Podcast
Questions and Answers
What is the primary outcome when a control system in the body fails to compensate for a disturbance?
What is the primary outcome when a control system in the body fails to compensate for a disturbance?
- The development of pathophysiology, potentially leading to illness or death. (correct)
- Successful reestablishment of homeostasis through autoregulation.
- Immediate activation of positive feedback mechanisms to amplify the compensation.
- A temporary return to homeostasis followed by further decompensation.
Which statement accurately describes the role of a receptor in a negative feedback control mechanism?
Which statement accurately describes the role of a receptor in a negative feedback control mechanism?
- To amplify the stimulus to create a more significant change in the body.
- To immediately activate the effector without the control center's input.
- To produce a response that acts in the same direction as the initial stimulus.
- To monitor the internal environment and detect changes from the set point. (correct)
How does negative feedback primarily function to maintain homeostasis?
How does negative feedback primarily function to maintain homeostasis?
- By producing an effect that counteracts the original stimulus. (correct)
- By amplifying the original stimulus to enhance the body's response.
- By rapidly accelerating changes to quickly correct a disturbance.
- By creating a feed-forward response to anticipate a future change.
Which of the following is a key difference between negative and positive feedback control mechanisms?
Which of the following is a key difference between negative and positive feedback control mechanisms?
In the context of the body's regulatory systems, what does the term 'effector' specifically refer to?
In the context of the body's regulatory systems, what does the term 'effector' specifically refer to?
What is the primary purpose of the human body's ability to predict and rapidly adapt to environmental changes?
What is the primary purpose of the human body's ability to predict and rapidly adapt to environmental changes?
Which type of ion channel is always open, contributing to the resting membrane potential?
Which type of ion channel is always open, contributing to the resting membrane potential?
What is the main difference between voltage-gated and ligand-gated channels?
What is the main difference between voltage-gated and ligand-gated channels?
In a nerve cell, why is membrane permeability to K+ higher than membrane permeability to Na+?
In a nerve cell, why is membrane permeability to K+ higher than membrane permeability to Na+?
What is the approximate resting membrane potential of a large nerve fiber?
What is the approximate resting membrane potential of a large nerve fiber?
How does the sodium-potassium pump contribute to the negative resting membrane potential?
How does the sodium-potassium pump contribute to the negative resting membrane potential?
What is the role of K+-Na+ 'leak channels' in the nerve membrane?
What is the role of K+-Na+ 'leak channels' in the nerve membrane?
Which cellular function is not directly activated or affected by changes in membrane potentials?
Which cellular function is not directly activated or affected by changes in membrane potentials?
In a homeostatic control system, what is the role of the effector?
In a homeostatic control system, what is the role of the effector?
Which of the following accurately describes a negative feedback mechanism within a homeostatic control system?
Which of the following accurately describes a negative feedback mechanism within a homeostatic control system?
Which of these examples primarily demonstrates a positive feedback mechanism?
Which of these examples primarily demonstrates a positive feedback mechanism?
What is the primary function of feed-forward control in the context of homeostasis?
What is the primary function of feed-forward control in the context of homeostasis?
According to the provided text, which scenario exemplifies the 'vicious circle' potential of positive feedback?
According to the provided text, which scenario exemplifies the 'vicious circle' potential of positive feedback?
How does a receptor (sensor) contribute to maintaining homeostasis based on the diagram provided?
How does a receptor (sensor) contribute to maintaining homeostasis based on the diagram provided?
What is the primary distinction between a 'stimulus' and a 'response' within a control system?
What is the primary distinction between a 'stimulus' and a 'response' within a control system?
In the context of feedback control, what is the role of the 'afferent pathway'?
In the context of feedback control, what is the role of the 'afferent pathway'?
Flashcards
Homeostasis
Homeostasis
The ability of an organism to maintain stable internal conditions despite external changes.
Negative Feedback
Negative Feedback
A control mechanism where output reduces the effect of the original stimulus.
Control Mechanism Components
Control Mechanism Components
Three components: Receptor, Control Center, and Effector work together to maintain homeostasis.
Feedback Control System
Feedback Control System
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Positive Feedback
Positive Feedback
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Control Mechanism
Control Mechanism
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Stimulus
Stimulus
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Receptor (Sensor)
Receptor (Sensor)
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Feed-forward control
Feed-forward control
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Adaptive Feedback Control
Adaptive Feedback Control
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Ion Channels
Ion Channels
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Leakage Channels
Leakage Channels
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Resting Membrane Potential
Resting Membrane Potential
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Gated Channels
Gated Channels
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Voltage-Gated Channels
Voltage-Gated Channels
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Sodium-Potassium Pump
Sodium-Potassium Pump
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Mechanical Stimulation
Mechanical Stimulation
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Electrogenic Pump
Electrogenic Pump
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Study Notes
Homeostasis & Control
- Successful compensation leads to homeostasis being re-established.
