Lab 1 : Neural and Sensory Function Flashcards
Objectives
A) Investigate some properties of the special senses and somatic senses
2) Elicit some reflexes
3) Illustrate fine motor control
How do sensory cells respond to factors such as light, pressure, chemical nature?
-respond by creating electrical signals that are sent to the nervous system
Why is it important to have information on the internal and external environment
to maintain homeostasis
What are the special senses
vision, taste, smell, equilibrium, and hearing
What do the special senses depend on (think organ) and what do they contain
Depend on complex organs and contain a large number of INDIVIDUAL sensory receptor cells
Where are the sensory cells of somatic senses found
not concentrated in sensory organs (like special senses), but found widely distributed amounf the skin, muscles, joints
Do REFLEXES and FINE MUSCLE CONTROL depend on sensory cell information
Yes
What are the three aspects of Vision (like the tests ig)
1) Visual Acuity: refers to the degree of detail that the eye can distinguish
2) Astigmatism: the blurring or distortion of the visual image caused by a defective curvature of the refractive surfaces of the eyes
3) Colour Vision:Ability to see colour
What is used to determine visual acuity
A Snellen Chart:
Test works by…
1) Standing 6 meters away from the chart
2)Cover one eye and read the letters on the chart until they are hard to distinguish
3)The last line read without mistakes represents the APPROXIMATE VISUAL ACUITY OF THAT EYE
What does Myopia and hyperopia mean
Myopia:
-Nearsightedness
-ability to see objects near you, but objects far away appear blurry
-occurs when the shape of your eye causes light rays to bend incorrectly, focussing images INFRONT of your retina instead of on your retina
Hyperopia:
-Farsightedness
-ability to see objects far from you more clear than objects near you
-occurs when eyeball is too short or curvature of CORNEA is too little, making light to focus BEHIND the retina, instead of on
What is Astigmatism
-the blurring or distortion of the visual image caused by the defective curvature of the refractive surfaces of the eye
-causes some light rays to not be sharply foccused but spread
How to test for Astigmatism
-look at the chart from 3 meters (10ft) away
-if the lines (bars) are sharp and evenly dark: eyes are normal
-if the lines are unevenly thick and some darker than others, while other lines are blurred and light: astigmatism
What is colour blindness caused by
deficiency in the retina’s system (cones: sensory cells that do this) for converting RGB light into receptor potentials
What measures colour perception
Ichikawa Colour Vision Test:
-used to detect red-green heriditary deficiency
-plates that have different colours on it that make up different numbers
-held 30 inches away from subjecy
-plates 1-4 are for orientation
-plate 5 is where testing begins
-the subject must concentrate on the coloured plate and say the number that they immediately see (if more than one is seen, they say the most common one)
-plates 15-19 determine the type of colour blindness
RESULT INTERPRETATION:
if 8 of 10 (since plate 5-14 is tested) is right, normal vision
if 3 or more abnormal responses: continue plates 15-19 to see which type of colour deficiency is present
What is the most common type of colour blindness
-red green deficiency
What shape and where are the taste bud sensory cells found
Shape: Barrel-shaped groupings of sensory cells
Located: tongue, epithelial lining of the mouth
How to test for taste
1) Dry Tongue
2) Apply the mxture you are testing for on the tip, sides and back of tongue
3) Indicate where u taste the solution
Solutions tested for:
5% Sucrose: sweet
1% acetic acid: Sour
5% NaCl: Salt
0.5% quinine sulfate;bitter
Are taste buds for different things uniformly distributed (is each pf the four primary tastes sensed equally everywhere inside the mouth?)
YEP!
How to test Olfaction
-Pinch your nostrils and eat a peppermint candy, determine whether it tastes like peppermint
-unplug your nose and taste it now
Results:
when plugging your nose, the strength of the peppermint is less strong
-therefore, olfaction increases taste
What are the two ways that sensory cells can respond to prolonged stimulation
the two ways allow the cells to be classified as two different types of cells
1) Tonic Cells:
- aka slowly-adapting sensors
-produce a continous sequence of action potentials as long as stimulus is present
-therefore, APs are as long as stimulus
2) Phasic Cells:
-aka rapidly adapting receptors
-if a continous, constant strength stimulus present: AP’s sent to CNS by these cells have a decreasing frequency (ie think one sent every 5 seconds instead of one sent every second)
-sense stimuli that is not important to survival
Garlic test
-tests to see if holding a constant stimulus changes our perception of the smell
-after 30 seconds of holding it under nose, it cannot be smelt anymore
How is hearing detected?
