Play as Webslides

Ambika K's List: MEDEDU

Maximizing Productivity and Recognition, Part 3: Developing a Research Plan - Science Careers - Biotech, Pharmaceutical, Faculty, Postdoc jobs on Science Careers

sciencecareers.sciencemag.org/...caredit.a0800148 - Preview

MedicalResearch on 2009-11-27
Medical Animation Library

www.pennmedicine.org/...animationplayer - Preview

medvideos on 2009-11-27 and saved by 5 people
Welcome to Wheeless' Textbook of Orthopaedics - Wheeless' Textbook of Orthopaedics

www.wheelessonline.com - Preview

orthopedics on 2009-11-27 and saved by 19 people
Murmurs recognition –part 1 | Vanumu.com

great!

vanumu.com/?p=728 - Preview

cardiovascular clinicalmed starred on 2009-11-23
ECG Learning Center

library.med.utah.edu/...index.html - Preview

ECG on 2009-11-23 and saved by 3 people
ED Primer.pdf (application/pdf Object)

www.saem.org/...ED%20Primer.pdf - Preview

EmergencyMed books on 2009-11-21
Audacity, Part 3: Funding Audacious Science - Science Careers - Biotech, Pharmaceutical, Faculty, Postdoc jobs on Science Careers

"pursue a range of projects with different levels of risk and potential reward and different timetables" -KEEP SIDE PROJECTS.

sciencecareers.sciencemag.org/...caredit.a0900143 - Preview

MedicalResearch audacious on 2009-11-20
- You get hired for the big and bold ideas, but you don't get funded for those
- You get hired for the big and bold ideas, but you don't get funded for those
- 8 more annotations...
- - What you publish is “the advertisement that you're providing to prospective students,” she says. If you aim to nudge your research into a bolder area but all you're publishing is the incremental, interim steps that are being funded, you will attract only students interested in incremental work, not bold ideas
  - Once “you get hired at a place, the biggest expectation is not necessarily to make great discoveries but to get grant funding and to publish a lot of papers
  - “If you start doing the boring stuff and you get all these little, minor reinforcements, like you get a grant, and you get tenure, and you get people patting you on the back and some paper gets accepted in this journal or that journal, you start losing sight of what's really driving the enterprise,” adds Vilayanur Ramachandran, a behavioral neurologist at the University of California, San Diego. “I would never compromise on doing the exciting stuff, and the reason for that is it becomes habit. You get lulled into a false sense of security. You follow the crowd, and you become that.”
  - If you want to get tenure, then you have to get grants–but is strong funding correlated with strong science? Not so much, say our sources, though it depends on the field. “It's a false impression that important discoveries necessarily need a lot of equipment and time and money. In fact, the opposite can be true,” Ramachandran argues. “If you've got a huge grant and 16 postdocs working under you, you become a lab manager. It stifles your creativity.”
  - “What many of us do is, we get the funds for the boring stuff and then do the exciting stuff on the side,” Ramachandran says. “The great thing about NIH is, they don't mind [if you] spend about 10 or 20% of [grant money] on other exciting stuff as long as you tell them it's vaguely related. That's an easy, easy way to deal with that problem.”
  - JHU neuroscientist Solomon Snyder doesn't write about new and exciting research directions in his grant applications. “I write about what we did that was exciting a couple of years ago and that was just published in the last year and say, 'Look, we discovered x, and we're going to do the boring follow-up of x.' ” When the money comes in, he works on what he wants to.
  - “My advice is, if you're selling your wares, which is what you're doing when you're applying for a grant, you try to find out what the customer wants,” Snyder says. “You sell the customer what he wants. And then in real life, you do what you feel like doing.”
  - Importantly, almost all of our sources put forward the concept of portfolio theory: Don't put all your eggs in a high-risk basket, they advise. Instead, pursue a range of projects with different levels of risk and potential reward and different timetables. Also pursue a range of funding sources; instead of relying on a single grant or source, spread the ideas and the applications around. Using strategies like these, you can establish a record of solid, if boring, productivity even as you pursue the big payoff.
Newborn > Abnormal

