6.5 Notes Homeostasis

What is homeostasis? the process of maintaining the internal conditions of an organism between acceptable limits

Homeostasis in Humans What are some conditions need to be kept in homeostasis in humans? body temperature blood glucose concentration blood pH carbon dioxide concentration water availability

How does the human body react to low temperatures? thermoreceptors in hypothalamus activates warming mechanisms nerve impulses from hypothalamus trigger shivering which generates heat nerve impulses from hypothalamus trigger vasoconstriction of skin arterioles; this reduces blood flow to extremities –thereby minimizing heat loss through skin

How does the human body react to high temperatures? thermoreceptors in hypothalamus activates cooling mechanisms nerve impulses from hypothalamus trigger sweat glands and promotes evaporation/cooling nerve impulses from hypothalamus trigger vasodilation of skin arterioles; this increases blood flow to extremities thereby heat loss is increased through skin

How does the human body react to low blood sugar levels? pancreatic cells monitor blood glucose low glucose level induces production of glucagon glucagon stimulates the liver to break glycogen into glucose therefore blood glucose increases

How does the human body react to high blood sugar levels? pancreatic cells monitor blood glucose high level of blood glucose induces production of insulin insulin stimulates uptake of glucose into cells (muscles) insulin stimulates uptake of glucose into liver where it is stored as glycogen insulin leads to decrease in blood glucose blood glucose regulation is an example of negative feedback

Diabetes Type I diabetes Type 2 diabetes insulin-dependent diabetes people do not have the ability to produce insulin they must take insulin externally Type 2 diabetes non-insulin-dependent diabetes people can produce insulin but not in proper amounts can usually be controlled by diet or exercise much more common than Type I

IB Exam Question 1. Which process decreases when the human body temperature decreases? (1 mark) A. Blood flow to the internal organs B. Secretion of sweat C. Secretion of insulin D. Shivering Correct answer: B

IB Exam Question 2. Describe the response of the human body to low external temperatures. (4 marks) thermoreceptors in hypothalamus activates warming mechanisms nerve impulses from hypothalamus trigger shivering which generates heat nerve impulses from hypothalamus trigger vasoconstriction of skin arterioles; this reduces blood flow to extremities –thereby minimizing heat loss through skin

IB Exam Question 3. Describe the response of the human body to high external temperatures. (4 marks) thermoreceptors in hypothalamus activates cooling mechanisms nerve impulses from hypothalamus trigger sweat glands and promotes evaporation/cooling nerve impulses from hypothalamus trigger vasodilation of skin arterioles; this increases blood flow to extremities thereby heat loss is increased through skin

IB Exam Question 4. Explain how blood glucose concentration is controlled in humans. (8 marks) pancreatic cells monitor blood glucose; low glucose level induces production of glucagon; glucagon stimulates the liver to break glycogen into glucose; therefore blood glucose increases; high level of blood glucose induces production of insulin; insulin stimulates uptake of glucose into cells (muscles); insulin stimulates uptake of glucose into liver where it is stored as storage glycogen; insulin leads to decrease in blood glucose; blood glucose regulation is an example of negative feedback;