Reading assignment: Chapter 1 and other material specifically referenced
What is life?
from an intro text)
showing a cell
If this were the first lecture for introductory biology, we would ask, "What
is unique to life?" and we might argue that "Inside the cell is
alive. Outside is not. The plasma membrane is thus the gate-keeper that
separates the quick from the dead."(1) Then we would develop the following
#1. Life is very complex.
#2. Life has excitability.
#3. Life has development.
#4. Life utilizes metabolism.
#5. Life's processes are regulated by homeostasis
#6. Evolution is major unifying principle
#7. Reproduction is fundamental
In introductory biology (but not in physiology), we would concentrate on:
#1. Life is very complex and has complex macromolecules (DNA, RNA, protein).
#3. Life has development, growth, form
#6. Evolution is major unifying principle, and present-day organisms have
an unbroken ancestry of 3 1/2 billion yrs
#7. Reproduction is fundamental causing us to define "survival"
in biology in terms of reproduction and production of fertile offspring.
What is Physiology?
In Physiology, we will concentrate on:
#2. Life has excitability, movement and responsiveness (irritability, sensitivity)
Excitability - Copy of a page
from a mathematically oriented text from 1971 text (2)
In the mid-1800's, it might be hard to distinguish a physiologist and a
physicist, and Helmholtz made contributions in both disciplines.
Nervous system -Copy of a page
from the book I used when I took physiology in 1969 (3), by Sir
Bernard Katz, (Nobel Prize, 1970), one of many neuroscientists to win
the Nobel Prize in Physiology
#4. Life utilizes metabolism, and we will concentrate on:
Catabolic processes, for the production and delivery of energy. (However,
we will not dwell on the bioenergetics coverage as much as "BL A302
Cellular Biochemistry and Molecular Biology.")
(to a lesser extent) Anabolic processes, involving build-up. (You have heard
the term "anabolic steroids," such as testosterone and drugs of
abuse among athletes.)
Perhaps, foremost, in Physiology, we will concentrate on
#5. Life's processes are regulated by homeostasis
Homeostasis: the thermostat
A fundamental example is the thermostat.
Negative feedback is sometimes referred to as a servo mechanism.
The thermostat works by negative feedback.
In house, "effector" would be furnace heat
Heat (energy) is what changes temperature.
1 calorie raises temperature of 1 ml of water 1 degree C
(the "calories" you "count" in a diet are kcal's)
Importantly, it takes about 540 calories to turn 1 ml of water to vapor.
Thus, for evaporation, we lose a lot of heat by panting or sweating.
This is called "insensible" water loss, not because it does not
make sense but because you are not aware of it as you are for micturation.
Ectotherms "cold" (ambient) blooded.
Figs. 1.3 and 1.4
"set point" 37oC
Humans - 98.6oF = 37oC
Reset thermostat's set point in fever (pyrogens).
Antipyretics (like aspirin) or hibernation lower set point.
Produce heat by shivering or increasing metabolism (with thyroxine, epinephrine)
Decrease heat loss: Arrector pili (smooth muscle) for piloerection (fluffing
fur) , vasoconstriction (closing peripheral capillary beds).
Increase heat loss by panting [for dog] or sweating [for person] or vasodialtion.
Homeostasis: weight regulation
One of my favorite examples of regulation is weight regulation. My fellow
graduate students and their professor in the early 1970's studied the hypothalamus,
a part of the brain you will see in a few minutes, and its involvement in
weight regulation. People actually regulate their food intake well. It is
stated that no calories are lost (in feces or urine) [except that glucose
is lost in urine of people with untreated diabetes]. Thus, you eat the same
amount you need for energy catabolism (2000-3000/day) or else you gain or
lose weight. I checked the calculations and found that 250 extra calories
per day (1 cookie/day) would result in gaining 25 lb/yr (and very few people
are gaining or losing weight that precipitously).
Levels of analysis
Levels of analysis (from introductory biology):
element - molecule - organelle - cell - tissue - organ - organ system -
organism - population - biosphere
Levels of analysis (for this human physiology course):
cell - tissue - organ - organ system - organism
Integrating body functions
To make everything function in cooperation, systems of integration are needed:
(1) hormones (examples of homeostasis, next)
(2) nervous system (first major topic of the semester)
shows these mechanism as well as paracrine (local hormone)
In both cases, a chemical is used.
