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What is the definition of homeostasis?
What is the definition of homeostasis?
- The complete absence of any changes in internal environment
- The body's ability to maintain stable internal conditions despite external changes (correct)
- A process that increases fluctuations in body systems
- A mechanism that emphasizes only positive feedback
Which of the following is an example of a condition that homeostasis maintains?
Which of the following is an example of a condition that homeostasis maintains?
- Body temperature increasing uncontrollably
- Blood glucose levels rising indefinitely
- Blood pH levels remaining stable at 7.4 (correct)
- Blood pressure fluctuating wildly
How does a negative feedback mechanism function?
How does a negative feedback mechanism function?
- It enhances the change beyond normal levels
- It triggers adaptive responses that increase body disturbances
- It senses changes and brings about effects that reverse them (correct)
- It allows multiple systems to operate independently
What initiates the adaptive response in a negative feedback mechanism?
What initiates the adaptive response in a negative feedback mechanism?
What is a characteristic of positive feedback mechanisms?
What is a characteristic of positive feedback mechanisms?
Which of the following hormones is associated with positive feedback during childbirth?
Which of the following hormones is associated with positive feedback during childbirth?
In terms of glucose levels, what is typically true about homeostasis?
In terms of glucose levels, what is typically true about homeostasis?
What happens to the signaling of sensors in a negative feedback mechanism once normal state is regained?
What happens to the signaling of sensors in a negative feedback mechanism once normal state is regained?
Homeostasis allows internal conditions to remain constant despite dramatic changes in external conditions.
Homeostasis allows internal conditions to remain constant despite dramatic changes in external conditions.
Negative feedback mechanisms enhance changes in the body's internal conditions.
Negative feedback mechanisms enhance changes in the body's internal conditions.
The average concentration of blood glucose is constant at 0.1%.
The average concentration of blood glucose is constant at 0.1%.
Positive feedback mechanisms increase the magnitude of a stimulus.
Positive feedback mechanisms increase the magnitude of a stimulus.
The control center in the brain only responds to blood pressure changes.
The control center in the brain only responds to blood pressure changes.
The body's adaptive response is triggered when temperatures fall below 37°C.
The body's adaptive response is triggered when temperatures fall below 37°C.
Positive feedback mechanisms are commonly involved in labor and childbirth.
Positive feedback mechanisms are commonly involved in labor and childbirth.
Once normal conditions are regained in negative feedback, sensors stop sending signals to the brain.
Once normal conditions are regained in negative feedback, sensors stop sending signals to the brain.
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Study Notes
Homeostasis
- The internal environment of the body is maintained in a relatively constant state.
- Internal conditions stay within a specific range, even when external conditions change dramatically.
- Examples in the human body:
- Blood pH: 7.4
- Body temperature: 37°C
- Blood pressure: 120/80
- Blood glucose concentration: 0.1%
Feedback Mechanisms
- Homeostasis is maintained by feedback mechanisms.
- Negative feedback mechanisms: Maintain stability by sensing a change and causing an effect that reverses it.
- The brain contains control centers which monitor and control bodily conditions like pH, temperature, blood pressure, and glucose levels.
- Sensors throughout the body detect unacceptable levels and signal the appropriate brain center.
- The control center directs the body to act in a way to restore the normal state.
Negative Feedback
- The change in body conditions triggers an adaptive response.
- Once the normal state is regained, the sensor stops signaling the brain center, so the adaptive response stops.
- It results in fluctuations around a set point.
- The concentration of blood glucose is rarely exactly 0.1%, it's usually slightly above or below, but it averages out to be 0.1% throughout the day.
Positive Feedback
- A stimulus triggers an increase in the stimulus. This causes a greater adaptive response, which results in a greater stimulus.
- During labor, oxytocin causes the uterus to contract.
- Oxytocin is made in the hypothalamus and stored in the posterior pituitary.
- The baby's head pressing against the cervix just before birth causes the release of oxytocin, which causes contractions.
Homeostasis
- Homeostasis is the maintenance of a stable internal environment in the body.
- Regardless of external conditions, internal conditions stay within a narrow range.
Homeostasis Examples
- Blood pH is maintained at 7.4.
- Body temperature is maintained at 37 degrees Celsius.
- Blood pressure is maintained at 120/80.
- Blood glucose concentration is maintained at 0.1%.
Feedback Mechanisms
- Homeostasis is maintained through feedback mechanisms.
- Negative feedback mechanisms maintain stability by reversing changes.
- Sensors all over the body detect unacceptable levels and signal the brain.
- The brain then directs the body to take action to restore normal conditions.
Negative Feedback Example
- Temperature sensors in the skin signal the brain if the body gets too cold.
- The brain directs the body to shiver, which generates heat.
- As body temperature returns to normal, the temperature sensors in the skin stop signaling, and the shivering stops.
Positive Feedback Example
- The release of oxytocin during labor is a positive feedback mechanism.
- Oxytocin causes the uterus to contract.
- The contractions push the baby's head against the cervix, which stimulates the release of more oxytocin.
- This cycle continues until the baby is born.
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