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What is the first step in the cross-bridge cycle?
ATP binding to myosin allows for the detachment from actin.
True
What happens after myosin forms a strong bond with actin?
The power stroke occurs.
In the cross-bridge cycle, ATP is hydrolyzed, leading to myosin assuming the ______ state.
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What is formed when Pi is lost during the cross-bridge cycle?
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The myosin in a low energy state forms a strong bond with actin.
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What is the role of Ca2+ in the cross-bridge cycle?
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ADP and ______ are involved in the energy transfer during the power stroke.
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Match the components with their respective roles in the cross-bridge cycle:
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Which state allows myosin to perform the power stroke?
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What type of muscle is primarily involved in voluntary movements?
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The autonomic nervous system consists of only one branch.
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What is the role of calcium release from the sarcoplasmic reticulum in muscle contraction?
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The receptors that muscle fibers have for acetylcholine are known as __________ receptors.
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Match the following components with their functions:
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Which neurotransmitter is primarily released at the neuromuscular junction?
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Smooth muscle contractions are typically faster than skeletal muscle contractions.
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What is the main structural unit of skeletal muscle?
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The sympathetic nervous system primarily uses __________ as a neurotransmitter at the target organs.
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Which type of muscle is involuntary and found in the walls of internal organs?
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What is the state in which myosin forms a strong bond with actin during the cross-bridge cycle?
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ATP hydrolysis leads myosin to assume a low energy state.
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What molecule binds to myosin to allow its detachment from actin?
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During the power stroke, myosin loses _____, forming a strong bond with actin.
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Which of the following neurotransmitters is primarily associated with the sympathetic nervous system's response at target organs?
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Skeletal muscle is striated and under involuntary control.
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What role does calcium (Ca2+) play in muscle contraction?
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The __________ system is responsible for involuntary control of smooth muscle in internal organs.
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Match the following muscle types with their characteristics:
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Study Notes
Spinal Cord Anatomy
- The CNS (Central Nervous System) includes the spinal cord and brain
- Spinal cord contains nuclei within it, and ganglia outside it
- Sensory nuclei responsible for receiving sensory information
- Sensory nuclei include somatic and visceral sensory nuclei
- Motor nuclei responsible for delivering motor commands
- Motor nuclei include autonomic and somatic efferent nuclei
Autonomic Nervous System
- The ANS is responsible for unconscious bodily functions
- The ANS is composed of: Somatic pathways, Parasympathetic pathway, Sympathetic pathways, Adrenal Sympathetic pathway
Autonomic Nervous System: Pathways
- The autonomic nervous system involves two branches; parasympathetic and sympathetic
- The ANS uses a two neuron pathway: Pre and Post Ganglionic Neuron
- Parasympathetic preganglionic neurons use acetylcholine (ACh) as a neurotransmitter
- Sympathetic preganglionic neurons use acetylcholine (ACh) as a neurotransmitter
- Sympathetic postganglionic neurons use norepinephrine (NE) as a neurotransmitter
- Both parasympathetic and sympathetic pathways use nicotine receptors
- The sympathetic pathways use alpha, beta 1 and beta 2 adrenoreceptors
- The parasympathetic pathways use muscarinic receptors
Response to Stimulus
- Reflex response is a rapid, involuntary reaction to a stimulus
- Homeostatic response is a slower response to maintain internal balance
- Homeostatic response involves sensory input, integration, and output
- Sensory input for both reflexes and homeostasis is received by sensory neurons
