2Homeostasis and Control Systems Homeostasis – an equilibrium (steady state) between an organism’s various physiological functions, and between the organism and the environment.This is a balance in response to continually changing conditions in both the internal and external environments
3Steady State achieved by self adjustment (see feedback) death results when then balance can no longer be maintaineddynamic equilibrium – a condition that remains stable with fluctuation limitsThere are many factors that we, as organisms, must balance: ex. blood glucose, water content (osmotic balance), temperature, hormones, etc.
4Control Systems All homeostatic control systems have three components: a monitor special sensors located in the organs of the body detect changes in homeostasisa coordinating centre, receives message from sensors and relays information to appropriate regulator (organ/tissue that will act to restore steady state) braina regulator restores normal balance muscles and organs
5FEEDBACK SYSTEMS MAINTAIN HOMEOSTASIS Components: 1. Receptors 2. Control Center3. EffectorsNEED TO KNOW THIS!!!Have receptors all over our body in every tissue; collect data constantly5
6Coordination of Body Functions The activity of various specialized parts of an animal are coordinated by the two major systems of internal communication:the nervous system – involved with high-speed messagesthe endocrine system – involved in the production, release, and movement of chemical messangers
7All animals exhibit some coordination by chemical signals: hormones = produced by the endocrine system convey information between organs of the bodypheromones = chemical signals used to communicate between different individualsneurotransmitters = chemical signals between cells on a localized scale (over short distances; between neurons)
8The Endocrine System Has several key components: Hormones = secreted by endocrine or neurosecretory cells, travel into body fluids to target cells where it elicits a specific responseTarget Cell = cell equipped to respond to the given hormoneNeurosecretory cells = neuron that receives signals from other nerve cells and responds by releasing hormones into body fluids or into a storage organ from which they are later released.Endocrine gland = ductless gland that secretes hormones into the body fluids for distribution through the bodyNote: Exocrine gland = glands that produce a variety of substances (e.g sweat, mucus, digestive enzymes) and deliver their produces via ducts, are NOT part of the endocrine system.More on the endocrine system in chapter 8…..
9Excreting Waste Urinary System Formation of Urine Water Balance Kidney DiseaseExample: carbon dioxide levels Levels increased during exerciseChemical receptors in brain are stimulatedNerve cells from the brain carry impulses to muscles that increase breathing rate.A group of arteries in the neck can detect low levels of oxygen in the blood and they send a message via a nerve to the brain, which then relays the message to the muscles that control breathing movements.Because we are constantly having to fix our levels so they stay within a range, we call it dynamic equilibrium.Mechanisms that make adjustments to bring the body back within its acceptable range are called negative feedback systems.
10The body is self correcting by the use of negative feedback Most homeostatic control systems are negative feedback systems. These systems prevent small changes from becoming too large.A relationship in which the response is opposite to the stimulus (or impressed change)The body is self correcting by the use of negative feedbackExample: glucose and insulin, thermostat (pg. 336)high glucose in blood↑ insulin production
11Response No heat produced Heater turned off Room temperature decreases SetpointToohotSet pointSetpointToocoldControl center:thermostatStudy this on your ownRoomtemperatureincreasesHeaterturnedonResponseHeatproduced11
12NEGATIVE FEEDBACK ►decreases an action ►stops when return to normal ►most homeostatic control mechanisms are negative feedback12
13Positive Feedback systems: process by which a small effect is amplified A relationship in which the response is the same as the stimulusLeads to instability and possibly deathSome rare limited examples:birthing process in humans: childbirth hormone oxytocin
14►must be turned off by outside event POSITIVEFEEDBACK(reinforces)►increasesan action►must be turned off by outside event►decreases►could run away = death* blood loss- ↓ B.P.- ↓ heart beat* blood clotting14
15Decrease in progesterone ---->increase in uterine contraction ----> release of oxytocin ---> increase in stronger contractions---->baby is expelled----->contraction stop--->release of oxytocin stops↓ progesteronecontractions & oxytocin+Section 7.1 Questions, pp. 337, #1-5
16ThermoregulationThermoregulation: the maintenance of body temperature within a range that enables cells to function efficiently.Ectotherms: (reptiles etc.) rely on air temperature to regulate metabolic rates. Therefore activity is dependent on environment. adaptations: seeking sun, shadeEndotherms: (mammals etc.) maintain constant body temp (37°C) regardless of environment. Respond to changes in environmental temp. by using energy to produce heatConduction: direct transfer of thermal motion(heat) between molecules of the environment and those of the body surfaceConvection: transfer of heat by the movement of air or liquid past the surface of a bodyRadiation: the emission of electromagnetic waves produced by all objects warmer than absolute zero transfer heat between objects that are not in direct contactEvaporation: the loss of heat from the surface of a liquid that is losing some of its molecules as gasEndotherms generally consume much more food than ectotherms of equivalent size.
