Homeostasis
This type of range of physiological conditions needs to be maintained for cell survival.
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Exercise 1, Q.1
This is the definition of a feedback mechanism in biology. They include these 3 major components.
A physiological process responding to a change in the system.
1- Receptors
2- Control Centre
3- Effectors
Exercise 1, Q.2
The VRG, which sets resting respiratory rate, and DRG, which integrates information from stretch and chemoreceptors to communicate to the VRG, are in this part of the brain.
The medullary respiratory centre (signals contraction for tidal inspiration and relaxation for tidal expiration)
Exercise 2, Q.1 i)
These two receptor types detect the need to increase respiratory rate with exercise.
Proprioceptors in active muscles
Chemoreceptors detect mostly pH, but also CO2 changes (need to eliminate CO2 and consume O2)
Exercise 2, Q.1 ii)
This branch of the nervous system releases acetylcholine via the Vagus Nerve to cause K channels to open in SA node cells. This slows heart contractions to produce the average 75bpm.
The PSNS
Exercise 2, Q.2
Homeostasis must be maintained regardless of what's going on in this type of environment.
The external
Exercise 1, Q.1
This is the definition of a negative feedback mechanism.
When internal physiological conditions are changed to oppose initial stimulus.
Ex: body temperature, blood glucose, blood pressure, CO2 levels
Exercise 1, Q.2
This part of the brain fine tunes respiration by transmitting impulses to the VRG.
Pontine Respiratory Centres
Exercise 2, Q.1 i)
This is how the bicarbonate equilibrium equation is related to maintaining body pH during exercise.
CO2 is removed at the lungs so the equilibrium shifts to react more H with HCO3- to create more CO2 and H2O. This counteracts lactic acid and H build-up.
Exercise 2, Q.1 iii)
This branch of the nervous system releases norepinephrine via cardiac nerves to increase Na permeability of SA node cells. Contractile cells of the heart also become more permeable to Ca.
This organ can also release E and NE to increase heart rate and contraction force.
The SNS
Adrenal medulla
Exercise 2, Q.2
37 degrees Celsius is homeostatic body temperature, which is largely maintained by this type of rate.
Metabolic rate (energy balance is also homeostatically maintained)
Exercise 1, Q.1
This is the definition of a positive feedback mechanism.
When internal physiological conditions deviate even more from original to amplify the initial stimulus.
Ex: APs, platelet plug formation, LH surge, oxytocin, and zymogen activation (pepsinogen and trypsinogen)
Exercise 1, Q.2
This reflex uses stretch receptors in the visceral pleura and bronchi/bronchioles to respond to muscle stretching. It sends signals to inhibit the medullary respiratory centre to prevent overinflation of the lungs.
Hering-Breur Reflex
Exercise 2, Q.1 i)
These are three reasons for an increase the heart rate with exercise.
1- SNS: release of E increases permeability of SA node cells to sodium
2- Increase in CO2 and decrease in pH detected by chemoreceptors also results in SNS stimulation for the heart
3- Increase in body temperature i) increases metabolic rate of cardiac cells ii) increases heart rate to pump more blood to skin to dissipate extra heat
Exercise 2, Q.3
These receptors detect changes in blood pressure and send signals to the medullary cardiovascular centre to reduce SNS signals in the case of low blood pressure. Reducing SNS signalling decreases heart rate, force of contraction, and allows vasodilation.
Baroreceptors in the carotid arteries and aortic arch
Exercise 2, Q.2
These three factors related to the blood must be homeostatically maintained.
1- Volume (5-6L male; 4-5L female)
2- pH (neutral 7.35-7.45)
3- Pressure (120/80mm Hg)
Exercise 1, Q.1
a) These two systems respond to stimuli and via a control centre recruit effectors. They modify internal physiological conditions to maintain homeostasis.
b) This is what would happen if homeostasis couldn't be maintained.
a) Nervous and endocrine systems.
b) Illness or death.
Exercise 1, Q.3&4
a) This control involves the cortex and may be useful for singing, holding your breath, and speaking.
b) This control modifies breathing due to emotions and pain.
Voluntary control
Hypothalamic controls
Exercise 2, Q.1 i)
These are two reasons for the increase in cardiac output with exercise.
1- Increase in heart rate (CO=HRxSV)
2- SNS: increase in force of contraction. Opening of VG Ca channels in T-tubule of contractile myocardial cells triggers more SR calcium channels to open.
Exercise 2, Q.3
Chemoreceptors of the brain and blood vessels in the neck may detect high levels of these two chemicals, respectively, during exercise. This results in stimulating SNS innervation of the heart.
CO2 and hydrogen ions
Exercise 2, Q.2
These three concentration types must be homeostatically maintained.
1- Ion (K, Ca, Na, Cl for neurons, muscles, blood tonicity)
2- Gas (mostly H, CO2 are monitored)
3- Nutrient/waste (glu, aa, urea, ammonia)
Exercise 1, Q.1
This is why people describe physiology as an "integrative" science.
-It integrates physics, chemistry, biology, and genetic in one subject
-Cells, tissues, organs, and organ systems all coordinate to maintain homeostasis
Exercise 1, Q.5
Chemical control of respiration involves central chemoreceptors in the medulla and peripheral chemoreceptors in the aortic arch and carotid arteries. The receptors directly detect this chemical.
Hydrogen ions
Central: H in CSF is detected due to CO2 crossing the BBB and being converted by CA. CSF is poorly buffered so small changes in pH are detected.
Exercise 2, Q.1 i)
This is why respiration and heart rate simultaneously increase during exercise.
Responding to the same stimuli (CO2, pH, proprioceptor signalling)
*Not because of each other
Exercise 2, Q.4
These are 4 other extrinsic factors that influence heart rate.
1- Ion balance: high or low K in ISF changes membrane potential
2- Fever: increased metabolic activity will increase heart rate
3- Age: newborns have higher heart rate
4- Fitness: more fit means lower resting heart rate
Exercise 2, Q.2