Chapter 1

The Study of Body Function

Human Physiology

Human Physiology•Study of how the human body functions.

•Pathophysiology: ▫How physiological processes are altered in disease or injury.

Scientific Method•Confidence in rational ability, honesty and humility.

•Formulate hypothesis.•Testing the hypothesis.•Analyze results.•Draw conclusion.

Homeostasis•Maintaining constancy of internal environment.

•Dynamic consistency.•Maintained by negative feedback loops.

Feedback Loops•Sensor:

▫Detects deviation from set point.•Integrating center:

▫Determines the response.•Effector:

▫Produces the response.

Negative Feedback• Defending the set

point.• Reverse the

deviation.• Produces change in

opposite direction.

Hormone insulin restores plasma [glucose].

Positive Feedback

•Action of effectors amplifies the change.

•Is in same direction as change.•Examples:

▫Oxytocin (parturition)▫Voltage gated Na+ channels (depolarization)

Primary Tissues

•4 Different Primary Tissues:▫Muscle▫Nervous▫Epithelial▫Connective

Muscle Tissue

•Specialized for contraction.•3 Types of Muscle Tissue:

▫Skeletal▫Cardiac▫Smooth

Skeletal Muscle

• Voluntary muscle.• Striated.• Attach to bones at

both ends (tendons).

• Arranged in parallel.

• Grade contraction.

Cardiac Muscle

•Striated.•Found only in

the heart.•Interconnecte

d.•Intercalated

discs.•Syncytium.

Smooth Muscle

•Not striated.•Gap

junctions.•Calmodulin.•Peristalsis.•Syncytium.

Nervous Tissue•Neurons (nerve cells):

▫Specialized for conduction of action potentials.

•Supporting cells:▫Provide anatomical and functional support.

Neuron•Dendrites:

▫Receive input. •Cell body:

▫Nucleus. ▫Metabolic center.

•Axon:▫Conducts nerve

impulses.

Epithelial Tissue

•Types of Epithelial Tissue:▫Cells that form membranes:

Squamous Columnar Cuboidal

▫Exocrine glands▫Endocrine glands

Squamous Cells

•Flattened in shape.

•Adapted for diffusion and filtration.

•Line all blood vessels.

Cuboidal Cells•Cube-shaped

cells.•Excretion,

secretion and absorption.

•Line kidney tubules, salivary ducts, and pancreatic ducts.

Columnar Cells•Taller column

shaped cells.•Excretion,

secretion and absorption.

•May contain cilia.•Line digestive

tract and respiratory passageways.

Exocrine Glands

•Derived from cells of epithelial membranes.

•Secretions are released through ducts.•Simple tubes or modified as acini.•Examples:

▫Tear glands▫Sweat glands▫Prostate glands

Endocrine Glands•Lack ducts.•Secrete hormones into capillaries within the body.

•May be discrete organs:▫Primary functions are the production and secretion of hormones.

Connective Tissue•Large amounts of extracellular (ECF)

material in the spaces between connective tissue cells.

•4 Types of Connective Tissue:▫Connective tissue proper▫Cartilage▫Bone▫Blood

Connective Tissue Proper•Loose connective tissue:

▫Scattered collagen and tissue fluid. Dermis of skin

•Dense fibrous connective tissue:▫Regular arranged.

Collagen oriented in same direction. Tendons

▫Irregularly arranged. Resists forces applied in many directions.

Capsules and sheaths

Cartilage

•Chondrocytes.•Supportive and protective tissue.

•Elastic properties to tissues.•Precursor to many bones.•Articular surfaces on joints.

Bone

•Hydroxyapatite crystals•Osteoblasts:

▫Bone-forming cells•Osteocytes:

▫Trapped osteoblasts: less active•Osteoclasts:

▫Bone resorbing cells

Blood•Classified as connective tissue.•Half its volume is plasma.

Organs

•Organs:▫Composed of at least two primary tissues.

▫Serve different functions of the organ.

Systems

•Organs that are located in different regions of the body and perform related functions.

•Examples:▫Skeletal system▫Cardiovascular system▫GI system

Body-Fluid Compartments•65-75% of total body weight H20.•Intracellular compartment:

▫Fluid inside the cell.▫2/3 of H20

•Extracellular compartment:▫1/3 H20▫2 Subdivisions:

Blood plasma Interstitial fluid

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