- Integration occurs in the CNS, potentially including the hypothalamus, pons, and medulla
- The output can be somatic, autonomic, or endocrine
Thermoregulation
- Thermoregulation is the process of maintaining body temperature
- Thermoregulation uses both the somatic nervous system and the autonomic nervous system
- Thermoregulation involves the hypothalamus and skeletal muscle
- Thermoregulation uses ACh and NE as neurotransmitters
- Thermoregulation involves smooth muscle which helps regulate blood flow to the skin
Summary
- The hypothalamus is crucial for maintaining body homeostasis
- Spinal reflexes are quick, involuntary actions that do not require brain integration
- Homeostatic reflexes are slower and often involve the autonomic nervous system
- The two divisions of the ANS, sympathetic and parasympathetic, have distinct effects on target cells
- Both branches of the ANS control the same target cells but produce opposite effects using different receptors
Muscle Types
- Three major types of muscle exist: skeletal, cardiac, and smooth
- Skeletal muscle is attached to bones
- Cardiac muscle is found in the heart
- Smooth muscle is found in internal organs and vessels
- Skeletal muscle is striated and multinucleated, while cardiac and smooth muscle have single nuclei
Skeletal Muscle
- Skeletal muscle is responsible for movement
- Skeletal muscle produces heat due to ATP use
- Skeletal muscle is composed of muscle fibers
- Skeletal muscle is innervated by somatic motor neurons
Organization of Skeletal Muscle
- Skeletal muscle is composed of fascicles, bundles of muscle fibers
- Muscle fibers are composed of myofibrils
- Muscle fibers contain nuclei, mitochondria, sarcoplasmic reticulum, and T tubules
Ultrastructure of Muscle
- Myofibrils are composed of repeating sarcomeres
- Sarcomeres are the functional units of muscle contraction
- Sarcomeres contain thick filaments (myosin) and thin filaments (actin)
- Myosin heads bind to actin
- Titin acts as a spring to hold the structure of the sarcomere
- Myosin tails form the M line and actin anchors to the Z disk
- Troponin is a calcium binding protein on the actin filament
Muscle Contraction
- Muscle contraction is a complex process involving calcium signaling, ATP hydrolysis and cross-bridge cycling
- The contraction cycle occurs at the level of the myosin head.
The Neuromuscular Junction
- The neuromuscular junction is the synapse where a motor neuron innervates a muscle fiber
- At the neuromuscular junction, the axon terminal releases acetylcholine (ACh)
- ACh binds to nicotinic receptors on the motor end plate of the muscle fiber
- Stimulation of the motor end plate initiates an action potential in the muscle fiber
- The action potential spreads across the sarcolemma and into the T tubules
Excitation-Contraction Coupling
- Excitation-contraction coupling is the process that converts an electrical signal (action potential) into a calcium signal
- The electrical signal triggers calcium release from the sarcoplasmic reticulum
- Binding of Ca2+ to troponin relieves the inhibition of actin
- Myosin heads can then bind to actin and initiate muscle contraction
- Muscle relaxation occurs when calcium is pumped back into the sarcoplasmic reticulum
The Calcium Signal
- Relaxation occurs when calcium is removed allowing the tropomyosin to block the actin binding site
- ATP is required for both the calcium pump and myosin detatchment
Spinal Cord Anatomy
- Ganglia are located outside the Central Nervous System (CNS)
- Nuclei are located within the CNS
- The dorsal root ganglion contains sensory neurons and is located outside the spinal cord
- The dorsal horn contains sensory nuclei
- The lateral horn contains autonomic efferent nuclei
- The ventral horn contains somatic motor nuclei
- The ventral root contains motor neurons and is located outside the spinal cord
Nervous System Pathways
- Somatic Motor Pathway: CNS to skeletal muscle, uses acetylcholine (ACh) as neurotransmitter, receptor is nicotinic on skeletal muscle
- Parasympathetic Pathway: CNS to autonomic effectors, uses ACh at both pre-ganglionic and post-ganglionic synapses, pre-ganglionic receptor is nicotinic, post-ganglionic receptor is muscarinic
- Sympathetic Pathways: CNS to autonomic effectors, uses ACh pre-ganglionically, uses norepinephrine (NE) post-ganglionically, pre-ganglionic receptor is nicotinic, post-ganglionic receptor is adrenergic
- Adrenal Sympathetic Pathway: CNS to adrenal medulla primarily, uses ACh pre-ganglionically, uses NE and epinephrine (E) from adrenal medulla, pre-ganglionic receptor is nicotinic, post-ganglionic receptor is adrenergic
- Autonomic effectors include smooth muscle, cardiac muscle, some endocrine and exocrine glands, and some adipose tissue
Response to Stimuli
- Reflex response: Sensory input triggers integration and action
- Homeostatic response: Sensory input triggers hypothalamic receptors and integration processing in the pons, medulla, and hypothalamus, resulting in autonomic, somatic motor, and endocrine responses
Thermoregulation
- Afferent sensory neurons detect temperature changes and send signals to the hypothalamus.
