Chapter 7 - Focus area Flashcards
Sensory receptors are either?
specialized endings of the afferent neurons or separate cells that signal afferent neurons
What does adaptation look like? Think of the graph. Define adaptation. What does rapidly adapting look like? What does slowly adapting looking?
A decrease in the stimulation response due to continued presence of stimulus (and a reduction in action potentials as a result). This mechanism prevents sensory overload
You can get a better idea of exactly where a stimulus is located if what?
The area where the stimulus occurs has a small receptive field, and area has many sensory neurons. You want to have a more spatially limited receptive field (smaller field)
Types of Sensory Receptors -List them and define what they do
Chemoreceptors - respond to different chemicals - oxygen, and other organic molecules like glucose, pH. Provide sense of smell and taste. Mechanoreceptors - respond to physical pressure (baroreceptors), stretching of the cell (osmoreceptors), vibration, sound, acceleration. Responsible for sensory info like BP, touch, muscle tension Photoreceptors - respond to different wavelengths of light. Respond to photons Thermoreceptors - varying degrees of heat. Detect sensations of cold or warmth.
What is somatic sensation?
sensation from skin, skeletal muscles, bones, tendons, and joints. Some of these receptors are mechanical, and respond to stimulation of hair, skin, and underlying tissues, while others respond to temperature or chemical changes.
Different types of somatic receptors? List them on this image.
-Tactile (Messiner’s) corpuscle (light touch) -Tactile (Merkle’s) corpuscles (touch) -Free Nerve Ending (pain) -Lamellated (Pacinian) Corpuscle (vibrations, and deep pressure) -Ruffini corpuscle (warmth)
The contraction state of which muscle determines the shape of the lens? Contracted what happens, relaxed what happens?
Ciliary muscle determines this, and it is attached zonular fibers that connect directly to the lens.
Contracted state stretches = less tension on zonule fibers, and the lens is more round, so you can see closer up.
Relaxed state puts more pressure on zonule fibers, and the lens becomes flat, so you can see farther away.
What does it mean when eye is out of focus? What can fix this? And why does it sometimes happen?
Lens does not project light properly onto fovea. Example would be when ciliary muscle is relaxed, lens is flattened, but trying to see something close up. Not going to be in focus. Corrective lenses can fix this. Sometimes happens bc eye changes shape over time, muslces become weak, and fibers weaken.
Different types of eye conditions. There are four of them.
Cataracts - cloudy lens. Caused by UV exposure, smoking, diabetes
Astigmatism - lens or cornea does not have a smoothy spherical surface. This results in distorted images, as light rays are prevented from meeting at a common focus.
Glaucoma - major cause of irreversible blindness. It is a disease in which retinal cells are damaged by increased pressure (from aqueous humor pressure)
Colorblindness - genetic disorder, and sex-linked, but recessive. Most common is red-green colorblindness
What are the two types of photoreceptor cells? What does each do? Rods and cones contain ______, and what do these do? What are these cells made up of?
Rods and cones.
Rods are very sensitive and respond to very low levels of illumination (night vision), and are responsible for resolving images.
Cones are less sensitve, and respond only when the light is bright. Cones are in charge of color.
Rods and cones contain photopigments, and these cells are responsible for absorbing light. Photopigments are made up of opsin protein attached to retinal (chromophore). The chromophore is the portion of the photopigment that is light sensitve, and responds to different wavelengths of light.
What do amacrine and bipolar cells do?
They absorb excess light, and get rid of fuzzy, blurry, double vision. They aid with lateral inhibition. This prevents blurry vision – it’s helping to prevent a lot of feedback or reflection from the light coming in.
What does the epithelial layer of the retina aid with?
Epithelial layer - The other thing that helps us see better – absorb light rather than reflect it. This prevents reflection and scattering of photons back through the rods and cones, which would cause a blurred image. Reflective in animals that are active at night.
Describe the cell membrane potential changes in a cone cell.
In light
- molecules of retinal in the disc membrane assume a new conformation induced by the absorption of energy from photons and dissociate from the opsin
- Opsin then interacts with transducin (G-protein family)
- Transducin activates cGMP-phosphodiesterase, which quickly degrades cGMP.
- Causes cation channel to close, MP hyperpolerizes
Describe field of vision.
In each eye, I have a field of vision. Left eye: left and right field of vision. Right eye: Right field of vision actually is received by the left side of the retina and continues to travel and is perceived in the left cortex of the brain. Left eye: right field of vision no matter which eye, is perceived by the left visual cortex.
List the parts of the ear. Where is the organ or Corti, and what does it contain?
Sits on the basilar membrane, and contains the ear’s sensitive receptor cells.
