in terpretation of sensations: what that sensation means to you 

ex) some see number 3 as yellow 

Sensory system:

1.   Reception = absorb stimulus / ability of stimulus to be detected

2.   Amplification = ramp up with G Proteins. so it can be detected.

        Ex) we can detect a single photon. How? Amplify.

3.   Transduction = ions move across membrane

ex) turn signal into language

4.   Transmission = only way to have transmission is to have action potential to CNS. (CNS can only understand language of action potential)

5.   Integration = process > turned into perception. 

amplification

amplification of external stimulus through molecular (G protein) or physical (hearing) means

• essential for amplicification is G protein 
• sight: transducin 
• smell: g protein
• hearing: no G protein here but a physical amplification btw tympanic membrane and oval window

• Ex) one photon will lead to the closing of a million Na+ channels--> more photon, more closing, more polarizaiton, more bright

covers 7 actins

lies on top of actin. 

 mechanoreceptors:*

·      Respond to shape change from being pulled or pushed

·      Convert mechanical energy to electrical signals

·      Function: help maintain body position with respect to gravity; constantly sends info to CNS about position and movement of body and internal organs (food in belly)

1.  Touch Receptors:

- Dendrites: detect touch, pressure and pain.

-Tactile receptors: at the base of hair / epidermis

-  Simulated indirectly and only when moving

    EX ) Merkel Disc

  -  Encapsulated endings: at dermis / covered by connective tissue

§  Meissner corpuscles

§  Ruffini corpuscles

§  Pacinian corpuscles

2. Proprioceptors:

   o   Help maintain postural relations (coordinate muscle movement) ex) allow us to dress in the dark

   o   Responds to tension and movement

§  Muscle Spindle

§  Golgi tendon organs

§  Joint receptors

3.Gravity receptors: statocysts

4.  Hair cells

5.  Lateral Line

·6.  Vestibular apparatus

·7. Auditory receptors 

 pacinian corpuslce 

ú  surrounded by layers of Schwann cell

ú  these take the most pressure to distort

ú  ex) when you feel that deep vibration. 

meissner’s corpuscle

ú  ex) lips /finger tips (hairless)

ú  adapt very quickly (means that we feel it and then it forgets/ignores quickly) 

sclera

o   white of your eye

o   mostly collagen, tough connective tissue

cornea

·      seen outside the body but kept alive.

o   when sclera gets to the front of your eye, it becomes cornea and becomes opaque

myofibril

• ·      can change the number of myofribils from exercise (change muscle massbut not the number). 
• myofibrls are striated the whole thing looks striated
• endoplasmic reticularum/sarcoplasmic reticulum membrane that holds onto Ca surrounds every myofibril
• because the T tubual goes down every Z line, action potential that was on surface goes through T tubual > trigger Ca channel and myofber are filled Ca > muscle contraction 

made of actin

·      switches between G-actin (globular)(ball) polymerize to F-actin: polymerization makes  a beaded chain

on top of it, there's tropomyosin held to the actin by troponin. 

one end of sacromere to another

called Z line bc micrscopy shows it being flat but is really round

 B/W vision (125 million cells)

§  opsin + retinal = rhodopsin

§  wavelength nonselective: don’t know the difference. 

§  absorbs "rainbow"

color vision  (6 million) 

§  3 different variant  = red, green, blue

§  wavelength matters.

§ usually find PHOTOpsin

·      allows you to focus 

three types: 

1. rods

2. cones 

3. photosensitive ganglion cells 

• specialized type of neuron found in the retina 
• allows phototransduction - Convert light energy
•  Have pigments that absorb light energy ex) rhodopsins

• the filaments of myofibrils constructed from proteins, 
•  two types, thick and thin. 
• seen in skeletal and cardiac muscle
• organized in repeating subunits (sacromeress) along the length of myofibiril

• aka "lockjaw" 
• prolonged contraction of skeletal muscle fibers
• only affects skeletal muscle

• composed of protein myosin
• bumps on both sides in different orientation and nothing in the middle bc have tail to tail connection in the middle.
• bumps: dimers of myosin 
• head can undergoes 45 angle change 

point of connection where skeleton and muscle meets where the connection is the least movable. 

