physiology exam 1

homeostasis

the body’s ability to maintain relatively stable internal conditions despite constant changes of the outside world.

• - a dynamic state of equilibrium or a balance in which internal conditions vary but always within limits

• Ex: body temperature, blood levels of vital nutrients, and blood pressure

Variable (parameter)

the factor or event being regulated ex: glucose concentration, blood ph,….

set point

expected value of the regulated varaible

-psychological set point examples:

• body temperature- 98.6 (37 C)

• blood glucose- 100mg/dl

• blood pH- 7.4

homeostatic control

processes involving at least 3 components that work together to regulate varible

• -sensors (or receptors)

• -control (or integrating) center

• -effectors

Sensors/Receptors

monitor the environment and detect stimuli

• -responds to stimuli by sending info along afferent pathway to control center

• ex: thermoreceptors (skin), chemoreceptors, and baroreceptors

control (integrating) center

determines set point

• -analyzes the information and orchestrates an appropriate response

• -sends information along efferent pathway to the effector

• -control centers are often particular sets of neural circuits in brain and spinal cord but can be a group of cells in an endocrine gland

Effectors

carries out control centers response to the stimulus

• -return regulate variables back to set point values include:

  • - muscles (smooth, skeletal, and cardiac)

  • - glands (exocrine and endocrine)

sensor

detects driviation from set point

integrating center

determines response

effector

produces response

stimulus

change in varible

effector

edits response

receptor

detects stimulus

response

change in some variable

integrating control center

compares to set point

negative feedback

turns off or reverses the original stimulus

positive feedback

enhances and up-regulates the initial stimulus (usually harmful to the body)

• - homeostasis is maintained by both

negative feedback mechanisms

most homeostatic control mechanisms are negative feedback mechanisms

• - cause a variable to change in a direction opposite to that of the initial change returning to ideal value

• - negative feedback loops FLUCUATE around a SET POINT in a attempt to minimize change

thermoregulation

blood vessels dilate and raise to surface of tissue to decrease body temp. Blood vessels constrict and go deeper into tissue to increase body temperature

Blood Ca2+ levels

release of calcitonin makes calcium rise, decrease in calcium causes release of parathormone. The thyroid secretes calcotonin which will decrease blood Ca2+ levels

positive feedback mechanisms

the actions of effectors AMPLIFY the original stimulus to an ENDPOINT

• - positive feedback are referred to as cascades that amplify original stimulus

• - an initial stimulus produces a response that amplifies or escalates the original change rather than opposing it

• - positive feedback loops are typically found when a potentially dangers or stressful process must be completed quickly

• Ex: spiking fever, blood clotting, ovulation, childbirth, and nerve signaling

blood clotting

cut vessel, platelets stick and release chemicals which attract more platelets causing them to stick to each other which releases more chemicals

childbirth

head stretches cervix, stretch receptors send signal to hypothalamus. Hypothalamus stimulates pituitary gland to secrete oxytocin stimulate pituitary gland to secrete oxytocin, oxytocin stimulates uterine contractions, pushes head toward cervix and stretches it

homeostatic imbalance

causes most diseases. When regulated variables can NOT be returned to set point values for ANY reason

atoms

the basic structural unit of matter

protons

positively charged particles weighing 1 atomic mass unit (1.67 × 10-24 grams) in nucleus

neutrons

neutrally charged particle weighing approximately 1 atomic mass unit (AMU) in nucleus

electrons

negatively charged particles weighing zero in various orbitals outside the atomic nucleus

atomic number

number of protons

ion

when the number of electrons change

isotope

elements that have 2 or more variations based on a differing # of neutrons

• - sometimes radioactive

• - most common/stable isotope reflected on periodic table

atomic mass

number of protons and neutrons (always a whole number)

polyatomic ions

ion composed of more than one atom

• ex: NH4+, Bicarbonate (HCO3-), PO4

chemical bonds

molecules form by chemical bonding between valence electrons of atoms

• - the term valence shell refers to an atom’s outermost energy level

octet rule

Except for shell 1, which is full when it has 2 electrons, atoms tend to interact in such a way that they end up having 8 electrons in their valence shell

3 major type of chemical bonds

ionic, chemical, and hydrogen

ionic bond

occur when valence are transferred from one atom to another (result from transfer of electrons between atoms)

• - forms charged atoms (ions)

• - atoms that lose electrons become a cation (+ charged)

• - atoms that gain electrons become a anion (- charged)

• - weaker than polar covalent bonds

• - dissociate when dissolved in water

• ex: NaCl→ electrolytes- if it dissolves in water

cation and anions are electrically attracted to each other

covalent bond

formed by sharing of valence electrons to fill the valence shell

• - hydrogen gas, oxygen gas, and methane are nonpolar because electrons are shared equally

• - water is polar because electrons are shared unequally

molecular shape and the relative electron attracting abilities of atoms determine polar or nonpolar

nonpolar covalent bond

electrons are shared equally

ex: H2, O2, or CO2

shape: linear and symmetrical

polar covalent bond

electrons are shared unequally

• - pulled more toward one atom- due to greater electronegativity have (+) and (-) poles

• - oxygen, nitrogen, and phosphorus have strong pull

• - tend to form polar molecules

• ex: H2O is bent, or V-shaped due to oxygens strong electronegativity, the e- are pulled twoard O and shared unequally

Hydrophilic

molecules are soluable in water = polar

• - because readily form hydration spheres

• - Ex- glucose and amino acids

water loving

Hydrophobic

molecules are nonpolar, cannot form hydration spheres

ex: lipids → fats and cholesterol

Hydrogen bonds

when H forms polar bond with another atoms it takes on a slight + charge

• - making it attracted to any nearby negatively charged atoms

• - called hydrogen bonds: intramolecular bond, forms between adjacent H2O molecules, and creates surface tension

responsible for tendency of H2O molecules to cling together and forms referred to as surface tension

pH

symbol for H+ concentration of a solution

• - scale runs from 0 to 14

• - pure H2O is neutral = pH is 7

• - acids less than 7

• - bases greater than 7

Hydrogen ions are very acidic

has to be 7 to be neutral

* scale is a factor of 10

Acid

a substance that releases H+ in detectable amounts

• - when they disassociated they release H+ ions and anions

• - an increase in H+ concentration H+ will decrease pH

Ex: HCl—- H+ + Cl-

Bases

a substance that takes up H+ in detectable amounts

• - when bases dissociate in water, they rleease hydroxyl ions (OH-) and cations

• - a decrease in H+ will increase pH

Ex: NaOH—- Na+ + OH-

Buffers

any substance or system that can stabilize the pH of a solution by either binding to or releasing ions

ex: the bicarbonate buffer system in blood

blood pH- 7.4

isotope

the same element but has a different atomic mass

• - same number of protons but differ in number of neutrons and therefore are a different AMU

• - extra neutrons increase atomic mass

• - the atomic weight is the averafe of the atomic mass of ALL the different isotopes of an element

Radioactive isotopes

Heavier isotopes of many elements are unstable and their atoms decompose spontaneously into more stable forms

• - this process of atomic delay is called radioactivity and isotopes that exhibit this behavior are called radioisotopes

half life

the time required for a radisotope to lose ½ of its activity

ex: Tc has a half life of 6 hrs