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BIOL 373 Lab Exam Notes.docx

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University of Waterloo
Bruce Wolff

SPECIAL SENSES     Vision, taste, smell, equilibrium, and hearing, complex organs contain large numbers of individual sensory receptor cells.  1) VISION a. VISUALACUITY - myopia (nearsighted) hyperopia (farsighted) Snellen Chart – determine degree of detail the eye can distinguish (cover one eye). Last line that can be read represents the approximate visual acuity for that eye. (20 feet) b. ASTIGMATISM – defective curvature(causes blurring) – some light rays not focused, spread out Astigmatism Chart – normal – all bars are sharp and evenly dark. Abnormal see some lines thick and dark while others are lighter and blurred. (10 feet) c. COLOUR VISION – deficiency of receptor potentials (cones – converting red/green/blue) Ichikawa Colour Vision Test – coloured plates (red-green blind), 3 seconds, says number, 8/10 right, normal (plates 5 to 14), 3 > more responses = (plates 15-19) to determine type of blind. (30 inches) 2) TASTE Quinine Sulfate (Back – Bitter). AceticAcid (Back/Sides – Sour). NaCl (Middle/Sides – Salt). Sucrose (Front – Sweet). 3) OLFACTION Peppermint/Nose closed – olfaction helps distinguish tastes (hold nose for medicine) (Tonic) Slow adapting receptors – continuous sequence ofAps as long as stimulus lasts. (Phasic) Rapid adapting receptors – detect stimulus of constant strength, sequence steadily decreases. Nose is phasic, after long with garlic, will lessen. Move away? Notice change. 4) HEARING Sounds waves can be transmitted through air conduction and through bone conduction (mastoid). Ring through bone, then when gone, put near ear – will reappear. Doesn’t reappear? Bad. a. Rinne’s Test – normal is better hearing via air conduction than bone conduction. Bone > Air = hearing loss, inhibiting the passage of sound (middle ear). Bone = Air = Bad = sound stopped earlier (sensorineural, inner ear). b. Weber’s Test – normal is that the sound is heard equally on both ears (once tuning fork is on midline of skull). If normal ear hears tuning fork better, inner ear damage. If defective ear hears tuning fork better, middle ear damage. Must use both to tell which kind of damage and which ear. Plugged ear will hear better (conductive hearing loss). Louder external noise makes the noise less audible. c. AuditoryAcuity Test - lower the frequency, the greater the distance it can be heard (longer the wavelength?) 5) EQUILLIBRIUM Romberg Test - proprioceptors (sensory from the skeletal muscles and positions of limbs), cerebellum, semicircular canals (middle), inner ear, all help to maintain balance. Eyes open – no movement. Eyes closed – sways. Use proprioception (one’s body in space), vestibular function (head position in space), and vision (changes in position). If falls – then proprioception is defective SOMATIC SENSES In order for two separate points on the skin to be perceived and discriminated by the brain as two distinct stimulus, two requirements must be met. 1) stimulation of at least two spatially separated touch-sensitive nerve endings must occur (in the skin); more likely when widely spaced and on sensitive parts. 2) In the spinal cord and brain, nerve impulses triggered by the two stimuli must be carried in two separate pathways, resulting in activity in two separate locations in the somatosensory cortex. Such spatial separation of sensory structure and function in the spinal cord and brain is a key feature underlying our ability to discriminate or resolve separate points of touch. Two Point Discrimination Advantages of having different densities of touch receptor in different regions of body? Fingers, tongues, explore the environment with hands, better for survival that way. Places like the face (lips, nose,), and the tips of toes and fingers – have the smallest millimeters of sensing. Places like the lower shoulder blade, trunk, mid calf, mid back, front of thigh – have the largest millimeters of sensing. Directly related to density of receptors. Mapping Cold Receptors In most areas of the body, there are three to ten times as many cold points as warm points. Estimate the sensory field size for a single cold point