Find study materials for any course. Check these out:
Browse by school
Make your own
To login with Google, please enable popups
To login with Google, please enable popups
Don’t have an account?
To signup with Google, please enable popups
To signup with Google, please enable popups
Sign up withor
What is the difference between an ionotropic and metabotropic receptor?
· Ionotropic: directly affects a cell by opening ions channels
· Metabotropic: uses primary, secondary, etc messengers to bring about some sort of change in the cell.
Give examples of touch receptors.
· Fast adapting: only respond to novel stimuli (ignore background noise)
· Slow adapting: constantly engaged (ie baroreceptors, proprioceptors)
Where are olfactory receptors found and what type of receptor are they?
· Olfactory receptors are found in the nasal cavity and are a G-protein coupled receptor. Golf activates cAMP as a second messenger and causes ion channels to open (metabotropic)
What are papillae and where are they found on the tongue? Which ones contain taste buds?
· Papillae are structures that contain taste buds (modified epithelial cells)
· They are found on the back of the tongue
· Contain taste buds:
o Fungiform papillae
o Foliate papillae
o Circumvallate papillae
What are the five types of taste receptors? What types of chemicals do they respond to? What types of receptors do each of these use?
Salty- respond to Na ions, moves in through leak Na channels causing depolarization from Na ions Sweet- GCPR, ATP as messenger, can lead to cell depolarization or activation of calcium as second messenger Bitter- GCPR, ATP as messenger, can lead to cell depolarization or activation of calcium as second messenger Sour- respond to H ions, cause K ion channels to close, cell depolarization Umami- GCPR, ATP as msgr, can lead to cell depol or activation of calcium as second messenger
What is gustducin? How is it involved in sensory signaling?
· Gustducin is a g protein that plays a large role in the transduction of bitter, sweet and umami stimuli
Why can’t you taste as well with a dry mouth or smell as well when it is cold outside?
· Because the receptors are dependent on the chemical activators being dissolved in an aqueous solution
What is lacrimation? What division of the ANS stimulates it?
· Excretion of tears, stimulated by parasympathetic nervous system
What do the extrinsic eye muscles do?
· Direct one’s gaze, controlled by cranial nerves
What is the iris? What does it have to do with the pupil? During what activities is the pupil dilated? Constricted?
· Iris is the muscle that surrounds the pupil (opening) and is responsible for the amount of light entering the eye (size of the pupil)
· The pupil is dilated when there is dim light or you are looking at something far away from you, when something is appealing or requires problem solving
· The pupil is constricted when there is bright light or you are looking at something close to you
What does it mean that light is refracted? What structure in the eye is responsible for most of light refraction?
· Light is refracted since it passes through the convex lens of the eye and the light rays converge and subsequently focus on the back of the eye (retina).
What is accommodation and how does this occur?
· Accomodation is the lengthening or condensing (straightening vs relaxing) of the lens. This occurs as a result of the relaxation or contraction of the ciliary muscle. If relaxed, the ligaments attached to the lens are pulled taught and there is lengthening of the lens. If the ciliary muscle is contracted, the ligaments are loosened and the lens is shortened.
What is the focal length of light? What happens if the focal length falls beyond the retina? What happens if it falls short of the retina?
· Focal length of light: the length it takes to converge into one central location
· Falls beyond retina: Far sighted
· Falls short of retina: close sighted
What are the 3 main cell layers in the retina?
· Photoreceptors to Bipolar cells to Retinal ganglion cells
What is the fovea centralis?
· Area of highest visual acuity, where light is focused to get best perception of image
What is the optic disc?
· Optic disc is where the ganglion axons form the optic nerve and signal travels away from eye, lacks photoreceptors
What forms the optic nerve (CN II)?
· The optic cranial nerve is formed by the axons of the ganglia
What is the difference between rods & cones – in terms of location/distribution, sensitivity, color vision, and visual acuity? Which of these converge, and which do not? How does convergence affect image quality and sensitivity?
· Rods: Dim light for night vision, absorb all wavelengths of visible light, perceived input is in gray tones, area of rods activates one ganglion cell (convergence), this results in a fuzzy image
· Cones: Color and needs stronger light to activate them, each individual one absorbs a specific wavelength of light, one cone activates one ganglion cell (no convergence)
What is a photopigment and where is it found in the eye?
