CHAPTER 40 INTRODUCTION TO ANIMAL FORM AND FUNCTION Prepared by Brenda Leady, University of Toledo Copyright (c) The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

All animal cells share similarities in the ways in which they Exchange materials with their surroundings Obtain energy from organic nutrients Synthesize complex molecules Duplicate themselves Detect and respond to signals in their immediate environment

Tissues Specialized cells of a given types cluster together 4 categories Muscle Nervous Epithelial Connective

Muscle tissue Cells specialized to contract 3 types Skeletal – attached to bone or exoskeleton for locomotion, voluntary control Smooth – surrounds hollow tubes and cavities for propulsion of contents, involuntary control Cardiac – only in the heart, involuntary control

Nervous tissue Initiate and conduct electrical signals from one part of the animal’s body to another Electrical signals produced in one nerve cell may stimulate or inhibit other nerve cells to Initiate new electrical signals Stimulate muscle to contract Stimulate glands to release chemicals

Epithelial tissues Sheets of densely packed cells that Cover the body or individual organs Line the walls of body cavities Specialized to protect and secrete or absorb Rest on basal lamina or basement membrane Can function as selective barriers

Connective tissues Connect, anchor, and support Includes blood, adipose, bone, cartilage, loose and dense connective tissue Form an extracellular matrix around cells Provides scaffold for attachment Protects and cushions Mechanical strength Transmit information

Creature Feature

Organs Composed of 2 or more kinds of tissues Organ system – different organs work together to perform an overall function Organ systems frequently work together – nervous and endocrine system Spatial arrangement of organs into organ systems part of overall body plan Body plan controlled by highly conserved family of genes with homologs in all animals

Organ Development and Function Are Controlled by Homeotic Genes Homeotic genes – family of ancient highly conserved genes found in all animals Determine timing and spatial patterning of the anteroposterior body axis during development In vertebrates known as Hox genes Important role in determining where organs form Hox genes also important for growth, development and function of organs in adults

Body fluids 2 main compartments Intracellular fluid – inside cells Extracellular fluid – outside cells Plasma – fluid portion of blood Interstitial fluid – fluid between cells Separate in closed systems Hemolymph intermingles to fluids in many inverts Intracellular and extracellular fluid can be very different in solute composition

Movement of water Plasma membranes tend to be highly permeable to water and Fluid moves readily between compartments Osmosis Swollen or shrunken cells do not operate well Can happen when cells exposed to more dilute (hypoosmotic) or more concentrated (hyperosmotic) extracellular fluids

Movement of solutes Passive diffusion Transport proteins used in Movement of a solute down its concentration gradient No carrier or ATP required Only lipid soluble molecules Transport proteins used in Facilitated diffusion – passive Active transport

Fick diffusion equation: Movement of solutes What variables influence the rate of diffusion? Fick diffusion equation: J = KA (C1 - C2)

Structure and function Key theme is structure determines function Compare respiratory systems of insect and mammal Structural similarities suggest similar function Tubes connect with the outside environment terminating in 1 cell thick structures Tubes serve as air conduits Thin cells with high surface area for diffusion of gases

Increased space requirements avoided by shape changes All organs that mediate diffusion or absorption have an extensive surface area Increased space requirements avoided by shape changes Folding for example SA/V – surface area to volume ratio

Surface area to volume ratio In groups of 3 discuss and come up with 3 specific examples of species/organs we studied that have important roles of increasing surface area

Homeo-stasis Process of adjusting to the external environment and maintaining a stable internal environment Conformers – maintain same fluid composition as environment – cheaper Regulators – internal composition of fluids different from environment – more expensive Animal can be both with respect to different variables

No physiological function is constant for very long, which is why we call them “variables” Normally, blood sugar (glucose) remains at fairly steady and predictable levels in any healthy individual After a meal the level of glucose in your blood can increase quickly If you skip a meal, your blood sugar level may drop slightly Homeostatic mechanisms restore blood glucose to normal levels in the blood

Homeostatic control systems Sensor – monitors particular variable Integrator – compares signals from the sensor to a baseline set point Effector – compensates for deviations between actual value and set point Example – body temperature in mammals

Feedback Fundamental feature of homeostasis Major way disturbances are minimized Negative feedback Positive feedback

Feedback Discuss with your neighbor a variable in the human body, the sensor, integrator and effector in the feedback system

Negative feedback Variable being regulated brings about responses that move the variable in the opposite direction Decrease in body temperature leads to responses that increase body temperature May occur at organ, cellular or molecular level

Positive feedback Far less common Accelerates a process Reinforces the direction of the change Birth in mammals

Feedforward regulation Animal’s body begins preparing for a change in some variable before it occurs Anticipatory Speeds up homeostatic responses and minimizes deviations from the set point Many result from or are modified by learning

Pavlov Demonstrated the Relationship Between Learning and Feedforward Processes Demonstrated that feedforward processes associated with digestion could be conditioned to an irrelevant stimulus Used ticking metronome (not ringing bell) Conditioned stimulus by itself can elicit increased salivation Other sounds and stimuli also worked Conditioned response not permanent

Local homeostatic responses Some homeostatic responses may be highly localized Paracrine signaling – molecules released into interstitial fluid to act on nearby cells Neurotransmitters released from one nerve cell travel to an adjacent nerve cell In contrast, hormones are chemical messengers produced in a gland, secreted into the blood, and act on distant cells