Hormones Flashcards
(104 cards)
A chemical messenger released in one tissue and transported via the bloodstream to alter activities of other cells in a different tissue is called
Hormone
Communication between cells using gap junctions. Occurs between two cells of the same type and close together Ex cardiac muscle
Direct communication
One cell releases a chemical into extra cellular fluid surrounding another cell. This tells the cell what is going on next door so that they can coordinate their activities at the local level
Paracrine communication
Most cells release paracrine factors but specialized ones produce hormones. Every hormone has a target cell. These are cells with very specific receptors needed to bind and read the hormone when it arrives.
This makes it so that the right hormone affects the right parts of the body. You don’t want the thyroid hormone binding to the ovaries. The hormones fit into their target cells like a lock and key or puzzle pieces.
Endocrine cells releases chemicals hormones into the bloodstream where messages will travel to other parts of the body and alters metabolic activity of many organs
Endocrine communication
Ideal for crisis management. Neurons release neurotransmitters at a synapse. Leads to action potential that propagated along axons. Allows for high speed messages to reach specific locations
Synaptic communication
Once hormone reach target cells they change the activity of the target cells by changing the types, amounts, or activity of the enzymes and proteins using transcription or translation or turn an existing enzyme or membrane off or on.
A hormone can easily change the structure or chemical properties of the target cell. One hormone can change the metabolism of multiple tissues or organs at the same time.
Hormones can be divided into 3 classes on the basis of their chemical structure
Amino acid derivative
Lipid derivative
Peptide hormones
Very small
Made from amino acid tyrosine and tryptophan [ larger of the two].
Tyrosine base ex thyroid hormone
Catecholamines group( epinephrine, norepinephrine, dopamine).
Tryptophan based ex: melatonin. Serotonin
Amino acid derivative
This hormone group has two classes: eicosanoids; derived from arachidonic acid and steroid hormones derived from cholesterol.
Eicosanoids ex: leukotrienes and prostaglandins.
Steroid hormones ex: androgen, estrogen, progesterone, corticosteroids, calcitrol.
Lipid derivatives
Hydrophobic
Bound specific transporters
This hormone group is made of chains of amino acids
Made of glycoproteins ( TSH, LH, FSH).
Made of short polypeptides ( ADH, OXT)
Small proteins ( insulin, growth hormone, prolactin)
Peptide hormones
The receptors for catecholamines, peptide hormones, and eicosanoids are in the plasma membrane of their target cells.
Catecholamines and peptide hormones are not lipid soluble so they can’t pass through the Lipid bilayer of the plasma membrane they must bind extracellularly.
Eicosanoids are lipid soluble so they pass across the plasma membrane and bind to receptors on the inner surface of the plasma membrane.
Communication between the hormone and its target cell uses first and second messengers. The first messenger is the hormone that binds to the membrane on the outside. A second messenger is a helper molecule that appears due to the meeting of the first messenger and receptor.
Important second messengers are cyclic AMP (cAMP) which is from ATP, cyclic GTP (cGTP) derivative of GTP, and calcium). The link between the first and second messenger is called G protein.
A G protein is an enzyme complex attached to a membrane receptor. G proteins become active when a hormone binds to its receptor at the membrane surface.
When G protein is activated it will activate the enzyme adenylate cyclase which will convert ATP to cAMP. Then cAMP will act as second messenger by activating a kinase which will attach a high energy phosphate group to another molecule by the process known as phosphorylation. This open ion channels in the cells. The cytoplasm contains the enzyme phosphodiesterase ( PDE) which inactivates cAMP by converting it to AMP.
Two regulatory hormones of the anterior pituitary
Inhibiting and releasing hormones
Stimulates creation and secretion of hormones at anterior lobe
Releasing hormones
Prevents creation and secretions of hormones at the anterior pituitary
Inhibiting hormones
Endocrine gland organs
Hypothalamus Pineal body
Pituitary Ovaries
Thyroid Testes
Parathyroid
Adrenals
The hormones of the anterior lobe are called tropic meaning turning on . They switch on other endocrine glands or supports the work of other organs.
Thyroid stimulating hormone or TSH triggers the thyroid gland itself and causes it to secrete thyroid hormone
Adrenocorticotropic hormone or ACTH
Stimulate the release of steroid hormones by the adrenal gland, causing it to produce glucocorticoids which are hormones that affect glucose metabolism.
Regulates the activity of the gonads ( testes and ovaries). They stimulate the production of reproductive cells and hormones.
Gonadotropins
2 gonadotropins
FSH follicle stimulating hormone and LH luteinizing hormone
Promotes follicle development in the ovaries and along with LH will stimulate the secretion of estrogen. In males will help with sperm production.
FSH follicle stimulating hormone
