Chapter 29 PHYSIOLOGY HOMEOSTASIS AND TEMPERATURE REGULATION PHYSIOLOGY

Chapter 29 PHYSIOLOGY, HOMEOSTASIS, AND TEMPERATURE REGULATION

PHYSIOLOGY: INTERNAL FLUIDITY � Animals are mostly water � Intracellular Fluid (ICF) � Most of water � Within cells � Extracellular � The Fluid (ECF) rest of the water, interstitial fluid, plasma, lymph � Interstitial fluid: Bathes cells, nutrients, waste

PHYSIOLOGY: HOMOESTASIS � Homeostasis � Maintaining stable internal environment � Temperature, p. H, ion concentration

PHYSIOLOGY: TISSUES � Cells → Tissues → Organs � Specialized cells form tissues � Tissue types � Epithelial � Connective � Nervous � Muscle

PHYSIOLOGY: EPITHELIAL TISSUE � Epithelial cells � Lines body surfaces and organs � Functions � Secretion, selective absorption, protection, transcellular transport and detection of sensation

PHYSIOLOGY: CONNECTIVE TISSUE � Components: Cells, fibers, extracellular matrix � Functions � Store energy, protect organs, provide structural framework, connect tissues � Tissue composition differs based on function

PHYSIOLOGY: NERVOUS TISSUE � Composed of two cell types � Neurons � Conduct nerve impulses throughout body � Components of central and peripheral nervous systems � Communicate by chemical neurotransmitters � Glial � Provide support for function

PHYSIOLOGY: MUSCLE TISSUE � Function: produce force and create motion � Contractile filaments move across � Changes size of cell → Motion � Three types � Skeletal: Locomotion and movement � Cardiac: Heartbeat � Smooth: Forces in internal organs

PHYSIOLOGY: ORGANS � Cells → Tissues→ Organs � Most organs have all four tissue types � Homeostasis depends on organs responding to the demands of the cells

PHYSIOLOGICAL REGULATION ACHIEVES HOMEOSTASIS � Information is required to regulate internal environment. � Information=Feedback � Systems are controlled by actions of nervous and endocrine systems

FEEDBACK INFORMATION � Set point � Desired � Error � Any level or rate signal difference between the set point and the feedback information

REGULATORY SYSTEM � Anything that receives information processes it and issues commands � Sensor-provides feedback information; eyes, nose, touch, hairs, etc. � Effectors-systems that make the changes

NEGATIVE FEEDBACK � Most commonly used by regulatory systems � “Negative”- used to counteract a force pushing away from the set point, the change is “negated” � Ex: Sweating from your body temperature being to high cools you down.

POSITIVE FEEDBACK � Not as commonly used as negative feedback � Amplifies a response � Increases � Sexual the deviation from the set point behavior- a little stimulation causes an increased behavioral response

FEEDFORWARD INFORMATION � Information used to change a set point � Ex: Squirrels know when cold temperatures are coming, and use this information to change the regulations and hybernate

LIVING CELLS ARE TEMPERATURE SENSITIVE � Normal cellular function=0 -40 degrees C � Most cells adapted to narrow limit � Humans- 35 -40 Degrees C

TEMPERATURE SENSITIVITY � Most reactions are temperature sensitive � Usually proceed faster at a higher temperature Q 10 = RT/RT– 10 Q 10 –temperature sensitivity coefficient RT –rate of reaction at a certain temperature Also known as “the 10 degree rule”

ACCLIMATION TO SEASONAL TEMPERATURES � Produce fewer enzymes � Produce enzymes with different optimal temp

REGULATION OF BODY TEMPERATURE � Ectotherms � “heat from the outside” � Use heat from the environment � Invertebrates, Fish, Amphibian, Reptiles

REGULATION OF BODY TEMPERATURE � Endotherms � “heat from inside” � Maintain a higher body temperature � Heat generated metabolically � Birds and Mammals

TEMPERATURE REGULATION � Heat budget equation � Heatin: Thermal energy flowing in � Environment � Heatout: � If and metabolism Thermal energy leaving animal heatin ≠ heatout, then body temperature will change � Surface area and temperature are key factors

THERMAL ENERGY GAIN/LOSS � Metabolism � Cleaving bonds in ATP � Radiation � Infrared radiation � Convection � Conduction � Evaporation

TEMPERATURE REGULATION � Endotherms spend more energy pumping ions across membranes and maintaining concentration gradients � Expenditure of energy releases heat

TEMPERATURE REGULATION � If temperature falls below endotherms lower critical temperature, then their body temperature will fall � Heat produced by � Shivering thermogenesis � Nonshivering heat production in brown fat

TEMPERATURE REGULATION � Basal metabolic rate (BMR) � � Body size and environmental temperature Increases as animals get smaller

TEMPERATURE REGULATION � Cold-climate species � Lower surface area/volume ratio � Insulation with fur � Decrease blood flow to skin � Countercurrent heat exchange � Rounder body shapes have lower ratio

TEMPERATURE REGULATION � Fish lose most heat as blood travels through gills � Cold fish use cold blood from gills � Hot fish use countercurrent exchage

TEMPERATURE REGULATION � High environmental temperature � Increased blood flow to skin � Evaporation of water through sweating � Active process

TEMPERATURE REGULATION � Ectotherms � Insects can produce heat contract flight muscles

TEMPERATURE REGULATION � Endotherms and ectotherms both regulate temperature behaviorally

TEMPERATURE REGULATION � Hormonal and neural mechanisms control thermoregulatory adaptations � Temperature regulatory system acts as thermostat � Hypothalamus is the center of thermostat

TEMPERATURE REGULATION � Cool hypothalamus � Increased metabolic rate � Less blood flow to skin � Warm hypothalamus � More blood flow to skin � Sweating and panting � Negative feedback

TEMPERATURE REGULATION � Fever response to pathogens � Animals lower temperature during inactive periods- torpor � Energy conservation � Hibernation � Long lasting regulated hypothermia