Overview of Physiology & Homeostasis 1 Biological explanations Levels of organization Homeostasis
2 Biological Explanations Proximate Proximate causation: an explanation of an animal's behavior based on it s response to a particular stimulus and the internal mechanisms responsible for the behavior. Ultimate Ultimate causation: an explanation of an animal's behavior based on evolutionary pressures possible explanation of why a particular behavior was favored by natural selection.
3 Levels of Organization Molecules Cells Tissues Muscular Nervous Epithelial Connective
Muscle tissues consist of elongated cells that generate force and cause movement. Three types of muscle tissues: Skeletal Cardiac Smooth Skeletal Muscle cells Skeletal: responsible for locomotion and other body movements (e.g., breathing, shivering). Cardiac: makes up the heart and is responsible for the heartbeat and blood flow. Smooth: involved in movement and generation of forces in internal organs (e.g., gut, blood vessels). Cardiac www.uoguelph.ca/.../devobio/210labs/muscle1.html Smooth
Nervous tissues contain two basic cell types: neurons and glia. Neurons encode information as electrical impulses that travel along axons to their targets. Chemical signals from the neuron stimulate a response in the target cell, via receptors. Glia provide support, nutrients and protection for neurons.
Epithelial tissues are sheets of tightly connected epithelial cells. This tissue forms structures such as the skin and lines hollow organs. Some epithelial cells: Secrete substances, like sweat or hormones Move substances with cilia Possess chemical receptors Create boundaries Control filtration and transport
Connective tissue provides support (and often a blood supply) for other tissues. Also binds other tissues together to form organs. 7 Cells dispersed in an extracellular matrix, which may be Solid Gel-like Liquid
Connective tissues are dispersed cells in an extracellular matrix that they secrete. The matrix contains protein fibers: Collagen: strong and resistant to stretch, supports skin and connections between muscles and bones Elastin: can be stretched and then recoils; found in tissues that stretch (e.g., lungs, arteries) www.technion.ac.il/~mdcourse/274203/lect3.html
Specialized Connective tissues: Cartilage provides structural support and is flexible: has chondrocytes; cells that secrete the extracellular matrix. No blood supply within cartilage. Bone: provides support and is hardened by calcium phosphate deposition in the matrix. Cells are found in lacunae within the matrix and are interconnected by tiny channels. Highly vascularized. cellbio.utmb.edu/.../compact_bone_histology.htm
Specialized connective tissues: Adipose tissue: White adipose tissue forms a store for lipids. Brown adipose tissue generates heat. Blood: consists of cells in a very liquid extracellular matrix, the blood plasma. www.technion.ac.il/~mdcourse/274203/lect3.html
11 Levels of Organization Molecules Cells Tissues Muscular Nervous Epithelial Connective Organs
Organs consist of multiple tissues. Example: The stomach wall is arranged in layers: Smooth muscle
Levels of Organization 13 Molecules Cells Tissues Muscular Nervous Epithelial Connective Organs Organ systems
An organ system is a group of organs that function together, e.g. the digestive system 14 Fig 15-15
Levels of Organization 15 Molecules Cells Tissues Muscular Nervous Epithelial Connective Organs Organ systems Organism Fig 1-1
Organ Systems 16 Control Support & Movement Maintenance Reproduction
All systems are interconnected and work together 17
18 Limits on body size r = 1 r = 2 r = 3 Surface area 4 r 2 Volume 4/3 r 3 SA:V
19 Limits on body size r = 1 r = 2 r = 3 Surface area 4 r 2 Volume 4/3 r 3 SA:V 12.6 50.2 113.1 4.2 33.5 113.1 3.0 1.5 1.0
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Milieu intérieur 21 "The living body, though it has need of the surrounding environment, is nevertheless relatively independent of it. Claude Bernard (1813-1878)
Internal environment contains: ~ 90% water in most animals dissolved inorganic & organic electrolytes, e.g. Na +, K +,Cl -, amino acids, proteins, nucleic acids dissolved non-electrolytes, i.e. urea, glucose non-dissolved solids e.g. lipid membranes, cytoskeleton, cellular inclusions (glycogen, lipid) 22 O 2, nutrients CO 2, wastes
Extracellular environment: between cells in multicellular organism 23 Provides an additional interface with the external environment O 2, nutrients CO 2, wastes O 2, nutrients CO 2, wastes
Milieu intérieur 24 "The living body, though it has need of the surrounding environment, is nevertheless relatively independent of it. Claude Bernard This independence which the organism has of its external environment, derives from the fact that in the living being, the tissues are in fact withdrawn from direct external influences and are protected by a veritable internal environment which is constituted, in particular, by the fluids circulating in the body."
25 Intracellular Fluid ICF ICF ICF ICF ICF
26 Extracellular Fluid (ECF) Plasma Interstitial Fluid (ISF)
Body weight 27 Total body water ICF + ECF ISF + plasma
Homeostasis 28 tendency of organisms to maintain a relatively constant internal environment despite variable external conditions. Walter B. Cannon (1871-1945) http://www.library.upenn.edu/etext/smith/c/cannon1.html Fig 1-2
Some variables that may be maintained relatively constant 29 temperature [O2] [CO2] ECF volume and pressure [nutrients] [waste products] [water] [salts] ph sterility
Negative-feedback-control system 30 Requires: Continuous sampling of the controlled variable - sensor. Comparison of sample with a given set point. Immediate corrective action (control mechanisms) in opposite direction to perceived error signal negative feedback. Fig 1-3
Spotlight 1-1 31
32 Characteristic of a regulated system in which the system s response opposes the original change in the system.g. An increase in body temperature of an endotherm causes physiological responses that serve to reduce body temperature: sweating flushing as warm blood is moved to skin decreased movement decreased metabolic rate
Regulation of Blood Glucose Levels 33
Positive feedback 34 Characteristic of a regulated system in which the system s response amplifies the original change in the system Few examples in biological systems: e.g. urination defecation sneezing vomiting nerve action potential ovulation child-birth
Positive Feedback 35 Ends with an explosive event
Child-birth occurs due to a positive feedback loop 36
How do animals respond to their external environment? 37 Fig 1-4
The Lizard is a conformer and the Mouse is a regulator: 38
Thermal classification of animals can be based on source of heat. Ectotherms have external sources of heat. Endotherms regulate temperature by producing heat metabolically or by actively losing heat. Heterotherms show characteristics of both an ectotherm and an endotherm. 39 Major differences between ectotherms and endotherms: Resting metabolic rate Total energy expenditure when at rest Response to changes in environmental temperatures An endotherm will increase its metabolic rate to maintain its body temperature in cold conditions.
40 (Spiny anteater) Fig 17-12
Both endotherms and ectotherms may use behavioral regulation to maintain body temperature. 41