Hormone Secretion
Control
Three Kinds of Regulation
Neural Control

Nerve fibers directly stimulate the endocrine organs to release
hormones.

The organs colored in blue are those connected to the nervous
system.

Example: During a fight or flight response nerve impulses travel
through the sympathetic nervous system and stimulate the
adrenal medulla, part of the adrenal glands. These glands
release epinephrine an norepinephrine. Which increases blood
flow, heart rate, dilates pupils. Etc.
Hormonal Control

Glands primarily talk to each other and other organs through
hormones. And this communication is organized into a hierarchy with
each tier telling the next one down in the chain of command what to
do. The hypothalamus is the president like in a business. With vice
presidents and managers below it.

The pituitary is responsible for delegating the work. It takes the
signals from the hypothalamus and then sends out specific hormones
that will communicates to other glands, the managers in this analogy.

The manager glands then send out hormones that will signal to other
parts of the body what needs to be done. All other glands are
considered managers.

The pancreas is a manager level gland but it is more isolated from the
hierarchy.
Negative Feedback

The managers send out signals
with a particular goal in mind,
such as stimulating the heart to
beat faster. Once that job is
done they signal to the
hypothalamus or the pituitary
gland to stop producing the
hormones telling them to
complete this action. This is
called a negative feedback
loop.
Humoral Control

Humoral control of the endocrine system is achieved by monitoring
the levels of different substances in the blood and other body fluids.
If there is an imbalance, corrective actions are taken by the body to
maintain homeostasis.

Example: If blood glucose rises the pancreas releases insulin that
promotes glucose uptake by the body. The result is that blood glucose
then goes down.
When blood glucose is too low the pancreas secretes glucagon. Which
causes the liver to break down glycogen which increases blood
glucose.
Hormones and Homeostasis

The body tends to correct imbalances within itself and always strives to
maintain homeostasis.

Like a thermostat, if the body’s temperature drops the hypothalamus tells the
thyroid to increase metabolism to increase energy output and increase the
body’s temperature. The sympathetic nervous system is stimulated to begin
shivering.

If the body’s temperature is to high then the hypothalamus stimulates the
sympathetic nervous system to sweat.
Critical Thinking

What kind of affects would climbing a very high mountain have on the body?

What kind of things would the body need to do to maintain homeostasis?

How would the endocrine system play into this?
https://www.youtube.com/watch?v=RpadzvO5JGM
Critical Thinking

What kind of affects would climbing a very high mountain have on the body?
Cold, low oxygen, stress.

What kind of things would the body need to do to maintain homeostasis?
Bring up and maintain body temperature, adjust to low oxygen, dealing with
the rigors and danger of the climb.

How would the endocrine system play into this?
Hypothalamus would signal the thyroid to up metabolism. Produce more heat
and energy. Then it would signal the sympathetic nervous system to direct the
body to begin shivering. The adrenal glands would begin the stress response.
Kidneys secrete erythropoietin. Increasing blood cell count. Increasing
available oxygen in the body.