Block 5 Neurophysiotherapy BRS W Expl Part 2

Coordination of movement (synergy) is the function of the cerebellum. Lesions of the cerebellum cause ataxia, lack of coordination, poor execution of movement, delay in initiation of movement, and inability to perform rapidly alternating movements. The premotor and motor cortices plan and execute movements. Lesions of the substantia nigra, a component of the basal ganglia, result in tremors, lead-pipe rigidity, and poor muscle tone (Parkinson's disease).

Optic nerve fibers from both temporal receptor fields cross at the optic chiasm.

Flexor withdrawal is a polysynaptic reflex that is used when a person touches a hot stove or steps on a tack. On the ipsilateral side of the painful stimulus, there is flexion (withdrawal); on the contralateral side, there is extension to maintain balance.

The fast eye movement that occurs during a spin is nystagmus. It occurs in the same direction as the rotation. After the spin, post-rotatory nystagmus occurs in the opposite direction.

Group Ia afferent fibers innervate intrafusal fibers of the muscle spindle. When the intrafusal fibers are stretched, the group Ia fibers fire and activate the stretch reflex, which causes the muscle to return to its resting length.

Output of Purkinje cells from the cerebellar cortex to deep cerebellar nuclei is inhibitory. This output modulates movement and is responsible for the coordination that allows one to "catch a fly."

The chorda tympani [cranial nerve (CN) VII] is involved in taste; it innervates the anterior two-thirds of the tongue.

The semicircular canals are involved in angular acceleration or rotation. Hair cells of the right semicircular canal are excited (depolarized) when there is rotation to the right. This rotation causes bending of the tereocilia toward the kinocilia, and this bending produces depolarization of the hair cell. Ascent in an elevator would activate the saccules, which detect linear acceleration.

Receptor potentials are graded potentials that may bring the membrane potential of the receptor cell either toward (depolarizing) or away from (hyperpolarizing) threshold. Receptor potentials are not action potentials, although action potentials (which are all-or-none) may result if the membrane potential reaches threshold

Cerebrospinal fluid (CSF) is similar in composition to the interstitial fluid of the brain. Therefore, it is similar to an ultrafiltrate of plasma and has a very low protein concentration because large protein molecules cannot cross the blood–brain barrier. There are other differences in composition between CSF and blood that are created by transporters in the choroid plexus, but the low protein concentration of CSF is the most dramatic difference.

Cranial nerve (CN) I innervates the olfactory epithelium. Its axons are C fibers. Fracture of the cribriform plate can tear the delicate olfactory nerves and thereby eliminate the sense of smell (anosmia); however, the ability to detect ammonia is left intact. Olfactory receptor cells are unique in that they are true neurons that are continuously replaced
from undifferentiated stem cells.

Among the autonomic drugs, only B1 and B2 adrenergic agonists act by stimulating adenylate cyclase. Norepinephrine is a B1 agonist. Atropine is a muscarinic cholinergic antagonist. Clonidine is an a2 adrenergic agonist. Curare is a nicotinic cholinergic antagonist. Phentolamine is an al adrenergic antagonist. Phenylephrine is an al adrenergic agonist. Propranolol is a B1 and B2 adrenergic antagonist.

Transection of the spinal cord causes "spinal shock" and loss of all reflexes below the level of the lesion. These reflexes, which are local circuits within the spinal cord, will return with time or become hypersensitive. Proprioception is permanently (rather than temporarily) lost because of the interruption of sensory nerve fibers. Fibers above the lesion are intact.

Pathogens release interleukin-1 (IL-1) from phagocytic cells. IL- 1 then acts to increase the production of prostaglandins, ultimately raising the temperature set point in the anterior hypothalamus. The hypothalamus now "thinks" that the body temperature is too low (because the core temperature is lower than the new set-point temperature) and initiates mechanisms for generating heat—shivering, vasoconstriction, and shunting of blood away from the venous plexus near the skin surface.

Photoreception involves the following steps. Light converts 11-cis retinal to all-trans retinal, which is converted to such intermediates as metarhodopsin II. Metarhodopsin II activates a stimulatory G protein (transducin), which activates a phosphodiesterase. Phosphodiesterase breaks down cyclic guanosine monophosphate (cGMP), so intracellular
cGMP levels decrease, causing closure of Na + channels in the photoreceptor cell membrane and hyperpolarization. Hyperpolarization of the photoreceptor cell membrane inhibits the release of neurotransmitter. If the neurotransmitter is excitatory, then the bipolar cell will be hyperpolarized (inhibited). If the neurotransmitter is inhibitory, then the bipolar cell will be depolarized (excited).

Explanation: Nuclear bag fibers are a type of intrafusal muscle fiber found within muscle spindles. They are specialized to detect dynamic changes in muscle length and the rate of change in length. These fibers are essential for proprioception, providing the central nervous system with information about muscle stretch and movement. They are not extrafusal muscle fibers, do not give rise to group Ib afferents, and are not innervated by alpha-motoneurons; instead, they are typically associated with gamma-motoneurons.

B2 Receptors on vascular smooth muscle produce vasodilation. a Receptors on vascular smooth muscle produce vasoconstriction. Because 02 receptors are more sensitive to epinephrine than are a receptors, low doses of epinephrine produce vasodilation, and high doses produce vasoconstriction.