spinal cord & nerves

What are the functions of the spinal cord?

Conduction: information from body → brain & vice versa

Locomotion: continuation of walking

Reflexes: involuntary responses to stimuli

What are the regions of the spinal cord?

• Cervical region

• Thoracic region

• Lumbar region

• Sacral region

• Coccygeal region

What is different between the cervical and lumbar regions and why?

Cervical Enlargement: nerves for upper extremities

Lumbar Enlargement: nerves for lower extremities

What are the structures of the spinal cord that are important for this chapter?

Conus medullaris (54)

Cauda equina (53)

Terminal filum

Anterior median fissure / Ventral median fissure

Posterior median sulcus / Dorsal median sulcus

Functions of Meninges in Spinal Cord

Meninges: fibrous connective tissue that surrounds the CNS

❑ Epidural space: between vertebra and dura mater; contains blood vessels, adipose tissue, and areolar connective tissue (location where anesthetics are introduced)

– Dura mater: outermost layer for stability

❑ Subdural space: potential space between the dura mater and the arachnoid mater

– Arachnoid mater: simple squamous epithelium + mesh of collagenous and elastic fibers

❑ Subarachnoid space: filled with CSF

– Pia mater: innermost layer that is on the surface of the spinal cord made of elastic and collagen fibers

• Terminal filum: extension of the pia mater

What are the different parts of gray matter in the spinal cord?

Posterior horns / Dorsal horns

Anterior horns / Ventral horns

Lateral horns

Gray commissure

What is the space within the spinal cord called? How is it different from adults vs children?

Central canal

contains CSF that has ependymal cells in children

What are the different parts of white matter in the spine?

Posterior column / Posterior funiculus / Dorsal column / Dorsal funiculus

Lateral column / Lateral funiculi

Anterior column / Anterior funiculus / Ventral column / Ventral funicul

What information do ascending vs descending tracts carry?

Ascending tracts: carries sensory information up the spinal cord

Descending tracts: carry motor information down the spinal cord

What are decussation, ipsilateral, contralateral?

Decussation: crossing over from left to right side of the body (vice versa)

Ipsilateral: no decussation occurs so tracts are on the same side

Contralateral: decussation occurs and tracts crosses over to other side of the body

How many spinal nerves do we have?

31 Pairs

Where does the first spinal nerve go through?

First pair between skull and C1

How many spinal nerves for each region of the spinal cord

– 8 Cervical (C1-8)

– 12 Thoracic (T1-12)

– 5 Lumbar (L1-5)

– 5 Sacral (S1-5)

– 1 Coccygeal (Co)

What type of information goes through the spinal nerve proper?

sensory and motor information

If it is sensory information what are the structures it’ll go to next from the spinal nerve proper?

Dorsal horn → Dorsal root → Dorsal root ganglion

If it is motor information, what are all the structures that motor information comes from that goes to the spinal nerve proper?

Ventral horn → Ventral root

What type of information is carried in the posterior ramus and where does it go to?

carries all sensory, motor, and visceral

innervates the muscles and joints in spine (ie: erector spinae) and back skin

What type of information is carried in the anterior ramus and where does it go to?

carries all sensory, motor, and visceral

innervates the anterior and lateral skin and muscles of the trunks and nerves of limbs

What structures comes off of/goes through the anterior/posterior ramus and what do they do?

Communicating rami: connects to sympathetic chain ganglia

• Gray Communicating Ramus

• White Communicating Ramus

Intercostal nerve: thoracic region innervating skin and intercostal muscles, and abdominal muscles

Nerve plexuses: group of spinal nerves coming and dispersing

What is a dermatome?

area of skin where each spinal nerve innervates

What is referred visceral pain?

pain from an organ that is referred to a dermatome

What are the different nerve plexuses?

Cervical plexus

Brachial plexus

Lumbar plexus

Sacral plexus

Coccygeal plexus

What nerve comes off of the cervical plexus and its function?

Phrenic nerve

Which spinal nerves make up this Phrenic nerve?

C3 - C5

What divisions come off of the brachial plexus?

Posterior and Anterior division

What nerves come from each division off of the brachial plexus?

• Posterior division

  • Axillary nerve: sensory information from shoulder and arm; muscular innervation for deltoid and teres minor muscles

  • Radial nerve: sensory information from the posterior arm and forearm; muscular innervation for the extensor muscles of arm and forearm

• Anterior division

  • Musculocutaneous nerve: sensory information of the lateral forearm; muscular innervation for anterior arm muscles

  • Median nerve: sensory information of from hand, digits; innervates muscles of the forearm flexors

  • Ulnar nerve: sensory information of the medial part of the hand and digits; innervates muscles of the forearm flexors

What nerve comes off the lumbar plexus and what does it do?

Femoral nerve

What nerves come off the sacral plexus and its functions.

Sciatic nerve: largest and longest nerve; innervates hamstring muscles

What nerves does the sciatic nerve become and its functions?

Tibial nerve: Supplies sensory information from posterior leg and sole of the foot

Common fibular nerve

What are reflexes and its properties?

quick, involuntary, stereotyped reactions of glands or muscles

• Stimulation: reflexes respond to some stimulus

• Quick: contain little to no interneurons

• Involuntary: reflexes occur without higher brain centers involved

What are the components of a reflex arc and its order? (7 steps)

1. Stimulus

2. Receptor

3. Afferent neuron / Sensory neuron

4. Integrating center

5. Efferent neuron / Motor neuron

6. Effector

7. Response

What are the different proprioceptors and its function and locations they are found?

Muscle spindles

Golgi tendon organs

Joint kinesthetic receptors

Name a specific type of stretch reflex?

Patellar/knee-jerk reflex

What type of reflex is the Patellar/knee-jerk reflex?

Tendon reflex

What is a monosynaptic vs polysynaptic reflex arc?

Monosynaptic reflex arc: primary afferent neuron synapses directly on the motor neurons

Polysynaptic reflex arc: involves multiple synapses

Is the monosynaptic reflex or the polysynaptic reflex arc faster?

Monosynaptic, because it connects with only one synapse

What is a withdrawal/flexor reflex?

contracts flexor muscles to withdraw limb from injury also causing reciprocal inhibition

What type of reflex is the withdrawal/flexor reflex?

Polysynaptic reflex arc

Name all the structures sensory information will go through from receptor to CNS (8)

1. Sensory Receptor

2. Peripheral Sensory Neuron

3. Dorsal Root Ganglion

4. Dorsal Root

5. Dorsal Gray Horn

6. Ascending Tract

7. Brainstem

8. Primary Sensory Cortex

Name all the structures motor information will go through from CNS to effector (8)

1. Cerebral Motor Cortex

2. Upper Motor Neuron

3. Brainstem

4. Spinal Cord

5. Lower Motor Neuron

6. Ventral Root

7. Neuromuscular Junction

8. Effector