Description:In adults, the spinal cord ends at the lower border of the L1 vertebra. This is because the spinal cord does not grow as fast as the vertebral column during childhood. In newborns, the spinal cord may extend up to the L3 vertebra. This is because the vertebral column is not fully developed at birth. The cauda equina is a collection of nerves that extend from the lumbar and sacral vertebrae to the coccyx. It is named after its resemblance to a horse's tail.

Description:The extension of the spinal cord takes place from the occipital bone of the skull.

Description:The cervical plexus is a network of nerves that innervates and controls the head and neck region. It is formed by the anterior rami of the upper four cervical nerves (C1-C4). The cervical plexus provides motor innervation to the muscles of the neck and shoulder, and sensory innervation to the skin of the head, neck, and chest. The brachial plexus is a network of nerves that innervates and controls the upper limb. It is formed by the anterior rami of the lower four cervical nerves (C5-C8) and the first thoracic nerve (T1). The brachial plexus provides motor innervation to the muscles of the upper limb, and sensory innervation to the skin of the upper limb. The lumbar plexus is a network of nerves that innervates and controls the lower limb. It is formed by the anterior rami of the lumbar nerves (L1-L4). The lumbar plexus provides motor innervation to the muscles of the lower limb, and sensory innervation to the skin of the lower limb. The thoracic plexus is a network of nerves that innervates and controls the chest and abdomen. It is formed by the anterior rami of the thoracic nerves (T1-T12). The thoracic plexus provides motor innervation to the muscles of the chest and abdomen, and sensory innervation to the skin of the chest and abdomen.

Description:The bundle of nerve fibers present below the spinal cord is referred to as the cauda equina.

Description:The bundles of fibers or the tract present on the white matter of the spinal cord are called fasciculi. Fasciculi are bundles of axons that are grouped together based on their function. There are three main types of fasciculi in the spinal cord: ascending, descending, and association fasciculi. Ascending fasciculi carry sensory information from the body to the brain. Descending fasciculi carry motor information from the brain to the body. Association fasciculi connect different parts of the spinal cord. The conus medullaris is the cone-shaped lower end of the spinal cord. The cauda equina is a collection of nerves that extend from the lumbar and sacral vertebrae to the coccyx. Dermatomes are areas of skin that are innervated by a single spinal nerve.

Description:In human beings, the opening of the spinal cord begins at the foramen magnum. Therefore, the correct answer is option a.

Description:Memory and comprehension." The spinal cord is primarily involved in carrying out reflexes, transmitting sensory and motor information, and transporting messages to and from the brain. Memory and comprehension are functions primarily associated with the brain rather than the spinal cord. Therefore, the correct answer is option c.

Description:The cervical enlargement is a region of the spinal cord that is enlarged to accommodate the nerves that innervate the arms. The cervical enlargement is located between the third and fifth cervical vertebrae. The nerves from the arm enter and exit the spinal cord through the cervical enlargement. The lumbar enlargement is a region of the spinal cord that is enlarged to accommodate the nerves that innervate the legs. The lumbar enlargement is located between the twelfth thoracic and third lumbar vertebrae. The nerves from the leg enter and exit the spinal cord through the lumbar enlargement. The central canal is the hollow center of the spinal cord. It contains cerebrospinal fluid, which helps to protect and nourish the spinal cord. The cauda equina is a collection of nerves that extend from the lumbar and sacral vertebrae to the coccyx. It is named after its resemblance to a horse's tail.

Description:The nerves from the leg enter and exit through the "b. Lumbosacral enlargement" of the spinal cord. The lumbosacral enlargement refers to the lower part of the spinal cord where the nerves that innervate the lower limbs (legs) enter and exit. Therefore, option b is the correct answer.

Description:The cerebrospinal fluid-filled ependymal space present on the spinal cord is known as the "c. Central canal." The central canal is a small hollow channel that runs along the length of the spinal cord and is filled with cerebrospinal fluid. Therefore, option c is the correct answer.

Description:The number of pairs of cranial nerves is "d. 12." There are 12 pairs of cranial nerves that emerge directly from the brain and are involved in various sensory, motor, and autonomic functions of the head and neck region. Therefore, option d is the correct answer.

Description:The 10th cranial nerve is the "b. Vagus" nerve. The vagus nerve is also known as cranial nerve X and is responsible for controlling various organs and functions in the body, including the heart, lungs, and digestive system. Therefore, option b is the correct answer.

Description:The largest cranial nerve is the "b. Trigeminal nerve." The trigeminal nerve is the fifth cranial nerve and is the largest of all the cranial nerves. It is responsible for sensory information from the face, as well as motor control of the muscles involved in chewing. Therefore, option b is the correct answer.

Description:The 5th cranial nerve is the trigeminal nerve. It is the largest of the twelve cranial nerves. The trigeminal nerve is responsible for providing sensory innervation to the face and motor innervation to the muscles of mastication. The trigeminal nerve has three branches: the ophthalmic nerve (V1), the maxillary nerve (V2), and the mandibular nerve (V3). The trochlear nerve is the 4th cranial nerve. It is responsible for innervating the superior oblique muscle of the eye. The abducens nerve is the 6th cranial nerve. It is responsible for innervating the lateral rectus muscle of the eye. The facial nerve is the 7th cranial nerve. It is responsible for innervating the muscles of facial expression, taste, and tears.

