Chapter 16- The Endocrine System Flashcards
Hormones
Long distance (not affecting the cells that are in the same tissue they are inchemical messengers that cause a change in metabolic activity of a cell
long lasting
hormone control
Reproduction
Growth and development
Immune system activation
Maintenance of various blood components (glucose, electrolytes, water, etc.)
autocrines and paractines
short-sdistance chemical messengers
more localized infections
autocrine
a chemical message that affects the same cell that produces the message
paracrine
a chemical message that is produced by one cell but affects a different cell
same tissue but different cell
Major classifications of hormones
- amino acid-based hormones- water soluble transports a protein from point a to point b
- steroid hormones- synthesized from cholesterol
lipid soluble
the only steroid hormones in the body are gonadal hormones and adrenocortical
Hormone Actions
- Altering plasma membrane permeability or membrane potential (epinephrine)
- stimulates the synthesis of enzymes/proteins in the cell
- Activates and deactivates enzymes
- induces secratory activity
- stimulates mitosis
Target cells
affected by hormones that have the appropriate receptor
2 mechanisms of hormones
- secondary messenger system through g protein (extremely efficient)
- intracellular system- hormone enters cell and binds to intracellular receptors and DNA transcription occurs
stimulus mechanisms
- humoral stimuli- change blood levels of critical ion and nutritns
- neural stimuli- nerve fibers stimulate hormone release
- hormonal stimuli- hormone released in response to other hormones
hormone concentration in blood depends on
- how fast its released from the organ
- how fast it is broken down (hormones are removed by kidneys and liver) (water soluble hormones have shortest half life)
Hormone release
negative feedback mechanism
activation of a cell depends on
- blood levels of a hormone (more blood = more binding)
- number of receptors for specific hormone on/in a cell (more receptors = more binding)
- affinity of receptor to the hormone (easier binding, the higher the effect)
up-regulation
increase receptor number in response to low hormone levels
down-regulation
decrease receptor number in response to high hormone levels (safety backup mechanism)
Permissiveness
one horone cannot have funn effect without binding of a second specific hormone
synergism
2 or more horones with similar effects bind to target cell and amplification occurs
antagoism
one hormone opposes the effect of another and they will compete
Pituitary gland
anterior and posterior pituitary