intro to sensory

Question 1

define exteroceptor

Answer 1

• receptor that relay whas is happening in the external environment (touch, hearing, taste, olfaction, vision)

Question 2

define interoceptor

Answer 2

• relays what is happening in the internal environment

Question 3

define proprioceptor

Answer 3

• relay what is happening in the musculoskeletal system

Question 4

define transduction

Answer 4

• process by which energy of physical stimulus is detected and CONVERTED into a form of energy used by nervous system
• physical stimulus CONVERTED into RECEPTOR POTENTIAL in a specialized receptor cell or sensory receptor ending

Question 5

define adequate stimulus

Answer 5

• under normal circumstances a specific receptor is affected by only one stimulus modality (this is adequate stimulus)

Question 6

define nociceptor

Answer 6

pain receptor (noxious)

Question 7

define receptive field

Answer 7

• region of tissue within which a stimulus can evoke a change in the firing rate of a neuron

Question 8

receptor potential vs action potential

Answer 8

• Receptor potential = CHANGE in membrane potential produced by a transducer mechanisms (is a LOCAL, GRADED POTENTIAL)
• Most receptor potentials are depolarizations
• IF DEPOLARIZATION reaches Threshold, an ACTION POTENTIAL is generated
• rate of action potential generation INCREASES as receptor potential rises higher above threshold

Question 9

How does the nervous system code for “what”

Answer 9

• labeled line principle = receptors/neurons code for specific stimuli

Question 10

how does the nervous system code for Where

Answer 10

• receptor field of a neuron is the region of tissue within which a stimulus an evoke a change in firing
• sensory pathways create a somatotopic maps
• lateral inhibition is a way to enhance boundary contrasts.

Question 11

how does the nervous system code for intensity

Answer 11

• signal strength increases by:
• -> increasing frequency of nerve impulses (TEMPORAL SUMMATION) = frequency)
• -> increasing the # of fibers activated (spatial summation = population)
• Stimuli of different intensities may activate different sets of sensory receptors

Question 12

how does the nervous system code for duration

Answer 12

• maintain continuous signal during stimulus

- have on and off signal

Question 13

define adaption of receptors

Answer 13

• maintained stimulus of constant strength is applied to a receptor, the frequency of AP in receptors sensory nerve decreases over time
• -> general property of sensory receptors
• -> receptors have different mechanisms of adaption
• -> probably all mechanoreceptors would completely adapt eventually

Question 14

describe Non-adapting

Answer 14

• often lumped with tonic receptors

- NOCICEPTORS

Question 15

describe slowly adapting (TONIC)

Answer 15

• give continuous info about stimulus (STRENGTH + DURATION)
• not useful at low stimulus intensities
• MERKEL CELL ENDINGS (disks), Ruffini end organ, Baroreceptors

Question 16

describe rapidly adapting (PHASIC)

Answer 16

• Useful for signaling begining and end of stimulus
• change in stimulus intensity
• # of APs transmitted related to rate at which change is taking place
• extract dynamic info (VELOCITY and ACCELERATION)
• Predictive function
• Can NOT give continuous signal in response to continuous stimuli
• PACINIAN CORPUSCLES, MEISSER’S CORPUSCLES

Question 17

A-alpha (type I)

Answer 17

• 100m/s
• myelinated
• Alpha motor neuron (muslce)
• Spindle primary endings (Ia)
• golgi tendon organ afferent (Ib)

Question 18

A-beta (type II)

Answer 18

• 50m/s
• myelinated
• Muscle spindle secondary endings (II)
• cutaneous mechanoreceptors

Question 19

A-Sigma (Type III)

Answer 19

• 20m/s
• myelinated
• Fast pain
• some temperature receptors

Question 20

• C type (Type IV)

Answer 20

• 1m/s
• NOT myelinated
• slow pain
• some temperature

Question 21

describe proprioception receptors

Answer 21

• sense important for BALANCE, Control of LIMB MOVEMENT, SHAPE of GRASPED OBJECT
• Joint position = static proprioception
• Joint movement = dynamic proprioception
• JOINT RECEPTORS, MUSCLE SPINDLE and GOLGI TENDON ORGANS, SKIN TACTILE RECEPTORS

Question 22

Dorsal column

Answer 22

• fine tactile discrimination, vibratory and proprioception, precise, visceral pain pathway
• decussates in brainstem (medial lemniscus)

Question 23

Anterolateral spinal cord pathway

Answer 23

• conveying nociceptive and thermal sensation
• some tactile info
• Decussates in spinal cord