OSU Physio 6101 - Lecture 1 Introduction (Fu)

This is a comprehensive review of lecture 1.

What is physiology?

It is the study of how living organisms function, of how the body works. From Greek meaning “study of nature”.

What is the hierarchical organization of the body?

Cells → tissues → organs → organ systems.

What is a cell?

The simplest structural unit into which a complex multicellular organism can be divided and still retain the function characteristic of life.

What are tissues?

Aggregates of differentiated cells with similar properties.

What is an organ?

Different tissue types joined in a structural unit to serve a common function.

What is an organ system?

Organs that are linked together to serve an overall function.

What are the 11 organ systems?

Circulatory, digestive, endocrine, immune, integumentary, respiratory, reproductive, urinary, nervous, musculoskeletal, and lymph.

What are the 4 categories of cells/tissues?

Muscle, nerve, epithelial, and connective.

What is the function of muscle cell/tissue?

Generate mechanical force.

What are the 3 types of muscle cell/tissue?

Cardiac, skeletal and smooth.

What is nerve cell/tissue specialized to do?

Initiate, integrate, and conduct electrical signals to other cells.

What is epithelial cell/tissue specialized to do?

Selective secretion and absorption of ions and molecules, and protection.

What is connective cell/tissue specialized to do?

Connect, anchor, and support the structures of the body (e.g. Blood, Cartilage, Adipose). If it is not muscle, nerve, or epithelial, it is connective.

How are epithelial cells named accordingly to their shape?

Cuboidal (cube-shaped), columnar (elongated), squamous (flattened), and ciliated.

What are the two divisions of epithelial tissue?

Simple epithelium, single-cell thick tissue; stratified epithelium, consisting of numerous cell layers.

Where are epithelia located?

At the surface of the body or individual organs; at inner surfaces of the tubular and hollow structures within the body.

What do epithelial cells rest on?

An extracellular protein layer called the basement membrane.

What do tight junctions enable epithelia to do?

Form boundaries between body compartments and function as selective barriers regulating the exchange of molecules.

What surrounds individual cells?

Extracellular matrix (ECM) and extracellular fluid (ECF).

What is the ECM?

A mixture of structural proteins (e.g. collagen), adhesive proteins (e.g. fibronectin and laminin), and protein-polysaccharides complexes (e.g. proteoglycans).

What are the functions of ECM?

Scaffold for cellular attachments; transmission of information to help cells regulate their activity.

What two compartments that compose ECF?

The plasma (fluid phase of the blood) and the interstitial fluid (ISF), surrounding cells within tissues.

What is ICF?

The fluid located inside the cells.

What separates ICF from ECF?

Cell membranes.

Is there more ICF or ECF?

There is more ICF. Around 2/3 of the fluid is ICF and around 1/3 is ECF.

What separates ISF and plasma?

Capillary wall.

What is total body water (TBW) as a percentage of body weight?

60% body weight.

What is ICF as a percentage of body weight?

40% body weight.

What is ECF as a percentage of body weight?

20% body weight.

What is interstitial fluid as a percentage of body weight?

16% body weight.

What is plasma as a percentage of body weight?

4% body weight.

What percentage of ECF is inside the cardiovascular system?

20%.

What percentage of ECF is located between the cells?

80%.

What is the concept of homeostasis?

Most of the common physiological variables of the body are maintained within a predictable range. This is commonly referred to as maintenance of homeostasis.

What did Claude Bernard talk about?

“un milieu interieur”, a well-regulated internal environment.

Who coined the term homeostasis?

Walter Cannon.

What did Walter Cannon mean by homeostasis?

The relative constancy of the internal environment.

What statement appears in The Wisdom of the Body (1932)?

“Change is met with mechanisms that restore constancy.”

What are examples of physiological variables or vital parameters?

Blood pressure; body temperature; blood glucose and oxygen levels; intracellular levels of ions.

What happens to glucose levels after eating?

Glucose levels increase after eating, then return to their set point.

What is dynamic constancy?

Levels change over short periods of time, but remain relatively constant over long periods of time. This is demonstrated by the glucose example.

What is the essence of physiology according to the slides?

The regulation of vital parameters by homeostatic mechanisms.

What happens when there is a change that can challenge maintenance of a vital parameter?

The body initiates reactions to correct or minimize that change.

When does regulation of vital parameters occur?

In the face of constant stress or challenges.

Why is homeostatic regulation described as a dynamic process?

It involves constant change that evokes a physiological response to return the vital parameter to “normal”.

When does pathophysiology occur?

When the physiological control mechanisms can no longer control a vital parameter within normal limits.

In simple terms, what is pathophysiology when physiological control mechanisms can no longer control a vital parameter within normal limits?

Disease.

What type of mechanisms are homeostatic processes to regulate vital parameters?

Negative Feedback mechanisms.

What is the regulated variable?

What is being controlled (e.g. body temperature).

What is the set point?

The normal or ideal value; steady state (e.g. 37C)

What is sensory input?

Mechanism that sense the actual value of the regulated variable (e.g. sensing temperature using thermoreceptors).

What is the integrative center?

Where the actual value and the set point are compared. If a difference is detected, effector systems are activated that change the regulated variable in the direction back toward the set point (e.g. the hypothalamus).

What is an effector?

Mechanism that return the regulated variable toward the set point. (e.g. blood vessels, voluntary muscles, and muscle activity - constrict, curling up, and shivering respectively).

Why is body temperature regulation a physiological example of negative feedback?

The body continuously senses core temperature, compares it with a set point, and activates effectors to bring body temperature back toward the set point.

What is a reflex?

A specific involuntary, unpremeditated, unlearned “built-in” response to a particular stimulus.

What is the pathway mediating a reflex called?

The reflex arc.

What are the components of a reflex arc?

Stimulus, receptor, afferent pathway, efferent pathway, and effector.

What is a stimulus in a reflex arc?

A detectable change in the internal or external environment.

What is a receptor in a reflex arc?

The component which detects the change.

What does the afferent pathway do?

Transmit information regarding the stimulus to an integrating center.

What does the efferent pathway do?

Transmit the information from the integrating center to the effector.

What is the effector in a reflex arc?

Effector activation produces the outcomes of the Response.

What do endocrine cells secrete?

Hormones into the blood.

What is a hormone?

A type of chemical messenger secreted into the blood by cells of the endocrine system.

What do nerve cells release?

Neurotransmitters.

Where do neurotransmitters act?

At specialized junctions with target cells (e.g. muscle cells, gland cells or other neurons).

What is a paracrine agent?

A signal that reaches neighboring cells via diffusion within the ISF.

What is an autocrine agent?

A signal that affects the cell that synthesized the signal.

Can an agent have both paracrine and autocrine functions?

Yes.

What is a biological rhythm?

A rhythmical change in a body function (e.g. circadian rhythm).

What do biological rhythms add to homeostatic control systems?

An anticipatory component.

When are biological rhythms activated?

Immediately and automatically at times when a challenge is likely to occur.

How do biological-rhythm responses differ from negative-feedback homeostatic responses?

Biological rhythms are anticipatory; negative-feedback homeostatic responses are corrective responses initiated after the steady state has been perturbed.

What is adaptation?

An inherited biological control mechanism.

What is acclimation?

Occurs when control mechanisms change in response to prolonged exposure to a stimulus or stress.