coordination and control - the human endocrine system Flashcards
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adrenal glands
definition
Glands located on top of the kidneys which produce adrenaline.
adrenaline
definition
Hormone produced by the adrenal gland and is released in times of fear or stress.
carbohydrate
definition
Food belonging to the food group consisting of sugars, starch and cellulose. Carbohydrates are vital for energy in humans and are stored as fat if eaten in excess. In plants, carbohydrates are important for photosynthesis.
gland
definition
An organ or tissue that makes a substance for release, such as a hormone.
glycogen
definition
Animals store glucose as glycogen in their liver and muscle tissues.
homeostasis
definition
The maintenance of steady conditions. The ability of the body to maintain a constant internal environment, eg temperature and blood glucose concentration.
hormone
definition
Chemical messenger produced in glands and carried by the blood to specific organs in the body.
hypothalamus
definition
Part of the brain which controls water balance, temperature and secretion of hormones by the pituitary gland.
negative feedback
definition
A mechanism where changes to conditions cause an action to reverse the change, to keep conditions stable.
negative feedback mechanism
definition
Mechanism to lower raised levels of something, and to raise reduced levels of something.
pancreas
definition
Large gland located in the abdomen near the stomach which produces digestive enzymes and the hormone insulin.
pituitary gland
definition
An endocrine gland that is located just below the centre of the brain. It releases a number of important hormones.
respiration
definition
The chemical change that takes place inside living cells, which uses glucose and oxygen to release the energy that organisms need to live. Carbon dioxide is a by-product of respiration.
target organ
definition
The organ with receptor molecules on its cell surfaces which recognise a specific hormone.
thyroid
definition
Gland located at the base of the neck which controls metabolic rate by releasing the hormone thyroxine.
thyroxine
definition
Hormone produced by the thyroid to control metabolism.
TRH
definition
Thyrotropin releasing hormone produced by the hypothalmus in response to a lack of thyroxine in the blood.
TSH
definition
Thyroid stimulating hormone produced by the pituitary gland in response to TRH.
Hormones and nerves
A hormone is a chemical substance, produced by a gland and carried in the bloodstream, which alters the activity of specific target organs. An example of this is the release of the hormone adrenaline, which is released by the adrenal glands. One of its target organs is the heart, where it increases the heart rate.
Like the nervous system, hormones can control the body. The effects are much slower than the nervous system, but they last for longer.
What happens to a hormone once it has been used?
Once a hormone has been used, it is destroyed by the liver.
There are important differences between nervous and hormonal control.
What is the type of signal for nervous and hormonal control?
Nervous: Electrical (chemical at synapses)
Hormonal: Chemical
There are important differences between nervous and hormonal control.
What is the transmission of signal for nervous and hormonal control?
Nervous: By nerve cells (neurones)
Hormonal: By the bloodstream
There are important differences between nervous and hormonal control.
What are the effectors for nervous and hormonal control?
Nervous: Muscles or glands
Hormonal: Target cells in particular organs
There are important differences between nervous and hormonal control.
What is the type of response for nervous and hormonal control?
Nervous: Muscle contraction or secretion
Hormonal: Chemical change
There are important differences between nervous and hormonal control.
What is the speed of response for nervous and hormonal control?
Nervous: Very rapid
Hormonal: Slower
There are important differences between nervous and hormonal control.
What is the duration of response for nervous and hormonal control?
Nervous: Short (until nerve impulses stop)
Hormonal: Long (until hormone is broken down)
Different hormones
The glands in the body produce a range of different chemical hormones that travel in the bloodstream and affect a number of different organs in the body. The diagram below shows this in detail.
Examples of important hormones released into the bloodstream.
Important hormones released into the bloodstream include ADH (anti-diuretic hormone), adrenaline and insulin.
What hormone does the thyroid gland produce?
thyroxine
What hormone does the pancreas produce?
insulin
What hormone do the testes produce?
testosterone
What hormone do the ovaries produce?
oestrogen
What hormone do the adrenal glands produce?
adrenaline
Pituitary gland
The ‘master gland’ situated at the base of the brain
What hormone does the pituitary gland produce?
