Lab 1 - Neural and Sensory Function

Question 1

What is used to test visual acuity

Answer 1

Snellen chart (letters big to small)

Question 2

What is used to test visual astigmatism

Answer 2

Astigmatism test chart (circle with dark lines)

Question 3

What us used to test for colour blindness

Answer 3

Ichikawa colour vision test (plates with dots of colour forming numbers)

Question 4

What solutions were used to test for taste

Answer 4

5% sucrose (sweet)
5% NaCl (salty)
1% acetic acid (sour)
0.5% quinine sulfate (bitter)
Umami/savory not tested

Question 5

What smells were used to test for olfaction

Answer 5

Peppermint
Crushed garlic

Question 6

What is the difference between tonic and phasic receptors

Answer 6

Tonic: slowly-adapting, produce continuous action potentials as long as the sensation lasts
Phasic: rapidly adapting, detect a stimulus of constant strength and send rapid action potentials decreasing in frequency over time
- Sense stimuli not important to survival (e.g., olfaction)

Question 7

describe the chambers of the eye

Answer 7

 Anterior chamber (in front of the lens):
* filled with aqueous humor (plasma like, low proteins) secreted by ciliary epithelium, drained out of canal of Schlemm (anterior channel)
* supports the lens
* relatively smaller
 vitreous chamber:
* relatively much larger
* filled with vitreous body: clear gelatinous matrix that keeps the eyes shape

Question 8

Describe the neural pathway for visual information

Answer 8

• Neural pathways from the retina to the brain turn electrical signals into visual images
  o Retina to Optic nerve to optic chiasm (some fibers cross to opp side)
  o Synapse at the lateral geniculate body (thalamus)
  o Terminate in the occipital lobe at the visual cortex

Question 9

describe the process of phototransduction and where it occurs

Answer 9

 Phototransduction: conversion of light energy into electrical signals
* Visible light: wavelength 400-750 nanometres
* on the retina From back to front (photoreceptors converge on bipolar cells which converge on ganglion cells which converge on optic nerve)

Question 10

descrive the retina and its function

Answer 10

o Retina: Contains photoreceptors (rods (low-light, blackandwhite) and cones (high acuity and colour vision in light, 20:1)
 Fovea/macula: increased concentration of photoreceptors with the most acute vision
* ONLY CONES
 Criss-crossed with small arteries and veins from the Optic disk
 Phototransduction:

Question 11

describe the external anatomy of the eye

Answer 11

• External Anatomy of the eye:
  o Eye is protected by skull’s bony cavity – the orbit
  o Six extrinsic muscles attached to the eye: control eye movement
  o Cranial nerves: innervate extrinsic muscles
   III
   IV
   VI
  o Upper and lower eyelids
  o Lacrimal apparatus: system of glands and ducts keep eye moist and free of debris (tears via lacrimal gland)

Question 12

what visual tests were performed, describe them

Answer 12

a. Visual acuity: degree of detail the eye can distinguish
b. Astigmatism: blurring/ distortion of the visual image caused by a defect in the lens (decrease ability to focus light)
c. Colour vision:
i. Sensory cells – cones (3 diff types): convert red, green, blue light into electrical signals
ii. Colour blindness: hereditary deficiency in cones (red/green)

Question 13

describe the structure and function of the pupil vs. cornea. vs lens.

Answer 13

• Focuses light on retina (light sensitive) using a lens (cornea) and an aperture (pupil)
  o Pupil: control amount of light let in
   size varies with contraction/relaxation of pupillary muscle ring
   create depth of field: by narrowing and letting less light in
  o Cornea: where light enters
   Transparent disc
   Continuation of the sclera
  o Lens: focuses light on the retina
   Suspended by zonule ligaments
   Transparent disc
   2 convex surfaces

Question 14

what sensory receptors facilitate taste sensation

Answer 14

• Gustation
• Via chemoreceptors
• Taste receptor cells: clustered in taste buds (barrel-shaped groupings of sensory cells on the tongue and lining the mouth)
  o Nonneural cells
  o Membrane channel receptors interact with taste ligands
  o Intracellular Ca¬2+ signal activates primary sensory neuron
• Taste is a combo of 6 sensations:
  o Sweet
  o Sour
  o Salty
  o Bitter
  o Umami (savoury)

Question 15

what sensory receptors facilitate olfaction.

Answer 15

3. Olfaction/smell
   - Via chemoreceptors (chemical sensing)
   - Olfactory sensory neurons in nasal caivity
   o Bipolar neurons
   o Pathway projects directly into olfactory cortex
   o G protein-coupled membrane proteins
   o Phasic receptors

Question 16

How is taste related to smell?

