Chapter 9: Homeostasis: A Fine Balance

Question 1

Negative feedback

Answer 1

It’s when a system reacts to a change by doing the opposite to bring things back to normal or balance. It helps keep everything stable.

Body Temperature – If you get too hot, you sweat to cool down. If you get too cold, you shiver to warm up, bringing your body temperature back to normal.

Question 2

Positive feeback

Answer 2

It’s when a change in a system causes a response that makes the change stronger or bigger. It keeps going in the same direction, pushing past normal limits.

Childbirth – When the baby pushes on the cervix, it causes more contractions, which push the baby more, until the baby is born.

Question 3

Use a practical example to describe negative feedback – stimulus, sensor, integrator, effector, response

Thermostat

Answer 3

• An example of a negative feedback system is a home thermostat, the stimulus is the warm air, which tells the sensor in the thermostat to reduce the heating, the thermostat sends a signal to the heating system (thermom) which makes action to stop heating.
• Stimulus- hot air
• Sensor- thermostat thermometer
• Integrator- thermostat
• Effector- furnace
• Response- stopping heating

Question 4

Formation of urine (reabsorption).

Answer 4

• Useful substances (water, Na+, K+, glucose, amino acids) are taken back into the blood.
• Water is reabsorbed by osmosis in the Loop of Henle and collecting duct.
• This process happens in the proximal tubule, loop of Henle, distal tubule, and collecting duct.

Question 5

Formation of urine (Secretion).

Answer 5

• Wastes like H+, K+, ammonia, and drugs are added to the filtrate from the blood.
• This happens in the proximal tubule, distal tubule, and collecting duct.

Question 6

Formation of urine (filtration).

Answer 6

• Happens in the glomerulus.
• High blood pressure pushes water, ions, glucose, amino acids, and waste (like urea) into Bowman’s capsule.
• Large particles like proteins are too big to pass the glomerulus

Question 7

Define deamination. What is the byproduct of deamination?

Answer 7

• Deamination occurs in the liver, where an amino group (NH₂) is removed from amino acids.
• This process produces ammonia (NH₃) as a toxic byproduct.
• To make it less toxic, the liver converts ammonia into urea through the urea cycle. Urea is then excreted from the body via urine.
• Keto acids: These are the carbon skeletons of amino acids, which can be used for energy production.