Flashcards in SB7 Deck (79)
What is a hormone?
A chemical substance, produced by a gland and carried in the bloodstream, which alters the activity of specific target organs.
What are target organs?
The organ with receptor molecules on its cell surfaces which recognise a specific hormone.
What hormone is released by the adrenal glands?
What is one of the target organs of adrenaline?
The heart, which increases the heart rate.
What happens once a hormone has been used?
It is destroyed by the liver.
What are the effects of hormones?
The effects are much slower than the nervous system, but they last for longer.
Compare and contrast the nervous system and the hormonal system.
Type of signal- Electrical (chemical at synapses).
Transmission of signal- By nerve cells (neurones).
Effectors- muscles or glands.
Type of response- Muscle contraction or secretion.
Speed of response- Very rapid.
Duration of response- Short (until nerve impulses stop).
Type of signal- Chemical.
Transmission of signal- By the bloodstream.
Effectors- Target cells in particular organs.
Type of response- Chemical change.
Speed of response- Slower.
Duration of response- Long (until hormone is broken down).
What hormone does the thyroid gland produce?
What hormone does the pancreas?
What hormone does the testes produce?
What hormone do the ovaries produce?
What is the pituitary gland?
The 'master gland' situated at the base of the brain.
What hormone is produced at the pituitary gland?
ADH. Its target organ is the kidneys and its role is to control the water content of blood. Its effect is that it increases reabsorption of water by the collecting ducts.
What hormone is produced at the adrenal glands?
Adrenaline. It has several target organs including the respiratory and circulatory systems. Its role is preparation for 'fight or flight'. It increases the breathing rate, heart rate, flow of blood to muscles and conversion of glycogen to glucose.
What hormone is produced in the pancreas?
Insulin. Its target organ is the liver. Its role is controlling blood glucose levels. It increases conversion of glucose into glycogen for storage.
What happens at the pituitary gland?
It secretes several hormones into the blood into the blood in response to the body's condition, such as blood water levels. The hypothalamus detects changes in hormone levels and will release hormones which controls the pituitary gland or other organs. The hormones from the hypothalamus and pituitary can also act on other glands to stimulate the release of different types of hormones and bring about effects.
In animals, conditions such as what are kept constant as possible?
Water concentration, temperature, and glucose concentration.
Control systems that keep such conditions constant are examples of what?
Homeostasis; this is the maintenance of constant internal conditions in an organism.
What type of mechanism is an important type of control that it found in homeostasis?
Negative feedback mechanism.
When does a negative feedback control system respond?
When conditions change from the ideal or set point and returns conditions to this set point.
How does the negative feedback system work?
- If the level of something rises, control systems reduce it again.
- If the level of something falls, control systems reduce it again.
Give an example of negative feedback.
The control of body temperature. Body temperature is controlled by the hypothalamus in your brain. If your body gets too hot, your body begin to sweat, which reduces body temperature. In the opposite way, if the body gets too cold, your body begins to shiver to raise body temperature.
What does thyroxine do?
Stimulates the metabolic rate. It controls the speed at which oxygen and food products react to release energy for the body to use. Thyroxine also plays an important role in growth and development. Its levels are controlled by negative feedback.
What 2 things have important roles in detecting and controlling thyroxine levels?
Hypothalamus and pituitary gland:
1. Low thyroxine levels in the bloodstream stimulate the hypothalamus to release TRH and this causes the pituitary to release TSH so the thyroid releases more thyroxine. So the blood levels return to normal.
2. Normal thyroxine levels in the bloodstream inhibit TRH release from the hypothalamus and the production of TSH by the pituitary, so normal blood levels are maintained.
This is an example of negative feedback.
What happens when adrenaline is released into the bloodstream?
It creates multiple effects:
1. increases breathing rate, heart rate (therefore blood flow) and blood pressure.
2. conversion of glycogen to glucose in liver cells, increasing blood glucose.
These effects result in more glucose being delivered to the muscles and more energy being released by respiration in the muscles.
The effects of adrenaline allow the body to prepare for action in situation where a quick response may be needed.
Glucose is needed by cells for what?
What is insulin?
A hormone produced by the pancreas which regulates glucose concentration in the blood.
What happens if the blood glucose concentration is too high?
The pancreas produces the hormone insulin, which causes glucose to move from the blood into the cells. In liver and muscle cells excess glucose is converted to glycogen for storage and will be used at a later date.
What happens if there is low glucose?
Insulin is not secreted into the blood, the liver doesn't convert glucose into glycogen and the blood glucose level increases.