3.3 Feedback Mechanisms, Stimuli, and Hormones

What do negative feedback mechanisms control?

the synthesis and release of hormones

In negative feedback, the target/effector organ's response feeds back and has what affect on further hormone production?

it inhibits further hormone production

How many types of stimuli trigger endocrine glands?

three

What two things do endocrine glands primarily do with hormones?

make and release them

What are the three types of stimuli that trigger endocrine glands to make and release hormones?

humoral stimuli, neural stimuli, and hormonal stimuli

What are humoral stimuli?

hormone release caused by altered levels of critical ions or nutrients

Which stimuli is the simplest endocrine control?

humoral stimuli

What is an example of humoral stimuli?

how the parathyroid gland controls calcium (Ca2+) levels by secreting parathyroid hormone

What are neural stimuli?

hormone release caused by neural input

What is an example of neural stimuli?

how the sympathetic nervous system stimulates the endocrine in response to stress

What are hormonal stimuli?

hormone release caused by another hormone

What stimuli promotes rhythmic hormone release?

hormonal stimuli

What is an example of hormonal stimuli?

hormones secreted by hypothalamus leads pituitary gland to secrete hormones which stimulates other glands

Specific receptors are required for hormones to what?

alter the activity of target cells

Where must the specific receptor be in order for the hormone to bind?

on or within the target cell

What three things does the response in the target cell depend on?

how much hormone is in the blood, relative numbers of receptors for the hormone, and strength (affinity) of the binding between hormone and receptor

Do most target cells have multiple types of receptors or just one type?

multiple types of receptors for different hormones

What is permissiveness?

when a hormone can't do its job fully without another hormone present

The fact that most target cells have multiple types of receptors for different hormones leads to what three things?

permissiveness, synergism, and anatgonism

What is an example of permissiveness?

the reproductive system hormones can't do their jobs unless the thyroid hormone has stimulated reproductive development

What is synergism?

when more than one hormone produces the same effects as the target cell which leads to an amplified combined effect

What is an example of synergism?

both glucagon and epinephrine cause the liver to release glucose to the blood, and when acting at the same time on the same cell, they can release way more glucose

What is antagonism?

when one hormone opposes the action of another

What is an example of antagonism?

insulin lowers blood glucose levels and glucagon raises them