Organization of the Body and Homeostasis

Physiology

the study of the normal functioning of a living organism and its component parts

• includes chemical and physical properties of the body

• involves the integration of function across all levels of organization and the entire organism

Types of cells

200 distinct cells

4 broad categories formed from cell differentation

• epithelial

• connective-tissue

• neurons

• muscle

Epithelial cells

found at surface of body or hollow organ

• specialized to secrete or absorb ions and organic molecules

Connective-tissue cells

from extracellular elements that connect, anchor, and support body structures

Neurons

cells of the nervous system that are specialized to initiate, integrate, and conduct electrical signals to other cells

Muscle cells

specialized cells that contain Actin and myosin filaments capable of generating force and movement

tissues

collection of cells that carry out related functions

• 4 types: epithelial, connective, nervous, muscle

organs

composed of multiple tissue types and carry out related functions

• example (blood vessels have layers of smooth muscle cells, endothelial cells, and fibroblasts)

organ system

contain multiple organs that work together

• example: the urinary system has the kidney, ureters, urethra, bladder

integumentary system

composed of the skin

forms a protective boundary that separates the body’s internal environment from the external environment

Digestive system

takes up nutrients and water and eliminates wastes

reproductive system

produces eggs or sperm

immune system

provides defense against foreign invader

endocrine system

coordinates body function through synthesis and release of regulatory molecules

nervous system

coordinates body function through electrical signals and release of regulatory molecules

circulatory system

transports material between all parts of the body

respiratory system

exchanges oxygen and carbon dioxide between the internal and external

musculoskeletal system

provides support and is responsible for movement

urinary system

maintains water and solutes in the internal environment; waste removal

intracellular fluid

fluid located inside cells

extracellular fluid (ECF)

composed of both the fluid in the blood (plasma) and fluid surrounding the cells (interstitial fluid)

• serves as a buffer zone between cells and the outside environment

Interstitial fluid

fluid surrounding the cells

located within the interstitium

Total Volume of body fluid

67%: intercellular fluid

26% interstitial fluid

7% plasma

Homeostasis

the relatively stable conditions of internal environment that results from regulatory system actions

• physiology: homeostasis is maintained

• pathophysiology: homeostasis is not maintained

Dynamic constancy

levels change over short period of time, but remain relatively constant over long periods of time

ex: blood glucose levels peaking after eating, returning to set point via homeostasis

reflex

biological control system linking stimulus with response to maintain homeostasis

• specific INVOLUNTARY, unpremeditated, unlearned “built-in” response to a particular stimulus

reflex arc

mediates a reflex

components: stimulus→receptor→afferent (incoming) pathway→integration center→ efferent (outgoing) pathway→ and effector

stimulus

a detectable change in the internal or external environment

receptor

detects the change

afferent pathway

the pathway the signal travels between the receptor and the integrating center

integrating center

can recieve signals from many receptors, some of which may respond to quite different types of stimuli

efferent pathway

pathway along which information travels AWAY from the integration center to the effector

Effector

2 specialized classes of tissues: muscles and glands

• major effectors of biological control systems

Negative feedback

• regulates reflex arcs

• shuts the system off once the set point has been reached in order to keep the system at or near the set point

Positive feedback

reinforces a stimulus and are NOT homeostatic

• triggers a cycle of ever increasing response

• ex: childbirth and the release of oxytocin