Photoreceptors, Visual Pathways, and Endocrine System Vocabulary

Flashcards covering the vocabulary of photoreceptors, photopigments, visual pathways, and the endocrine system based on the lecture notes.

Photoreceptors

Sensory cells that respond to light.

Rods

Receptors in the eye that change shape in response to light; concentrated on periphery of retina.

Rhodopsin

Photopigment in rods, responsible for low-light vision, high sensitivity, and no color perception.

Cones

Receptors in the eye responsible for color vision and high-resolution vision; concentrated at fovea centralis.

Optic Chiasm

Point where optic nerves from each eye cross, allowing visual information from one side of the visual field to be processed by the opposite side of the brain.

Hemidecussation

Half crossover, where only some nerve fibers cross to the other side.

Lateral Geniculate Nucleus

Relay center in the thalamus for the visual pathway.

Visual Cortex

Part of the brain that processes visual information.

Nervous System

Communicates by means of electrical impulses and neurotransmitters; reacts quickly to stimuli.

Endocrine System

Communicates by means of hormones released into the bloodstream; reacts more slowly to stimuli.

Exocrine Glands

Secrete substances onto a surface or into tracts via ducts (e.g., sweat glands, digestive enzymes).

Endocrine Glands

Secrete hormones inside the body, directly into the bloodstream; have no ducts.

Paracrine Agent

Chemical messengers that act on nearby cells via interstitial fluid.

Autocrine Agent

Chemical messengers that act on the cell that secretes them.

Hormone Receptors

Determine which tissues respond to a hormone.

Steroids

Hormones derived from cholesterol; typically hydrophobic and bind to intracellular receptors.

Monoamines

Hormones derived from amino acids.

Peptides

Hormones composed of amino acids; typically hydrophilic and bind to extracellular receptors.

Adenohypophysis

Anterior pituitary; develops from epithelial tissue in the mouth.

Neurohypophysis

Posterior pituitary; develops from nervous tissue in the brain.