- Failure to compensate results in pathophysiology, illness, and potentially death.
- An organism maintains homeostasis to maintain stable internal conditions in a constantly changing external environment.
- Three types of regulation are hormonal, nervous, and autoregulation.
Regulation of Body Functions
- The three forms of regulation work together as a feedback control system.
- Feedback Control: Output from a controlled organ modifies the control system's actions.
- Negative feedback control: Output opposes the initial stimulus.
- Positive feedback control: Output increases the initial stimulus.
Negative Feedback
- Feedback signals induce an opposite response to the action of the control system.
- This opposing action is primarily an inhibitory action.
- Negative feedback mechanisms prevent small changes from becoming too large via counteracting responses.
- Examples include body temperature regulation.
Homeostasis: Control Mechanisms
- Homeostasis is maintained by three interdependent components:
- Receptor: Monitors changes in the environment (stimuli)
- Control center: Determines the set point for a variable.
- Effector: Responds to the stimulus to maintain the set point.
- In negative feedback systems, the output shuts off the initial stimulus.
- This prevents sudden and severe changes in the body, as seen in blood glucose regulation.
Homeostasis: Control Mechanisms (Diagrammatic Representation)
- Input (information sent along afferent pathways).
- Change detected by the receptor.
- Stimulus produces a change in a variable.
- Imbalance in variable.
- Response of effector feeds back to influence the stimulus magnitude, returning the variable to homeostasis.
Homeostasis: Negative Feedback (Specific Example - Blood Glucose)
- Insulin-secreting cells respond to high blood glucose by releasing insulin.
- Body cells absorb glucose, lowering blood glucose.
- Glucagon-releasing cells respond to low blood glucose by releasing glucagon.
- Liver releases glucose back to blood.
Positive Feedback
- Feedback signals increase the action of the control system.
- Examples include blood clotting, micturition (urination), defecation, nerve signal generation, and uterine contraction during childbirth.
Positive Feedback (Stimulatory):
- Enhances the response and reinforces the initial stimulus.
- An example is the stretch receptors of the uterine wall reinforcing labor contractions during childbirth.
Importance of Feedback Mechanisms
- Feedback mechanisms enhance the action of the initial stimulus, or amplify/reinforce the change to promote a complete process.
- The feedback loop can become a vicious circle causing instability and potentially death if not appropriately regulated.
Feed-Forward Control
- Direct effect of a stimulus on the control system before feedback is employed.
- Adaptive feedback control; enables the body to anticipate and respond to changes in the environment, as in shivering before cold exposure.
Types of Ion Channels
- Leakage channels: Always open, influencing resting membrane potential.
- Gated channels: Open or close in response to stimuli.
- Voltage-gated: Open/close due to changes in voltage.
- Ligand-gated: Open/close in response to a chemical stimulus.
- Mechanically-gated: Open/close due to mechanical stimulation.
Electrical Potentials
- Electrical potentials exist across cell membranes, enabling some cells (e.g., nerve and muscle) to generate electrochemical impulses for signal transmission.
- Local changes in membrane potentials activate other cell functions like those in glandular, macrophage, and ciliated cells.
Resting Membrane Potential of Nerves
- The stable electrical potential difference across a nerve cell's membrane when not transmitting signals is approximately -90 millivolts, with the inside being more negative.
Factors Determining Resting Potential (Sodium-Potassium Pump)
- The Sodium-Potassium pump continuously moves sodium ions out of and potassium ions into the cell.
- This process is electrogenic (creates an electrical difference), maintaining a negative potential inside the cell membrane.
Leakage of Potassium and Sodium Through the Nerve Membrane
- Potassium and sodium can cross the membrane through leak channels.
- Potassium permeability is significantly higher than sodium permeability, influencing the resting membrane potential.
Relation of Diffusion Potential to Concentration Difference (Nernst Potential)
- The diffusion potential that exactly opposes the net diffusion of an ion is the Nernst potential.
- Its magnitude is determined by the ratio of ion concentrations on either side of the membrane.
Nernst Equation
- Calculates the Nernst potential for univalent ions at normal body temperature (37°C.).
Calculation of Diffusion Potential (Goldman-Hodgkin-Katz Equation)
- Calculates the membrane potential when the membrane is permeable to multiple ions (e.g., sodium, potassium, and chloride).
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