Introductory lecture

Reading assignment: Chapter 1 and other material specifically referenced

What is life?

Fig. 3.1
(Also TRANSPARENCY 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 list:

#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 and Medicine

#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.
Endotherms (homeotherms).

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)

Fig. 6.29
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

TRANSPARENCY (review 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 hormone).
["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 kidney).
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.

Fig. 11.16
[a similar example from your text]
TRH (thyrotropin-releasing hormone) (Note, "hormone" term, "factor" above.)
TSH (thyroid stimulating hormone)

Fig. 11.3
"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:

Fig. 11.25
Goiter insufficient dietary iodine

Fig. 11.24

Figure 11.26
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, 1966
(4) S. Freeman, Biological Science, Upper Saddle River, NJ, Prentice-Hall, 2002

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?

post-translational modifications

"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 circumstances?

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?

anabolic steroids

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)?

ACTH, steroid

"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?

untreated diabetes

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?)

adrenal cortex

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?

evaporative cooling

ACTH triggers the release of what hormone from its target gland?


Relate the statement "Aspirin is an antipyretic" to the concept of homeostasis.

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" mean?

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 C.

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 athletes?

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.

piloerection, vasoconstriction

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 inaccurate?

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?

adrenal cortex

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 has fur.

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?
Increases it
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 release?
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?
Portal system

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