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

11. Nervous Tissue and Nervous System

Graded Potentials

Anatomy & Physiology

11. Nervous Tissue and Nervous System

Graded Potentials

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2:46 minutes

Problem 9

Textbook Question

An IPSP is inhibitory because
a. It hyperpolarizes the postsynaptic membrane.
b. It reduces the amount of neurotransmitter released by the presynaptic terminal.
c. It prevents calcium ion entry into the presynaptic terminal.
d. It changes the threshold of the neuron.

Verified step by step guidance

Understand the concept of an IPSP (Inhibitory Postsynaptic Potential): An IPSP is a type of synaptic potential that makes a postsynaptic neuron less likely to generate an action potential. It is inhibitory in nature and typically involves hyperpolarization of the postsynaptic membrane.

Review the mechanism of hyperpolarization: Hyperpolarization occurs when the membrane potential becomes more negative than the resting potential. This is often due to the opening of ion channels that allow negatively charged ions (e.g., Cl⁻) to enter the cell or positively charged ions (e.g., K⁺) to leave the cell.

Analyze the options provided: Option (a) states that an IPSP hyperpolarizes the postsynaptic membrane, which aligns with the definition of an IPSP. Option (b) refers to neurotransmitter release, which is a presynaptic event and not directly related to IPSPs. Option (c) mentions calcium ion entry into the presynaptic terminal, which is also unrelated to IPSPs. Option (d) suggests a change in the threshold of the neuron, which is not the primary mechanism of IPSPs.

Correlate the correct physiological process with the inhibitory effect: IPSPs decrease the likelihood of an action potential by moving the membrane potential further away from the threshold for activation. This inhibitory effect is achieved through hyperpolarization, as described in option (a).

Conclude that the correct answer is based on the physiological mechanism of hyperpolarization, which directly explains why an IPSP is inhibitory.

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Key Concepts

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

IPSP (Inhibitory Postsynaptic Potential)

An IPSP is a type of synaptic potential that makes a postsynaptic neuron less likely to fire an action potential. It typically occurs when neurotransmitters bind to receptors that open ion channels, allowing negatively charged ions to enter the neuron or positively charged ions to exit, leading to hyperpolarization of the membrane.

Hyperpolarization

Hyperpolarization refers to an increase in the membrane potential of a neuron, making it more negative than its resting potential. This change decreases the likelihood of the neuron reaching the threshold needed to trigger an action potential, thus inhibiting neuronal firing and signaling.

Neurotransmitter Release

Neurotransmitter release is the process by which signaling molecules are released from the presynaptic terminal into the synaptic cleft. In the context of IPSPs, certain mechanisms can reduce the amount of neurotransmitter released, further contributing to the inhibitory effect on the postsynaptic neuron.

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