· Stack of disk-like infoldings that change shape as they absorb light
· Found at base of rods and cones
What is photobleaching? What happens if a photoreceptor is bleached?
• Constant exposure to one type of either rod/cone
• When environment is changed, have trouble with seeing that color/rod/cone use
What is retinal and what role does it have in phototransduction? What form is it in during the dark? During the light?
· Retinal is a light absorbing molecule that when combined with opsin forms rhodopsin (visual pigment)
· When it is stimulated it begins electrical impulses in the optic nerve
· Form during dark: inactivated form (11-cis retinal) and bound to opsin (rhodopsin)
· Form during light: activated form (all-trans retinal), released from opsin and free
What is opsin and what role does it have in phototransduction?
· Opsins are a group of light-sensitive G protein-coupled receptors found in photoreceptor cells of the retina. Opsins are involved in vision, mediating the conversion of a photon of light into an electrochemical signal.
What is the dark current? What causes it?
· “Dark current” is the inward sodium current carried by cGMP-gated sodium channels. It is responsible for depolarizing the cell to around -40 mV. It is caused by the absence of light.
What is the membrane potential in the photoreceptor in the dark? What is it after light activates it?
· -40mV in the dark
· After light activates it, it is hyperpolarized to -70mV
What is transducin?
· Transducin is a g protein that is activated by opsin after being bleached by light. The activation of transducin initiates a breakdown in cGMP, thereby closing sodium channels and leading to the hyperpolarization of the photoreceptor
What is the role of the RPE (retinal pigmented epithelium)?
· RPE shields the retina from excess incoming light. It supplies omega-3 fatty acids and glucose, the former for building photoreceptive membranes, the latter for energy. Also partake in phagocytosis of old discs and photoreceptors in self-contained immune system.
What state are sodium and potassium channels in photoreceptors during the dark?
· Both are open
What ions move (in photoreceptors in the dark) and which direction do they go?
· Sodium ions move into the cell and potassium ions move out of the cell
What state are sodium and potassium channels in photoreceptors after light stimulation? What ions move and which direction do they go (in photoreceptors in the light)?
· Sodium channels are closed and potassium channels remain open. Potassium continues to move out of the cell causing hyperpolarization
What neurotransmitter is released from the photoreceptors? What effect does it have on bipolar cells?
Glutamate is released from the photoreceptors and it inhibits on center bipolar cells and excites off center bipolar cells.
In the dark, PRs are DEPOLARIZED and constantly release glutamate. This inhibits on center (hyperpolarizes them) and activates off center.
In the light, PRs are hyperpolarized and glutamate is not released. This causes the on center bipolar cell to become depolarized and send signal to ganglion cell.
What is light adaptation?
· Dramatic decreases in retinal sensitivity – rod function is lost
· Switching from the rod to the cone system – visual acuity is gained
Where else (besides the visual cortex) do small subsets of visual fibers go and what do they do?
· A small subset of visual fibers contain (melanopsin/circadian pigment) and go to the suprachiasmatic nucleus (SCN), a tiny region located in the hypothalamus, situated directly above the optic chiasm. It is responsible for controlling circadian rhythms.
How do we achieve depth perception?
· We achieve depth perception by both eyes viewing the same image from slightly different angles
What is the LGN?
· The LGN is the primary relay center for visual information received from the retina of the eye. The LGN is found inside the thalamus of the brain
Where other than the visual (striate) cortex does visual information go? What is this information used for?
· Hypothalamus: SCN and is responsible for circadian rhythm
· Thalamus: Through the LGN before being sent to the visual cortex
· Other optic tract fibers end in superior colliculi (initiating visual reflexes)
What is a negative afterimage? Why does that occur?
· You use up all of one kind of cone by looking at an image for a while and then when looking at a white screen see color other than that cone
What do ceruminous glands produce, and what is the function of this substance?
· Ceruminous glands produce cerumen, or earwax. Cerumen keeps the eardrum pliable, lubricates and cleans the external auditory canal, waterproofs the canal, kills bacteria, and serves as a barrier to trap foreign particles (dust, fungal spores, etc.) by coating the guard hairs of the ear, making them sticky.
How does sound reach the inner ear?
· Tympanic membrane (ear drum) à Malleus à Incus à Stapes à Oval window
What are the stapedius and tensor tympani muscles, and what do they do?
