Chapter 46

Question 0

Where do the sensors go for processing and interpretation?

Answer 0

Central Nervous System (CNS)

Question 1

What are sensors/receptors?

Answer 1

Sensory receptor cells that convert physical and chemical stimuli (light, sound waves, pressure (touch), odors, taste molecules) into neural signals

Question 2

What is sensory transduction?

Answer 2

The first step is a change in membrane potential of the receptor cell to a specific type of stimulus. Begins with a receptor protein that opens/closes ion channels in response to specific stimulus- the resulting change in ion flow alters the receptor cells membrane potential

Question 3

What is a receptor potential?

Answer 3

A change in membrane potential of a receptor cell in response to a stimulus. Are graded membrane potentials that spread only over short distances

Question 4

How can a receptor potential spread over long distances?

Answer 4

Must generate action potentials that are done in 2 ways. 1) receptor potential may trigger action potentials in the receptor cell itself 2) the receptor potential may cause the receptor cell to release neurotransmitters that can induce a postsynaptic neuron to generate action potentials

Question 5

What is an excitatory ligand gated channels?

Answer 5

Are permeable to cations (Na+, K+). Produce depolarization via Excitatory Postsynaptic Potentials- Is a postsynaptic potential that makes the neuron more likely to fire an action potential. The temporary depolarization of the postsynaptic membrane potential caused by the flow of positively charged ions into the postsynaptic cell via ligand gated channels. EX: receptors for acetylcholine, glutamate, serotonin

Question 6

What is an inhibitory ligand-gated ion channel?

Answer 6

Are permeable to anions (Cl-). Produce hyperpolarizations via inhibitory postsynaptic potentials- result from the flow of negative ions into the cellar positive ions out of the cell, is a kind of synaptic potential that makes a postsynaptic neuron less likely to generate an action potential. EX: receptors of glycine, GABA

Question 7

How does a Metabotropic receptor work?

Answer 7

Receptor is not an ion channel but activated G protein, which in turn activates an ion channel in many cases via a change in concentration of a second messenger such as cyclic nucleotide or Ca+2

Question 8

Which receptors are ionotropic sensory receptors?

Answer 8

1) mechanoreceptors, 2) electroreceptors, 3) temperature receptors, 4) some kinds of taste receptors (salt detectors). All cases- sensory stimulus gates a channel directly, stimulus directly affects ion channel concentration

Question 9

Which receptors are Metabotropic sensory receptors?

Answer 9

1) olfactory receptors, 2) some kinds of taste receptors (sweet, bitter) , 3) all photoreceptors. Sensory receptor molecule activates channels in directly via a G protein

Question 10

What stimulus causes a 1) mechanoreceptors, 2) thermoreceptor, 3) electroreceptors to open?

Answer 10

1)pressure opens an ion channel- pressure sensitive cation channel, 2) temperature influences a membrane protein that is a cation channel or is closely associated with the channel- temperature sensitive cation channel, 3) an electric charge opens an ion channel- voltage gated Ca2+ channel

Question 11

What stimulus cause a 1) chemoreceptor, 2) photoreceptor to open?

Answer 11

1) A molecule binds to a receptor, initiating a signal that controls the ion channel V a second messenger cascade 2) light alters a receptor protein initiating a signaling cascade to control an ion channel

Question 12

What are the types of mechanoreceptors in mammalian non-hairy skin? (Picture pg. 952)

Answer 12

1) Merkel’s disks: slowly adapting, responsible in large part for sense of touch
2) Messiner’s corpuscles: rapidly adapting, sense of flutter, shape of touched objects
3) Ruffini endings: slowly adapting pressure detectors in deep skin
4) Pacinian corpuscles: rapidly adapting pressure detectors in deep skin, respond to high frequency vibrations

Question 13

What are sterocilia? Hair cells?

Answer 13

fingerlike extensions of the cell membrane stiffened by cross-linked actin filament- project from the surface of each hair cell like a set of organ pipes. Bend in response to waves of pressure, bending of the sterocilia in one direction depolarizes the hair cell and bending in the other direction hyperpolarizes it
-are the mechanorecpetors for the vertebrate auditory system (sound-?perceiving) and the vestibular (equilibrium- maintaining) systems

Question 14

How do sterocilia release neurotransmitter onto a sensory neuron?

