Block 5 Neurophysiotherapy BRS W Expl Part 1

Representation on the motor homunculus is greatest for those structures that are involved in the most complicated movements—the fingers, hands, and face.

Cutting the optic nerve from the left eye causes blindness in the left eye because the fibers have not yet crossed at the optic chiasm.

C fibers (slow pain) are the smallest nerve fibers and therefore have the slowest conduction velocity.

The stretch reflex is the monosynaptic response to stretching of a muscle. The reflex produces contraction and then shortening of the muscle that was originally stretched (homonymous muscle).

Of the two types of photoreceptors, the rods are more sensitive to low-intensity light and therefore are more important than the cones for night vision. They adapt to darkness after the cones. Rods are not present in the fovea. The cones are primarily involved in color vision.

Fibers from the left temporal field and the right nasal field ascend together in the right optic tract.

Erection is a parasympathetic muscarinic response. Dilation of the bronchioles, ejaculation, constriction of the gastrointestinal (GI) sphincters, and increased cardiac contractility are all sympathetic a or f3 responses.

Heart rate is increased by the stimulatory effect of norepinephrine on B1 receptors in the sinoatrial (SA) node. There are also sympathetic pi receptors in the heart that regulate contractility.

Asthma, a disease involving increased resistance of the upper airways, is treated by administering drugs that produce bronchiolar dilation (i.e.,B2 agonists). B2 Agonists include isoproterenol, albuterol, epinephrine, and, to a lesser extent, norepinephrine. Antagonists, such as propranolol, are strictly contraindicated because they cause constriction of the bronchioles.

Sympathetic preganglionic neurons originate in spinal cord segments T1–L3. Thus, the designation is thoracolumbar. The sympathetic nervous system is further characterized by short preganglionic neurons that synapse in ganglia located in the paravertebral chain (not in the effector organs) and postganglionic neurons that release
norepinephrine (not epinephrine). Common features of the sympathetic and parasympathetic nervous systems are preganglionic neurons that release acetylcholine (ACh) and postganglionic neurons that synapse in effector organs.

Sound frequencies can be encoded by the organ of Corti because of differences in properties along the basilar membrane. The base of the basilar membrane is narrow and stiff, and hair cells on it are activated by high frequencies. The apex of the basilar membrane is wide and compliant, and hair cells on it are activated by low frequencies.

Preganglionic sympathetic fibers synapse on the chromaffin cells of the adrenal medulla at a nicotinic receptor. Epinephrine (and, to a lesser extent, norepinephrine) are released into the circulation.

Hexamethonium is a nicotinic blacker, but it acts only at ganglionic (not neuromuscular junction) nicotinic receptors. This pharmacologic distinction emphasizes that nicotinic receptors at these two locations, although similar, are not identical.

Adrenergic a l receptors produce physiologic actions by stimulating the formation of inositol 1,4,5-triphosphate (IP3) and causing a subsequent increase in intracellular [Ca2+]. Both B1 and B2 receptors act by stimulating adenylate cyclase and increasing the production of cyclic adenosine monophosphate (cAMP). a 2 Receptors inhibit adenylate cyclase and decrease cAMP levels. Muscarinic and nicotinic receptors are cholinergic.

Complex cells respond to moving bars or edges with the correct orientation. Simple cells respond to stationary bars, and hypercomplex cells respond to lines, curves, and angles. Bipolar and ganglion cells are found in the retina, not in the visual cortex.

Decerebrate rigidity is caused by increased reflex musclespindle activity. Stimulation of group Ia afferents would enhance, not diminish, this reflex activity. Cutting the dorsal roots would block the reflexes. Stimulation of a- and y-motoneurons would stimulate muscles directly.

Prazosin is a specific antagonist of al receptors, which are present in vascular smooth muscle, but not in the heart. Inhibition of a l receptors results in vasodilation of the cutaneous and splanchnic vascular beds, decreased total peripheral resistance, and decreased blood pressure.