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Questions and Answers
What is the functional unit of the nervous system?
What is the functional unit of the nervous system?
Which part of the nervous system includes cranial nerves?
Which part of the nervous system includes cranial nerves?
What type of stimulus has an intensity less than the threshold?
What type of stimulus has an intensity less than the threshold?
Which of the following is not part of the Central Nervous System (CNS)?
Which of the following is not part of the Central Nervous System (CNS)?
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What is the primary characteristic of an excitable tissue?
What is the primary characteristic of an excitable tissue?
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Which classification of the nervous system is responsible for involuntary movements?
Which classification of the nervous system is responsible for involuntary movements?
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How is a nerve impulse transmitted once generated?
How is a nerve impulse transmitted once generated?
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Which of the following is an example of a mechanical stimulus?
Which of the following is an example of a mechanical stimulus?
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What is not a function of action potentials?
What is not a function of action potentials?
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Which type of nerve fiber is primarily responsible for transmitting sensory information?
Which type of nerve fiber is primarily responsible for transmitting sensory information?
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What type of conduction occurs in myelinated nerve fibers?
What type of conduction occurs in myelinated nerve fibers?
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Which of the following best describes the 'All or None Law'?
Which of the following best describes the 'All or None Law'?
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What is the primary consequence of a subthreshold stimulus?
What is the primary consequence of a subthreshold stimulus?
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During which phase is nerve excitability higher than normal?
During which phase is nerve excitability higher than normal?
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Which ion's release is crucial for initiating skeletal muscle contraction?
Which ion's release is crucial for initiating skeletal muscle contraction?
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What is necessary for the continuation of the contraction cycle in muscle fibers?
What is necessary for the continuation of the contraction cycle in muscle fibers?
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What primarily provides energy during nerve impulse propagation?
What primarily provides energy during nerve impulse propagation?
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Which of the following types of muscle does not obey the 'All or None Law'?
Which of the following types of muscle does not obey the 'All or None Law'?
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What happens when the end plate potential reaches the firing level in muscle contraction?
What happens when the end plate potential reaches the firing level in muscle contraction?
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What characterizes the local responses produced by subthreshold stimuli?
What characterizes the local responses produced by subthreshold stimuli?
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Study Notes
Nervous System - Excitable Tissues
- The neuron is the structural unit of the nervous system.
- Reflex action is the functional unit, occurring via a reflex arc (receptor, afferent, center, efferent, and effector).
- Anatomical classification of the nervous system includes:
- Central Nervous System (CNS):
- Brain (cerebrum, subcortical centers, cerebellum, brain stem)
- Spinal cord (31 segments, with horns and columns)
- Peripheral Nervous System (PNS):
- 12 pairs of cranial nerves
- 31 pairs of spinal nerves
- Central Nervous System (CNS):
- Physiological classification includes:
- Sensory part: transmits sensations from receptors to sensory centers (Somatic, Visceral, and Special).
- Motor part: transmits orders from motor centers to effector organs (Somatic and Autonomic).
- The common physiological classification includes 3 main divisions:
- CNS: Somatic (sensory and motor)
- ANS (Autonomic nervous system)
- Special senses
Nerve Properties
-
Excitability:
- Nerves respond to stimuli (changes in the environment, e.g., electrical, chemical, mechanical, thermal).
- Threshold stimulus: Minimal intensity needed for a response.
- Subthreshold stimulus: Intensity less than the threshold.
- Suprathreshold stimulus: Intensity greater than the threshold.
- Nerve responses involve electrical changes (action potentials), excitability changes, metabolic changes, and thermal changes.
-
Conductivity:
- Once initiated, nerve impulses travel along the nerve fiber.
- Types of nerve impulse conduction:
- Unmyelinated: sweeping conduction
- Myelinated: saltatory conduction
All-or-None Law
- Nerve either responds maximally or not at all to a stimulus (provided other factors remain constant).
- Applies to: single nerve fiber, single motor unit, cardiac muscle, unitary smooth muscle.
- Does not apply to: whole skeletal muscle, nerve trunk, multiunit smooth muscle.
Summation
- Subthreshold stimuli, if applied successively within a short period, can sum to produce an action potential.
Adaptation (Accommodation)
- Nerve fibers adapt quickly to constant or gradually increasing stimuli.
- Complete adaptation does not occur for stimuli with fluctuating intensity.
Infatigability
- Nerve fibers do not become fatigued by repeated stimulation.
Electrical Changes - Resting Membrane Potential (RMP)
- RMP is the voltage difference across the nerve cell membrane at rest.
- The cell membrane is polarized at rest: outside positive, inside negative.
- Factors affecting RMP: selective permeability of the membrane, presence of ion channels, Na+/K+ pump.
Electrical Changes - Action Potential
- Depolarization: increase in membrane potential toward zero (or positive).
- Repolarization: return to the resting membrane potential.
- After-potentials: small changes in membrane potential following repolarization (hyperpolarization, then depolarization).
Neuromuscular Transmission
- Explains how nerves communicate with muscles.
- Action potentials in motor neurons trigger the release of neurotransmitters (e.g., acetylcholine), which cause muscle contraction.
Mechanism of Skeletal Muscle Contraction
- Depolarization of the muscle fiber initiates the contraction process.
- Release of Ca²⁺ from the sarcoplasmic reticulum results in cross-bridge formation, leading to muscle shortening.
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Description
This quiz covers the fundamental concepts of the nervous system, focusing on excitable tissues such as neurons and their classification. It includes details about the central and peripheral nervous systems, as well as the physiological functions of sensory and motor systems. Test your knowledge on the essential components and functions of the nervous system!
