Table of contents

1. Introduction to Biology2h 42m
2. Chemistry3h 37m
3. Water1h 26m
4. Biomolecules2h 23m
5. Cell Components2h 26m
6. The Membrane2h 31m
7. Energy and Metabolism2h 0m
8. Respiration2h 40m
9. Photosynthesis2h 49m
10. Cell Signaling59m
11. Cell Division2h 47m
12. Meiosis2h 0m
13. Mendelian Genetics4h 44m
14. DNA Synthesis2h 27m
15. Gene Expression3h 6m
16. Regulation of Expression3h 31m
17. Viruses37m
- Viruses
  37m
18. Biotechnology2h 58m
19. Genomics17m
- Genomes
  17m
20. Development1h 5m
21. Evolution3h 1m
22. Evolution of Populations3h 53m
23. Speciation1h 37m
24. History of Life on Earth2h 6m
25. Phylogeny2h 31m
26. Prokaryotes4h 59m
27. Protists1h 12m
28. Plants1h 22m
29. Fungi36m
- Fungi
  19m
- Fungi Reproduction
  17m
30. Overview of Animals34m
- Overview of Animals
  34m
31. Invertebrates1h 2m
32. Vertebrates50m
33. Plant Anatomy1h 3m
34. Vascular Plant Transport1h 2m
- Water Potential
  1h 2m
35. Soil37m
- Soil and Nutrients
  20m
- Nitrogen Fixation
  16m
36. Plant Reproduction47m
- Flowers
  33m
- Seeds
  14m
37. Plant Sensation and Response1h 9m
38. Animal Form and Function1h 19m
39. Digestive System1h 10m
- Digestion
  1h 3m
- Blood Sugar Homeostasis
  7m
40. Circulatory System1h 49m
41. Immune System1h 12m
42. Osmoregulation and Excretion50m
- Osmoregulation and Excretion
  50m
43. Endocrine System1h 4m
- Endocrine System
  1h 4m
44. Animal Reproduction1h 2m
- Animal Reproduction
  1h 2m
45. Nervous System1h 55m
- Neurons and Action Potentials
  1h 8m
- Central and Peripheral Nervous System
  46m
46. Sensory Systems46m
- Sensory System
  46m
47. Muscle Systems23m
- Musculoskeletal System
  23m
48. Ecology3h 11m
49. Animal Behavior28m
- Animal Behavior
  28m
50. Population Ecology3h 41m
51. Community Ecology2h 46m
52. Ecosystems2h 36m
53. Conservation Biology24m
- Conservation Biology
  24m

10. Cell Signaling

Introduction to Cell Signaling

General Biology

10. Cell Signaling

Introduction to Cell Signaling

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Multiple Choice

Which brain defense mechanism restricts substances from entering the brain via the vascular system?

Meninges

Myelin sheath

Blood-brain barrier

Cerebrospinal fluid

Previous problemNext problem

Verified step by step guidance

Understand the problem: The question is asking about a brain defense mechanism that restricts substances from entering the brain through the vascular system. This means we need to identify the structure or system responsible for controlling the passage of substances from the bloodstream into the brain.

Clarify the options: Review each option provided: (1) Meninges, which are protective layers surrounding the brain and spinal cord; (2) Myelin sheath, which insulates nerve fibers to enhance signal transmission; (3) Blood-brain barrier, a selective barrier that regulates the entry of substances into the brain; and (4) Cerebrospinal fluid, which cushions the brain and spinal cord and provides nutrients.

Focus on the correct concept: The blood-brain barrier is a specialized structure formed by endothelial cells lining the brain's capillaries. These cells are tightly joined, creating a selective barrier that allows essential nutrients to pass while blocking harmful substances.

Explain the mechanism: The blood-brain barrier functions through tight junctions between endothelial cells, supported by astrocytes. It uses selective transport mechanisms to allow molecules like glucose and amino acids to enter while preventing toxins and pathogens from crossing.

Conclude the reasoning: Based on the description and function, the blood-brain barrier is the correct answer because it specifically restricts substances from entering the brain via the vascular system, unlike the other options which serve different roles in brain protection or function.