Topic 7: Homeostasis and Exercise Flashcards
Explain the role of the brain in reducing heart rate after exercise (2)
-Chemoreceptors detect a change in carbon dioxide / PH
-The cardiovascular control centre receives impulses from the chemoreceptors / sends impulses to the heart
-Therefore impulses are transmitted along the parasympathetic nerve to the SAN reducing heart rate
Describe how the brain reduces the activity of the sweat glands after the exercise (2)
-Thermoreceptors detect a decrease in temperature
-Hypothalamus / thermoregulatory centre sends fewer impulses to sweat glands
Explain how the respiratory centre is involved in the control of ventilation rate after exercise (5)
-High CO2 in the blood stimulates the respiratory centre
-Increase in lactate / fall in PH stimulates the respiratory centre
-More impulses send to the diaphragm and intercostal muscles
-Resulting in an increase in the rate and depth of breathing
-PH returns to normal as CO2 is removed and ventilation rate decreases
Heat stress occurs when the core body temperature raises above 40C
Describe how thermoregulatory mechanisms are controlled to help marathon runners avoid heat stress (4)
-Thermoreceptors in the hypothalamus or skin detect increase in temperature
-Impulses sent to thermoregulatory centre in hypothalamus
-Hypothalamus sends impulses (action potentials) to sweat glands
-Increases blood flow to surface of skin by vasodilation
-Decreases metabolic rate
Explain the role of the nervous system in bringing about the increase in temperature of the body (5)
-Thermoreceptors in the skin detect and increase in temperature
-Thermoreceptors in the hypothalamus detect temperature increase
-Therefore more impulses are sent along the sympathetic nerves / nervous system
-Which leads to constriction of shunt vessels
-Therefore causing vasodilation of arterioles
-Causing more blood to flow near the skin surface
Sweating is a thermoregulatory mechanism
A student concludes that loss of heat when sweating is related to the dipole nature of water molecules
Justify this statement (3)
-Water has an uneven distribution of charge, making it dipole
-So water forms hydrogen bonds with other water molecules
-And it requires a lot of thermal energy to break these bonds
-And allow water to evaporate taking he heat energy with it
Explain the importance of the dipole nature of water in sweating (2)
-Dipole nature allows water molecules to form hydrogen bonds / bonds with each other
-Heat energy is used to break bonds between water molecules
-Evaporation of water cause cooling / removal of heat
Describe how the production of sweat is controlled during exercise in humans (4)
-By homeostasis / a negative feedback response
-Thermoreceptors in the skin / hypothalamus detect a rise in temperature
-Send impulses to the thermoregulatory centre / hypothalamus
-Thermoregulatory centre / hypothalamus sends impulses to the sweat glands
-To increase sweat production
Explain why too much exercise could be harmful to the human body (3)
-Increased exercise results in wear and tear of joints, cartilage, tendons, ligaments
-Therefore leading to joint damage
-Suppression of immune system
-Therefore leading to increased risk of infection
Explain the process when blood pressure is too high (4)
-Detected by baroreceptors which send impulses to cardiovascular control centre
-It sends impulses along the parasympathetic neurons which secrete acetylcholine
-Acetylcholine binds the SAN causing it to fire less frequently
-Heart rate slows down and blood pressure decreases back to normal
Explain the process when blood pressure is too low (4)
-Detected by baroreceptors which send impulses to cardiovascular control centre
-It sends impulses along sympathetic neurons which secrete noradrenaline
-Noradrenaline binds to receptors to SAN causing it to fire more frequently
-Heart rate speeds up and blood pressure increases back to normal
Explain the process when O2 in the blood is high / Low CO2 (4)
-Detected by chemoreceptors which sends impulses to cardiovascular control centre
-It sends impulses along parasympathetic neurons which secrete acetylcholine
-Acetylcholine binds to receptors on SAN causing it to fire less frequently
-Heart rate slows down and O2/CO2 and PH return to normal
Explain the process when blood O2 is low / High CO2 (4)
-Detected by chemoreceptors which send impulses to cardiovascular control centre
-It sends impulses along sympathetic neurons which secrete noradrenaline
-Noradrenaline binds to receptors on SAN causing it to fire more frequently
-Heart rate speeds up and O2/CO2 levels return to normal
Control of the breathing rate (3)
-Controlled by the ventilation centres (also called respiratory centres) in the medulla oblongata
-The inspiratory centre controls the movement of air into the lungs (inhalation)
-The expiratory centre controls the movement of air out of the lungs (exhalation)
Effects of the inspiratory centre on breathing rate (5)
-It sends nerve impulses along motor neurons to the intercostal muscles of the ribs and diaphragm muscles
-These muscles will contract and cause the volume of the chest to increase
-This lowers the air pressure in the lungs to slightly below atmospheric pressure
-An impulse is also sent to the expiratory centre to inhibit its action
-Due to the difference in pressure between the lungs and outside air, air will flow into the lungs
Role of stretch receptors in inspiration (2)
-Stretch receptors in the lungs are stimulated as they inflate with air
-Nerve impulses are sent back to the medulla oblongata which will inhibit the inspiratory centre
Effects of the expiratory centre on breathing rate (4)
-It sends nerve impulses to the intercostal and diaphragm muscles
-These muscles will relax and cause the volume of the chest to decrease
-This increases the air pressure in the lungs to slightly above atmospheric pressure
-Due to the higher pressure in the lungs, air will flow out of the lungs
Role of stretch receptors in expiration (2)
-As the lungs deflate, the stretch receptors become inactive
-Means that the inspiratory centre is no longer inhibited and the next breathing cycle can begin
Chemoreceptors
-Chemoreceptors are found in the medulla oblongata, as well as in the aortic and carotid bodies
