Endocrine SHIZZLE Flashcards
Endocrine vs Exocrine
Endocrine: ductless, hormones into bloodstream, hormones only act on target cells
Exocrine: secrete externally via ducts or tubes, deliver product directly to a specific site
Paracrine vs. Autocrine Secretion
Paracrine: affect nearby cells via messenger molecule
Autocrine: affect cells that secrete the substance
Nervous System vs. Endocrine System
Cells: Neurons vs Glandular epithelium
Chemical signal: Neurotransmitter vs. Hormone
Specific action: Receptors on postsynaptic cell, receptors on target cell
Speed of onset: seconds, seconds to hours
Duration of action: very brief, brief or even days
Endocrine Chemical Communication
- Endocrine system is precise, in that only target cells can respond to a specific hormone
- Target cells contain particular receptors for the hormone; these receptors are not present on other cells
Steroid Hormone General Information
- lipids containing aromatic rings
- produced from cholesterol
- ex: sex hormones (testosterone, estrogens) & adrenal cortex hormones (cortisol, aldosterone)
Non-Steroid Hormone General Information
- Amines: Derived from tyrosine (–epinephrine, norepinephrine)
- Proteins: Composed of long chains of amino acids (growth hormone, PTH, GH PRL)
- Peptides: Short chains of amino acids (oxytocin, ADH, TRH, SS)
- Glycoproteins: Carbohydrates joined to proteins (TSH, FSH, LH)
Actions of Hormones
- Deliver messages by binding to specific receptors on/in target cell
- Number of receptors determines strength of response, and can be altered (upregulation and downregulation)
Steroid Hormone Mechanism
1) Steroid hormone crosses into cell membrane due to likeness of cholesterol
2) Combines w/ protein receptor usually found inside the nucleus
3) Hormone-receptor complex binds to DNA and synthesizes mRNA
4) mRNA leaves nucleus and translation leads to synthesize of proteins as instructed by hormone
Non-Steroid Hormone Mechanism
1) Non-steroid hormone binds to specific receptor molecule on cell membrane
2) Activates adenylate cyclase
3) Catalyzes conversion of ATP into cAMP
4) cAMP activates proteins, causing a series of reactions leading to cellular changes associated with hormone’s action
Prostaglandins
- Paracrine substance
- Can activate or inhibit adenylate cyclase > controls cAMp production, therefore alters a cell’s response to hormones
Negative Feedback
-Control mechanism in which rising level of a hormone leads to a decrease in hormone secretion and vice versa
stimulus > receptors > gland > effector > response
3 Methods in which negative feedback controls hormone secretion
1) Tropic Hormones: act on other glands to regulate their secretion
2) Nervous System Control: NS stimulates some glands to secrete hormones via nerve impulses
3) Changes in composition of internal environment: changing levels of specific substances in blood can either inhibit/stimulate secretion of some hormones
Anterior Pituitary Lobe Regulation vs Posterior Pituitary Lobe Regulation
-Anterior Lobe Regulaton:
Hypothalamic releasing hormones are transported through the Hypophyseal Portal System, and stimulate cells of anterior lobe to release hormones
-Posterior Lobe Regulation:
Nerve impulses from the hypothalamus travel through the infundibulum, and stimulate nerve endings in posterior lobe to release hormones
Anterior Pituitary Hormones
Growth hormone (GH) Prolactin (PRL) Thyroid-stimulating hormone (TSH) Adrenocorticotropic hormone (ACTH) Follicle-stimulating hormone (FSH) Luteinizing hormone (LH)
Posterior Pituitary Hormones
Antiduretic Hormone (ADH) Oxytocin (OT)