Chapter 10 - Homeostasis

Question 0

What is co-ordination?

Answer 0

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.

Question 1

Living organism are sensitive. What does this mean?

Answer 1

They are able to detect things going on around them and react to any changes.

Question 2

What is the chain of events which occur, once a stimulus is detected?

Answer 2

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.

Question 3

In mammals, how is co-ordination carried out?

Answer 3

Through the nervous system and the endocrine system.

Question 4

What is homeostasis?

Answer 4

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.

Question 5

What would happen, hypothetically, if the temperature inside your body began to rise exponentially?

Answer 5

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.

Question 6

Different systems in the body need to work together to ensure, what exactly?

Answer 6

To ensure the internal environment is kept under control and to maintain the right conditions for cells to live and function properly.

Question 7

How much are the conditions within the body allowed to fluctuate?

Answer 7

Conditions are allowed to fluctuate within very narrow limits - close to their optimum level.
Resulting in a state of internal balance and stability.

Question 8

What is homeostasis?

Answer 8

The ability of the body to maintain internal conditions within very narrow limits - close to their optimum level.

Question 9

How is homeostasis achieved?

Answer 9

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.

Question 10

What is negative feedback?

Answer 10

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.

Question 11

What is a detector?

Answer 11

Is a sensor which constantly monitors the conditions of the variable. (Eg: temperature)

Question 12

What is the optimum temperature of the human body?

Answer 12

37.5 degrees Celsius.

Question 13

The coordinator causes the effector to respond in an appropriate manner. How so?

Answer 13

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)

Question 14

What does negative feedback mechanism prevent?

Answer 14

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.

Question 15

Both the nervous system and the endocrine system are needed for homeostasis. Do they work together or alone?

Answer 15

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

Question 16

What is the endocrine system?

Answer 16

It consists of endocrine glands that secrete chemical messengers called hormones.

Question 17

How is the endocrine system different to the exocrine system?

Answer 17

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.

Question 18

What do hormones do?

Answer 18

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.

Question 19

What is the thyroid gland responsible for and what does it produce?

Answer 19

It produces thyroxine, which controls the rate of metabolism.

Question 20

What are the testes responsible for and what do they produce?m

Answer 20

They produce testosterone, which cause changes at puberty and stimulates sperm production.

Question 21

What are the ovaries responsible for, and what do they produce?

Answer 21

They produce oestrogen, which causes changes at puberty and helps control the menstrual cycle.

Question 22

What is the adrenal glands responsible for, and what does it produce?

Answer 22

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.

Question 23

What is the pituitary gland?

Answer 23

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.

Question 24

What are some other hormones released by the pituitary gland?

Answer 24

Growth hormone, corticotropin and anti-diuretic hormone.
Also secrete hormones that signal the ovaries and testes to make sex hormones. Oxytocin and prolactin are also produced during and after pregnancy.

Question 25

What controls the hormones which are released by the pituitary gland?

Answer 25

The hypothalamus.

Question 26

What is the pancreas?

Answer 26

It is an elongated, feather like organ located at the back of the abdomen, just behind the stomach.
It is connected to the duodenum via the pancreatic duct.

Question 27

The pancreas consists of 2 types of glands and have 2 different functions. What are they?

Answer 27

Exocrine glands: These give the pancreas a digestive function since they release digestive enzymes into the duodenum. (Tripsin, amylase, and lipase)
Endocrine glands: These give the pancreas an endocrine function since they release hormones into the bloodstream. The hormones released by the own crease are concerned with regulation of blood glucose levels.

Question 28

What do we find in the pancreas? (Which is revealed through a cross section)

Answer 28

The Islets of Langerhans. (Endocrine)
They have a good blood supply since endocrine glands secrete hormones into the blood stream (not into ducts like the digestive pancreas)

Question 29

The islets of Langerhans are made up of 2 cells. What are they?

Answer 29

Beta cells, which secrete insulin

Alpha cells which secrete glucagon.

Question 30

What are the desired blood glucose levels?

Answer 30

Between 70mg and 110mg/100cm.

The average is about 90/100cm.

Question 31

How can blood glucose levels vary?

Answer 31

After a meal which is rich in carbohydrates, it may rise to 150mg/100cm.
After either starvation or prolonged activity, it may drop to 70mg/100cm.

Question 32

How are changes in blood glucose levels detected?

Answer 32

By chemoreceptors in pancreas.
They are found in the islets of Langerhans, which are specialised in design to respond to chemical stimuli.
These cells are usually designed with customised locks which only fit the keys if specific chemicals. Making the sensitive to only certain types of chemicals.

Question 33

What happens if your blood glucose level rises, in homeostatic terms?

Answer 33

1) Glucose enters the circulatory system through the ileum.
2) Blood glucose levels rises.
3) Islets of Langerhans in the pancreas detect the change in level.
4) The pancreas responds to high blood glucose by activation of Beta cells (in islets of langerhans) which produce insulin.
5) Insulin enters the blood stream and travels around the body.
6) At target organs, insulin joins special insulin receptors.
7) This causes a structural change in the membrane and glucose channels open.
8) Glucose flows out of the blood and into body cells (Eg used in metabolism to produce energy which the cell needs)
9) This causes the blood glucose level to return to normal and insulin secretion stops.

Question 34

What happens if your blood glucose level drops, in homeostatic terms?

Answer 34

1) During exercise, for example, muscle cells take up a lot of glucose since they need it for respiration.
2) The blood glucose level drops.
3) Pancreas respond to low glucose by activating Alpha cells (islets of langerhans) that produce glucagon.
4) Glucagon enters the blood stream and travels to the liver.
5) At the target organ, glucagon attached to proteins on the cell membrane.
6) Causing a large amount of chemical reactions to occur inside the cell, which convert glycogen and amino acids into glucose.
7) Glucose then enters the bloodstream, increase the blood glucose level so that it returns to normal and glucagon secretion stops.