Description:The abducens nerve (CN VI) is the first cranial nerve to be affected by increased intracranial pressure. This is because the abducens nerve is the most superficial of the cranial nerves, and it is therefore more vulnerable to compression by increased intracranial pressure. The other cranial nerves are also affected by increased intracranial pressure, but they are not affected as early as the abducens nerve. The oculomotor nerve (CN III) is usually affected next, followed by the trochlear nerve (CN IV). The trigeminal nerve (CN V), facial nerve (CN VII), vestibulocochlear nerve (CN VIII), glossopharyngeal nerve (CN IX), vagus nerve (CN X), accessory nerve (CN XI), and hypoglossal nerve (CN XII) are affected later. The symptoms of increased intracranial pressure can vary depending on the severity of the pressure. Mild increases in intracranial pressure may not cause any symptoms. However, as the pressure increases, the patient may experience headaches, nausea, vomiting, double vision, and vision loss. In severe cases, increased intracranial pressure can lead to coma and death.

Description:Pupillary constriction is controlled by the "b. III" cranial nerve, also known as the oculomotor nerve. The oculomotor nerve innervates the muscles that control the size of the pupil (pupillary constriction) and other movements of the eye. Therefore, option b is the correct answer.

Description:• Largest cranial nerve: Trigeminal • Smallest cranial nerve: Trochlear • Short cranial nerve: Olfactory

Description:The vagus nerve (X nerve) mediates important homeostatic reflexes such as heart rate, blood pressure, and respiration.

Description:The sciatic nerve is the largest nerve in the human body. It is a mixed nerve, meaning that it contains both motor and sensory fibers. The sciatic nerve originates in the lower back and travels down the back of each leg to the foot. It is responsible for providing motor innervation to the muscles of the back of the thigh and leg, and sensory innervation to the skin of the leg and foot. The femoral nerve is the second largest nerve in the human body. It is a motor nerve that provides innervation to the muscles of the thigh. The obturator nerve is a motor nerve that provides innervation to the muscles of the inner thigh. The pudendal nerve is a mixed nerve that provides innervation to the muscles of the pelvic floor and the genitals.

Description:The correct answer is "c. Myelencephalon." The medulla oblongata is a part of the brainstem, and it is specifically derived from the embryonic myelencephalon. Therefore, option c is the correct answer. The prosencephalon, femoral nerve, and metencephalon refer to different structures or nerves and are not alternate names for the medulla oblongata.

Description:The posterior inferior cerebellar artery is not part of the circle of Willis. The circle of Willis is a network of arteries at the base of the brain that provides a backup supply of blood to the brain in case one of the major arteries is blocked. The circle of Willis is formed by the following arteries: The anterior cerebral artery (ACA) The posterior cerebral artery (PCA) The internal carotid artery (ICA) The anterior communicating artery (ACoA) The posterior communicating artery (PCoA) The posterior inferior cerebellar artery (PICA) is a branch of the vertebral artery that supplies blood to the brainstem and cerebellum. It is not part of the circle of Willis.

Description:The middle meningeal artery is a branch of the "b. Maxillary artery." The maxillary artery is one of the main branches of the external carotid artery and gives rise to several branches, including the middle meningeal artery. Therefore, option b is the correct answer. The middle cerebral artery, superficial temporal artery, and vertebral artery are not directly associated with the origin of the middle meningeal artery.

Description:The major peripheral nerve of upper arm is musculocutaneous which innervates the anterior compartment muscle (brachialis, bicep brachii and coracobrachialis) of upper arm and give rise to lateral cutaneous nerve of forearm which innervate lateral surfaces of the forearm. But the muscles of forearm (Flexor carpi ulnaris, Flexor carpi radialis, pronator teres, etc.) innervated by radial nerve, ulnar nerve and median nerve, PS: The question is about muscle innervations (not cutaneous innervations). Cutaneous innervations of forearm is supplied by musculocutaneous nerve.

Description:The ulnar nerve supplies the lumbricals, which are small muscles that help to flex the fingers. However, the ulnar nerve does not supply all of the lumbricals. The lumbricals of the index and middle fingers are supplied by the median nerve. Therefore, if the ulnar nerve is severed above the elbow, it will not cause paralysis of all of the lumbricals. The ulnar nerve also supplies the flexor carpi ulnaris, the flexor profundus, and the interossei muscles. Therefore, if the ulnar nerve is severed above the elbow, it will cause paralysis of these muscles, as well as complete loss of sensation in the 4th and 5th fingers.

Description:The triceps muscle is primarily supplied by the "c. Radial nerve." The radial nerve is a major nerve in the upper limb that innervates several muscles, including the triceps brachii muscle. Therefore, option c is the correct answer. The axillary nerve primarily supplies the deltoid muscle, the ulnar nerve supplies muscles in the forearm and hand, and the musculocutaneous nerve supplies the biceps brachii muscle.