BIOL125 Lecture Notes - Lecture 3: Microvillus, Catabolism, Acetyl-Coa
BIOL week 3
LA Homeostasis
What is homeostasis?
- The body’s ability to maintain a stable internal environment within a narrow pre-set
range, relative to a variable external environment
- Each bodily structure contributes to keeping internal environment within normal
limits
Why we need to maintain homeostasis
- Optimal conditions for our cells to function
- Cells constantly need nutrients and removal of waste products
- Factors that need to be maintained within narrow ranges:
oGases (eg: O2, CO2)
oIons (eg: Na+, K+, Ca2+)
oNutrients (eg: glucose)
opH (acid/base balance) blood pH is 7.4
oWater (hydrated/dehydrated)
oTemperature (~37 °C)
Disruption to homeostasis
- Imbalance and disruption to optimum range for normal body functions must be
corrected
- If not disease or death
oBlood pressure if it cannot be controlled, it develops into hypertension
oBlood glucose levels if it cannot be controlled, it develops into diabetes
oCalcium levels = Osteomalacia variations in calcium levels can affect bone
health
Factors that affect homeostasis
- Internal disruption
oEg: An over/under-active thyroid
- External disruptions
oEg: Weather, altitude
- Can be short in duration and mild
oEg: Exercise
- Can be long in duration and intense
oEg: High blood pressure
Maintaining homeostasis
- The body has regulating systems
- Nerve impulses and/or chemical messengers transmit information through
- Positive feedback is where the stimulus causes change in the same direction
- Negative feedback is where the stimulus causes change in the opposite direction
eg: if high blood sugar, the system will try to lower the blood sugar
- Feedback Systems cycle of events where body conditions are:
oMonitored
oEvaluated
oMaintained/changed
oRemonitored
Feedback System components
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- Alpha and beta cells in the pancreas monitor blood sugar levels if blood sugar is
very high, then beta cells detect that and release insulin to lower that
Feedback system types
- Our body can negate (oppose) the change initiated by the stimulus = negative
feedback, or
- Our body can enhance the change initiated by the stimulus = positive feedback
Negative feedback
- The response opposes the initial stimulus to reverse the change back to normal
homeostatic state
- Main feedback system used to regulate changes in our body
- Used in conditions that need frequent adjustments
- Eg: body temperature, blood sugar levels, blood pressure, blood calcium levels
Negative feedback eg: temperature regulation
Positive feedback
- Strengthens or enhances the stimulus to produce an even greater (amplified) change
- Used to produce large, rapid changes
- Rare as most of the control in the body is negative feedback only a few examples
exist such as:
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oFormation of a platelet plug during blood clotting If there is a hole in a
blood vessel, platelets increase in number around the site, forming a blood
clot, stopping the bleeding
oRelease of oxytocin during child birth increase in oxytocin release causes an
increase in the amount of contractions
oActivation of immune cells when immune system recognises foreign bodies
in the body, it will produce antibodies until all the antigens are removed
oAction potential firing all or none effect
Positive feedback blood clotting
Positive feedback childbirth
Disruptions to homeostasis
- Injury
oPunctured lung, severe cuts/burns
- Illness
oFlu, inflammation, bacterial/viral infections
- Disease
oDiabetes, anaemia, heart disease, hypertension, hyper/hypothyroidism
- Lifestyle factors
oSmoking, excess drinking, lack of sleep
LB Cell metabolism and Tissue
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Document Summary
The body"s ability to maintain a stable internal environment within a narrow pre-set range, relative to a variable external environment. Each bodily structure contributes to keeping internal environment within normal limits. Optimal conditions for our cells to function. Cells constantly need nutrients and removal of waste products. Factors that need to be maintained within narrow ranges: gases (eg: o2, co2, ions (eg: na+, k+, ca2+, nutrients (eg: glucose, ph (acid/base balance) blood ph is 7. 4, water (hydrated/dehydrated, temperature (~37 c) Imbalance and disruption to optimum range for normal body functions must be corrected. Can be short in duration and mild: eg: exercise. Can be long in duration and intense: eg: high blood pressure. Nerve impulses and/or chemical messengers transmit information through. Negative feedback is where the stimulus causes change in the opposite direction . Positive feedback is where the stimulus causes change in the same direction eg: if high blood sugar, the system will try to lower the blood sugar.
