Intro to the Visual System

What is the visual system a part of?

Central nervous system

What are the two ocular structures that make up the majority of the refractive power of the eye?

Cornea and lens which focus the light on the retina.

What makes up the outer tunic?

Fibrous connective tissue (e.g. cornea and sclera)

What makes up the middle tunic?

Vascular structures, uvea (blood supply)

(e.g. iris, ciliary body, choroid)

What makes up the inner tunic?

Neural (e.g. retina)

Where is the anterior chamber located?

B/w cornea and iris.

Where is the posterior chamber located?

B/w iris and lens.

Where is the vitreous chamber located?

B/w lens and retina.

What is emmetropia?

Refractive power of the cornea + lens, where the image is focused on the retina.

What is hyperopia?

The refractive power of cornea + lens, where the image is behind the retina.

What is myopia?

Refractive power of cornea + lens, where the image is focused in front of the retina.

What is the sagittal/median plane?

A vertical plane that divide the body into right/left.

What is the coronal/frontal plane?

It is a vertical plane that divides body into anterior/posterior.

What is the axial/transverse/horizontal plane?

A horizontal plane that divides structures into superior/inferior.

What is epithelial tissue and its role?

Type of tissue that covers external surfaces and lines cavities.

Roles: Protection, absorption, filtration, secretion. (e.g. using microvilli to increase surface area to absorb nutrients)

Where can we find the basement membrane?

It is attached to underlying connective tissue.

What forms the basal lamina?

The epithelial cell which secretes it.

What forms the reticular lamina?

The underlying connective tissue secretes it.

What are unicellular glands?

They are glands that consist of a single secretory cell (e.g. goblet cells).

What are multicellular glands?

Glands that are composed of clusters of secretory cells (e.g. lacrimal gland)

What are exocrine glands?

Type of gland that secretes products through ducts (e.g. lacrimal gland, sweat gland, salivary gland).

What are endocrine glands?

Type of gland that secrete products directly into the bloodstream (e.g. thyroid gland).

What are the three classifications of exocrine glands?

Merocrine: secrete secretory product only

Apocrine: secretes part of the cell cytoplasm with secretory products

Holocrine: secretes complete cells containing secretory products

What are three types of exocrine gland secretions?

Sebaceous: secrete sebum/oils (e.g. meibomian glands)

Serous: secrete watery and protein-rich fluid (e.g. lacrimal gland)

Mucous: secrete mucus, which is a thick, carbohydrate-rich substance (e.g. goblet cells)

What is the role of connective tissue?

Provides structure, support, connection, and nutrition to other tissues.

What are connective tissue composed of?

Ground substance + fibers + cells

What is the extracellular matrix composed of?

Ground substance + fibers

What are fibroblasts?

Cells that produce and maintain fibers and ground substance (e.g. keratocytes in cornea).

What are macrophages?

Immune cells that are responsible for phagocytosis and cytokine release.

What are mast cells and where can they be found?

Immune cells that contain heparin and histamine (found in cornea and conjunctiva).

What are adipocytes and where are they found?

Cells that store lipids and fat. They are found in the orbital fat.

What are two types of striated muscles?

Skeletal (voluntary) and cardiac (involuntary)

What is an example of a smooth muscle (involuntary)?

Muscles within the iris.

What muscles are voluntary and involuntary?

Striated (both) and smooth (involuntary)

What are neuroglia?

Cells that provide structure and metabolic support to neurons.

What kind of communication is expressed between pre-synaptic and post-synaptic neurons?

Chemical and neural communication

What happens after neurotransmitters get released into the synapse?

• They bind receptors on post-synaptic neurons.

• Trigger excitatory or inhibitory responses.

What kind of junctions connect cells?

Mostly cell-to-cell and some cell to basement membrane

What are tight junctions?

Fused connections between membranes and cytoskeletons of adjacent cells.

They are impermeable and used in epithelium for barrier function.

What are two examples of tight junctions?

Zonula occludens (ZO): encircles entire cell

Macula occludens (MO): localized

What are anchoring junctions?

Attachments that increase cell stability.

What are some examples of anchoring junctions?

Zonula adherens (ZA): encircle entire cell

Macula adherens (MA): localized

Desmosome: connects cell to cell

Hemidesmosome: connect cell to basement membrane (extend into cytoplasm and underlying connective tissue)

What are gap junctions?

A group of connexin proteins from one cell join to connexins from another cell (forms connexon)

What do gap junctions allow passage to?

Allows ions and small molecules to pass through.