[B3] Hormones and Negative Feedback Systems Flashcards
What are hormones?
Chemical messengers produced by endocrine glands.
How are hormones transported around the body?
They are released directly into the bloodstream.
What are target cells?
Cells that are affected by the hormone. These cells have the right receptors to respond to the hormone.
What is a target organ?
An organ that contains target cells.
What is adrenaline?
The hormone that controls the fight or flight response by increasing the supply of oxygen and glucose to cells.
e.g initiate increased heart rate, dialation of pupils.
Which gland releases adrenaline?
The adrenal gland.
How does adrenaline work?
They bind to specific receptors in the heart, causing it to contract more frequently with more force. This increases the blood pressure.
This increases blood flow to muscles, so the cells recievee more oxygen and glucose for respiration.
Adrenaline also binds to receptors in the liver, causing it to break down glycogen and increase levels of glucose in the bloodstream.
How is the secretion of adrenaline initiated?
When the brain detects a stressful situation, it sends electrical impulses to the adrenal glands which then secrete adrenaline.
What is thyroxine made out of?
Iodine and amino acids.
Where is thyroxine released?
The thyroid gland which is found in the neck.
What does thyroxine manage?
Regulating metabolic rate - the speed at which chemical reactions in the body occur.
e.g growth, protein synthisis
How is the secretion of thyroxine initiated?
Thyroid stimulating hormone (TSH) is released from the pituitary gland and thyroxine is produced.
How does the negative feedback cycle regulate thyroxine levels?
When high levels of thyroxine in the gland is detected, the secretion of TSH is inhibited, and thus reducing levels of thyroxine in the blood.