on the skin. Typically, the dimensions of a cold point are approximately 1-2mm across (one or two dots). More than 1 sensation of cold when each of the two adjacent holes stimulated? More than one field likely involved. Divide estimated number of cold point in the grid by the grid’s area to obtain estimate of concentration of cold sensors. DIFFERS IN THE BODY (Many in the lips 15-25/cm, fewer in the finger 3-5/cm, even less in the broad areas of the trunk 1/cm) REFLEXES Spinal reclexes – stimulation and inhibition of muscle contraction. Reflex arc – links sensory input and motor output. Receptor and Effector. Receptor is sensor cell (converts stim to Aps, passed along afferent (sensory) neuron to s-cord. Simplest: sensory neuron sends signal to motor pathway (efferent neuron) leading to an effector (muscle, gland); this is monosynaptic reflex. Visceral Reflex: heartbeat, breating Somatic: skeletal muscles Postural: function, location, etc. Location – proprioceptor detects stretch within muscle/tendon: Spinal Reflexes KNEE JERK – hit below the tendon, leg extends (quad contracts, hamstring relaxes) ACHILLES JERK – strike ach tendon – foot jerks down TRICEPJERK – cervical spinal nerve 7 (radial nerve) – contracts the tricep Cutaneous Reflexes BABINSKI REFLEX – stimulation of cutaneous (skin) receptors on sole of foot – not in the spinal cord, but in the brain. Axons descend into the spine, good test of integrity of the spine. Normal- toes curl down/together. Abnormal – toes curl up. Lie down on back, knee bend, draw blunt object along L shape up foot. Cranial Nerve Reflexes PUPILARY LIGHT REFLEX – eyes close consensual in response to light in one eye (none = nerve damage) Optic Nerve = senses the incoming light (afferent) Oculomotor Nerve = drives muscles that constrict pupil CORNEAL BLINK REFLEX – blow air – should be rapid consensual in response – survival to keep out things MENACE REFLEX – no air, immediate can include turning of the head – in combination with other flex, can diagnose location of damage. Can be overridden. Fine Motor Control With weight, signature if hampered – when body’s gross motor units are in usage (holding bucket), fine muscle usage is hampered. Fine motor movement requires many more muscle groups recruited (hands), holding weight distracts number of muscle cells originally dedicated to hand movements. Question One – List the events, in sequence, that occur between the striking of the patellar tendon and the extension of the leg. 1) Stimulus (tendon tap) – stretches the muscle spindle, activates, and fires… 2)Action potential through the sensory neuron (via sensory fibers) 3) Synapses with sensory neurons in spinal cord, which are synapsed onto motor neurons) a. Somatic motor neurons effect the quadricep muscle (CONTRACT) b. Interneuron (inhibitory) somatic motor neurons effect the hamstring muscle (RELAXES) c. EXTENSION (RECIPROCAL INHIBITION – contraction of quads is unopposed) Question Two – What does an abnormal Babinski response indicate damage to the spinal cord at any level? Since the cutaneous skin receptors in the sole of the foot are integrated in the brain (not the spinal cord), the response to a stimulus is carried all the way from the motor cortex to motor neurons in the spine via pyramidal cell axons; the motor neuron is classified as an upper motor neuron and communicates between the brain and the spinal cord: these axons relay the message all the way along the corticospinal tract, an abnormal Babinski reflex could indicate damage along any point along the spinal cord. Other reflexes concern lower motor neurons that communicate between muscle spindle fibers and motor neurons in the spinal cord (do not involve the motor cortex or the entire corticospinal tract). Question Three – Which parts of the body have the largest areas of the cortex? Which have the smallest? Largest – body parts where sensory receptors are most dense: fingers, thumbs, lips, tongue, genitals, face, arms Smallest – body parts where sensory receptors are least dense: teeth, gums, jaw, trunk, neck, shoulder, eyes, toes Question Four – How does the ear transduce sounds into electrical nerve impulses? 