• motor protein 
• only in eukaryotes 
• make up "thick filaments" in myofilaments
• many polypeptides + dimers as heads.
• while at rest, holds onto ADp and Pi
• they are atpases

technically only where there's only thin filament

but can span within two z line and can spans btw two sacromere bc of overlaping 

o   where thick filaments reside

o   end to end of thick filaments

o   never shortens whether relaxed or contracts

o   defined as a certain length

pigment of the retina 

responsible for creating photoreceptor cells 

protein opsin + retinal

exist in cis and trans form

sensitive to light 

when exposed to light, pigment, "photobleaches"

allow vision in the dark

• troponin coordinate tyropmyosin position on actin.
• glue that holds tyropmyosin and actin together

has three subunits

1. troponin C – binds to calcium

if Ca not bound, myosin and actin are invisible

if Ca are bound, shape changes actin and myosin can see each other. Calicium control actin and myosin interaction

2. troponin T – binds to tropomyosin

3. troponin I – binds to actin

1. sensory receptors for auditory and vestibular system 
2. function as sound detectors and amplifiers
3. located in inner ear > Corti > cochlea > on thin basilar membrane 
4. have sterocilia 
5. damage to this causes deadness

1. transparent 
2. lens + cornea = help refract light and allow to be focused on retina
3. allows for accommodation: can change shape > function to change focal distance 

1.  ear - part that is outside the head 
2. function: collect sound, amplify and direct to auditory canal 

• btw eardrum and oval window
• has malleus, incus and stapes
• hollow space here is called tympanic cavity
• function:

1. allows pressure to equalize in the eustachian tube

        2. transfer sound waves to fluid waves

3. amplify sound

• involuntary striated muscle 
• found in heart 
• have myocytes 
• has a lot of mitochondria

• undulating double membrane separating adjacent cells in cardiac muscle fibers
• support cardiac tissue contraction

function: 

1. hearing

2. balance

3. position within gravitational field 

4. de/acceleration

• has membranous labyrinth inside bony labyrinth 

in membranous labyrinth..:

you lose sense of equilibrium if you damage it

there is vestibular:

  1. sacculue and utricle (has stereocilia)

  2. three semicircular canal (give info about how we should turn our head)

bony labyrinth:

1.cochlea (hearing) 

2.vestibular system (balance)

organ of Corti

• part of inner ear 
• has thousands of "hair cells" - the auditory receptor for hearing 
• hair cells rest on basilar membrane 
• stereocilia of hair cell extends into cochlear duct. 

layer of connective tissue

btw retina and sclera 

provide oxygen to outer layers of retina

• membrane 
• control diameter of pupil 
• control amt of light reaching the retina
• controls "eye color" 

·      Vision starts here

·      have photoreceptors (rods and cones)

• tissue/layers of neurons interconnected by synapses
• lines the inner surface of the eye
• light sensitive -when light hits the retina, it triggers nerve impulses

sarcoplasmic reticulum

have a lot of Ca hidden in sarcoplasmic reticulum- none in the cytoplasm. 

• thin and thick filament interaction in a mucle
• strong connection
• rearranged and broken during tension

exist for every action potential, get a little bit of tension.

