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Questions and Answers
Which of the following accurately describes the relationship between the sensory neuron, interneuron, and motor neuron in a reflex arc?
Which of the following accurately describes the relationship between the sensory neuron, interneuron, and motor neuron in a reflex arc?
- The motor neuron stimulates the sensory neuron, which then stimulates the interneuron.
- The interneuron directly stimulates the sensory and motor neurons simultaneously.
- The sensory neuron directly stimulates the motor neuron, bypassing the interneuron.
- The sensory neuron carries the message from the sensory organ to the interneuron, which then relays the message to the motor neuron. (correct)
Which of the following is the primary role of the myelin sheath found on some neurons?
Which of the following is the primary role of the myelin sheath found on some neurons?
- To provide structural support to the neuron.
- To increase the speed of action potential propagation along the axon. (correct)
- To synthesize neurotransmitters for synaptic transmission.
- To protect the neuron from physical damage.
If a nerve fiber is subjected to a stimulus below the threshold intensity, what will be the result?
If a nerve fiber is subjected to a stimulus below the threshold intensity, what will be the result?
- No action potential will be generated. (correct)
- An action potential will be generated with normal amplitude and speed.
- A partial action potential with reduced amplitude will be generated.
- An action potential will be generated, but it will propagate at a slower speed.
An injury to the vertebral column could directly endanger which component of the central nervous system?
An injury to the vertebral column could directly endanger which component of the central nervous system?
Which of the following statements accurately describes the relationship between axon diameter and the speed of nerve impulse propagation?
Which of the following statements accurately describes the relationship between axon diameter and the speed of nerve impulse propagation?
Damage to the medulla oblongata would most likely result in:
Damage to the medulla oblongata would most likely result in:
Which type of neuron is specialized to transmit messages from sensory receptors to the central nervous system?
Which type of neuron is specialized to transmit messages from sensory receptors to the central nervous system?
The terminal arborizations of a neuron are responsible for:
The terminal arborizations of a neuron are responsible for:
Based on the structural classification of neurons, a neuron with one axon and one dendrite extending from the cell body is classified as:
Based on the structural classification of neurons, a neuron with one axon and one dendrite extending from the cell body is classified as:
How will an increase in temperature typically affect the speed of action potential propagation in a neuron?
How will an increase in temperature typically affect the speed of action potential propagation in a neuron?
Flashcards
Central Nervous System
Central Nervous System
The central nervous system consists of the brain and spinal cord.
Peripheral Nervous System
Peripheral Nervous System
The peripheral nervous system includes cranial and spinal nerves.
Neuron
Neuron
The functional unit of the nervous system, transmits signals.
Dendrites
Dendrites
Short, cytoplasmic extensions that receive signals.
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Axon
Axon
Long cytoplasmic extension that transmits signals.
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Cell Body
Cell Body
Contains the nucleus of the neuron and integrates signals.
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Myelin Sheath
Myelin Sheath
Formed from Schwann cells wrapping nerve fibers, speeds up signal transmission.
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Sensory vs. Effector Organ
Sensory vs. Effector Organ
Sensory organ receives stimulus, effector organ responds.
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Reflex Action
Reflex Action
Heat stimulates sensory organ, muscles contract to pull away.
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Threshold Intensity
Threshold Intensity
Minimum intensity of stimulus needed to generate an action potential.
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Nervous System Structure
- The nervous system divides into the Peripheral Nervous System (PNS) and the Central Nervous System (CNS)
Peripheral Nervous System
- Contains cranial nerves and spinal nerves
Central Nervous System
- Contains the Brain and Spinal Cord
Brain
- Comprises the cerebrum, cerebellum, and medulla oblongata
- The skull protects the brain
Spinal Cord
- Located in the vertebral column
- It is protected by the vertebral column
Neuron
- The structural and functional unit of the nervous system is the neuron
- A neuron is composed of dendrites, an axon, and a cell body
Neuron Components
- Cell Body: Contains the nucleus
- Dendrites: Short cytoplasmic prolongations
- Axon: Long cytoplasmic prolongation ending in terminal arborizations that contain synaptic vesicles
Nerve Fibers
- Some nerve fibers are myelinated and others are non-myelinated
- Myelin sheath is formed from a Schwan cell wrapping around the axon/nerve fiber.
Types of Neurons based on structure
- Bipolar neuron
- Multipolar neuron
- Unipolar neuron
Reflex Action
- Reflex action occurs upon subjecting the finger skin to a hot object, causing the subject to pull away their arm
- STIMULUS: Heat stimulates the sensory organ
- RESPONSE: Pulling away the arm is due to contraction of muscle fiber
Reflex Arc
- The sensory organ receives a stimulus and initiates a nerve message
- The effector organ receives a nerve message and responds to it
- Sensory neuron carries the message from the sensory organ to the spinal cord or brain
- Interneuron transmits the message from the sensory neuron to the motor neuron
- Motor neuron carries the nerve message from the CNS (spinal cord) to the effector organ
Nerve Signal Propagation
- A nerve message propagates along the nerve fiber with constant speed and amplitude
- No action potential equals ineffective stimulation
- Threshold intensity is the minimum intensity that generates an action potential
- Nerve Fiber obeys the rule of all or none: before threshold zero, after threshold constant amplitude
- Nerves do not obey the rule of all or none (global potential or summation of action potential)
Speed of Propagation Factors
- Diameter: an increase in diameter causes an increase in speed of propagation
- Presence of myelin sheet: due to node of Ranvier
- Temperature: an increase in temperature causes an increase in speed of propagation of action potential
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