Levels of Structural Organization Cells are the smallest unit of organization that can live independently. Cells are organized into tissues. Tissues are organized into organs. Organs are organized into systems.
Tissue—group of cells with a common structure and function 4 main types: 1) epithelial—outside of body, linings of organs and cavities. Free surface is exposed to air or fluid; other side is attached to the basement membrane, a dense mat of extracellular matrix.
Types of epithelial cells simple—single layer stratified—multiple layers cuboidal—cube shape columnar—sideways stacked bricks squamous—flat
2. Connective tissue—binds and supports other tissues—3 types of fibers a.collagenous fibers—nonelastic fiber (skin does not come off on pulling)
b. elastic fibers—made of elastin (guess what—they’re elastic! Skin pulls back; blood vessels) c. reticular fibers—thin, branched, made of collagen, join connective tissue to adjacent tissues (around muscle fibers)
Types of connective tissues—all have an extensive extracellular matrix a) Loose connective tissue binds epithelial cells to other tissues, holds organs in place; ex. fibroblasts (secrete proteins), macrophages (engulf bacteria and dead cells) b) Adipose tissue stores fat, insulates body c) Fibrous connective tissue is made of dense collagenous fibers; ex. tendons (attach muscles to bones), ligaments (join bones together) d) Cartilage is used for flexible support e) Bone is a mineralized connective tissue—osteoblasts deposit collagen, Ca ++, Mg +, PO 4 - that harden f) Blood has a matrix of plasma
3. Nervous tissue—senses stimuli and transmits signals—functional unit is the neuron (nerve cell) 4. Muscle tissue—made of long muscle fiber cells that can contract Skeletal—voluntary movements Cardiac—heart muscle Smooth—involuntary movements
Tissues are arranged into organs— many organs live in cavities filled with fluid: --lungs and heart are in thoracic cavity --stomach is in abdominal cavity diaphragm (muscle) separates these 2 cavities Systems consist of several organs
Your systems are connected!!
Bioenergetics—how we make energy from what we eat—is it efficient? Amount of energy an animal uses/unit time = metabolic rate Energy is measured in calories or kilocalories
Use of chemical energy generates heat. Minimum metabolic rates maintain life maximum rates occur during peak activity BMR= basal metabolic rate—for an endotherm (that’s us!) at rest, empty stomach, no stress SMR= standard metabolic rate—for ectotherms—have to know temperature
Homeostasis—”steady state”—animals want to keep a constant condition in internal environments (ex. humans—temp, blood pH, blood sugar) Cells of vertebrates live in interstitial fluid
Parts of a homeostatic control system: Receptor—detects a change in internal environment Control Center—processes information and directs and appropriate response Effector—effects the changes mandated by the control center
Negative feedback is a common control mechanism