Nervous System Organization and Function (3A) - MCAT Biological and Biochemical Foundations of Living Systems
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Which receptor type binds ACh at the skeletal muscle neuromuscular junction?
Which receptor type binds ACh at the skeletal muscle neuromuscular junction?
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Nicotinic acetylcholine receptor (nAChR). This ionotropic receptor triggers muscle contraction by allowing cation influx upon binding at the motor end plate.
Nicotinic acetylcholine receptor (nAChR). This ionotropic receptor triggers muscle contraction by allowing cation influx upon binding at the motor end plate.
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What is the effect of opening ligand-gated $Cl^-$ channels on membrane potential?
What is the effect of opening ligand-gated $Cl^-$ channels on membrane potential?
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Hyperpolarization (inhibitory postsynaptic potential, IPSP). Chloride influx shifts the membrane potential more negative, reducing the likelihood of action potential generation.
Hyperpolarization (inhibitory postsynaptic potential, IPSP). Chloride influx shifts the membrane potential more negative, reducing the likelihood of action potential generation.
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What is the primary immune-like phagocytic cell type in the CNS?
What is the primary immune-like phagocytic cell type in the CNS?
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Microglia. These resident macrophages of the CNS engulf debris and pathogens to protect neural tissue.
Microglia. These resident macrophages of the CNS engulf debris and pathogens to protect neural tissue.
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What is the primary role of astrocytes in the CNS?
What is the primary role of astrocytes in the CNS?
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Support neurons and help maintain the blood-brain barrier. Astrocytes provide metabolic and structural support to neurons while regulating the extracellular environment and barrier integrity.
Support neurons and help maintain the blood-brain barrier. Astrocytes provide metabolic and structural support to neurons while regulating the extracellular environment and barrier integrity.
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Which glial cells myelinate axons in the peripheral nervous system?
Which glial cells myelinate axons in the peripheral nervous system?
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Schwann cells. These PNS glial cells individually myelinate axons, aiding in nerve regeneration and signal conduction.
Schwann cells. These PNS glial cells individually myelinate axons, aiding in nerve regeneration and signal conduction.
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Which glial cells myelinate axons in the central nervous system?
Which glial cells myelinate axons in the central nervous system?
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Oligodendrocytes. These CNS glial cells wrap multiple axons to form myelin sheaths, supporting rapid neural signaling.
Oligodendrocytes. These CNS glial cells wrap multiple axons to form myelin sheaths, supporting rapid neural signaling.
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What is the functional role of myelin in axons?
What is the functional role of myelin in axons?
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Increases conduction velocity by insulating the axon. Myelin sheaths prevent ion leakage and enable faster signal propagation via saltatory conduction along axons.
Increases conduction velocity by insulating the axon. Myelin sheaths prevent ion leakage and enable faster signal propagation via saltatory conduction along axons.
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Which receptor class is activated by NE in most sympathetic target organs?
Which receptor class is activated by NE in most sympathetic target organs?
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Adrenergic receptors (alpha and beta). These G-protein coupled receptors mediate sympathetic responses by binding catecholamines like NE in effector organs.
Adrenergic receptors (alpha and beta). These G-protein coupled receptors mediate sympathetic responses by binding catecholamines like NE in effector organs.
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Which ANS division is associated with “fight-or-flight” physiology?
Which ANS division is associated with “fight-or-flight” physiology?
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Sympathetic nervous system. This division mobilizes energy resources and prepares the body for emergency responses through widespread activation.
Sympathetic nervous system. This division mobilizes energy resources and prepares the body for emergency responses through widespread activation.
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What is the correct ion movement that causes depolarization in a neuron?
What is the correct ion movement that causes depolarization in a neuron?
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Voltage-gated $Na^+$ channels open; $Na^+$ influx depolarizes. Threshold depolarization triggers sodium channel opening, allowing rapid sodium entry to reverse membrane potential.
Voltage-gated $Na^+$ channels open; $Na^+$ influx depolarizes. Threshold depolarization triggers sodium channel opening, allowing rapid sodium entry to reverse membrane potential.
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What ion movement is primarily responsible for repolarization of the action potential?
What ion movement is primarily responsible for repolarization of the action potential?
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Voltage-gated $K^+$ channels open; $K^+$ efflux repolarizes. Following peak depolarization, potassium channels open to restore the negative membrane potential through potassium outflow.
Voltage-gated $K^+$ channels open; $K^+$ efflux repolarizes. Following peak depolarization, potassium channels open to restore the negative membrane potential through potassium outflow.
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Identify the direction of neurotransmitter release across a chemical synapse.
Identify the direction of neurotransmitter release across a chemical synapse.
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From presynaptic axon terminal to postsynaptic membrane. Chemical synapses transmit signals unidirectionally via neurotransmitter diffusion across the synaptic cleft to receptor sites.
