Chapter 10 - Homeostasis Flashcards
What is co-ordination?
It is the way that all the organs and the systems of the body work together to respond to any changes that are detected outside and inside the body.
Living organism are sensitive. What does this mean?
They are able to detect things going on around them and react to any changes.
What is the chain of events which occur, once a stimulus is detected?
1) Stimulus: change that can be detected. (Eg increase in temperature)
2) Receptors: monitors the variables and detects the change (Eg themoreceptors)
3) Co-Ordination: part of the body that decides what to do (Eg brain)
4) Effector: brings about the response. Always muscles and glands.
5) Response: in this case, sweating.
In mammals, how is co-ordination carried out?
Through the nervous system and the endocrine system.
What is homeostasis?
Cells depend on the body environment to love and function.Conditions outside the body may fluctuate at random.
However, it is very important for a cell that the internal conditions of the body (that is, the conditions in it surrounding environment - tissue fluid and blood) are kept as constant as possible.
What would happen, hypothetically, if the temperature inside your body began to rise exponentially?
Body would stop functioning. The enzymes would become denatured due to heat and lose their essential shape, red blood cells would shrink and less oxygen would be passed through circulation.
Different systems in the body need to work together to ensure, what exactly?
To ensure the internal environment is kept under control and to maintain the right conditions for cells to live and function properly.
How much are the conditions within the body allowed to fluctuate?
Conditions are allowed to fluctuate within very narrow limits - close to their optimum level.
Resulting in a state of internal balance and stability.
What is homeostasis?
The ability of the body to maintain internal conditions within very narrow limits - close to their optimum level.
How is homeostasis achieved?
For many variable that need to be controlled, the body has a set-point (reference point with the optimum level of the variable)
Any changes from the set-point (decrease or increase) activates a control system, which works to return conditions back towards their optimum.
This reaction is known as a negative feedback - negative because it negates the initial change.
What is negative feedback?
It is a mechanism concerned with making a system more stable and therefore, achieving homeostasis.
A change from the norm will result in a response.
The response to the change is to counteract the change.
Aim is to restore the normal optimum conditions.
What is a detector?
Is a sensor which constantly monitors the conditions of the variable. (Eg: temperature)
What is the optimum temperature of the human body?
37.5 degrees Celsius.
The coordinator causes the effector to respond in an appropriate manner. How so?
If the variable is too low, the coordinator sends messages to the effector to increase the variable (Eg: if temperature is too low, the coordinator causes the muscles to contract and relax rapidly - shivering - to increase body temperature)
If the variable is too high, the coordinators sends messages to the effector to decrease the variable (Eg if temperature is too high, the coordinator causes sweat glands to release sweat to decrease temp)
What does negative feedback mechanism prevent?
A continued change in one direction.
Eg: the body does not get warmer and warmer since the same warmth stimulates changes that decrease the body temperature.
Both the nervous system and the endocrine system are needed for homeostasis. Do they work together or alone?
The two system do not work independently of each other. They are linked together by a very important region in the brain known as the hypothalamus
What is the endocrine system?
It consists of endocrine glands that secrete chemical messengers called hormones.
How is the endocrine system different to the exocrine system?
Unlike exocrine glands (Eg: salivary glands), endocrine glands do not have ducts. Therefor hormones are released directly into the bloodstream and are circulated around the body to affect one or several organs.
In doing so, they help coordinate functions in different parts of the body.
What do hormones do?
Hormones transfer information and instructions from one set of cells to another.
Many different hormones move through the bloodstream, but each type of hormone is designed to affect only certain cells.
What is the thyroid gland responsible for and what does it produce?
It produces thyroxine, which controls the rate of metabolism.
What are the testes responsible for and what do they produce?m
They produce testosterone, which cause changes at puberty and stimulates sperm production.
What are the ovaries responsible for, and what do they produce?
They produce oestrogen, which causes changes at puberty and helps control the menstrual cycle.
What is the adrenal glands responsible for, and what does it produce?
It produces adrenaline, which prepares the body for rapid activity by increasing the heart rate and level of sugar in blood and diverting blood to muscles and brain.
What is the pituitary gland?
It’s a small, oval gland lying at the base of the brain. It consists of a collection of hormone producing cells.
Most of the hormones produced by the pituitary gland control several other endocrine glands round the body. This is why the pituitary gland is referred to as the master gland.
Eg: it releases Thyroid-Stimulating Hormone which stimulates the thyroid gland to produce thyroxine.
