Chapter 16 part 1) Endocrine system Flashcards
1
Q
Endocrine System Overview
A
- Acts with nervous system to coordinate and integrate activity of body cells.
- Influences metabolic (cell) activities via hormones in blood
- Produces a slower but longer lasting effect than the nervous system
- Endorcrinology) study of hormones and endocrine organs.
- Controls and Regulates
- Reproduction
- Growth and Development
- Mantienace of electrolyte, water, and nutrient balance in the blood.
- Regulation of cellular metabolism and energy balance
- Mobilization of body defenses.
2
Q
Endocrine vs Exocrine glands
A
- Exocrine Glands
- produce nonhormonal substances (slaiva, sweat)
- Secrete on membrane suface (ex; skin, tounge)
- Endocrine Glands
- Produce horomones
- Lack ducts; secrete horomones into surrounding tissue.
3
Q
Endocrine Glands (types)
A
- Pituitary, thyroid, parathyroid, adrenal, and pineal glands are all endocrine glands
- Hypothalamus) Nueroendocrine organ
- has both nural and endocrine functions
- Pancreas, Gonads, and Placenta
- have exocrine and endocrine functions
- Adipose cells, thymus, cells in small intestine, stomach, kidneys and heat
- all produce horomones
4
Q
Chemical Messangers
A
- Horomones) Long distance chemical signals
- travel in blood or lymph
- Autocrines) Exert effects on same cells that release them
- Paracrines) Locally acting chemicals that affect cells that surround the secreating cell.
- Autocrines and Paracrines are local chemical messangers that are not considered part of the endocrine system.
5
Q
Chemisty of a Horomone
A
Two Types
- Amino acid-based hormones
- Amino acid derivatives, peptides, and proteins
- Cannot pass through plasma membrane
- Steriods
- Synthesized from cholesteral
- Gonaldal and adrenocortical hormones
- can pass trhorugh plasma membrane
- Target Cells) Tissues with reponsers for a specific hormone
- Hormones circulate systemically but only target cells are affected.
- Horomone action on Target cells may be to
- Alter plasma membrane permiability/ ion channels
- Stimulate synthesis or enymes/ protiens
- Activate/ deactivate enzymes
- induce secretory activity
- stimulate mitosis
6
Q
Mechanisms of Hormone Action
A
- Water-siluable hormones (all amino acid-based hormones except thyroid hormones)
- Act on plasma membrane receptors
- Act via G protien second messangers (do not enter cell)
- Lipid-Soluable hormones (steriod and thyroid hormones)
- Act on intracellular receptors that directly activate genes
- can enter the cell
7
Q
Cyclic AMP (second messanger system)
A
- cAMP signiling mechanism
- Hormone (first messanger) binds to receptor
- Receptor activates a G protien
- G protien activates/ inhibits adenylate cyclase
- Adenylate Cyclase Converts ATP to cAMP (secnd messanger)
- cAMP activated protien kinases that phosphorylaye protiens (add a phospate too)
- Phosphorylation activates some protiens and inhibits other
- can affect a variety of proesses in the target cell
- cAMP is rapidly degraded by enzyme phosphodiesterase
- Cascaded have amplification effect.
8
Q
PIP2- calcium signaling mechanism (second messanger system)
A
- PIP2-calcium signaling mechanism
- Hormone-activated G protien releases phospholipase C
- Phospholipase C splits membrane protein called PIP2 (Phosphatidyle Inositol Biphosphate) into two second messangers
- Diaclyglycerol (DAG) activated protien kinases
- Inositol Triposphate (IP3) causes Ca2+ release from intracelluar stores. Ca2+ acts as another messanger
- Ca2+ release alters enzyme activity and channles, or binds to regulatory protien calmodulin.
- Calcium boynd calmodulin always amplifys cellular response.
9
Q
Other Signaling Mechanisms
A
- Cycilic guanosine monophospate (cGMP) is a second messanger for some homones.
- Some work without second messagers
- Ex) Insulin
10
Q
Intracellular Receptors and Direct Gene Activation
A
- Steroid hormones and thyroid hormone can diffuse into target cells and bind with intracellular receptors
- Receptor-hormone complex enters nucleus and bind to specific region of DNA
- Help initiate DNA transcription to produce mRNA
- mRNA is then translated into specific protein
- Proteins synthesized have various functions
- Examples: metabolic activities, structural purposes, or exported from cell
11
Q
Control of hormone release
A
- Hormone levels in the blood are controlled by negative feeback systems
- Increased hormone effect on target organs can cause decreased hormone release.
- Levels stay withing a narrow, desirable range
- Endocrine glands stimulated to syntesise and release hormones in response to
- Humoral Stimuli) Changling levels of ions and nutrients
- ex) more Ca2+ in blood stimulates parathyroid hormone
- Nural stimili) Nerve fibers stimulare hormone release
- ex) sympathetic nervous system activating
- Horomonal Stimuli) Hormones stimulate other endocrine organs to release their hormones
- Humoral Stimuli) Changling levels of ions and nutrients
12
Q
Nervous System modulation
A
- Nervous system can make adjuctments to hormone levels when needed
- Can modify stimulation or inhibitionof endocrine glands
- The nervous system can overide normal endocrine system functioning
- EX) hypothalamus and sympathetic nervous system overide insulin to allow blood glucose levels to raise in “fight or Flight”
13
Q
Terget Cell Specificty
A
- Target cells must have specific receptors for the hormone to bind to
- Target cell regulation depends on three facotrs
- Blood levels of hormone
- Relative number of receptors
- Affinity of bining between recptor and hormone.
- Ammount of hormone can influence the number of receptors for that hormone
- Up-regulation) more target cells in response to low hormone levels
- Down-regulation) target cells lose receptors in response to high hormone levels.
14
Q
Hormones in the Blood
A
- Hormones circulate in blood either free or bound
- Steroids and Thyroid homone are attached to plasma membrnes
- all others are free
- Concentration of circulating hrormones relates
- rate of release
- speed of removal in the body
- Hormones can be removed from the blood by
- Degrading Enzymes, kindeys, or the liver
- Half-life. Time required for hormone’s blood level to decrease in half. (half a minuite to a week)
- Onset of Hormonse activities
- hormones take diffrent times to activate a receptor
- Duration of a response is usually limited
15
Q
Interations of Hormones at Target Cells
A
- Permissivensess) one hormone cannot exert its effct without another hormone present
- Reproducive and thyroid hormone are nessecary for the timly development of reproductive structures.
- Synergism) more than onre hormone produces the same effect on a target cell
- causes amplification
- ex) glucagon and epinephrine both cause liver to release glucose
- Antoganism) One or more homrones apposed the action of another hormone
- EX) Example: insulin, and glucagon: Insulin lowers blood glucose levels, is antagonized by glucagon, which raises blood glucose levels.
