Biol 235 - Chapter 10: Sensory Physiology

Front 1

Characteristics of Specialized Senses

Back 1

1. specialized receptors

2. localized to a specific region (head)

Front 2

Specialized Senses

Back 2

Vision

Hearing

Taste

Smell

Equilibrium

Front 3

Somatic Senses

Back 3

Touch

Temperature

Pain

Itch

Proprioception

Front 4

Basic Sensory Pathway

Back 4

Stimulus

Sensory receptor (transducer)

Intracellular signal (change in memb potential)

Afferent (action potential to CNS)

Integration in CNS

Efferent

Target Cell

Response

Front 5

Sensory Receptor Types

Back 5

Chemoreceptors: O2, pH, organic molecules

Mechanoreceptors: pressure, stretch, vibration,

- Baroreceptors: vessel pressure

- Osmoreceptors: osmatic pressure

Photoreceptors: photons of light

Thermoreceptors: heat

Nocioceptors: tissue damage (pain and itch)

Front 6

General Classification of Receptors

Back 6

Interoceptors: monitors internal

Proprioceptors: background position of jts and muscles. Awareness of body position in space.

Exteroceptors: monitors external

Front 7

Receptive Field

Back 7

Area monitored by each receptor.

Can overlap with other receptors.

Front 8

Receptive Field Convergence

Back 8

Multiple primary neurons (receptors) converge onto a single secondary neuron.

Front 9

Increased Sensitivity

Back 9

1:1 relationship between primary and secondary neuron.

Front 10

Lateral Inhibition

Back 10

Increases contrast between activated receptive fields and inactive neighbors.

2ndary neuron suppresses response of weaker, lateral neurons

i.e. vision - sharpens perception of visual edges

Front 11

Primary Sensory Neuron

Back 11

Receptor neuron

Front 12

Secondary Sensory Neuron

Back 12

CNS neuron.

Receives info from primary neuron and travels to CNS

Front 13

Gray Matter

Back 13

Location: cortex and nuclei of brain, horns of spinal cord

Function: information processing

Unmyelinated

Front 14

White Matter

Back 14

Location: not in cortex and nuclei of brain, columns of spinal cord

Function: information pathway

Myelinated

Front 15

Perceptual Threshold

Back 15

Level of stimulus needed in order to be aware of a particular stimulus

Front 16

Integration of Sensory Information by Brain

Back 16

Primary neuron to secondary neuron.

Ascends tracts to brain or directly via cranial nerves.

Visceral reflexes are not consciously perceived.

Front 17

Stimulus Properties

Back 17

Allows for CNS to differentiate between stimulus

Dependent on which receptors activated:

1) Modality: nature of stimulus

2) Location

Dependent on pattern of APs:

3) Intensity: # of receptors activated and frequency of AP (frequency coding)

4) Duration: longer series of APs

Front 18

Adaptation of Receptors

Back 18

Receptors can adapt or cease to respond if a stimulus continues to persist.

Tonic receptors

Phasic receptors

Front 19

Tonic Receptors

Back 19

Slow adapting receptors that fire rapidly when 1st activated then slow and maintain firing as long as the stimulus exists.

i.e. receptors in bld vessels under constant monitoring.

Front 20

Phasic Receptors

Back 20

Fast adapting receptors that fire when 1st receive stimulus but cease to fire if strength of stimulus remains constant.

Attuned to changes in parameter.

Allows CNS to filter out extraneous info

i.e. smell, cologne strong in the morning but later no longer smell.

Front 21

Somatosensory Modalities

Back 21

Touch

Proprioception

Temperature

Nociception

Front 22

Somatosensory Pathway of Pain, Temp and Coarse Touch

Back 22

Stimulus
Receptor
Synapse at spinal cord and cross
2ndary neuron to thalamus
Tertiary neuron to somatosensory cortex

Front 23

Somatosensory Pathway of Fine Touch, Vibration and Proprioception

Back 23

Stimulus

Receptor

Enters spinal cord and ascends

Synapse at medulla and cross

2ndary neuron to thalamus

Tertiary neuron to somatosensory cortex

Front 24

Homunculus

Back 24

Represents amount of neurons per area of body.

Sensory map of somatosensory cortex.

Front 25

Somatosensory Nerve Fibers

Back 25

AB (beta)

Ad (delta)

C

Front 26

AB (beta) Nerve Fiber

Back 26

Large, myelinated

- rapid conduction 30-70 m/s

Mechanical stimuli

Front 27

Ad (delta) Nerve Fiber

Back 27

Small, myelinated

- 12-30 m/s

Cold, fast pain, mechanical stimuli

Front 28

C Nerve Fiber

Back 28

Small, unmyelinated

- slow conduction: 0.5-2 m/s

Slow pain, heat, cold, mechanical stimuli

Front 29

Touch Receptors in the Skin

Back 29

Free Nerve Endings

Meissner's Corpuscles

Pacinian Corpuscles

Ruffini Corpuscles

Merkel Receptors

Front 30

Free Nerve Endings

Back 30

Location: around hair roots and under skin surface

Stimulus: temp, noxious stimulus, hair movement

Front 31

Meissner's Corpuscles

Back 31

Location: superficial lyrs of skin

Stimulus: flutter, stroking (soft pressure)