“fast twitch”

• white meat (lil mitochondira)
• little contraction
• fermentation/ glycosis > actic acid > cramp
• holds onto creatinphosphate which can make ATP
• ex) sprints

“slow twitch”

• ·      dark filled with myoglobin
• ·      has mitochondira – cellular respoiration.
• ·      endurance

chemoreceptors

a.   olfaction (smell): smell is 80% of taste

b.   gustation (taste): (be cauious bc taste is combined with smell)

c.    specific to a single molecule

electromagnetic receptors *

a.   photo receptors

b.   magnetic field – tells bird the direction to fly

c.    electric field

nocireceptor

pain (impt sense for protection so you know what to avoid

·      Found in: dendrites of some sensory neurons

·      Three types:

o   1) mechanical – respond to cuts, crushing

o   2) thermal – extreme temp

o   3) other – certain chemicals

o   can act like cytoskeleton - in cilia, actin is holding it up.

o   actin reacts with myosin to give movement and force( even amoeba) 

basilar membrane 

·      looks like a harp

·      longest note plays the lowest

·      high note plats at the shortest 

·     can be stiff or flexible

• aka single neuron. 
• Functional value of the muscle
• generate different levels of force by varying different numbers of motor units. 
• single motor neuron can talk to 10 or 1000 cells. When neuron contracts, all the connected cells will have to contract at the same time. 
• every muscle cell is being told to contract by ONE motor neuron. But a single motor neuron will talk to X number of muscle cell. 

• down the thick only
• holds the whole filaments together

• used to generate force but only in one direction.
• muscles are crystal protein.
•    were called fibers.

• ·      muscles are single cells but are massive.

  syncytial= lots of individual nuclei. 

• extension on receptors 
• composed of microvilli
• mechanoreceptor 
• look like organ pipes > more you hit, bigger sound
• which way you bend hair gives you hyper/depolarization. 
• do not repair well

Action potential spreads on surface > down the T tubua > triggers Ca channel that SR has > myofibers filled with CA > filaments slide over each other> shortening of fiber > z line gets closer during contraction> I and H zone disappears bc I slides past Hzone (A band never shortens) > SR eats up the Ca > repeat 

muscle contracts as long as action potential / Ca is there >twitch 

Overall: Myosin (thick) holds towards it core, grab, pull, release, and reset and regrabbing and et

·      those that can to carry out single tasks. Specialized for single stimuli. 

Taste cells > taste bud > papillae

·      2-250 papillae in a taste bud 

Vomero nasal organ VNO *

detect pheromones

• neurons but release neurotransmitter.
• High turnover rate- replaceable cells
• work with neurons and then tell CNS to tell if it’s sweet, sour or etc. 

·      rods and cone point back towards the brain.

·      do not have action potential

·      every rod and cone are not created equally

·      only place we see equal rod and cone pathway is fovea- every one of these cones have it’s own ganglion

·     

Olfactory nerve*

§  goes to limbic system first > smell has emotional response

 osmoreceptor *

a.   finds osmolarity (K, Na, and etc)

   thermoreceptor:*

a.   if extreme, linked to pain as well

b.   hot receptor

c.    cold receptor

                                 i.     ex) mint gives a sensation of coldness.  

Chordates:

•  phylum 
• precedes vertebrates.

bradykinin*

§  primary signal for pain:

Any cell that is damaged will cause bradykinin to be released

Gustation*

itch*

a.   lowest in transmission

b.   most debilitating when it goes wrong. Ex) scratch through your brain. 

limbic system*

seat of our emotion 

Sensory receptors: *

Can be specialized neuron endings or specialized cells in close contact with neurons  

tendons*

connect muscles to the bone

Sense organs: *

Sensory receptors + other types of cells

Ex) eyes, ears, nose 

encapsulated or naked 

encapsulated by connective tissue/ sheath

o   because it’s encapsulated, it makes it a bit harder to distort

§  meissner’s corpuscle

§  pacinian corpuslce

naked. “naked” dendrites are sitting there without anything surrounding it.

o   merkel’s disc (touch)

o   root hair plexus (touch)

o   nociceptors (pain)

o   thermoreceptors

§  in every tissue of the body except the CNS. (which is why you can poke your brain and not feel pain)

Bone:

1.   storage for calcium and phosphate and fat (yellow marrow).

·      “calcium phosphate salt” = hydroxyapatite

o   precipitates in the matrix.. gives mineral like quality

o   reservoir for calcium

o   calcium essential for muscular and neuronal system.