Neuron uses small amount of neurotransmitter applied directly to target
(muscle, nerve or gland)
Endocrine (ductless) gland (as opposed to exocrine gland with duct) puts
a larger amount of hormone into blood stream where it can affect one or
several target organs.
Homeostasis - hormones
figure from introductory biology)
Here's the bottom middle of the brain, the hypothalamus.
Also, the pituitary to which the hypothalamus connects.
The anterior part of the pituitary puts out ACTH (adreno cortico tropic
["AC" refers to adrenal cortex, "T "refers to trophic
effect, "H" stands for hormone.]
ACTH positively regulates the cortex of the adrenal gland (just north of
The adrenal cortex puts out cortisol that feeds back negatively the anterior
pituitary to decrease ACTH.
The Hypothalamus sends CRF (corticotrophin releasing factor) through the
portal vessel to the anterior pituitary for ACTH release.
[Explanation of "portal" -- Mostly, the circulatory system is
"wired" in "parallel," but for 3 systems, hypothalamus->pituitary,
intestine->liver and kidney cortex->kidney medulla, the blood flows
first to one then to the other, i.e. it is "wired" in "series".]
ACTH feeds back negatively to the hypothalamus to decrease CRF.
[a similar example from your text]
TRH (thyrotropin-releasing hormone) (Note, "hormone" term, "factor"
TSH (thyroid stimulating hormone)
"Thyroxine" has two forms, T3, T4, formed from dimer of tyrosine
(amino acid) with 3 or 4 iodines attached.
What everybody should know about thyroid hormone:
Goiter insufficient dietary iodine
Hyperthyroid syndrome in adult (Graves disease is autoimmyne disease where
antibodies bind receptors for TSH on thyroid gland cells)
Cretinism hypothyroid in infant
Dietary iodine is from sea food. Now iodine is added to salt.
It is because of thyroxine that you should worry if there is a reactor leak
(like 3 mile Island or Chernobyl), and the solution is taking lots of iodine
so that any radioactive iodine you are exposed to will be competitively
swamped out for thyroid uptake.
Roger Guillemin and Andrew V. Schally won the 1977 Nobel
Prize for their discovery of these releasing hormones (factors), a heroc
task because they are present in vanishingly small amounts (because of the
efficiency of hormone delivery through the portal vessel).
(1) see p. 117, G. Audesirk & T. Audesirk, BIOLOGY Life on Earth (3rd
ed.), New York, Macmillan, 1993.
(2) see pp. 48-49, D. J. Aidley, The physiology of excitable cells, Cambridge,
University Press, 1971.
(3) see pp. 34-35, B. Katz, Nerve, muscle and synapse, New York, McGraw-Hill,
(4) S. Freeman, Biological Science, Upper Saddle River, NJ, Prentice-Hall,
Exam questions from 2004 - 2011 relevant to this lecture
Antypyretic. Answer either (1) Why would you take such a drug? or (2)
What is the best known example of such a drug.
to reduce fever, aspirin
Referring to the body's thermostat, under the same circumstances when an
animal might utilize vasoconstriction, what would happen to its fur?
piloerection, fluffing up the fur for better insulation
Guilleman and Schally needed a quarter of a million hypothalami to isolate
TRH. Why did it take so many?
there is not much TRH because of the portal delivery
What happens at the ribosome is called translation. Then why (for what process)
is the Golgi apparatus required?
"A large fraction of the ATP is made in the mitochondrion." What
process makes the ATP that is not made in the mitochondrion?
"A hormone is diluted by the blood stream, and so a lot more chemical
signal is needed than for the a neurotransmitter from the spinal motor neuron
to the muscle cell." Why is a smaller amount of hormone required when
the hypothalamus signals to the anterior pituitary?
the portal system delivers it more discreetly
An equivalent circuit is used as a model that explains exponential functions
of voltage as a function of distance along the axon or voltage as a function
of time when a square wave of current is applied. Name one of the electrical
components used in such an equivalent circuit.
batteries, resistors, capacitors
Before iodized salt, people who lived where would have been more likely
to develop goiter?
inland (away from the ocean)
How would high dietary overdoses of iodine help some people and under what
if exposed to radioactive iodine from a reactor leak, normal iodine would
compete for incorporation into thyroxine
How come there is heat available to allow you to regulate your body temperature
at 98.6 o F?
catabolism is only about 40 % effective in useful work, the "waste"
is heat that can be used
"The nucleus orchestrates the cell's functions by [doing what?] at
the level of the ribosomes?
