chap9: homeostasis & hormonal control

Question 1

what is homeostasis

Answer 1

the maintenance of a constant internal environment

Question 2

what is negative feedback

Answer 2

a corrective mechanism where the body detects a change away from the normal condition and causes a change back towards the normal condition

Question 3

what happens when blood glucose concentration increases above normal

Answer 3

islets of langerhans in the pancreas is stimulated and produces more insulin to secrete into the blood. the insulin stimulates the liver to convert excess glucose into the glycogen for storage in the liver. this decreases the blood glucose concentration back to normal

Question 4

what happens when blood glucose concentration decreases above normal

Answer 4

the islets of langerhans in the pancreas is stimulated to produce and secrete more glucagon into the blood. glucagon stimulates the liver to convert glycogen into glucose which is released into the blood. this increases the blood glucose concentration back to normal

Question 5

effect of normal insulin levels

Answer 5

makes cell membrane more permeable to glucose, allowing more glucose to diffuse into liver and muscle cells
stimulates the liver and muscle cells to convert glucose to glucagon for storage
increases the use of glucose for respiration

Question 6

effect of low insulin levels

Answer 6

glucose cannot be stored or utilised by tissue cells
muscles have no reserve of glycogen, the body grows weak and loses weight

Question 7

effect of high levels of insulin

Answer 7

low blood glucose concentration
results in fits, shocks, passing out

Question 8

purpose of glucagon

Answer 8

converts glucose into glycogen
converts fats and amino acids into glucose

Question 9

what is type 1 diabetes

Answer 9

develops early in a person’s life
occurs when the islets of langerhans are unable to produce sufficient insulin
can be inherited

Question 10

what is type 2 diabetes

Answer 10

occurs later in a person’s life
overweight people are more susceptible to developing
occurs when target cells like muscle cells do not respond well to insulin

Question 11

what is type 2 diabetes

Answer 11

occurs later in a person’s life
overweight people are more susceptible to developing
insulin resistant: occurs when target cells like muscle cells do not respond well to insulin

Question 12

how is type 1 diabetes treated

Answer 12

insulin injections

Question 13

how is type 2 diabetes treated

Answer 13

oral medication
control of dietary intake
exercise

Question 14

what are risk factors to type 2 diabetes

Answer 14

obesity
high lipid levels
inactive lifetstyle
ageing
family history

Question 15

what is a hormone

Answer 15

hormones are chemical substances produced in small quantities by exocrine glands that are transports in the bloodstream to target organs where it exerts its effects

Question 16

what are exocrine glands

Answer 16

exo = outwards
they have a duct/tube to carry away their secretions
eg. salivary gland -> salivary duct -> saliva -> mouth
sweat gland -> sweat duct -> sweat -> out of body

Question 17

what are endocrine glands

Answer 17

endo = within
they are ductless glands and secrete hormones directly into the bloodstream which then distributes the hormone around the body
eg. pituitary gland -> ADH

Question 18

what organ is considered both an exocrine and endocrine gland, why?

Answer 18

the pancreas is considered an exocrine gland as it produces pancreatic juice which is carried by the pancreatic duct to the duodenum
the pancreas is also considered an endocrine gland as it contains islets of Langerhans which secreates insulin and glucagon into the bloodstream

Question 19

what affects body temperature

Answer 19

the environment, change in temperature, time of day, weather
human behaviour

Question 20

how is the skin adapted for temperature regulation

Question 21

how do blood vessels help to regulate body temperature

Answer 21

the constriction and dilation of arterioles are caused by the contraction and relaxation of muscles in the arterioles walls, this helps to regulate body temperature
vasodilation is the dilation of the arterioles which sends blood to the blood capillaries in the skin.
vasoconstriction is the constriction of the arterioles in the skin which reduces the amount of blood flowing through the the capillaries in the skin

Question 22

how do sweat glands help regulate body temperature

Answer 22

secreted sweat flows through a sweat duct and to a sweat pore that opens up on the skins surface. secreted sweat is made out of water and excretory products like urea and dissolved salts. when swear is excreted, heat in the surrounding causes it to evaporate and hence cooling down the surface of the skin

Question 23

how do thermoreceptors help to regulate body temperature

Answer 23

thermoreceptors help detect change in the temperature

Question 24

how is heat gained in the body

Answer 24

heat is released when metabolic activities take place like cellular respiration
vigorous muscular exercise, consumption of hot food, being in warm environments

Question 25

how is heat lost by the body

Answer 25

through the skin
evaporation of water ins went from surface of the skin
faeces and urine
in the air that is exhaled

Question 26

what happens when body temperature rises above normal

Answer 26

thermoreceptors in the skin and the hypothalamus in the brain is stimulated. the arterioles in the skin becomes more dilated and more blood can flow through blood capillaries in the skin to increase heat lost through the skin. sweat glands become more active and produce a larger volume of sweat to be excreted on the surface of the skin. more sweat is being evaporated and more heat is lost. metabolic rate is decreased which reduces the amount of heat released within the body. body returns to normal temperature.

Question 27

what happens when body temperature falls below normal

Answer 27

thermoreceptors in the skin and hypothalamus in the brain is stimulated. arterioles in the skin constricts and lesser blood can flow through the blood capillaries in the skin, this reduces heat lost from the skin to the environment. sweat glands become less active and produce less sweat to evaporate from the skin surface, hence conserving heat. metabolic rate speeds up which increases body temperature. shivering is the rapid contraction and relaxation of the skeletal muscles which increases the amount of heat released. this brings the body temperature back to normal.