7B Electrical Activity in the Heart, Homeostasis and Sport

Question 1

respiratory minute ventilation / ventilation rate (per min)

Answer 1

tidal vol x breathing rate (breaths per min)

Question 2

tidal volume

Answer 2

vol air in each breath (~0.4 dm³)

Question 3

oxygen consumption

Answer 3

vol O₂ used by body (usually rate)

find change in vol of gas in spirometer (as O₂ used for respiration)

Question 4

breathing rate

Answer 4

count no. peaks in spirometer trace per min

Question 5

design an experiment to investigate ventilation in humans

Answer 5

use spirometer

-> gives reading of tidal volume
-> use to find breathing rate, O₂ consumption and resp min vol

1. canister containing soda lime (absorbs CO₂ that subject exhales) inserted between mouthpiece and floating chamber
2. after calibration, spirometer filled with O₂ with tube connected to O₂ chamber
3. subject breathes into tube for 1 min -> as they breathe in = lid of chamber moves down and vice versa
4. movements of lid recorded by pen attached to lid -> writes on rotating drum = makes SPIROMETER TRACE
5. subject then exercises for 2 mins and spirometer chamber refilled with O₂ (used up in respiration -> vol gas in chamber ↓ over time)
6. immediately after stopping exercise -> breathe into spirometer again for 1 min
7. spirometer trace before and after exercise recorded

Question 6

cardiac output

Answer 6

heart rate (bpm) x stroke vol (cm³)

cm³ min⁻¹

Question 7

state diff in fast and slow twitch muscle fibres, including structural and physiological diff

Answer 7

• fast twitch contract quickly whereas slow contract slowly
• fast used for fast movement (mainly in eyes and legs) whereas slow used for slow movement (posture - in back)
• fast good for short bursts of speed/power (sprint) whereas slow good for endurance activities (long distance)
• fast get tired quickly whereas slow is opp
• fast energy released quickly through anaerobic resp using glycogen (↓ mitochondria) whereas slow energy released slowly through aerobic resp (↑ mitochondria) and blood vessels supply O₂
• fast are white (not much myoglobin -> so can’t store much O₂) whereas slow are pink (rich in myoglobin -> red coloured protein that supplies O₂)

Question 8

examples of performance enhancing drugs and their diff effects on the body

Answer 8

• anabolic steroids -> ↑ strength, speed + stamina by ↑ muscle size + allowing athlete to train harder . ↑ aggression
• stimulants -> speed up reactions, ↓ fatigue + ↑ aggression
• narcotic analgesics -> ↓ pain so injuries don’t affect performance

Question 9

discuss whether use of performance enhancing drugs by athletes is acceptable

Answer 9

absolutist:

• some drugs are illegal
• competition becomes unfair -> ppl get adv by taking drugs nit working hard
• serious health risks -> ↑ b.p, heart problems
• athletes not fully informed of health risks of drugs they take

rationalist:

• up to each individ. -> have right to make their own decision, whether its worth the risk etc
• drug-free sport isnt fair anyway -> diff athletes have diff equipment, training access -> use of drugs might overcome these inequalities
• athletes that want to compete at higher level may only be able to using drugs

Question 10

adv of keyhole surgery

Answer 10

• doesnt involve opening patients up as much -> lose less blood + less scarring
• less pain caused after + recover faster as less damage done
• so easier for patient to return to normal activities + hospital stay shorter

Question 11

describe how damaged cruciate ligaments can be fixed by keyhole surgery

(2 marks)

Answer 11

• crucviate ligament found in middle of knee, connects thigh bone to lower leg bone
• damaged cruciate ligament removed + replaced with graft
• graft usually from tendon in patients leg (or from donor)

Question 12

prosthesis

Answer 12

artificial device to replace damaged or missing body parts

Question 13

describe how prostheses enable ppl with damaged knee joints to participate in sport

Answer 13

• metal device inserted into knee to replace damaged cartilage + bone
• knee joint + ends of leg bones replaced to provide smooth knee joint
• cushioning in new joint helps ↓ impact on knee
• knee joint replacement allows ppl to participate in low impact sports

Question 14

explain why it is important to have stable internal conditions in the human body

Answer 14

• intracellular enzymes: fragile
• pH affects molecular structure (H-bonds disrupted + charge distrib. on active site changes)
• temp affects proteins -> rate of reactions + stability of shape affected
• water potential -> could cause swelling / shrinking of cells

Question 15

negative feedback

Answer 15

• mechanism that restores level of normal
• effectors respond to counteract change + bring level back to normal

Question 16

positive feedback

Answer 16

mechanism that amplifies change from normal level

• useful to rapidly activate smt eg. blood clot after injury
• also happens when homeostatic system breaks down eg. too cold for too long (hypothermia)
• isnt involved in homeostasis as doesn’t keep internal env stable