Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

15. The Special Senses

Optic Components of the Eyeball

Anatomy & Physiology

15. The Special Senses

Optic Components of the Eyeball

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Problem 9

Textbook Question

Which cells in the retina are depolarized in darkness?
a. Rods and cones
b. Bipolar cells
c. Retinal ganglion cells
d. All of the above
e. Only rods

Verified step by step guidance

Understand the basic physiology of the retina: The retina contains photoreceptor cells (rods and cones), bipolar cells, and retinal ganglion cells. These cells work together to process visual information and transmit it to the brain.

Recall the behavior of photoreceptor cells (rods and cones) in darkness: In the absence of light, photoreceptor cells are depolarized because their sodium channels remain open due to the presence of cyclic GMP (cGMP). This allows a steady influx of sodium ions, known as the 'dark current.'

Understand the role of bipolar cells: Bipolar cells are not depolarized in darkness. Instead, they respond to the neurotransmitter glutamate released by depolarized photoreceptors. Depending on the type of bipolar cell (ON or OFF), they may be inhibited or activated in response to light.

Consider the retinal ganglion cells: Retinal ganglion cells are not directly depolarized in darkness. Their activity depends on the input they receive from bipolar cells, which is influenced by the presence or absence of light.

Conclude which cells are depolarized in darkness: Based on the above steps, only the photoreceptor cells (rods and cones) are depolarized in darkness due to the continuous influx of sodium ions through their open channels.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Phototransduction

Phototransduction is the process by which light is converted into electrical signals in the retina. In darkness, photoreceptor cells (rods and cones) are depolarized due to the continuous influx of sodium ions, leading to the release of neurotransmitters that inhibit bipolar cells.

Rods and Cones

Rods and cones are the two types of photoreceptor cells in the retina. Rods are highly sensitive to light and enable vision in low-light conditions, while cones are responsible for color vision and function best in bright light. In darkness, rods remain depolarized, contributing to the overall response of the retina.

Bipolar Cells

Bipolar cells are the intermediary neurons in the retina that connect photoreceptors to ganglion cells. In the dark, the inhibition from depolarized rods and cones prevents bipolar cells from depolarizing, which is essential for transmitting visual signals to the brain when light is present.

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