# Scientific Investigation Lab

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### descriptive statistics

measures of central tendency (mean, median, mode) + measure of dispersion (range, variance, standard deviation, standard error)

### normal distribution

parameter vs. frequency... 68, 95, 99% within tha +/- 1, 2, 3 standard deviations (delta/ s) of the mean.

### 95% CI

if the 95% CI overlap, the groups are not different from one another.

### t-test

compare the means of 2 populations/ distributions

### ANOVA

compare the means of more than 2 populations

### regression

"r2"... ANOVA. cause-and-effect relationship???... mathematical equation

### correlation

"r from -1.0 to +1.0"... assumes no cause-and-effect relationship b/w the variables... association??... measures the direction and strength of the linear relationship...

### P-value

=probability. If P < 0.05, the individuals are significantly different from each other.

### Null hypothesis (H0)

A statement of no difference

N vs. n

### parameter vs. statistic

Population vs. Sample

### variable>>variates

characteristic>>scores

### accuracy & precision

nearness of a measurement to the actual value of the variable & closeness of repeated measurements of the same quintity

### Homeostasis

dynamic internal constancy... Claude Bernard "an organism remains constant despite changes in the external environment surrounding the organism"

### The body maintains homeostasis with a set of sensors and physiological mechanisms that can be activated or inhibited accordingly.

Any deviations from the set point will be detected by the sensors which will stimulate mechanisms to return the body to the set point.

### Feedback mechanisms = feedback loops... response becomes the stimulus!

(stimulus) -- sensors (single cells/ multiple cells in a gland or organ) --integrating center--effectors -- response

### Negative feedback

responses are in the "opposite" from the initial stimulus/ disturbance in homeostasis... keeping the right body temp.

### Positive feedback

responses are in the "same" as the initial stimulus/ disturbance in homeostasis... blood clotting & the enhancement of labor contractions during birth

### Positive feedback

inherently unstable and always move the system farther away from homeostasis

### Solution

a uniform mixture of solute and solvent (liquid)

### diffusion

movement of molecules

### net diffusion

net movement of molecules from an area of high conc. to an area of low conc.

### Rate of diffusion is dependent upon...

(1) conc. gradient (2) permeability & thickness of the semipermeable membranes (3) surface are of the semipermeable membranes (4) size of the molecules diffusin (5) temperature

### Diffusion with no energy required from high conc. to low conc.

diffusion, osmosis (MW of water = 18g/mol) , facilitated diffusion (protein transporter)

active transport

### osmosis

net movement of water = solvent from an area of low solution conc. to an area of high solute conc.

### osmotic pressure

tendency of a solution to elicit osmosis... # of molecules (such as NaCl) i.e. 1 Molar of anything contains 6.02*10 to the 23 molecules

Na+ Cl-

### Osmolarity

# of particles (such as Na+) that will generate osmotic pressure

mol/ L

### osmolarity

ex) mol/L Na+ + mol/L Cl-

### Tonicity

"relative" differences in osmotic pressure/ conc. among different solutions

### hypotonic solution

lower conc. of solutes ex) swimming pools

### hypertonic solution

higher conc. of solutes ex) seawater

### isotonic solution

same solute conc.

### Action potential is caused by...

the movement of ions, particularly Na+ and K+

### How does the nervous system communicate?

through action potentials

### ion gradients across the human cell membranes are established by...

active solute pumps using ATP... ex) Na+/K+ pump that moves both ions against their conc. gradients

### Na+/K+ pump moves...

3 Na+ out of the cell and 2K+ into the cell for every 1 ATP molecule... maintains both a conc. gradient AND an electrical gradient.

relative diff. in the # of Na+ and K+ present in the intra- and extracellular fluids... more K+ inside the cell and more Na+ out side the cell

Na+/K+ pump --> separations of electrical charges (ions)

### resting membrane potential

-70 mV for a nerve cell. V across the cell membrane while the cell is at rest.

### Resting membrane potential is created because of...

(1) diff. in the ion concentrations on the O vs. I of the cell membrane (2) relative permeability of the plasma membrane to Na+ and K+ ions (3) conc. gradient of Cl-

### Gldman-Hodgkin-Katz eq.

resting m.p = -70 for a nerve cell

### Nernst eq.

equilibrium potential (= electrical potential needed to balance an ionic conc. gradient so that the net flux of that ion is 0) for each ion such as Na+

### voltage-gated Na+ and K+ channels

when a neuron receives an electrical stimulus, it induces voltage-gated Na+ and K+ channels in the cell membrane to open

### K+ channels are

slower than Na+ channels

### Na+ channels have

a faster rate of response to voltage changes across the membrane and an extra intracellular structure known as an inactivation gate which limits the influx of Na+ ions into the cell by blocking the channel shortly after depolarization opens it...

### depolarization

both the electrical and conc. gradients of Na+ move Na+ into the cell... -70 to +30

### repolarization

both the electrical and conc. gradients of K+ move K+ out of the cell

### hyperpolarization>>afterhyperpolarization

overshoot of the resting membrane potential by K+ efflux

### threshold voltage

-55mV... If the stimulus opens enough voltage-gated Na+ channels to depolarize a neuron to its threshold voltage then an action potential can be generated.

