Homeostasis Flashcards
descrbie the difference between a stimulus an a response
what is the purpose of homeostasis
clarify how positive and negative feedback differ. suggest why positive feedback is generally not associated with homeostasis.
what are the by products of cellular respiration
differentiate between a tolerance range and optimal range
explain the differences between cellular respiration and metabolic activity
explain difference between ectotherms and endotherms
define homeostasis
the process by which the body maintains a constant internal environment, this is done by nerves and hormones. it is important because many reactions (enzymes) only work at certain conditions
what is the reange of deviation called
tolerance limits are the range of deviation that is acceptible for certain varations such as temperature, blood glucose levels, etc.
define the stimulus response model
the body’s way of detecting a change in its external or internal environment, and reacting accordingly.
what is regulation
regulation is responding to fluctuations around a set point.
define negative feedback loop
information produced by the feedback causes a reversal in the effect of the stimulus
describe in general terms how an organism maintains its internal environment within tolerance limits
homeostasis is the process by which the body maintains a stable internal environment through a stimulus-response negative feedback model, which works as follows:
- stimulus: change in the internal or external environment
- receptor: receptor detects stimulus
- central nervous system: receptor produces a signal to send to the central nervous system to coordinate a response
- effector: central nervous systems send message to an effector, such as muscles or glands
- response: effector conducts a response to restore the body to its balanced state.
Negative feedback mechanisms are typically used to maintain homeostasis.
Describe the main features of a negative feedback mechanism.
Change in internal environment (stimulus)
Receptor detects the change
Signal sent from receptor to the control centre (central nervous system) and processed
Signal sent from the control centre to the appropriate effector
Effector responds to the signal and restores homeostasis (reverses the effect of the stimulus)
Outline the role of the effector in homeostasis.
An effector is responsible for amending a homeostatic imbalance that has been communicated to the control centre. Effectors are either muscles or glands. Muscles will either expand or contract, whereas glands will release a secretion.
Outline the role of receptors in homeostasis.
Receptors detect changes in homeostasis. There are a variety of different types of receptor, all of which are able to respond to different types of stimuli. These receptors operate according to set levels. When they detect a deviation from a set level, the receptor sends a signal to the control centre.
define endotherm
warm-blooded, largely create heat by adjusting processes in their bodies (we are endotherms), rely mainly on physiological sources of heat to regulate internal temperature
define ectotherm
cold-blooded, rely on external sources of temperature to heat up or cool down, depend solely on the environment for heat regulation.
physiological responses to cold to reduce heat loss
- piloerection. hairs erect on your skin, trap air close to skin, preventing heat loss via the convection of air.
- vasoconstriction. blood vessels constrict, so less blood travels near the skin’s surface. Less heat is lost from the blood
physiological responses to cold to increase heat production
- shivering. muscle cells perform respiration in order to break down glucose and make energy. respiration releases heat.
- increasing metabolism. main source of heat production when your body is at rest. endocrine system can be used to influence the production of heat via metabolism.
behavioural responses to cold to both reduce heat loss and increase heat production
reduce heat loss: seeking shelter, putting on clothing, decreasing surface area.
increasing heat production: voluntary movement.
responding to heat, physiological processes to increase heat loss.
- vasodilation, blood actively losses heat to the external environment.
- sweating, from by glands on skin, this draw heat from the skin to evaporate the sweat, converting a liquid to a gas.
responding to heat, physiological processes to reduce heat production
- decreasing metabolism, in response to heat, the hypothalamus reduces the rate of cellular respiration in the bodies internal organs
Conduction, convection, radiation and evaporative cooling are the four ways we exchange heat with our environment, not rumination!
Identify TWO responses of a named endotherm to a decrease in body temperature.
Shivering and vasoconstriction in humans.
Outline the role of the nervous system of an endotherm in maintaining homeostasis when its body temperature changes.
Changing body temperature is detected using temperature receptors in the skin and brain. A signal is sent via nerves from the receptors to the central nervous system. Nerve signals are then sent from the CNS to effectors (muscles or glands).
Explain how humans maintain homeostasis in response to changes in temperature.
The human sensory nervous system is responsible for detecting changes in temperature. Specific receptors on the skin are designed to detect specific temperatures and transmit that information along nerves to the brain. In response, effector tissues are activated to adapt to the detected changes and maintain homeostasis. For example, in response to cold, humans will shiver to generate heat in the muscles. This maintains a constant internal temperature.
Distinguish between endotherms and ectotherms.
The body temperature of ectotherms is regulated by the ambient, or environmental temperature, as they are unable to generate heat themselves. Endotherms thermoregulate by modifying their internal body processes, using a negative feedback loop where a change in body temperature (stimulus) is detected by a thermoreceptor (receptor). This change is interpreted by the central nervous system (control centre) which activates an effector, producing a response which cancels out the original stimulus.
Describe one structural feature and one physiological process that enables mammals living in cold environments to maintain a constant core body temperature. Identify clearly in your answer which is the structural feature and which is the physiological process.
Structural feature: Thick fur coat
Traps layer of air close to body, providing insulation
This reduces heat loss by conduction
Stops air flow close to body, reduces heat loss by convection
Hairs may be hollow (more insulation from hollow core)
Furry tail can be folded over nose/extremities to improve insulation
Physiological process: Vasoconstriction
Blood vessels in skin constrict
Restrict blood flow to skin, reducing temperature of skin
Reduces heat loss through radiation
Most blood remains below the insulating fat layer
Rabbits have the ability to control the amount of blood flow to their ears.
Explain how this can help them to thermoregulate.
Rabbits are endothermic, meaning that they maintain a constant internal temperature regardless of the temperature of the environment. The blood flowing from the body to the ears is relatively warm. The ear is in close contact with air, therefore heat in blood can be lost via the ear. If the air temperature is warm, rabbits increase the blood flow to their ears through vasodilation. This increases heat loss by radiation (and/or by convection if the rabbit is moving). If air temperature is cold, rabbits decrease the blood flow to their ears through vasoconstriction. This retains heat in their body (rather than losing heat to the environment).
what is osmoregulation
the control of the concentration of body fluids, in order to maintain water balance, it controls how much water there is compared to other dissolved substances (solutes) in the body.
