4.4 Negative Feedback Loop
3 min read•june 18, 2024
are crucial for maintaining in the body. These mechanisms detect changes in regulated variables like body temperature and blood glucose, then trigger responses to bring them back to set points.
Key components include that sense changes, control centers that process information, and that carry out responses. Understanding these loops is essential for grasping how the body maintains stability in various physiological systems.
Negative Feedback Loops and Homeostasis
Negative feedback for homeostasis
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- loops function as control mechanisms that maintain homeostasis by counteracting changes in a system
- Detect deviations from a and initiate responses to return the system back to the set point (, )
- Homeostasis involves the maintenance of a stable internal environment despite changes in the external environment
- Homeostatic variables include body temperature (37°C), blood glucose levels (70-110 mg/dL), and blood pressure (120/80 mmHg)
- Negative feedback loops maintain homeostasis by:
- Sensing changes in a using receptors (, , )
- Comparing the current state to the set point using a (, )
- Activating effectors to counteract the change and bring the variable back to the set point (, )
Components of negative feedback
- Regulated variable: The physiological parameter being maintained within a specific range (body temperature, blood glucose)
- Set point: The optimal level or range for the regulated variable (37°C for body temperature, 70-110 mg/dL for blood glucose)
- Receptors: Structures that detect changes in the regulated variable and send signals to the control center
- Thermoreceptors (detect changes in temperature)
- Chemoreceptors (detect changes in chemical concentrations)
- (detect changes in blood pressure)
- Control center: The central processing unit that compares the input from receptors to the set point and determines the appropriate response
- Often located in the brain () or other organs (pancreas)
- Effectors: Organs, tissues, or cells that receive signals from the control center and carry out the necessary actions to restore homeostasis
- Sweat glands (thermoregulation)
- Blood vessels (, )
- (insulin secretion)
- Steps in a negative feedback loop:
- Stimulus: A change in the regulated variable occurs (increase in body temperature)
- Reception: Receptors detect the change and send signals to the control center (thermoreceptors in the hypothalamus)
- Processing: The control center compares the input to the set point and determines the appropriate response (hypothalamus detects temperature above 37°C)
- Response: The control center sends signals to effectors to counteract the change (hypothalamus signals sweat glands and blood vessels)
- Restoration: Effectors carry out actions that bring the regulated variable back to the set point (sweating and vasodilation reduce body temperature)
Negative vs positive feedback mechanisms
- Negative feedback loops:
- Maintain homeostasis by counteracting changes and returning the system to the set point (thermoregulation, blood glucose regulation, blood pressure regulation)
- More common in physiological regulation and essential for maintaining a stable internal environment
- processes:
- Amplify changes in a system, leading to a deviation from the initial state ( release during childbirth, in blood coagulation)
- Less common in physiological regulation but play important roles in certain processes
- Key differences:
- Negative feedback loops stabilize a system, while positive feedback processes amplify changes
- Negative feedback loops have a defined set point, while positive feedback processes do not
- Negative feedback loops are more prevalent in maintaining homeostasis, while positive feedback processes are involved in specific physiological events (childbirth, , action potential generation)
Regulatory Systems and Homeostasis
- The plays a crucial role in maintaining homeostasis by regulating various bodily functions without conscious control
- act as chemical messengers in negative feedback loops, helping to regulate physiological processes over longer periods
- is a mechanism where the end product of a biochemical pathway inhibits an earlier step, helping to maintain in cellular processes
Key Terms to Review (33)
Autonomic Nervous System: The autonomic nervous system is the part of the nervous system that controls and regulates the body's internal organs and involuntary functions, such as heart rate, breathing, digestion, and blood pressure, without conscious control. It is a critical component in maintaining homeostasis and ensuring the body's proper functioning.
Baroreceptors: Baroreceptors are specialized sensory receptors that detect changes in blood pressure within the cardiovascular system. They play a crucial role in the negative feedback loop that helps maintain homeostasis of blood pressure.
Blood clotting: Blood clotting is the process by which blood changes from a liquid to a gel, forming a clot to prevent excessive bleeding. This involves a complex cascade of events leading to the formation of fibrin strands that stabilize the clot.
Blood Glucose Regulation: Blood glucose regulation is the physiological process that maintains a stable and optimal level of glucose in the bloodstream. This is crucial for providing energy to cells throughout the body and ensuring proper functioning of various organ systems.
Chemoreceptors: Chemoreceptors are specialized sensory cells that detect changes in the chemical composition of the body's internal and external environments. They play crucial roles in various physiological processes, including negative feedback loops, pain perception, and respiratory control.
Clotting Cascade: The clotting cascade, also known as the coagulation cascade, is a complex series of enzymatic reactions that lead to the formation of a fibrin clot to stop bleeding and promote wound healing. It is a critical physiological process that helps maintain homeostasis by regulating blood flow and preventing excessive blood loss.
Control Center: The control center refers to the part of a system that regulates, manages, and coordinates the various components and functions within that system. It serves as the central hub responsible for monitoring, adjusting, and maintaining the overall operation and homeostasis of the system.
Effectors: Effectors are the organs, tissues, or structures that directly respond to and carry out the commands of the control centers in the body. They are the final common pathway that translates the physiological signals from the control centers into the appropriate biological responses to maintain homeostasis.
Endocrine Glands: Endocrine glands are specialized organs in the body that secrete hormones directly into the bloodstream to regulate various physiological processes. These glands play a crucial role in the negative feedback loop, a mechanism that maintains homeostasis within the body.