### An action potential is an...

all-or-none principle

### amplitude of depolarization

does not depend on the stimulus strength/duration but the chemical properties of the voltage-gated ion channels & the conc. and electrical gradients of the cell

### def. action potential

a brief all-or-none depolarization of the cell membrane... has a refractory period and a threshold

### def. threshold potential

membrane potential at which an action potential is initiated

### def. resting membrane potential

steady transmembrane potential of a cell that is not producing an electric signal

### refractory period

time during which an excitable membrane does not respond to a stimulus that normally causes response

### def. equilibrium potential

at the eq. potential for an ion, there is no net movement of the ion because the opposing fluxes are equal, and the potential will undergo no further change...

### absolute refractory period

time period following an action potential during which a second action potential cannot be generated, no matter how strong the stimulus

### relative refractory period

a second potential may be generated, but it requires a stimulus stronger than the one that generated the first action potential

### compound action potential

sum of the all the action potentials... voltage change across the nerve rather than a single axon

### EPSP (excitatory postsynaptic potential)

electrical response in the postsynaptic cell at an excitatory synapse

### IPSP (inhibitory postsynaptic potential)

electrical response in the postsynaptic cel atan inhibitory synapse

### Action potentials are generally initiated by...

the temporal and spatial summation of many EPSPs.

### the postsynaptic cell's potential is the result of...

temporal and spatial summation of the EPSPs and IPSPs at the many active excitatory and inhibitory synapses on the cell.

### Reflex

an involuntary and stereotypic response to a stimulus to maintain homeostasis

### learned responses are

NOT innate reflex responses

### As the experiment is repeated enough times, the unlearned response will become a learned response!

unlearned response times using an auditory cue

### reflex arc

sensory receptors -- sensory/ afferent neurons (dorsal root) -- synapses in the spinal cord -- motor/efferent neurons (ventral root) -- effector

### reflexes occur in...

(1) somatic nervous system (2) autonomic nervous system

### Effectors of somatic reflexes are skeletal muscles which are usually under voluntary control and the effect is always

excitatory = causing a muscle contraction...ex) patellar tendon reflex

### autonomic nervous system reflexes assist in regulating the activity of physiological systems such as endocrine, cardiovascular, repiratory, urinary, and digestive systems which are NOT under voluntary control and the effect is

either stimulatory OR inhibitory, depending on the neurotransimitter released by the efferent neuron and the receptor type present on the effector.

### Autonomic reflexes occus in...

(1) SNS (2) PNS sym and para.

### Reflec occur very quickly in response to a stimulus because...

processing by higher brain centers is not required for the reflexive action.

### Ipsilateral reflex

reflex occurring on the same side as the stimulus

### Contralateral reflex

reflex occurring on the opposite side of the stimulus

### The patellar tendon stretch reflex is...

an ipsilateral monosynaptic reflex, in which the sensory neuron synpases DIRECTLY onto the motor neuron... no interneurons!!

### Reciprocal inhibition

in stretch reflexes, the antagonistic muscle group is simultaneously inhibited from contracting.

### In the patellar tendon stretch reflex, some afferent neurons synapse on inhibitory interneurons... this part of a stretch reflex is

polysynaptic!! includes interneurons.

### def. transduction

process by which stimulus energy is transformed to an electrical response

### Meissner's corpuscle, Merkle's corpuscle, Pacinian corpuscle, and ruffini corpuscle

are mechanoreceptors

### Free nerve ending

some are nociceptros, some are thermoreceptors, andsme are mechanoreceptors

### modality

= type of sensory stimulus... ex) heat, cold, sound, pressure...

### Sensitivity of a certain area depends on...

(1) density (2) receptive fields of somatic sensory receptors

### sound wave conduction through...

air, fluid, solids (=bone)... compression & rarefraction

### frequency -->

pitch of the sound

### amplitude-->

loudness of the sound

### how do sound waves get transmitted?

external auditory canal -- tympanic membrane -- ossicles (malleus, incus, and stapes) -- cochlea (sterocilia of hair cells transduce mechanical stimulus of sound pressure waves into nerve impulses)

### Cornea and lens

focus light rays onto the retina

### rods

low light perception, black-and-white vision

### cones

less sensitive to light, color vision

### fovea centralis

area of highest visual acuity

### blind spot

where the optic disc occurs

### accommodation

process of keeping an object in focus as it is moved closer to the eye

### At the infinite distans = 20 ft.

the light entering the eye from an object are parallel and naturally focused on the fovea centralis and the lens is in its RELAXED state

### presbyopia

age-related decline in the ability to accommodate for near vision

### hyperopia = farsightedness

short eyeball/ images of near objects converge at a point behind the retina... corrected with a convex/ converging (+) lens

### myopia = nearsightedness

long eyeball/ images of far objects focus at a point before the retina.. corrected with a concave/ diverging lenses (-)

### visual acuity

ability of the lens to refract the light to focus an image on the retina

### diopter

=1/ focal length (from lens to the focal point on the retina) in meters... measures refractive power of a lens... visual acuity

### the snellen eye chart is based on

a visual angle of one minute!

### conduction deafness

hearing inability due to impaired conduction of sound waves in the middle ear/ cochlea

### sensorineural deafness

hearing inability due to impaired transduction from the cochlea to the auditory complex

### Weber's test detects...

sound perceived by the damaged ear due to bone conduction is not dampened and seems louder --> conduction deafness

### Rinne's tests are used to distinguish

the cause of conduction deafness...bone is more efficient at conducting sound waves than the middle ear --> conduction deafness due to middle ear damage

Example: