Download Negative Feedback

Warm-Up (3/3)
If high concentrations of glucose build
up outside a cell, how does a cell absorb
some of the glucose?
Hint: go back to your “Diffusion” notes.
Name
Date
Period
2C.1a: Negative feedback mechanisms maintain dynamic homeostasis for a
particular condition (variable) by regulating physiological processes, returning the
changing condition back to its target set point.
Illustrative example: temperature regulation in animals
2C.1b: Positive feedback mechanisms amplify responses and processes in
biological organisms. The variable initiating the response is moved farther away
from the initial set point. Amplification occurs when the stimulus is further activated
which, in turn, initiates an additional response that produces systemic change.
Illustrative example: lactation in mammals
2C.1c: Alterations in the mechanisms of feedback often results in deleterious
consequences.
Illustrative example: dehydration in response to decreased antidiuretic
hormone (ADH)
2C.2a: Organisms response to changes in their environment through behavioral
and physiological mechanisms.
Illustrative example: shivering and sweating in humans
Negative Feedback
Homeostasis is the balance of
levels of two things.
Negative feedback regulates to
return systems to homeostasis.
Levels of
hormone A
Levels of
bodily
function
B
Negative Feedback
Homeostasis is the balance of
levels of two things.
For example, temperature regulation
Negative feedback regulates to
return systems to homeostasis.
Hippocampus
hormones
98.6°F
Temperature
Negative Feedback
Homeostasis is the balance of
levels of two things.
For example, temperature regulation
if temperature drops,
hormones released
Negative feedback regulates to
return systems to homeostasis.
Temperature
Re-regulated
Negative Feedback
Homeostasis is the balance of
levels of two things.
Negative feedback regulates to
return systems to homeostasis.
Hippocampus
hormones
For example, temperature regulation
if temperature drops,
hormones released,
temperature returns to normal.
98.6°F
Temperature
Negative Feedback
Homeostasis is the balance of
levels of two things.
For example, temperature regulation
if temperature drops,
hormones released
Negative feedback regulates to
return systems to homeostasis.
Shivering
Negative Feedback
Homeostasis is the balance of
levels of two things.
For example, temperature regulation
if temperature raises,
hormones released
Negative feedback regulates to
return systems to homeostasis.
Sweating
Negative Feedback
Homeostasis is the balance of
levels of two things.
For example, hydration regulation
Negative feedback regulates to
return systems to homeostasis.
Antidiuretic
hormone (ADH)
from kidneys
Normal
water
balance
Negative Feedback
Homeostasis is the balance of
levels of two things.
For example, hydration regulation
if cells become dehydrated,
ADH released
Negative feedback regulates to
return systems to homeostasis.
Kidneys
release water
(urine more
concentrated)
Negative Feedback
Homeostasis is the balance of
levels of two things.
Negative feedback regulates to
return systems to homeostasis.
Antidiuretic
hormone (ADH)
from kidneys
For example, hydration regulation
if cells become dehydrated,
ADH released,
water balance restored.
Normal
water
balance
Negative Feedback
Homeostasis is the balance of
levels of two things.
Negative feedback regulates to
return systems to homeostasis.
For example, hydration regulation
if cells become overhydrated,
less ADH released
Negative Feedback
Homeostasis is the balance of
levels of two things.
For example, hydration regulation
if cells become overhydrated,
less ADH released
Negative feedback regulates to
return systems to homeostasis.
Kidneys
absorb water
(urine more
diluted)
Negative Feedback
Homeostasis is the balance of
levels of two things.
Negative feedback regulates to
return systems to homeostasis.
Antidiuretic
hormone (ADH)
from kidneys
For example, hydration regulation
if cells become overhydrated,
less ADH released,
water balance restored.
Normal
water
balance
Critical Thinking Question #1
Insulin is a hormone ligand which binds to the insulin receptor and stimulates
the absorption of glucose from the bloodstream into cells. When blood glucose
levels are high, the pancreas increases insulin levels; when blood glucose
levels are low, the pancreas releases less insulin. A graph is plotted below
showing the levels of glucose and insulin in a single person over a period of 24
hours.
Explain why the graph shows relatively low concentrations of insulin at 12
hours but relatively high concentrations of glucose, and predict what the
glucose curve would look like if the pancreas failed to produce insulin.
2C.1a: Negative feedback mechanisms maintain dynamic homeostasis for a
particular condition (variable) by regulating physiological processes, returning the
changing condition back to its target set point.
Illustrative example: temperature regulation in animals
2C.1b: Positive feedback mechanisms amplify responses and processes in
biological organisms. The variable initiating the response is moved farther away
from the initial set point. Amplification occurs when the stimulus is further activated
which, in turn, initiates an additional response that produces systemic change.
Illustrative example: lactation in mammals
2C.1c: Alterations in the mechanisms of feedback often results in deleterious
consequences.
Illustrative example: dehydration in response to decreased antidiuretic
hormone (ADH)
2C.2a: Organisms response to changes in their environment through behavioral
and physiological mechanisms.
Illustrative example: shivering and sweating in humans
Negative Feedback
Positive feedback further moves
the system away from
homeostasis.
Levels of
hormone A
Levels of
bodily
function
B
Negative Feedback
Positive feedback further moves
the system away from
homeostasis.
Hypothetical example:
Bodily function B drops,
Negative Feedback
Positive feedback further moves
the system away from
homeostasis.
Hypothetical example:
Bodily function B drops,
Hormone A promotes activated,
Negative Feedback
Positive feedback further moves
the system away from
homeostasis.
Hypothetical example:
Bodily function B drops,
Hormone A promotes activated,
bodily function B drops further.
Negative Feedback
Positive feedback further moves
the system away from
homeostasis.
Hypothetical example:
Bodily function B drops,
Hormone A promotes activated,
bodily function B drops further,
Hormone A promotes activated,
bodily function B drops further.
Negative Feedback
Positive feedback further moves
the system away from
homeostasis.
Actual example: Lactation
Milk gets suckled,
Hormone released to produce milk,
More milk get suckled,
More milk produced.
Critical Thinking Question #2
The sjf1 gene encodes a transcription factor
which activates several genes, including its
own gene. Explain how a signal
transduction pathway which leads to
activation of the sjf1 gene will be amplified
through positive feedback.
Closure
On the piece of white paper from the
back, answer the following question:
Explain how chronic (long-term)
exposure to high glucose levels
leads to insensitivity to insulin
signaling, a condition known as
diabetes mellitus.
Name
Date
Period
Scale
1 – 10