2. protection

3. support

4. movement (in conjunction with muscles)

5. stem cell – produce blood and immune system

·      red marrow- where our blood and immune system comes from

Cells Resting Potential vs Receptor Potential:  *

Receptor Cells:

1. ·      do NOT have action potential
2. ·      do not have threshold.
3. ·      graded potential (more or less change in the membrane potential)   ex) -20 to -40 to -60
4. ·      but will be eventually turned into action potential. 

Types of sensory receptors by location of stimuli*:

Exteroceptors

Interoceptors

receptors that constant (tonic/continuous): *

·      light ex) vision

·      pain

Types of sensory receptors by type of energy converted*

1. Thermo (pain, hold, cold)
2. Electro (photo, magnetic, electric)
3. Noci (pain)
4. Mecano (propriorreception) 
5. Chemo (olfaction, gustation, specific)
6. itch 
7. osmo (osmolarity - K, Na)

Smell and taste transduction difference? *

Smell does not activate protein kinase  and does not close K channel BUT opens NA channel 

receptors that are adaptive: *

·      smell

o   signal dissipates 

:sensation in the tongue:

 *

1.   salt = Na+

2.   sour = H+ (acid)

3, 4, 5 work under G protein:

3.   sweet= simple sugars, certain amino acids

4.   bitter = alkaloid (caffeine, nicotine, strychnine= all neurotoxin)

5.   umami = particular form of acid: glutamate (MSG). ex) what gives the broth it’s richness.

6.   “fat” = proven in rats, but not in humans yet

___________ supply rods and cones with retinal*

What happens to a photon of light when it hits our eyes?

humans vs cats *

·      human: choroid absorbs light

·      tapetum reflective: certain species have it so it’s reflective and not choroid. At night, when animals eyes’ flash.

o   Pro: twice the chance to catch

o   con: resolution disappears. 

*what energy/wavelength does rod/cone absorb?  

o   matters depending on the type of protein that retinol is holding on it.  

ex) o   1 -2 percent of ganglion cells do not communicate info for vision. Have version of protein called  melanopsin and sent to pineal gland ( helps us understand our circadian system)

§  these are not wavelength sensitive.

§  can be activated by any wavelength

in the brain- not the eye

·      ex) green color in one eye; red color in one eye = interpret color as yellow in both eyes.  

hearing

balance

position within a gravitational field

acceleration / deacceleration 

*Where does sensation take place?

Takes place in the brain. 

*What are the two types of sensory reception mechanism? 

1. stretch receptors:

Stronger stretch > larger receptor potential > high frequency of action potential

·      bend over > dendrites (on the muscle) and muscle stretches > produce stretch receptor potential > trigger action potential in stretch receptor

2. hair receptors:

whether there is fluid or not, hair cells release neurotransmitter and send action potential along the axon.

Responds to the direction of motion and strength and speed.

·      hairs of hair cells + no fluid movement > release neurotransmitter > signal down axon = 0 receptor potential; but several action potential

·      hairs of hair cells + fluid movement to one direction > release MORE neurotransmitter  > depolarize hair cell > increase action potential frequency  = receptor potential + action potential

·      hairs of hair cells + fluid movement in other direction > release LESS neurotransmitter  > hyperpolarize hair cell > decrease action potential frequency  = negative receptor potential + action potential

*Explain the difference in receptor potential and action potential graph of Mv vs time? 

Action potential: sharp peaks

Receptor potential: rise > levels off > decline 

*What is sensation depended on? 

Sensory receptor + brain

Depends on transmission of a coded message

Depends on which interneuron receives the message. 

*Do all sensory messages give rise to sensations? 

No. 

*What are the types of mechano receptors? 

Gravity receptors: statocysts

Hair cells

Lateral Line

Vestibular apparatus

Auditory receptors

Proprioceptors:

Touch Receptors: 

*How does the brain interpret sensations? 

Converts sensation to perceptions by comparing present with past memories.

*Why might the “coded messages” created by sensory neurons be different? 