· Muscles attached to the stapes and malleus. Help with “attenuation reflex” and will contract when predicting a loud noise. The contraction helps dampen the amount the bones move
How is pressure equalized in the middle ear? (as occurs during altitude changes, e.g.)
· By letting air enter the Eustachian tubes
What is the tympanic membrane and what does it do?
· The tympanic membrane is also sometimes called the eardrum and it takes vibrations from ossicles and caused the movement of fluid inside the cochlea.
What is the composition of perilymph and where do you find it?
· Perilymph is inside the inner ear bone labyrinth and is similar to extracellular fluid. Has high concentration of Na and low concentration of K
What is the composition of endolymph and where do you find it?
· Major component of membranous labyrinth – high K+, low Na+
How does a hair cell work? What causes depolarization and what causes hyperpolarization? What is an MET protein? What are tip link proteins?
· K+ channels (mechano electrical transducers- MET protein) in tip of hairs connect via filament to adjacent hairs
· Bending hair toward kinocilium opens K+ channel, depolarizing cell bc endolymph is high in K+
· Bending hair away from kinocilium closes channel and hyperpolarizes cell
· Tip linked proteins connect the stereocilia and the kinocilia
How are kinocilia different from stereocilia in terms of function?
· Kinocilia are the largest and only true cilium in hair cells (of semicircular canals)
· Stereocilia are really microvilli and linked to the kinocilium via tip linked proteins
What structures are associated with linear (static) equilibrium and which with dynamic equilibrium?
What is the organ of Corti and where do you find it?
· The organ of Corti is rests on basilar membrane, has inner hair cells on one row with outer hair cells - 3-4 rows, tectorial membrane rests on tips of hairs.
· Found in cochlea between cochlear duct and scala tympani of cochlea
What is conduction deafness? Sensorineural deafness?
· Conductive hearing loss: sound conduction hampered (e.g., impacted earwax, perforated eardrum, osteosclerosis of the ossicles)
· Sensorineural deafness damage to the neural structures (hair cell damage)
What are the otolithic membrane, cupula, and tectorial membrane? What role do they play in hair cell activation, and with what structure is each associated?
· Otolithic membrane: Covers hair cells and is btwn hair cells and endolymph, has crystals inside that act as gravity receptors
· Cupula: gelatinous covering of crista (with hair cells). Movement of endolymph fluid deflects the cupula and causes activation of hair cells (just like hearing) à in semicircular canals
· Tectorial membrane: Covers organ of corti and rests on tops of hair cells
What is the stria vascularis and what does it do?
· The stria vascularis is vascular & secretes endolymph, located in the cochlear duct (scala media) which is located between the vestibular membrane of the scala vestibuli and the basilar membrane of the scala tympani.
How are pitch and loudness of sound transmitted in sound waves?
· Pitch= different frequencies
· Loudness= amplitude of sound waves
How do the ears adjust sensitivity for louder and softer sounds?
· Contraction or relaxation of stapedius and tensor tympani muscles
What are the basilar and tectorial membranes and what roles do they play in detection of sound waves?
· Basilar membrane vibrates, causing the tectorial membrane to move. The tectorial membrane rests on the tips of the hair cells. By the tectorial membrane moving, the MET hair cells are activated and the mechanical stimulus is turned into an electrical stimulus.
What is the difference between the origin and insertion of a muscle?
· Origin: an immoveable attachment
· Insertion: a moveable attachment
What is the power stroke?
· Power stroke initiate by rise in CA levels à Ca binds to troponin à Troponin and Ca complex pulls tropomyosin away from the G-actin binding site à myosin binds to this site, P is released from the myosin head. This initiates the power stroke, which is when the myosin head pivots and pushes the actin filaments passed it
What is a sarcomere? Know the different bands & zones, etc, discussed in class. Which of these shorten during a contraction?
A sarcomere includes one end of the thin filaments (z disk), the thin and thick filaments, the m line, the other side of the end line through to the next z disk.
A band is the myosin and actin overlap
I band is actin only (shortens during contraction)
H zone is myosin only with no overlap (shortens during contraction)
Z disk is the connection of 2 sides of thin (actin) filaments
What is the thin filament made of? The thick filament? How do they interact during contraction?
