose homeostasis
thyroid-stimulating hormone (TSH) stimulates the production of thyroxin by thyroid gland
luteinizing hormone (LH) ovulation and testosterone production in testes
follicle-stimulating hormone (FSH) develops ovarian follicle and sperm in males
prolactin (PRL) stimulates mammary glands to produce milk
melanocyte-stimulating hormone (MSH) synthesis and dispersion of melanin pigment
Major Pituitary Gland Hormones
Anterior Pituitary Gland
Hypothalamic control of anterior pituitary gland secretion
Neurons in the hypothalamus secrete releasing hormones and inhibiting hormones into blood capillaries at the base of the hypothalamus.
Each hormone delivered by hypothalamohypophysial portal system regulates secretion or inhibition of a specific anterior pituitary hormone.
Neurons in the hypothalamus secretes hormones that are carried by short blood vessels directly to the ant. Pituitary gland, where they either stimulate or inhibit the secretions of the ant pituitary hormones
Cell body Axons to
primary
capillaries Primary
capillaries Pituitary stalk Posterior pituitary Anterior pituitary Secondary
capillaries Portal
venules
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