BMS 108 Ch. 10 Sensory Physiology

Question 0

How are the different receptors grouped?

Answer 0

according to the type of stimulus they transduce

Question 1

What are the six types of sensory receptors and what do they react to?

Answer 1

1. Chemoreceptors - respond to chemicals (taste, smell)
2. Photoreceptors - respond to light (vision)
3. Thermoreceptors - temperature
4. Mechanoreceptors - hair cells, mechanically pull open ion channels (skin, balance, hearing)
5. Nocireceptors - pain
6. Proprioceptors - limbs in space (spindle apparatus, stretch receptors)

Question 2

What is a generator potential?

Answer 2

A subthreshold response to an adequate stimulus. (like EPSPs)

Question 3

Generator potential are _______ in amplitude.

Answer 3

graded

Question 4

Generator potentials are _________ to stimulus intensity.

Answer 4

proportional

Question 5

If a generator potential reaches threshold, then an ______ _______ is generated.

Answer 5

action potential

Question 6

What is a tonic responder?

Answer 6

A receptor that fires APs throughout the entire duration of a stimulus.

Question 7

What is a phasic responder?

Answer 7

Habituates. Only fires APs when a stimulus changes.

Question 8

What is tactile acquity?

Answer 8

A measure of distance between receptive fields. The larger the receptive field, the less tactile acquity.

Question 9

What is lateral inhibition?

Answer 9

The ability of an excited neuron to inhibit activity in its neighbors.

Question 10

How many neurons are in the neural pathway for somatesthetic senses?

Answer 10

Three;

First order - sensory receptor to spinal cord
Second order - decussates at SC or medulla; to thalamus
Third order - Thalamus to cortex

Question 11

What is the purpose of lateral inhibition?

Answer 11

To sharpen sensations

Question 12

What are the five tastes?

Answer 12

Sweet, Sour, Salty, Bitter and Umami

Question 13

What are taste buds?

Answer 13

Modified epithelial cells with microvilli.

Question 14

How many modified epithelial cells are in each taste bud?

Answer 14

50-100

Question 15

How many tastes can each bud respond to?

Answer 15

all of them

Question 16

If each taste bud can respond to all tastes, why don’t we taste everything all at once?

Answer 16

Because the sensory nerve fiber attached to a taste bud can only carry one type of signal.

Question 17

Which tastes can pass directly through the taste bud receptor cell?

Answer 17

Salty and sour

Question 18

Which tastes use 2nd messenger systems?

Answer 18

Sweet and bitter

Question 19

How does olfaction work?

Answer 19

Odor molecules bind to receptors (~ 350 kinds) and act through G-proteins (which greatly amplifies the signal).

Question 20

How many neurons in olfaction?

Answer 20

Two;

1st order - to glomeruli of olfactory bulb
2nd order - olfactory bulb to cortex (doesn’t route through thalamus)

Question 21

What kind of receptors does the inner ear use?

Answer 21

mechanoreceptors

Question 22

What is the vestibular system responsible for?; the auditory system?

Answer 22

equilibrium/balance; hearing

Question 23

How do we hear?

Answer 23

By transducing sound waves

Question 24

How are sound waves measured?

Answer 24

Frequency is measured in hertz (cycles/sec) and is directly related to pitch
Intensity (loudness) is measured in decibels and related to the amplitude of waves

Question 25

Where are the hair cells used for hearing located?

Answer 25

In the cochlea.

Question 26

High frequencies maximally stimulate the spiral organ closer to the ______ of the cochlea and lower frequencies stimulate closer to the ______.

Answer 26

base; apex

Question 27

What is another name for the spiral organ?

Answer 27

Organ of Corti

Question 28

What are the forces that activate the hair cells?

Answer 28

shearing forces

Question 29

Do hair cells have generator potentials?

Answer 29

yes

Question 30

What cranial nerve does hearing affect?

Answer 30

Vestibulocochlear Nerve (CN 8)

Question 31

Trace the neural pathway for hearing.

Answer 31

CN 8 > medulla > inferior colliculus > thalamus > auditory cortex of the temporal lobe

Question 32

What are the wavelengths of the electomagnetic spectrum that we see as visible light?

Answer 32

400 - 700 nm

Question 33

What is the retina?

Answer 33

Neural layer of the eye that houses photoreceptors (rods & cones), bipolar and ganglion cells.

Question 34

What photoreceptors respond to low light conditions? color and acquity?

Answer 34

rods; cones

Question 35

Rods and cones consist of _____ and ______ segments.

Answer 35

inner; outer

Question 36

Outer segments contain stacks of __________ ______.

Answer 36

photopigment discs

Question 37

Trace the pathway from photoreceptor to optic nerve.

Answer 37

rods & cones > bipolar cells > ganglion cells > optic nerve

Question 38

Describe how light affects rods.

Answer 38

1. Rods are activated when light produces a chemical change in rhodopsin, causing it to dissociate into retinal and opsin
2. Causes Na+ channels to close
3. Rod hyperpolarizes which decreases the amount of inhibiting NT released from the rod to the bipolar cell
4. Bipolar cell released from inhibition and releases excitatory NT to the ganglion cells
5. Increasing the chance of a ganglion cell having an AP

Question 39

Rods and cones contain many ____ channels, that are _____ in the dark. This depolarizing ____ influx is the _____ _______.

Answer 39

Na+; open; dark current

Question 40

Rods, cones and bipolar cells produce _________ __________.

Ganglion cells produce ______ __________.

Answer 40

generator potentials; action potentials

Question 41

Cones are _____ sensitive than rods to light.

Answer 41

less

Question 42

Instead of rhodopsin, cones have 3 _________. One each for red, green and blue absorption.

Answer 42

Photopsins

Question 43

Visual acuity is due to the structure of the ______ ______.

Answer 43

fovea centralis

Question 44

Describe the fovea centralis.

Answer 44

1. contains only cones
2. neural layers displaced to sides so that light strikes the cones directly
3. each cone supplies 1 ganglion cell

Question 45

Light sensitivity is due to __________.

Answer 45

convergence

Question 46

Why does covergence increase light sensitivity?

Answer 46

Less light is required to get the rod ganglion cell to threshold.