Homeostasis: Homeostasis is the process by which the body maintains a stable and balanced internal environment, despite changes in external conditions. It is a fundamental principle that allows the body to function optimally and adapt to various stressors.
Homeostatic response system: The homeostatic response system is the body's mechanism to maintain internal stability in response to changes in external conditions. It involves various physiological processes that work together to keep parameters like temperature, pH, and electrolyte balance within a narrow range.
Hormones: Hormones are chemical messengers produced by the endocrine system that regulate various physiological processes in the body. They play a crucial role in maintaining homeostasis, controlling growth and development, and influencing mood, metabolism, and other vital functions.
Hypothalamus: The hypothalamus is a crucial part of the brain that regulates various physiological processes, including hunger, thirst, sleep, and hormone release. It plays a pivotal role in maintaining homeostasis by controlling the endocrine system through its interaction with the pituitary gland.
Hypothalamus: The hypothalamus is a small, but crucial, region of the brain that plays a vital role in maintaining homeostasis, regulating hormone production, and coordinating the body's responses to various stimuli. As a key component of the endocrine system, the hypothalamus serves as the link between the nervous system and the endocrine system, allowing for the integration of physiological and behavioral processes.
Insulin Secretion: Insulin secretion is the process by which the pancreatic beta cells release the hormone insulin into the bloodstream. Insulin is a critical regulator of blood glucose levels and plays a central role in the body's metabolic processes, particularly in the context of the negative feedback loop described in 4.4 Negative Feedback Loop.
Negative feedback: Negative feedback is a physiological process that counteracts a change in the body to maintain homeostasis. It involves detecting deviations from the norm and initiating responses to restore balance.
Negative Feedback Inhibition: Negative feedback inhibition is a regulatory mechanism in biological systems where the end product of a metabolic pathway inhibits an earlier step in the same pathway, thereby reducing its own production. This process helps maintain homeostasis and prevent excessive accumulation of a substance.
Negative Feedback Loops: A negative feedback loop is a self-regulating mechanism in biological systems where the output of a process inhibits or reduces the input, creating a stabilizing effect. This term is particularly relevant in the context of maintaining homeostasis and regulating various physiological processes within the body.
Osmoreceptors: Osmoreceptors are specialized sensory cells that detect changes in the osmolality, or solute concentration, of the extracellular fluid in the body. These receptors play a crucial role in the regulation of fluid balance and the release of antidiuretic hormone (ADH) to maintain homeostasis.
Oxytocin: Oxytocin is a hormone produced in the hypothalamus and released by the posterior pituitary gland. It plays a crucial role in various physiological processes, including uterine contractions, lactation, and the regulation of the body's stress response through its involvement in the hypothalamic-pituitary-adrenal (HPA) axis.
Pancreas: The pancreas is a vital organ located behind the stomach that plays a crucial role in the body's metabolism and digestion. It is responsible for producing hormones that regulate blood sugar levels and enzymes that aid in the breakdown of food.
Positive feedback: Positive feedback amplifies changes or deviations in a system, leading to an enhanced or intensified output. It is less common in biological systems compared to negative feedback loops.
Receptors: Receptors are specialized molecules found on the surface or within cells that bind to specific substances, triggering a physiological response. They act as the primary interface between cells and their external environment, allowing them to detect and respond to various chemical signals and stimuli.
Regulated Variable: A regulated variable is a quantity or condition that is maintained within a desired range or set point by a feedback control system. It is a key component in understanding the concept of a negative feedback loop, where the system actively works to counteract changes and keep the variable stable.
Set Point: The set point refers to the physiological value or range that the body aims to maintain for a particular parameter, such as temperature, blood pressure, or blood sugar levels. It represents the ideal or optimal state that the body's regulatory systems strive to achieve and sustain through various homeostatic mechanisms.
Steady state: Steady state is the condition in which the overall intake of a drug is in dynamic equilibrium with its elimination. This means the drug's concentration in the bloodstream remains consistent over time with regular dosing.
Steady State: Steady state refers to a condition where a system or process maintains a consistent, stable, and unchanging state over time. It is a fundamental concept in the context of maintaining homeostasis and negative feedback loops within the body.
Sweat Glands: Sweat glands are specialized exocrine glands found in the skin that produce and secrete sweat, a watery fluid composed of water, salts, and other substances. They play a crucial role in the body's thermoregulation process, helping to maintain a stable internal temperature through evaporative cooling.
Thermoreceptors: Thermoreceptors are sensory receptors that detect changes in temperature within the body or in the environment. They play a crucial role in the regulation of body temperature and the perception of thermal stimuli, which are important for both the negative feedback loop of thermoregulation and the introduction to pain.
Thermoregulation: Thermoregulation is the process by which the body maintains its internal temperature within a narrow, optimal range, despite changes in the external environment. It is a critical physiological function that helps the body adapt and survive in different temperature conditions.
Uterine contraction during childbirth: Uterine contractions during childbirth are the rhythmic tightening and relaxing of the uterine muscles. These contractions help to dilate the cervix and push the baby through the birth canal.
Vasoconstriction: Vasoconstriction is the narrowing or constriction of blood vessels, specifically the arteries and arterioles, which leads to a decrease in blood flow and blood pressure. This physiological process is an important mechanism in the regulation of blood flow and blood pressure throughout the body.
Vasodilation: Vasodilation refers to the widening or dilation of blood vessels, particularly the arteries and arterioles. This process leads to increased blood flow and reduced vascular resistance, which can have significant implications in various physiological and pharmacological contexts.