Human Anatomy and Physiology: Biology 211 class Flashcards
Endocrine system function
Acts with the nervous system to coordinate body activity. Influence metabolic activities by means of hormones transported in blood. response occurs slowly, but last longer.
endocrine system includes
Pineal gland, hypothalamus, pituitary gland, thyroid gland, parathyroid, thymus, adrenal gland, pancreas, gonads. other tissues as well
Hormones...a chemical messenger
long distance chemical signals that travel in the blood or lymph. Reproduction, growth and development, body defenses. cellular metabolism, chemical balance of blood.
Autocrines..a chemical messenger
chemicals that exert effects on the same cells that secrete them. Prostaglandins, affect smooth muscle contraction
Paracrines..a chemical messenger
Locally acting chemicals that affect other cells includes Histamine, serotonin.
The hypothalamus has
both neural and endocrine functions
receive impulses and release hormones
Two main classes of hormones
Amino acid-based and steroids
amino acid-based hormones
amines, thyroxine, peptides and proteins
synthesized from cholesterol.
gonadal and adrenocortical hormones
Hormones act on _______and alter activity
List how hormones alter activity?
alter plasma membrane permeability
stimulate synthesis of proteins
activate or deactivate enzyme systems
induce secretory activity
Mechanisms of Hormone activity
Water soluble hormones
all amino acid based hormones except thyroid hormone. Cannot enter the target cell
act on plasma membrane receptors
coupled by G proteins to intracellular second messengers.
Lipid-soluble hormones (steroid and thyroid)
act on intracellular receptors that directly activate genes
Steps in hormone process
Hormone first messenger binds to receptor
receptor activates G (G2) protein
G protein activates adenylate cyclase.
Adenylate cyclase converts ATP to cAMP (2nd messenger)
Steps in the lipid process of hormone action
- Steroid hormone diffuses through the plasma membrane and binds in the intracellular receptor.
- receptor hormone complex enters the nucleus
- receptor binds to a specific dna region
- binding initiates transcription of the gene to mRNA
- mRNA directs protein synthesis
Target cells must have ________ to which hormone binds
ACTH (adrenocorticotropic hormone) receptors are only found on certain cells of the
Thyroxine receptors are found in nearly _____cells of the body
Target cell activation depends on three factors
number of receptors
affinity of binding
hormones influence the number of their receptors on the membrane through
up regulation and down regulation
target cells form more receptors in response to the hormone. Persistent low hormone levels
target cells lose receptors in response to the hormone. prolonged high hormone levels.
Hormones circulate in the blood either free or bound.
steroids and thyroid hormone( lipid soluble) are attached to plasma proteins. All others circulate without carriers.
The concentration of (blood level) of a circulation hormone reflects
speed of inactivation and removal from the body
rate of release.