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5.1 Communication and Homeostasis - Coggle Diagram
5.1 Communication and Homeostasis
Homeostasis
Homeostasis
Homeostasis is the maintenance of a stable internal environment within restricted limits in organisms.
This ensures that cells function normally despite changes in the external environment.
Why is it important?
It keeps the internal environment constant for metabolic reactions.
It ensures cells function properly and avoid damage.
It helps organisms respond and adapt to external changes.
Control Mechanisms
Homeostasis is coordinated by several different control mechanisms, consisting of receptors, coordinators, and effectors throughout the body.
Receptors - These sensory receptors detect stimuli and send signals to the brain about changes in the internal environment, like changes in blood pH and temperature.
Coordinator - This receives and interprets information from receptors and sends instructions to an appropriate effector.
Effectors - These are muscles or glands that act on signals from the brain and cause responses to reverse changes and regain equilibrium, such as sweating to reduce high temperature.
These control mechanisms aim to maintain conditions around an optimum point: the point at which the system operates best.
Negative Feedback Systems
Negative feedback systems involve coordination between receptors and effectors to control conditions around set optimum points, where the system works best. A derivation from the optimum point leads to changes that bring the system back to the optimum point.
How it works:
Receptors detect a change in one direction, like rising blood glucose.
Signals trigger effectors to produce responses that reverse the initial change, like releasing insulin to lower blood glucose.
Conditions return to their set range.
Examples
Maintaining Blood Glucose Concentration
Why it is important - Glucose is needed for respiration, but too much glucose can affect water potential in blood and cells.
How it is achieved - Insulin and glucagon adjust blood glucose concentration to maintain a healthy supply of glucose.
Maintaining Blood pH
Why it is important - Changes in pH can impair enzyme action.
How it is achieved - Adjustments are made to the acid-base balance in the blood to maintain the optimum pH.
Maintaining Temperature
Why it is important - Changes in temperature can impair enzyme action.
How it is achieved - Adjustments are made, for instance by sweating or shivering, to maintain the optimum temperature.
Water Regulation
Why it is important - Too much or too little water in the blood and cells can cause cells to burst or shrink due to osmosis.
How it is achieved - Water is removed or reabsorbed from blood or tissue fluid to maintain the optimum water potential.
Positive Feedback Systems
Positive feedback, in contrast to negative feedback, amplifies changes rather than reversing them. In other words, a deviation from an optimum causes changes that result in an even greater deviation from the optimum point.
How it works:
An initial change occurs, like the release of clotting factors after a blood vessel injury.
Effectors are stimulated and enhance the change, like more clotting factors being released.
The change continues until an endpoint is met, like a clot being fully formed.
Examples
Positive feedback is less common than negative feedback in homeostasis, as uncontrolled responses can disrupt the body's equilibrium. Tight regulation is essential to prevent harm when changes intensify in these systems.
Childbirth - Oxytocin stimulates more uterine contractions.
Blood clotting - Clotting factors activate further clotting.
Cell Signalling
Cell signalling is the process by which cells communicate. It can occur between adjacent cells, like when neurones release neurotransmitters to stimulate nearby nerve cells or muscle cells, or between very distant cells.
How it works:
Cells can communicate by releasing hormones.
These hormones travel in the blood and signal to target cells that may be far away.
Cell-surface receptors enable cells to recognise and respond to these hormones.
Thermoregulation
Thermoregulation
Thermoregulation is the process of maintaining a relatively constant core body temperature. This is important to maintain optimum enzyme activity.
Ectotherms
Examples- Reptiles, Fish
Definition- Animals that use their surroundings to regulate their body temperature
Control of Body Temperature- Can only regulate body temperature through behavioural changes like basking in the sun or seeking shade
Variation in Body Temperature- Internal temperature is influenced by environmental temperatures
Activity Level- Activity increases with warmer environmental temperatures and decreases when it's cooler
Metabolic Rate- Metabolic rate varies and the organism generally produces minimal heat on its own
Endotherms
Examples- Mammals, birds
Definition- Animals that rely on their metabolic processes to control their body temperature
Control of Body Temperature- Regulate body temperature through internal processes and behavioural changes
Variation in Body Temperature- Internal temperature is relatively stable and less influenced by changes in environmental temperature
Activity Level- Can remain active across a range of temperatures
Metabolic Rate- The organism sustains a high and steady metabolic rate, producing large amounts of heat through metabolism
Mechanisms of Thermoregulation in Mammals
To reduce body temperature when it is too high:
Increased sweating - Effector sweat glands produce more sweat to promote evaporative cooling.
Flattening hair - Effector erector pili muscles relax, flattening hairs and reducing insulation.
Vasodilation - Effector arterioles near the skin dilate, increasing blood flow to the skin and heat radiation from the skin surface.
To increase body temperature when it is too low:
Shivering - Effector skeletal muscles contract to generate heat through increased cellular respiration, an exothermic reaction.
Minimising sweating - Effector sweat glands produce less sweat, which helps to conserve body heat.
Erecting hair - Effector erector pili muscles contract, raising hairs, trapping a layer of warm air, and increasing insulation.
Vasoconstriction - Effector arterioles near the skin constrict, reducing blood flow to the skin and heat radiation from the skin surface.
Releasing adrenaline and thyroxine - Effector glands release these hormones to speed up cellular metabolism, which produces more heat.
The Role of the Hypothalamus in Controlling Body Temperature
The hypothalamus is the thermostat of the brain, and is crucial in coordinating thermoregulation in mammals.
How it works:
The hypothalamus collects information about core body temperature from temperature receptors in the hypothalamus and about surface temperature from peripheral receptors in the skin.
This information is processed in the hypothalamus to detect deviations from normal levels in core and surface body temperature.
The hypothalamus then sends signals to effectors like muscles and sweat glands.
These effectors implement mechanisms to restore the ideal temperature.
This homeostatic process lets mammals maintain a stable internal temperature, even when external temperatures fluctuate.
The heat loss and heat gain centres in the hypothalamus
When blood temperature increases:
Impulses are sent to the heat loss centre in the hypothalamus.
This sends impulses to the effector organs to increase heat loss.
The body temperature returns to the optimum point.
When blood temperature decreases:
Impulses are sent to the heat gain centre in the hypothalamus.
This sends impulses to effector organs to reduce heat loss.
The body temperature returns to the optimum point.