S&P - 6 Sensory Systems all flashcards

What happened to Ian Waterman at age 19?

He lost his sense of proprioception from the neck down due to an infection after cutting his finger.

How does Ian Waterman manage to move his limbs?

He must see his limbs and consciously think about moving them.

What somatosensory feeling does Ian Waterman retain?

He retains the somatosensory feeling of temperature.

What is somatosensation?

It refers to mechanical displacement, proprioception, temperature, and pain.

What are the two types of fibers involved in proprioception?

Fast response myelinated fibers and slow response unmyelinated fibers.

What do mechanoreceptors detect?

They detect mechanical changes such as pressure and vibration.

What is the difference between fast adapting (FA) and slow adapting (SA) receptors?

FA receptors respond at the onset and offset of a stimulus, while SA receptors respond throughout the duration of a stimulus.

What type of mechanoreceptor is responsible for sustained pressure detection?

Merkel's disks.

What do Meissner's corpuscles detect?

Temporal changes in skin deformation and low-frequency vibrations.

What is the role of Pacinian corpuscles?

They detect high-frequency vibrations and temporal changes in skin deformation.

What do Ruffini endings respond to?

Sustained downward pressure, lateral skin stretch, and skin slip.

What are receptive fields in somatosensation?

Areas of skin that, when stimulated, activate specific sensory neurons.

What is the difference between small and large receptive fields?

Small receptive fields provide high tactile acuity, while large receptive fields have lower spatial resolution.

What types of neurons are involved in proprioception?

Group 1a and 1b sensory neurons.

What is the function of muscle spindles?

They act as stretch receptors and are involved in detecting changes in muscle length.

What do gamma motor neurons do?

They adjust spindle sensitivity by contracting intrafusal fibers.

What is the myotatic reflex?

A reflex that causes a muscle to contract in response to being stretched.

What is the reverse myotatic reflex?

A reflex that protects against muscle overload by inhibiting alpha motor neurons.

What sensory inputs are necessary to maintain posture?

Proprioception, cutaneous receptors, visual input, and vestibular system input.

What is the anticipatory feed forward mechanism?

A conscious adjustment of balance before movements.

What is the compensatory feedback mechanism?

Unconscious adjustments of body position when balance is lost.

What factors help maintain posture?

Pressure receptors in the foot, muscle, and joint receptors.

What is sarcopenia?

Age-related loss of muscle mass that can affect balance.

How does aging affect postural adjustments?

It results in slower muscle spindle responses, making it harder to correct posture.

What is the significance of watching the Baby Body Sense video?

It illustrates how babies learn to move to targets using proprioceptive feedback, similar to how individuals like Ian must learn to move.

What are the otolith organs and their function?

The utricle and saccule, which detect linear acceleration and head position relative to gravity.

What do semicircular canals detect?

They detect rotational acceleration.

What is the vestibulo-ocular reflex (VOR)?

A reflex that coordinates head position with eye movements to maintain visual field orientation.

What happens to hair cells in the semicircular canals when bent towards the kinocilium?

They produce an excitatory response, increasing the firing rate.

What is the role of the vestibulocollic reflex?

It acts on the neck to counteract head movements and keep the head upright during body tilts.

What is the function of the vestibulospinal reflex?

It prepares the limbs for landing during falls.

What is congenital analgesia?

A condition where an individual has insensitivity to pain.

What is the gate control theory of pain?

Pain perception is modulated by a gate mechanism in the spinal cord, where an open gate increases pain and a closed gate reduces pain.

What are nociceptors and their types?

Pain receptors; A-delta fibers transmit sharp, localized pain, while C fibers transmit dull, aching pain.

What is the spinothalamic pain pathway?

A pathway transmitting pain from the dorsal horn of the spinal cord to the thalamus and then to the somatosensory cortex.

What is the spinoreticular pain pathway?

A pathway transmitting pain to the reticular formation in the brainstem, influencing emotional responses.

What neurotransmitter transmits pain signals?

Substance P.

What are the four aspects of illness behavior?

Symptom perception, symptom interpretation, symptom expression, and coping behaviors.

What is the role of proprioceptive feedback in movement?

It provides information about limb position and tension for accurate movement execution.

What is the impact of large fiber sensory neuropathy on movement?

Grossly inaccurate rapid movements to targets due to lack of feedback.

What is the primary function of hair cells in the vestibular system?

Detect changes in head position and motion for balance and orientation.

What does the vestibular system coordinate?

Balance, motor responses, eye movements, and posture.

What is the emotional aspect of pain?

Pain is an unpleasant sensory and emotional experience linked to actual or potential tissue damage.

What is the difference between pain tolerance and pain endurance?

Pain tolerance is when pain becomes intolerable; pain endurance is the difference between tolerance and threshold.

What are Brodmann's Areas?

Regions of the cerebral cortex are defined by distinct cellular organization by respective functions.

How do patients with prefrontal lobotomies respond to pain?

They live in the present, lack awareness of prolonged pain, and do not fear future pain.

What is pain asymbolia?

Normal pain perception without emotional or behavioral response due to cortical lesions.

