BIPN 100 Lecture Notes - Lecture 3: Negative Feedback, Action Potential, Positive Feedback

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chocolatebeetle359

13 Jun 2018

School

UCSD

Department

Biology/Animal Physiol & Neurosc

Course

BIPN 100

Professor

Dr. Kimberley Cooper

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BIPN 100 Lecture 3

4/6/2018

• Nervous and endocrine systems are in charge of regulating physiological state

• Homeostasis is maintained by feedback loops

o Negative feedback loops

▪ Maintain homeostasis

▪ Reverse a change in a controlled condition

▪ Variables tend to remain at constant values

▪ There is an odd number of negative signs in a negative feedback loop

▪ E.g. temperature regulation, blood glucose, BP

• BP: stimulus leads to an increase in PB (BP is the

controlled/physiological variable). The baroreceptors are the

receptors that detect this change and send an input via a verse

impulse to the brain (the integrator). The brain makes an output

via another nerve impulse to the heart (the effector) to decrease

HR and BP (this is the response) to return to a homeostatic range

o Positive feedback loops

▪ Strengthens or reinforces a change in the controlled variable

▪ No sign inversion or there is an even number of negative signs in the

feedback loop

▪ Are ofte pathologial, istaes where they are’t are i lood lottig

and child birth

▪ E.g. fever

• Positive feedback loop. You get an infection. Immune system kicks

i ad WBC’s attak. Iue syste releases heial i the

blood that travel to the hypothalamus which tells it to elevate the

set point for body temperature. Now the rai thiks you’re old

because the set point has been raised. The body tries to raise

body temperature by shivering and having a fever, causing the

fever to rise to kill the infection. What stops this is the infection

being killed

• Voltage

o A form of potential energy that acts as the driving force causing current

• Current

o Flow of charge

• Resistance

o Impedes flow

• When separated, charges may move freely if a conductor is present, or may remain

separated if an insulator is present (e.g. a cell membrane)

• Electrical charges move only if there is both a driving force and a pathways (e.g. the

voltage and a channel)

• Oh’s law desries this

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Document Summary

The baroreceptors are the receptors that detect this change and send an input via a verse impulse to the brain (the integrator). The brain makes an output via another nerve impulse to the heart (the effector) to decrease. Immune system kicks i(cid:374) a(cid:374)d wbc"s atta(cid:272)k. i(cid:373)(cid:373)u(cid:374)e syste(cid:373) releases (cid:272)he(cid:373)i(cid:272)al i(cid:374) the blood that travel to the hypothalamus which tells it to elevate the set point for body temperature. Now the (cid:271)rai(cid:374) thi(cid:374)ks you"re (cid:272)old because the set point has been raised. The body tries to raise body temperature by shivering and having a fever, causing the fever to rise to kill the infection. What stops this is the infection being killed: voltage, a form of potential energy that acts as the driving force causing current, current, flow of charge, resistance. Is the electrical gradient between the ecf and the icf: electrochemical gradient.

Related Questions

Define: physiology, homeostasis, dynamic constancy, variable,range.

What are the four requirements for a feedback loop? Be able toexplain their role in feedback loops.

What is a negative feedback loop? What is a positive feedbackloop? Be able to give an example of each type of feedback loop.What is dynamic constancy?

Why are negative feedback loops preferentially used to maintainhomeostasis?

Why are antagonistic feedback processes used for negativefeedback loops?

Compare and contrast the two main regulatory mechanisms forhomeostasis (endocrine and nervous systems).

Know the organ systems and their functions and the differencesbetween exocrine and endocrine glands. This is more of a âkeepthese in mindâ rather than something that will be tested onLE#1.

What is the Law of Mass Balance?

How is blood glucose regulated?

1) The human body's arterial blood pH is tightly maintainedaround 7.4 by buffering agents that bind hydrogen ions to stop anychange in pH. If an acid-base imbalance overcomes the buffersystem, the body changes the ventilation rate, or the rate at whichgas enters or leaves the lungs. Changing the ventilation ratechanges the concentration of CO₂ in the blood, whichalters the pH of the blood. In this case, the muscles that controlthe ventilation rate are acting as the:

		homeostatic challenge
		sensor
		effector
		integrator

2) For cells to maintain an appropriate solute concentration,_____ will occur; for cells to maintain an appropriate waterconcentration, _____ will occur.

