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Homeostasis

1. Overview of Homeostasis: – Homeostasis maintains optimal conditions for metabolic processes in organisms. – Regulators in mammals keep extracellular fluid composition constant, regulating temperature, […]

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1. Overview of Homeostasis:
– Homeostasis maintains optimal conditions for metabolic processes in organisms.
– Regulators in mammals keep extracellular fluid composition constant, regulating temperature, pH, and concentrations of ions.
– Homeostatic mechanisms control various aspects of human physiology.
– Circadian variations affect body temperature throughout the day.
– Homeostasis regulates core body temperature with temperature sensors in the brain.

2. Mechanisms of Homeostasis:
– Homeostatic mechanisms involve receptors, control centers, and effectors.
– Receptors monitor and respond to changes in the environment.
– Control centers set maintenance ranges for variables like temperature.
– Effectors bring about changes to return the variable to its normal state.
– Negative feedback loops stop the need for further signaling once the variable is regulated.

3. Examples of Homeostasis in Action:
– Cannabinoid receptors like CB1 modulate neurotransmitter release for homeostasis.
– Polyunsaturated fatty acids play a role in fine-tuning body homeostasis.
– Homeostatic control mechanisms regulate variables like blood pressure in mammals.
– Sensors detect changes in variables like blood pressure and signal control centers in the brain.
– Effector responses, like heart rate changes, help reverse errors in blood pressure to maintain homeostasis.

4. Regulation of Specific Variables:
– Core temperature is regulated by input from thermoreceptors in various body parts.
– Allostasis can adjust behavior in extreme temperatures.
– Behavioral thermoregulation takes precedence over physiological regulation.
– Blood flow to extremities is reduced in cold weather to minimize heat loss.
– Metabolic rate increases to generate heat in response to low core temperature.

5. Regulation of Blood Glucose, Iron, and Copper Levels:
– Blood sugar levels are tightly regulated in mammals through insulin and glucagon.
– Iron regulation is crucial for human health and disease due to the complexity of iron metabolism.
– Copper homeostasis is vital for overall health, as maintaining proper levels is critical to prevent health problems related to copper imbalance.

Homeostasis (Wikipedia)

In biology, homeostasis (British also homoeostasis; /hɒmiˈstsɪs, -miə-/) is the state of steady internal physical and chemical conditions maintained by living systems. This is the condition of optimal functioning for the organism and includes many variables, such as body temperature and fluid balance, being kept within certain pre-set limits (homeostatic range). Other variables include the pH of extracellular fluid, the concentrations of sodium, potassium, and calcium ions, as well as the blood sugar level, and these need to be regulated despite changes in the environment, diet, or level of activity. Each of these variables is controlled by one or more regulators or homeostatic mechanisms, which together maintain life.

Homeostasis is brought about by a natural resistance to change when already in optimal conditions, and equilibrium is maintained by many regulatory mechanisms; it is thought to be the central motivation for all organic action. All homeostatic control mechanisms have at least three interdependent components for the variable being regulated: a receptor, a control center, and an effector. The receptor is the sensing component that monitors and responds to changes in the environment, either external or internal. Receptors include thermoreceptors and mechanoreceptors. Control centers include the respiratory center and the renin-angiotensin system. An effector is the target acted on, to bring about the change back to the normal state. At the cellular level, effectors include nuclear receptors that bring about changes in gene expression through up-regulation or down-regulation and act in negative feedback mechanisms. An example of this is in the control of bile acids in the liver.

Some centers, such as the renin–angiotensin system, control more than one variable. When the receptor senses a stimulus, it reacts by sending action potentials to a control center. The control center sets the maintenance range—the acceptable upper and lower limits—for the particular variable, such as temperature. The control center responds to the signal by determining an appropriate response and sending signals to an effector, which can be one or more muscles, an organ, or a gland. When the signal is received and acted on, negative feedback is provided to the receptor that stops the need for further signaling.

The cannabinoid receptor type 1 (CB1), located at the presynaptic neuron, is a receptor that can stop stressful neurotransmitter release to the postsynaptic neuron; it is activated by endocannabinoids (ECs) such as anandamide (N-arachidonoylethanolamide; AEA) and 2-arachidonoylglycerol (2-AG) via a retrograde signaling process in which these compounds are synthesized by and released from postsynaptic neurons, and travel back to the presynaptic terminal to bind to the CB1 receptor for modulation of neurotransmitter release to obtain homeostasis.

The polyunsaturated fatty acids (PUFAs) are lipid derivatives of omega-3 (docosahexaenoic acid, DHA, and eicosapentaenoic acid, EPA) or of omega-6 (arachidonic acid, ARA) are synthesized from membrane phospholipids and used as a precursor for endocannabinoids (ECs) mediate significant effects in the fine-tuning adjustment of body homeostasis.

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