What are the main pathways of the corticospinal tract?
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| 1 | What are the main pathways of the corticospinal tract? |
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Study the pathways of major nerves and their innervation patterns across the body.
The corticospinal tract originates in the motor cortex, descends through the internal capsule, cerebral peduncles, pons, medulla (where fibers decussate at the pyramidal decussation), and continues down the spinal cord as the lateral corticospinal tract to innervate limb muscles. The anterior corticospinal tract also arises from the cortex but decussates at the spinal cord level to innervate axial muscles. |
| Think 'pyramids' for decussation location |
| 2 | Which nerve roots contribute to the brachial plexus? | The brachial plexus is formed by the anterior rami of spinal nerves C5 through T1. | C5-T1 are the 'nerve roots' for the upper limb |
| 3 | What is the primary pathway of the dorsal column-medial lemniscal system? | Sensory fibers from the dorsal columns (fasciculus cuneatus and fasciculus gracilis) ascend ipsilaterally to the medulla, synapse there, then cross as the internal arcuate fibers, and ascend contralaterally as the medial lemniscus to the thalamus, ultimately projecting to the somatosensory cortex. | Remember 'medial lemniscus' crosses at the medulla |
| 4 | Which cranial nerve is primarily responsible for facial sensation and where does its sensory pathway project? | The trigeminal nerve (cranial nerve V) transmits facial sensation. Its sensory fibers project to the trigeminal (semilunar) ganglion, then to the principal sensory nucleus in the pons, and finally to the ventral posteromedial nucleus of the thalamus before reaching the somatosensory cortex. | Think 'V' for 'V' in trigeminal and ventral posteromedial nucleus |
| 5 | Describe the pathway of the spinothalamic tract. | The spinothalamic tract carries pain and temperature sensation. It originates from dorsal horn neurons, fibers cross immediately through the ventral white commissure, ascend contralaterally in the lateral funiculus as the lateral spinothalamic tract to reach the thalamus, then project to the somatosensory cortex. | Crossing occurs early in the spinal cord |
| 6 | Which nerve roots form the lumbar plexus, and what are its major branches? | The lumbar plexus is formed by anterior rami of L1-L4. Major branches include the femoral nerve, obturator nerve, and lateral femoral cutaneous nerve. | L1-L4 for lumbar plexus; 'FOL' for Femoral, Obturator, Lateral femoral cutaneous |
| 7 | Where does the sympathetic innervation of the heart originate? | Sympathetic innervation of the heart originates from preganglionic fibers in the intermediolateral cell columns of T1-T4 spinal cord segments, which synapse in cervical and thoracic sympathetic chain ganglia before reaching the cardiac plexus. | T1-T4 are the key segments for cardiac sympathetic supply |
| 8 | What are the main pathways of the dorsal scapular nerve and its innervation pattern? | The dorsal scapular nerve arises from C5 ventral ramus, passes through the middle scalene, and innervates the rhomboid major, rhomboid minor, and levator scapulae muscles. | C5 is the key root for dorsal scapular nerve |
| 9 | Which nerves are involved in the innervation of the anterior thigh muscles? | The femoral nerve (L2-L4) innervates most anterior thigh muscles, including the quadriceps. The obturator nerve (L2-L4) supplies the medial thigh muscles like the adductors. | Femoral for quadriceps; Obturator for adductors |
| 10 | What is the pathway of the spinal accessory nerve (cranial nerve XI)? | The spinal accessory nerve originates from the spinal cord (C1-C5), ascends through the foramen magnum into the skull, then exits via the jugular foramen to innervate the sternocleidomastoid and trapezius muscles. | Don't confuse with vagus nerve; 'Accessory' helps 'access' muscles |
| 11 | Which nerve supplies the intrinsic muscles of the hand, and what is its pathway? | The ulnar nerve supplies many intrinsic hand muscles. It originates from the medial cord of the brachial plexus (C8-T1), travels down the medial arm, passes posterior to the medial epicondyle at the elbow, and enters the hand via Guyon's canal. | Ulnar for 'ulnar' side muscles of the hand |
| 12 | What is the course of the sciatic nerve, and which muscles does it innervate? | The sciatic nerve arises from L4-S3 nerve roots, exits the pelvis through the greater sciatic foramen below the piriformis, runs posteriorly down the thigh, and bifurcates into tibial and common fibular nerves, innervating posterior thigh muscles and all muscles below the knee. | Longest nerve in the body |
| 13 | Which nerve provides motor innervation to the diaphragm? | The phrenic nerve, originating primarily from C3-C5 nerve roots, supplies motor innervation to the diaphragm. | C3, C4, C5 keep the diaphragm alive |
| 14 | Where does the lumbosacral trunk run, and what does it innervate? | The lumbosacral trunk is formed by L4-L5 nerve roots, runs over the pelvic brim, and contributes to the sacral plexus, innervating parts of the pelvis and lower limb via the sacral plexus. | L4-L5 connect lumbar and sacral plexuses |
| 15 | What is the pathway of the olfactory nerve (cranial nerve I)? | The olfactory nerve fibers originate in the olfactory epithelium, pass through the cribriform plate of the ethmoid bone, and synapse in the olfactory bulb, with signals then relayed to the olfactory cortex. | Special sensory nerve for smell |
| 16 | Which nerves are involved in the somatic motor innervation of the muscles of mastication? | The mandibular nerve (V3 branch of trigeminal nerve) provides motor innervation to the muscles of mastication: masseter, temporalis, medial and lateral pterygoids. | V3 is both sensory and motor |
| 17 | What is the pathway of the vagus nerve (cranial nerve X) in the thorax? | The vagus nerve exits the skull via the jugular foramen, descends through the neck within the carotid sheath, and gives off branches to thoracic viscera, including the cardiac, pulmonary, and esophageal plexuses, before reaching the abdomen. | Vagus = wanderer of the thorax and abdomen |
| 18 | Which nerve is responsible for the sensation of the anterior two-thirds of the tongue? | The mandibular division of the trigeminal nerve (V3) provides general sensation, while taste is carried by the chorda tympani branch of the facial nerve (cranial nerve VII). | Sensation: V3; Taste: Facial nerve |
| 19 | How does the dorsal scapular nerve differ from the suprascapular nerve in terms of pathway and innervation? | The dorsal scapular nerve (C5) innervates rhomboids and levator scapulae, while the suprascapular nerve (C5-C6) passes through the suprascapular notch to innervate the supraspinatus and infraspinatus muscles. | Dorsal scapular for 'scapula' muscles; Suprascapular for 'rotator cuff' muscles |
| 20 | Which nerves contribute to the formation of the sacral plexus? | The sacral plexus is formed primarily by anterior rami of L4-S4 nerve roots. | L4-S4 make up the sacral plexus |
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