library.med.utah.edu/...newborn_ab.html - Preview

pediatrics clinicalexped clinicalmed on 2009-11-15
Virtual Anaesthesia Textbook

www.virtual-anaesthesia-textbook.com/index.shtml - Preview

anaesthesia clinicalmed on 2009-11-15 and saved by 5 people
Proteinuria: how to evaluate an important finding. — Cleveland Clinic Journal of Medicine

approach to a patient with proteinuria

www.ccjm.org/...535.full.pdf+html - Preview

med-algorithm on 2009-11-09
Is digoxin a drug of the past? — Cleveland Clinic Journal of Medicine

digoxin MOA diagram
digoxin blocks sodium-pot atpase pump & thus prevents removal of sodium ions from cell . this low ECF sodium inturn stops sodium-calcium exchanger to remove calcium from cell.

www.ccjm.org/...821.full.pdf+html - Preview

pharmacology on 2009-11-09
Skin Lesion Nomenclature Tutorials

www.pediatrics.wisc.edu/...master.html - Preview

clinicalmed dermatology on 2009-11-09
Demonstrations - Thyroid Exam - Physical Diagnosis Skills - University of Washington School of Medicine

depts.washington.edu/...demo.html - Preview

clinicalmed thyroid on 2009-11-09
Neurological Examination

great detail

neuroexam.med.utoronto.ca - Preview

clinicalmed Neurology starred on 2009-11-09
AUDITORY AND VESTIBULAR PATHWAYS

thalamus.wustl.edu/...audvest.html - Preview

ENT clinicalmed on 2009-11-07 and saved by 4 people
- Endolymph is very similar to intracellular
  fluid: it is high in potassium and low in sodium. The ionic composition
  is necessary for vestibular and auditory hair cells to function
  optimally. The space between the membranous and bony labyrinths
  is filled with perilymph, which is very much like normal
  cerebral spinal fluid.
- 27 more annotations...
- - As the stapes vibrates the oval window, the perilymph
    sloshes back and forth, vibrating the round window in a complementary
    rhythm. The membranous labyrinth is caught between the two, and
    bounces up and down with all this sloshing
  - As with almost all sensory neurons (the exception is in the retina),
    its cell body lies outside the CNS in a ganglion. In this case,
    the ganglion is stretched out along the spiralling center axis
    of the cochlea, and is named the spiral ganglion.
  - basilar membrane is actually thinner and narrower
    at the base of the cochlea than at the tip (apex), which seems
    backwards given that the cochlea is widest at the base. The properties
    of the basilar membrane change as its shape changes; just as with
    guitar strings, thin things vibrate to high pitches, and thick
    things vibrate to low pitches. This means that the basilar membrane
    vibrates to high frequencies at the base of the cochlea and to
    low frequencies at the apex. A hair cell at the base of the cochlea
    will respond best to high frequencies, since at those frequencies
    the basilar membrane underneath it will vibrate the most. The
    key idea is that although the hair cells are arranged in order
    along the basilar membrane, from high-frequency to low-frequency,
    it is the properties of the basilar membrane that set up this
    gradient, not the properties of the hair cells.
  - outer hair cells help to "sharpen the tuning".
    Outer hair cells can actually move (change length) in response
    to nerve stimulation. If they could push the basilar membrane
    up and down, they could amplify or damp vibrations at will, making
    the inner hair cells more or less responsive. (Just like you
    can push a child higher and higher on a swing or bring her to
    a halt - it's all in when you push.)
  - Something about this tight connection allows the timing of the
    signal to be preserved to the microsecond (action potentials are
    on the order of milliseconds, so it is no mean feat). The ventral
    cochlear nucleus cells then project to a collection of nuclei
    in the medulla called the superior olive. In the superior
    olive, the minute differences in the timing and loudness of the
    sound in each ear are compared, and from this you can determine
    the direction the sound came from. The superior olive then projects
    up to the inferior colliculus via a fiber tract called
    the lateral lemniscus.
  - The second stream of information starts in the dorsal
    cochlear nucleus. Unlike the exquisitely time-sensitive localization
    pathway, this stream analyzes the quality of sound. The dorsal
    cochlear nucleus, with fairly complex circuitry, picks apart the
    tiny frequency differences which make "bet" sound different
    from "bat" and "debt". This pathway projects
    directly to the inferior colliculus, also via the lateral lemniscus.
  - Notice that both pathways are bilateral. The consequence
    of this is that lesions anywhere along the pathway usually have
    no obvious effect on hearing. Deafness is essentially only caused
    by damage to the middle ear, cochlea, or auditory nerve.
  - From the inferior colliculus, both streams of information
    proceed to sensory thalamus. The auditory nucleus of thalamus
    is the medial geniculate nucleus. The medial geniculate
    projects to primary auditory cortex, located on the banks
    of the temporal lobes.
  - Fibers from the cochlear nuclei
    and the superior olive (not the inferior) travel up the
    lateral lemniscus (not the medial) to the inferior
    colliculus (not the superior), and then to the medial geniculate
    (not the lateral). Try remembering the mnemonic,
    
