CNS 2

Question 1

The structure of a sensory receptor determines which

Answer 1

modality of stimulus it responds to.

Question 2

The modality activating a given receptor is called that receptor’s

Answer 2

adequate stimulus.

Question 3

Different modalities are processed in different

Answer 3

brain regions ( eg. Sensory cortex, visual cortex).

Question 4

Specific types of mechanosensory stimulation are transduced by specific types of receptor cells

Answer 4

A: Tactile (Meissner’s) corpuscle (Light touch)

B: Tactile (Merkel’s) corpuscle (Touch)

C: Free nerve ending (Pain)

D: Lamellated (Pacinian) corpuscle (Vibration and deep pressure)

E: Ruffini corpuscle (Warmth)

Question 5

Sensory receptors are either:

Answer 5

a. Specialized endings of afferent axons ( eg. Skin and muscle receptors)
b. Separate cells that respond to the stimulus and transmit signals via synapses with the afferent neurons (eg. Cochlear hair cells, retinal photoreceptor cells)

Question 6

Several million neurons from body to CNS, signaling:

Answer 6

1) mechanoreceptors
2) thermoreceptors
3) nocireceptors (pain)
4) proprioceptors
5) vestibular receptors

Question 7

Ve s t i b u l a r receptors

Answer 7

Head acceleration and tilt

Question 8

Proprioceptors

Answer 8

Movement & force in muscles & joints

Question 9

Nociceptors

Answer 9

Pain (tissue damage) in skin, viscera, muscle

Question 10

Thermoreceptors

Answer 10

Temperature in skin & brain

Question 11

Mechanoreceptors

Answer 11

Local tissue deformation in skin & viscera

Question 12

Sensory receptors signal stimuli with action potentials in widely

Answer 12

ranging species (Invertebrates, vertebrates including humans).

Question 13

The coding mechanism of information transfer in nervous systems (Pulse rate modulation) must have evolved before

Answer 13

Invertebrates and vertebrates diverged

Question 14

How many types of sensory axons types

Answer 14

• la (myelin): muscle spindle primary ending
• lb (myelin)
• lll (thin myelin)
• IV (none): nocirecpetors (ache) and warmth thermoreceptors

Question 15

Motor axon types

Answer 15

• a : (myelin): extrafusul ,muscle fibres

- y : (myelin): intrafusal muscle fibres

Question 16

Autonomic axon types

Answer 16

• Preganglionic fibres (Myelin) thick

- Postganglionic fibers (myelin) thin

Question 17

As stimulus intensity increases, the membrane potential at the initial segment of the sensory receptor’s afferent axon

Answer 17

increases until action potentials are generated.

Question 18

Further increases cause increases in

Answer 18

action potential rate and the recruitment of more sensory receptors.

Question 19

Changes in regularity of firing rates may also encode

Answer 19

stimulus properties.

Question 20

Frequency code:

Answer 20

the bigger the stimulus, the more the membrane channels in the sensory ending are distorted, the greater the number of action potentials/sec (AP/s)

Question 21

Population code:

Answer 21

the bigger the stimulus, the more sensory neurons are recruited into activity, so the more AP/s

Question 22

Temporal pattern code:

Answer 22

variability of firing rate (bursts vs steady firing) may mediate certain types of sensation

Question 23

Duration

Answer 23

Slowly adapting (tonic) receptors respond the entire time a stimulus is applied.

Question 24

Adaptation:

Answer 24

reduction in response (number of

action potentials/sec) in continuous presence of a stimulus

Question 25

Different sensory receptors vary in

their

Answer 25

speed of adaptation to stimuli