Endocrine System

Endocrine SystemThe endocrine system is a system of glands, each of which secretes a type of hormone to regulate the body.

The endocrine system is an information signal system much like the nervous system. Hormones are like chemical messengers that “tell” other organs to do something, which sometimes means to produce their own hormones.

Hormones regulate many functions of an organism, including mood, growth and development, tissue function, and metabolism.

Hypothalamus- Helps body maintain homeostasis.

Pituitary- helps regulate human growth and physical development or maturity; secretes hormones that control other glands. Often referred to as “the master gland.”

Thyroid- regulates metabolism (the rate at which cells burn fuels from food to produce energy). This influences body temperature, weight, other factors.

Pancreas- releases the hormones insulin and glucagon which regulate the amount of glucose in the blood.

Adrenal- releases adrenalin.

http://www.youtube.com/watch?v=kIPYVV4aThM

Review- complete the following sentences:

The endocrine system consists of a number structures called ____________ which produce chemical messengers called ________________. These chemicals play a role in regulating a wide variety of ________________________ .

glands

hormones

bodily or system functions.

The main function of the hypothalamus is homeostasis, or maintaining the body's status quo. Factors such as blood pressure, body temperature, fluid and electrolyte balance, and body weight are held to a precise value called the set-point. Although this set-point can change over time, from day to day it is remarkably fixed.

To achieve this task, the hypothalamus must receive inputs about the state of the body, and must be able to make changes or adjustments if anything drifts out of whack.

Extension information

The pituitary gland is sometimes called the "master" gland of the endocrine system, because it controls the functions of the other endocrine glands. The pituitary gland is no larger than a pea, and is located at the base of the brain.

The pituitary gland secretes hormones that cause other glands in the body to start secreting their own hormones that affect such things as growth, adrenaline, milk production, puberty and sex hormones, skin pigmentation, and other things.

Negative Feedback and HomeostasisNegative feedback is the main mechanism for controlling blood levels of hormones and helping the body to maintain homeostasis. In a negative feedback system, levels of one type of hormone influence the level of other types of hormones.

Negative feedback loops create "comfort zones". A common illustration of these loops is a thermostat. If you set a thermostat to 72 degrees and turn it on, the heating/air conditioning unit will take constant measurements of the temperature. If it gets too hot, it will turn on the AC. If it get too cold, it will turn on the heater. Thus, the room stays within a predetermined "comfort zone."

An example of a negative feedback in the body is demonstrated by the pancreas.

When glucose levels in the blood get too high, the pancreas releases the hormone insulin. Insulin triggers the body to start converting the glucose to a form that can be stored for later use (glycogen, fat).

When glucose levels in the blood get to low, the pancreas secretes the hormone glucagon which triggers the body to change the glycogen back into glucose while also causing the body to stop storing fat.

Negative feedback loops exist for blood pressure, body temperature, and a whole host of other body functions.

Let’s see what this looks like in a visual representation.

1. What happens to blood sugar levels after the morning meal and after lunch?After eating, blood sugar levels increase dramatically.2. What was the highest blood glucose concentration in this time period? Approximately 120 mg/100 cm (also referred to as 120 mg/dL.)3. Normal fasting glucose levels (levels after 8 hours with no food) should be between 70 mg/dL and 100 mg/dL. Was this person’s glucose level within the normal range prior to the morning meal? Yup.

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4. What is happening to the blood glucose level between 10:50 a.m. and 12:30 p.m.?It is decreasing.5. According to the graph, why is the blood glucose level dropping in the area marked by the red bracket?The excess glucose is being stored in the liver as glycogen and in fat tissues.6. At 10:10 a.m., the blood glucose levels are continuing to rise even though the person did not eat. What is the most likely explanation for this continued increase?Neither glucagon nor insulin can shut themselves “off.” The glucagon keeps signaling the liver to release glucose even after the normal level has been attained. Insulin must be released to counteract the effects of the glucagon.

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Excess glucose is stored as glycogen in the liver, in normal cells, and as fat in fat cells.

Glycogen in the liver is converted back into glucose and released into the blood stream.