Physiology Revision - Spinal Cord and Spinal Tracts Flashcards
Where is the grey matter located in the spinal cord?
In the middle of the horn
White matter makes up the outside fibers that carries info to and from the spinal cord/cortex
Which horn does SENSEORY info come out of the spinal cord? What kind of sensory info?
The DORSAL horn
Sensory info: fine touch, proprioception, vibration, pain, temperature
Which horn does MOTOR info come into the spinal cord?
The VENTRAL horn
- Motor neurons make direct contact with muscles
- Stimulation of these neurons causes movement
What is somatotopy?
Somatotopy maps
Somatotopy is a point-for-point correspondence of an area of the body to a specific point on the central nervous system and spinal cord.
Adjacent neurons in the neural tissue respond selectively to stimuli presented to adjacent locations on the body
What are the 2 major descending systems and the 2 major ascending systems? What is the basic function of each?
2 major descending systems:
- Lateral descending system consists of the Corticospinal (influences general movement across the body especially indiv. finger movements) and Rubrospinal tracts (controls muscle tone in flexor groups and reach-to-grasp movements)
- Medial descending system consists of the Vestibulospinal (balance and spatial orientation) and the Reticulospinal tracts (posture and balance during our own volitional movements - internal disturbances)
2 major ascending systems:
- Medial lemniscus/Dorsal Column Pathway (carries sensory info on fine touch, vibration, two-point discrimination, proprioception)
- Spinothalamic Pathway/Anterolateral Pathway (carries sensory info about crude touch, pain, temperature)
Where does the Vestibulospinal tract originate from and what does it do?
The vestibulospinal tract originates from the vestibular nuclei in the medulla and pons.
This tract carries motor info of balance and spatial orientation to control axial (medial) musculature. Involuntary
Most of vestibular nuclei send their outputs to the SC and the muscles that move the eyes
Ex. river rafters going over a waterfall will tilt their body position
Where does the Reticulospinal tract originate from and what does it do?
The reticulospinal tract originates from the reticular formation/nuclei within the brainstem
This tract carries motor info of posture and balance during our own volitional movements - internal disturbances. Involuntary
Ex. brain predicts postural consequences of planned movements and prevents loss of balance (before lifting a weight, calf muscles excite to support posture)
Where does the Medial lemniscus/Dorsal Column tract originate from and what does it do? Does it decussate?
The Medial lemniscus/Dorsal Column tract originates from the dorsal root ganglion
Yes, axons decussate in the medulla, then ascend to the thalamus
The Medial lemniscus/Dorsal Column tract carries info from receptors on fine touch, vibration, two-point discrimination and proprioception
Where does the Spinothalamic/Anterolateral tract originate from and what does it do? Does it decussate?
The Spinothalamic/Anterolateral tract originates from the dorsal root ganglion
Yes, axons decussate in the grey mater of the SC then ascend to the thalamus
The Spinothalamic/Anterolateral tract carries info from receptors on crude touch, pain and temperature
Where does the Corticospinal tract originate from and what does it do? Does it decussate?
The Corticospinal tract originates from the cortex
Yes, axons decussate at the medulla
The Corticospinal tract influences general movement especially indiv. finger movement. Voluntary control
Where does the Rubrospinal Tract originate from and what does it do? Does it decussate?
The Rubrospinal tract originates from the red nucleus in the midbrain
Yes, axons decussate immediately after exiting the red nucleus. Its fibers terminate in the cervical and lumbar spine
The Rubrospinal tract controls muscle tone in flexor groups and controls shaping of the hand during reach-to-grasp movements
What is a dermatome?
A dermatome is an area of the skin innervated by nerves from a single dorsal root ganglion
The dermatome map is a generalized pattern. Dermatomes on the trunk of the body run horizontally, while dermatomes on the arms and legs run vertically
Dermatomes have some overlap
What is 2-point discrimination?
The ability to discern two nearby objects touching the skin; this reflects how finely innervated the area is
How many pairs of spinal nerves are there?
31 pairs of spinal nerves
- Parts of the body with more muscles and more sensory receptors will have larger nerves and therefore, spinal enlargements
Ex. Lumbar enlargement