ADH
What is the source of the hormone ADH?
Pituitary gland
What is the source of the hormone adrenaline?
Adrenal glands
What is the source of the hormone insulin?
Pancreas
What is the target organ(s) of AHD?
Kidneys
What are the target organs of adrenaline?
Several targets including organs in the respiratory and circulatory systems
What is the target organ of insulin?
Liver
What is the role of the hormone ADH?
Controlling the water content of the blood
What is the role of the hormone adrenaline?
Preparation for ‘fight or flight’
What is the role of the hormone insulin?
Controlling blood glucose levels
What is the effect of ADH?
Increases reabsorption of water by the collecting ducts
What are the effects of adrenaline?
Increases breathing rate, heart rate, flow of blood to muscles, conversion of glycogen to glucose
What is the effect of insulin?
Increases conversion of glucose into glycogen for storage
Master gland
The pituitary gland in the brain is known as a ‘master gland’. It secretes several hormones 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 control 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.
Coordination and control - The human endocrine system
overview
The endocrine system secretes hormones into the bloodstream from glands throughout the body. Hormones travel in the blood stream to specific target organs, where they have an effect.
Homeostatic control
In animals, conditions such as water concentration, temperature, and glucose concentration must be kept as constant as possible. Control systems that keep such conditions constant are examples of homeostasis; this is the maintenance of constant internal conditions in an organism.
Homeostatic control
Negative feedback mechanism
A negative feedback mechanism is an important type of control that is found in homeostasis. A negative feedback control system responds when conditions change from the ideal or set point and returns conditions to this set point. There is a continuous cycle of events in negative feedback.
General stages in negative feedback
In general this works by:
- if the level of something rises, control systems reduce it again
- if the level of something falls, control systems raise it again
Negative feedback
any order (is a loop)
Change detected → Corrective mechanisms activated → Conditions returned to set point → Corrective mechanisms switched off → Conditions in the body change from set point
An example of negative feedback is the control of body temperature.
An example of negative feedback is the control of body temperature. Body temperature is controlled by the hypothalamus in your brain. If your body gets too hot, your body begins 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.
Thyroxine
Thyroxine is produced from the thyroid gland, which 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.
The hypothalamus and pituitary gland have important roles in detecting and controlling thyroxine levels.
low thyroxine levels
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 blood levels return to normal.
The hypothalamus and pituitary gland have important roles in detecting and controlling thyroxine levels.
normal thyroxine levels
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.
The control of thyroxine levels by the hypothalamus and pituitary gland is an example of what?
The control of thyroxine levels by the hypothalamus and pituitary gland is an example of negative feedback.
Adrenaline
Adrenaline is 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’. Adrenaline is not controlled by negative feedback.
When adrenaline is released into the bloodstream it creates multiple effects:
What do these effects result in?
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.
What do the effects of adrenaline do?
The effects of adrenaline allow the body to prepare for action in situations where a quick response may be needed.
Regulating blood glucose
Glucose is needed by cells for respiration. It is important that the concentration of glucose in the blood is maintained at a constant level and controlled carefully. Insulin is a hormone produced by the pancreas which regulates glucose concentrations in the blood.
What happens if the blood glucose concentration is too high?
If the blood glucose concentration is too high, the pancreas produces the hormone insulin, this 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.
Action of insulin
effect of low glucose on pancreas
Insulin not secreted into the blood
Action of insulin
effect of high glucose on pancreas
Insulin secreted into the blood
Action of insulin
effect of low glucose on liver
Does not convert glucose into glycogen
Action of insulin
effect of high glucose on liver
Converts glucose into glycogen
Action of insulin
effect of low glucose on blood glucose level
Increases
Action of insulin
effect of high glucose on blood glucose level
Decreases
how insulin works in the body
high levels of glucose
1) too much glucose in the blood
2) pancreas produces insulin which enters blood
3) Insulin allows glucose to be absorbed by body cells
4) blood glucose is reduced.
how insulin works in the body
low levels of glucose
1) normal levels of glucose in the blood
2) insulin not produced by the pancreas
3) Less glucose absorbed by body cells
4) Blood glucose remains the same.
What is diabetes?
