Chapter 15-17 Flashcards
What is the iris?
The colored part of the eye
What does the iris do?
Controls the size of the pupil
What is the pupil?
- central opening that regulates the amount of light entering the eye
Close vision and bright light
- pupils constrict
Distant vision and dim light
- pupils dilate
What is the term for farsightedness?
Hyperopia
Why can corneas be transplanted without fear of rejection?
- The cornea is avascular
- there are no antigens or antibodies for the recipients body to reject
Why does motion sickness occur?
- Sensory input mismatches
- Visual input differs from equilibrium input
- Conflicting information causes motion sickness
What special sense is not fully functional at birth?
Vision
What is the blind spot
- Optic disc (blind spot)
- The site where the optic nerve leaves the eye
- Lacks photoreceptors
What is the path of light through the eye?
- cornea
- aqueous humor
- lens
- vitreous humor
- entire neural layer of retina
- photoreceptors
What percentage of your sensory receptors are located in the eye?
70%
Define hormones
long-distance chemical signals; travel in blood or lymph
What is the “master endocrine gland?”
pituitary gland
What endocrine organ important in the immunity of a child?
Thymus
How do steroid hormones work?
- Diffuse into target cells and bind to intracellular receptors
- Receptor-hormone complex enters nucleus; binds to the specific region of DNA
- Prompts DNA transcription to produce mRNA
- mRNA directs protein synthesis
- Promote metabolic activities, or promote synthesis of structural proteins or proteins for export from the cell
Define up-regulation
target cells form more receptors in response to low hormone levels
