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.