Chapter 13: The Spinal Cord, Spinal Nerves, and Somatic Reflexes
In the spinal cord, the somas of the lower motor neurons are found in
Anterior Horns
Spinoreticular tract
Ascending Tract Anterolateral System carries pain signals resulting from tissue injury decussate Create reticular formation in the medulla and pons
Spinothalamic
Ascending Tract Anterolateraly System carries signals for pain, temp, pressure, tickle, itch and light or crude touch Decussate at second order neurons
Gracile Fasciculus
Ascending Tract carries signals from the midthoracic and lower parts of the body, below T6 Carry signals for vibration, viceral pain, deep and discriminative touch, proprioception
Posterior and Anterior Spinocerebellar
Ascending Tract carry proprioceptive signals from the limbs and trunk to the cerebellum at the rear of the brain Decussate
Cuneate Fasciculus
Ascending Tract occupies the lateral portion of the posterior column and forces the gracile fasciculus medially. carries same type of sensory signals as the gracile. T6 and up. Decussate at the medial lemniscus
Which plexus gives rise to the Axillary nerve?
Brachial Plexus
Which plexus gives rise to the Radial nerve?
Brachial Plexus
The brachial Plexus gives rise to all of the following nerves except a. axillary nerve b. radial nerve c. obturator nerve d. median nerve e. ulnar nerve
C. Obturator Nerve
Which plexus gives rise to the Phrenic nerve?
Cervical Plexus
Name the four major regions and two enlargements of the spinal cord
Cervical, Thoracic, lumbar, and Sacral regions Cervical Enlargement and Lumbar Enlargement
In the ____reflex, contraction of flexor muscles in one limb is accompanied by the contraction of extensor muscles in the contralateral limb
Crossed Extension
Decribe the distal end of the spinal cord and the contents of the vertebral canal from level L2 to S5
The cord tapers to a point called the medullary cone. Arising from the lumbar enlargement and medullary cone is a bundle of nerve roots that occupy the vertebral canal from L2 to S5. This bundle is the Cauda Equina.
The sciatic nerve is composite of two nerves, ______ and ______
Tibial, Common Fibular
At teh inferior end, the adult spinal cord ends before the vertebral column does
True
Each spinal cord segment has only one pair of spinal nerves
True
The anterior and posterior horns of the spinal cord are composed of gray matter
True
The corticospinal tracts carry motor signals down the spinal cord
True
The tendon reflex acts to inhibit muscle contraction
True
Thre crossing of a nerve fiber or tract from the right side of the CS to the left or vice cersa is called
decussation
Brachial Plexus
near the shoulder
Lumbar plexus
the lower back
The outermost connective tissue wrapping of a nerve is called the
Epineurium
Somatic reflexes are those that do not involve the brain
False
Some spinal nerves are sensory and others are motor
False
The dermatomes are nonoverlapping regions of skin innervated by different spinal nerves
False
The dura mater adheres tightly to the bone of the vertebral canal
False
The gracile fasciculus is a descending spinal tract
False
Nerve fibers that adjust the tension in a muscle spindle are called
Gamma Motor Neurons
Outside the CNS, the somas of neurons are clustered in swellings called ______
Ganglia
Name five structural components of a typical somatic reflex arc.
I. somatic receptors II. Afferent nerve fibers III. Integrating Center IV. Efferent Nerve fibers V. Effectors
Modified muscle fibers serving primarily to detect strech are called______
Intrafusal Fibers
Which plexus gives rise to the Ilioinguinal nerve?
Lumbar Plexus
Which plexus gives rise to the Obturator nerve?
Lumbar Plexus
Which plexus gives rise to the Sciatic nerve?
Lumbar Plexus
Sacral plexus
immediately inferior
Give an anatomical explanation of why a stroke in the right cerebral hemisphere can paralyze the limbs of the left side of the body
Decussation: meaning that they cross over from the left side of the body to the right side or vice versa. As a result the left side of the brain receives sensory information from the right side of the body and sends motor commands to that side, while the right side of the brain senses and controls the left side of the body
Tectospinal Tract
Descending Tract begins in midbrain - tectum involved in reflex turning of head
Corticospinal Tract
Descending Tract carry motor signals from the cerebral cortex for precise, finely coordinated limb movement. Decussate
Lateral and Medial Reticulospinal
Descending Tract originate in the reticular formation of the brainstem. Control muscles of the upper and lower limbs, maintain psture and balance
Lateral and Medial Vestibulospinal
Descending Tract Begin in brainstem, vestibular nuclei, which receives impulses for balance from the inner ear. Important in reponding to body tilt.
Which of these is not a region of the spinal cord? a. cervical b. thoracic c. pelvic d. lumbar e. sacral
Pelvic
The _____ nerves arise from the cervical plexus and innervate the diaphragm
Phrenic
The _____ganglion contains the somas of neurons that carry sensory signals to the spinal cord
Posterior root
Distal to the intervertebral foramen, a spinal nerve branches into an anterior and posterior ____
Ramus
A strech reflex requires the action of _______ to prevent an atagonistic muslce from interfering with the agonist
Reciprical inhibition
Which plexus gives rise to the Pudendal nerve?
Sacral and Coccygeal Plexuses
Anterior Root (Ventral)
Six to eight nerve rootlets emerge from the anterior survace and converge Motor
Posterior Root (dorsal)
Six to eight rootlets emerg from the posterior surface adn converge Sensory
The Cerebellum receives feedback from the muscles and joints by way of the ____ tracts of the spinal cord
Spinorcerebellar
A patient has a gunshot wound that caused a bone fragement to nick the spinal cord. The patient now feels no pain or temperature sensations from that level of the body down. Most likely the ______ was damaged
Spinothalamic
Below L2, the vertebral canal is occupied by a bundle of spinal nerve roots called
The Cauda Equina
Intrafusal Fiber
The muscle fibers within the spindle
Cervical Plexus
The neck
Coccygeal Plexus
adjacent to the lower sacrum and coccyx
Anulospiral Ending
after entering the muscle spindle, the fiber divides into two flat, ribbonlike branches that wind themselves in rings or spirals about the intrafusal muscle fibers.
The nonvisual awareness of the body's position and movements is called____
proprioception
Gamma Motor Neuron
relatively small-diameter, slow motor nerve fibers
All Somatic reflexes share all of the following properties except: a. they are quick b. they are monosynaptic c. they require stimultion d. they are involuntary e. they are sterotyped
they are monosynatpic