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Questions and Answers
What is the primary function of sensory nerves?
What is the primary function of sensory nerves?
Which type of nerve is responsible for controlling muscle and gland functions?
Which type of nerve is responsible for controlling muscle and gland functions?
What is a synapse?
What is a synapse?
What role do neurotransmitters play in the nervous system?
What role do neurotransmitters play in the nervous system?
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Which of the following best describes reflex arcs?
Which of the following best describes reflex arcs?
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What is another name for synapses between nerve and muscle cells?
What is another name for synapses between nerve and muscle cells?
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Which term describes the signals sent by sensory nerves?
Which term describes the signals sent by sensory nerves?
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What distinguishes motor nerves from sensory nerves?
What distinguishes motor nerves from sensory nerves?
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What are action potentials characterized by?
What are action potentials characterized by?
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Which type of channels open during the depolarization phase of an action potential?
Which type of channels open during the depolarization phase of an action potential?
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What happens to the membrane potential after K+ channels open?
What happens to the membrane potential after K+ channels open?
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How does the strength of an action potential change as it travels?
How does the strength of an action potential change as it travels?
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What initiates an action potential?
What initiates an action potential?
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What is the resting membrane potential typically around?
What is the resting membrane potential typically around?
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What is the main function of voltage-gated K+ channels during an action potential?
What is the main function of voltage-gated K+ channels during an action potential?
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What occurs after the closing of voltage-gated Na+ channels during an action potential?
What occurs after the closing of voltage-gated Na+ channels during an action potential?
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What occurs when the membrane reaches the threshold potential?
What occurs when the membrane reaches the threshold potential?
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What is the threshold potential at which an action potential is generated?
What is the threshold potential at which an action potential is generated?
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What primarily causes the flow of sodium ions into the intracellular fluid (ICF)?
What primarily causes the flow of sodium ions into the intracellular fluid (ICF)?
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What is responsible for restoring the membrane potential to its resting state?
What is responsible for restoring the membrane potential to its resting state?
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During the absolute refractory period, what is primarily inactivated?
During the absolute refractory period, what is primarily inactivated?
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What is one consequence of K+ movement out of the cell during repolarization?
What is one consequence of K+ movement out of the cell during repolarization?
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How does the refractory period affect action potentials?
How does the refractory period affect action potentials?
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What result does the opening of VGPCs during repolarization lead to?
What result does the opening of VGPCs during repolarization lead to?
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What drains into the T-tubes in skeletal muscle?
What drains into the T-tubes in skeletal muscle?
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What type of neurons run from the CNS to the muscles and glands?
What type of neurons run from the CNS to the muscles and glands?
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Where are the cell bodies of motor neurons located?
Where are the cell bodies of motor neurons located?
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What occurs at the neuromuscular junction?
What occurs at the neuromuscular junction?
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What do action potentials traveling down motor neurons cause?
What do action potentials traveling down motor neurons cause?
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What is created from a single vesicle release at the neuromuscular junction?
What is created from a single vesicle release at the neuromuscular junction?
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What type of muscle fibers are innervated by motor neurons?
What type of muscle fibers are innervated by motor neurons?
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What forms a chemical synapse at the neuromuscular junction?
What forms a chemical synapse at the neuromuscular junction?
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What is the primary function of sensory neurons?
What is the primary function of sensory neurons?
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Which part of the nervous system is responsible for voluntary movements?
Which part of the nervous system is responsible for voluntary movements?
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What defines a neurotransmitter?
What defines a neurotransmitter?
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During neurotransmission at the neuromuscular junction, which enzyme degrades the neurotransmitter acetylcholine?
During neurotransmission at the neuromuscular junction, which enzyme degrades the neurotransmitter acetylcholine?
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Which of the following best describes nicotinic receptors at the neuromuscular junction?
Which of the following best describes nicotinic receptors at the neuromuscular junction?
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Which division of the peripheral nervous system is responsible for involuntary control of smooth muscles?
Which division of the peripheral nervous system is responsible for involuntary control of smooth muscles?
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What occurs during depolarization of the plasma membrane?
What occurs during depolarization of the plasma membrane?
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What is the role of the axon in a neuron?
What is the role of the axon in a neuron?
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Which type of neuron would have multiple projections from its cell body?
Which type of neuron would have multiple projections from its cell body?
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Which system is NOT part of the autonomic nervous system?
Which system is NOT part of the autonomic nervous system?
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Study Notes
Organization of the Nervous System
- The nervous system is divided into the central nervous system (CNS) and the peripheral nervous system (PNS).
- The CNS consists of the brain and spinal cord.
- The PNS consists of sensory nerves (afferent nerves) and motor nerves (efferent nerves)
- The PNS can be further divided into the afferent division and the efferent division.
