lecture 13

Question 1

somatic senses

Answer 1

• touch
• temp
• itch
• pain
• proprioception
  —-> goes to primary cortex in parietal lobe where it is perceived

Question 2

if a signal reaches the cerebral cortex

Answer 2

stimulus enters our consciousness

Question 3

if signal does not reach the cerebral cortex

Answer 3

1. stimulus is processed and a movement is elicited w/ out our conscious awareness (heart rate, digestion)
2. not strong enough (not aware)

Question 4

proprioception

Answer 4

awareness of where you are in space (you know you’re sitting)

Question 5

conscious stimulus processing (special senses)

Answer 5

1. vision—> goes to visual cortex in occipital lobe
2. hearing —> goes to auditory cortex in temporal lobe
3. smell and taste —> goes to dedicated region between frontal and temporal lobe
4. equilibrium (balance) —> involves vestibular apparatus in inner ear

Question 6

sensory receptors

Answer 6

• convert stimulus into intracellular response
• the may or may not be neurons
  type of receptor:
  1. chemoreceptor
  2. mechanoreceptor
  3. photoreceptor
  4. thermoreceptor

Question 7

a change in membrane potential of receptor cell

Answer 7

receptor potential

Question 8

when a light photons fall on retina in the eye, rods and cones _________

Answer 8

hyperpolarize

Question 9

when skin is touched, touch receptors _______

Answer 9

depolarize

Question 10

Transduction

Answer 10

Stimulus is converted into an intracellular response

Question 11

Sensory receptors that are neurons

Answer 11

Transduction occurs at the receptor end of primary sensory neurons
Example 1: pain and temperature receptors w/ free nerve endings in the dermis of the skin
- unmylinated
- synapse in dorsal region (gray matter) of spinal cord
- slow
Example 2: Pressure (in closed nerve endings)
- mylinated
- synapse in dorsal region (gray matter) in spinal cord
- fast
In response to their stimulus (pain, temperature, pressure) they produce action potentials

Question 12

Sensory receptors that are not neurons

Answer 12

• Sensory cell is separate from the primary sensory neurons
• special senses (vision, hearing, taste) receptors are cells that release neurotransmitters onto a partner primary neuron to fire an AP (indirectly)
• example: inner ear has hair cells that is caused my finger like projections called cilia that respond when their is mechanical energy
• intracellular response is receptor potential
• exception is olfactory system (smell)

Question 13

stimulus modality

Answer 13

• determined by sensory receptor activated and what area in the brain the sensory signal is sent too
  e.g. when photoreceptors are activated you will perceive light because photoreceptor send signals along visual pathways to visual cortex in occipital lobe
  Label line coding: when you activate a certain receptor (photoreceptor) and that info always goes to the same place (visual cortex) then that info will always be perceived as light
  Example: when u press on your eyes “seeing stars” signal from photoreceptors are always perceived as “light” even if they were activated by another stimulus such as mechanical stress

Question 14

when would you not get 2 point discrimination?

Answer 14

• when all primary neurons converge and synapse onto a single secondary sensory neuron
• convergence creates large receptive fields

Question 15

when would you get 2 point discrimination?

Answer 15

• when each primary neuron has a secondary neuron
• when fewer neurons converge, secondary receptive fields are much smaller

Question 16

perception threshold

Answer 16

minimum stimulus intensity required for activation of all neurons, thus transmission of signal to the brain for perception

Question 17

stimulus location

Answer 17

• the cerebral cortex is highly organized so that specific areas correspond to specific receptive fields
• somatosensory cortex is organized so that information coming from specific regions of the body always go to the same place in the primary sensory cortex
• more cortical= more sensitivity (lips, hands, toes) —> to point discrimination

Question 18

Lateral inhibition

Answer 18

• allows you to detect precisely where a stimulus is
• turns/shuts off neighbouring neurons

Question 19

intensity

Answer 19

coded by number of receptors activated and frequency of action potential

Question 20

duration

Answer 20

• coded by duration of action potential trains
• some receptors can adapt:
  tonic receptors adapt slowly (fire for duration of action potential)
  phasic receptors adapt quickly (fire only when a stimulus changes) —> olfactory neurons

Question 21

Cutaneous

Answer 21

receptors in skin
1. Touch (mechanoreceptors)
- pressure, vibration, sound waves
2. Pain and Itch (nociceptors)
3. Temperature (thermoreceptors)