BIOL 1108 1st Edition Exam 3 Study Guide Lectures 12 14 Lecture 12 October 6 Homeostasis and Thermoregulation Learning Objectives 1 Practice observing animal FORM and relating it to FUNCTION 2 Be able to de ne homeostasis 3 Be able to draw a generalized homeostatic feedback diagram and understand its terminology 4 Understand two evolutionary strategies animals have for thermoregulation 5 Consider organisms physiological morphological and behavioral adaptations for thermoreg ulating within their environments In The News Why did John O Keefe May Britt Moser and Edvard I Moser update their Facebook pages last week These scientists won the 2014 Nobel Prize in Physiology or Medicine for discovering how the brain stores information through the inner GPS navigation of brain cells This discovery can ultimately help nd a cure for brain diseases such as Alzheimer s o Discovery of brain cells that give the body a sense of self location o Sense of space spatial arrangement in mice was measured using electrodes in their brains o Neuron ring was relative to direction of where the mice were facing and spatial cues o Representation of these signals are found in the entorhinal cortex and hippocampus NEGATIVE FEEDBACK TOPHAT QUESTION How would you de ne a negative feedback loop A A process whereby a change in an initial condition triggers a response that counteracts the initial change The receptor receives information that something in the environment is changing The control center or integration center receives and processes information from the receptor The effector responds to the commands of the control center by either opposing or enhancing the stimulus This is an ongoing process that continually works to restore and maintain homeostasis HOMEOSTASIS The property of a system in which variables are regulated so that internal conditions remain stable and relatively constant Homeostatic regulation involves three parts or mechanisms 1 The receptor 2 The control center 3 The effector For example in regulating body temperature there are temperature receptors in the skin which communicate information to the brain which is the control center and the effector is our blood vessels and sweat glands in our skin Because the internal and external environment of the body are constantly changing and adjustments must be made continuously to stay at or near the set point homeostasis can be thought of as a synthetic equilibrium THERMOREGULATION Heat gain and loss Radiation The emission of electromagnetic waves by all objects warmer than absolute zero Can transfer heat between objects that are not in direct contact as when a lizard absorbs heat radiating from the sun Evaporation The removal of heat from the surface of a liquid that is losing some of its molecules as gas For example evaporation of water from a lizard s moist surfaces that are exposed to the environment had a strong cooling effect Convection The transfer of heat by the movement of air or liquid past a surface as when a breeze contributes to heat loss from a lizard s dry skin or blood moves from the body core to the extremities Conduction The direct transfer of thermal motion heat between molecules of objects in direct contact with each other as when a lizard sits a hot rock Heat gain loss and environmental interaction relative to organisms physiological morphological and behavioral adaptations ABIOTIC AND BIOTIC FACTORS Abiotic Factors o Temperature hooter near the equator colder near the poles o Land vs Water cool down faster in water than air o Elevation cooler in higher areas and in low areas o Sunlight vs Shade warmer in the sunlight o Vegetation o Water Biotic Factors o Ectotherms heat source from something external Ex Lizard o Endotherms internal metabolistic heat source regulates own heat Ex Walrus Lecture 13 October 10 Electrical Signals Learning Objectives 1 Describe the range of vertebrate nervous systems 2 3 4 5 Describe information processing Identify neuron structure and function Describe the basis of membrane potential Be able to describe what an action potential is including depolarization hyperpolarization 6 Describe how an electrical signal moves down an axon from one neuron to the next 7 Apply what you ve learned to real world situations In The News In what ways does our understanding of giraffes not measure up Maternal Behavior mourning over died offspring social groups like elephants Male Behavior show sexual features depending on the presence of other males Fighting necking sexual selection evolution Circulatory system thick blood vessels to avoid fainting Ecological impacts seed distributers Physiology testosterone androgen fluctuates based on sexual activity o Body temperature averages around 38 degrees endothermic TOPHAT Which has more vertebrae a giraffe or a mouse They are the same all animals have 7 vertebrae ANATOMY OF NEURON The functional unit of the nervous system is the neuron 1 Dendrites receives the signals 2 Cell body contains organelles 3 Axon Hillock signals are generated 4 Myelin sheath Schwan Cell insulation and increase speed 5 Node of Ranvier gap helps signals leap down the axon 6 Axon transmits signal from cell to cell 7 Axon Terminal connects cell to dendrites of another cell MEMBRANE POTENTIAL The charged difference or voltage mV between the inside and outside of the axon Two factors that influences membrane potential is ion concentration diffusion and electrical force The negative charge inside the axon is built up through active transport o Resting potential when no signals are being sent at all is between 60 mV and 80 mV Why is the axon resting membrane potential 70 mV There are more potassium channels than there are sodium channels So potassium is going to leave the cell and sodium is going into the cell The net movement of potassium out of cell positive charges leave cell negative net loss Sodium in the outside also is positive and remains on the outside creating a positive gradient Number of sodium and potassium attempt to balance through diffusion More diffusion out than in the cell Using ATP as energy to transport sodium out and the potassium in the cell TOPHAT At which phase does depolarization rst occur At graded potential TOPHAT An action potential is triggered when the membrane potential reaches 55 mV EQUILIBRIUM POTENTIAL Eion When the electrical gradient opposes the concentration gradient Calculated using the Nernst Equation o Eion 62 mV log ion concentration outside ion concentration