-vibration of oval window in response to sound waves (air conduction)
AND
-sound waves transmitted through Skull bones (bone conduction)
What are the three types of hearing tests
1) Rinne’s Test:
-tests for hearing problems using bone conduction and air conduction
-do this test in quiet environment
2) Webers Test
-test for hearing problems as well EXCEPT this tests for hearing individually for both ears, allowing differences between hearing loss of the ears to be determined
-ie can see if earing loss in right ear is different from left
3) Auditory Acuity
-tests the ability to hear different frequencies
Rinne’s Test
Steps:
1) hit a tuning fork and place the butt of handle on the MASTOID PROCESS OF TEMPORAL BONE (behind ear)
2)once sound is no longer detected (through skull), move it to the ear hole (external auditory opening)
if no damage to middle ear…
-sound will reappear when held to ear opening (positive result)
-may be an indication of sensorineural hearing loss too
If listening through skull better than listening through ear opening…
-means result is negative
-conductive hearing loss (inner or middle ear damage that cause sound that travels through air to be impacted)
-can be stimulated by placing a cotton ball in ear and doing test again as this prevents air conduction from occuring
Air conduction vs bone conduction
Air conduction: when sound waves travel through air into ear opening
Bone conduction: when sound waves use skull bone to detect souns waves
Webers Test
-place tuning fork on midlline of skull
-test on both sides of head to test for both ears
when plugging an ear: it is louder in the ear that is plugged, meaning that external noise causes the noise pf the tuning fork to be percieved as quieter
Auditory Acuity
Subject must close eyes and plug one ear
1) Strike tuning fork near ear opening and move it away until the subject no longer hears it
2) Record with different frequecencys and record the distance at which they cannot hear it anymore
How is Equilibrium tested
Romberg Test
1) Stands with his back against but not touching wall
2) Draw lines parallel to subjects arms
3) Make the subject stand there for 2 mins, observer monitors how far (to what degree) the subject moves
4) Repeat trial with eyes closed
5) Repeat with the subjects left shoulder against the blackboard (test forward movement)
Results:
when eyes closed, the subject sways to a bigger degree, meaning the sense of sight is important to equilibrium
What is Equilibrium
-Maintainence of an upright position while standing or moving/ the ability to maintain balance and orientations
-depends on input from multiple senses
-info is sent to CNS (brain) which responds by sending signals to muscles in legs, back and other places
Are the receptor cells of the skin grouped into organs?
NO
What are the stimuluses that each type of sensory neurons in the skin are sensitive to (multiple)
1) Touch
2) Pressure
3)Vibration
4)Pain
5)Heat
6)Cold
How are the sensory afferent neurons located, looking like, ending?
Looks: single axon extends in both directions from the cell body
Cell body located in DORSAL ROOT GANGLION of spinal cord, one end extends to the skin with several dendrites, each terminating into a receptor ending
other axon terminates in the spinal cord
What are receptor endings
where the branching of dendrites of the axon terminates
What is the neurons trigger zone
area of branching of dendrites is called this
How is touch detected
1) Stimulus is detected by receptor endings
2)electrical impulses (AP) sent up axon into spinal cord
3) AP is relayed to other neurons AND up to thalamus of brain (where info translated to neurons in somatosensory cortex of cerebrum)
Difference of perception and detection
Perception:
-meaning consciousness
-only occurs when appropriate neurons in the somatosensory cortex of brain receive the impulses
-the somatosensory cortex is also split into different regions, each region devoted to a specific part of the body (so that touch of that part can be precieved), some parts have bigger area than others
Detection:
occurs at the receptor ending of skin
What does large region in the somatosensory cortex mean
-means a larger sensitivity for the senses, so way more receptor endings there and more parts that recieve signals from them in brain
Why is it good that our skin has rapid sensory adaptation to a constant stimulus
-so that we are not distracted by constant touch stimuli that is unimportant
-ie the feeling of our clothes when we are not moving
Two-Point Discimination of Touch
-ability to determine touch of two different points on skin to be PERCIEVED BY BRAIN as two distint touches
What are the two requirements for two point discrimination of touch
1)IN SKIN:
-the stimulus must stimulate TWO SPATIALLY SEPERATED NERVE ENDINGS
-more likely to happen if stimuli is spaced apart or occur in sensitive areas of skin that have many touch receptors per area
2) In SPINAL CORD
-nerve impulses MUST be carried by two sperate pathaways, resulting in activity in two SEPERATE locations in Somatosensory cortex
-this is whatmakes this structure of brain and spinal cord important for perception and discrimination
Test for two point determination
1) Subject seated with eyes closed
2) measure tips of bristles at 80 mm apart by ruler and touch the back of the subjects hand with bristles
3) Subject must state if it was one point or two points
4) Reduce the distance and keep testing, and occasionally only allow one bristle to touch the sbject to prevent subject from knowing
5) Once a point where the bristles are detected as ONE STIMULUS rather than two is the TWO POINT THRESHOLD DISTANCE
Test with various areas of body:
Back of hand : 16 mm
Palm: 13 mm
Index fingertip: 1 mm
Forearem: 23 mm
upper arm:36 mm
shin: 27 mm
back of neck: 27 mm
(foundings of E.H Weber )
SHows index has the most sensory nerve endings here
What is the two poiint threshold distance
-distance where a two point stimulus feels like a one point touch
Which areas have the lowest density of sensory endings
-Upper arm
-thighs
-back
Who is known as the father of psychophysics
E.H Weber
german physiologist
What are the sensory cells called that have sensitivity to temperature
thermosensory nerve cells, have terminations as receptor endings as well like touch
Are cold sensitive neurons different from warm sensitive neurons
YEP
in structure and function
How to the receptor ends of thermosensory cells look
-do not branch profusely
-just form a small field (called receptive field that is 1mm in diameter) that is seperate from the fields of other neurons
-concentration of these fields varies from body part to body part
What are the concentration of receptive field of cold sensitive neurons in different body parts such as Lips, finger and trunk
Lips: 15-25 cold points per square cm
Finger: 3-5
Trunk:1 per square cm
In most areas of the body do we have more cold points (receptive fields) or warm
COLD!
