MCAT Biological and Biochemical Foundations of Living Systems Flashcards: 3a Nervous System Organization Function

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This deck focuses on 3a Nervous System Organization Function, giving you a quick way to review the definitions, rules, and examples that matter most for MCAT Biological and Biochemical Foundations of Living Systems.

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Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: Which glial cells myelinate axons in the peripheral nervous system?

Answer: Schwann cells. These PNS glial cells individually myelinate axons, aiding in nerve regeneration and signal conduction.

Flashcard 2: What is the functional difference between afferent and efferent neurons?

Answer: Afferent: sensory to CNS; efferent: motor from CNS. Afferent neurons transmit signals toward the CNS for integration, while efferent carry commands away to effectors.

Flashcard 3: What are the two major anatomical divisions of the nervous system?

Answer: 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.

Flashcard 4: Which ANS division is associated with "fight-or-flight" physiology?

Answer: Sympathetic nervous system. This division mobilizes energy resources and prepares the body for emergency responses through widespread activation.

Flashcard 5: What are the two divisions of the autonomic nervous system (ANS)?

Answer: Sympathetic and parasympathetic. The ANS is subdivided into antagonistic branches that balance physiological responses to stress and relaxation.

Flashcard 6: What is the neurotransmitter released by all preganglionic ANS neurons?

Answer: Acetylcholine (ACh). Preganglionic neurons in both ANS divisions use this neurotransmitter to synapse with postganglionic neurons at ganglia.

Flashcard 7: What structures make up the central nervous system (CNS)?

Answer: Brain and spinal cord. The CNS integrates sensory information and coordinates responses, consisting of protected neural tissues.

Flashcard 8: Which ANS division is associated with "rest-and-digest" physiology?

Answer: Parasympathetic nervous system. This division conserves energy and promotes maintenance activities like digestion during non-stressful states.

Flashcard 9: What is the primary immune-like phagocytic cell type in the CNS?

Answer: Microglia. These resident macrophages of the CNS engulf debris and pathogens to protect neural tissue.

Flashcard 10: What is the correct ion movement that causes depolarization in a neuron?

Answer: Voltage-gated $Na^+$ channels open; $Na^+$ influx depolarizes. Threshold depolarization triggers sodium channel opening, allowing rapid sodium entry to reverse membrane potential.

Flashcard 11: What is the effect of opening ligand-gated $Cl^-$ channels on membrane potential?

Answer: Hyperpolarization (inhibitory postsynaptic potential, IPSP). Chloride influx shifts the membrane potential more negative, reducing the likelihood of action potential generation.

Flashcard 12: Which brain region is the primary homeostatic control center for autonomic and endocrine output?

Answer: Hypothalamus. This diencephalic structure integrates sensory inputs and regulates vital functions through neural and hormonal mechanisms.

Flashcard 13: Identify the direction of neurotransmitter release across a chemical synapse.

Answer: From presynaptic axon terminal to postsynaptic membrane. Chemical synapses transmit signals unidirectionally via neurotransmitter diffusion across the synaptic cleft to receptor sites.

Flashcard 14: What structures make up the peripheral nervous system (PNS)?

Answer: 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.

Flashcard 15: Which glial cells myelinate axons in the central nervous system?

Answer: Oligodendrocytes. These CNS glial cells wrap multiple axons to form myelin sheaths, supporting rapid neural signaling.

Flashcard 16: Which receptor class is activated by NE in most sympathetic target organs?

Answer: Adrenergic receptors (alpha and beta). These G-protein coupled receptors mediate sympathetic responses by binding catecholamines like NE in effector organs.

Flashcard 17: What are the two main functional divisions of the efferent PNS?

Answer: Somatic nervous system and autonomic nervous system. Efferent PNS divisions separate voluntary control from involuntary regulation of internal functions.

Flashcard 18: What neurotransmitter is typically released by sympathetic postganglionic neurons?

Answer: Norepinephrine (NE). Sympathetic postganglionic fibers primarily release this catecholamine to elicit fight-or-flight effects on target tissues.

Flashcard 19: What is the primary role of astrocytes in the CNS?

Answer: 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.

Flashcard 20: Which receptor type binds ACh at the skeletal muscle neuromuscular junction?

Answer: Nicotinic acetylcholine receptor (nAChR). This ionotropic receptor triggers muscle contraction by allowing cation influx upon binding at the motor end plate.

Flashcard 21: What ion movement is primarily responsible for repolarization of the action potential?

Answer: Voltage-gated $K^+$ channels open; $K^+$ efflux repolarizes. Following peak depolarization, potassium channels open to restore the negative membrane potential through potassium outflow.

Flashcard 22: What is the key difference between somatic and autonomic motor pathways?

Answer: Somatic: skeletal muscle; autonomic: smooth/cardiac/glands. Somatic pathways enable conscious control of movement, whereas autonomic regulate involuntary visceral functions.

Flashcard 23: What neurotransmitter is typically released by parasympathetic postganglionic neurons?

Answer: Acetylcholine (ACh). Parasympathetic postganglionic neurons release this neurotransmitter to mediate rest-and-digest responses in visceral organs.

Flashcard 24: What is the functional role of myelin in axons?

Answer: Increases conduction velocity by insulating the axon. Myelin sheaths prevent ion leakage and enable faster signal propagation via saltatory conduction along axons.