- The afferent division transmits information from the body to the CNS (arriving).
- The efferent division transmits information from the CNS to the body (exiting, effector organ)
- The efferent division can be further divided into the somatic nervous system and the autonomic nervous system.
- The somatic nervous system controls skeletal muscle.
- The autonomic nervous system controls smooth muscle, cardiac muscle, exocrine glands, and some endocrine glands.
- The autonomic nervous system has three subdivisions: sympathetic, parasympathetic, and enteric.
Structural Units of the Nervous System: Neurons
- Neurons have a cell body (soma), dendrites, and an axon.
- Dendrites are projections from the cell body that receive impulses.
- Axons are projections from the cell body that transmit impulses.
- The axon hillock is the section where the axon begins.
- The telodendron is the end of the axon.
- The synaptic terminal is the end of the telodendron where the neuron makes a connection with another cell.
Signal Transduction
- Dendrites or the cell body receive signals that cause a depolarization or hyperpolarization of the plasma membrane.
- Axons propagate output signals: action potentials.
Ways to Classify Neurons (I)
- Morphology (shape) : Neurons are classified as bipolar (two projections from cell body) or multipolar (multiple projections from cell body)
- Afferent and Efferent nerves: Neurons that transmit information towards the CNS are afferent (arriving). Neurons that transmit information from the CNS are efferent (exiting, effector organ).
- Neurotransmitter: Neurons are classified by the substance or chemical they release (e.g. dopamine, acetylcholine).
Functional Ways to Classify Neurons/Nerves (II)
- Sensory nerves send information to the CNS about the internal and external environment.
- Motor nerves control the activity of the body by controlling muscle and gland functions.
- The motor response to sensory input requires integration of information through interconnections between nerves and reflex arcs.
The Synapse
- The synapse is the junction between one neuron and the next cell.
- Specialised structures at the synapse convert electrical impulses to chemical signals for communication between cells (electro-chemical coupling).
- Types of synapse:
- Nerve-Nerve
- Nerve-Organ / Organ-Nerve
- Nerve-Muscle
- Nerve-Gland
- Synapses between nerve and muscle cells are also called neuromuscular junctions or motor end plates.
Neurotransmitters
- Neurotransmitters are typically small, rapid-acting molecules (e.g. dopamine, acetylcholine).
Potentials (II): Action Potentials
- Action potentials (APs) are brief, rapid, large changes in membrane potential, during which the potential reverses.
- APs involve only a small portion of the total excitable cell membrane at any given time.
- APs do not decrease in strength as they travel from their site of initiation.
The Refractory Period - One Way Traffic
- The refractory period is the time during which a further stimulus applied to the neuron or muscle fiber will not trigger another action potential.
- The refractory period is due to the inactivation of sodium channels (absolute refractory period) and repolarization brought about by the opening of potassium channels and potassium ions (K+) movement out of the cell (relative refractory period).
Skeletal Muscle
- Skeletal muscle is controlled by the somatic nervous system.
Peripheral Nervous System & Nerve-Muscle Junctions
- The output of the PNS consists of motor neurons running from the CNS to the muscles and glands - called effectors - that take action.
- Nerve (somatic motor nerves) – skeletal muscle – neuromuscular junction (NMJ).
- Nerve (Autonomic NS) – cardiac or smooth muscle.
Motor Neurons Innervate Skeletal Muscle Fibers
- Cell bodies of motor neurons are located in the ventral horn of the spinal cord.
- These neurons have thick, myelinated axons (somatic efferent fiber).
- Motor neurons lose their myelin sheath at the motor end plate.
- At the motor end plate, each axon terminal forms a neuromuscular junction with a single muscle fiber.
The Neuromuscular Junction (I)
- Motor neurons and skeletal muscle fibers are chemically linked at the NMJ.
- Action potentials traveling down motor neurons cause the contraction of skeletal muscle fibers.
- The NMJ is always excitatory.
- Single vesicle release at the NMJ creates miniature end plate potentials (mEPP).
- Action potentials release neurotransmitter acetylcholine (ACh).
Neuromuscular Junction
- The NMJ is a chemical synapse between a motor neuron and a muscle fiber.
- The NMJ is responsible for the transmission of nerve impulses from a motor neuron to a muscle fiber.
- The NMJ is essential for the activation of muscle contraction.
What is a Neuromuscular Junction?
- A chemical synapse between a motor neuron and a muscle fiber.
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Description
Test your knowledge on the organization of the nervous system, including the central and peripheral nervous systems. This quiz covers the divisions of the PNS, the somatic and autonomic nervous systems, and the functional roles of neurons. Challenge yourself to understand how these systems work together to transmit information in the body.