    "S-L-I-M" .
  - You must be able
    to detect rotation, such as what happens when you shake or nod
    your head. In physics, this is called angular acceleration.
    You must also be able to detect motion along a line - such as
    what happens when the elevator drops beneath you, or on a more
    subtle note, what happens when your body begins to lean to one
    side. This is called linear acceleration. The vestibular
    system is divided into two receptor organs to accomplish these
    tasks.
  - semicircular canals detect angular acceleration
  - continuous endolymph-filled
    hoop. The actual hair cells sit in a small swelling at the base
    called the ampula.
  - hair cells are arranged as a single tuft that
    projects up into a gelatinous mass, the cupula. When you
    turn your head in the plane of the canal, the inertia of the endolymph
    causes it to slosh against the cupula, deflecting the hair cells.
    Now, if you were to keep turning in circles, eventually the fluid
    would catch up with the canal, and there would be no more pressure
    on the cupula. If you stopped spinning, the moving fluid would
    slosh up against a suddenly still cupula, and you would feel as
    though you were turning in the other direction.
  - Each tuft of hair cells is polarized
    - if you push it one way, it will be excited, but if you push
    it the other way, it will be inhibited. This means that the canals
    on either side of the head will generally be operating in a push-pull
    rhythm; when one is excited, the other is inhibited
  - if both sides push at once,
    then you will feel debilitating vertigo and nausea. This is the
    reason that infections of the endolymph or damage to the inner
    ear can cause vertigo. However, if one vestibular nerve is cut,
    the brain will gradually get used to only listening to one side
    - this can actually be a treatment for intractable vertigo.
  - semicircular canals exert direct control over
    the eyes, so they can directly compensate for head movements.
    Recall that the eye is controlled by three pairs of muscles;
    the medial and lateral rectus, the superior and inferior rectus,
    and the inferior and superior oblique. You may also remember
    that their directions of motion seemed to be at crazy diagonals.
    Those same crazy diagonals are matched closely by the three planes
    of the semicircular canals, so that a single canal (in general)
    interacts with a single muscle pair. The entire compensatory
    reflex is called the vestibulo-ocular reflex (VOR).
  - If you move your head to the left, you will excite
    the left horizontal canal, inhibiting the right. To keep
    your eyes fixed on a stationary point, you need to fire the right
    lateral rectus and the left medial rectus, to move the eyes to
    the right.
  - The pathway is as follows: the vestibular nerve
    enters the brainstem and synapses in the vestibular nucleus.
    Cells that received information from the left horizontal canal
    project to the abducens nucleus on the right side, to stimulate
    the lateral rectus. They also project to the oculomotor nucleus
    on the left side, to stimulate the medial rectus. Although not
    shown on the diagram, the same vestibular cells also inhibit the
    opposing muscles (in this case, the right medial rectus, and the
    left lateral rectus).
  - right horizontal
    canal is wired to the complementary set of muscles. Since it
    is inhibited, it will not excite its target muscles (the right
    medial rectus and the left lateral rectus), nor will it inhibit
    the muscles you want to use
  - A great deal of the VOR axon traffic travels via
    a fiber highway called the MLF (medial longitudinal fasciculus).
    The integrity of this tract is crucial for the VOR to work properly.
    It is occasionally damaged by medial brainstem strokes.
  - The utricle and saccule detect linear acceleration.
    Each organ has a sheet of hair cells (the macula) whose cilia
    are embedded in a gelatinous mass, just like the semicircular
    canals. Unlike the canals, however, this gel has a clump of small
    crystals embedded in it, called an otolith (yes, all along you've
    had rocks in your head). The otoliths provide the inertia, so
    that when you move to one side, the otolith-gel mass drags on
    the hair cells. Once you are moving at a constant speed, such
    as in a car, the otoliths come to equilibrium and you no longer
    perceive the motion.
  - single
    sheet of hair cells can detect motion forward and back, side to
    side. Each macula can therefore cover two dimensions of movement.
    The utricle lays horizontally in the ear, and can detect any
    motion in the horizontal plane. The saccule is oriented vertically,
    so it can detect motion in the sagittal plane (up and down, forward
    and back).
    