1) First Transduction – sound waves strike tympanic membrane, become vibrations 2) Sound wave energy is transferred to the three bones of the middle ear, which vibrate 3) Second Transduction – the stapes is attached to the oval window membrane; vibrations of the oval window create fluid waves in the cochlea 4) Third Transduction – fluid waves push on the flexible membranes of the cochlear duct. Hair cells bend and release NT 5) Fourth Transduction – NT release onto sensory neurons createsAPs - travel through cochlear nerve to brain 6) Energy from the waves transfers across the cochlear duct into the tympanic duct and is dissipated back into the middle ear at the round window Question Five – if subject has severe middle ear infection (both ears), how will this affect the results of the Rinne’s test? Given that a middle ear infection would cause a swelling that would block sound from moving to the inner ear via air conduction. The Rinne test would therefore be negative, because of temporary conductive hear loss, causing bone conduction to be the better air conduction. Question Six – What senses are affected by lateral inhibition? Briefly explain how the process functions Hearing – pitch discrimination – basilar membrane vibrations Vision – visual acuity (enhances contours) – ganglion cells Touch – sharpens sensations for localization - neurons Increases the contrast between activated receptive fields (around cells) and their inactive neighbors; helps to localize stimuli. Primary neuron response is proportional to stimulus strength. Pathway closest to stimulus inhibits neighboring neurons. Inhibition of lateral neurons enhances perception of stimulus. Movement and positioning of eye involves a complex array of muscular control and innervation. In humans, six muscles (innervated by motor neurons) are externally attached to each eye (grouped into antagonistic pairs) about the vertical, horizontal, and torsional axes (Purves et al., 2001, Department of Biology, 2013). Medial and lateral rectus muscles are paired about the vertical axis (controlling inward (adduct) and outward (abduct) eye movement towards and away from the direction of the nose, respectively). Superior and inferior rectus muscles are paired about the horizontal axis (controlling upward (elevated) and downward (depressive) eye movement, respectively, as well as eye rotation toward (intort) and away (extort) away from the nose, respectively). Superior and inferior oblique muscles are paired about the torsional axis (controlling depressive intort and elevated extort of the upper eye region, respectively) (Purves et al., 2001; Büttner-Ennever, 2007; Department of Biology, 2013). Measurable electrical activity within each muscle’s motor neurons allows for both the velocity of eye movement (phasic, using a direct communication pathway from the brain to the motor neuron), and positioning of the eye (tonic, using an indirect pathway) (Department of Biology, 2013). Velocity is chiefly responsible for stabilizing gaze during physical motion, and motion perceived in the external environment; its neural pathway is distinct from positioning (Pastor et al., 1994). Positioning involves the integration of velocity activity via neural networks; each type of oculomotor control is associated with diverse integrations of velocity commands in various neural groupings, and is correlated with a unique eye movement (Purves et al., 2001). Firstly, saccades are abrupt, rapid movements of the eye that continuously alter the fixation point (Purves et al., 2001). Ranging from small (while reading) to large (while gazing a landscape) movements, saccades rotate the eyes so as to position a target image within the fovea (the focal point, i.e. retinal region for detail). Saccades movements (while vision-poor) are accurate given our internal estimation ‘system’ that predicts where the intended position of a target image will be, and moves the eyes in accordance with that perceived distance (Purves et al., 2001). Secondly, pursuit movements of the eye do not continuously alter the fixation point; rather, pursuit movements track a moving target image by fixating the fovea. Pursuit involves an initial electrical signal delay due to the recruitment of additional neural networks that help track moving targets, and often utilizes a saccades movement to help the eye firstly