U3 Concept 3 The Endocrine System
Hormone
chemical messengers secreted by cells into extracellular fluids
• Travel through blood to regulate functions in our cells
Exocrine
externally secreting; release nonhormonal substances, like sweat and saliva, through ducts to the body's
surface...
hormone release caused by altered levels of critical ions or nutrients
- Simplest endocrine control
Neural stimuli
hormone release caused by neural input
Hormonal stimuli
hormone release caused by another hormone
- Promotes rhythmic hormone release
Permissiveness
when a hormone can't do its job fully without another hormone present
• Ex. Reproductive system hormones can't do their jobs unless the thyroid hormone has stimulated
reproductive development in a timely manner.
Synergism
when more than one hormone produces the same effects at the target cell an amplified combined effect
• Ex. Both glucagon and epinephrine cause the liver to release glucose to the blood. When acting at the
same time on the same cell, they can release way more glucose.
Antagonism
when one hormone opposes the action of another
• Ex. Insulin lowers blood glucose levels and glucagon raises them.
List the overall function of the endocrine system and examples of the different bodily activities it
regulates.
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