Regulation and Control
Homeostasis
Objectives:
outline the need for communication systems within mammals to respond to changes
in the internal and external environment
Learning Activity
Prepare a presentation using text book or internet on any one of the following in 10
mins:
organisation of multicellular organisms, internal changes, changes in external
environment, endocrine, nervous system, reflexes. Negative feedback
Present your ideas in five minutes
BRAIN
RIGHT LUNG
PITUITARY GLAND
RIBS
INTERCOSTAL MUSCLE
HEART
DIAPHRAGM
STOMACH
PANCREAS
SKIN
KIDNEY
BLADDER
Control of a possible football situation
RISU are trailing 1-0 to ISU in the final of the Rainbow Cup. All of a
sudden (student A) pulls up with a suspected torn hamstring. (Student B)
spots this and immediately sends a message to Mr Colley what happens.
Mr Colley makes a decision. He decides to replace (student A) with
(Student C). Student C went on to score a hatrick.
Final Score RISU 3 ISU 4
What was the problem (stimulus)?
Who detected it?
Who was the decision maker is the system?
What was the response?
Body Temperature Control
Increased body
temperature eg when
exercising
HIGH
Homeostasis: Body Temperature
LOW
Decreased body
temperature eg due to
cold surroundings
Regulation of Body Temperature
Put the statements below in the correct boxes on the other side of the page:
Brain detects DECREASE in blood temperature.
Capillaries widen (VASODILATION). Heat radiates from skin.
Capillaries narrow (VASOCONSTRICTION). Reduces heat loss from
skin.
Body temperature decreases. Cooling mechanisms shut down.
Shivering generates heat.
Brain detects RISE in blood temperature.
Evaporation of sweat cools body.
Body temperature increases. Warming mechanisms shut down
Effects of Hot and Cold on the Skin
Heat lost by Radiation
Evaporation of the sweat
cools the skin
Very little heat lost by
radiation
Sweating Stops
Sweat
Gland
Hot Weather
Sweat
Gland
Blood Vessels Widen
Blood Vessels Narrow
VASODILATION
VASOCONSTRICTION
Cold Weather
Control of Blood Glucose
Objectives:
describe the cellular structure of an islet of Langerhans from the pancreas and outline
the role of the pancreas as an endocrine gland;
explain how the blood glucose concentration is regulated by negative feedback control
mechanisms, with reference to insulin and glucagon
Regulation of Body Temperature
Put the statements below in the correct boxes on the other side of the page:
Brain detects DECREASE in blood temperature.
Capillaries widen (VASODILATION). Heat radiates from skin.
Capillaries narrow (VASOCONSTRICTION). Reduces heat loss from skin.
Body temperature decreases. Cooling mechanisms shut down.
Shivering generates heat.
Brain detects RISE in blood temperature.
Evaporation of sweat cools body.
Body temperature increases. Warming mechanisms shut down.
What happens after we eat?
Insulin Control
Islet of langerhans
• Beta cells have channels in the
plasma membrane that serve as
glucose detector. They secrete a
small protein hormone insulin
(polypeptide of 21 amino acids
• They stimulate skeletal muscles,
liver cells, fat cells to convert
glucose to glycogen (glycogenesis)
• They stimulate the hypothalamus to
reduce appetite.
• Taken together, all of these actions
result in:
• the storage of the soluble nutrients
absorbed from the intestine into an
insoluble product (glycogen)
• a drop in the level of blood sugar
• Alpha cells of the islets situated on the outer
rim of the islet secrete GLUCAGON, also a
protein hormone of 29 amino acids
• Glucagon acts principally on the liver
• Glucagon secretion is stimulated by low levels
of glucose in the blood and
• inhibited by high levels.
•
• In the liver it stimulates the conversion of
glycogen into glucose which is deposited in
the blood. (glycogenolysis)
•
(a)
Describe how the level of blood glucose in a human
is maintained at a constant level by hormones with
reference to the source of the hormones involved
What happens when insulin is not
produced?
• Diabetes is a disease where the
concentration of glucose in the blood is not
controlled properly by the body.
• In type 1 diabetes, the pancreas does not
produce enough insulin. This can lead to high
levels of glucose in the blood, which can be
fatal.
Too much insulin can also be harmful.
Cells of Islets of Langerhans
1. Name the cells of Islet of Langerhans
2. State their roles in homeostasis and their
structural differences
Diabetes mellitus
Homework:
Research and make notes on different diabetes and
how they are controlled