Answer 16

• both use chemoreceptors
• Smell is closely related to taste (decreased ability to taste without smell)

Question 17

describe the function of the ear

Answer 17

o Our perception of energy carried by sound waves.
o Air waves - mechanical vibrations – fluid waves – chemical signals – action potentials
o Sounds waves transmitted through the skull can also be detected
 This is used to diagnose hearing problems in the middle and inner ear
o Neural coding of sound not well understood
 Likely a combo of place-code (different locations along cochlear membrane are read as different pitches, important for high pitch sounds) and temporal-code (timing frequency of APs directly proportional to pitch, important for low pitch sounds) hypothesis

Question 18

What sensory receptors facilitate hearing

Answer 18

o Hair cells/mechanoreceptors
 Tonic control when not bent
 Movement of kinocilium (longer hair-process)
* Left: hyperpolarization of cell = inhibition, no AP
* Right = increase frequency of AP

Question 19

describe the basic structure of the ear (outer, middle, inner)

Answer 19

o Outer ear: sound waves enter ear canal
 Hit tympanic membrane (ear drum) and cause it to vibrate
o middle ear: 3 bones carry vibrations
 malleus
 incus
 stapes – pushes on oval window
o Inner ear: cochlea contains 3 parallel fluid-filled ducts.
 Endolymph: Cochlear duct: contains organ of corti
* Organ of corti: contains neural sensory hair cells (mechanoreceptors) and epithelial support cells
 Perilymph (continuous chamber but 2 distinct sections): vibrations resonate through here
* Tympanic duct: vibrate through duct from endolymph out round window (backwards) for pressure release
* Vestibular duct: vibrate through duct to endolymph

Question 20

describe the neural pathway for sound

Answer 20

o Neural pathway
 Sounds from each ear cross over and right both RL auditory cortex sides
* Timing of sounds btw ears = location of sound
 Some goes to cerebellum
 Synapse in thalamus
 Eventually reach auditory cortex of temporal region

Question 21

What three tests were used for hearing?

Answer 21

a. Rinne’s test
- For Conductive deafness
b. Weber’s test
- For conductive and sensorineural deafness
c. Auditory acuity
- The sensitivity of the auditory system to pick up sound (frequencies for speech tested 250 – 8,000 Hz)

Question 22

describe the Rinne’s test (special sense tested, equipment, setup, results)

Answer 22

• For hearing: Conductive deafness
• requires: Quiet environment, Tuning fork, Cotton
• setup:
  i.Strike tuning fork
  ii. Hold against mastoid process behind ear then move to the auditory opening
  iii. Repeat with cotton
• results:
  i. Normal: air conduction is better than bone. Increased length of sounds recognition through air
  ii. If bone is better = blocked middle ear

Question 23

describe the Weber’s test (special sense tested, equipment, setup, results)

Answer 23

• For hearing: conductive and sensorineural deafness
• Equipment: Moderate background noise environment, Tuning fork, cotton
• setup:
  i. Strike tuning fork
  ii. Hold at midline of skull
  iii. Repeat test with one ear plugged
• results:
  i. Normal: Sound heard equally on both sides
  ii. Hearing loss: on ear is louder

Question 24

describe the auditory acuity test (special sense tested, equipment, setup, results)

Answer 24

• The sensitivity of the auditory system to pick up sound (frequencies for speech tested 250 – 8,000 Hz)
• Equipment:
  i. Tuning fork
  ii. Cotton
• setup:
  i. Close eyes and block one ear
  ii. Strike tuning fork
  iii. Place near ear opening and move away slowly until subject indicates they cant hear it anymore
• results: Normal hearing for speech tested 250 – 8,000 Hz or 10-15 dBs

Question 25

what is glaucoma, what structures does it involve?

Answer 25

Glaucoma (degeneration of the optic nerve) can be caused by increasing intraocular pressure within the anterior chamber Due to blocked outflow of fluid at the canal of Schlemm/anterior channel

Question 26

what are the three types of hearing loss. describe them.

Answer 26

• Conductive: fluid/wax build up of the middle ear blocked transmission of sound waves
• Central: neural pathway damage or cortex damage
• Sensorineural (most common): damage to hair cells due to acute or chronic damage. HAIR CELLS NOT RELPACABLE IN MAMMALS

Question 27

what test is performed to test Equilibrium. describe it (setup, equipment, results)

Answer 27

• The Romberg test
• equipment: blackboard, marker/chalk, timer
  -setup: subject stands close to blackboard. parallel lines are drawn at upper arms. subject stands with eyes open for 2 minutes. examiner notes movement. repeat with eyes closed. repeat entire process with subject at 90 degrees
• results:
  subject deviates body weight side-side 2x more than front-back direction.
  subject tends to lean more forward and have more movement with their eyes closed.

