Homeostasis

Question 1

What is homeostasis?

Answer 1

• Refers to the body’s ability to maintain its internal environment within narrow parameters. Not a static process - dynamic, constantly changing process.
• Moderated by feedback mechanisms.

Question 1

Failure to maintain homeostasis leads to?

Answer 1

• Heart failure.
• Diabetes Mellitus
• Diabetes Inspidus
• Hypertension
• Graves’ Disease
• Haemochromatosis.
• Cardiac arrest.
• Hypo/hyperthermia

Question 2

What is a negative feedback system?

Answer 2

Used by the body to maintain a stable environment. It involves:
* Receptor/detector – a body structure that monitors the environment, detects any change and sends a message to a control centre
* Control centre – often the brain. Sets the range of values that are optimal, receives input from receptors and alerts effectors
* Effector – a body structure that receives information from the control centre and produces a response that aims to correct the imbalance. This could be almost any organ or tissue in the body.

Question 3

What is a positive feedback system?

Answer 3

• Much more rare in the human body.
• Whereas a negative feedback system reverses a change, a positive system reinforces a change.
• One example is childbirth – stretch receptors in the cervix are activated, this stimulates the brain to increase oxytocin production, which in turn stimulates further stretching of the cervix.

Question 4

When feedback loops go wrong- diabetes mellitus

Answer 4

• Normal blood sugar 4 – 7 mmol/L
• High blood sugar levels (hyperglycaemia) lead to tissue damage & long term complications.
• Low blood sugar levels (hypoglycaemia) leads to insufficient glucose to produce energy in the mitochondria. The brain can’t function without this energy

Question 5

What is an insulin dependent type 1 diabetes?

Answer 5

• Auto-immune disease, can develop at any age.
• Triad of characteristics: weight loss, polydipsia, polyuria.
• Body’s immune cells destroy beta cells in the islets of Langerhans in the pancreas – secrete glucagons and insulin. Together these control blood glucose levels.

Question 6

What is ketoacidosis?

Answer 6

• Absence of insulin – can’t facilitate the entry of glucose into cells.
• Cells use fatty acids to produce ATP instead. Triglycerides are broken down into fatty acids and glycerol.
• Progressive accumulation of the by-products of this – Ketones.
• Build up of ketones causes blood PH to fall – Ketoacidosis. Can quickly lead to death.