    A major role of the saccule and utricle is to keep
    you vertically oriented with respect to gravity. If your head
    and body start to tilt, the vestibular nuclei will automatically
    compensate with the correct postural adjustments. This is not
    just something that happens if the floor tilts - if you watch
    someone trying to stand still, you will notice constant small
    wavers and rocking back and forth.
Receptive field - Wikipedia, the free encyclopedia

en.wikipedia.org/...Receptive_field - Preview

ophthalmology on 2009-11-06
- There are two types of bipolar cells: "on-center" and "off-center". An on-center cell is stimulated when the center of its receptive field is exposed to light, and is inhibited when the surround is exposed to light. Off-center cells have just the opposite reaction.
- 3 more annotations...
- - Stimulation of the center of an on-center cell's receptive field produces depolarization and an increase in the firing of the ganglion cell, stimulation of the surround produces a Hyperpolarization and a decrease in the firing of the cell, and stimulation of both the center and surround produces only a mild response (due to mutual inhibition of center and surround). This prevents an overload of signals to the brain. An off-center cell is stimulated by activation of the surround and inhibited by stimulation of the center
  - The center-surround receptive field organization allows ganglion cells to transmit information not merely about whether photoreceptor cells are exposed to light, but also about the differences in firing rates of cells in the center and surround. This allows them to transmit information about contrast.
  - The receptive field tends to favor movement (such as a light or dark spot moving over the field, as in center-to-periphery (or vice versa)), as well as contours (due to their nonuniformity in the receptive fields).
Eye and Retina

thalamus.wustl.edu/...eyeret.html - Preview

ophthalmology on 2009-11-06
- retina, seven
  layers of alternating cells and processes which convert a light
  signal into a neural signal ("signal transduction").
  The actual photoreceptors are the rods and cones,
  but the cells that transmit to the brain are the ganglion cells.
  The axons of these ganglion cells make up the optic nerve
- pupillary sphincter muscle constricts the pupil like a purse-string, and is under the control of the parasympathetic system. Therefore it is innervated by fibers from the oculomotor nerve which originate in the Edinger-Westphal nucleus of the midbrain.
- 15 more annotations...
- - pupillary dilator muscle is composed of radial fibers which pull the pupil open, and is controlled by the sympathetic system. Therefore it is innervated by post-ganglionic sympathetics from the superior cervical ganglion.
  - zonule fibers - hold the lens stretched out into
    a more disc-like shape. This shape allows for far-focusing. What
    happens when you need to near-focus? At this point the ciliary
    body, a hoop-like structure that supports the zonule fibers,
    comes into play. Imagine a spiderweb built into the opening of
    a drawstring purse, suspending a disk in the opening. When the
    purse is open, the spiderweb is taut. If you pull the drawstring,
    however, the web will go slack and collapse on itself. The ciliary
    body is the drawstring purse, in this analogy. The ciliary
    muscle within it is the drawstring. When the ciliary muscle
    contracts (this is also under parasympathetic control), the zonule
    fibers go slack, the suspended lens is released from their tension,
    and it is free to round up. This change is necessary for near-focusing.
    The entire process of adjusting the focus to different distances
    is called accommodation.
  - retina is a seven-layered structure
    involved in signal transduction. In general, dark "nuclear"
    or "cell" layers contain cell bodies, while pale "plexiform"
    layers contain axons and dendrites.
  - In the OPL photoreceptor axons
    contact the dendrites of bipolar cells and horizontal cells. Horizontal
    cells are interneurons which aid in signal processing.
  - In the IPL, bipolar axons contact
    ganglion cell dendrites and amacrine cells, another class of interneurons
  - The ganglion cells of the GCL send
    their axons through the OFL to the optic disk to make up the optic
    nerve. They travel all the way to the lateral geniculate nucleus.
  - fovea defines the center of the retina, and is the region of highest visual acuity. The fovea is directed towards whatever object you wish to study most closely - this sentence, at the moment. In the fovea there are almost exclusively cones, and they are at their highest density.
    The ratio of ganglion cells : photoreceptors is about 2 :1 here, the highest in the eye. In addition, at the fovea all of the other cell types squeeze out of the way to allow the most light to hit the cones. This makes the fovea visible microscopically. The blood vessels also skirt a wide margin around the fovea. The area in and around the fovea has a pale yellow pigmentation that is visible through an ophthalmoscope, and is called the macula.
  - ganglion cell axons all leave
    the eyeball at one location, the optic disk. At the optic
    disk all photoreceptors and accessory cells are pushed aside so
    the axons can penetrate the choroid and the sclera. This creates
    a hole in our vision, the blind spot. Normally each eye covers
    for the blind spot of the other, and the brain fills in missing
    information with whatever pattern surrounds the hole. Therefore
    we are not conscious of the blind spot.
  - Most cones lie in the fovea, whereas
    peripheral vision is dominated by rods. Overall, rods greatly
    outnumber cones. Review the characteristics of rods (black and
    white vision, very sensitive to low light) and cones (color vision,
    not so sensitive) and explain these phenomena:
    
