BIOL 254 Anatomy and Physiology
A&P Exam 1 Study Guide
Endocrine System
Cellular communication
● Autocrine → self signaling
● Paracrine → “near” signaling
● Endocrine → bloodstream, distant target cells signaling (slower)
Endocrine system controls:
1. Reproduction
2. Development
3. Blood maintenance
4. Metabolism
5. Body defenses
How hormones communicate with target cells
● Hormones target most cells of the body
● Depends on hormone’s chemical nature and receptor location
● Target cells have to have specific receptors to which the hormone binds
○ Target cell activation depends on:
i. Blood level of the hormone
ii. # of receptors on/in the target cell
iii. Affinity (strength) of binding between receptor and hormone
Water- vs. lipid-soluble hormones
(second messenger systems vs. direct gene activation/intracellular receptors)
i. Water-soluble (polar)
1. Act on plasma membrane receptors (on cell)
2. Via G protein 2nd messengers
a. Ex. cAMP + PIP2-calcium
b. Hormone binds to receptor → activates G protein
→ activates etc.
3. Can not enter the cell
a. Ex. amino-acid hormones
ii. Lipid-soluble (nonpolar)
1. Act on intracellular receptors (in cell)
2. Directly activate genes
, a. Receptor-hormone complex enters the nucleus →
binds to DNA → mRNA → spec. protein
3. Can enter the cell
a. Ex. steroid and thyroid hormones
Types of stimuli that trigger hormone release
1. Endocrine gland stimuli
a. Humoral stimuli → hormone release caused by altered levels of certain
ions or nutrients
b. Neural stimuli → hormone release caused by neural input
c. Hormonal stimuli → hormone release caused by another hormone
(tropic hormone)
Feedback mechanisms
1. Negative feedback → reduce the output (back to stable state)
2. Positive feedback → increase the output (amplified to happen quicker)
Hypothalamus
● The Hypothalamus controls release of hormones from pituitary
● Connected to pituitary gland via infundibulum
● Neurosecretory cells → synthesize ADH + oxytocin → stored in PP
○ Transported to posterior pituitary (PP) and stored for later use
● Secretes releasing (stimulating) and inhibiting hormones → anterior
pituitary (AP)
b. Hypothalamus-Pituitary-Target Gland axis
A&P Exam 1 Study Guide
Endocrine System
Cellular communication
● Autocrine → self signaling
● Paracrine → “near” signaling
● Endocrine → bloodstream, distant target cells signaling (slower)
Endocrine system controls:
1. Reproduction
2. Development
3. Blood maintenance
4. Metabolism
5. Body defenses
How hormones communicate with target cells
● Hormones target most cells of the body
● Depends on hormone’s chemical nature and receptor location
● Target cells have to have specific receptors to which the hormone binds
○ Target cell activation depends on:
i. Blood level of the hormone
ii. # of receptors on/in the target cell
iii. Affinity (strength) of binding between receptor and hormone
Water- vs. lipid-soluble hormones
(second messenger systems vs. direct gene activation/intracellular receptors)
i. Water-soluble (polar)
1. Act on plasma membrane receptors (on cell)
2. Via G protein 2nd messengers
a. Ex. cAMP + PIP2-calcium
b. Hormone binds to receptor → activates G protein
→ activates etc.
3. Can not enter the cell
a. Ex. amino-acid hormones
ii. Lipid-soluble (nonpolar)
1. Act on intracellular receptors (in cell)
2. Directly activate genes
, a. Receptor-hormone complex enters the nucleus →
binds to DNA → mRNA → spec. protein
3. Can enter the cell
a. Ex. steroid and thyroid hormones
Types of stimuli that trigger hormone release
1. Endocrine gland stimuli
a. Humoral stimuli → hormone release caused by altered levels of certain
ions or nutrients
b. Neural stimuli → hormone release caused by neural input
c. Hormonal stimuli → hormone release caused by another hormone
(tropic hormone)
Feedback mechanisms
1. Negative feedback → reduce the output (back to stable state)
2. Positive feedback → increase the output (amplified to happen quicker)
Hypothalamus
● The Hypothalamus controls release of hormones from pituitary
● Connected to pituitary gland via infundibulum
● Neurosecretory cells → synthesize ADH + oxytocin → stored in PP
○ Transported to posterior pituitary (PP) and stored for later use
● Secretes releasing (stimulating) and inhibiting hormones → anterior
pituitary (AP)
b. Hypothalamus-Pituitary-Target Gland axis
