Peripheral nervous system: afferent division

Question 1

Is the afferent input accurate?

Answer 1

No, it is not highly accurate: 2 outputs for the same picture/stimulus - not a high fidelity recorder

Question 2

What is the afferent input essential for controlling?

Answer 2

It is essential for control of efferent output

• it regulates motor control
• coordinates internal activities for homeostasis

Question 3

The afferent input processing by reticular activating system is critical for what?

Answer 3

arousal and consciousness

Question 4

What are the five important factors the afferent input is responsible for?
(EPPSI)

Answer 4

• essential for control of efferent output (regulates motor control, coordinates internal activities for homeostasis)
• processing by reticular activating system critical for arousal and consciousness
• perception of the environment around us
• storage for future recall
• impact emotions

Question 5

A change detectable by the body, exist in various energy forms (modalities) touch, temp, pain and position

Answer 5

stimulus - generate afferent input

Question 6

What generates an afferent input?

Answer 6

• Stimulus
• detection of adequate stimuli by receptors (not the same as the receptors on the PM of the cells - don’t transduce signal inside cell)
• receptors detecting specialized stimuli may be (specialized ending of afferent neurons, separate cell closely associated with peripheral ending of the neuron)

Question 7

What does generation of afferent input do?

Answer 7

• alters membrane permeability: local depolarization (specialized ending: generator potential, separate cell: receptor potential)
• graded potentials: strength and duration proportional
• converted to action potentials: self-propagated to CNS

Question 8

Where is an AP initiated during receptor stimulation for afferent, efferent, and interneurons?

Answer 8

Afferent neuron: peripheral end of the fiber, close to the receptor

Efferent neuron or interneuron: Axon hillock

Question 9

The intensity of a receptor stimulus depends on?

Answer 9

the frequency of action potentials (stronger stimulus, higher AP frequency)

the number of receptors

Question 10

Tonic receptors (tone)

Answer 10

don’t adapt, or adapt slowly
convey valuable info about stimulus, so receptor shouldn’t adapt or the brain wouldn’t receive info (muscles controlling posture & balance)

Question 11

Stimuli of same intensity does not bring about receptor potentials of the same magnitude from the same receptor

Answer 11

adaptaion

Question 12

Phasic receptors (phase)

Answer 12

• adapts rapidly bby decrease in AP, responds with an off response on removal of stimulus
• important where change in stimulus intensity is important (touch receptors)

i.e. put on ring or watch, feel it initially but not the rest of the day until you take it off

Question 13

The mechanism of receptor adaptation is the same for every receptor. True or false?

Answer 13

FAlse, the mechanism of adaptation varies for different receptors

Question 14

Describe the pacinian corpuscle

Answer 14

• onion - has rings of tissues = concentric layers

- detects pressure and vibrations in the skin

Question 15

How does the pacinian corpuscle rapidly adapt?

Answer 15

mechanical component: layers slip (no longer responsive to stimulus)

electrochemical component: inactivation of sodium channels = no action potential

Question 16

What is a first order transmission of stimulus?

Answer 16

transmit sensory info from the periphery to CNS

- there are different types that convey different messages

Question 17

What is a second order transmission of stimulus?

Answer 17

ascending pathways

• reflex activated
• communicate with various reflex networks and sensory pathways in spinal cord and travel directly to thalamus

Question 18

What is the third order transmission of stimulus?

Answer 18

relay info from thalamus to cerebral cortex (sensory homunculus)

Question 19

What are the three types of nerve fibers for transmission?

Answer 19

Type A
Type B
Type C

type a and b myelinated
type c unmyelinated

Question 20

Put the following in size order based on diameter largest to smallest:
B
C
Aalpha
A beta
A delta

Answer 20

Aalpa (~120m/s) >Abeta > Adelta > B > C (~0.6m/s)

Question 21

What factor do you think affects speed of conduction?

a. thicker myelination
b. greater membrane potential
c. greater diameter
d. stronger AP

Answer 21

C

Question 22

How is acuity of sensation influenced? (AKA discriminative ability)

Answer 22

receptive field

lateral inhibition

Question 23

What is the receptive field?

Answer 23

• circumscribed area of the skin surrounding the somatosensory neuron
• acuity is inversely proportional to the receptive field
  (larger field, smaller acuity)
• small receptive field: more detailed info
• corresponds with sensory homunculus

i. e. can tell two fingers are on face, can’t differ one from two fingers on calf)
- shopping, first instinct to feel with fingers because it is where discriminative ability is the highest

Question 24

What is lateral inhibition?

Answer 24

• most strongly activated signal pathway (center) inhibits the less excited pathwhays from fringe (strong stimulus inhibit small)
• facilitates localization and sharpens contrast (how you k now where forced was applied)
• touch and vision have the most lateral inhibition, so most accurate

(poked with pen)

Question 25

Photoreceptor

Answer 25

respond to visible wavelength of light

Question 26

mechanoreceptor

Answer 26

sensitive to mechanical energy, baroreceptors (blood pressure)

Question 27

thermoreceptor

Answer 27

sensitive to heat and cold, skin

Question 28

osmoreceptor

Answer 28

detect changes in the concentration of solute in body fluids

Question 29

chemoreceptor

Answer 29

sensitive to specific chemicals, concentration of blood O2

Question 30

nociceptor

Answer 30

a pain receptor that is sensitive to tissue damage