1. total number of sensory neurons transmitting signals

2. specific neurons transmitting action potential

3. total number of action potential transmitted by a neuron

3. frequency of the action potential transmitted by a given fiber 

cis and trans

conversion happens with absorption of photon

*Are all action potential the same? 

Yes, qualitatively the same. 

*Where does sensory integration happen and begin? 

begin at receptor >integrated by summation

occurs in spinal cord and some parts of brain

*When unstimualted, what potential is the sensory at? 

It maintains a resting potential- charge diff btw inside and outside cell

*How do sensory receptors adapt to stimuli?

1. Maintain - If stimulus continues at SAME intensity, sensory adapatation takes into affect and do not continue to respond.

2. Slowly- trigger action potential even with stimulus persisting ex) pain or cold

3. Rapidly – ex) smell 

*What is responsible for the sense of smell? 

Olfactory epithelium 

*How do you sense taste? 

*What does color vision depend on? 

Three types of cone – red, green, blue 

*What kind of neuron are sensory neurons?

Aka afferent neurons – transmit info from receptor to CNS

*Where does integration of visual information begin?

*Overall pathway for Sensory System: 

Stimulus (ex: light) accepted by sensory receptors > receptor tranduces/converts stimulus energy into electrical energy via neurotransmitter or > create receptor potential potential (de/hyper-polarized) in receptor > depolarize > action potential generated in sensory neuron and sent down axon>  signals transmitted to CNS > integrated by brain > giving perception

*Detailed pathway for sensory system:

Stimulus (ex: light) accepted by sensory receptors > receptor tranduces/converts stimulus energy into electrical energy via neurotransmitter or current down the axon > integrated by summation > create receptor potential (de/hyper-polarized) in receptor > depolarize > action potential generated in sensory neuron (coded messages) and sent down axon>  signals transmitted to CNS > integrated by brain > decoded by brain > select/interprete/organize by brain > converts to perception by comparing present memories with past. 

·      fibers > fibrils (striated) > filaments 

Signal through sensory neuron > release neurotransmitter glutamate and neuropeptide substance P > interneuron transmits to spinal cord > thalamus > impulse sent to parietal lobes and limbic system > cerebrum > pain perception + emotions attached

Overall:

Light > cornea > aqueous fluid > lens> vitreous body > image forms on photoreceptor cells in retina > singal bipolar cells > signal ganglion cells > optic nerves transmit signals to thalamus > integrate by visual areas of cerebral cortex

when dark, receptor is at the MOST depolarized state.

·      release inhibitory neurotransmitter the most 

when it gets lighter, cell gets more and more negative.

·      remove neurotransmitter > activate bipolar cell > activate gangilion > action potential

Going from dark to light :

In the dark intiailly  cGMP > allow Na to come into the rod cell > depolarize > release neurotransmitter glutatmate > glutamate hyperpolarize bipolar cell so does not transmit info.

Light on (Opsin + cis retinal) = rhodopsin > light adaptation > rhodopsin broken down to trans retainal + opsin >optin activates G protein > trans retainal binds with transducin (a G protein) > activates phoshodiesterase > esterase turn cGMP to GMP > decrease cGMP > Na channel close > cells becomes more negative > hyperpolarize > release less glutamate > depolarize bipolar cell > increase neurotransmitter release > stimulate ganglion cell 

Going from light to dark :

Dark adaptation > enzymes convert retinal back to cis form > recombines cis with opsin = rhodopsin

Taste receptors detect chemical substance > signal tranduction pathway.