		diffusion, osmosis
		osmosis, diffusion
		diffusion, facilitated diffusion
		diffusion, active transport

3) A marine fish with a cold body temperature that matches itscold surroundings is an example of

		negative feedback
		regulating
		conforming
		homeostasis

4) Fiddler crabs are small crabs that inhabit intertidal areas.When the tide comes in, the salinity rises to 35ppt and when thetide leaves, the salinity falls to 5ppt. Fiddler crabs can maintaintheir internal salinity at 32ppt when the external environmentranges from 20-40ppt, but cannot regulate at levels higher or lowerthan this. The range of 20-40ppt is the ____________________ forthese animals.

		zone of conforming
		zone of stability
		osmoregulatory conforming capacity
		positive feedback effector range

Complete Question Text:

1. A patient comes to a doctor complaining of muscle cramping.As part of her examination, the doctor notes that the patient has aslow pulse. Additionally, in the past year the patient has brokenher hand and her arm in seemingly minor falls. What variable do youpredict the patient is having trouble regulating?

Fat
K+
ATP
Ca2+

2. Allen's rule is a biological rule that states that the limbsof warm blooded animals that live in colder climates are differentthan the limbs of the same species of animals in warmer climates.In what way do you expect them to be different and why?

Shorter because a low surface area to volume ratio is best formaintaining heat
Longer because a high surface area to volume ratio is best formaintaining heat. ????
Longer because a low surface area to volume ratio is best formaintaining heat
Shorter because a high surface area to volume ratio is best formaintaining heat.

3. Pepsin is a digestive enzyme. It is made in an inactive form,pepsinogen, which is activated by the acidity of the stomach toself-cleave (cut itself) into a formed called the cleaved molecule.This cleaved molecule is active pepsin, which goes on to cleavemore pepsinogen molecules, leading to a cascade of rapid pepsinactivation (and many more active pepsin molecules). This pathway isan example of:

a feedforward regulationâ¨
a positive feedback loopâ¨
a negative feedback loopâ¨
conditioning

4. The human body's arterial blood pH is tightly maintainedaround 7.4 by buffering agents that bind hydrogen ions to stop anychange in pH. If an acid-base imbalance overcomes the buffersystem, the body changes the ventilation rate, or the rate at whichgas enters or leaves the lungs. Changing the ventilation ratechanges the concentration of CO2 in the blood, which alters the pHof the blood. In this case, the muscles that control theventilation rate are acting as the:

homeostatic challenge
sensor
effector
integrator

5. The human body's arterial blood pH is tightly maintainedaround 7.4 by buffering agents that bind hydrogen ions to stop anychange in pH. If an acid-base imbalance overcomes the buffersystem, the body changes the ventilation rate, or the rate at whichgas enters or leaves the lungs. Changing the ventilation ratechanges the concentration of CO2 in the blood, which alters the pHof the blood. In this case, pH 7.4 is the:

homeostatic challenge
sensor
effector
set point

6. What is the equivalent of the mammalian mouth and nose in therespiratory system of insects?

alveoli
spiracles
tracheoles
epithelial tissue

7. For cells to maintain an appropriate solute concentration,_____ will occur; for cells to maintain an appropriate waterconcentration, _____ will occur.

diffusion, osmosis
osmosis, diffusion
diffusion, facilitated diffusion
diffusion, active transport

8. A marine fish with a cold body temperature that matches itscold surroundings is an example of

negative feedbackâ¨
regulating
conforming
homeostasis

9 Fiddler crabs are small crabs that inhabit intertidal areas.When the tide comes in, the salinity rises to 35ppt and when thetide leaves, the salinity falls to 5ppt. Fiddler crabs can maintaintheir internal salinity at 32ppt when the external environmentranges from 20-40ppt, but cannot regulate at levels higher or lowerthan this. The range of 20-40ppt is the ____________________ forthese animals.

zone of conforming
zone of stability
osmoregulator conforming capacity
positive feedback effector range

10. Imagine you are entering a darkened cavern. You are excited,but also a little nervous. Your heart rate quickens, your bloodpressure rises slightly, and your digestive system activitydecreases as blood is diverted to your musclesâall changes thatprepare you should you need to move rapidly. This type of change isan example of:

positive feedback control
negative feedback control
a failure of homeostasis
feedforward regulation

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BIPN 100 Lecture Notes - Lecture 3: Negative Feedback, Action Potential, Positive Feedback

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