Unit 1 - Homeostasis & Cell Communication Flashcards
what is the definition of physiology?
the study of the functions of living organisms and their parts
levels of organization in the body
cell –> tissue –> organ –> organ system –> organism
four classification of cells
- neurons
- muscle cells
- epithelial cells
- connective tissue cells
four major tissue types
- nerve tissue
- muscle tissue
- epithelium
- connective tissue
(correspond to cell types)
what are organ systems?
- a group of organs
- organized to perform more complex functions that any organ alone
what is homeostasis?
- the ability to maintain a relatively constant internal environment
- requires organ system integration
role of negative feedback loop in homeostasis
- negative feedback is important because it triggers changes in the regulated variable if becomes too high or too low from set point
- works to counteracts a change in the body (i.e temperature) back to its set point
what is the mechanism to maintaining homeostasis?
- sensors within in the body (aka neurons) are sensitive to a certain variable, such a temperature
- these sensors relay signals (input) to an integrating centre which compares the regulated variable to the desired set point
- an appropriate response is orchestrated within the brain or a gland
- to carry out the response, the integrating center relays signals (output) to the cells, tissues or organs that illicit the final response.
what organ system doesn’t maintain homeostasis? why?
- the reproductive system
- it functions to maintain the species (produce offspring) and not the individual
what components of the internal human environment are regulated?
- temperature (37 +/- 2)
- volume of fluids
- composition of fluids
why is homeostasis important?
- the body needs stable internal and external environments for it to operate
- if homeostasis is not restored, potentially introduces illness, disease or death
afferent
towards the CNS from PNS
efferent
away from CNS to PNS
effectors
refers to cells/tissues/organs that are effected, and receive a signal to respond to
affector
refers to a structure that affects others or sends a signal out.
structures that help maintain homeostasis
- receptors
- integrating centers
- effectors
- signals
role of receptors
- to detect physiologcial variables
- i.e heat, stretch, pressure
examples of receptors in the body
- thermoreceptors
- chemoreceptors
- baroreceptors
role of integrating centers
- orchestrates an appropriate response
- many integrating centres are found in the brain
role of effectors
- responsible for facilitation of a response in the body
- receive signals
role of signals
- allow components (receptors, effectors and centers) to communicate
what are the different signals in the body?
- input signal: receptor to an integrating center
- output signal: integrating center to an effector
2 ways cell communicate
- electrical signals
- chemical signals
what are electrical signals?
- changes in membrane potential to adjacent or long-distance cells
what are chemical signals?
- proteins secreted by cells into the ECF and go to neighboring cells
- include cytokines, hormones, neurotransmitters
what are target cells?
cells that receive messages which can illicit an appropriate response within the body
3 stages of signal transduction
- reception = key + key hole (cell affinity with a messenger)
- transduction = convert into message that can illicit a response
- response - changes within a cell
how do cells communicate locally and long distances?
local = using special junctions
long distance = combination of electrical (nerves) and chemical (blood) signals
3 main types of special junctions
- tight junctions
- desmosomes
- gap junctions
role of tight junctions
- occludins fuse adjacent cells together to form a continuous (nearly impermeable) barrier between epithelial cells
- molecules must go in/out of cell via diffusion or active transport through epithelium rather than space between plasma membrane
role of desmosomes
- to provides strength and adherence between adjacent cells so that the cells do not tear apart when the tissue is subjected to stress (i.e cardiac muscle, skin, bladder)
role of gap junctions
- membrane proteins connect adjacent cells creating channels
- allow for adjacent cells to communicate and exchange ions/molecules rapidly with each other
two types of intercellular communication
1.) direct communication between adjacent cells
2.) indirect communication using chemical messengers to act on specific receptors
what are autocrine and paracrine signals?
autocrine = a cell secretes a hormone that acts on the receptors on the same cell
paracrine = a signal secreted by one cell and act on nearby target cells (if it has the particular receptor for the chemical messenger).
role of membranes
- separate material between ICF and ECF
- allows for exchange of material between ICF and ECF
why is transport across membranes important?
- helps obtain oxygen and nutrients to processes can occur within a cell
- helps get rid of waste product (i.e CO2, H+ eliminated)
what is a selectively permeable membrane?
the membrane allows for the transport of some molecules but is restrictive to others
what molecules easily pass through a membrane?
- non polar molecules
–> includes O2, CO2, fatty acids
what molecules don’t usually pass through a membrane?
- ions and polar molecules
–> includes glucose, proteins, Na+
what factors affect transport across a mebrane?
- chemical and electrical forces (electrochemical gradient)
- depends on charges of a molecule
- depends on the polarity of a membrane
passive transport
- spontaneous, doesn’t require energy
- downhill movement i.e simple diffusion
- “high to low concentration”
active transport
- requires energy
- non-spontaneous i.e the use of pumps
- uphill movement
- “against the concentration gradient, low to high concentration”
what is a chemical driving force?
- is created by a concentration gradient across a membrane
- a force that “pushes” molecules down a concentration gradient spontaneously, from high to low concentration