Diabetes is a condition where the blood glucose levels cannot be controlled by the body. There are two types of diabetes - type 1 and type 2.
What is type 1 diabetes?
Type 1 diabetes is a disorder in which the pancreas fails to produce enough insulin. This can be detected from an early age. It is characterised by uncontrolled high blood glucose levels and it can be controlled by injecting insulin.
Effect and mangement of type 1 diabetes
People with type 1 diabetes have to monitor their blood sugar levels throughout the day. Their levels of physical activity and their diet affect the amount of insulin needed.
Control (somewhat) of type 1 diabetes
They can help to control their blood glucose level by being careful with their diet, and eat foods that will not cause large increases in blood sugar level, and by exercising, which can lower blood glucose levels due to increased respiration in the muscles.
Type 2 diabetes
In type 2 diabetes the person’s body cells no longer respond to insulin produced by the pancreas. It is more common in older people. It can be controlled by a carbohydrate controlled diet and an exercise regime. Carbohydrate is digested into glucose, which raises the overall blood glucose level. There is a correlation between rising levels of body mass in the general population and increasing levels of type 2 diabetes.
Commonly accepted BMI ranges are:
underweight: under 18.5 kg/m2
normal weight: 18.5 to 25 kg/m2
overweight: 25 to 30 kg/m2
obese: over 30 kg/m2
Who is at an increased risk of developing type 2 diabetes?
People who are overweight or obese have an increased risk of developing type 2 diabetes.
waist to hip ratio
Waist:hip ratio = waist measurement/hip measurement.
effects of waist to hip ratio
Scientific research has also indicated that people who have more weight around their waist are at a higher risk from developing certain illnesses, such as type 2 diabetes, than people who have more weight around their hips. This is determined by calculating waist to hip ratio:
waist to hip ratio and obesity
A waist:hip ratio of over 0.85 in women and 1 in men is considered an indicator of obesity.
Negative feedback
In blood glucose regulation, the hormone insulin plays a key role. When blood sugar rises in the blood, insulin sends a signal to the liver, muscles and other cells to store the excess glucose. Some is stored as body fat and other is stored as glycogen in the liver and muscles. If the blood glucose level is too low, the pancreas releases the hormone glucagon. This travels to the liver in the blood and causes the break-down of glycogen into glucose. The glucose enters the blood stream and glucose levels increase back to normal.
How glucose is regulated
What happens in the pancreas if blood glucose is too high?
Insulin secreted into the blood
How glucose is regulated
What happens in the liver if blood glucose is too high?
Liver converts glucose into glycogen
How glucose is regulated
What is the effect on glucose if blood glucose is too high?
Goes down
How glucose is regulated
What happens in the pancreas if blood glucose is too low?
Glucagon (not insulin) is secreted into the blood.
How glucose is regulated
What happens in the liver if blood glucose is too low?
Liver does not convert glucose into glycogen. Glycogen is converted to glucose.
How glucose is regulated
What is the effect on glucose if blood glucose is too low?
Goes up
What are hormones?
Chemicals secreted by glands
How are hormones transported around the body?
By blood
Adrenalin is released by which gland?
Adrenal gland
Which hormone is released in response to high blood glucose levels?
Insulin is released in response to high blood glucose levels. It lowers blood glucose.
Which conversion happens when insulin lowers blood glucose?
Insulin converts glucose into glycogen, in order to lower blood glucose levels.
Which is a treatment for type 1 diabetes?
Insulin injections
Which is the target organ for insulin and glucagon?
Liver
Which type of feedback is important for homeostasis?
Negative feedback is important for homeostasis. It is a response carried out when conditions change from the ideal or set point. It returns conditions to this set point.
Adrenalin has which affect on the heart rate?
Adrenalin increases the heart rate. It also increases blood pressure, blood flow to muscles and the conversion of glycogen to glucose.
If thyroxine levels are low, which hormone is released from the pituitary gland?
If thyroxine levels are low, TSH is released from the pituitary gland. TSH will stimulate the thyroid to release thyroxine.
How is blood glucose increased?
Glucagon converts glycogen into glucose in order to increase blood glucose.