capture these objects (Purves et al., 2001). Thirdly, VORs will ensure that larger background targets (such as the external environment) are kept fixed while the head moves. VOR ensures that a target image is kept at roughly the same place on the retina by utilizing sensory information from the semicircular canals and directing the eyes opposite the movement of the head in equal velocity; VOR itself is considered a phasic reflex (rotation of eye is a phasic command via direct pathway), while image fixation is tonic (tonic command via indirect pathways) (Purves et al., 2001; Department of Biology, 2013). Lastly, vergence movements are important for aligning the fovea of each eye with target images that are located at varying distances. In vergence, eye movements will be disjunctive (as opposed to conjugate during other types of movements), rotating oppositely to either converge when foveae are moved from a distant object to a closer object, or diverge when foveae are moved from a close object to a more distant object (Purves et al., 2001). Electrical activity that is associated with each eye movement may be recorded using electrodes that are placed on the temples and neck, and presented as an electroculogram (EOG). METHODS SACCADES - paragraphs were chosen from pages 37 and 47 of the laboratory manual for subjects to read (simple and complex paragraph readings, respectively). VOR head rotation task - subjects were asked to focus on a tennis ball placed approximately 1 foot in front of them while moving their head from side-to-side. PURSUIT pendulum task - the tennis ball was suspended by an experimenter’s hand, and was kept in continuous motion. VERGENCE close vs. distant object task - two tennis balls were used as the targets that were similar in size and shape and were aligned at comparatively similar heights RESULTS Saccades EOG patterns were found to peak during sentence reading, and dip as the eyes moved to a new line; eye movements were seen as rapid, and abrupt. (progressive inclines, met by sharp drops with new line) VOR EOG patterns were observed to be continuous, equal in magnitude, and equidistant; eye movements were mostly smooth, but appeared slightly saccadic. (continuous and equal ski hills) Pursuit EOG patterns were also found to be continuous, equal in magnitude, and equidistant; eye movements appeared saccadic, but were actually smooth. (continuous but sharper equal ski hills) Vergence EOG patterns responded to convergence (slightly crossed and depressed eyes) in upward peaks, and divergence (slightly elevated, looking outward) in downward dips; eye movements were found to be saccadic. Slower eye movements during all of the experimental tasks appeared to alter EOG patterns by way of increasing the width of peaks, dips, and/or the distance between them. Describe the motion of eyes during VOR. Is it smooth or saccadic? Does the motion of subject’s eyes differ between vestibular ocular reflexes of different degrees or velocities? According to previous research, the phasic command that is sent via the direct pathway to the eyes will rotate them in the opposing direction of the head movement, while a tonic movement will cause the eyes to remain fixed in that position via indirect pathways Given that subjects’eyes were consistently fixed on an image, the eyes would not technically be moving, but only be appear to be moving via saccades; this became more clear during slower head movements where the eyes appeared to move less saccadically. Visual fixation is never perfect; upon close examination, the eye will have small saccadic movements that are integral to visual perception. Describe the motion of the subject’s eyes during pursuit. Is it smooth of saccadic? the eyes of either subject were seen to move in saccadic movements during fast pursuit, and more smoothly during slow pursuit. The eyes may have appeared to move in saccades during fast pursuit because the movement of the tennis ball was so quick, leading the observer to believe that the eye was constantly attempting to ‘capture’the object with the fovea; however, slower pursuit movements revealed that the eyes were generally smooth How does the patter of the EOG recorded during the “slow saccadic” reading of the first paragraph