Nervous System and Neurons

The neuron (nerve cell) is the fundamental structural and functional unit of the nervous system. Axons and dendrites are parts of a neuron, not independent units. Neuralgia is a condition involving nerve pain.

Connexins are four-pass transmembrane proteins with both C and N cytoplasmic termini.

Goose pimples (piloerection) are controlled by the sympathetic nervous system, which is part of the autonomic nervous system. This involuntary response causes arrector pili muscles to contract, forming goose bumps.

Complete parts of a Neuron

The Na+/K+ ATPase pump actively transports 3 Na+ out and 2 K+ in against their concentration gradients, using ATP to establish the resting membrane potential (~-70mV). Depolarization and repolarization are passive ion flows down gradients once the resting potential is established.

A is correct because if inhibiting nerve growth is merely a by-product of the inhibitors' main function, then deactivating them could interfere with essential biological processes, casting doubt on whether nerve repair will become routine. B is irrelevant because chemical similarity between stimulants and antibodies does not impact the argument. C discusses brain nerves, not spinal cord nerves, so it is out of scope. D refers to nerves outside the spinal cord, which does not help explain why spinal nerve repair specifically would fail. E discusses a practical delivery issue rather than a fundamental biological barrier, so it is less damaging to the conclusion.

The tibialis anterior muscle in humans is percepted from the L4-S1 roots, particularly the L5 and to a lesser extent L4 root through the sciatic and ultimately the deep peroneal nerves.

Celiac ganglion is the largest group of sympathetic prevertebral ganglia on the upper part of the abdominal aorta on either side of the celiac artery, containing the sympathetic neurons. The axons of the greater and least splanchnic nerves synapse on the postganglionic neurons located in the celiac ganglion.

The optic nerve (Cranial Nerve II) is the second cranial nerve and transmits visual information from the retina to the brain. The olfactory nerve (CN I) is first, and other nerves like abducens (CN VI) and trigeminal (CN V) have different numbers and functions.

The trigeminal nerve (CN V) is the fifth cranial nerve, responsible for sensation in the face and motor functions like biting and chewing. Occulomotor is CN III, facial is CN VII, and glossopharyngeal is CN IX.

The parasympathetic nervous system uses acetylcholine as its neurotransmitter at both preganglionic and postganglionic nerve endings. This cholinergic transmission is what produces 'rest and digest' effects like slowing heart rate and increasing digestion.

The olfactory nerve (Cranial Nerve I) is the first cranial nerve, responsible for the sense of smell. It's unique among cranial nerves as it can regenerate and conducts smell signals from the nasal epithelium directly to the brain.

In ulnar nerve injury, adduction of the thumb is impaired due to paralysis of the adductor pollicis muscle. The other options (claw hand, hypothenar atrophy, sensory loss) are all clinical findings that DO occur in ulnar nerve injury.

Fast axonal transport relies on microtubule tracks and molecular motors: kinesin (anterograde transport) and dynein (retrograde transport). Microfilaments (actin) participate in slow axonal transport. Neurofilaments are structural intermediate filaments that provide cytoskeletal support and do NOT participate in active transport.