Front 32

Pacinian Corpuscles

Back 32

Location: deep lyrs of skin

Stimulus: vibration

Front 33

Ruffini Corpuscles

Back 33

Location: deep lyrs of skin

Stimulus: skin stretch

Front 34

Merkel Receptors

Back 34

Location: superficial lyrs of skin

Stimulus: steady pressure, textures

Front 35

Olfactory Tracing

Back 35

Stimulus (airborne chemicals)

External nares

Nasal cavity

Olfactory Receptors (primary neuron, AP)

Olfactory bulbs (soma of primary neuron)

Olfactory tract (2ndary neuron AP)

Olfactory cortex in temporal lobe (integration)

Front 36

Papillae of the Tongue

Back 36

Contain taste receptors (except filiform)

Circumvallate: most taste buds

Fungiform: 2nd most taste buds

Filiform: no taste receptors (texture)

Foliate

Front 37

5 Taste Sensations

Back 37

1) sweet

2) sour

3) salty

4) bitter

5) umami

Areas are not dedicated to certain sensations, areas may have more of 1 type of receptor

Front 38

Taste Tracing

Back 38

Chemical (stimulus)

Oral cavity (enzymes break down)

Papillae

Taste bud

Taste receptor

Glossopharyngeal and Facial Nerves

Thalamus

Gustatory Cortex of the Insula

Front 39

Functions of the Ear

Back 39

Hearing

Equilibrium

Front 40

Tracing for Hearing

Back 40

Soundwave (stimulus)

Ear Canal (external acoustic meatus)

Tympanic memb (stabilized by tensor tympani)

Malleus->Incus->Stapes (stabilized by stapedius muscle)

Oval Window

Vestibular Duct (perilymph: increase speed and stabilizes wave pattern)

Cochlear duct (endolymph: increase speed, stabilize)

Tectorial memb

Hair cells (receptors) transduction -----> exit

Cochlear branch of Vestibulocochlear nerve

Vestibulocochlear nerve

Auditory cortex of temporal lobe

Front 41

Sound wave exit from cochlea

Back 41

Waves enter->

Cochlear duct

Tectorial membrane

Hair cells (transduction) ----> cochlear branch

Tympanic Duct

Round window

Eustachian Tube

Front 42

Tracing for Equilibrium

Back 42

Oval window

Saccule

Utricle (vestibule: contain maculae w/ otoliths for sensing gravity) transduction

Ampullae (cristae w/ hair cells for rotational movement) transduction -----> Wave exit

Vestibular branch of vestibulocochlear nerve

Cortex of temporal lobe

Front 43

Wave exit for Equilibrium

Back 43

Ampullae

Semicirular Canals

Round window

Eustacian tube

Front 44

Cristae

Back 44

Found in ampulla of vestibular apparatus

Sense rotational movement.

Hair cells bend in opposite direction of movement due to momentum.

Front 45

Otoliths

Back 45

Found in macula of vestibular apparatus

Sense gravity

Hair cells bend in same direction of movement

Front 46

Layers of Vitreous Chamber

Back 46

Retina: nervous tiss

Choroid: vascular

Sclera: fibrous tiss

Front 47

Retina

Back 47

Nervous tunic

Multilayered nervous tissue in vitreous chamber

- ganglion, bipolar, rods and cones

- light passes thru layers, then signal passes in reverse

Front 48

Rods and Cones

Back 48

Receptor cells of the eye

Rods: dark environment

Cones: light environment, colors, sharpness

Front 49

Macula

Back 49

Contains only cones

Fovea: region of sharpest vision

- area of highest concentration of cones

Front 50

Optic Disk

Back 50

No photoreceptors

Blind spot

Front 51

Vision Tracing

Back 51

Light rays

Cornea

Pupil (controlled by sphincter/radial muscles)

Lens

Posterior cavity (vitreous chamber: stabilize light rays and maintain concentration)

Retina: ganglion->bipolar

rods & cones (transduction)

bipolar->ganglion

Optic nerve

Medial/Lateral pathways

Optic Chiasm (medial pathways X)

Occipital Cortex

Front 52

Intrinsic Muscles of the Eye

Back 52

1) Ciliary Muscle: lens shape

2) Radial Muscle: iris

3) Sphincter Muscle: iris

Front 53

Ciliary Muscles

Back 53

Controls lens shape to change focal point (accomodation)

Attached to lens via suspensory ligaments

Relaxed: ligs in tension, lens flat

Contracted: no tension, lens round

Front 54

Radial and Sphincter Muscles

Back 54

Controls pupil size

Radial contraction -> pupil dilation

Sphincter contraction -> pupil contraction

Front 55

Phototransduction

Back 55

Process by which light energy is converted into electrical signals.

Front 56

Phototransduction of Rod in Darkness

Back 56

Rhodopsin Inactive

cGMP high

CNG gate open (influx Ca2+ and Na+)

Depolarizes cell membrane

Tonic release of neurotransmitter on bipolar cells

Front 57

Phototransduction of Rod in Light

Back 57

Light bleaches rhodopsin

Rhodopsin activated

Cell membrane hyperpolarizes

Neurotransmitter release decreases in proportion to amount of light