Bb W1 L2

Front 1

What is the modality

Back 1

A type of physical phenomenon that can be sensed

Front 2

Types of modalities

Back 2

– Photonic
– Chemical
– Temperature
- Pressure
> auditory
>somatic

Front 3

Somatic pressure sensations can be divided into

Back 3

- externoceptors
- internoceptors
- proprioceptors

Front 4

Types of externoceptors

Back 4

- Meissners corpuscle
- Pacinian corpuscle
- Ruffini's corpuscle
- Merkel's disk
- Free nerve endings

Front 5

Meissners corpuscle

Back 5

– Light touch

Front 6

Pacinian corpuscle

Back 6

– deep pressure
– vibration

Front 7

Ruffini's corpuscle

Back 7

– skin stretch,
– sense of position
– movement

Front 8

Merkel's disk

Back 8

– vibrations at low frequencies

Front 9

Free nerve endings

Back 9

– touch,
– pressure,
– stretch,
– temperature
– pain

Front 10

Internoceptors and proprioceptors

Back 10

Provide information concerning position of the body

Front 11

How we sense a particular modality depends on

Back 11

– The type of receptor
– Where the fibers terminate in the brain

Front 12

Synesthesia

Back 12

A neurological phenomenon in which simulation of one sensory pathway leads to autonomic, involuntary experiences in a second sensory pathway

Front 13

Grapheme

Back 13

Color synesthesia: individual letters and numbers (collectively referred to as graphemes) are shaded or tinged with color
- See a color think of the number, see the number and think of the number in a specific color

Front 14

Possible neural basis for grapheme color synesthesia

Back 14

– Crosstalk between different regions specialized for different functions

Front 15

Receptor/generator potential

Back 15

Depolarization of the receptive portion of the sensory axon caused by application of the sensory stimulus
– The exception is rods and cones which hyperpolarize

Front 16

What are the special senses and which nerves they carried by

Back 16

- olfatory nerve <-- smell
- optic nerve <-- vision
- facial nerve (chorda tympani)<-- taste
- glossopharyngeal nerve <-- taste
- vestibulocochlear nerve <-- hearing and balance

Front 17

What are the general senses and which nerves are they carried by

Back 17

The general senses [somatosensory] are those that are detected from all parts of the body and transmitted to the CNS via
- Trigeminal nerve <-- sensation to the face
- All spinal nerves [except C1]

Front 18

Type of receptors that can be excited to generate an impulse

Back 18

– Mechanical receptors [deformation]
– Chemical
– Temperature
– Electromagnetic [i.e. light]

Front 19

Mechanical receptors

Back 19

By mechanical deformation of the receptor which stretches the membrane and opens ion channels

Front 20

Pacinian corpuscle characteristics

Back 20

– Activated via mechanical D formation
– 20 – 60 concentric lamellae composed of fibrous connective tissue supported by gelatinous material
– Nerve ending located centrally within inner bulb in a fluid filled cavity
- a single afferent unmyelinated nerve ending is activated the stretch

Front 21

Chemical activation of ion channels

Back 21

Chemical binds --> single transduced in cell --> opening of Na channel --> depolarization --> activation of afferent nerve --> Ca influx and release of NT
– Example: taste buds

Front 22

Electromagnetic radiation affect on receptor [Dark]

Back 22

– In the dark, cGMP levels are high and cGMP gates [sodium channels] are open. Positively charged sodium enters the photoreceptor and depolarizes it.
– resting potential is – 40 MV [high compared to most cells]
– Result is tonic release of neurotransmitter in the absence of light

Front 23

Electromagnetic radiation affect on receptor [Light]

Back 23

– In the light, rhodopsin in the outer segment of the rod is stimulated by a photon of light
– Activation of signaling cascade culminating with DECRASED cGMP levels
– CLOSING of cGMP gated sodium channels
– Potassium channels are unaffected and get net HYPERPOLARIZATION of cell to – 70mV
– Reduced neurotransmitter release

Front 24

Modality: intensity

Back 24

Intensity or amount of a sensation depends on the strength of a stimulus

Front 25

Sensory threshold

Back 25

The lowest stimulus intensity a person can detect [Anything about this well elicit an action potential]

Front 26

How can different levels of intensity be transmitted

Back 26

– By sending more impulses along the single fiber [Frequency coding or Temporel summation]
– By increasing the number of Perlow fibers transmit information [Population coding or spatial summation]

Front 27

Modality: duration

Back 27

The relationship between the stimulus intensity and the perceived intensity

Front 28

Adaptation

Back 28

If the stimulus persists for a long time the intensity diminishes

Front 29

Differences in adaptation between cell types

Back 29

– Carotid and aortic baroreceptors may take up to two days to completely adapt
– Pacinian corpuscles adapt to extinction within a few hundreds of the second because of their morphology

Front 30

Modality: location

Back 30

– Ability to locate the site of stimulus
– Ability to distinguish two closely spaced stimuli

Front 31

What is necessary for two point discrimination

Back 31

– Receptor density
– Size of receptive fields

Front 32

Contrast

Back 32

– You need to have at least one receptor between two points to perceive two touches

Front 33

Differences and size of receptive fields and affect on point discrimination

Back 33

– Fingertips have SMALLER receptive fields than the back, so the chance of two touches hitting targets that are at least one receptor way from each other is greater

Front 34

Lateral inhibition

Back 34

– Allows sensory cortex to detect two touches versus one
– lateral inhibition blocks the lateral spread of expiratory signals and therefore increases the degree of contrast in the sensory patterns perceived by the cortex

Front 35

Merkels disc: stimulus, sensation, adaptation?

Back 35

Stimulus: steady indentation
Sensation: pressure
Meditation: slow

Front 36

Meissner's corpuscle: stimulus, sensation, adaptation?

Back 36

Stimulus: low-frequency vibration
Sensation: gentle fluttering
Adaptation: rapid

Front 37

Ruffini's corpuscle: stimulus, sensation, adaptation?

Back 37

Stimulus: rapid indentation
Sensation: stretch
Adaptation: slow

Front 38

Pacinian corpuscle: stimulus, sensation, adaptation?

Back 38

Stimulus: vibration
Sensation: vibration
Adaptation: rapid

Front 39

Hair receptor: stimulus, sensation, adaptation?

Back 39

Stimulus: hair deflection
Sensation: brushing
Adaptation: rapid or slow

Front 40

A(alpha) [Ia] fiber functions

Back 40

– Proprioception
– Stretch
– Primary muscle spindle afferents
– Motor befriend to muscle [extrafusal]

Front 41

A(alpha) [Ib] fiber functions

Back 41

– Contractile fibers: golgi tendon organ efferents

Front 42

A(beta) [II] fiber functions

Back 42

Mechanoreception:
– Discriminative touch
– Pressure
– Joint rotation
– Secondary muscle spindle efferents

Front 43

A(gamma) [II] fiber functions

Back 43

– Muscle spindle intrafusal efferents

Front 44

Relative size + conduction velocities of sensory fibers

Back 44

Ia=Ib > II (Ab) > II (Ay) > III > C

** larger size correlates with faster conduction velocity
** C fibers nonmyelinated