compare to the normal reading of the same paragraph? How does the motion of the subject’s eyes differ between these readings? EOG patterns were found to have increased distances between each dip (dips were also observed to be less steep). Furthermore, both subjects’ eyes moved quicker and with more comprehensive motions during the regular reading speed task. How does the pattern for convergence differ from the pattern for divergence? Convergence patterns were seen as sharp upward peaks, while divergence patterns were seen as sharp downward dips. converge when foveae are moved from a distant object to a closer object, or diverge when foveae are moved from a close object to a more distant object Describe (name) the three “directions” of motion that are controlled by the opposing eye muscles that were studied in this exercise. Vertical, horizontal, and torsional axes? Adduct, abduct – inward and outward from the nose Elevated and depressive – upward or downward Extort and intort – rotate toward away from the nose HYDROLYSIS – digestion of nutrient molecules (from polymeric form to monomeric) – enzyme help this PROTEINS (effects of pH and temp) Stomach acid and pepsin make digestion of peptides in small intestine easier. 1)ACID DENATURES (untwists, exposes more peptide bonds) 2) PEPSIN (breaks some peptide bonds, shorter peptide molecules) 3) NEUTRALIZATION (once in small-I, neutral means they stay this way, can’t resume shape while exposed to enzymes) Digestion of Protein (Egg white) by Pepsin and Trypsin LeadAcetate Test – positive ofAAs with sulphur (black precipitate). Boil. Used: water bath, ice bath, 10 test tubes (5 each enzyme), sharpie. Solution Actual Result Expected Result 1 drop distilled + pepsin (warm) Digestion (+) 1 drop HCL + pepsin (warm) Digestion (+) Pepsin – best at 2pH & warm 1 drop HCL + pepsin (freeze) No digestion (-) 1 drop HCL + distilled (warm) No digestion (-) 1 drop NaOH + pepsin (warm) No digestion (-) 1 drop distilled + trypsin (warm) No digestion (-) 1 drop HCL + trypsin (warm) No digestion (-) 1 drop HCL + trypsin (freeze) No digestion (-) 1 drop HCL + distilled (warm) No digestion (-) 1 drop NaOH + trypsin (warm) Digestion (+) Trypsin – best at 8pH & warm CARBOHYDRATES (effects of pH and temp) Starch digested into smaller non-polymers of glucose 1)AMYLAZE (starch to maltose – dissacharide, plus small maltotriose and isomaltose) 2) MALTASE (maltose to glucose) Iodine Test for Starch – 1 drop in solution, dark blue-black colour indicates starch Benedicts Test for Reducing Sugars – mix solution with mixture, boil, coloured precipitate (cuprous oxide) is positive for reducing sugars. Slightly positive = cloudy green. Very positive = bright red. Used: 5 test tubes, water bath (37C), hot plate (boil), test tube holder, test tube rack, sharpie. Solution Actual Result Expected Result 3.0 distilled (iodine) Starch (+) 3.0 amylase (iodine) No Starch (-) 3.0 HCL + 3.0 amylase (iodine) Starch (+) 3.0 boiled amylase (iodine) No Starch (-) 3.0 HCL (iodine) Starch (+) BoiledAmylase is best 3.0 distilled (benedict) No maltose Increased Temp +Amylase would help 3.0 amylase (benedict) (+)(+)(+) pH of 8.5 would also help. 3.0 HCL + 3.0 amylase (benedict) (+) green 3.0 boiled amylase (benedict) (+)(+)(+) 3.0 HCL (benedict) No maltose LIPIDS (effect of bile salts) Triaglycerol is digested by lipase enzymes to two free fatty acids and a monoacylglyceral. 1) LIPASE (triacyglyceral > monoacylglyceral + two fatty acids) Lipase enzymes dissolved in water, lipid substrates very low aqueous solubility, form micelles. Immiscibility limits degree of interaction between enzyme and substrate. Another factor that limits results is differential solubility of the fatty acids produced by lipid digestion. More soluble? Influence the pH of the digestion mixture to greater extent than those less soluble. Solution Actual Result Expected Result 0.5% Lipase + no bile salts BILE SALTS HELP DEGRADE EVEN No change > (+) some change (little) 0.5% Lipase + 0.5% bile salts MORE OIL Decreased pH 0.5% Lipase + 1% bile salts Decreased pH x 2 0.5% Lipase + 2% bile salts Decreased pH x 3 (red/pink) 2% Bile Salts only No change Proteinases Enzyme Substrate Products Pepsin
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