G protein is activated > activate Adenylyl cyclase > ATP turns to cAMP > protein kinase activated > close K channel > depolarize > opens Ca channels and Ca comes into the cell > increase Ca > synaptic vesicles to release neurotransmitter >  action potential in sensory neuron

Odortant binds with receptor cell that is on the cilia covered in mucus> reaches the olfactory bulb > signal transduction pathway

G protein is activated > activate  Adenylyl cyclase > ATP turns to cAMP > protein kinase activated >OPEN NA channel > depolarize > action potential in sensory neuron to brain 

• brain infers pitch from the type of hair cells that are stimulated. - where the vibration starts on the basilar membrane determines pitch
• high frequency of sound waves >high pitch> hair cells near base of cochlea will be stimulated
• low frequency of sound waves >low pitch> hair cells near apex of cochlea will be stimulated

*molecular mechanism that takes place to become more negative when light shines in? 

transducin – they are crucial for amplication

at rest: 

actin can't interact bc trpomyson is blocking actin

myosin head holds onto ADP and Pi at rest.

head is at “rest” in the cocked position.  

add Calicium > trpomyosin moves > actin binding site is visible > head forms a cross bridge > triggers release of pi and ADP > powerstroke

add ATP > release head from cross bridge

·      ALOT OF sharing- a lot of things pulling at once.

·      not synchronous.

·      a lot of hands pulling on the thin filament. As long as their pulling, it’s constant.

1.   hydrostatic – water insoluble membrane that allows muscle contraction to squirt water out ex) water balloon

2.   exoskeleton – great for protection but not great for growth.

a.   ex) chitan, calcium carbonate

b.   ex) soft shell crab

3.   endoskeleton – skeleton that grows along with us 

Sound waves > external auditory canal> tympanic membrane vibrates > malleus, incus and stapes vibrates and amplifies > oval window vibrates (making round window bludge also)> vibrates tympanic canal fluid > vibrate basilar membrane > hair cells of organ of Corti rub on tectorial membrane > ion channels in hair cells open > Ca (or K?) ion move into hair cell > glutamate released > glutatmate binds to receptors> depolarize hair cells > action potential sent to cochlear nerve neuron

Lecture: ??

level of K in cochlear duct is really high.

Eq K = 0Mv. (outside is 0 and -70 inside)

for rest of body, -5mV.

so if youopen a K channel, polarization is driving by K, not Na.

hearing > open K channel, it depolarizes. 

 DIFFERENT from all other neurons bc…

o   1. Dark current: Ion channel is normaly open > depolarized and constantly release neurotransmitter

o   2. DO NOT produce action potential (except ganglion cell photoreceptor)

o   3. Release of neurotransmitter is graded 

how much basilar membrane vibrates determine volume. 

more intensity > more frequency

axial vs appendicular skeleton 

• appendicular: 126 bones
• axial: 80 bones
• 206 bones make up a human skeleton (do not have to know the names of the bone)

·      cross bridge is formed, can’t be broken and now can’t be released so muscle locks.: rigormortis. 

types of muscle 

muscles are always paired antagonistically.

1. flexor: if it's designed to make it more acute

2. extensor: opposite of flexor

all muscles have to be attached to skeleton in minimum of 2 places.

origin and insertion:

·      attachment of muscle to bone.

·      insertion: where it undergoes motion

·      origin: least movable. 

How is bone developed? 

bone undergoes endochondrial ossification. (except: skull is produced a little differently) 

1. starts with cartilage. Cartilage has no blood system.

2. as we developed, cartilage dies and blood system invades

3. for bone to continue to grow, need to maintain active cartilage growth.

this happens right at the end at growth plates. 

as cartilage grows, you still continue to grow.

4. bones grow bc of sex and growth hormone.

growth stops when growth plates disappear. 

ex) adult have no growth plates. it’s just hollow. Internally filled with marrow and blood.

·      atp is not needed for the direct generation of force but for the separateion of cross bridge. 

what makes and digests bone? 

osteoblasts = makes bone

·      if Ca high > hormone calcitonin (made by thyroid) stimulates osteoblasts

osteoclasts = digests bone

·      if Ca low > hormone PTH (parathyroid) activates osteoclasts.

·      if really low, Ca will be pulled from the bone.

