Week 4 - Homeostasis

Question 1

homeostasis

Answer 1

maintaining the body’s internal environment for the proper functioning of the human body

Question 2

conditions for homeostasis

Answer 2

1. proper concentration of gases (eg. O2, CO2), nutrients (eg. glucose), salts (eg. NaCl), water
2. optimum temperature (37*)
3. optimum pressure (eg. blood pressure)

Question 3

stress

Answer 3

any stimulus that causes an imbalance in the internal environment

Question 4

feedback loop

Answer 4

a circular situation where the status of a body condition is monitored and then reported back to a control centre which causes an action that changes the status

Question 5

negative feedback

Answer 5

used by most systems in the body; a circular loop where a particular body condition is constantly monitored to ensure homeostasis is maintained; the output is the opposite of the input

Question 6

when blood pressure rises

Answer 6

1. homeostasis is disrupted by an increase in blood pressure
2. stretch receptors called baroreceptors in certain blood vessels detect change in blood pressure, and sends a message to the brain (cardiovascular centre of the medulla oblongata)
3. the brain processes the message, and sends a message to the effectors which are the heart to slow down heart rate and blood vessels to vasodilate
4. heart and blood vessels respond to the message
5. as a result, blood pressure decreases

Question 7

when it gets too cold

Answer 7

1. input - too cold
2. sensor - cold thermoreceptors
3. control centre - hypothalamus
4. effectors - contraction of skeletal muscles (shivering), vasoconstriction, release of hormones (to increase thermogenesis), increase in muscle tone
5. output - warm up

Question 8

when it gets too hot

Answer 8

1. input - too hot
2. sensor - warm thermoreceptors
3. control centre - hypothalamus
4. effectors - release of sweat by sweat glands, vasodilation, fewer hormones released (decrease thermogenesis), decrease in muscle tone
5. output - cool down

Question 9

positive feedback

Answer 9

a condition where the output is stronger, more amplified than the input; very few normal systems in the body use positive feedback

Question 10

positive feedback - childbirth

Answer 10

1. during labour, the baby’s head pushes against the cervix
2. stretch receptors in the cervix detect the stretching and send a message to the brain
3. the brain receives the signal and releases a hormone called oxytocin (made by hypothalamus and released by posterior pituitary gland)
4. oxytocin acts on the uterus and causes sit t o contract more forcefully
5. baby’s head pushes against the cervix more