Ch. 10 Sensory Physiology

Question 1

Sensory Receptors

Answer 1

Transduce (convert energy into a different form) different forms of energy in the “real world” to nerve impulses.

Different modalities of sensations (sound, light, pressure) arise from differences in neural pathways and synaptic connections
–ex: If the optic nerve delivers an impulse, the brain interprets it as light even though the impulse is the same as for hearing

Question 2

Functional Sensory Receptors: Chemoreceptors

Answer 2

Sense chemicals in the environment (taste, smell) or blood

Question 3

Functional Sensory Receptors: Photoreceptors

Answer 3

Sense light

Question 4

Functional Sensory Receptors: Thermoreceptors

Answer 4

Respond to cold or heat

Question 5

Functional Sensory Receptors: Mechanoreceptors

Answer 5

Stimulated by mechanical deformation of the receptor (touch, hearing)

Question 6

Information Sensory Receptors: Proprioceptors

Answer 6

Found in muscles, tendons, and joints. Provide a sense of body position and allows fine muscle control

Question 7

Information Sensory Receptors: Cutaneous (skin)

Answer 7

Touch, pressure, heat, cold, and pain

Question 8

Information Sensory Receptors: Special Senses

Answer 8

Vision, hearing, taste, smell, equilibrium

Question 9

What are the 2 origins of sensory receptors?

Answer 9

Exteroceptors and Interoceptors

Question 10

Exteroceptors

Answer 10

Respond to stimuli from outside the body; includes cutaneous receptors and special senses

Vision, hearing, taste, smell

Question 11

Interoceptors

Answer 11

Respond to internal stimuli; found in organs; monitor BP, pH, and oxygen concentrations

Cardiovascular system: sense BP

Question 12

Phasic

Answer 12

Respond w/ a burst of activity when stimulus is first applied but quickly adapt to the stimulus by decreasing response
–sense something and fire response/signal

Allow sensory adaptation - cease to pay attention to constant stimuli
–ex: live near airport hearing constant noise –> adaptation and it becomes background activity

Ex: smell, touch, temperature

Question 13

Tonic

Answer 13

Maintain a high firing rate as long as the stimulus is applied

Ex: pain

Question 14

Phasic Receptor

Answer 14

Fast-adapting

Fire less frequently –> consistency of signal

Question 15

Tonic Receptor

Answer 15

Slow-adapting

Question 16

What is the only special sense that bypasses the Thalamus?

Answer 16

Olfaction (smell)

Question 17

Describe Olfaction’s Sensory Pathway

Answer 17

Olfaction goes from nose to Olfactory cortex, not relayed through Thalamus

Directly process smell, all other senses relayed through Thalamus to be processed and sent to where it needs to go

Question 18

What are the 2 types of Chemoreceptors?

Answer 18

Taste (gustation)

Smell (olfaction)

Question 19

Taste (gustation)

Answer 19

Responds to chemicals dissolved in food and drink

Question 20

Smell (olfaction)

Answer 20

Responds to chemical molecules from the air; olfaction influences gustation

Question 21

Gustation

Answer 21

Receptors are called taste buds - consist of 50 to 100 specialized epithelial cells w/ long microvilli that extend out through the pore in the taste bud

• -each taste bud has taste cell sensitive to each category of 5 tastes: salty, sour, sweet, umami (meaty), bitter
• -microvilli come into contact w/ chemicals
• -cells behave like neurons by depolarizing and producing action potentials
• -cells release neurotransmitters onto sensory neurons

Question 22

Olfactory Receptors

Answer 22

Bipolar neurons w/ ciliated dendrites projecting into nasal cavity

Proteins in the cilia bind to odors

~380 genes code for ~380 different olfactory receptors

One odorant molecule stimulates one protein

Question 23

Vestibular Apparatus

Answer 23

Provides sense of equilibrium

Located in inner ear

Consists of:

• Otolith organs
• ->Utricle and Saccule - linear acceleration (ex: running toward door)
• Semicircular canals - rotational acceleration (ex: rotating body)

Question 24

Inner Ear

Answer 24

Consists of a body labyrinth surrounding a membranous labyrinth

Between the 2 is fluid called Perilymph

W/in the membranous labyrinth is fluid calls Endolymph, which has an unusually high K+ concentration, which will produce depolarization

Question 25

Why is the Perilymph important?

Answer 25

The multiple layers of membrane and fluid allow us to detect subtle movements This wouldn't be possible if the membrane was against bone w/o fluid

Question 26

Sensory Hair Cells

Answer 26

Modified epithelial cells w/ 20-50 hairlike extensions called Stereocilia (not true cilia) and one Kinocilium (true cilium) When the stereocilia bend toward the kinocilium, K+ channels and K+ rushes into the cell and depolarizes the cell --K+ concentration high on outside of cell, so when channels open it rushes in and depolarizes cell Cells release a neurotransmitter that depolarizes sensory dendrites in vestibulocochlear nerve

Question 27

Which has more structural support: stereocilia or microvilli?

