Homeostasis Flashcards
What is homeostasis and what is it important for?
Body’s ability to maintain a stable, optimal internal environment within a narrow pre set range, relative to a variable external environment. Important for maintaining ideal physiological conditions within the body during change (e.g. responding to exertion, or injury, stress).
Why do we need to maintain homeostasis?
Want optimal conditions for our cells to function. Deviations are normal but homeostasis needs to corrects the deviations. Cells constantly need nutrients and removal of waste products.
Examples of factors that need to be maintained within narrow ranges
Gas concentration (e.g. O 2 , CO 2 ) Ion concentration (e.g. Na ++, K ++, Ca 2+2+) Nutrients (e.g. glucose) pH (acid/base balance using buffers) Water (hydrated/dehydrated)
Disruption to homeostasis
Imbalance and disruption from optimum range for normal
body functions must be corrected by homeostasis. If no correction it may lead to disease or death. Such as injury, illness, disease and lifestyle factors; they can be internal or external disruptions (excess hormone production- injury), short or long duration (exercise- high blood pressure).
What happens when blood pressure, blood pH and temperature increases or decreases aren’t corrected?
Blood pressure increase is Hypertension and decrease Hypotension.
Blood pH increase alkalosis and blood pH decrease acidosis.
Temperature increase Hyperthermia and decrease Hypothermia.
What happens when blood glucose levels increases?
Diabetes
What happens when calcium levels decrease?
Osteoporosis (due to hypocalcaemia)
Feedback system
cycle of events where body conditions are monitored/detected (by receptors), evaluated (by a Control center), maintained/changed (by effectors) and continuously re-monitored.
In depth step by step of a feedback system getting a stimulus 7 steps.
- Stimulus = change in body environment and homeostatic balance.
- Detected by receptors.
- Message of details of change sent to control center via sensory/afferent neurons.
- Control center receives messages and sends out new commands.
- Message sent to effectors via motor/efferent neurons.
- Effector cells change output which causes a response that alters the controlled condition.
- Returns to homeostasis when the response brings the controlled condition back to normal.
Types of receptors that detect stimuli?
Thermoreceptors (heat and cold) in skin.
Touch receptors (fine touch and pressure) in skin.
Baroreceptors in blood vessels that detect stretch.
Chemoreceptors that detect changes in CO2 , O2 and pH.
Hormone receptors detect changes in hormone levels.
Types of effectors?
Muscle cells (skeletal, smooth and cardiac), glands, kidney, liver, bone, gut, adipose tissue and blood vessels.
2 Types of feedback
Positive and negative
Negative feedback
Response opposes the initial stimulus to reverse the
change back to normal state. Main feedback system in body used to regulate changes. Used in conditions that need frequent adjustments such as body temperature, blood sugar levels, blood pressure, blood calcium levels and pH balance.
Example of a negative feedback
- Stimulus is cold weather.
- Change in homeostatic balance is that the body’s temperature has decreased.
- This change has been monitored by thermo receptors.
- Thermoreceptors send details of the change in temperature via signals to the hypothalamus in the brain.
- The hypothalamus receives, integrates and processes the signal and sends instructions to the skeletal muscles and blood vessels in the skin.
- The skeletal muscles and blood vessels in the skin receives instruction for the muscles to shiver and the blood vessels to constrict.
- This causes an increase in temperature.
* If it was in hot weather the hypothalamus would have instructed the sweat glands to sweat and the blood vessels to dilate to decrease temperature.
Positive feedback + examples
Strengthens or enhances the stimulus to produce an
even greater (amplified) change. Used to produce large, rapid changes. Gets an important job by the body done as quickly and efficiently as possible.
There are few examples
Formation of a platelet plug during blood clotting
Release of oxytocin during child birth
Release of oxytocin during breast feeding
Activation of immune cells