(via mRNA) translation of proteins
What would vasoconstriction do to help to regulate body temperature?
decrease heat loss
4. Used as an example of homeostasis, thyroxine was shown to have what effect
on the anterior pituitary?
"inhibits responsiveness to TRH" translates to: feeds back to
decrease release of TSH
An equivalent circuit for the membrane, shown in the first lecture, plotted
an exponential decrement of voltage as a function of distance. Name one
of the electrical components that was shown in that model.
resistor, capacitor, battery
Using an expression that relates to constructive metabolic reactions and
the chemical nature of the compounds, what are the testosterone-like drugs
that some athletes abuse?
It's winter and it is cold outside, and your home heating system serves
as a model of homeostasis. A furnace provides heat, "feedback"
in the homeostasis model. Temperature is monitored by a thermometer. What
is the other critical component in this model of homeostasis?
the set-point on the thermostat, a comparator
Why are the various types of insensible water loss (recall that dogs and
humans were used as examples) so effective and critical in temperature regulation?
sweating or panting
Near the kidney is an endocrine gland that surrounds the adrenal medulla.
Answer one of the following: (1) What is the name (abbreviation will suffice)
of the pituitary peptide that regulates a major hormone (cortisol) from
this gland? (2) What kind of chemical is this gland's hormone (cortisol)?
"Hormones are not very efficient because they get diluted by the entire
volume of the blood stream." Why are releasing hormones (releasing
factors) from the hypothalamus different?
They travel by the portal system directly to the pituitary
Hypertrophy of the thyroid gland Answer one of the following: (1) results
from insufficiency of what dietary substance? (2) results from insufficiency
of what hormone? (3) is called (what)? (4) is referred to as endemic (why)?
iodine, thyroxine (T3 or T4), goiter, happened inland, not in coastal areas
Under what circumstances does a person lose calories via the urine?
What is an anabolic steroid?
a hormone like testosterone that bromotes muscle growth
Why might you take iodine supplements if you are downwind of a reactor accident?
have more "cold" iodine to compete with radioactive iodine for
T3 and T4 incorporation
"Tropic," the "T" in "ACTH" means affecting
the activity of. Specifically, on what gland does ACTH have this trophic
affect? (i.e. What does the AC stand for?)
What does piloerection do to regulate back to the set point?
fluffing the fur prevents heat loss
Name a substance for which the portal vessel from the hypothalamus to the
pituitary is specifically "designed."
TRH, others like it
What does panting achieve for a dog?
ACTH triggers the release of what hormone from its target gland?
Relate the statement "Aspirin is an antipyretic" to the concept
pyrogens reset the thermostat to cause fever
"Insensible" is a term applied to water loss by perspiration or
panting in contrast with the water loss by micturition. What does "insensible"
you're not aware of it
Relate the amount of energy an average adult uses per day in catabolic metabolism
to the energy needed to increase the temperature of 1 ml of water by 1 degree
2000 k cal / day relative to the definition of one calorie
What is the set point for the human hypothalamic thermostat in degrees C?
Why are sweating and panting so effective for increasing heat loss?
the heat of vaporization is 540 cal
Why is the term "anabolic" applied to steroids abused by some
they cause build-up as oppoaed to break-down (in catabolism), in this case
of muscle mass
How does aspirin affect the set point of the thermostat?
it is antipyretic
What would be specified with the term "catabolism" in distinction
with the more general term "metabolism?"
How does vasoconstriction decrease heat loss?
Less radiation of warmth from extremeties
Why is testosterone referred to as an "anabolic steroid?"
it favors muscle growth
If there were a deficiency of iodine in the diet, which pituitary hormone
would be produced in excess, leading to goiter?
ACTH has a negative feedback to control what hypothalamic hormone in order
to regulate its own (ACTH's) level?
