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Questions and Answers
What type of junction connects the motor neuron to the muscle fiber?
What is the primary neurotransmitter synthesized at the neuromuscular junction?
During resting conditions, what is the typical range of membrane potential for nervous and muscular tissues?
What causes a muscle fiber to initiate an action potential?
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What term describes the ability of nerve and muscle cells to respond to stimuli?
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What is the primary effect of depolarization on a cell membrane?
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What is referred to as the potential difference in a resting cell membrane?
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What happens to the membrane potential during depolarization?
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What is the primary function of afferent neurons in the peripheral nervous system?
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Which part of the nervous system includes the spinal cord and the brain?
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What characterizes mixed nerves in the peripheral nervous system?
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What do upper motor neurons refer to within the context of the nervous system?
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What is the structure referred to as the 'motor unit' in muscle physiology?
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What is the role of the myelin sheath in nerve fibers?
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How do action potentials affect muscle contraction?
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Which type of neurons are primarily responsible for innervating skeletal muscles?
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What happens to the I band during muscle contraction?
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Which statement best describes the H band during muscle contraction?
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What is the role of cross bridges during muscle activity?
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Which component of a sarcomere anchors the actin filaments?
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What occurs to the Z lines as a muscle contracts?
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Which of the following correctly describes the Sliding Filament Theory?
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What characterizes the A band in a resting muscle fiber?
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What structural feature allows myosin heads to project laterally during muscle activation?
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What is the primary role of the epimysium in muscle structure?
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How are myofibrils within a muscle fiber structured?
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What distinguishes the A band in skeletal muscle?
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What function does the sarcolemma serve in muscle fibers?
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What is the composition of myofilaments within a muscle fiber?
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What is the function of mitochondria within muscle fibers?
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What role does calcium play in muscle contraction?
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What is the immediate consequence of the cross bridge coupling with the actin?
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How are fasciculi defined in the context of muscle anatomy?
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What structural components create the striations observed in skeletal muscles?
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How does ATP affect the myosin during muscle contraction?
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What happens during the recharging phase of muscle contraction?
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What structural change occurs during the muscle contraction cycle?
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Study Notes
Nervous System Overview
- Comprises two main parts: central nervous system (CNS) and peripheral nervous system (PNS).
- CNS includes the spinal cord and brain; PNS consists of nerves extending from the CNS, including cranial nerves and peripheral nerves.
Peripheral Nervous System Organization
- Peripheral nerves categorized into sensory, motor, and mixed types.
- Mixed nerves contain both sensory and motor neurons; they facilitate both input and output functions.
- PNS further divided into afferent (sensory information to CNS) and efferent (motor signals from CNS to body) neurons.
Neuron Structure
- Neurons vary significantly in shape and size, tailored to their function.
- Each neuron typically has a cell body with a nucleus, numerous dendrites, and a single long axon.
- The axon may branch and is covered by a myelin sheath, forming the nerve fiber.
Synaptic Communication
- Communication between neurons occurs at synapses involving neurotransmitters.
- The motor unit, the functional unit of muscle contraction, includes the alpha motor nerve and the muscle fibers it innervates.
- Most innervating neurons for skeletal muscle are classified as alpha motor neurons.
Muscle Contraction Mechanism
- Each muscle can contain multiple motor units, varying in the number of muscle fibers and motor units.
- The nervous system regulates muscle fiber activity through action potentials.
- Nerve endings form a neuromuscular junction (mio-neural junction) that closely adheres to muscle fiber membranes without penetrating them.
Action Potential and Resting Potential
- Electrical potential differences exist across membranes of all living cells, with varying ion concentrations inside (predominantly negative) and outside (predominantly positive).
- Resting potential ranges from -60 to -90 millivolts; typical resting potential for neurons is -70 millivolts.
- The capacity to respond to stimuli, known as irritability, allows cells to experience changes in membrane potential.
Depolarization Process
- Upon stimulation, membrane potential becomes more positive through depolarization.
- Continuous depolarization leads to transmission of electrochemical impulses along the cell membrane, facilitating communication in both nerve and muscle cells.
Muscle Structure and Function
- Muscle is enveloped by epimysium, a connective tissue that maintains separation between adjacent muscles.
- Perimysium further divides the muscle into smaller sections known as fasciculi.
- Each fasciculus comprises numerous muscle fibers, which are the fundamental units of the muscle structure.
- Muscle fibers contain rod-shaped myofibrils, extending the full length of the fiber.
- Myofibrils are encased in the sarcolemma and consist of a gelatinous substance called sarcoplasm, housing mitochondria and the sarcoplasmic reticulum.
- Mitochondria play a vital role in metabolic processes within muscle cells.
- Muscle fibers exhibit variation in length and diameter and contain multiple nuclei.
- Myofibrils house bundles of myofilaments—actin (thin filament) and myosin (thick filament)—integral for muscle contraction.
Sarcomere Organization
- A myofibril is structured into units called sarcomeres, which are delineated by Z-lines.
- Actin and myosin filaments create striations in skeletal muscles: light areas (I bands) and darker areas (A bands).
- A bands incorporate myosin filaments and regions of overlap with actin.
- H band is the central area of the sarcomere containing only myosin filaments, while I bands consist solely of actin anchored to Z lines.
- During contraction, the A band remains unchanged, while I bands shorten and H bands disappear as actin filaments slide inward.
Muscle Contraction Mechanism
- The contraction of muscles involves the sliding of actin past myosin, bringing Z lines closer together and shortening the muscle fiber.
- Myosin filaments have globular heads that form cross bridges with actin during muscle activation.
- The Sliding Filament Theory explains how actin and myosin filaments interact to create muscle contraction.
- Multiple cycles of cross-bridge formation are necessary for a strong contraction.
Cross Bridge Cycle
- ATP is crucial for muscle contraction; it binds to the myosin heads near the cross bridge.
- Calcium ions released from the sarcoplasmic reticulum allow myosin heads to attach to actin binding sites.
- The binding triggers the breakdown of ATP into ADP and energy, facilitating movement and flexion of the myosin head.
- Myosin pulls actin filaments toward each other, resulting in muscle contraction and Z lines moving closer together.
- The cycle of coupling, flexion, uncoupling, and recharging occurs rapidly, allowing continuous muscle contraction.
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Description
Test your knowledge on the nervous system, including its components and functions. This quiz covers the central and peripheral nervous systems, focusing on the anatomy of nerves and their organization. Ideal for students studying biology or human anatomy.