- The hypothalamus integrates information and sends signals through descending tracts to somatic motor neurons and efferent autonomic neurons.
- Somatic motor neurons activate skeletal muscle for shivering (generating heat).
- Autonomic neurons activate smooth muscle in blood vessels, either constricting or dilating to regulate heat loss.
The Hypothalamus
- The hypothalamus is essential for maintaining homeostasis.
Reflexes
- Spinal reflexes are fast, involuntary actions that do not require direct integration by the brain.
- Homeostatic reflexes are slower and often involve the autonomic nervous system.
The Autonomic Nervous System
- The autonomic nervous system has two branches: parasympathetic and sympathetic.
- Within the CNS, the control of these branches is spatially segregated.
- Both branches affect the same target cells but produce antagonistic effects by interacting with different receptors.
Skeletal Muscle
- Skeletal muscle is attached to the skeleton and is responsible for movement.
- It is striated, multinucleated, and exhibits the fastest contraction speed.
- It is controlled by the somatic motor nervous system.
Fundamental Functions of Muscle
- Muscle converts neural information into mechanical energy (force and displacement).
- Muscle contraction produces heat as a byproduct.
Organization of Skeletal Muscle
- Skeletal muscle consists of muscle fibers bundled into fascicles, surrounded by connective tissue.
Ultrastructure of Muscle
- Muscle fibers contain myofibrils, which are composed of sarcomeres.
- Sarcomeres are the basic contractile units of muscle.
- Sarcomeres contain thick filaments (myosin) and thin filaments (actin).
Contraction Cycle
- The contraction cycle involves a series of steps that require ATP.
- Myosin heads bind to actin (cross-bridge formation) and perform a power stroke, pulling the thin filaments toward the center of the sarcomere, causing muscle shortening.
- Myosin detaches from actin when ATP binds to myosin, allowing the cycle to repeat.
Neuromuscular Junction
- The neuromuscular junction is a synapse between a motor neuron and a muscle fiber.
- The axon terminal of the motor neuron releases acetylcholine (ACh), which binds to nicotinic receptors on the motor end plate of the muscle fiber.
- This binding triggers an action potential in the muscle fiber, leading to muscle contraction.
Excitation-Contraction Coupling
- Excitation-contraction coupling refers to the conversion of an electrical signal (action potential) in the sarcolemma (muscle fiber membrane) into a calcium signal in the cytoplasm.
- This occurs when the action potential triggers the release of calcium from the sarcoplasmic reticulum (SR).
- The release of calcium initiates the contraction cycle by allowing myosin to bind to actin.
Calcium Signal
- The calcium signal is critical for muscle contraction.
- Calcium release from the SR triggers muscle contraction, while the removal of calcium from the cytoplasm allows the muscle to relax.
Muscle Relaxation
- Muscle relaxation occurs when calcium is removed from the cytoplasm, which is achieved through the action of calcium pumps in the SR membrane.
- The removal of calcium allows the muscle to relax and return to its resting length.
Three Types of Muscle
- Skeletal muscle: Attached to skeleton, striated, multinucleated, fastest contraction speed
- Cardiac muscle: Found in heart, striated, uninucleated, intermediate contraction speed
- Smooth muscle: Located in internal organs and vessels, smooth, uninucleated, and slowest contraction speed
ATP in Muscle Contraction
- ATP is essential for muscle contraction.
- It is required for the following processes:
- Myosin detachment from actin, breaking the cross-bridge
- The power stroke of myosin
- Calcium pumps to move calcium back into the sarcoplasmic reticulum, allowing for muscle relaxation.
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Description
This quiz covers the anatomy of the spinal cord and the autonomic nervous system (ANS). Learn about the structure and functions of sensory and motor nuclei, as well as the pathways involved in the ANS, including the roles of sympathetic and parasympathetic branches. Test your knowledge on the central nervous system and its components.
