Lecture 10: Homeostasis

Question 1

Homeostasis:

Answer 1

Any self-regulating process by which biological systems tend to maintain stability while adjusting to conditions that are optimal for survival

Question 2

homeostasis steady state =

Answer 2

• Maintenance of internal balance

* Internal systems & external environment interact with each other dynamically/continuously

Question 3

homeostatic mechanisms have 3 functional components:

Answer 3

• Receptor: takes in sensory information
• Control centre: Determines the “set point” and regulates the body’s response
• Effector: carries out the body’s response
• (Variable: a factors in the body that can be modified by the effector)

Question 4

regulatory mechanisms work by:

Answer 4

Feedback

Question 5

Feedback =

Answer 5

return of output to the input part of the system
–The response of the effector therefore influences the
subsequent output by the effector

Question 6

two types of feedback

Answer 6

• & +

Question 7

negative feedback =

Answer 7

activity of effectors oppose any deviation of the

controlled variable from the regulated level e.g. Temperature regulation

Question 8

positive feedback =

Answer 8

activity of effectors enhance deviation. Rare and always part of larger negative feedback system e.g. blood clotting

Question 9

doping =

Answer 9

the use of performance enhancing drugs (PEDs)

Question 10

reasons to use PEDs

Answer 10

– Build muscle mass and strength
– Increase O2 delivery to exercising tissue – Mask pain/injury
– Decrease weight
– Hide use of other drugs

Question 11

examples of PEDs

Answer 11

− Anabolic (metabolic synthesis) steroids
− Human Growth Hormone (HGH)
− Erythropoietin (EPO)
–Inc. O2 delivery
− Diuretics – weight loss and hide drug use

Question 12

Anabolic (metabolic synthesis) steroids :

Answer 12

• stimulates muscle & bone cells (hypertrophy) to make new protein by changing gene expression
• Also makes more myonuclei in muscle fibres which increases protein synthesis capacity of cells

Question 13

Steroids:

Answer 13

• derived from cholesterol
• Natural steroids = e.g. testosterone (Tes) in males, oestrogen in females
• synthetic hormones mimic testosterone; injected or swallowed

Question 14

Testosterone:

Answer 14

• causes male reproductive & secondary sex traits
• Test is a ratio; Tes: epitestosterone; should normally be 1:1; anything 4:1 is WADA illegal
• avoid detection by injecting epitestosterone

Question 15

Side effects to testosterone:

Answer 15

• males = baldness, infertility through shrivelled testes
• females = facial/body hair, suppress menstrual cycle, thicken vocal cords
• General: increased risk of heart disease, liver cancer, kidney damage, personality disorders

Question 16

Human growth hormone (HGH) natural;

Answer 16

• naturally occurring protein
• produced by pituitary gland
• functions in normal human growth & development
• stimulates bone & muscle growth & Decreases body fat

Question 17

epiphysis:

Answer 17

the cap at the end of a long bone that develops from a secondary ossification centre

Question 18

Diaphysis:

Answer 18

the shaft of a long bone

Question 19

HGH synthetic bone:

Answer 19

• Synthetic form (or from cadavers) is injected and looks exactly like natural protein
• But this is the major isoform; actually the body produces another isoform
• Now WADA uses the two isoform ratio blood test which only detects within about 2 days of doping and can only detect synthetic (not cadaver)

Question 20

side effects of HGH:

Answer 20

– Type I diabetes
– Acromegaly (overgrowth of hands, feet and face)
– Enlarged internal organs (heart, kidney, tongue, liver)
– Heart problems
– Kidney failure with long term use

Question 21

Increasing O2 in tissues; EPO Erythropoietin

Answer 21

• Negative feedback control
− Drop in RBC causes hypoxaemia to kidneys
− EPO production ↑ bone marrow is stimulated
− RBC ↑s in 3-4 days

Question 22

stimulus for erythropoiesis

Answer 22

− Low atmospheric O2
− ↑ in exercise
− Haemorrhaging

Question 23

synthetic EPO effect:

Answer 23

• ↑ O2 supply by 7-10%

- Injected – synthetic but also gene therapy

Question 24

is EPO possible to detect?

Answer 24

Yes, but an “arms race”
– Frequent testing of athletes to keep track of nine key blood characteristics
– If red blood cells is higher during competition e.g. 50% compared to 46%, then indicates doping

Question 25

side effects of EPO:

Answer 25

“thickens” the blood, so blood doesn’t flow as well through blood vessels, so heart has to work harder

Question 26

how to hide drug use:

Answer 26

Diuretics
e.g. caffeine, alcohol
Acts on kidney to increase urine flow
• Pills – commonly hydrochlorothiazide (used in medicine to treat high blood pressure)
• Detected via liquid chromatography or mass spectrometry but most commonly used ones have short half life of 24-48 hours

Question 27

side effects to diuretics

Answer 27

• dehydration
• cramps (loss of salt ions)
• heart damage & kidney failure

Question 28

doping to increase athletic performance is based on

Answer 28

physiology

Question 29

why do we have side effectts to doping?

Answer 29

body is trying to get back to a steady state (homeostasis)