L7 - Sensory Systems & Vision Flashcards
List the special senses.
vision, hearing, taste, smell, equilibrium
List the somatic senses.
touch, temperature, pain, itch, proprioception (awareness of where you are in space)
List visceral stimuli.
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
List somatic stimuli.
muscle length and tension
proprioception
What are the three main classes of sensory receptors ranging from simple to complex?
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
What types of receptors/sensors are required for the fives ‘senses’?
‘smell’ uses neurons and all other senses use specialised cells (e.g. photoreceptors, hair cells) that detect physical energy and synapse on sensory neurons
What are the four main types of sensory receptors? List examples of stimuli which trigger each of these types of receptors.
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
What is a receptive field?
an area of skin, for example, that a sensory neuron innervates
What happens when the receptive fields of three sensory neurons overlap?
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
What is the name of three primary receptive fields which overlap?
a secondary receptive field
Where do most sensory pathways project to? What is the role of this part of the brain?
the thalamus which modifies and relays information to cortical centers
Where do olfactory pathways from the nose project to?
through the olfactory bulb to the olfactory cortex
Where do equilibrium pathways project to?
to the cerebellum
The minimum stimulus required to activate a sensory receptor is its…
threshold
How do neurons indicate a stronger signal?
sending action potentials at a higher frequency
this is known as frequency coding
What is frequency coding?
indicating a stronger signal by sending action potentials at a higher frequency
What is population coding?
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
Convergence creates receptive fields that have ______ resolution.
lower
Why is resolution of peripheral vision much lower than the resolution of vision near the fovea?
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
What do photoreceptors do to light so that our brain can process this type of signal?
they transduce light into electrical signals
How many more rods are there than cones? What type of vision are rods good for?
more numerous than cones (20:1)
good for night vision
What type of vision are cones good for and how many types are there?
colour vision and high acuity vision (predominant receptor at fovea) three types (different colours - with different opsins - visual pigments)
What are the three primary colours sensed by photo pigments?
red, blue and green
A person with defective cones will have trouble with…
distinguishing colors
What is the role of the pigmented epithelium and where is it found?
it is found on the retina and its role is to absorb light (cones and rods are embedded in this layer)
Where are rhodopsins found?
they are found in discs within rods
How often are rods releasing neurotransmitter?
all the time (tonically) unless they are stimulated by light