What is pain empathy and which brain region is necessary for it?

The ability to feel others' pain, requiring the anterior insular cortex.

What is the definition of acute pain?

Pain lasting less than 3 months.

What is chronic pain?

Pain lasting longer than 3 months and affecting about 20% of the world population.

What is neuropathic pain?

Pain that persists after tissue injury or nerve damage.

Why has the placebo response increased over time?

Longer study durations enhance expectation-driven effects.

What is addiction in the context of opioids?

Dependence on a drug that is difficult to stop due to withdrawal.

What is tolerance in relation to opioids?

Reduced drug effectiveness over time requiring higher doses.

What are the three types of opioid receptors?

Mu, delta, and kappa receptors.

What is the mechanism of action of opioids in the CNS?

Opening K+ channels causing hyperpolarization and blocking pain signals.

What is the placebo effect?

Symptom improvement due to expectation rather than treatment.

What are nocebos?

Expected negative effects that cause distress or illness.

What are the two necessities for placebo analgesia?

Desire for pain relief and expectation of relief.

How can placebo analgesia be blocked?

By the opioid antagonist naloxone.

What is the significance of the anterior insular cortex in pain empathy?

Damage prevents empathy for others' pain.

What is the role of the periaqueductal gray in pain modulation?

It contains many mu receptors and mediates descending pain inhibition.

What is the impact of chronic pain on emotional response?

Chronic pain heightens emotional responses.

What historical significance does morphine have?

Isolated in 1806 and widely used during the US Civil War.

Human range of visible light (in nm)

400-700 nm

Number and names of cone/rod types

3 cone types (L, M, S wavelength-sensitive cones) and rods

What is vision like with just rods?

Black/white; non-functional in bright light due to photobleaching; monochromat

Principle of Univariance

A single photoreceptor system responds only to light intensity, not wavelength

Monochromacy, dichromacy, trichromacy

Having 1, 2, or 3 functional cone types and rods

What does the world look like to a protanope?

Missing L cones; cannot see red; world looks mostly green/blue

What does the world look like to a deuteranope?

Missing M cones; cannot see green; world looks mostly red/blue

What does the world look like to a tritanope?

Missing S cones; cannot see blue; world looks mostly red/green

What are color matching experiments?

Adjusting intensities of three primaries (R, G, B) to match a test light → demonstrates trichromacy and metamers

What is a metamer?

Different wavelength compositions that appear as the same color

Why are men more often colorblind than women?

L/M opsin genes are on the X chromosome; men (XY) are hemizygous so mutations express

Why does colorblindness differ across races?

The theory is that the longer a society has been industrialized, the less selective pressure there is against colorblindness.

Achromatopsia

Rod monochromacy; no functional cones due to CNGA3 or CNGB3 channel mutations

Squirrel monkeys' color vision

All males are dichromats, some females trichromats due to X-linked opsin alleles

Cats and dogs' color vision

Rod-rich retinas; reflective tapetum lucidum for night vision

Coelacanth

Fish with 2 rod types; may permit color discrimination without cones

Shiny and black loosejaws

Deep-sea fish using red bioluminescence; chlorophyll-like pigment extends sensitivity

Bees' color vision

See UV and preferentially seek UV-reflecting surfaces

Snakes' color vision

Pit organs allow long-wavelength/infrared detection

House mice's color vision

Dichromats; cones coexpress UV and M; retinal top-bottom gradient matches environment

Whales' color vision

Monochromats; have 5 opsin genes but none are expressed

Pigeons' color vision

Tetrachromats with oil droplets in cones to filter light

Goldfish's color vision

Exhibit color constancy; can perceive true color regardless of illumination

Monarch butterflies' color vision

UV, blue, green cones; orange pigment in ommatidia enables orange discrimination

Reindeer's color vision

Seasonal changes in tapetum lucidum to optimize sensitivity in summer vs winter light

Tetrachromacy in some human women

Protanomaly can yield two L-cone variants plus normal S and M cones (4 total)

Nystagmus

Involuntary eye oscillation; in achromats, no cones → no fovea → unstable fixation

Photobleaching

Rods saturate and lose function in bright light; achromats blinded in daylight

Phototransduction mechanism

Photon absorbed; chromophore straightens; cascade lowers cGMP; CNG channels close; hyperpolarization → signal

Cone cation channel composition

2 CNGA3 and 2 CNGB3 subunits; mutations cause achromatopsia

Pingelapese condition

Rod monochromacy (achromatopsia) due to CNGA3/CNGB3 mutations

Gene therapy's effects on achromatopsia (general)

Targeting CNGA3/CNGB3; some improvement in acuity and photoaversion, limited color vision recovery

Opponent mechanisms (general)

Color encoded by comparing cone activities in opponent pairs (R/G, B/Y, L/D)

Red-green opponent mechanism

Difference of L vs M cones; mediated by midget ganglion cells

Blue-yellow opponent mechanism

Difference of S vs (L+M) cones; mediated by small bistratified ganglion cells

Light-dark (luminance) opponent mechanism

Pooled L+M cone input vs lack of stimulation; mediated by parasol ganglion cells