This web page contains notes to accompany lectures in Vertebrate Physiology, Biology 410, taught by Dr. Peter King in the Department of Biology, Francis Marion University, Florence, South Carolina, 29502, USA.

Physiology is the study of how organisms work. In this course we will focus on the physiology of vertebrates. Having a common evolutionary history many of the mechanisms that control how vertebrates work are similar. Much of our knowledge of human physiology has come from studying related vertebrates.
Physiology integrates information from many other areas of science including chemistry and physics. Physiology also encompasses the knowledge from branches of biology. One underlying theme of biology is that there is a often function is dependent on form or structure. The physiology of an organism is the result of adaptation to its environment. What we see in the mechanisms of body systems is the result of evolution over many millions of years.

Homeostasis
Homeostasis is the maintenance of stable conditions within the internal environment of an organism. A lot of our energy goes into maintaining physiological acceptable limits. If our body is low in water we get thirsty and seek water for example. If out temperature increases we sweat to produce conditions of evaporative cooling. Physiological systems generally have built in control mechanisms that rely on negative feedback. Much of this course will look at how the steady state is maintained in various systems.

Movement of molecules across membranes
Cells contol their internal environment by controlling synthesis and degradation and by controlling movement of molecules across the cell membrane.

What makes molecules move?
Molecules (solutes) that are dissolved in a solution will move by diffusion from an area of high concentration to an area of low concentration. Movement will continue until a state of equilibrium has been reached.

Cell membranes are semi permeable membranes or perhaps better described as selectively permeable.

Small uncharged particles such as oxygen O₂ and Carbon dioxide CO₂ can move through a cell membrane by diffusion if a concentration gradient exists. Water molecules can also move across a cell membrane by a similar process but it is given a special name osmosis.

Cross membrane proteins can creat holes or channels in a cell membrane and allow diffusion of other molecules to take place. These proteins, called carrier proteins, are generally selective in the molecules they will allow to move and hence the concept of selective permeability. This is called facilitated diffusion. If a mechanism is available to open and close the channel we now have control over what enters and exits the cell provided concentration gradients exist.

Some cross membrane proteins are able to move molecules across a membrane against a concentration gradient. This requires energy (ATP) and is called active transport. These proteins are also referred to as carrier proteins or pumps i.e. Na/K pump transports Na⁺ and K⁺ across a membrane

Another mechanism for moving materials out of a cell is exocytosis. A membrane bound vessicle may fuse with a cell membrane and expell the vessicle contents on the outside of a cell. A reverse process endocytosis can take materials into a cell by forming an invagination of the cell membrane that breaks off inside the cell.

Enzymes
Enzymes are biological catalysts.
They increase the rate of chemical reactions by 10⁶ to 10¹² times.
They work under physiological conditions.
They may be very specific.
Their activity is easily modified.
Almost all enzymes are proteins.

Enzyme activity is effected by 3 important characteristics.
1. Temperature
2. pH
3. concentration

Enzymes control most biochemical reactions within organisms. They allow metabolic pathways to function. They also provide oportunities for negative feedback loops to operate in very complex pathways with simple mechanisms that disable enzyme activity.

Cells are dynamic
Cells are constantly reacting to their environment. Their environment is the internal environment of out body or the interstitial fluid that surrounds the cells. We will be looking at what stimulates a cell to perform its function. What environmental cues signal the cell to change? Hormones and neurotransmitters are 2 common signals but there are many others. Homeostasis is important because it provides some consistancy in the normal environment.

Metabolism

Why does an animal (like you) need oxygen?

It is necessary for aerobic respiration.

What is aerobic respiration?
The breakdown of fuels to produce ATP, using oxygen as the final electron acceptor of the electron transfer chain in mitochondria.
Does glycolysis use oxygen?
No
Glycolysis is a precursor to the Krebs cycle forming pyruvate CH₃COCO₂

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This page was created by Peter King. Please contact the author at pking@fmarion.edu with comments.
http://people.fmarion.edu/pking/vertphys/intro.html
Last edit January 10, 2011.
Copyright Peter King