    1. To see a faint star, you cannot
    look directly at it, but must look slightly to the side.
    
    2. A person with macular degeneration
    can become functionally blind, yet their night vision is not really
    affected. How would their color perception be?
  - - The cornea is continuous
    with the sclera, which in turn is continuous with the dura.
    
    - The choroid, a highly vascular,
    highly pigmented layer between the sclera and the retina, is continuous
    with the ciliary body and the iris. Do not confuse it with the
    pigment epithelium.
    
    - The pigment epithelium is
    a single cell layer thick, and comes from the outer layer of the
    original optic cup (a classic embryological "pushed-in
    ball"). In the mature retina it is pushed directly up next
    to the neural retina, which came from the inner layer of the optic
    cup. They are not fused together, however, and can separate along
    the old plane - a "separated" or "detached"
    retina.
  - If you were to record from a photoreceptor,
    you would find that it was "ON" (hyperpolarized, paradoxically)
    whenever light shone on it. If you recorded from a ganglion cell
    instead, you would find that diffuse light did little to the cell.
    However, the cell would respond well to a small spot of light,
    a small ring of light, or a light-dark edge. We say that this
    cell has a center-surround receptive field - the center
    must be mainly light and the surround mainly dark, or vice versa.
    What happens between the outer segment and the ganglion cell?
    This complex receptive field is created by the interneurons of
    the retina: the bipolar cells and the horizontal cells, primarily.
  - neighbor cones also excite horizontal cells. The horizontal cells send processes laterally and inhibit the center bipolar cell.
    
    So, what does diffuse light do? It excites the central bipolar cell, but also inhibits it via the neighbors. Result - the ganglion cell does not get excited. It continues to tick along at its normal, tonic rate.
  - our entire
    visual system exists to see borders and contours. We see the world
    as a pattern of lines, even things as complex as a face. We judge
    colors and brightness by comparison, not by any absolute scale.
    (Don't believe it? Put that teal scarf next to a blue shirt, you'll
    call it green. On a green coat, you'll call it blue.) This system
    of lateral inhibition in the retina is the first step towards
    sharpening contours and picking up on borders between light and
    dark. Diffuse light is ignored by the ganglion cell, but a sharp
    dot will really turn it on. Higher up in the cortex, all these
    dots will be combined into lines, which will be combined into
    curves, etc, etc.
Eye, Brain, and Vision

hubel.med.harvard.edu/b9.htm - Preview

ophthalmology clinicalexEYE on 2009-11-06
- Left:
  Four recordings from a typical on-
  