· The thin filament is made of actin and troponin
· The thick filament is made of myosin
· Move past eachother during contraction
What is the neuromuscular junction (aka: myoneural junction)? What NT is released here?
· The neuromuscular junction is the synapse between a motor neuron and the muscle fiber is activates
· ACh is released at this junction
What type of receptors are found at the motor end plate? What causes them to open, and what happens when they do?
· The motor end plate has ionotropic receptors, caused to open when ACh binds to them
· Ionotropic channels open allowing sodium influx and potassium efflux
· Sodium moves in faster than potassium moves out, causes depolarization
How does the depolarization from the motor neuron spread throughout the skeletal muscle cell?
· The depolarization spreads along the membrane, down to the t-tubule until it finally gets to the DHP receptor
What role does ATP play in skeletal muscle contraction?
· Attaches to myosin head where it causes the release of myosin head form actin-binding site. ATPase converts to ADP and P and myosin head reattaches at 90 degrees relative to the two filaments. P is given off as the power stroke occurs.
What is the DHP receptor and where is this found? How does this differ from the ryanodine receptor? How are these coupled with the release of calcium?
· The DHP receptor is found on the membrane by the t-tubule.
· It is different from the ryanodine receptor because
· DHP receptor is linked to the sarcoplasmic reticulum and, when activation reaches DHP and changes conformation, triggers Ca2+ release from sarcoplasmic reticulum into rest of cell
Where is calcium stored in skeletal muscle, and what kind of receptor triggers its release? What is the role of calcium in skeletal muscle contraction?
· Calcium is stored in the sarcoplasmic reticulum
· DHP triggers its release
· Calcium binds to troponin on the actin filaments and opens actin binding site so that myosin head can execute power stroke
What is tetani and how is it produced?
· Tetani occurs when the same muscle cell is stimulated repeatedly by either the same motor neuron or multiple motor neurons. Get up to maximum tension and smoothly sustain it until fatigue sets in
What are some of the differences between a slow-twitch and fast-twitch fiber? Which type would you expect a sprinter to have more of? A long-distance runner?
Fast twitch, Usually appear white, Due to less blood vessels throughout to supply, Have fast myosin ATPase, More in sprinters
Slow twitch, Darker because more blood vessels supplying them, Have myoglobin- oxygen binding protein that facilitates transfer of oxygen, also gives red color to muscle, Have slow myosin ATPase, Slower to develop tension, but also slower to fatigue, More in long-distance runners
What is phosphocreatine and what is it used for?
· Helps provide ATP at the beginning of working out
· This ATP is needed for myosin head (contraction), SERCA (relaxation), and Na/K ATPase to restore ionic concentrations
What is muscle fatigue and what are some of its causes?
Fatigue inability of muscle to reach maximal tension even with continued stimuli
Tons of theories, not linked to ATP stores, though
Possible theories are: depletion of ACh, increase in inorganic phosphate bc of inability of myosin head to release inorganic phosphate, altered calcium cells, the amount of calcium is proportional to amount of cross bridges formed, altered potassium levels that messes with pH of fibers
Where in the body might you find smooth muscle?
· Intestines, veins, reproductive system, urinary system
How are the actin & myosin filaments different in smooth muscle (vs skeletal muscle)?
· Longer actin & myosin filaments
· Actin: Myosin ratio higher
· Initiation of movement is myosin dependent, not actin
What is the difference between single-unit and multi-unit smooth muscle?
· Single unit have lots of gap junctions and can affect multiple when only one is stimulated
· Multi unit have very few gap junctions and must be stimulate independently
What is the role of calcium in smooth muscle contraction and where does it come from?
· Calcium enters cell after stretch activated channels kick in and allow the ions to enter the cell from the extracellular environment
· This causes calcium to be released by the sarcoplasmic reticulum
What is calmodulin and what does it do?
· Calmodulin is a second messenger? And, once calcium is bound to it, activates myosin light chain kinase
· Calmodulin activates MLCK to initiate response in smooth muscle
What is myosin light chain kinase and what does it do? Why is this important in smooth muscle?
· Myosin light chain kinase is an enzyme that phosphorylates light chains in myosin heads and increases myosin ATPase activity
· This is important in smooth muscle since it enables the myosin cross bridges to move passed actin and create tension
Sign up for free and study better.
Get started today!