Why is it especially useful for a person to sweat when hot?
Evaporative heat loss
In terms of the human thermostat, when would shivering be a useful behavior?
Muscle activity generates heat
"You do not lose calories through your feces and urine." What
is the most notable exception to this generalization?
Untreated diabetes mellitus
Why don't most people gain or lose a lot of weight rapidly?
homeostasis - they eat the right amount
State one of the physiological mechanisms for decreasing heat loss in mammals.
Why are some steroids are called "anabolic?"
they favor growth
"Neurotransmitters are strategic because they are so discrete and thus
use a minimum amount." Why on earth would there be hormones then?
they reach many areas
How does glucose get into the cell?
transport, facilitated and co-transport with sodium
What hormone does the adrenal release in response to ACTH?
There is a lot less TRH than TSH. Why?
TRH delivered neatly via portal system
How is paracrine signaling distinguished from endocrine signaling?
paracrine is local
Why is panting and perspiring so effective to increase heat loss?
because of the large heat of vaporization of water
A fat is a triglyceride. How come membrane lipids have only two fatty acids
in text book diagrams? (i.e. What is the third item linked to the glycerol?)
the polar head group
"Endemic" was the term your text used for (what?) disorder of
inland people who had no seafood (in the old days)?
The lay expression for ectotherm is "cold-blooded." Why is that
More like they assume ambient temperature
How come homeotherms (endotherms) always have heat available for maintaining
body temperature at the set point?
Because of inefficiency in metabolism, waste is heat
In addition to triiodothyroxine, what is the other thyroid hormone?
In your homeostasis lecture, ACTH was used as an example. What keeps ACTH
levels from getting real high?
homeostasis (negative feedback from cortisol)
Adrenalin comes from the adrenal medulla. By contrast, where does ACTH exert
its trophic effect?
What is the opposite of vasodilation and what is this (the opposite of vasodilation)
useful for (in terms of homeostasis)?
vasoconstriction would decrease heat loss (body's thermostat)
A diagram from the introductory biology book showed how hypothalamic CRF
(corticotropin releasing factor) caused the anterior pituitary to secrete
ACTH (adrenocorticotropic hormone). Why is this hormone referred to as CRF?
corticotropin = ACTH, factor=hormone, causes its release
Guillemin and Schally won a Nobel Prize for for their discovery of releasing
hormones (factors), a heroic task because they are present in vanishingly
small amounts. Why can there be such small amounts of these hormones (compared
with other hormones).
portal vessel delivers it without dilution
A nuclear reactor spews out radioactivity upwind of where you live. Quick!
What should you eat to minimize thyroid damage?
nonradioactive iodine to compete with the radioactive for uptake
Relate "goose bumps" with temperature regulation in a mammal that
piloerection would fluff up the fur to conserve heat, goose bumps just show
the smooth muscle poking up the "vestigial" hairs
The drugs that some athletes abuse are sometimes called anabolic steroids.
What does the word "anabolic" imply?
anabolic (vs catabolic) is the branch of metabolism for constructive reactions
A model for the exponential decrement of voltage along the length of the
axon was shown in the first lecture. I said "along the length of the
axoplasm, there is resistanceäout in the extracellular space there
is resistance but not much." Why isnt there much?
Because there is not a confined space
"The action potential depolarizes the axon ahead of it to the threshold
(for the action potential, and how far this spreads is described by an exponential
drop-off." What does myelin do to this distance?
The drugs that some athletes abuse are sometimes called anabolic steroids.
What does the word "anabolic" imply?
Anabolic refers to build-up
"The adrenal is two glands; The adrenal medulla releases adrenaline."
The other part: Answer either (1) what is it called? Or (2) what does it
1 adrenal cortex 2 cortisol (and others)
Regarding the regulation of blood flow to your periphery, for instance your
hands, how would this contribute to temperature regulation?
Radiate more heat if vasodilation
Goiter. Answer either (1) This is caused by too MUCH of what hormone? Or
(2) Why is there too much of this hormone?
1 TSH 2 insufficient T3 & T4 -> insufficient negative feedback
What is different about the circulatory system of the hypothalamus - anterior
pituitary than most other parts of the body?
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