17Relationship between body temperature & Environmental temperature 40River otter (endotherm)30Body temperature (°C)20Largemouth bass (ectotherm)1010203040Ambient (environmental) temperature (°C)17
18B. Modes of Heat Exchange Organisms exchange heat by four physical processes: conduction, convection, radiation, and evaporationRadiation: radiate heatbetween objects not in contact.Evaporation: removal heatfrom surface of liquid lostas gasConvection: transferheat by mvt airConduction: direct transferheat between moleculesin contact18
19B. Balancing Heat Loss and Gain In thermoregulation, physiological and behavioral adjustments balance heat loss and heat gain5 general adaptations in animals’ thermoregulation:InsulationCirculatory adaptationsCooling by evaporative heat lossBehavioral responsesAdjusting metabolic heat production19
201. InsulationInsulation is a major thermoregulatory adaptation in mammals and birdsIt reduces heat flow between an animal and its environmentExamples are skin, feathers, fur, and blubberIn mammals, the integumentary system acts as insulating materialThis is how we regulate our heat20
212. Circulatory Adaptations Many endotherms & some ectotherms alter amount of blood flowing between the body core & skinVasodilatation = ↑ blood flow in skin = ↑ heat lossVasoconstriction = ↓ blood flow in skin =↓ heat lossLike when we work out and our faces get red; our blood is flowing faster and our vessels are expanding to let off more heat.21
22important for reducing heat loss Many marine mammals & birds have arrangement blood vessels called counter current heat exchanger which areimportant for reducing heat loss22
233. Cooling by Evaporative Heat Loss Many types of animals lose heat through evaporation of water in sweatPanting augments the cooling effect in birds and many mammalsBathing moistens the skin, helping to cool animal23
244. Behavioral ResponsesBoth endotherms and ectotherms use behavioral responses to control body tempSome terrestrial invertebrates have postures that minimize or maximize absorb solar heatMore extreme behavioral adaptations = hibernation or migration to more suitable climateLike when we shiver and tense our muscles when we are cold.24
255. Adjusting Metabolic Heat Production Some animals can regulate body temperature by adjusting their rate of metabolic heat productionMany species of flying insects use shivering to warm up before taking flightPreflight warmup in hawkmoth = shiver-like to help muscles produce enough power to take off25
26C. Feedback Mechanisms in Thermoregulation Mammals regulate body temperature by negative feedback involving several organ systemsIn humans, the hypothalamus (a part of the brain) contains nerve cells that function as a thermostat26
27Physiological Response Adjustment Decreased environmental temperature StimulusPhysiological ResponseAdjustmentDecreased environmental temperatureConstriction of blood vessels in skin-hairs on body erect shiveringHeat is conserved more heat is generated by increased metabolismIncreased environmental temperatureDilation of blood vessels of skin-sweatingHeat is dissipatedVasodilation/Vasoconstriction/ Counter-current heat exchange
30increase sweat (glands) vasodilatation (blood vessels) Responses to heat stress: (nerve messages from sensor via hypothalamus)increase sweat (glands)vasodilatation (blood vessels)Responses to cold stress: (nervemessages from sensor via hypothalamus)smooth muscles contractvasoconstriction (blood vessels)hair stands on end to trap warm air near skin (follicles) (goosebump = musclecontraction in area of hair follicle)rhythmic skeletal musclecontraction = shivering to generate heatMammalian Diving ReflexSection 7.2 Questions, pp. 341, # 1-7Torpor: alternative physiological state in which metabolism decreases and the heart and respiratory system slow down conserve energy when food supplies are low and environmental temperatures are extremeHibernation: long-term torpor during which the body temp. is lowered as an adaptation to winter cold and food scarcityEstivation: summer torpor slow metabolism and inactivity that enables an animal to survive long periods of high temps. And scarce water supplies