Somatic: Eye Physiology

What are the two essential processes that must occur for vision?

Light rays must be focused on the retina and the resulting nerve impulses must be conducted to the visual areas of the cerebral cortex.

What is the role of photoreceptors in the retina?

Photoreceptors, namely rods and cones, capture images similarly to film in a camera when exposed to light.

What are the components that light passes through to reach the retina?

Cornea, anterior cavity (anterior chamber filled with aqueous humor), pupil, posterior chamber, lens, vitreous cavity (filled with vitreous humor), and then to the photoreceptors.

What is the function of the central fovea?

The central fovea is a tiny area in the back of the eye where light must be focused for clear vision.

What happens to light as it travels through different mediums in the eye?

Light is refracted or bent, which can change its direction as it passes through different densities of substances.

What determines the size of the pupil?

The radial and circular smooth muscle fibers control the pupil size, working antagonistically to allow more or less light into the eye.

What happens when the radial muscle fibers contract?

The pupil dilates, allowing more light to enter.

What action do circular muscle fibers perform when they contract?

They constrict the pupil, making it smaller.

What is accommodation in the context of vision?

Accommodation is the process by which the lens changes shape to focus on near or distant objects.

How do ciliary muscles affect the lens?

Ciliary muscles contract or relax to change the tension on suspensory ligaments, altering the shape of the lens for focusing.

What occurs when light hits the photoreceptors in the retina?

Chemical reactions are triggered, leading to graded potentials; if strong enough, these can generate action potentials.

Describe the pathway of nerve impulses from the retina to the brain.

Nerve impulses travel from photoreceptors to bipolar neurons, then to ganglion neurons, which send axons to the optic disc and exit the eye via the optic nerve.

What is the optic chiasm?

The point where the optic nerve fibers from each eye cross just below the hypothalamus.

In which part of the brain are visual signals integrated before reaching consciousness?

Visual signals pass through the thalamus before reaching the primary visual cortex in the occipital lobe.