Ch. 7 Sensory Pt. 2 (touch+vision)

Meissner’s corpuscle

detects light touch

Merkel disc

detects sustained touch/pressure

Pacinian corpuscle

rapidly adapting receptor that detects vibration & deep pressure

Ruffini ending

slow-adapting receptor

What are the 2 ascending tract systems of the Somatosensory Cortex?

1) Anterolateral System(Spinothalamic)

2) Dorsal Column System

Anterolateral System characteristics ?

1) processes pain & temperature

2) its 2nd order neuron immediately crosses to the opposite side of the spinal cord then ascends up the anterolateral column to thalamus

Dorsal Column System Characteristics ?

1) processes body movement, limb position, touch, pressure

2) 2nd neuron crosses at brainstem & up to the thalamus(3rd order neuron)

What nm wavelength is visible to human eye?

400-700nm

retina location & thickness?

back of the eye & extremely thin

What is refraction? What does this cause?

refraction→bending of light as it enters your eye

-causes image to be inverted on the retina

ex// top of tree you see is actually bottom of tree at retina

Accommodation ability of the eye? Which part of the eye allows for accommodation?

ability of eye to keep image focused on retina as distance between object & eyes vary

-the LENS

Ciliary muscle is ______ and the lens are ____ when you see Distant Objects.

relaxed; thin

Ciliary muscle is ______ and the lens are ____ when you see Near Objects.

contracted; thick

Terms for normal vision, nearsightedness, and farsightedness?

normal vision→emmetropia

nearsightedness→myopia

farsightedness→hyperopia

(myopia & hyperopia can be fixed with convex lens)

What are the 2 major components of the Retina?

1) Retinal Pigment Epithelium

2) Neural Retina →layers of neurons/cells

What are the layers of the Neural Retina that light has to pass through?

(Optic Nerve CN II)→Ganglion Cell→(amacrine cell)→Bipolar Cell→(horizontal cell)→ photoreceptors(rods & cones)

Horizontal cells vs. Amacrine cells

Horizontal cells→modulate signaling between photoreceptors & bipolar cells

Amacrine cells→modulate signaling between bipolar cells & ganglion cells

Which cells of the retina generate the action potential?

Ganglion cells →generate AP to the Optic Nerve(CN II)

(all other retinal neurons use graded potentials)

Purpose of the Muller Glia

help light pass through the ganglion & bipolar cell layers to reach the photoreceptors

(optical waveguide)

Fovea Centralis

center of the retina that has a LOT of cones(color +detail) & is for sharpest acuity/vision

Peripheral retina contains more….

rods→provide sensitivity to dim light

what are the 3 types of cones & the length of their wavelengths? (Trichromatic Theory)

1) blue (short wavelength)

2) green (medium wavelength)

3) red (longest wavelength)

What protein does each cone have?

opsin

explain the process of Phototransduction in a Cone cell. (when there is light exposure & when there is not)

in the dark, cGMP opens Na/Ca channels=ions go into cone cells=depolarized

in light, light hits the Opsin protein→ activates transducin→activates G-protein→activates phosphodiesterase→converts cGMP→GMP
(this closes the Na/Ca channels bc they need cGMP to stay open =repolarization

Most common color vision deficiency?

red-green color deficiency (X-linked recessive trait)→more common in males