-They are stimulated by changes in the levels of carbon dioxide and oxygen in the blood, as well as blood pH
Effects of exercise on breathing rate (5)
-Decrease the pH of the blood is detected by chemoreceptors
-Impulses sent to the intercostal muscles and diaphragm
-This increases the rate and depth of breathing
-Results in more oxygen entering the lungs and more CO2 leaving the lungs
-The decrease in carbon dioxide levels will result in the blood pH returning back to normal
Baroreceptors
-Found in the aortic and carotid bodies and they are stimulated by high and low blood pressure
Benefits of exercise (4)
-Balances LDLs and HDLs
-Better BMI and waist : hip ratio
-Reduced risk of cancer
-Reduced risk of coronary heart disease and stroke (lower blood pressure)
Negative impacts of exercise (3)
-Joints may become damaged due to increased wear and tear
-Suppresses the immune system, making the individual more susceptible to disease and infection
-Vigorous exercise can cause low levels of antibody production
The demand for oxygen changes during exercise
The change in demand affects the breathing rate
Explain the effect of exercise on the changes in oxygen consumption (4)
-Exercise will increase oxygen consumption
-Because there is increased aerobic respiration
-Because more energy / ATP is needed by muscles
-Oxygen required to convert lactic acid into glucose / pyruvate
-Oxygen consumption begins to decrease after exercise
The demand for oxygen changes during exercise
The change in demand affects the breathing rate
At the start of exercise, breathing rate increases
Explain how starting to exercise causes an increase in breathing rate (3)
-Exercise initiates impulses from the motor cortex / stretch receptors in muscle cells
-Impulses sent to respiratory / ventilation centre
-Leading to increased impulses to intercostal muscles / diaphragm
As levels of activity increase, the heart can respond to the changing demand for oxygen
Describe how the sinoatrial node (SAN) is involved in bringing about a change in heart rate as the level of activity increases (2)
-More stimulation / depolarisation of the SAN from the sympathetic nervous system
-Causing more frequent waves of depolarisation from the SAN to the atria
-Leading to more frequent contraction of the atria / stimulation of the SAN
As levels of activity increase, the heart can respond to the changing demand for oxygen
Which term describes the ability of heart muscle to contract without external stimulation? (1)
A) autonomic
B) cardiac
C) myogenic
D) systolic
Myogenic
Creatine phosphate
-Substance which is stored in muscle fibres
-It supplies the initial energy needed to produce ATP before aerobic respiration
-Serves as a rapid release reserve of high energy
Oxygen debt
The amount of oxygen needed to oxidise lactic acid to carbon dioxide and water
Lactate can build up in the muscles of a sprinter.
Suggest why the build up of lactate may prevent any further increase in speed (2)
-Build up of lactate causes a fall in PH / more more acidic
-This denatures enzyme shape
-Which slows down glycolysis / ATP production / anaerobic respiration
Explain the fate of lactate following a sprint (4)
-Lactate in the blood is transported to / broken down in the liver
-Lactate is converted to pyruvate
-Via oxidation / production of reduced NAD+
-Pyruvate is oxidised in the Krebs cycle
-This requires extra oxygen / oxygen debt
-Carbon dioxide and water are produced
Gluconeogenesis
Lactate removed from muscles and carried to the liver in the blood then is converted back into pyruvate and then into glucose. The glucose is then carried around in the blood to replenish glycogen stores in muscles
State the location of the SAN in the heart (1)
Right atrium
Explain what is meant by the term myogenic (2)
-That stimulation generated from within (muscle)
-This results in depolarisation
Explain how an electrocardiogram (ECG) can be used to calculate a person’s heart rate (3)
-Shows electrical activity of the heart
-Idea of how to identify {one heart beat / time for one heart beat}
-Count the number of these / peaks in a set time or how long from one set of electrical activity to the next
Workers in the brewing industry may be at risk due to the carbon dioxide released by yeast fermentation.
Atmospheric air contains between 0.03% and 0.04% carbon dioxide.
A concentration of 5% carbon dioxide in the air causes a change in the heart rate of people exposed to this concentration.
Explain why a carbon dioxide concentration of 5% causes a change in heart rate (5)
-The concentration of carbon dioxide in the alveoli is higher
-The concentration of carbon dioxide in the blood is higher / pH of blood is lower
-Detected by chemoreceptors in medulla /carotid artery / aorta
-Impulses sent to cardiovascular / cardiac control centre in medulla
-Autonomic nervous system / sympathetic nerve stimulated
-More impulses to SAN
-Noradrenalin / norepinephrine released onto SAN ;
-SAN excitation rate increased
-Heart rate will increase
How do blood vessels in the skin respond to low body temperature? (3)
-Smooth muscle in shunt vessels relaxes and they dilate.
-Smooth muscle in arterioles contracts and they constrict (vasoconstriction).
-Less blood flows through capillaries close to the skin surface to conserve heat.
How does the body respond to low body temperature? (5)
-Sweat glands secrete less sweat due to decreased stimulation from sympathetic neurones from the hypothalamus.
-Erector pili muscles contract → hairs on skin stand up to trap an insulating layer of air.
-Thyroid gland releases more thyroxine → metabolic rate increases.
-Shunt vessels dilate and arterioles constrict.
-Skeletal muscles contract rapidly to generate metabolic heat through respiration.
Explain how heart rate is controlled during exercise (5)
-Increase in respiration rate in muscle cells
-More CO2/carbonic acid in blood
More lactate / lactic acid in blood
-Idea that chemoreceptors in medulla stimulated
-Cardiovascular control centre in medulla
-Autonomic nervous system /sympathetic nerve
-More impulses from medulla / cardiovascular control centre to SAN
OR along neurones to SAN
-More noradrenaline / norepinephrine released onto SAN
-SAN excitation rate increased
-Causing an increased heart rate
