Sensory systems

Question 1

What is a sensory system ?

Answer 1

A system that receives information from the environment through receptors at the periphery, and transmits this information to the CNS.

Question 2

you can modulate the sensation

Answer 2

true

Question 3

Sensory systems encode four basic attributes of a stimulus

Answer 3

1. Modality (the form of sensory sensation)
2. Intensity
3. Duration
4. Location

Question 4

what are the 5 major sensory modalities ?

Answer 4

1. Vision
2. Hearing
3. Touch
4. Taste
   5.Smell
   To these can be added:- 6. Balance
5. Proprioception

Question 5

what are sense organs

Answer 5

structures that mediate sensory modalities

Question 6

what are sensory receptors

Answer 6

specialised cells found within sensory organs

- transduce (covert) physical information about a stimulus into a neural signal

Question 7

What are the five major sensory receptors types in animals ?

Answer 7

1. Chemoreceptors (Taste/Smell/pCO2/p02)
2. Mechanoreceptors
   (Hearing/Balance/Touch/Proprioception )
3. Thermoreceptors (touch)
4. Photoreceptors (Vision)
5. Nociceptors (Touch > pain)

Question 8

are receptors sensory neurones ?

Answer 8

Receptors for sensory stimuli are not always the sensory neurons.

In the retina, rods and cones are neurons. Sensory neurons for touch, pressure, pain, and proprioceptors are neurons, one end of each of these sensory neurons is specialized to be excited by a specific stimulus. Sensory cells for smell are neurons.

Sensory receptors for taste, hearing and balance (vestibular) are not neurons, but they synapse with first order primary neurons. Once receptors are excited, the first order neurons are depolarized and fire action potentials.

Question 9

sensory systems..

Answer 9

encode a range of stimulus attributes
use a different sensory receptors
have receptors that are sensitive to specific forms of stems energy (light, sound etc)

Question 10

what is the role of a sensory receptor ?

Answer 10

To transduce (convert) stimulus energy into neural activity.

Question 11

stimulus energy takes many different forms.

Answer 11

for example
photons of light
vibrations of air molecules
direct mechanical force

Question 12

energy of stimulus causes a change in the ..

Answer 12

membrane potential of the sensory receptor aka a receptor potential

Question 13

properties of a receptor potential

Answer 13

1. it propagates electronically
2. it is restricted to the sensory receptor’s cell membrane
3. it is a graded potential

Question 14

what underlies the receptor potential

Answer 14

opening or closing of ion channels: transduction channels

Question 15

what does the intensity of a stimulus determine

Answer 15

the magnitude or amplitude of the receptor potential

Question 16

what does the amplitude of the receptor potential determine

Answer 16

the frequency of action potentials ( the number of action potentials per unit time)

Question 17

The intensity of a stimulus determines..

Answer 17

the rate of discharge of action potentials.. this is called rate of frequency coding

Question 18

what are muscle spindles

Answer 18

also called a stretch receptor. The spindles and their associated Ia axons, specialised for the detection of changes in muscle length (stretch), are examples of proprioceptors.

Question 19

Adaptation

Answer 19

• decline in the amplitude of the RP in receptor cell
• the frequency of action potentials decreases with time in response to a sustained stimulus
• very useful because of the wide range of intensities that sensory systems can signal e.g vision 10
• often a result of a desensitisation of ion channels underlying transduction
• can also be due to mechanical changes e.g. muscle spindle, hair cell
• chemical changes e.g. photoreceptors
• can also be due to transmission properties at synapse

Question 20

what are hair cells

Answer 20

sensory receptors of hearing and balance

Question 21

the mammalian vestibular system

Answer 21

is responsible for the sense of balance

• monitors rotational acceleration
• linear acceleration
• gravity

Question 22

describe tonic sensory inputs

Answer 22

Tonic sensory input adapts slowly to a stimulus[2] and continues to produce action potentials over the duration of the stimulus.[3] In this way it conveys information about the duration of the stimulus. In contrast, phasic receptors adapt rapidly to a stimulus. The response of the cell diminishes very quickly and then stops.[2] It does not provide information on the duration of the stimulus;[3] instead some of them convey information on rapid changes in stimulus intensity and rate.

Question 23

what do gamma efferents in the muscle spindle do

Answer 23

they reset the length of the intrafusal muscle fibres