Lecture 10: Homeostasis Flashcards
Homeostasis:
Any self-regulating process by which biological systems tend to maintain stability while adjusting to conditions that are optimal for survival
homeostasis steady state =
- Maintenance of internal balance
* Internal systems & external environment interact with each other dynamically/continuously
homeostatic mechanisms have 3 functional components:
- 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)
regulatory mechanisms work by:
Feedback
Feedback =
return of output to the input part of the system
–The response of the effector therefore influences the
subsequent output by the effector
two types of feedback
- & +
negative feedback =
activity of effectors oppose any deviation of the
controlled variable from the regulated level e.g. Temperature regulation
positive feedback =
activity of effectors enhance deviation. Rare and always part of larger negative feedback system e.g. blood clotting
doping =
the use of performance enhancing drugs (PEDs)
reasons to use PEDs
– Build muscle mass and strength
– Increase O2 delivery to exercising tissue – Mask pain/injury
– Decrease weight
– Hide use of other drugs
examples of PEDs
− Anabolic (metabolic synthesis) steroids
− Human Growth Hormone (HGH)
− Erythropoietin (EPO)
–Inc. O2 delivery
− Diuretics – weight loss and hide drug use
Anabolic (metabolic synthesis) steroids :
- 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
Steroids:
- derived from cholesterol
- Natural steroids = e.g. testosterone (Tes) in males, oestrogen in females
- synthetic hormones mimic testosterone; injected or swallowed
Testosterone:
- 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
Side effects to testosterone:
- 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
Human growth hormone (HGH) natural;
- naturally occurring protein
- produced by pituitary gland
- functions in normal human growth & development
- stimulates bone & muscle growth & Decreases body fat
epiphysis:
the cap at the end of a long bone that develops from a secondary ossification centre
Diaphysis:
the shaft of a long bone
HGH synthetic bone:
- 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)
side effects of HGH:
– 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
Increasing O2 in tissues; EPO Erythropoietin
• Negative feedback control
− Drop in RBC causes hypoxaemia to kidneys
− EPO production ↑ bone marrow is stimulated
− RBC ↑s in 3-4 days
stimulus for erythropoiesis
− Low atmospheric O2
− ↑ in exercise
− Haemorrhaging
synthetic EPO effect:
- ↑ O2 supply by 7-10%
- Injected – synthetic but also gene therapy
is EPO possible to detect?
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
side effects of EPO:
“thickens” the blood, so blood doesn’t flow as well through blood vessels, so heart has to work harder
how to hide drug use:
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
side effects to diuretics
- dehydration
- cramps (loss of salt ions)
- heart damage & kidney failure
doping to increase athletic performance is based on
physiology
why do we have side effectts to doping?
body is trying to get back to a steady state (homeostasis)