  center retinal ganglion cell. Each record is a
  
  single sweep of the oscilloscope, whose
  
  duration is 2.5 seconds. For a sweep this
  
  slow, the rising and falling phases of the
  
  impulse coalesce so that each spike appears
  
  as a vertical line. To the left the stimuli are
  
  shown. In the resting state at the top, there
  
  is no stimulus: firing is slow and more or
  
  less random. The lower three records show
  
  responses to a small (optimum size) spot, a
  
  large spot covering the receptive-field cen-
  
  ter and surround, and a ring covering the
  
  surround only. Right: Responses of an off-
  
  center retinal ganglion cell to the same set
  
  of stimuli shown at the left.
- 2 more annotations...
- - The
    two main types of retinal-ganglion-cell
    
    receptive fields are on center, with inhibi-
    
    tory surround, and off center, with excita-
    
    tory surround. "+" stands for regions giv-
    
    ing on responses, "—" for regions giving
    
    off responses.
    
    A
    cross section of the retina, about mid-
    
    way between the fovea and far periphery,
    
    where rods are more numerous than cones.
    
    From top to bottom is about one-quarter
    
    millimeter.
Central Visual Pathways

thalamus.wustl.edu/...cenvis.html - Preview

clinicalexEYE ophthalmology on 2009-11-06 and saved by 2 people
- ganglion cell axons leave the retina, they
  travel through the optic nerve
- optic tract wraps around the cerebral
  peduncles of the midbrain to get to the lateral geniculate
  nucleus (LGN). The LGN is really a part of the thalamus,
  and remember that nothing gets up to cortex without synapsing
  in thalamus first (if the cortex is the boss, the thalamus is
  an excellent secretary). Almost all of the optic tract axons,
  therefore, synapse in the LGN. The remaining few branch off to
  synapse in nuclei of the midbrain: the superior colliculi
  and the pretectal area.
- 8 more annotations...
- - LGN send their axons directly
    to V1 (primary visual cortex, striate cortex, area 17)
    via the optic radiations. This highway of visual information
    courses through the white matter of the temporal and parietal
    lobes, and can be very vulnerable to strokes.
  - What we see can be divided into several categories
    of vision: color, linear pattern, motion, etc.
  - rods see only black and white, and can function in dim
    light, whereas cones can see all colors but require full light.
  - small ganglion cells that dominate in the fovea: they are
    color sensitive and are "fine-grained", meaning their
    receptive fields are small enough that they can pick up a high
    level of detail. These small cells are called P cells
    (P for parvo for small). The second type of ganglion
    cells have large dendritic arrays, and receive information from
    a wide radius of bipolar cells. They are mostly found in the
    peripheral retina, are not color-sensitive, and are "coarse-grained"
    and relatively insensitive to detail. Their main asset is that
    they are sensitive to motion - you can imagine that due to their
    width they can track a signal flashing across several bipolar
    cells. These are the M cells (M for magno ).
  - These two types of information, motion vs. color
    and form, are maintained in separate compartments all the way
    up the visual pathway. They are kept in separate layers in the
    LGN, enter V1 via separate sublayers (4Ca vs. 4Cb), and after
    passing through V2, go on to separate areas of associative cortex.
    In the end, the parietal visual cortical areas (such as
    MT and PP) end up dealing with motion of objects, navigation through
    the world, and spatial reasoning (which is essentially moving
    things around in your head). Temporal visual areas (such
    as V4 and IT) are involved with the complex perception of patterns
    and forms as recognizable objects.
  - few optic tract fibers which bypassed the LGN
    entirely, traveling instead to the less glamorous but equally
    essential midbrain. One of their targets in the midbrain is the
    pretectal area, which mediates the pupillary light reflex.
    This reflex can be demonstrated by shining a light in one eye;
    if all is working correctly, both pupils will constrict.
  - directly
    to the pretectal area. After synapsing, the information is sent
    to the Edinger-Westphal nuclei on both sides of
    the midbrain - this is the crucial step in ensuring that both
    eyes react to light. The Edinger-Westphal nuclei, via the IIIrd
    nerve, control the pupillary constrictors that narrow the
    pupils
The W.U.S.M. Neuroscience Tutorial

thalamus.wustl.edu/course - Preview

Neurology on 2009-11-06 and saved by 43 people