Spinal Cord
Lateral Horn
(only in thoracic regions)
Tendon Reflex
- Golgi tendon organs activated when tendon stretched. - Muscle relaxes - Antagonistic muscle contracts - Prevents tendon damage
Tracts of the Spinal Cord
- Highways for sensory and motor information (sensory tracts ascend, motor tracts descend)
Anterior Spinothalamic Tract
- In anterior part of the spinal cord - Impulses travel from spinal cord to thalamus
Indirect pathways (extrapyramidal tracts)
- "programmed" automatic movement - Co-ordinate gross movements and visual reflexes
Sensory Tracts
- Dorsal Columns - Spinothalamic - Spinocerebellar
Flexor reflex
- Draws limb away from painful stimulus - Pain signals activate motor fibers in several spinal cord segments - >1 muscle group activated to lift foot
Meninges
- Duramater is subdural space filled with interstitial fluid - Arachnoid mater is subarachnoid space filled with cerebrospinal fluid - Pia mater
Spinal Nerve Coverings
- Epineurium - Perineurium - Endoneirum
Crossed extensor reflex
- Extends contralateral limb to maintain balance - Pain signals to contralateral spinal cords - Contralateral extensors contract, flexors relax - Contralateral limb extends to support body
Reflex
- Fast, predictable, automatic responses to environmental changes
Spinal Cord Appearance
- Flattened cylinder 42-45cm long, 2 cm diameter - Lies within the spinal canal - Extends from the foramen magnum to L4 in newborn, to L1 in adults. - Growth of cord stops at age 5
Stretch Reflex
- Monosynaptic reflex - Prevents over-stretching injury
Spinothalamic Tract
- Pain, temperature, crude touch, deep pressure
Flexor and Crossed Extensor Reflexes
- Post synaptic reflexes
Direct pathways (pyramidal tracts)
- Precise, voluntary movements
Posterior (Dorsal) Columns
- Propioception - Discriminative Touch - Two point discrimination - Pressure - Vibration
Physiological Role of Reflexes
- Protection - minimizes duration of exposure to noxious stimuli - Maintain posture, balance - Co-ordination
Motor Tracts
- Pyramidal (corticospinal) - Extrapyramidal tracts
Intergrating Centers
- Regions in the CNS that relay impulses from sensory to motor neurons
Cervical Enlargement
enlargement in spinal cord in cervical region, a lot of information the spinal cord has to handle and work it has to do in that region
How many Spinal Nerves are there?
31 pairs of Spinal Nerves
Dermatone
- Area of skin supplied by one spinal nerve - Overlap of dermatones prevent loss of sensation if one spinal nerve is damaged (must block/cut 3 adjacent spinal nerves to induce local anesthesia)
Why does spinal cord growth stop at age 5?
- Because people get taller
Spinal Nerves
- Branch from spinal cord and emerge through intervertebral foramina = small holes - Mixed nerves (contain sensory and motor fibers)
Plexus
- Complex network of nerves - Switchbox for ventral rami of spinal nerves - Found in cervical, brachial, lumbar and sacral regions - s.n. T2-T12 don't form plexuses
Spinal Cord
- Conducts sensory impulses from body to brain - Conducts motor impulses from brain to body - Controls reflex activities
Conus Medullaris
- Cone shaped end of the spinal cord (where the spinal cord ends).
Dorsal Root Ganglion
- Contains cell bodies of sensory neurons
Ventral Root
- Contains motor vibers
Dorsal Root
- Contains sensory fibers
Integrating Centre for Spinal Reflexes
- Spinal cord serves as an integrating center for spinal reflexes
Spinal Reflexes
- Stretch Reflex - Tendon Reflex - Flexor (withdrawal) reflex - Crossed extensor reflex
Filum Terminale
- Thread like extension of pia mater - stabilizes spinal cord in the spinal canal
Spinocerebellar tract
- Unconscious propioception - Sensing balance
Cervical Plexus
- Ventral Rami of Spinal Nerves C1 to C5 - Innervates skin and muscles of the head and neck, and superior shoulders and chest.
Lumber Plexus
- Ventral Rami of Spinal Nerves L1 to L4 - Innervates abdominal wall, external genitals and anterior-medial thigh - Femoral Nerve
Sacral Plexus
- Ventral rami of Spinal Nerves L4 to S4 - Innervates buttocks, perineum and part of lower limb - Sciatic Nerve
Brachial Plexus
- Ventral rami of spinal nerves C5 to T1 - Innervate shoulder and upper limb - Roots merge to form superior, middle, and inferior trunks - Trunks merge to form lateral, posterior and medial cords - Most nerves branch from cords
Cauda Equina
-Dorsal, ventral roots of lowest spinal nerves
Dorsal Horn
Crescent shaped projection of gray matter within the spinal cord where sensory neurons enter the spinal cord
Axillary Nerve
Deltoid innervation
Spinal Nerves branch into what?
Dorsal and Ventral rami
Median Nerve
Forearm Innervation
C3,4,5
Keeps the diaphragm alive
Radial Nerve
Posterior of the arm
Spinal nerves emerge from spinal cord as what?
Roots
Dorsal and Ventral Roots join to form what?
Spinal Nerves
Musculocutaneous Nerve
Supply the anterior muscles of the arm
Ventral Column
Ventral white matter
Gray Commissure
a thin strip of gray matter that surrounds the central canal of the spinal cord and, along with the anterior white commissure, connects the two halves of the cord.
Dorsal Column
conveys two-point discrimination, vibratory and proprioceptive senses
Lumbar Enlargement
nerves of pelvis and lower limbs
Ventral Horn
somatic motor neurons whose axons exit the cord via ventral roots
Lateral Column
the white matter of the spinal cord lying on either side between the anterior median fissure and the ventral root.