KIN 103 (Chp: 10 - Neurons)

Question 1

What are the three types of neurons? (Simple neuron)

Answer 1

• may or may not have myelinated axons
• free nerve endings

Question 2

What are the three types of neurons? (Complex neuron)

Answer 2

• enclosed nerve endings
• connective layers of tissue around them (Pacinian corpuscle)
• myelinated axons
• usually for sensing touch

Question 3

What are the three types of neurons? (Special neurons)

Answer 3

• Specialized receptor hair end
• Synaptic vessicles
• synapses
• myelinated axons
• usually for the senses of the body

Question 4

Adequate stimulus:

Answer 4

Adequate stimulus: each type of receptor responds preferentially to a particular type of stimulus or form of energy.

Question 5

Chemoreceptors

Answer 5

stimulated by: oxygen, pH, organic molecules

Question 6

Mechanoreceptors

Answer 6

Stimulated by: pressure, cell stretch, vibrations

Question 7

Photoreceptors

Answer 7

Stimulated by: Photons of light

Question 8

Thermoreceptors

Answer 8

Stimulated by: Varying degrees of heat

Question 9

Transduction

Answer 9

Transduction: stimulus energy converted into information processed by CNS, ion channels or second messengers initiate membrane potential change in sensory receptor (graded potentials)

Question 10

Receptor potential:

Answer 10

Receptor potential: change in membrane potential of sensory receptor (graded potential), can initiate action potentials or release neurotransmitter

Question 11

Threshold

Answer 11

Threshold: minimum stimulus required to generate large enough receptor potential to initiate action potentials (or release neurotransmitter)

Question 12

Receptive field

Answer 12

Receptive field: neurons are activated when stimuli fall within a specific physical area (i.e. region on the skin or on the retina)

Question 13

Primary and secondary sensory neurons (which have larger sensory fields?)

Answer 13

Primary and secondary sensory neurons have primary (smaller) and secondary (larger) receptive fields, respectively.

Question 14

Do secondary receptive fields overlap?

Answer 14

Yes they do, in fact secondary receptive fields are a combination of primary receptive fields in a said area

Question 15

Two point discrimination

Answer 15

Essentially the principle that when we touch two places on someone’s skin it may trigger a feeling of only one place since the neurons go through convergence

Question 16

Modalities (what are they?)

Answer 16

Different types of information (modalities) are processed in different regions of the brain

Question 17

Does all sensory information reach the brain?

Answer 17

Some information does not reach the brain, eg: Visceral reflexes are integrated in brain stem or spinal cord and usually do not reach conscious perception (eg. control of blood pressure)

Question 18

What type of pathways does sensory information travel through?

Answer 18

Most sensory information travels from the body to the brain along ascending pathways in the spinal cord or from the head to the brain via cranial nerves

Question 19

Four properties of all stimuli: (What are they?)

Answer 19

Modality, location, intensity, duration

Question 20

Modality (Definition)

Answer 20

Modality: What kind of stimulus is it (touch, sound, light)?
- indicated by which sensory neurons are activated and where those neurons terminate in brain
- specific to receptor type (adequate stimulus)

Question 21

labeled line coding (what is it?)

Answer 21

labeled line coding
- 1:1 association of receptor with sensation
- Each type of receptor projects to a specific part of the brain.

Question 22

Lateral inhibition (what is it?)

Answer 22

Lateral inhibition: increases contrast between active receptive fields and inactive neighbors (slide 13)

Question 23

Population coding (what is it?)

Answer 23

Population coding: the CNS evaluates input from multiple receptors to obtain more information than can be provided by a single receptor (slides 7, 12, 13)

Question 24

Intensity

Answer 24

Intensity = frequency of APs (frequency coding) and number of receptors activated (population coding)

Question 25

Duration

Answer 25

Duration = duration of AP discharge “train” and resulting neurotransmitter release.

