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Homeostasis and the Organization of the Human Body


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What is homeostasis?
- greek word meaning "to stay the same"
- internal state better described as dynamic equilibrium.
How are equilibrium conditions maintained?
by feedback mechanisms.
- Negative Feedback: counteracts the effects of changes (ex, thermostat)

-Positive Feedback: reinforces changes to serve a phyiological need. (ex. pregnancy)
What is the control center of the body?
What is the Human body set point?
The human body set point is 98.6 F. (can vary by 1 degree)

The control center of the body is the hypothalamus.
What happens to maintain body temperature?
1. Nerve endings act as temp. sensors and send info to hypothalamus.
2. When temp drops, hypothalamus activates effector mechanisms to raise temp.
*shivering - produce heat
*blood vessel constriction
*blood vessel dilation
*chemical signals to raise metabolic rate.
How is the human body organized?
cells - tissues - organs - organ systems.
Body Cavity?
1. Cranial (brain)
2. Thoracic (chest)
3. Abdomincal (belly)
4. Pelvic (lower digestive system)
What are tissues?
What is the study of tissues called?
What are the four types of tissues?
Tissues are composed of cells that are similar in structure and perform a specialized function.

The study of tissue is called histology.

1. epithelial
3. Muscular
4. Nervous
*epithelial cells which encase all internal and external surfraces.

6 Functions:
1. Protection
2. Absorbtion
3. Sensation
4. Secretion
5. Excretion
6. Surface Transport

Common Characteristics:
- layers are usually only a few cells thick
- tightly packed
- few blood vessels
- can regenerate
How can the tissue be classified?
1. Squamous : flat, thin linings

2. Cuboidal: looks like cubes

3. Columnar: looks like columns

1. Simple: 1 cell thick

2. Stratified: 2 or more layers

3. Psudostratified: only appears layered

4. Transitional: can stretch
Connective Tissue
- diverse (many functions)
- vaired composition
- cells usually spaced well apart and embedded in a non-living matrix made up of fluid, gel, fibers, or crystals.

1. defense (from antigens)
2. Structure
3. Isolation, Storage, Transport
Defense (connective tissue)what are the three cell types?
- type of white blood cell
- part of immune system

- surround and digest foreign particles

Mast Cells
- produce histamine to dilate blood vessels near site of injury.
Structural (connective tissue)
three cell types?
- stay in one place
- flat, branching, irregular shape
- secrete 4 types of protein fibers into matrix....

1. Collagen fibers
- protien collagen
-wavy and strong

2. Reticulin Fibers
- protein collagen
- fine and branching

3. Elastic Fibers
- protein elastin
- fibers branch

4. Loose
- collagen and elastin fibers

Cartilage cells:
- produce cartilage
- firm, flexible, non stretchy
- contain lacunae: chambers which hold individual cells after matrix secreted

3 types of carilage -->
1. Hyaline Cartilage: end of long bones, fine collagen fibers

2. Elastic Cartilage:
small amount of elastin

3. Fibrocartilage: great ammount of support
thick bundles of collagen absorbing shocks

Bone cells: also called supporting c.t.
produce bone.

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