Hormones and homeostasis

Question 1

what are hormones

Answer 1

hormones are chemical substances, produced by a gland and carried by the blood, which alter the activity of one or more specific target organs. They play many roles, e.g. in homeostasis, growth, reproduction

Question 2

what are endocrine glands

Answer 2

ductless glands that secrete hormones directly into the blood. e.g. adrenal glands, pancreas, ovaries, testes, pituitary gland

Question 3

adrenal glands

Answer 3

hormone- adrenaline in ‘fight or flight’situations

Question 4

pancreas

Answer 4

hormones insulin and glucagon for regulation of blood glucose levels

Question 5

ovaries

Answer 5

oestrogen for developement of female secondary sexual characteristics, control of menstrual cycle of pregnancy

Question 6

testes

Answer 6

testosterone for development of male secondary sexual characteristics

Question 7

pituitary gland

Answer 7

hormones FSH, LH for control of menstrual cycle and pregnancy

Question 8

what is adrenaline

Answer 8

a hormone secreted in dangerous, ‘fight or flight’ situations. Has many target organs and it effects make us more able to react

Question 9

what effects does adrenaline have on the body

Answer 9

• pupil dialation
• faster and deeper breathing (more O2 supply + more CO2 removal)
• increased pulse rate (more O2 and glucose supply + more CO2 removal)
• increased blood glucose concentration (target: liver, which converts stored glycogen to glucose and releases it into the blood)

Question 10

what do adrenaline effects help with

Answer 10

these effects are to allow an increase in metabolic activity, e.g. muscles ín action’ needs to respire

Question 11

what happens when you are stressed

Answer 11

brain sends nerve impulses to adrenal glands which releases adrenaline into the blood

Question 12

what is homeostasis

Answer 12

the maintenance of a constant internal environment

Question 13

what is the control centre

Answer 13

the brain is the control centre: it monitors the blood flowing through it and if there is deviation from the optimal (e.g. blood too hot), it instructs the respective organ to correct it.

Question 14

what is negative feedback

Answer 14

it is a system of control in which a change triggers responses that counteract the change. i.e. if the level of something rises, the control systems reduce it again. -if the level of something falls, the control systems raise it again.
e.g. if temperature rises, the brain instructs the skin to respond so that the temperature drops.

Question 15

what happens when blood glucose increases

Answer 15

when blood glucose increases, pancreas secretes insulin and the liver takes up excess glucose and converts it into glycogen for storage (and other cells take up glucose for respiration) and the blood glucose decreases

Question 16

what happens when blood glucose decreases

Answer 16

when blood glucose decreases the pancreas secretes glucagon and the liver converts glycogen to glucose and release it into the blood and blood glucose increases

Question 17

what are symptoms of diabetes

Answer 17

• high blood glucose levels
• glucose detected in urine
• thirst, frequent urination, weight loss

Question 18

what is the cause of type 1 diabetes

Answer 18

results from failure to produce insulin autoimmune disease– the immune system destroys beta cells of the pancreas which produce insulin

Question 19

what is the treatment of type 1 diabetes

Answer 19

insulin injections, regulated diet and exercise

Question 20

how does the body lose and gain heat

Answer 20

loses heat: through the skin by conduction, convection, radiation and evaporation
gains heat internally from respiration and externally from the surroundings

Question 21

what does the skin contain

Answer 21

the skin is the main organ in heat loss/ gain.
It has the sweat pore, sweat duct, sweat gland, fat adipose tissue (for insulation), arteriole, venule, hair, hair erector muscles (contracts to raise hair), sensory neuron, dermis, capillaries, receptor and epidermis (cells produce melanin to protect from UV light)

Question 22

how is the maintenance of body temperature detected

Answer 22

receptors in the brain detect changes in blood temperature and coordinate response

Question 23

what happens when you are overheating

Answer 23

• vasodilation : shunt vessel constricts, arterioles in the dermis dilate, thus more blood flows through capillaries near the surface, thus more heat is lost
• sweating: sweat glands secrete sweat on the skin surface. when the water evaporates it takes heat from the body
• hairs lie flat so heat can escape

Question 24

what happens when you are overcooling

Answer 24

• vasoconstriction: arterioles in the dermis narrow and the shunt vessel dilates, thus less blood flow through capillaries near the surface, thus less heat is lost
• sweating stops
• hairs erect and trap air
• shivering : uncontrollable rapid muscular contraction in the limbs releases heat as a result of respiration