Endocrine System Overview

The endocrine system uses hormones to regulate growth, development, and metabolism, releasing them directly into the bloodstream.

The main endocrine glands include the pituitary, pineal, thyroid, parathyroid, and adrenal glands. Other organs with endocrine functions are the stomach, pancreas, ovaries, and testes.

Hormonal stimulation involves one hormone triggering the release of another. For example, TSH (thyroid-stimulating hormone) prompts the thyroid to release thyroid hormone.

Humoral stimulation occurs when changes in blood chemistry trigger hormone release. For example, low blood glucose triggers the release of glucagon.

Nervous system stimulation involves direct signaling from the nervous system to trigger hormone release. For example, the sympathetic nervous system triggers hormone release in times of stress.

Circulating hormones travel through the bloodstream to reach their target cells, while local hormones act on nearby cells without circulating.

Autocrine signaling involves a cell acting on itself with a hormone, while paracrine signaling involves a cell acting on neighboring cells.

Lipid-soluble hormones dissolve in fats, can pass through cell membranes, and bind to intracellular receptors. Water-soluble hormones bind to receptors on the cell membrane, triggering a signaling cascade.

The process by which a hormone interacts with a target cell, leading to a specific response. This response is influenced by factors like the hormone concentration, receptor numbers, and interactions with other hormones.

A type of hormone interaction where one hormone amplifies the effect of another. For example, estrogen and luteinizing hormone work together to stimulate ovulation.

A type of hormone interaction where one hormone requires the presence of another to function properly. Prolactin and oxytocin demonstrate this, where prolactin prepares the breast for milk production, and oxytocin triggers milk release.

A type of hormone interaction where two hormones have opposing effects. Insulin and glucagon are an example, where insulin lowers blood sugar and glucagon raises it.

The body's response to stress, characterized by three stages: alarm reaction, resistance reaction, and exhaustion reaction.

The initial stage of the stress response, marked by activation of the sympathetic nervous system, leading to the fight-or-flight response.

The second stage of the stress response, characterized by prolonged activation of the sympathetic nervous system, increased cortisol levels, and use of glycogen reserves.

The final stage of the stress response, marked by depletion of resources, leading to fatigue, weakened immune system, and potential health problems.