Answer 14

• when a cilium is bent in one direction, the small filaments open a mechanosensory ion channel at the tip of the neighboring cilium. the depolarized hair cell releases neurotransmitter onto a sensory neuron.
  1) sterocilia project into a fluid high in K+ and low in Na+, when K+ channels open- K+ enters and depolarize is the cell. 2) Ion channels open when sterocilia are bent in one direction 3) and close when they are bent in opposite 4) membrane depolarization opens voltage gated Ca2+ channels causing neurotransmitter release

Question 15

How do you hair cells play a role in the auditory system of soundwaves and the human ear?

Answer 15

Hair cells of the semicircular canals are stimulated by rotational acceleration caused by the movement of the head.

Question 16

What is the importance of the Otoliths organs located in the ear?

Answer 16

Otoliths organs located adjacent to semicircular canals, called utricle and saccule. Cells of utricle and saccule detect linear acceleration in the position of the head with respect to gravity

Question 17

What causes Benign Paroxysmal Positional Vertigo (BPPV)?

Answer 17

BPPV usually develops when calcium particles (otoliths) that are normally embedded in one part of the inner ear (utricle and saccule) are displaced and moved into another part of the inner ear ( most commonly the posterior semicircular canal), causes vertigo or dizziness

Question 18

What is the Epley Maneuver?

Answer 18

Is the repositioning used to treat BPPV, works by allowing free-floating particles from the affected semicircular canal to be relocated using gravity back into that utricle,

Question 19

How are pitch differences detected in the cochlea and basilar membrane?

Answer 19

Sounds produce a traveling wave down the Basilar membrane whose amplitude for different sound frequencies is the greatest at different places along the length of the cochlea
Low pitch: pressure waves travel far down the vestibular canal and flex the basilar membrane activating action potential in low frequency sensors
Medium pitch:pressure waves travel only part way down the upper canal before flexing the basilar membrane and activating mid- frequency sensors
High pitch: pressure waves travel a short distance before flexing the basilar membrane and activating high-frequency sensors

Question 20

What are olfactory receptors?

Answer 20

Responsible for the detection of odor molecules, activated olfactory receptors are the initial player in a signal transduction cascade which produces a nerve impulse that is transmitted to the brain

Question 21

What is the process of the transduction cascade?

Answer 21

1) receptor 2) G protein 3) Effector molecule (adenyly cyclase) 4) second messenger (cAMP) 5) Channel (second messenger gated)

Question 22

Olfactory Receptor Molecules

Answer 22

1000 different molecule genes that are functional in the mouse genome and 300-350 in man
Each cell expresses only a single type of receptor molecule Gene
Each receptor molecules sensitive to a wide variety of odors but specificity is different for each receptor molecule
Many receptor cells in the epithelium express the same receptor molecule and all these synapse together onto the same group of cells in the CNS

Question 23

What is rhodopsin?

Answer 23

Photosensitivity depends on the ability visual pigments to absorb photons of light and to undergo a change in conformation.
Vertebrate visual pigment
Consists of opsin protein and 11-cis- retinal (nonprotein light absorbing functional group)

Question 24

What is photoisomerization?

Answer 24

The light absorbing molecule 11-cis-retinal bonds with the protein opsin to form the vertebrate visual pigment rhodopsin.
1) 11-cis-retinal is sensitive to light 2) and when it absorbs a photon it becomes all-trans-retinal. After passing through unstable intermediates all-trans-retinal activates a G protein cascade that results in a change in membrane potential 3) when all-trans-retinal returns to 11-cis confirmation it is a photo responsive again

Question 25

How does light absorption affect the sodium channels?

Answer 25

1) in the absence of light Na+ channels are open and create a depolarizing dark current
2) rhodopsin Absorbs light energy
3) causing a G protein, transducin, to exchange GTP for GDP
4) activated PDE hydrolyzes cGMP causing Na+ channels to close. The cell hyperpolarizes

Question 26

Why are cGMP gated channels open in the dark? What does the closing of the channel cause?

Answer 26

Because cGMP is high in the dark. The closing of the channels causes the membrane potential of the photoreceptor to hyperpolarized and decrease release of transmitter