Chapter 12 - Homeostasis

Question 1

Define homeostasis.

Answer 1

Maintenance of a constant internal environment.

Question 2

Define negative feedback.

Answer 2

𝘈𝘶𝘵𝘰𝘮𝘢𝘵𝘪𝘤 response, triggered by a change in level of internal environment, to restore the original level.

Question 3

Define hormone.

Answer 3

A chemical substance produced by an endocrine gland, transported in the 𝘣𝘭𝘰𝘰𝘥 𝘱𝘭𝘢𝘴𝘮𝘢 to alter the activity of one or more target organs, and is 𝘥𝘦𝘴𝘵𝘳𝘰𝘺𝘦𝘥 in the liver then 𝘦𝘹𝘤𝘳𝘦𝘵𝘦𝘥 in kidney.

Question 4

What happens when the surrounding temperature/blood temperature increases?

Answer 4

(Receptor) Hypothalamus detects/Thermoreceptors in skin

(Stimulus) Rise in blood temperature above normal levels/Rise in skin temperature

(Control Centre) Hypothalamus stimulates the

(Corrective Mechanism)
Decreasing heat production:
Metabolic rate decreases to reduce amount of heat 𝘳𝘦𝘭𝘦𝘢𝘴𝘦𝘥 𝘸𝘪𝘵𝘩𝘪𝘯 𝘵𝘩𝘦 𝘣𝘰𝘥𝘺.

Increasing heat loss:
Arterioles 𝘪𝘯 𝘴𝘬𝘪𝘯 dilates (vasodilation) and shunt vessel constrict to allow more blood to flow 𝘵𝘩𝘳𝘰𝘶𝘨𝘩 𝘣𝘭𝘰𝘰𝘥 𝘤𝘢𝘱𝘪𝘭𝘭𝘢𝘳𝘪𝘦𝘴 𝘯𝘦𝘢𝘳 𝘵𝘩𝘦 𝘴𝘬𝘪𝘯 𝘴𝘶𝘳𝘧𝘢𝘤𝘦. More heat is lost 𝘵𝘩𝘳𝘰𝘶𝘨𝘩 𝘵𝘩𝘦 𝘴𝘬𝘪𝘯 by conduction, convection and radiation.
Sweat glands become more active and more sweat is produced. More 𝘸𝘢𝘵𝘦𝘳 𝘪𝘯 𝘴𝘸𝘦𝘢𝘵 evaporates from skin surface, more 𝘭𝘢𝘵𝘦𝘯𝘵 𝘩𝘦𝘢𝘵 is lost from body.

Question 5

Another way of increasing heat production other than increasing metabolic rates?

Answer 5

Shivering, a reflex muscle contraction of skeletal muscle. This spasmodic contraction of skeletal muscles increases amount of heat released within the body.

Question 6

What happens when blood glucose concentration rises above normal?

Answer 6

(Receptor) Islet of Langerhans detects

(Stimulus) rise in blood glucose concentration above normal

(Control Centre) Islets of Langerhans in the pancreas

(Corrective Mechanism)
Increases secretion of insulin into bloodstream to be 𝘵𝘳𝘢𝘯𝘴𝘱𝘰𝘳𝘵𝘦𝘥 𝘣𝘺 𝘣𝘭𝘰𝘰𝘥 𝘱𝘭𝘢𝘴𝘮𝘢.
Insulin increases permeability of cell membrane to glucose, increasing rate of glucose uptake by cells.
Insulin stimulates liver and muscles to convert 𝘦𝘹𝘤𝘦𝘴𝘴 glucose to glycogen 𝘧𝘰𝘳 𝘴𝘵𝘰𝘳𝘢𝘨𝘦.
Insulin increases oxidation of glucose during tissue respiration.
𝘚𝘦𝘤𝘳𝘦𝘵𝘪𝘰𝘯 𝘰𝘧 𝘪𝘯𝘴𝘶𝘭𝘪𝘯 𝘳𝘦𝘥𝘶𝘤𝘦𝘴 𝘰𝘯𝘤𝘦 𝘣𝘭𝘰𝘰𝘥 𝘨𝘭𝘶𝘤𝘰𝘴𝘦 𝘤𝘰𝘯𝘤𝘦𝘯𝘵𝘳𝘢𝘵𝘪𝘰𝘯 𝘳𝘦𝘵𝘶𝘳𝘯𝘴 𝘵𝘰 𝘯𝘰𝘳𝘮𝘢𝘭.

Question 7

What happens when blood glucose concentration drops below normal?

Answer 7

(Receptor) Islet of Langerhans detects

(Stimulus) drop in blood glucose concentration below normal

(Control Centre) Islets of Langerhans in the pancreas

(Corrective Mechanism)
Increases secretion of glucagon into bloodstream to be 𝘵𝘳𝘢𝘯𝘴𝘱𝘰𝘳𝘵𝘦𝘥 𝘣𝘺 𝘣𝘭𝘰𝘰𝘥 𝘱𝘭𝘢𝘴𝘮𝘢.
Glucagon stimulates liver to convert stored glycogen to glucose and 𝘳𝘦𝘭𝘦𝘢𝘴𝘦𝘴 glucose molecules into bloodstream
𝘚𝘦𝘤𝘳𝘦𝘵𝘪𝘰𝘯 𝘰𝘧 𝘨𝘭𝘶𝘤𝘢𝘨𝘰𝘯 𝘳𝘦𝘥𝘶𝘤𝘦𝘴 𝘰𝘯𝘤𝘦 𝘣𝘭𝘰𝘰𝘥 𝘨𝘭𝘶𝘤𝘰𝘴𝘦 𝘤𝘰𝘯𝘤𝘦𝘯𝘵𝘳𝘢𝘵𝘪𝘰𝘯 𝘳𝘦𝘵𝘶𝘳𝘯𝘴 𝘵𝘰 𝘯𝘰𝘳𝘮𝘢𝘭

Question 8

What happens when blood water potential drops below normal?

Answer 8

(Receptor) Hypothalamus in brain detects

(Stimulus) drop in blood water potential below normal

(Control Centre) Hypothalamus in brain stimulates pituitary gland to

(Corrective Mechanism) Increase secretion of anti-diuretic hormones into bloodstream to transported by blood plasma.
Cells in wall of 𝘥𝘪𝘴𝘵𝘢𝘭 𝘤𝘰𝘯𝘷𝘶𝘭𝘢𝘵𝘦𝘥 𝘵𝘶𝘣𝘶𝘭𝘦 𝘢𝘯𝘥 𝘤𝘰𝘭𝘭𝘦𝘤𝘵𝘪𝘯𝘨 𝘥𝘶𝘤𝘵 become more permeable to water.
More water reabsorbed into bloodstream 𝘣𝘺 𝘰𝘴𝘮𝘰𝘴𝘪𝘴.