Human Endocrine System - Hormones: Adrenaline and Thyroxine (GCSE Biology)
Hormones: Adrenaline and Thyroxine
Thyroxine and adrenaline are two key hormones which are very important for metabolism and the normal running of the body.
Adrenaline
Adrenal Glands and Adrenaline
Adrenaline is a hormone produced by the adrenal glands. The adrenal glands are endocrine glands that sit above the kidneys.
Adrenaline is released in situations where the body has an increased demand for oxygen. For example, when an animal is being hunted, adrenaline is released.
Physiological Effects of Adrenaline
Adrenaline causes many physiological changes to take place. These include:
- Increased heart rate and blood pressure – pumps more blood around the body for the muscles.
- Glucose production – increases the breakdown of glycogen into glucose in the liver, increasing glucose supply for respiring muscles.
- Vasoconstriction in the gut – causes ‘butterflies in stomach’, and allows blood to be redirected to the muscles and brain, for increased oxygen delivery
- Pupil dilation – makes the individual more alert
- Bronchioles widen – increases ventilation to get more air in for faster gas exchange
All of these effects lead to an overall increase in oxygen supply to the muscles that are required. This is very helpful in such situations as described earlier. That is why it is known as the ‘flight or fight’ reflex. Therefore, the body increases its ability to escape, or hunt in certain scenarios for example, in the case of an emergency, before a test or in extreme sports like sky diving.
Thyroxine
Thyroid Glands and Thyroxine
The thyroid gland is an important endocrine gland that resides in the throat. It is shaped like a butterfly and has two lobes. The thyroid makes the hormone thyroxine.
Thyroxine is a very important hormone in the he body, which works to control the basal metabolic rate. This is the body’s natural rate of metabolism.
Thyroxine and Negative Feedback
Thyroxine levels are controlled due to negative feedback. The hypothalamus, pituitary gland and thyroid glands are involved in this:
When thyroxine levels are low:
- Low levels of thyroxine stimulate the hypothalamus to release Thyrotropin Releasing Hormone (TRH)
- The TRH causes the pituitary gland to release Thyroid Stimulating Hormone (TSH)
- The TSH travels in the blood and acts on the thyroid gland to produce thyroxine
- Thyroxine levels increase
When thyroxine levels are normal or high:
- The thyroxine levels inhibit the release of TRH and the production of TSH
- Thyroxine levels decrease
Hypothyroidism
If you have too little thyroxine, you become hypothyroid and the basal metabolic rate decreases. This causes:
- Weight gain
- Increased heart rate
- Loss of appetite
- Reduced fertility
Hyperthyroidism
On the other hand, if there is too much thyroxine, you become hyperthyroid and the basal metabolic rate increases. This will lead to:
- Weight loss
- Palpitations
- Irregular menstrual cycle in females
- Irritability
- Possible swelling near the eyes, causing the eyes to appear popped out
Both of these circumstances can present with a swelling known as a goitre in the neck.
These conditions therefore affect the growth and repair of the body. Therefore, it is very important to keep thyroxine levels under to control.
FAQs
The human endocrine system is a network of glands that produce and secrete hormones into the bloodstream to regulate various bodily functions. Hormones act as chemical messengers, transmitting signals to target cells throughout the body to help regulate growth, metabolism, and other important processes.
Adrenaline is a hormone produced by the adrenal gland that prepares the body for action in response to stress or danger. Adrenaline increases heart rate, breathing rate, and blood pressure to provide more oxygen and energy to the muscles, and also causes the release of glucose from the liver to provide a quick source of energy.
Thyroxine is a hormone produced by the thyroid gland that regulates metabolism and helps control the body’s energy production. It stimulates the metabolism of cells, increases heart rate, and helps regulate the growth and development of bones and other tissues.
Adrenaline affects the body by preparing it for action in response to stress or danger. It increases heart rate, breathing rate, and blood pressure, and also causes the release of glucose from the liver to provide a quick source of energy. This allows the body to respond quickly and effectively to potential threats.
Thyroxine affects the body by regulating metabolism and helping control the body’s energy production. It stimulates the metabolism of cells, increases heart rate, and helps regulate the growth and development of bones and other tissues. It also helps regulate body temperature and plays a role in the regulation of calcium levels in the blood.
If there is too much adrenaline in the body, it can cause symptoms such as increased heart rate, sweating, anxiety, and high blood pressure. On the other hand, if there is too little adrenaline, the body may not respond effectively to stress or danger, and may experience symptoms such as fatigue, low blood pressure, and slow heart rate.
If there is too much thyroxine in the body, it can cause symptoms such as weight loss, increased heart rate, and sweating. On the other hand, if there is too little thyroxine, the body may experience symptoms such as fatigue, weight gain, and cold intolerance. An imbalance of thyroxine levels can also affect growth and development in children.
Common causes of imbalanced levels of adrenaline and thyroxine in the body include stress, certain medications, and certain medical conditions such as adrenal gland disorders and thyroid disorders. In some cases, imbalanced hormone levels can also be due to genetic factors.
Treatment for imbalanced levels of adrenaline and thyroxine typically involves medications to regulate hormone levels, as well as lifestyle changes to manage stress and improve overall health. In some cases, surgery may be necessary to remove a gland that is producing too much or too little hormone. Your doctor can provide more information on the best treatment options for your specific condition.
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