Vision, Endocrine System, and Blood Review Flashcards

Practice vocabulary flashcards covering vision anatomy and physiology, the endocrine system's hormones and control mechanisms, and the components and functions of blood based on the lecture review sheets.

Lacrimal glands

Glands that moisten the eyes and secrete antibodies.

Macula

The point of focus for detailed vision where cones are concentrated; also known as the fovea.

Choroid

The layer of the eye that absorbs light entering the eye.

Lens

The structure that focuses light; it rounds up (thickens) for near vision and flattens for distance vision.

Aqueous humor

The fluid in the eye produced by the ciliary body and drained through the canal of Schlemm.

Glaucoma

A pathology caused by a build-up of intraocular pressure, often due to a blockage of the canal of Schlemm.

Refraction

The bending of light rays.

Accommodation

The rounding of the lens for near vision to focus light rays from a nearby object on the fovea.

Convergence

Focusing both eyes on the same object to improve depth perception, primarily involving the medial rectus muscles.

Rods

Photoreceptors for black and white vision found on the periphery (edges) of the retina.

Rhodopsin

A pigment in rods that breaks down into opsin (a protein) and retinal (a vitamin A derivative) in light.

Dark adaptation

The 10 – 20 minute adjustment of the eyes from bright light to dim light as rhodopsin builds back up.

Night blindness

A condition often caused by a lack of rhodopsin or Vitamin A.

Iodopsins

Pigments in cones (blue-sensitive, green-sensitive, and red-sensitive) whose build-up requires ATP.

Cranial nerve II

The optic nerve where the breakdown of iodopsins initiates an action potential.

Hypothalamus hormones

Includes growth hormone releasing hormone, thyrotropin releasing hormone (TRH), corticotrophin releasing hormone (CRH), and gonadotropin releasing hormone (GnRH).

Corticotrophin releasing hormone (CRH)

A hormone released from the hypothalamus that targets the anterior pituitary.

Oxytocin

A hormone released by the posterior pituitary that targets the breast and uterus to promote contractions and milk release.

Growth hormone (GH)

An anterior pituitary hormone that targets most tissues of the body.

Calcitonin

A hormone that targets osteoclasts to help regulate blood calcium.

Thymosin

A hormone responsible for the development of the immune system.

Insulin

A hormone that lowers blood glucose by allowing it to enter body cells.

Parathyroid hormone (PTH)

A hormone that raises blood calcium levels via action on bone, kidney, and small intestines.

Chronic hormone secretion

A pattern of secretion at relatively constant levels, such as thyroxine.

Acute hormone secretion

A pattern of secretion where hormones are released in large amounts in response to a stimulus, such as epinephrine.

Episodic (Cyclic) hormone secretion

A pattern where hormone levels increase and decrease in a cycle, such as cortisol or the female monthly cycle.

Target cell

A cell that possesses specific receptors for a particular hormone.

Down regulation

A decrease in the number of receptors that causes a target cell to become less sensitive to a hormone.

Nuclear receptors

Receptors for lipid-soluble hormones that activate DNA, resulting in a slow response time.

Membrane-bound receptors

Receptors for water-soluble hormones that activate intracellular molecules, resulting in a rapid response time.

Cascade effect

A rapid and amplified response associated with membrane-bound receptors.

Prostaglandins

Chemical signals secreted into interstitial fluid instead of blood that affect smooth muscle contraction, blood clotting, and inflammation.

Erythrocytes

Also known as red blood cells (RBCs), these biconcave disks carry oxygen between the lungs and body cells.

Hemoglobin

A protein in RBCs; the iron on the heme part carries up to 4 oxygen molecules.

Anemia

A condition characterized by a lack of sufficient RBCs or hemoglobin.

Leukocytes

Also known as white blood cells (WBCs), these cells exhibit amoeboid movement and help protect against infection.

Chemotaxis

The process by which leukocytes are attracted to foreign or dead cells.

Granulocytes

A category of white blood cells that includes neutrophils, basophils, and eosinophils.

Agranulocytes

A category of white blood cells that includes lymphocytes and monocytes.

Platelets

Fragments of megakaryocytes involved in blood clotting with a typically short life span.

Serum albumin

The most abundant plasma protein, important for maintaining the osmotic concentration of the blood.

Hematocrit

The percentage of total blood volume composed of RBCs, approximately $45\%$ in adult males.

Leucocytosis

An elevated white blood cell count.

Reticulocytes

Immature red blood cells.

Hemostasis

The three-step process to stop bleeding: 1. Vascular spasm, 2. platelet plug formation, 3. coagulation.

Prothrombinase

The enzyme that activates prothrombin; its production requires calcium.

Thrombin

The enzyme that activates fibrinogen into fibrin for clot formation.

Antigen

A molecule on the surface of cells (like RBCs) that can stimulate an attack by antibodies.

Hematopoiesis

The process of blood cell formation.

Erythropoietin

A hormone whose production increases when blood oxygen decreases, stimulating red blood cell formation.