Question 28

what sensory receptors are involved in equilibrium

Answer 28

• proprioceptors: send sensory information to the brain regarding tension of skeletal muscles and position of the limbs
• eyes: provide info about orientation relative to environment
• the vestibular apparatus system of the inner ear: detects position and movement of our head in space. and movement acceleration of the body through space. coordinates eye movement, posture, as well as equilibrium. detected by mechanoreceptors (hair cells) lining fluid- filled chambers

Question 29

what is the neural pathway for equilibrium

Answer 29

• exit vestibular apparatus via vestibular branch of vesbulocochlear (cranial vIII) nerve
• 2nd neuron to medulla to cerebellum (mostly), somatic motor neuron controlling eye movement, and reticular formation (primitive wake cycles)
• to the cerebral cortex

Question 30

What are the main differences between the somatic and specieal senses

Answer 30

• special sense receptors grouped in specialized sensory organs and are relatively more complex/specialized
• somatic sensory receptors widespread through the skin, muscles, and joints

Question 31

What is the difference between touch detection and perception?

Answer 31

detection: occurs at the receptor endings in the skin
perception: conscious realization. Awareness of the stimulus occurs at the somatosensory cortex when the appropriate neurons receive the incoming sensory impulses. each part of the body has its own region of the somatosensory cortex devoted to perceiving touch in that area

Question 32

what are the modalities of the somatic senses

Answer 32

• touch
  -temperature
• nociception (pain/itch sensation)
  -proprioception (both conscious and subconscious)

Question 33

what is the somatosensory pathway? when do the somatic senses cross over the midline?

Answer 33

• synapse on 3 neurons: primary (from stimulus to CNS) - secondary (in the spinal cord grey matter to the thalamus) - tertiary (from the thalamus to the somatosensory cortex -correct region)
• crude/primitive (nociception (itch/pain), temp, coarse touch) senses cross over at the spinal cord and ascend via the spinothalamic tract
• evolved senses (proprioception, vibration, fine touch) cross over at the medulla

Question 34

what factors influence touch sensitivity of a given region of the body. give an example

Answer 34

• # of receptors
• relative size of the region in the somatosensory cortex devoted to the area
  -e.g., lips and fingertips have heightened sensitivity due to the relatively larger region of the somatosensory cortex and the relatively higher number of touch sensory nerve fibers and receptor endings

Question 35

what are the requirements for touch at two separate points on the skin to be perceived by the brain as two distinct stimuli?

Answer 35

1. stimulation of at least two spatially separated touch-sensitive nerve endings
2. nerve impulses triggered by the two separate must travel via 2 different pathways to two separate locations in the somatosensory cortex

Question 36

describe the two-point discrimination of touch test (equipment, setup, results)

Answer 36

• equipment: dividers with 2 bristles attached, ruler with millimetre scale, ‘Minimum Distance for Two-point discrimination’ data sheet
• setup: 1 examiner and 1 subject with eyes closed. move tips of bristles 80 mm apart. lightly touch back of the hand. subject indicates whether they feel 2 points or one. reduce bristle spacing by 10mm until the subject only detects one point (two-point threshold). record the two-point threshold for each area on the chart (back of hand, palm, index fingertip, forearm, upper arm, shin, back of neck)
• results: from least to most sensitive
  1. index fingertip (1mm)
  2. palm of hand (13mm)
  3. back of hand (16mm)
  4. forearm (23mm)
  5. Shin and back of neck (27mm)
  6. outer surface of upper arm (36mm)

Question 37

which surface has the lowest density of sensory endings?

