PHYSIOLOGY 214:
Lecture notes: Week 1
Intro to physiology: (Lecture 1)
What is Physiology?
• The study of the function of living things – how the human body works.
• Physiology focuses on mechanisms of action – Cause and effect sequences of physical
and chemical processes in the body.
• Two approaches are used to explain events that occur in the body:
- Emphasizes the purpose of a body process.
- Emphasizes the underlying mechanism.
Why vs How in Physiology:
o Physiological Processes (What):
Shivering in response to cold
o Why?
Because shivering generates heat which warms the body
o How?
Temperature sensitive nerve cells detect a decrease in body temperature – signal a
region in the brain responsible for temp sensitivity – activates a nerve pathway that
causes involuntary, oscillating waves of muscle contraction (shivering)
Structure and Function:
▪ Structure and function are inseparable.
▪ The structures of the body (Anatomy) are closely related to the function of the body
(Physiology)
▪ Example: Air sacs in the lungs contain thin walls closely associated with blood
vessels for diffusion of gases between the lungs and the blood
Levels of Organization in the Body:
There is exquisite structural organisation of the human body, from the most
microscopic (chemical) to the body as a whole (organism)
1. Chemical Level
2. Cellular Level
3. Tissue Level
4. Organ Level
5. Organ System Level
6. Organism Level
, 1. Chemical Level:
❖ The chemical level: Various atoms and molecules make up the body.
Atoms: smallest building blocks of matter
Molecules: atoms combine to make larger molecules
2. Cellular Level:
➢ Cells are the basic units of life.
➢ A cell is the smallest unit capable of carrying out the basic processes
associated with life.
➢ Enclosed by a plasma membrane.
➢ Interior composition is regulated – contains atoms and molecules used,
produced, and maintained for life functions.
Basic cell functions:
1) Obtaining food (nutrients) and O2
2) Performing chemical reactions
3) Eliminating CO2 and other waste
4) Synthesizing proteins
5) Controlling the exchange of materials in and out
6) Moving materials internally from one part of the cell to another
7) Sense and respond to environment.
8) Reproduce.
Specialized Cell Functions:
✓ In multicellular organisms, each cell also performs a specialized function.
✓ Each cell performs these specialized activities in addition to carrying on the basic cell
functions.
, ✓ Example: digestive glands use protein synthesis machinery within cells to produce
digestive enzymes - specialized proteins that break down food (Function: Protein
Synthesis)
✓ Example: Kidney tubules regulate substances between the blood on one side of the
cell and urine on the other side of the cell to selectively retain necessary substances in
the blood and remove wastes.(Function: controls exchange)
3. Tissue level:
- Tissues are groups of cells of similar
specialization.
- There are four primary types:
Muscle, Nervous, Epithelial,
Connective
- Each tissue consists of cells of a single
specialized type.
Muscle tissue:
• Muscle tissue consists of cells specialized
for contracting, which generates tension
and produces movement.
• The three types of muscle tissue include:
1) Skeletal muscle, which moves the
skeleton.
2) Cardiac muscle, which pumps blood out of the heart.
3) Smooth muscle, which controls
movement of contents through
hollow tubes and organs, such as
movement of food through the
digestive tract.
Nervous tissue:
o Nervous tissue consists of cells specialized
for initiating and transmitting electrical impulses.
o These electrical impulses act as signals that relay information from one part of the
body to another.
o Nervous tissue is found in the brain, spinal cord, nerves, and special sense organs.
Epithelial tissue:
▪ Epithelial tissue consists of cells specialized for exchanging materials between the
cell and its environment.
▪ Epithelial tissue is organized into two general types of structures:
1) Epithelial sheets
2) Secretory glands.
▪ Epithelial sheets are layers of tightly joined cells that cover and line various parts of
the body.
, - Only selective transfer of materials is possible between regions separated by an
epithelial barrier.
▪ Glands are epithelial tissue derivatives specialized for
secreting.
▪ Secretion is the release from a cell, in response to
appropriate stimulation, of specific products that have been
produced by the cell.
▪ Glands are formed by pockets of epithelial tissue that dip
inward from the surface and develop secretory capabilities.
▪ The two categories of glands are:
- Exocrine
- Endocrine
Connective tissue:
Connective tissue is distinguished by having relatively few
cells dispersed within an abundance of extracellular
material.
As its name implies, connective tissue connects, supports,
and anchors various body parts.
The cells within connective tissue produce specific
structural molecules that they release into the extracellular
spaces between the cells.
4. The organ level:
❖ An organ is a unit made up of several tissue types.
❖ Organs consist of two or more types of primary tissue organized to perform
functions.
❖ Example: The stomach - is made up of all four primary tissue types.
❖ The stomach is lined with epithelial tissue - Epithelial gland cells in the
stomach include exocrine cells and endocrine cells.
❖ The stomach wall contains smooth muscle tissue.
❖ The stomach wall also contains nervous tissue.
❖ Connective tissue binds together all these various tissues.
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