15CHAPTER 17: THE ENDOCRINE SYSTEM Flashcards
Why must cells be able to communicate and integrate their activities with each other?
gap junction,
To maintain body homeostasis
What are the 4 methods of cellular communication?
Gap junctions, neurotransmitters, paracrine signals, and hormones
Where are gap junctions present are and what do they do?
Present in some neurons, cardiac and smooth muscle
Allow direct communication via signalling molecules
What doe neurotransmitters secreted by and what do they do?
Secreted by neurons
Act less directly than gap junctions, release neurotransmitters on postsynaptic neurons that have the correct receptor
What are paracrine signals secreted into?
Secreted into tissue fluids by a cell and affect nearby cells in same tissue
What are hormones?
Chemical messengers secreted by endocrine glands (and others) into the bloodstream
What does the endocrine system include?
Glands and organs (brain, heart, small intestine) that secrete hormones into the blood
How does communication occur within the nervous system and the endocrine system?
NS- neurotransmitter
ES- hormones
Where are chemicals released into from the Nervous system and the endocrine system?
NS- into synaptic cleft ES- into blood
What are the effects of the NS and the ES?
NS-short acting ES- longer acting
What is the Speed of reactions withing the NS and ES?
NS- fast – seconds , ES- slow – minutes to days
What does the hypothalamus (HYP) form?
Floor and walls of the 3rd ventricle.
What is the pituitary gland composed of?
Two structures:
- Posterior pituitary (neurohypophysis)
- Anterior pituitary (adenohypophysis)
What do the hormones of the hypothalamus do?
6 stimulate or inhibit anterior pituitary
2 secrete by way of posterior pituitary
Which hormones are the posterior pituitary (PP) hormones?
ADH (antidiuretic hormone) and OT (oxytocin)
What is the action of ADH (antidiuretic hormone)?
Water reabsorption
What is the action of OT (oxytocin)?
Contraction of uterus (childbirth)
Contraction of mammary gland cells (milk secretion)
What are the anterior pituitary hormones?
FSH (follicle-stimulating H.), LH (luteinizing H.), TSH (thyroid-stimulating H.), ACTH (adrenocorticotropic H.), PRL (prolactin), GH (growth H.)
What are the 3 chemical classes of hormones?
Steroids, peptides, monoamines
What are steroids synthesized from?
Cholesterol
Examples: sex H., vit D, corticosteroids, aldosterone, estrogen
What are peptides synthesized from?
Amino acids
Ex. Oxytocin, ADH, insulin
What are monoamines synthesized from?
Amino acids Tryptophan (melatonin) and Tyrosine (EPI, NE)
What kind of solution is blood plasma?
Aqueous solution (mostly water)
What is the difference is life length between hydrophobic hormones and hydrophilic hormones?
hydrophobic hormones- prolonged lives due to being bound to transport proteins hydrophilic hormones- short life due to unbound (free) travelling
Where are hormone receptors found?
the plasma membranes, on the mitochondria and other organelles, and in the nuclei of target cells
What do steroids bind to?
nuclear receptors
What do monoamines bind to?
receptors in nucleus, mitochondria, and ribosomes
What do peptides bind to?
Plasma membrane receptors which activate second messengers (cAMP)
What is enzyme amplification?
A very small hormonal stimulus can cause a very large metabolic effect
What is Metabolic clearance rate (MCR)?
rate at which hormones are removed