Answer 37

-any area with hair.
- area with highest two-point threshold): outer surface of upper arm has the lowest density of sensory endings

Question 38

what are the advantages of having different densities of touch receptors is different areas of the body

Answer 38

• areas that need to be more touch sensitive (hands and feet) need a higher density than areas that dont require it (upper arm)
  -decrease amount of intense sensory info being transmitted
  -more energy efficient

Question 39

describe the test for mapping cold receptors (equipment, setup, results)

Answer 39

-equipment: ruler, ‘Cold-point testing’ data sheet, extra-fine tip marker, grid stamp, blunt metal probes with thermally insulated handles, cooled fine grain sand to keep probes
- setup: only use probes for 2 mins to keep cool. on the inner forearm touch the probe to the skin until the subject reports a distinct cool sensation. mark this spot with the marker and use the pen to make a matrix of points 1mm apart in a diamond shape. touch the cold probe to these points to determine the spatial limits of cold sensitivity. then stamp a 2cmx2cm grid with 100 squares (2mmx2mm) on the subjects forearm. test all 100 squares with probe and record whether the subject reports “cold point (C)”, “touch (black dot)”, or “no sensation”. repeat for 3 subjects
-results:
field size of cold point: 1-2mm across

Question 40

how does the skin detect temperature?

Answer 40

• thermo-sensory nerve cells with receptor endings specifically sensitive to temperature
• distinct structure and function of cold and warm sensing neurons.
  cold outnumbers warm by 3-10:1
• free nerve endings with small (1mm) receptive field just below the skin
• variation of nerve density varies greatly across the body:
  lips: 15-25 cold points /cm^2
  fingertips: 3-5 cold points /cm^2
  trunk: <1 cold points /cm^2

Question 41

who is known as the father of psychophysics

Answer 41

• E.H. Weber (1795 - 1878)
• physiologist
• used for threshold value table for lab result comparison

Question 42

for cold-point test: if a subject reports the sensation of cold when each of 2 adjacent holes is stimulated, how many receptor fields are likely to be involved? why?

Answer 42

two fields are likely to be involved because a cold receptor can have a receptive field 1-2mm across, and the holes are 2mm each (4mm total).

Question 43

define a reflex, spinal reflex, and reflex arc

Answer 43

• an unconscious action not subject to voluntary control
• spinal reflex: involve the neurons within the spinal cord that inhibition/stimulation of muscle contraction without participation of higher centers (brain). they differ from other reflexes in that others may involve the brain
• reflex arc: fundamental pathway linking sensory input and motor output. includes receptor and effector (monosynaptic reflex)

Question 44

what reflexes were tested?

Answer 44

• knee jerk
• achilles jerk
• triceps/radial nerve jerk

Question 45

how are reflexes defined

Answer 45

• visceral: concerned with heartbeat and breathing or
  somatic: involving the skeletal muscles.
• by location
  -by function

Question 46

what is the sensory receptor responsible for somatic reflexes

Answer 46

proprioceptor (muscle spindle fiber)/ stretch receptor

Question 47

describe the knee jerk spinal reflex test (equipment, setup, results)

Answer 47

• equipt: rubber hammer, coin
• setup: subject sits with feet hanging freely. examiner strikes just below the knee (patellar tendon) with the rubber hammer
• result:
  no coin: reflex occurs
  coin: no reflex occurs because focus and neurons being used to balance coin?

Question 48

describe the achilles jerk spinal reflex test (equipment, setup, results)

Answer 48

equipt: rubber hammer, stool
- setup: subject kneel on stool with foot hanging freely. examiner strikes ankle (achilles tendon)
-result: planar flexation of foot

Question 49

describe the triceps jerk spinal reflex test (equipment, setup, results)

Answer 49

equipt: rubber hammer
- setup: subject sits with horizontal upper arm and lower arm hanging freely. examiner strikes the triceps humoris tendon 2inches above the elbow
result: lower arm swings outward.

Question 50

describe the Babinski reflex

Answer 50

-cutaneous reflex via cutaneous receptors
- integrated in the brain instead of the spinal chord (spinal reflexes)
- response to stimulus carried by pyramidal cells located in the motor cortex who’s neurons extend to the motor cortex of the spine
-tests the integrity of the spine
- line is drawn upward (heel-toe) in an L shape with firm pressure
-normal response: flex/curl of the all toes
-abnormal response: toes curl and big toe extends

Question 51

describe a cranial nerve reflex. what tests are performed? describe them.

Answer 51

• under control of the cranial nerve
  1. pupillary light reflex: consensual reflex (both pupils constrict even though light only shines in one
  2.corneal blink reflex: puff of air on cornea. consensual (both eyes blink)
  3. menace reflex: one partner pretends to hit the other in the eye. normal response is to blink and perhaps move the head back. facial nerve VII and optic nerve III responsible .

Question 52

what allows fine-motor control?

Answer 52

-relatively higher proportion of motor neurons to muscle cells
- result: writing without a load = very fine motor control

Question 53

what allows heavy lifting of loads

Answer 53

1:1 motor neuron to muscle cells
- result: writing name with bag load = less fine motor control but still substantial (name legible)