BMSC 207 Midterm
Homeostasis - ✔️✔️The ability to maintain a relatively stable internal environment
despite exposure to external variability. Along with regulation of the internal environment
it is a key focus of physiology. Originally termed by Walter Cannon and means like of
similar condition. Conditions in each person vary slightly.
Homeostasis and Disease - ✔️✔️There can be an external change such as toxic
chemicals, physical trauma, foreign invaders or internal changes such as abnormal cell
growth, autoimmune disorders, genetic disorders that lead the body to attempt to
compensate which will either lead to health or a pathophysiological state.
Physiology - ✔️✔️The study of the normal functioning of a living organism and its
component parts, including all its chemical and physical processes. Aristotle said it was
the knowledge of nature. Hippocrates said it was the healing power of nature.
Integrative Science - ✔️✔️Physiology is this. It covers chemistry, molecular biology,
cell biology, and ecology. It is closely tied to anatomy because the structure will provide
a physical base for the function.
Cells - ✔️✔️Smallest unit of structure capable of carrying out life processes.
Tissue - ✔️✔️Collection of cells carrying out related functions.
Organ - ✔️✔️Formation of tissues into a structural and functional unit.
Organ System - ✔️✔️Integrated groups of organs.
Body Systems - ✔️✔️It is often common to study each system individually but there is
actually a lot of integration between the organ systems. Some variables are controlled
by many systems.
Teleological Approach - ✔️✔️The function or "why"
Ex. Why do red blood cells transport oxygen? Because cells need oxygen and the
RBC's bring it.
Mechanistic Approach - ✔️✔️The mechanism or "how"
Ex. How do RBC's transport oxygen? Oxygen bind to hemoglobin in the red blood cells.
This is much more the focus of physiologists.
10 Organ Systems - ✔️✔️1- Musculoskeletal-skeletal, muscles, bone
2- Integumentary-skin
,3- Digestive- stomach, intestines, liver, pancreas
4- Circulatory- heart, blood vessels, blood
5- Respiratory-Lungs, airway
6- Immune- Thymus, spleen, lymph nodes
7- Endocrine- Thyroid gland, adrenal gland
8- Nervous-Brain, spinal cord
9- Urinary- Kidneys, bladder
10- Reproductive- Ovaries, uterus, and testes.
Pathophysiology - ✔️✔️Abnormal physiology
Extracellular Fluid - ✔️✔️Considered as the internal environment of the body.
Surrounding cells it is a buffer between cells and the external environment. Composed
of the plasma and interstitial fluid.
Dynamic Steady State - ✔️✔️the internal environment is in a relatively steady state but
is dynamic in that materials are constantly moving back and forth between the
extracellular and intracellular fluid.
Law of Mass Balance - ✔️✔️If the amount of a substance in the body is to remain
constant, any gain must be offset by an equal loss.
Input: diet-food, water Lungs, Skin, Metabolic production
Output: Pee, feces, lungs, skin, metabolism
The body load is what is typically in the body.
Homeostasis and equilibrium - ✔️✔️These concepts are NOT equal. The ECF and ICF
must have different concentrations for basic survival. When studying this it is much
easier to study the plasma rather than the individual cells. The ultimate goal is to
maintain the dynamic steady states of body compartments.
Control Systems - ✔️✔️To maintain homeostasis the body monitors certain key
functions/variables. The variables are kept in a normal range by these control
mechanisms. They can be local (one area) or reflex (through out the body).
Input signal(variable sensed)-Integrating centre(takes in info and decides)-Output
signal(try to fix)-Response(action is taken).
Local Control - ✔️✔️Restricted to tissues or cells involved. Ex. Active cells reduce the
amount of oxygen in the tissue so endothelial cells send local signals which causes
vasodialation and oxygen levels are restored.
Reflex Control - ✔️✔️Long distance signaling- changes are widespread throughout the
body (systemic) use more complex control systems. Any mechanism of this type with
use either the endocrine system or the nervous system. The response loop causes
, movement in the downward direction while the feedback loop modulates the response
loop and feeds back to ultimately influence the input.
3 types- negative, positive, and feed forward.
The acceptable set point range is variable depending on the parameter and can be
either narrow or slightly broader. Ex. The fish tank.
Reflex control can be antagonistic using two different systems. Think of the heating and
cooling of a house.
Negative feedback loop - ✔️✔️a pathway in which the response opposes or removes
the stimulus signal. It serves to stabilize a system, homeostatic, can restore the initial
state but cannot prevent the initial disturbance.
Ex. Blood glucose and blood glucoagon.
Positive Feedback Loop - ✔️✔️A more rare type, are not homeostatic, reinforce a
stimulus to drive the system away from a normal value rather than decreasing or
removing it. An intervention outside of the loop will stop the response.
Ex. Oxytocin in birth.
Feedforward Control - ✔️✔️a few reflexes have evolved that allow the body to predict a
change is about to occur.
Ex. Salivation, stomach acid, digestive contractions
Ex. Heart rate increases before exercise
biological rhythms - ✔️✔️Set points change over time due to genetics, constant
exposure, or a new condition.
It is a variable that changes predictably to create repeating patterns or cycles of
changes.
Circadian rhythm is a cycle over 24 hours that corresponds to light and dark. Hormones
are linked to these cycles as well.
Membranes - ✔️✔️Separate one compartment from another.
Cell Membrane - ✔️✔️Originally thought to have consisted of one layer of lipids but it is
known now that it is actually a double layer of phospholipids with protein molecules.
Carbohydrates attach on the outside as well. The average composition is about 55%
proteins, 45% lipids, and very small levels of carbohydrates however depending on the
cell this changes. The more proteins are present the more active the cell likely will be.
Functions of a Cell membrane - ✔️✔️1. Physical isolation: separates ICF and ECF,
separates cell from environment.
2. Regulation of exchange with the environment: entry, elimination and release
3. Communication between the cell and its environment: contains proteins that allow for
responding or interacting with external environment.
4. Structural support: Proteins in the membrane are used to make cell-to-cell
connections and to anchor cytoskeleton.
