1. Physiology, Homeostasis and Temperature Regulation
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Bio 11, Week 9
Purves et al., Chapter 41

2. Outline Tissues, organs, organ systems
4 types of tissues
Organs consist of multiple tissue types
Organ systems are groups of organs that function together
Physiologic regulation & Homeostasis
Ectotherms and Endotherms
Thermoregulation
Feedback loops

3. Tissues, Organs, Organ Systems
Cells organized into tissues
Tissues are organized into organs
Organs are organized into organ systems

4. 4 Types of Tissues
When cells with the same characteristics or specializations are grouped together, they form a type of tissue
Epithelial
Connective
Muscle
Nervous

5. Epithelial Tissue Covers the body and lines organs
Sheets of densely packed, tightly connected cells that cover surfaces
Comprise the skin and line hollow organs (gut)
Some epithelial cells are secretory (hormones, mucus, sweat, digestive enzymes)

6. Epithelial Tissue cont.
Some epithelial cells have cilia to transport substances over surfaces or through tubes
Some epithelial cells have protective functions (create boundaries bt inside and outside)
Epithelial cells can also form receptors to provide information to the nervous system (smell and taste receptors)

7. Epithelial Tissue cont.
Have distinct inner and outer surfaces
Inner surfaces = basal ends of the epithelial cells (rests on basal lamina)
Outer surfaces = apical ends of the epithelial cells

8. Epithalial Tissue cont.

9. Connective Tissue Support and reinforce other tissues
Dispersed populations of cells embedded in an extracellular matrix comprised of proteins
Collagen (25% total body protein)
Elastin (wrinkles with aging)

10. Connective Tissue cont.
Cartilage provides rigid, structural support
Collagen fibers embedded in flexible matrix
Bone provides rigid, structural support
Collagen fibers hardened by calcium phosphate
Adipose Tissue
Stored energy
Blood

11. Connective Tissue cont.

12. Muscle Tissue Contract and cause movement Elongated cells
Most abundant tissue type
When active (contracting) use most of the energy produced by the body
Silverthorn, Human Physiology, 3rd edition Figure 12-1,2

13. Nervous Tissue Process information
Neurons communicate via electrical and chemical signals
Glial cells support neurons (outnumber them too)

14. Organs Consist of multiple tissue types Ex. Wall of stomach
Inner surface lined with epithelial cells that secreted mucus and digestive enzymes
Connective tissue underneath epithelial lining
Muscle tissue (smooth) allows stomach to contract
Neurons control contractions and secretions

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16. Organ Systems
Controlled and regulated to achieve constancy in the internal environment of the organism.
Nervous
Endocrine
Muscles
Skeletal
Reproductive
Digestive
Respiratory
Circulatory
Lymphatic
Immune
Skin
Excretory

17. The endocrine system of humans
Pineal gland
Hypothalamus
Posterior pituitary
Anterior pituitary
Thyroid
Parathyroid
Thymus
Heart
Liver
Stomach and small intestine
Pancreas
Adrenal cortex
Adrenal medulla
Kidney
Skin
Gonads
Silverthorn, Human Physiology, 3rd edition Figure 7-2

18. Homeostasis
Single-celled organisms meet all of their needs by direct exchange with the external environment
Evolution of an internal environment, distinct from external environment, made multi-cellular organisms feasible
Homeostasis allows for conditions of internal (intracellular) environment to remain constant and optimal even when the external environment fluctuates

19. The External and Internal Environments
Materials enter and leave the body
The External
Environment
Exchange cells
Intracellular
fluid
Intracellular
fluid
Extracellular fluid (ECF)
(This is the Internal Environment)
Protective cells
ECF is the interface between the external environment and the cells
Stratton with permission

20. Homeostasis cont.
Homeostasis depends on the ability to regulate the activities of organs and organ systems to keep the internal environment constant
Generally, activities of organs/organ systems are controlled by the nervous and endocrine systems
Failure to maintain homeostasis results in disease or pathology

21. Claude Bernard Silverthorn, 3rd ed.
He recognized that an animal’s independence from changing external conditions is related to its capacity to maintain a relatively constant Internal environment.
Claude Bernard ( )
Silverthorn, 3rd ed.

22. Walter Cannon Silverthorn, 3rd ed.
Recognized that the key to maintaining a relatively stable internal environment is the presence of regulatory mechanisms in the body.
He coined the term homeostasis to describe the maintenance of this stable internal environment.
homeo = similar,
stasis = state
Walter Bradford Cannon ( )
Silverthorn, 3rd ed.

23. Temperature External temps vary enormously
Living cells can function over a narrow (tolerable) range of temps (0-45°C)
Q10 is a measure of temp sensitivity
Q10 = RT/RT-10

24. Q10 and Reaction Rate
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25. Optimal Body Temperature
Ectotherms depend on external sources of heat, such as solar radiation, to maintain body temperature
Endotherms can regulate their body temperature by producing heat metabolically (mammals and birds)

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27. Energy Budgets
Both ectotherms and endotherms can alter their body temperature by altering 4 characteristics of heat exchange b/t their bodies and the environment
Radiation
Conduction
Convection
Evaporation

28. Heat Loss Side Depends on Surface Temp/Blood Flow to Skin
Heatin = Heatout
Metabolism + Rabs = Rout + convection conduction
+ evaporation

29. Reflex Control Pathways Maintain Setpoints
Response Loop
Input signal
Integration of signal
Output signal or response
Feedback Loop
Response feeds back to impact the Input (to correct error signal)

30. Response Loops Stimulus Sensor Afferent Path Integrating Center
Efferent
Path
Effector
Response

31. Negative Feedback Loops
Stimulus
Sensor X
Afferent
Path
Integrating
Center
Efferent
Path
Effector
Response

32. Thermoregulation in Endoderms
Thermoneutral zones and basal metabolic rates
Basal metabolic rates are related to body size
Endotherms respond to cold by producing heat
Shivering heat production
Nonshivering heat production

33. Shivering
Depends on contractile machinery of skeletal muscles to consume ATP
Tremor results
Conversion of ATP to ADP results in heat production

34. Nonshivering Heat Production
Brown fat
Thermogenin uncouples proton movement from ATP production, so metabolic fuels are consumed without producing ATP
Heat is still released

35. Regulatory Thermostat
Controls thermoregulatory adaptations and mechanisms (shivering)
Integrative center is in hypothalamus, which establishes a temperature set point and receives feedback information
Temperature of external environment is sensed by skin sensors (feedforward)

36. Hypothalamus

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