From presynaptic axon terminal to postsynaptic membrane. Chemical synapses transmit signals unidirectionally via neurotransmitter diffusion across the synaptic cleft to receptor sites.
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Which brain region is the primary homeostatic control center for autonomic and endocrine output?
Which brain region is the primary homeostatic control center for autonomic and endocrine output?
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Hypothalamus. This diencephalic structure integrates sensory inputs and regulates vital functions through neural and hormonal mechanisms.
Hypothalamus. This diencephalic structure integrates sensory inputs and regulates vital functions through neural and hormonal mechanisms.
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What are the two major anatomical divisions of the nervous system?
What are the two major anatomical divisions of the nervous system?
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Central nervous system and peripheral nervous system. The nervous system is anatomically divided into central components for processing and peripheral for communication with the body.
Central nervous system and peripheral nervous system. The nervous system is anatomically divided into central components for processing and peripheral for communication with the body.
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What structures make up the central nervous system (CNS)?
What structures make up the central nervous system (CNS)?
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Brain and spinal cord. The CNS integrates sensory information and coordinates responses, consisting of protected neural tissues.
Brain and spinal cord. The CNS integrates sensory information and coordinates responses, consisting of protected neural tissues.
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What structures make up the peripheral nervous system (PNS)?
What structures make up the peripheral nervous system (PNS)?
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Cranial nerves, spinal nerves, and ganglia. The PNS connects the CNS to the rest of the body, facilitating sensory input and motor output through neural bundles and clusters.
Cranial nerves, spinal nerves, and ganglia. The PNS connects the CNS to the rest of the body, facilitating sensory input and motor output through neural bundles and clusters.
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What is the functional difference between afferent and efferent neurons?
What is the functional difference between afferent and efferent neurons?
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Afferent: sensory to CNS; efferent: motor from CNS. Afferent neurons transmit signals toward the CNS for integration, while efferent carry commands away to effectors.
Afferent: sensory to CNS; efferent: motor from CNS. Afferent neurons transmit signals toward the CNS for integration, while efferent carry commands away to effectors.
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What are the two main functional divisions of the efferent PNS?
What are the two main functional divisions of the efferent PNS?
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Somatic nervous system and autonomic nervous system. Efferent PNS divisions separate voluntary control from involuntary regulation of internal functions.
Somatic nervous system and autonomic nervous system. Efferent PNS divisions separate voluntary control from involuntary regulation of internal functions.
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What is the key difference between somatic and autonomic motor pathways?
What is the key difference between somatic and autonomic motor pathways?
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Somatic: skeletal muscle; autonomic: smooth/cardiac/glands. Somatic pathways enable conscious control of movement, whereas autonomic regulate involuntary visceral functions.
Somatic: skeletal muscle; autonomic: smooth/cardiac/glands. Somatic pathways enable conscious control of movement, whereas autonomic regulate involuntary visceral functions.
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What are the two divisions of the autonomic nervous system (ANS)?
What are the two divisions of the autonomic nervous system (ANS)?
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Sympathetic and parasympathetic. The ANS is subdivided into antagonistic branches that balance physiological responses to stress and relaxation.
Sympathetic and parasympathetic. The ANS is subdivided into antagonistic branches that balance physiological responses to stress and relaxation.
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Which ANS division is associated with “rest-and-digest” physiology?
Which ANS division is associated with “rest-and-digest” physiology?
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Parasympathetic nervous system. This division conserves energy and promotes maintenance activities like digestion during non-stressful states.
Parasympathetic nervous system. This division conserves energy and promotes maintenance activities like digestion during non-stressful states.
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What is the neurotransmitter released by all preganglionic ANS neurons?
What is the neurotransmitter released by all preganglionic ANS neurons?
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Acetylcholine (ACh). Preganglionic neurons in both ANS divisions use this neurotransmitter to synapse with postganglionic neurons at ganglia.
Acetylcholine (ACh). Preganglionic neurons in both ANS divisions use this neurotransmitter to synapse with postganglionic neurons at ganglia.
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What neurotransmitter is typically released by sympathetic postganglionic neurons?
What neurotransmitter is typically released by sympathetic postganglionic neurons?
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Norepinephrine (NE). Sympathetic postganglionic fibers primarily release this catecholamine to elicit fight-or-flight effects on target tissues.
Norepinephrine (NE). Sympathetic postganglionic fibers primarily release this catecholamine to elicit fight-or-flight effects on target tissues.
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What neurotransmitter is typically released by parasympathetic postganglionic neurons?
What neurotransmitter is typically released by parasympathetic postganglionic neurons?
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Acetylcholine (ACh). Parasympathetic postganglionic neurons release this neurotransmitter to mediate rest-and-digest responses in visceral organs.
Acetylcholine (ACh). Parasympathetic postganglionic neurons release this neurotransmitter to mediate rest-and-digest responses in visceral organs.
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