L7 - Sensory Systems & Vision

Question 1

List the special senses.

Answer 1

vision, hearing, taste, smell, equilibrium

Question 2

List the somatic senses.

Answer 2

touch, temperature, pain, itch, proprioception (awareness of where you are in space)

Question 3

List visceral stimuli.

Answer 3

blood pressure
distension of GI tract
blood glucose concentration
internal body temperature
osmolarity of body fluids
lung inflation
pH of cerebrospinal fluid
pH and oxygen content of blood

Question 4

List somatic stimuli.

Answer 4

muscle length and tension

proprioception

Question 5

What are the three main classes of sensory receptors ranging from simple to complex?

Answer 5

simple receptors which are neurons with free nerve endings, complex neural receptors which have nerve endings enclosed in connective tissue capsules and special senses receptors of which most are cells that release NT onto sensory neurons, initiating an action potential

Question 6

What types of receptors/sensors are required for the fives ‘senses’?

Answer 6

‘smell’ uses neurons and all other senses use specialised cells (e.g. photoreceptors, hair cells) that detect physical energy and synapse on sensory neurons

Question 7

What are the four main types of sensory receptors? List examples of stimuli which trigger each of these types of receptors.

Answer 7

chemoreceptors: oxygen, pH, various organic molecules such as glucose
mechanoreceptors: pressure (baroreceptors), cell stretch (osmoreceptors), vibration, acceleration, sound
photoreceptors: photons of light
thermoreceptors: varying degrees of heat

Question 8

What is a receptive field?

Answer 8

an area of skin, for example, that a sensory neuron innervates

Question 9

What happens when the receptive fields of three sensory neurons overlap?

Answer 9

the signal will be sent to the same interneuron regardless of where exactly the stimulus is coming from, therefore it can be difficult for the brain to determine exactly where the stimulus is coming from as the interneuron is only giving information about the general area the stimulus is coming from

Question 10

What is the name of three primary receptive fields which overlap?

Answer 10

a secondary receptive field

Question 11

Where do most sensory pathways project to? What is the role of this part of the brain?

Answer 11

the thalamus which modifies and relays information to cortical centers

Question 12

Where do olfactory pathways from the nose project to?

Answer 12

through the olfactory bulb to the olfactory cortex

Question 13

Where do equilibrium pathways project to?

Answer 13

to the cerebellum

Question 14

The minimum stimulus required to activate a sensory receptor is its…

Answer 14

threshold

Question 15

How do neurons indicate a stronger signal?

Answer 15

sending action potentials at a higher frequency

this is known as frequency coding

Question 16

What is frequency coding?

Answer 16

indicating a stronger signal by sending action potentials at a higher frequency

Question 17

What is population coding?

Answer 17

indicating a strong signal by having multiple neurons of different excitability
if only easily excitable neurons are firing then there is usually not much of a stimulus
if easily and moderately excitable neurons are firing then there is more of a stimulus
if easily/moderately excitable neurons and neurons which are difficult to excite are all firing then there is even more of a stimulus

Question 18

Convergence creates receptive fields that have ______ resolution.

Answer 18

lower

Question 19

Why is resolution of peripheral vision much lower than the resolution of vision near the fovea?

Answer 19

because there is usually a convergence ratio of ~15 to 45 : 1 from rods to ganglion cells, while near the fovea this is a 1 : 1 ratio resulting in high resolution

Question 20

What do photoreceptors do to light so that our brain can process this type of signal?

Answer 20

they transduce light into electrical signals

Question 21

How many more rods are there than cones? What type of vision are rods good for?

Answer 21

more numerous than cones (20:1)

good for night vision

Question 22

What type of vision are cones good for and how many types are there?

Answer 22

colour vision and high acuity vision (predominant receptor at fovea)
three types (different colours - with different opsins - visual pigments)

Question 23

What are the three primary colours sensed by photo pigments?

Answer 23

red, blue and green

Question 24

A person with defective cones will have trouble with…

Answer 24

distinguishing colors

Question 25

What is the role of the pigmented epithelium and where is it found?

Answer 25

it is found on the retina and its role is to absorb light (cones and rods are embedded in this layer)

Question 26

Where are rhodopsins found?

Answer 26

they are found in discs within rods

Question 27

How often are rods releasing neurotransmitter?

Answer 27

all the time (tonically) unless they are stimulated by light