The Endocrine Sustem Flashcards
What is the endocrine system
The endocrine system is a collection of glands throughout the body that secrete hormones directly into the blood
What do hormones do
Hormones produced by the endocrine system regulate body functions including metabolism, fertility and water balance
What is negative feedback
Negative feedback is a regulatory mechanism in which a stimulus causes an opposite output in order to maintain an ideal level of whatever is being regulated
What is positive feedback
Positive feedback back is when the body responds to already low/high levels of hormones in the body, and amplifies those levels, rather than to try and balance them and control them
Example of negative feedback
If there is a very high level of thyroxine produced, the pituitary gland sends a signal to the thyroid gland, to stop the prediction of thyroxine until the levels are stable and balanced again
What is an example of positive feedback
During childbirth, the pituitary gland produces extra oxytocin, producing very high levels in the body. The oxytocin helps muscle contractions and acts as a natural pain reliever
What are the main glands
- pituitary gland
- thyroid gland
- adrenal gland
- pancreatic gland
- ovarian gland
- glands in the testes
What does the thyroid gland release
Thyroxine - contrails how much energy your body uses (metabolic rate), aids brain development, bone health, and muscle control
What do the adrenal glands release
Adrenaline - produced by the adrenal glands in times of fear or stress. It targets vital organs, increases the heart rate and boosts the delivery of oxygen and glucose to the brain and muscles, preparing the body for ‘flight or fight’.
What do the pancreatic glands release
Insulin - helps the breakdown of sugar in the blood stream
What do the ovary glands release
Oestrogen - helps female puberty, and menstrual development
What do the testicular glands produce
Testosterone - male puberty
How does adrenaline work
- Adrenaline is a hormone that triggers the “fight or flight” response in stressful or dangerous situations.
- It increases heart rate, breathing rate, and blood flow to muscles, preparing the body for action.
- It also releases stored glucose into the blood for extra energy.
How is adrenaline released
- The hypothalamus in the brain detects stress or danger.
- It sends signals via the nervous system to the adrenal glands (located on top of the kidneys).
- The adrenal glands release adrenaline into the bloodstream.
Why is adrenaline important
- It helps the body respond quickly to emergencies.
- Provides the energy and physical readiness needed to escape or confront a threat.
What does adrenaline control
- Heart rate: makes the heart beat faster to pump blood more efficiently.
- Airways: widens them to allow more oxygen intake.
- Blood vessels: redirects blood to muscles and away from non-essential organs.
- Glucose levels: increases blood sugar to fuel muscles
What does excess adrenaline cause
- Anxiety or restlessness due to overstimulation of the nervous system.
- High blood pressure and a rapid heartbeat.
- Sweating, headaches, or difficulty sleeping.
- In extreme cases, it can lead to long-term stress and health problems.
What does not having enough adrenaline do
- Reduced ability to respond to stress or danger.
- Fatigue and lack of energy, as glucose release is impaired.
- Difficulty maintaining blood pressure, which can lead to dizziness or fainting.
What Signals Adrenaline to Be Released?
The hypothalamus activates the sympathetic nervous system in response to:
- Physical danger (e.g., a predator or accident).
- Emotional stress (e.g., anxiety or fear).
- Excitement or exercise can also trigger smaller releases
How does thyroxine work
Thyroxine is a hormone produced by the thyroid gland (in the neck).
It regulates the body’s metabolic rate, controlling how fast energy is used.
It affects growth, development, and body temperature
How is thyroxine released
- The hypothalamus in the brain releases thyrotropin-releasing hormone (TRH).
- TRH stimulates the pituitary gland to release thyroid-stimulating hormone (TSH).
- TSH signals the thyroid gland to produce and release thyroxine into the blood.
Why is thyroxine important
- It ensures cells have enough energy to function properly by increasing the metabolic rate.
- It helps regulate body temperature, supporting processes like sweating or shivering.
- It is vital for growth and brain development, especially in children.
What does thyroxine control
- Metabolic rate: the speed at which cells convert nutrients into energy.
- Heart rate: increases in thyroxine can make the heart beat faster.
- Protein synthesis: promotes tissue repair and growth.
- Development: plays a key role in bone growth and brain development
What does an excess of thyroxine do
- Overactive metabolism leading to weight loss and heat intolerance.
- Rapid or irregular heartbeat and increased nervousness or anxiety.
- Muscle weakness, sweating, and fatigue.
What does not having enough thyroxine do
- Slow metabolism, causing weight gain and cold intolerance.
- Fatigue, depression, and difficulty concentrating (“brain fog”).
- Dry skin, hair loss, and slower growth in children.
- Severe deficiency during infancy can lead to developmental delays.
What signals thyroxine to be released
- Low levels of thyroxine in the blood are detected by the hypothalamus.
- This triggers the release of TRH, starting the chain reaction (TRH → TSH → thyroxine).
- When enough thyroxine is in the blood, the process slows down in a negative feedback loop.
How do hormones stimulate cells to perform their functions
- Hormones are chemical messengers released by endocrine glands and travel in the blood to target cells.
- Target cells have specific receptors that recognize and bind to the hormone.
- Hormone-receptor binding triggers changes in the target cell, activating or inhibiting processes.
- Peptide hormones (insulin) bind to cell surface receptors, triggering secondary messengers inside the cell.
- Steroid hormones (oestrogen) pass through the cell membrane and directly influence gene expression in the nucleus.
- Negative feedback mechanisms regulate hormone levels to maintain balance in the body.
What is a hormone
Hormones are large chemical molecules produced by the endocrine glands and are secreted in the blood
How is the thyroid stimulated to release thyroxine
- Thyroxine regulates the body’s basal metabolic rate, heart rate, and temp
- Hypothalamus detects low/high levels of Thyroxine and releases/slows release of thyrotropin-releasing hormone (TRH),
- TRH stimulates the Pituitary gland to secrete Thyrold stimulating hormone (TSH)
- TSH stimulates the Thyroid gland to release Thyroxine