No part of your skeleton that is older than 10 years.

prefix

"sarco"

"chondria"

chondria = cartilidge. 

sarco= pieces of muscles

external Ca > trigger release neurotransmitter > action potential > release internal store of Ca (skeletal muscle don't need Ca bc it has everything it needs) > power stroke > until Ca gets eaten up by SR

Ca

the conversion of external stimulus to an internal signal in the form of an action potential; a series of changes in cellular proteins that converts an extracellular chemical signal to a specific intracellular response

sending changing rates of AP signals to specific portions of the brain

light-sensitive membrane-bound G protein-coupled receptors found in photoreceptor cells of the retina; conversion of photon of light into electrochemical signal

an actin-binding protein that regulates actin mechanics for muscle contraction; associated with actin in muscle fibers and regulate muscle contraction by regulating the binding of myosin:

resting muscle-tropomyosin overlays the myosin binding sites on actin (a single tropomyosin molecule spans 7 actin subunits) and is "locked" down in this position by troponin

-->calcium binds to troponin and "unlocks" tropomyosin from actin-->myosin heads access the binding sites on actin initiating muscle shortening and contraction-->once calcium is pumped out of the cytoplasm and calcium levels return to normal-->tropomyosin again binds to actin, preventing myosin from binding

a sensory receptor that responds to mechanical pressure or distortion:

four main types: Pacinian corpuscles, Meissner's corpuscles, Merkel's discs, and Ruffini corpuscles

 nerve endings in the skin, responsible for sensitivity to pain and pressure;

detects deep pressure and rapid vibrations, phasic (rapidly adapting), deep layer, capsulated, oval shaped, respond to higher frequency vibrations; any deformation causes action potentials to be generated, by opening pressure-sensitive sodium ion channels in the axon membrane

-->sodium ions influx in, creating a receptor potential

the transparent front part of the eye that covers the iris, pupil, and anterior chamber; refracts light, contributes to most of the eye's focusing power but is fixed; unmyelinated nerve endings sensitive to touch, temperature and chemicals-->a touch causes an involuntary reflex to close the eyelid; transparency, avascularity (no blood vessels, receives nutrients via diffusion from the air-oxygen); contains albumin-most abundant soluble protein

the opening in the center of the iris that allows light to enter the retina, its size determines the amount of light that enters the eye

• specialized neurons or epithelial cells that exist singly or in groups with other cell types within sensory organs (like the eye)
• function: to convert the energy of stimuli into changes in membrane potentials, then transmit signals to the nervous system
• can detect the smallest physical unit of stimulus possible
• 5 categories based on the type of energy they detect:
  • mechanoreceptors
  • nociceptors
    
  • chemoreceptors
  • electromagnetic recptors
  • thermoreceptor
    

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either a general receptor that transmits information about the total solute [ ] in a solution or a specific receptor that responds to individual kinds of molecules.

Examples:

• osmoreceptors – general receptors  in the brain, detect changes in solute [ ] of the blood and stimulate thirst when osmolarity increases 
• gustatory receptor: specific taste receptors that respond to categories of related chemicals

specific taste receptors that respond to categories of related chemicals

"tastes" that make up gustation:

·      salty - stimulus is Na

·      sour - stimulus is H (acid)

·      sweet - stimulus is simple sugars, amino acids

·      bitter - alkaloids (neurotoxins: caffeine, nicotine, strychnine)

·      umami  - glutamate (particular form of amino acid)

·     fat

receptors that detect electromagnetic energy such as visible light, electricity, and magnetism

• pain receptors. naked dendrites in the epidermis of the skin.
  
• different groups of pain receptors respond to heat, pressure, chemicals etc.
• every tissue in the body except brain has nociceptors 
  
• bradykinen- a chemical produced whenever any cell damage occurs. it binds to the nociceptors and serves as the primary signal for pain.

