31. The diagram below illustrates a negative feedback loop that is used to homeostatically control a. Question
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31. The diagram below illustrates a negative feedback loop that is used to homeostatically control a regulated variable in the extracellular fluid (ECF). Refer to the diagram and answer questions below.
a) What is the regulated variable that is being controlled in this feedback loop?
b) As shown in the diagram- where exactly is the integrating centre that receives the signal from the stimulus and acts on it?
c) Which of the body’s control systems is/are involved in this feedback loop?
d) In this feedback loop, what is the output signal from the integration centre?
e) What are the main target cells for output signal?
f) Explain in detail one mechanism that target cells use in order to facilitate a decrease in plasma glucose levels?
g) What is the stimulus that activates the feedback loop?
h) Explain what is meant by “increased transport” as a response by some of the target tissue.
32. Consider synaptic transmission at a chemical synapse and answer questions a) to e) below:-.
a) What type of signal do the calcium channels at the synaptic terminal need to receive in order to open?
b) Where are neurotransmitters stored in neurons and what causes them to be released? What is the mechanism of release ?
c) What is the role of the neurotransmitter, once released ?
d) What is an excitatory post-synaptic potential (EPSP) and where does it occur?
e) How is the neurotransmitter signal terminated- give details of mechanisms?
33. Consider an Action potential that is initiated at the axon hillock and propagated down the axon and answer the following questions:-
a) Explain what is meant by ‘Threshold Potential’?
b) When a neuron is at rest which of the listed channels are open and which are closed?? Voltage gated sodium channels Voltage gated potassium channels Sodium leak channels Potassium leak channels
c) Describe the structure of a voltage gated sodium channel and how it differs from the potassium voltage gated channel. Explain the role these channels play in the action potential.
d) In order for an action potential to be generated, a positive feedback loop must be established. Describe the two factors that happens to interrupt the loop. When, during the action potential do these factors occur ?
e) What does repolarisation mean and what causes the repolarisation phase of the action potential?
f) What is meant by the absolute refractory period, and what causes it?
g) What does hyperpolarisation mean, and what causes the hyperpolarisation phase of the action potential?
h) During an action potential, do the sodium and potassium concentration gradients ever reverse across the cell membrane?
i) How is sodium removed from the cell once it enters?
SCIENCE
HEALTH SCIENCE
NURSING
HEALTH SCI HBIO1007
31. The diagram below illustrates a negative feedback loop that is used to homeostatically control a
