A&P I Lecture Chapter 13 HW

A. Nociceptors respond to potentially damaging stimuli like noxious chemicals and extremes of temperature or pH. Nociceptors are generally associated with free nerve endings of specialized neurons.

B. Proprioceptors are sensitive to stimuli associated with body movements. The muscle spindle shown in B is responsive to muscle stretch.

Nerves are collection of axons of either sensory or motor neurons but not both. Nerves can be mixed collections of both sensory and motor axons.

endoneurium Within a nerve, each axon is surrounded by endoneurium, a delicate layer of loose connective tissue that also encloses the fiber's associated Schwann cells.

vagus nerve The vagus nerve has many targets in the thoracic and abdominal cavities and innervates many of the visceral organs.

abducens nerve The abducens carries efferent (motor) signals to the extrinsic eye muscle that abducts the eye (turns it laterally).

cervical plexus The phrenic nerve, which arises from the cervical plexus, supplies both motor and sensory fibers to the diaphragm, the main breathing muscle.

motor branches of ventral rami associated with the C3-C5 region of the spinal cord The ventral rami of spinal nerves contain motor fibers that originate from neuron soma found in the spinal cord. These efferent pathways activate the contraction of skeletal muscle. The phrenic nerve branches from this region and innervates the skeletal muscle of the diaphragm.

sternocleidomastoid muscle The sternocleidomastoid muscle is innervated by the accessory cranial nerve and branches of cervical spinal nerves C2 and C3.

cutaneous branches of the median nerve The median nerve cutaneous branch carries sensory input from the skin of the lateral 2/3rds of the hand, palm side and dorsum of fingers 2-3.

flex the wrist One action of the flexor carpi ulnaris muscle is wrist flexion. This muscle is innervated by the ulnar nerve.

segmental level, projection level, precommand level The hierarchy of motor control from lowest to highest level of control is segmental level, projection level, and precommand level.

interneurons In many cases, the interneurons are the integration point for reflexes, but they are not necessary.

modulation of descending motor pathways by brainstem and cortex

afferent sensory neuron A is an afferent sensory neuron carrying information from the muscle to the CNS.

determination of muscle length The muscle spindle indicated by F functions as a proprioceptor that is responsive to changes in the length of the surrounding muscle.

the contraction of muscle E A sudden stretch in a muscle leads to the contraction of the stretched muscle (E) and the relaxation of the antagonistic muscle (G).

rectus femoris The rectus femoris is one of the quadriceps. Stimulation of muscle spindles by tapping of the patellar ligament results in the reflex contraction of these muscles and the extension of the knee.

crossed-extensor reflex The grasped arm is withdrawn (via the flexor reflex) as the opposite arm pushes you away from the attacker (via crossed-extensor reflex). As in this scenario, the crossed-extensor reflex often accompanies the flexor reflex.