Unformatted text preview:

29. HomeostasisA. Homeostasisa. Maintenance of a relatively constant internal environment even when the external environment changes significantlyB. Requirementsa. Sensori. Detect the stimulus: fluctuations in the variable above or below the set pointb. Control center for responsei. Upon receiving a signal from the sensor, it generates output that triggers a responsec. Responsei. Physiological activity that helps return the variable to the set pointd. Signaling Mechanismse. Negative Feedbacki. Control mechanism that reduces the stimulusii. Ex: exercise1. When your exercise vigorously, you produce heat, which increases body temperature2. Nervous system detects this increase and triggers sweating3. As you sweat, the evaporation of moisture from your skin cools your body, helping return your body temperature to it’s set pointf. only works within a range of parametersi. moderates but doesn’t eliminate changes in the internal environmentC. Acclimatizationa. One way in which the normal range of homeostasis may changeb. Gradual process by which an animal adjusts to changes in its external environmentc. Not adaptationd. Example: when a mammal moves up into the mountains from sea leveli. Physiological changes occur facilitate activity at higher elevationsii. Lower oxygen concentration in the air= breathe more rapidly and deeplyiii. Loses more co2 through exhalation, raising blood ph above its set pointiv. Changes in kidney function result in excretion of more alkaline urine, returning blood ph to its normal rangeD. Homeostasis and temperature controla. Normal body temperature 37 C (98.6 F) ---i. body temp rises above normal ---ii. nervous system signals dermal blood vessels to dilate and sweat glands to secrete --iii. body heat is lost to its surroundings --iv. body temperature drops toward normal --v. normal body temperatureb. Hypothalamic set point -i. Body temperature drops below normal -ii. Nervous system signals dermal blood vessels to constrict and sweat glands to remain inactive--1. Body heat is conserved 2. Body temperature rises toward normal 3. Hypothalamic set pointiii. If body temperature continues to drop, nervous system signals muscles to contract involuntarily-1. Muscle activity generates body heat 2. Body temperature rises toward normal 3. Hypothalamic set point Fig 30.230. Physiological EcologyA. Adaptations: conserved solutions from ancestorsa. Not all adaptations are new adaptationsb. Conserved mechanisms more widespread that appreciated because we instinctively look for differencesc. Easiest and most likely to have one solution emerge and all offspring have a derivative of themd. “if it ain’t broke..don’t fix it”B. Convergent Evolutiona. Independent evolution of similar phenotypes from different sourcesb. Constrained by evolutionary historyc. Genetic variation for a potential adaptation never occurred or not right place/timed. Convergence doesn’t have to occure. Evolution does not have a single, optimal solution to any problemC. How to stay in life parametersa. Live in consistent environmentsb. Move with environmental changec. Behaviors that improve conditionsd. Homeostasise. Plasticityf. SymbiosisD. Phenotypic Plasticitya. The ability of individual genotypes to produce different phenotypes when exposed to different environmental conditionsb. Respond to environmental conditionsc. Not non-genetic or all environmentald. Exists in animals, plants varying degreesi. Whole body or separate structures of bodye. Plasticity is itself heritablef. Plantsi. allocation of more resources to the roots in soils that contain low concentrations of nutrients and the alteration of leaf size and thicknessg. Animalsi. Responses to temperature are essential among ectodermic organismsii. Phenotypic plasticity of the digestive system allows some animals to respond to changes in dietary nutrient composition, diet quality, and energy requirements1. Ex: Changes in the nutrient composition of the diet (the proportion of lipids, proteins and carbohydrates) may occur during development (e.g. weaning) or with seasonal changes in the abundance of different food types.E. Plasticitya. Facilitated by (but does not require) modular growth patterning and fractal growth patterningb. Allows for relatively few instructions (genes) to fill space and fit needs. More genes and more instructions would constrainF. Sex & Plasticitya. Many but not all reptiles determine offspring sex b temperature of incubationb. Climate change means= same genotype, very different phenotype31. Skeletons & Mechanics of SupportA. Skeletal Functionsa. Resist, absorb, and transmit mechanical forcesi. Support- maintain shape in the face of external forcesii. Protection- prevent external forces from damaging organismiii. Motility- transfer forces from one region of an organism to another or to the external environmentb. Skeletons are dynamici. Interact with muscles- skeletomuscular systemii. Can be modifiediii. May have pliant or fluid componentsc. 3 typesi. Antagonistic musclesii. Extensor: extend body partiii. Flexor: bend body partd. Hydrostatic skeletoni. found in soft-bodied invertebrates such as earth worms and jelly fishe. Exoskeletoni. surround the body as a rigid hard casef. Endoskeletoni. vertebrates and echinodermsii. rigid internal skeletons to which muscles are attachediii. Vertebrates have a flexible exterior that accommodates the movements of their skeletoniv. composed of cartilage or boneB. Mechanical Forcesa. Skeletal system is subject to a variety of applied forces as bone is loaded in various directionsb. Loads are produced by weight bearing, gravity, muscular forces, external forcesc. Aligned forces—act along a single axisi. Failure perpendicular to loadii. Compression: load that pushes molecules of a structure closer together1. Compression force presses the ends of the bones together and is produced by muscles, weight bearing, gravity or some external loading along the length of the bone2. Compressive stress and strain inside the bone shorten and widen the bone3. The bone absorbs maximal stress on a plane perpendicular to the compressive load4. Compressive forces are necessary for development and growth in the boneiii. Tension: load that pulls molecules of a structure farther apart1. Applied to the bony surface and pulls or stretches the bone apart so that it tends to lengthen and narrow2. Maximum stress is perpendicular to the plane of the applied load3.


View Full Document

UMD BSCI 207 - Homeostasis

Documents in this Course
Notes

Notes

15 pages

Neurons

Neurons

27 pages

Exam 3

Exam 3

5 pages

Motility

Motility

19 pages

Final

Final

20 pages

Exam 3

Exam 3

4 pages

EXAM 2

EXAM 2

12 pages

DNA

DNA

11 pages

Load more
Download Homeostasis
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Homeostasis and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Homeostasis 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?