Question 26

Tonic receptors

Answer 26

Tonic receptors: are slowly adapting receptors that responds for the duration of the receptor - Provides continuous feedback as long as the stimulus is applied (eg. Baroreceptors, proprioceptors)

Question 27

Phasic receptors

Answer 27

Phasic receptors: rapidly adapt to a constant stimulus and turn off, they fire once more when stimulus turns off - Signals and on and an off - "event detectors"

Question 28

Modality (its 4 types)

Answer 28

- Touch - Proprioception - Temperature - Nociception - Pain - Itch

Question 29

Where do fine touch and proprioception synapse in the CNS?

Answer 29

- They synapse in the medulla - once more in the thalamus

Question 30

Where do nociceptors and course touch senses synapse in the CNS?

Answer 30

- They synapse in the dorsal root of the spinal cord - once more in the thalamus

Question 31

What is important to note about sensory pathways?

Answer 31

- they all enter from one side (either left or right) and contact the opposite side of the brain

Question 32

Tertiary sensory neurons (where do they terminate?)

Answer 32

- They terminate in the somatosensory cortex

Question 33

Somatosensory cortex

Answer 33

- Within it the body is mapped - The maps created are "plastic" and can change over time and with use - The amount of space each part has in the somatosensory cortex is proportional to the sensitivity of the part

Question 34

The axons of Somatosensory neurons differ for each their purposes (what are these differences? - A(beta)

Answer 34

A(beta) - Large, myelinated - Fast conduction - Mechanical stimuli

Question 35

The axons of Somatosensory neurons differ for each their purposes (what are these differences? - A(delta)

Answer 35

A(delta) - Small, myelinated - Medium speed - Cold, fast pain, mechanical stimuli

Question 36

The axons of Somatosensory neurons differ for each their purposes (what are these differences? - C)

Answer 36

C - Small, unmyelinated - Slow speed - Slow pain, heat, cold, mechanical stimuli

Question 37

Merkel receptors (What are they?)

Answer 37

Merkel receptors: sense steady pressure and texture

Question 38

Meissner's corpuscle

Answer 38

Meissner's corpuscle: responds to flutter and stroking movements

Question 39

Pacinian corpuscle

Answer 39

Pacinian corpuscle: sense vibration

Question 40

Ruffini corpuscle

Answer 40

Ruffini corpuscle: responds to skin stretch

Question 41

Temperature Receptors

Answer 41

- Located throughout the body - Play a role in homeostasis - In the skin they are free nerve endings located in subcutaneous layers - Cold receptors - Activated at temperatures below body temperature - Warm receptors - Activated above body temperature to about 45°C - Pain receptors activated above 45°C

Question 42

Nociceptors (Definition)

Answer 42

Nociceptors are free nerve endings that respond to strong chemical, mechanical, thermal stimuli that may damage tissue (Fig 10.10)

Question 43

Pain (Definition)

Answer 43

Pain is our subjective perception of the activation of nociceptors. - Fast pain, sharp and localized (Adelta fibers) - Slow pain, more diffuse (C fibers) (see Table 10.3)

Question 44

Itch (Definition)

Answer 44

Itch is our subjective perception of the activation of nociceptors in the skin

Question 45

How can Nociceptor discharge be altered?

Answer 45

- Nociceptor discharge can be altered by local chemicals ○ Chemicals that mediate inflammatory response (histamine, serotonin) increase nociceptor discharge by activating the receptor or decreasing their threshold ○ Leads to inflammatory pain, increases sensitivity to pain at inflammation site

Question 46

Nociceptor pathways (Reflex pathway)

Answer 46

Reflex pathways through the spinal cord produce an integrated “withdrawal” response...

Question 47

Nociceptor pathways (Ascending pathway)

Answer 47

Ascending pathways to the brain (Fig. 10.8) mediate conscious sensation (pain or itch) and can initiate autonomic responses (nausea, sweating).

Question 48

Referred pain (What is it?)

Answer 48

Referred pain: pain from a heart attack is often felt in the neck, shoulder and left arm - Because they share a common secondary field receptor - (THIS HAS A LOT TO DO WITH THE TWO POINT DISCRIMINATION)

Question 49

Pain control (gate modulation theory)

Answer 49

Essentially the theory that there are C neurons connected to an inhibitory gate that opens when a signal is fired but close when there is no signal firing (NEURONS CAN TURN ON AND OFF INHIBITORY NEURONS)