Endocrine System

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Endocrine System

Chemical signals between organ systems

Coordinate functions over long distance and long timeframe

Endocrine cells secrete hormones

Carried in blood

Act on target tissues:

- Have receptors that fit the hormone molecule

- Hormone attaches and target cell responds

Hormone mechanisms

One hormone - many target tissues respond

Feedback regulation

Antagonistic hormones

Hormone cascades

Focus on…

What stimulates release?

What tissues release the hormone?

What's the target tissue?

What is the response?

!!!!!If you can answer these then you can tell the story!!!!!

Example of One Hormone - Many targets

Responding to fearful situations

Stimulus:

stress/fear triggers hormonal response in brain

Pituitary gland releases hormone ACTH into blood

Target tissue = adrenal gland on top of kidney

Adrenal gland releases more hormones in response:

Hormones: adrenaline and noradrenaline

Many target tissues for these hormones

Hormonal Cascade

Target Tissues respond:

Homeostasis achieved by feedback regulation and antagonistic hormones

Feedback Regulation:

When system varies from the “set point: hormones restore balance

Negative feedback loops:

Inhibits a response by reducing the initial stimulus

Turn off or dials down the process

Antagonistic Hormones balance each other out:

Involved in homeostasis

- Example: control of blood sugar

- Hormones Involved: insulin and glucagon

Two antagonistic Hormones Regulate Blood Sugar

Insulin and glucagon

Together - remove excess sugar and add more when levels dip below a set point