Chapter 17 Flashcards
what is the Endocrine System (simple)
Hormones travel via bloodstream
Autocrine
Secreted by cells in a local area. influences the activity of the same cell from which it was secreted.
eicosanoids (prostaglandins, thromboxanes, prostacyclins, leukotrienes)
Paracrine
produced by a wide variety of tissues and secreted into extracellular fluid; has a localized effect on other tissues.
somatostatin, histamine, eicosanoids.
Neurotransmitters
Produced by neurons; secreted into a synaptic cleft by presynaptic terminals; travels short distances; influences postsynaptic cells.
Acetylcholine, epinephrine
Endocrine response is secreted into the
Secreted into the blood by specialized cells; travels some distance to target specific tissues
Characteristics of the Endocrine System
Glands that secrete chemical messengers (hormones) into circulatory system (blood). Regulates Activities (growth & reproduction) of body structures.
Hormone Characteristics
- produced in small quantities
- secreted int intercellular space (outside of cell)
- transported some distance in circulatory system
- acts on target tissue elsewhere in the body (must posse receptors)
Ligands
General term for chemical signals
Similarities of Nervous and Endocrine System
- Both systems associated with the brain. (hypothalamus - to control the pituitary gland. Epithalamus (pineal gland))
- may use same chemical messenger as neurotransmitter and hormone. (epinephrine)
- two systems are cooperative.
Differences of Nervous & Endocrine System
- mode of transport : nervous system uses axon of neurons via synapsis. Endocrine system uses blood stream
- speed of response: Nervous system - instant/milliseconds. Endocrine system: Delayed/seconds.
3.Duration of responses:
Nervous system - milliseconds/seconds. Endocrine system: mintues/days.
Duration of response nervous vs. endocrine system
The target cell/tissue produces a longer resonse with the endocrine system compared to the nervous system
Lipid Soluble Hormones
absorbed/disolved by fat. hydrophobic (hates water).
Lipid soluble hormones have a longer half-life compared to water soluble hormones
Water Soluble hormones
Absorbed/disolved by water - water loving/Hydrophilic.
water soluble hormones have a shorter half-life compared to lipid soluble hormones
Lipid Soluble Vitamins
Vitamin A, D, E, K - can lead to toxicity if taken too much because they are harder to get rid of (stored in fats)
Water soluble vitamins taken too much will lead to ___
if taken too much, kidneys can excrete excessive levels of water soluble vitamins
what binding protein do water-soluble hormones need?
Water soluble hormones don’t need a binding protein when traveling in blood
Patterns of Hormone Secretion
- chronic hormone regulation - maitenance of relatively constant concentrations of hormone. (thyroid hormone regulates basal metabolism)
- Acute hormone regulation - epinephrine in response to stress
- episodic (cyclic) hormone regulation - female reproductive system
Control of Hormone Secretion PTH
PTH Parathyroid hormone > stimulates osteoclasts (catastrophe bc they take calcium away from the bone and if stimulated too much may lead to osteoperiosis) > bone calcium levels decrease > blood calcium levels increase
Control of Hormone Secretion Calcitonin
Calcitonin does oposite of PTH : secretion of calcitonin leads to stimulation of osteoblasts (bone building cells) causing an increase of calcium being added to the bone causing a decrease of blood calcium levels
Negative Feedback
Ultimately turns off system. likes to maintain homeostasis (normal baseline, normal range, stable environment).
Positive Feedback
It is a system that further deviates from normal baseline or homeostasis.
Down-Regulation (Endocytosis)
takes away receptors on the cell membrane and decreases the cells response.
Up-Regulation
adding more receptors to the cell membrane: exocytosis: increases cell response
Overview of Hormone receptors and mechanisms of action Lipid Soluble and small molecules
Hormone
nuclear receptors
activates genes
synthesizes new proteins or enzymes
cell responds
Hormone receptors and mechanisms of actions for Water soluble and large molecules
Membrane bound receptors
receptors after the activity of G proteins
Open of close Ion channels and activates existing enzymes
cell responds
OR
Membrane bound receptors
Receptors alter the activity of intracellular enzymes
activate existing enzymes
cell responds
Hormone examples for Lipid Soluble
(receptor type : nuclear)
Steroid hormone testosterone estrogen progesterone aldosterone cortisol thyroid hormone vitamin D
Hormone examples for water-soluble
(receptor type: membrane bound)
luteinizing hormone follicle-stimulating hormone thyroid stimulating hormone adrenocorticotropic hormone glucagon oxytocin antidiuretic hormone calcitonin parathyroid hormone epinephrine insulin growth hormone prolactin
