3.4.6 - Homeostasis and Negative Feedback

Why is homeostasis important?

Homeostasis is important as it ensures the maintenance of optimal conditions for enzyme action and cell function.

What detects information about the conditions inside/outside the body?

Sensory cells detect information about the conditions in/outside the body.

What are the two types of coordination systems?

Nervous and endocrine

How is information sent in the nervous system?

Information is sent as nerve impulses (electrical signals)

How does this information move?

pass along nerve cells known as neurones.

A bundle of neurons is a nerve.

Neurones coordinate the activities of sensory receptors, decision-making centres in the CNS and effectors.

What is the CNS and PNS?

CNS- Brain and spinal cord.

PNS- all of the nerves in the body.

How is information send in the endocrine system?

Hormones, These chemicals transmit information from one part of an organism to another and bring about a change. Hormones are used to control functions that do not need instant responses.

Where are hormones produced?

Hormone is a chemical substance produced by an endocrine gland and carried by the blood.

What is a gland?

Gland - group of cells that produces and releases one or more substances.

What cells do hormones affect?

Endocrine glands have a good blood supply. Hormones only affect cells with receptors.

What two internal body conditions do you need to control? Why?

Two key factors to be controlled- Temperature, pH.

A stable core temperature and blood pH are vital for enzyme activity.

Explain why Temperature needs to be controlled in detail.

Temperature- enzymes have a specific optimum temperature- Temperature at which they catalyse a reaction at the maximum rate. Lower temperatures- prevent/slow down. Molecules move slow so less frequent enzyme substrate complexes formed, maily because they collide with less energy, making it less likely for bonds to be formed/broken.

High temperatures- move quickly, more successful collisions.

Too high temperature- Denature. Hydrogen bonds start to break, causing tertiary structure to change.

Explain why pH needs to be controlled in detail.

pH- all enzymes have an optimum pH. Enzymes are denatured at extreme pH as an excess of H+ and OH- ions cause hydrogen and ionic bonds to break, denaturing it.

What is another condition that needs to be controlled?

The concentration of glucose in the blood also has to be controlled.

The amount of glucose present in the blood affects the water potential of the blood and the availability of respiratory substrate for cells

A sufficient amount of glucose is essential for cellular respiration.

What is negative feedback?

Negative feedback (keeps conditions within certain limits-

Receptor, coordination system, effector.

Continuously monitored. Increase- detected by stimuli, body responds to make the factor decrease. Vice versa. The system is restored to its original level.

Why is negative feedback important?

Receptors detect any deviations from the normal range which results in a corrective mechanism to return the factor to its normal range (may involve nervous or endocrine system). They have two corrective mechanisms.

Describe Positive Feedback

Positive feedback- stimulus produces a response that causes the factor to deviate even more from the normal range.