E1: Homeostasis & Cell Physiology

LO: Define homeostasis and explain how the internal environment is regulated through negative feedback

define homeostasis: Homeostasis is the body’s ability to maintain a stable internal environment despite changes in the external environment .

-> cells make up tissues ---> make up organs -->makes up organ systems--> maintain extra cellular fluid ---> surrounds all cells (full circle)

how internal environment is regulated through negative feedback: stimulus : a variable deviates from normal set point (body temp rises) , receptor (sensor) : detects change, afferent pathway (at/towards) ,integration center : compares current value to set point and determines a response, efferent pathway , effector: carries out a response that opposes original change , response : the variable moves back towards set point

ex: temp ^ → thermoreceptors detect change —> hypothalamus activates effectors —> sweating + vasodilation → temp vv back to normal

LO: differentiate between the teleological (the “why”) and the mechanistic (the “how”) approaches to physiological processes

teleological (the why): function of a physiological process, why the body does something in terms of survival EX: why do we sweat? → to lower body temp and prevent overheating

Mechanistic (the “how”) : the specific biological mechanisms involved, explains how a process occurs at the cellular level EX: how do we sweat ? > increased body temp activates thermoreceptors → hypothalamus signals sweat glands → sweat evaporates, removing heat

•LO: List the two major fluid compartments in the body and the typical (relative) fluid

volumes in each compartment.

Intracellular fluid (ICF): supports cellular life

• Fluid inside cells

• 2/3 of total body water

• 28 L in an average adult

Extracellular Fluid (ECF): serves as an exchange medium

• Fluid outside cells

• 1/3 of total body water

• 14 L total divided into

  • interstitial fluid(liquid between cells) (ISF): 11 L

  • Plasma : 3 L

• LO: Describe the levels of organization for cells, tissues, and organs

Cells

• basic living units

Tissues

• Groups of similar cells performing a common function

  • four types : epithelial (lining of skin and internal organs), connective, muscle, nervous

Organs

• composed of two or more tissue types

• carry out specific functions (heart, lungs)

Organ systems:

• groups of organs working together to perform physiological functions

  • ex: cardiovascular, respiratory , digestive, nervous —> organism

Internal environment

extracellular fluid (plasma + interstitial fluid)

once something crosses an epithelium layer and enters the ECF, its part of the IE

External environment

anything outside the body and any any space continuous with the outside

food, air, water, urine in bladder

→ even though theyre in your body , theyre external cause they haven’t crossed an epithelial layer

Systemic, Diffuse response regulated by the Nervous and Endocrine system

Speed of action : endocrine

• slower response, minutes, to hours, to years (think puberty)

• diffuse target: entire tissues and organ structures can be impacted

Speed of action : nervous

• very fast response, often a specific target

regardless of speed of actions, both systems use negative feedback to regulate function