Sensory Receptors and Exteroception

Question 1

Weak left hand, clumsy left leg. Abnormal temperature and pinprick sensation in right leg. Loss of vibration sense in left hand. Left plantar response extensor (Babinski)

Answer 1

Hemisection of the left spinal cord (Brown-Séquard)

Question 2

Hand grips weak bilaterally. Bilateral decreased touch and vibration below his knees. Normal pinprick, except in the palm of his hands. No truncal sensory level.

Answer 2

Acute inflammatory demyelinating polyneuropathy (Guillain-Barré)

Question 3

Special Sensory Systems

Answer 3

Light- seeing
Air Pressure- hearing
Chemical- olfaction; taste

Question 4

sensory receptor cells depolarization of the membrane in the synaptic region causes opening of ______________ eliciting an increase in intracellular calcium, which triggers synaptic vesicle fusion and release of chemical transmitter(s) to which the second order cell is sensitive.

Answer 4

voltage-dependent calcium channels

Question 5

Exteroception Somatosensory system

Answer 5

vibration- touch

Pain/Temp-

Question 6

Depolarizing receptor potentials. Receptors that depolarize to their adequate stimulus
generally do so as a result of an increase in:

Answer 6

nonspecific cation conductance in the receptive area membrane.

Question 7

Sensory receptor cell characteristics

Answer 7

have somas/ nucleus, synapse, second order neuron, sensory ending

Question 8

The process of detection of a sensory input and transformation of information into a change in neuronal action potential – a neural signal - is called :

Answer 8

transduction.

Stimulus–> voltage change

transduction channels are not voltage-dependent

Question 9

Sensory endings are _____ dependant

Answer 9

Stimulant

Not voltage

Question 10

An example of a receptor that hyperpolarizes upon stimulation is the

Answer 10

rod photoreceptor

resting membrane potential of
approximately –40 mV due to a substantial resting cation conductance

Question 11

Voltage dependant channels with 2 gates:

Answer 11

Na channel

Question 12

Some receptors, such as hair cells of the auditory system, respond to stimulation with an oscillatory change in generator potential alternating between:

Answer 12

depolarization and

hyperpolarization

Question 13

Retina has 2 cell types

Answer 13

Cone cells, color

rod cells, light

Question 14

Receptors that hyperpolarize in response to stimulation have resting potentials that lie between 0 mV and Ek (-70 mV), generally:_____

Answer 14

-30 to -40 mV

Question 15

Proprioception

Answer 15

you do not need to think a lot to move. Brain knows where hand is by: Detecting stretch of muscles (muscle spindles)

Question 16

Muscle Spindle

Answer 16

Direct channel that opens when stretched

Allows proprioception

Question 17

Photoreceptors (rods) are NOT _____ and they DO NOT have:

Answer 17

NOT channels

NO action Potentials

Question 18

Photoreceptors (rods) ARE _____

Answer 18

second messenger systems

Question 19

Second Messenger system of Rods

Answer 19

Light–> rhodopsin (trans)–> activate G Protein–> activate cGMP phosphodiesterase (PDE)–> PDE hydrolyzes cGMP (↓ cGMP)–> Closes Na Channel

Question 20

_______ opens the Na/ K channel of rods

Answer 20

cGMP

cGMP gated

Question 21

Light ________ the cell, the more light, the greater the intensity

Answer 21

HYPERPOLARIZES

Question 22

Retina is in ___ conformation in the dark

Answer 22

cis- (kinked/angles)

Question 23

Retina is in ___ conformation in the presence of light

Answer 23

Trans- able to detect g protein

Question 24

_______ or perceived amount of a sensation depends on the stimulus strength.

Answer 24

Intensity

Long sensory receptor cells code stimulus intensity as an increase in action potential firing frequency.

Question 25

transduction channels are not:

Answer 25

voltage-dependent
Key: Second messenger system that opens or closes channel
*Can amplify

Question 26

Second messenger system types and key point

Answer 26

• Vision
• capsaicin

MASSIVE amplification

Question 27

_____ sense has no second messenger

Answer 27

Touch (somatosensory)
Proprioception
*Directly gated channel

Question 28

A-Beta

Aβ

Answer 28

Mechanoreceptors of skin, secondary muscle spindle afferents

Question 29

_______ has direct channel but no action potential

Answer 29

Auditory

Question 30

The concept of labeled lines:

Answer 30

Conscious appreciation of sensory modality is determined by specific neuronal connections from sensory organs through thalamus to cerebral cortex.

Question 31

There is a separate chain of neurons ________ for each sensory system

Answer 31

(a separate labeled line)

Question 32

Anatomically, there are separate pathways for the different sensory systems, illustrating the fact that the central nervous system preserves the distinctions inherent in its ___________

Answer 32

receptor inputs

Question 33

The question of how the brain knows when light is hitting retina VS air vibrations at eardrum is answered by stating that different nerve cells are active for the two kinds of stimulation. Thus, ________ (e.g., hearing, vision, taste, touch, pain, pressure on skin, heat, cold, smell, etc.) is coded by which nerve cells are active.

Answer 33

stimulus modality