I.
Endocrine glands – general
A. Endocrine vs. exocrine
- exocrine – sweat, oil, mucus, digestive
glands
- endocrine – “ductless” - secretions are
hormones that travel directly into the blood
stream – body regulators
B. Nervous and endocrine systems – work together
to coordinate functioning of all systems
- nervous system releases chemical
messengers called neurotransmitters
which cause nerve impulse – milliseconds
- endocrine system – releases chemical
messengers called hormones which alter
physiological activity of all tissues – several
hours (pg 307)
C. Hormonal effects
1. regulate chemical composition and
volume of extracellular fluid
2. regulate metabolism and energy balance
3. regulate contraction of smooth and
cardiac muscle – secretion of exocrine
glands
4.maintain homeostasis despite infection,
trauma, stress, dehydration, starvation,
hemorrhage, and temperature change
5. regulates immune system
6.regulates smooth and sequencial growth
7. contribute to reproduction, gamete
formation, fertilization, nourishment
(fetal & newborn)
D.Chemistry of hormones
1. steroids – derived form cholesterol and
are lipid soluable
2. biogenic amines – simplest molecule –
produced from amino acids and are H20
soluble
3. proteins and peptide – chains of amino
acids (3 – 200) – H20 soluable
4.eicosanoids – derived from fatty acids
II. Hormonal Action – determined by body
requirements at any time
A. Overview – hormone producing cells are sent
information from sensing and signaling that
regulates amount and duration of hormone
release
- hormones only affect target cells
- cells have receptors (protein) that are
specific
B. Receptors – selective response
- only target cells are influenced by
hormones
- different kinds of cells may have same
receptors but will respond differently
EX. Ca+2 is too low the parathyroid will trigger
the bones to release Ca, the GI tract will
absorb Ca, and the kidneys will reabsorb Ca
from the urine
C. Messengers
- 1st messengers - H2o soluble hormones that
bring messages to the cell – cannot
penetrate the phospholipid layer of the
plasma membrane
- 2nd messengers - take messages into the cell
- cyclic AMP(from ATP) – activates enzymes
called protein kinases
D.Feedback control – regulation is necessary to
prevent the over production or the under
production of hormones
- negative feedback control
1. blood chemical levels -Ca
- insulin and glucagon
2. nerve impulses – hormone is released by
a direct impulse to an endocrine gland
3. hypothalamus secretions – chemical
secretions by the hypothalamus controls
the negative feedback system –
a. releasing hormones – cause a release
b. inhibiting hormones – prevent release