Endocrine System Flashcards
What is cell communication?
The endocrine system uses a chemical method of communicating where hormones are released into the bloodstream and travels to target cells. Works with nervous system to maintain homeostasis. Within bloodstream, expression of target receptors, long-lasting (dependent on half-life and metabolic rate) often diffuse.
Components of the endocrine system?
Made up of endocrine glands and the hormones they secrete.
Major organs: Hypothalamus, pituitary, thyroid, parathyroid, pancreas, adrenal, ovaries, testes
Accessory organs: Brain, liver, heart, thymus, gastrointestinal, mucosa, placenta
Functions of the Endocrine system
Growth and development, fluid and electrolyte balance (water retention), muscle development and strength, blood glucose control (sugar), responding to stress, temperature regulation, fuel metabolism, moods and emotions, love and bonding, appetite and fuel intake, sleep and wake cycles, pregnancy, reproduction, lactation, puberty
Hormones and their target cells:
Chemical messengers that transfer information and instructions from one set of cells to another. Released in small amounts from the endocrine glands and is transported in the bloodstream to target organs or other cells. A target cell is a receptor that responds to the presence of a specific hormone and may respond to more than one hormone
Endocrine glands and their hormones:
Pineal gland (brain) releases melatonin. Hypothalamus stimulates and inhibits secretion from the anterior and pituitary and controls the direct release of hormones form posterior pituitary gland.
thyroid releases T3 and T4 (regulation of metabolic rate)
Parathyroid releases parathyroid hormone (regulation of calcium in body fluids)
Adrenal glands release - cortisol, aldosterone, adrenaline,
Pancreas releases insulin and glucagon
Testes release testosterone
Ovaries
Chemical classes of hormones
Water soluble: Cannot diffuse through the plasma membrane (amines, peptide hormones)
Lipid soluble: Can diffuse through the plasma membrane (steroid hormone) can enter the cell
What are water soluble hormones?
Circulate in the blood plasma in a free form. Free hormones diffuse out of the blood when it gets to a target cell and into the extracellular fluid surrounding the target cell it binds to a receptor (outside the cell)
Target cell receptor location: Surface of the plasma membrane
Hormone action: Activates a 2nd messenger system in the cytosol to trigger a response in rarget cells. Binding of this hormone to a receptor causes activation of something else and this thing in the chain is called a 2nd messenger which then goes out and does their job to change the action in a protein (tells it to go do something)
What are lipid-soluble hormones?
Travel in blood plasma bound to transport proteins, however a small percentage are free unbound hormones. A free hormone diffuses out of the blood and into the extracellular fluid
Target cell receptor location: in the cytosol or nucleus
Hormone action: activates genes to trigger a response in target cells, directly effects DNA and tells the nucleus to make proteins.
What is the difference between a water soluble and lipid soluble hormone?
Water tells the 2nd messenger to activate a protein, whereas the lipid tells it to make a protein.
Activating a second messenger is quicker than altering gene expression but lipid has a longer half-life as it takes longer to do things
Hypothalamus and Pituitary gland
Location:
Hypothalamus is a region of the brain, anterior to the superior brainstem. It is the coordination center for the endocrine system and controls activity of the pituitary gland
Pituitary gland is connected inferiorly to the hypothalamus by the posterior component, secretes hormones that regulate many body functions
Anatomy of the pituitary gland:
The posterior pituitary is a direct extension of the hypothalamus. Communication occurs via hormones sent directly from hypothalamus through neurosecretory cells ( nerves that package a hormone into vesicles, sends down an axon and is acted upon)
Anterior pituitary is attached to the posterior pituitary, communication occurs through releasing/ inhibiting hormones sent from the hypothalamus, through the blood vessel system (hypothalamic-hypophyseal portal system)
Hypothalamus sends hormones to a capillary bed or blood network
Posterior Pituitary:
Hormones:
Neurohormones (came from neurosecretory cells in the hypothalamus) oxytocin and antidiuretic (water retention at kidney level) ADH are synthesized in the cell bodies of the neurons located in the hypothalamus
Vesicles containing the hormone made in soma are transported down the axon to the posterior pituitary
Anterior pituitary:
Hormones
Short axon neurons in they hypothalamus synthesize hypophysiotropic hormones and release them into the portal system
Portal system carry hormones to anterior pituitary, endocrine cells are controlled by the hypophysiotropic hormones and they secrete anterior pituitary hormones into systemic blood
if we want to release thyroid stimulating hormone we need a releasing hormone from they hypothalamus (TRH) which stimulates TSH
The Thyroid Gland and Thyroid Hormone
The thyroid is an endocrine gland in the neck region, inferior to the larynx made up of thyroid follicles. Plays a major role in metabolism, growth and development. Thyroid hormones T3 and T4 are stored in the thyroid gland and rely on synthesis and consumption of iodine