Answer 27

Stereocilia

Question 28

What causes the stereocilia to move?

Answer 28

Fluid moving causes stereocilia to bend (won't bend w/o fluid movement)

Question 29

What is the tympanic membrane?

Answer 29

The eardrum

Question 30

Which part of the ear (outer, middle, or inner) is the fluid filled cavity?

Answer 30

The inner ear

Question 31

Middle Ear

Answer 31

Air-filled cavity between Tympanic Membrane and Cochlea Contains 3 bones called Ossicles: -Malleus, Incus, Stapes Vibrations are transmitted and amplified along the bones The stapes is attached to the Oval Window, which transfers the vibrations into the cochlea

Question 32

What is the purpose of the 3 ossicles (malleus, incus, stapes)?

Answer 32

Transmit sound waves that passed through tympanic membrane to the cochlea via the oval window

Question 33

Cochlea

Answer 33

Hearing part of inner ear 3 chambers: - -upper chamber is portion of bony labyrinth called Scala Vestibule (Perilymph) - -lower bony chamber called Scala Tympani (Perilymph) - -cochlea also contains a membranous labyrinth called Cochlear Duct (Scala Media) filled w/ Endolymph

Question 34

What's special about Endolymph?

Answer 34

There's a high K+ concentration outside of the cell; contains stereocilia

Question 35

How does the ear prevent echoing?

Answer 35

Sound waves are dissipated back into the middle ear from the inner ear at the Round Window

Question 36

Is the Cochlea fluid filled?

Answer 36

Yes (part of inner ear)

Question 37

Hearing: Mechanism

Answer 37

When sound waves enter the scala media, the tectorial membrane vibrates, bending stereocilia in the hair cells of the Organ of Corti. - -opens K+ channels that are facing endolymph - -K+ rushes in, depolarizing cell (b/c it's high concentration on outside) - -releases glutamate onto sensory neurons - -K+ returns to perilymph at base of stereocilia

Question 38

Hearing: Neural Pathways

Answer 38

Sensory neurons in inner ear --> integrated in Thalamus --> auditory cortex

Question 39

Vision

Answer 39

Comes from light energy transduced into nerve impulses Only a limited part of the electromagnetic spectrum can excite photoreceptors

Question 40

Where is the blind spot in the eye?

Answer 40

At the optic disc

Question 41

Is the eye highly vascularized?

Answer 41

Yes

Question 42

Path of Light (I'm sorry, but you need to know this)

Answer 42

1. Light passes through cornea and into anterior chamber of eye 2. Passes through pupil, which can change shape (due to pigmented iris muscle) to allow more/less light in 3. Passes through lens, which can change shape to focus image 4. Passes through posterior chamber and the vitreous body 5. Finally, it hits the retina, where photoreceptors are found and then absorbed by the pigmented choroid layer

Question 43

Pupil and Iris

Answer 43

Iris can increase or decrease the diameter of the pupil - Constriction: contraction of circular muscles via parasympathetic stimulation - Dilation: contraction of radial muscles via sympathetic stimulation Iris also has pigmented epithelium for eye color

Question 44

Lens

Answer 44

Composed of layers of living cells that are normally completely clear (must be transparent to do its job) Avascular Cell metabolism is anaerobic (lens is a group of cells!) Attached to muscles called Ciliary Bodies Suspended from Suspensory Ligaments

Question 45

Visual Fields

Answer 45

Part of the external world projected onto the retina Right side is projected onto the left side of retina Left side is projected onto right side of retina (see ch. 10 p. 36 notes for a good picture of how this works)

Question 46

Lens Accommodation

Answer 46

Accommodation is the ability of the lens to keep an object focused on the retina as the distance between the eye and the object moves Contraction of the ciliary muscle causes the lens to thicken and roundup (close vision) Relaxation of the ciliary muscle causes the lens to thin and flatten (distant vision)

Question 47

Retina

Answer 47

Extension of the brain, so the neural layers face outward toward incoming light (have to face outward in order to receive light) Neuron axons in retina are gathered at a point called the Optic Disc (blind spot) and exit as the Optic Nerve; blood vessels also enter/leave here Photoreceptors (rods and cones) are in the inner layer (toward vitreous body) These synapse on a middle layer of bipolar cells, which synapse on the outer layer of ganglion cells There are also horizontal cells and amacrine cells w/in the layers

Question 48

Rods and Cones: Outer and Inner Segments

Answer 48

Outer segment: full of flattened discs with photopigment molecules Inner segment: contains the cell organelles

Question 49

Rods

Answer 49

Black and white vision in low light; contain rhodopsin

Question 50

Cones

Answer 50

Color vision and acuity, contain photopsin which vary depending upon cone

Question 51

Vision: Mechanism

Answer 51

Stimulation of photoreceptor cells is outlier Stimulation results in hyperpolarization (instead of depolarization) Bipolar cells activate ganglion cells that transmit action potentials to brain