almost 3to10x more cold than warm
How to test for cold receptors distnace
Purpose: Determine the spatial limits of that cold reference point
1) get a cold probe and poke the skin, if the subject doesnt feel cold, move it over a bit until they do
2) mark that point and make a matrix array around that point (distance between points is 1 mm)
3)Touch the reference again to mkae sure its right
4) Touch the dots in the matrix, starting from the ones adjacent to the reference, figure out the range of how far the cold can be sensed
RESULTS:
should be able to sense cold 1-2 mm across
How to test for cold receptor concentration
-place grid on hand, it is 2mm by 2mm for each swuare
-use probe and poke each grid with the cold probe
-record what each grid mark is detected as, either cold, only touch or nothing
-replace probe every 2-3 mins to ensure it is still cold
If a subject identifies the feeling of cold when points adjacent to eachother are stimulated it means…
-one receptive field is in play here, not multiple
What are Reflexes and what are the two types and the two classifications
-unconscious actions, not subject to voluntary control
Types-
Spinal reflexes:
-neurons in spinal cord that stimulate and inhibit certain muscles without higher cneters (brain)
Other:
require the transfer fo info to and from brain
Classifications-
a) Visceral: heartbeat, breathing
b)somatic: involving skeletal muscles
c)postural; when its categorizzed by function or location
ie: knee jerk reflex is classified by location as the receptor is a proprioreceptor cell that detects stretching
What is a reflex arc and what does it include
-pathway linking sensory input and motor output
includes
a)Receptor: sensory cell that converts stimulus into action potentials that are passed along the afferent neuron to the spinal cord
b)Effector: motor pathway to bring AP to the muscles or gland
Monosynaptic REflex
when only a afferent neuron and efferent neuron are involved
-diretly synapse together
Spinal Reflexes and the Arcs
1) Knee Jerk Reflex:
hit the patellar tendon with rubber hamer
2) Achiles Jerk
-knees on stool, strike the tendon attached to back of heel
3)Tricep Jerk (radial Nerve)
-strike tendon above elbow on tricep while arm held up with hand downward
Cutaneous Reflex-The Babinski Reflex
-stimulation fo skin recepts on sole of foot
-integrated in the brain, not spinal cord
-has pyramidial cells located in motor cortex, whose axons descend from brain to form synapses in spine with motor neurons
-tests integrity of spine
Responses:
big toe flexes with other toes :normal
big toe points up with other toes: abnormal
Cranial Nerve Reflex
A) Pupillary Light Reflex: shine light into one eye and not the other, note the size of pupils in both eyes
b) Corneal Blink Reflex:
blow stream of air into cornea using a syringe
c) Menace Reflex: pretend to strike partner in the eye
Is the pupillary light reflex consensual (ie does shining light into one eye produce a response on both sides)? What about the corenal blink reflex
YES! Shining light into one eye produces a response in both
Yes, blowing air will cause both eyes to blink and tear
Wht nerves are involved in the pupillary light reflex
Optic nerve (cranial nerve 2) and oculomotor nerve (CN 3)
Why isthe menace reflex different from corneal
-subject can control the response for menace if they are aware whereas they cant for corneal
What is a motor unit
single motor neuron and all of the skeletal muscle cells that it controls
How to control muscles precisely
-having a low ratio of muscle cells to motor neurons gives muscles ability to do this
When more motor units are recruited, less precision is involved. T or F
True!
Lifting a weight and writing your signature will be less precise than just wiriting name with no weights
More motor cells connected to a single neuron allows foe what
i think stuff like heavier loads to be worked.