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• one of two openings into the cochlea of the inner ear, situated behind the oval window
• closed off from the middle ear by the round window membrane which vibrates with opposite phase to vibrations entering the cochlea through the oval window 
• stapes bone vibrates against the oval window -> wave of pressure moves  fluid in choclea into vestibular canal -> wave dissipates as it strikes the round window -> hair cells of the basilar membrane  stimulated ->  audation occurs

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• a chamber in the vestibule behind the oval window with hair cells sensitive to balance and body position
• along with the utricle, tells the brain which way is up and informs it of the body’s position in space

• an extracellular fluid in found in 2 of the 3 cochlear compartments (the tympanic canal and the vestibular canal).
• ionic composition is comparable to that of plasma and cerebrospinal fluid
• major ion is Na⁺

• tube that connects the pharynx to the middle ear
• equalizes pressure between the middle ear and the atmosphere (by allowing you to “pop” your ear)

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aka: involuntary or visceral muscle

• spindle shaped cells
• lacks the striations of skeletal & cardiac muscle b/c actin & myosin filaments not  regularly arrayed along length of the cell
• compared to striated muscles - contractions are slow, can stay contracted longer, and can contract over greater lengths
• no T tubule system
• no well-developed sarcoplasmic reticulum
  

• <!-- /* Font Definitions */ @font-face {font-family:"Times New Roman"; panose-1:0 2 2 6 3 5 4 5 2 3; mso-font-charset:0; mso-generic-font-family:auto; mso-font-pitch:variable; mso-font-signature:50331648 0 0 0 1 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0in; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman";} table.MsoNormalTable {mso-style-parent:""; font-size:10.0pt; font-family:"Times New Roman";} @page Section1 {size:8.5in 11.0in; margin:1.0in 1.25in 1.0in 1.25in; mso-header-margin:.5in; mso-footer-margin:.5in; mso-paper-source:0;} div.Section1 {page:Section1;} --> a specialized endoplasmic reticulum that regulates the calcium [ ] in the cytosol
• membrane of sarcoplasmic reticulum actively transports calcium from the cytosol into the interior of the reticulum
  

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• an oxygen-storing pigmented protein in muscle cells
• binds oxygen more tightly than hemoglobin 
• the brownish-red pigmented protein in the dark meat of poultry and fish

• stretch receptor. an interoreceptor (detects stimuli within the body) stimulated by mechanical distortion
•   <!-- /* Font Definitions */ @font-face {font-family:"Times New Roman"; panose-1:0 2 2 6 3 5 4 5 2 3; mso-font-charset:0; mso-generic-font-family:auto; mso-font-pitch:variable; mso-font-signature:50331648 0 0 0 1 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0in; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman";} table.MsoNormalTable {mso-style-parent:""; font-size:10.0pt; font-family:"Times New Roman";} @page Section1 {size:8.5in 11.0in; margin:1.0in 1.25in 1.0in 1.25in; mso-header-margin:.5in; mso-footer-margin:.5in; mso-paper-source:0;} div.Section1 {page:Section1;} -->

   

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(vs origin)

• a single quick contraction in respone to a single breif electrical stimulus
• fast and slow fibers have different duration of twitches
  • fast twitch - for short, rapid, powerful contractions
  • slow twitch- can sustain long contractions. less sarcolpasmic reticulum, slower calcium pumps, (so Ca remains in the cytosol longer), many mitochondria, rich blood supply, and lots of myoglobin

• calcium carbonate earstones embedded in a gelatinous cupula covering hair cells on sterocilia in saccule and utricle of inner ear
• sense gravity

the addition of individual twitch contractions to increase the intensity of overall muscle contraction. This can be achieved in two ways:

(1) by increasing the number and size of contractile units simultaneously, called multiple fiber summation, and

(2) by increasing the frequency at which action potentials are sent to muscle fibers, called frequency summation.

• cutaneous receptors that have the ability to detect low-frequency vibrations
• found in the conjunctiva of the eye, in the mucous membrane of the lips and tongue and in the epineurium of nerve trunks

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• a globular protein that links into chains, 2 of which twist helically about each other
  
• the subunit of two types of filaments in muscle and other contractile elements in cells: microfilaments and thin filaments

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