4.3 Homeostatic mechanisms and stimulus–response models Flashcards
What is homeostasis and what does it involve monitoring?
Homeostasis is the body’s attempt to maintain a constant and balanced internal environment.Homeostasis requires monitoring the level of variables involves comparing the current level against the value of its set point.
What is the set point of temperature?
36.1–37.2 °C
What two body systems help maintain homeostasis and how do they do it and how do they communicate?
The nervous and endocrine system. Their critical role is in the communication of signals. Communication in the nervous system occurs through electrochemical signals that are transmitted by neurons. The endocrine system communicates through hormones that are released by endocrine glands into the blood stream and travel to target organs.
What can Stimulus–response feedback models used to show?
Stimulus–response feedback models can be used to show how homeostatic mechanisms act in the body and maintain a fairly constant state.
What are the 5/6 components of a stimulis-response feedback model?
Stimulus: a change, either an increase or a decrease, in the level of an internal variable E.g change in body temp
Receptor: the structure that detects the change and sends signals to the control centre
Control centre: the structure (central nervous system) that evaluates the change against the set point for that variable and sends signals to the effector about the correction needed
Effector: the structure that adjusts its output to make the required correction
Response: the corrective action taken
An additional process in the closed homeostatic stimulus response loop model is feedback:
Negative feedback: the counteracting or negating effect of the response on the stimulus. The negative feedback is that the temp ha now returned to normal.
What is the difference between the stimulus-response feedback model and negative feedback loop?
Outcome: The stimulus-response feedback model results in a direct response to a stimulus, whereas the negative feedback loop results in the regulation of a system to maintain homeostasis.
Parts of a stimulus response model with feedback
1)Stimulus 2)Receptor 3)Control centre 4)Effector 5)Response 6)Feedback > recocurring
What is the objective a negative feedback loop?
A negative feedback loop is all about how to reduce or raise conditions back towards homeostasis.
What is positive feedback?
Outline the steps of the negative feedback loop of the thyroid hormone secretion.
Specific cells in the hypothalamus are stimulated by signals such as stress, cold and nutritional status to release thyrotropin-releasing hormone (TRH).
TRH travels via the blood to the anterior pituitary, which responds by releasing thyroid-stimulating hormone (TSH).
TSH is carried by the blood to the thyroid gland, which is stimulated to release its T3 and T4 hormones (the response).When the circulating thyroid hormones increase above a particular level, negative feedback mechanisms come into play. They inhibit the production of TSH by the anterior pituitary and TRH by the hypothalamus, stopping the release of T3 and T4.
Identify why is homeostasis important for sustaining life.
What role does the control centre have in the homeostatic stimulus–response model?
The control centre evaluates the change against the set point for that variable and sends signals to the effector about the correction needed.
Would you expect the normal range for blood pressure to be the same across all animals? Why/why not?
No (1 mark). Organisms have different requirements depending on their body structure and their environment, and different tolerance limits (1 mark).
Identify a difference between an open stimulus–response model and a homeostatic closed loop model .
In a homeostatic closed loop model, the stimulus and the response are related to the same variable, but are opposite in their direction — when the stimulus changes the value of an internal variable, the response is a change in opposite direction of that variable.
In an open stimulus–response model, the stimulus and the response are unrelated in kind and the response has no effect on the stimulus.
What is the difference between negative and positive feedback?
Negative feedback refers to a situation in which the response to a stimulus counteracts the stimulus — it returns the variable to its required range (1 mark).
Positive feedback refers to a situation in which the response to a stimulus amplifies it
