Chapter 1: Homeostasis Flashcards
Physiology
the study of how the body functions. Many levels and integration (work together)
Pathophysiology
the physiologic basis of disease
Levels of organization
1) chemical
2) organelles
3) cells
4) tissues
5) organs
6) organ systems
7) organisms
Chemical level of organization
most simple level
Cells
basic structural and functional units of life (differentiate during development)
- 4 main types: muscle, nerve, connective tissue, and epithelial
Muscle cells
contract and generate movement
Nerve cells
initiate and conduct electrical signals
Connective Tissue Cells
connect, anchor, and support structures in the body
Epithelial Cells
- Selective, secretion, and absorption of ions and organic molecules and for protection.
- Cover and line the body’s surface.
- Make glands and form absorptive cells in intestines and kidneys
Tissues
Groups of differentiated cells with similar properties
- 4 types: muscle (skeletal muscle/cardiac muscle/smooth muscle), nerve tissue, connective tissue, epithelial
Muscle Tissues
- contract and generate movement of certain muscles
- 3 types: skeletal, cardiac, smooth
Skeletal muscle tissue
movement of entire body
Cardiac muscle tissue
contraction of the heart
Smooth muscle tissue
movement of internal organs
Nerve tissue
makes up brain, spinal cord, and nerves
Connective tissue
bone, cartilage, and blood
Epithelial tissue
covers and lines body and lines organs and intestines
Organs
structures composed of 2+ tissues that perform a specific function and usually have a recognizable shape (i.e. heart, brain, lungs, liver, kidneys)
Functional Units of Organs
responsible for performing actual function of the organ (i.e. the nephron of a kidney)
Organ systems
collection of organs that work together to perform an overall function
Organism
most complex level of organization. Collection of organ systems that work together.
Internal environment
fluids that surround the cells and exist in blood
Fluid compartments
extracellular and intracellular
Extracellular fluid
- outside the cell
- plasma component: 20-25% fluid in blood vessel
- interstitial fluid: 75-80% directly surrounds cells
Intracellular fluid
fluid within cells
Compartmentilization
achieved via barriers (regulation of the movement of substances between compartments)
- capillary membrane only lets certain things through
Body water
- 55-60% body weight in males (less in females because more fat and fat has less water in it)
- 2/3 body water is intracellular, 1/3 extracellular
Homeostasis
- Maintenance of relatively stable internal environment
- physiology variables maintained in narrow range of ‘normal’ that fluctuates around a setpoint
- compensatory mechanisms restore conditions
- dynamic process. Detects and responds to deviations in physio variables
Negative feedback
- MOST COMMON
- response moves variable in opposite direction of original stimulus
- moves back toward normal setpoint
Positive feedback
- exacerbates effect of original stimuli
- accelerates a physiological pro
- pregnant lady increases uterine contractions
Feedforward Regulation
- produces responses that improve the speed of homeostatic responses and minimizes deviation of the regulated variable from the set point
- anticipates changes in regulated variables
- minimizes distance to setpoint
Resetting of set points
- not all set points are static
- some may change or be reset for health purposes (i.e. get fever to kill viruses)
Homeostatic control systems
- are reflexes
Reflex and reflex arcs
- reflex: specific involuntary responses to a particular stimulus
- reflex arc: pathway mediating the reflex with 3 components (receptor, integrating center, and effector)
Stimulus
change in environment
Receptor
detects change from stimuli
- very specific
integrating center
recieves input from receptor and determines the change need to be made to fix it.
- determines the response
Effector
produces the response that changes the variable (usually a muscle or gland)
Response
actual response/change that occurs
Organ system that controls homeostasis
- nervous and endocrine systems
Nervous system control of homeostasis
nerve reflexes
Endocrine system control of homeostasis
hormones that circulate through blood and stimulate specific target cells
(i.e. endocrine systems = integrating center and hormones = effectors)
Four chemical messengers that maintain homeostasis
hormones, neurotransmitters, paracrine substances, and autocrine substances
Hormones and Neurotransmitters
systemic levels
Paracrine substances
- locally
- paracrine released into the interstitial fluid by cells and effect nearby cells
Autocrine substances
affect the cells that release them
Three states of total-body balance
- negative balance
- positive balance
- stable balance
Negative balance
- loss exceeds gain (amount decreases overall)
Positive balance
- gain exceeds loss (amount increases overall)
Stable balance
- gain equals loss (amount stays the same)
pool
- body’s readily available quantity of substance (amount present in ECF)
- total amount of substance in body depends on the relative rates of net gain and net loss for particular substance
- pool concentration depends on both total amount of substance in the body and upon exchanges of the substance within the body
- potential inputs and outputs can effect the pool of a material
