Nervous System

The sympathetic division “stirs you up”. The ANS and somatic NS are distinct parts of the efferent section of the peripheral nervous system. The parasympathetic division is “craniosacral” not “thoracolumbar”.

Saltatory conduction refers to the action potential “jumping” from node to node of a myelinated neuron. Myelin is a lipid, not a protein. Myelin surrounds the axon, not the dendrite. (The peripheral sensory neurons have myelinated dendrites. Short dendrites in the central nervous system are not myelinated.)

The vagus nerve carries 90% of parasympathetic motor impulses. It arises mainly from the medulla oblongata.

The BBB is a selectively permeable barrier to many water-soluble particles that is incomplete at birth.

The patellar reflex affects the leg below the knee. The leg (anatomically between the knee and ankle) kicks out. This is extension not flexion.

It is ascending – going from spine to thalamus – and ascending tracts carry sensory information to the brain.

The ventral root contains axons of motor neurons. That is, they carry motor information from the brain to the body – this is efferent (outgoing) information.

The optic chiasma (crossing) allows the stimulation produced by light striking the rods and cones on the medial aspect of one eye to cross over to the other side of the brain to travel with the stimulation produced in the lateral aspect of the other eye. Hence some information from each eye is interpreted together in each side of the occipital lobe. In this way, binocular vision and the perception of distance are achieved.

Most sensory neurones are unipolar, that is, the axon and dendrites are not separated by the cell body but are the one strand (are fused), with the cell body attached to it by a single process.

Fat-soluble molecules can pass the BBB, but most charged particles cannot.