Ch 3 - Neurophysiology

Question 1

Decussations

Answer 1

They are crossing fibers
We have:
  -Anterior white commissure
  -Internal arcuate fibers
  -Corpus Callosum (connects L&R side of the brain)
  -Anterior & Posterior Commisure

Question 2

The greater the degree of myelination ->

Answer 2

Means increased diameter which means increased conduction

Question 3

Typical Sensory pathways

Answer 3

Sensory receptors; 1st order neurons -> 2nd order neurons -> 3rd order neurons -> 4th order neurons -> cortex

Question 4

Sensory Transduction

Answer 4

Environmental stimulus (e.g., pressure, light, chemicals) activating a receptor, altering the membrane potential (receptor potential) via opening/closing of ion channels, and increasing the chances of an AP which is then conducted as an impulse/signal

Question 5

Opening of channels & current flow

Answer 5

Receptor potential or generator potential

Question 6

Inward flow

Answer 6

Depolarization. Membrane potential moves toward threshold and increases the likelihood of an AP

Question 7

Outward flow

Answer 7

Hyperpolarization. Membrane potential moves away from threshold, decreasing the likelihood of an AP

Question 8

Definition of Receptive Fields

Answer 8

Area of the body that when stimulated results in a change in firing rate of a sensory neuron

Question 9

Types of Receptive Fields

Answer 9

Excitatory: increases in the firing rate of a sensory neuron
Inhibitory: decreases in the firing rate of a sensory neuron

Question 10

The smaller the receptive field…

Answer 10

The more precise

Question 11

Lateral Inhibition

Answer 11

Is a protective mechanism which increases precision of sensory localization by defining its boundaries & providing a contrasting border

Question 12

Stimulus Modality

Answer 12

Pathways are specific to sensory type

Ex: your eyes are not hearing or your nose is not seeing

Question 13

Stimulus Location

Answer 13

Encoded by the receptive field

Enhanced by lateral inhibition

Question 14

Threshold

Answer 14

Minimum stimulus that can be detected by receptive field to produce an AP

Question 15

Stimulus Intensity is encoded by these 3 methods

Answer 15

1. Based on # of receptors activated
2. Based on firing rates of neurons
3. Based on type of receptor activated; ex: light touch; mechanoreceptor & intense dragging stimulus; nocioceptors

Question 16

Adaptation of Sensory Receptors

Answer 16

Being desensitized by long exposure to stimulus

Question 17

Phasic Receptors

Answer 17

Pacinian corpuscle; light touch & vibration; rapidly adapting

Question 18

Tonic Receptors

Answer 18

Muscle spindle, merkel’s receptors; steady pressure or slow pain; slowly adapting

Question 19

Thermoreceptors

Answer 19

Slowly adapting receptors

Detect skin temperature

Question 20

Warm vs Cold Thermoreceptors

Answer 20

Warm: Optimal @ approximately 42-43 C; Quiescent @ 45 C

Cold: Optimal @ approximately 30 C; Quiescent @ below 25 C

Both function @ approximately 36 C

Question 21

Nociceptors

Answer 21

• Respond to noxious stimuli that can produce tissue damage

Question 22

Types of Nociceptors

Answer 22

Mechanical: Respond to mechanical stimuli such as sharp, pricking pain. Supplied by finely myelinated A-delta fibers which allow for medium conduction

Polymodal: Respond to high-intensity mechanical or chemical stimuli and hot and cold stimuli. Supplied by unmyelinated C fibers which allow for slow conduction

Question 23

Fast pain

Answer 23

• Carried by group II and group III fibers
• Rapid onset & offset
• Precise localization
• Ex: pin prick

Question 24

Slow pain

Answer 24

• Carried by C fibers
• Characterized as aching, burning, or throbbing pain
• Poorly localized
• Ex: burn

Question 25

Referred pain

Answer 25

• Of visceral origin
• Pain is “referred” according to the dermatomal rule, which states that sites on the skin are innervated by nerves arising from the same spinal cord segments as those innervating the visceral organs
• Ex: Ischemic heart pain is referred to the chest & shoulder

Question 26

Examples of Phasic Receptors

Answer 26

Pacinian Corpuscles; light touch & vibration

Question 27

Examples of Tonic Receptors

Answer 27

Muscle spindles, merkel’s receptors; steady pressure or slow pain

Question 28

Mechanical Nociceptors respond to

Answer 28

Respond to mechanical stimuli such as sharp, pricking pain

Question 29

Polymodal Nociceptors respond to

Answer 29

Respond to high-intensity mechanical or chemical stimuli and hot and cold stimuli

Question 30

Fast pain are carried by which fibers?

Answer 30

Group II & III fibers

Question 31

Slow pain is carried by which fibers?

Answer 31

Group C fibers

Question 32

Are thermoreceptors fast or slow adapting?

Answer 32

Slow