Nervous System Revision Sheet

1. 📌 Essentials

• Neurons are the fundamental units, comprising soma, dendrites, axon, and synapses.
• The CNS includes the brain (cerebrum, cerebellum, brainstem) and spinal cord.
• The PNS consists of cranial nerves (12 pairs) and spinal nerves (31 pairs).
• Major brain regions cerebral cortex (motor, sensory, association), diencephalon, brainstem cerebellum.
• Spinal cord gray matter: dorsal horn (sensory), ventral horn (motor), lateral horn (autonomic).
• Ascending pathways (sensory): dorsal columns, spinothalamic tract.
• Descending pathways (motor): corticospinal tract.
• Cranial nerves I-XII have specific sensory, motor, or mixed functions.
• Reflexes involve sensory receptor → afferent neuron → CNS → efferent neuron → effector.
• Typical neuron resting potential: ~ -70 mV; threshold: ~ -55 mV.
• Blood supply: carotid and vertebral arteries.

2. 🧩 Key Structures & Components