spinal cord (I)

Question 1

Where do primary somatic sensory afferents project to?

Answer 1

The spinal cord

Question 2

Spinal cord dimensions

Answer 2

• 42-45 cm long
• ≤ 1 cm in diameter

Question 3

Spinal cord segments

Answer 3

31 segments, each of which corresponds to the entry point of a pair of spinal nerves.

→8 cervical
→12 thoracic
→5 lumbar
→5 sacral
→1 coccygeal

Question 4

Cervical and lumbar enlargements

Answer 4

Correspond to the segments that innervate the limbs

Question 5

Lumbar cistern

Answer 5

The subarachnoid space in the lower lumbar spinal canal.

• no spinal cord here
• filled with CSF
• filled with nerves
  (where needles are inserted to not potentially damage spinal cord higher up!)

Question 6

Cauda equina

Answer 6

The cauda equina is the bundle of nerve roots located at the lower end of the spinal cord.

Question 7

Foramen magnum

Answer 7

Place where the cord enters the skull to form the medulla.

Question 8

Medulla

Answer 8

Most caudal region of the region of the brainstem.

Question 9

Spinal cord composition

Answer 9

1. Central grey matter
2. Surrounding white matter

Question 10

Ventral horn

Answer 10

-part of the grey matter
-mainly involved in movement

Question 11

Dorsal horn

Answer 11

-part of the grey matter
-mainly involved in sensory function

Question 12

Grey matter

Answer 12

Regions of the nervous system consisting mainly of (1) neuronal cell bodies, (2) dendrites and (3) synapses

Question 13

White matter

Answer 13

Bundles of myelinated axons.

Question 14

General cross-sectional anatomy of the spinal cord: Fill in the blanks

Answer 14

☆slide 37☆

Question 15

Ganglion

Answer 15

An organized cluster of neuronal cell bodies in the peripheral nervous system.

Question 16

Nucleus

Answer 16

An organized cluster of neuronal cell bodies in the central nervous system.

Question 17

Number of spinal nerves

Answer 17

There are 31 pairs of spinal nerves running down the length of the spinal cord.

Question 18

How do primary somatic sensory afferents enter the dorsal spinal cord?
(Draw it!)

Answer 18

Through the dorsal roots.

→fibers come in and branch out through the dorsal root

Question 19

How do motor neurons project to skeletal muscle fibers?
(Draw it!)

Answer 19

Through the ventral roots.

→in the ventral horn of the spinal cord grey matter, we have the cell bodies of motor neurons that are going out to control the skeletal muscles, they then send their axons out through the ventral root

Question 20

What procedure can be done in cases of SEVERE pain?

Answer 20

An individual may have the dorsal root cut off ONLY in the case of severe pain.

Question 21

Dermatome

Answer 21

Each pair of spinal nerves innervates a region of the body surface called a dermatome.

(i.e. if nerve 2 is damaged, then so will sensory ability of region C2)

Question 22

What does the intermediate region of the spinal cord grey matter contain?

Answer 22

The intermediate region contains interneurons and preganglionic autonomic neurons

Question 23

Interneuron role

Answer 23

-connecting different neurons
-involved in integrative processes
-found in the grey matter
-allow for intrinsic circuitry

Question 24

Fine touch primary afferent root in spinal cord

Answer 24

Primary afferents for fine touch enter the dorsal columns and ascend to the dorsal column nuclei in the brainstem.

→can go to grey matter or white matter directly
→ipsilateral

Question 25

Pain & temperature primary afferent root in spinal cord

Answer 25

Primary pain and temperature afferents synapse in the dorsal horn of the spinal cord grey matter. The second neuron crosses over toward the anterolateral column.

→contralateral

Question 26

Dorsal columns and anterolateral columns organization

Answer 26

They are somatotopically organized.

→fine touch: arms located laterally, legs located medially
→pain & temp.: arms located medially, legs located laterally

Question 27

How far is somatotopic organization conserved?

Answer 27

Somatotopic organization is conserved throughout the entire sensory pathway.

Question 28

Sensory-motor hierarchy
(Draw it!)

Answer 28

The spinal cord is part of a sensory-motor hierarchy that includes the brainstem and higher brain regions including the cerebral cortex, the cerebellum and the basal ganglia.

Question 29

Sensory-motor hierarchy: Motor cortex

Answer 29

-complex voluntary movements
-fine motor control

Question 30

Sensory-motor hierarchy: Brainstem

Answer 30

-automatic behaviour
-respiration
-chewing
-expressions
-stereotyped behaviour

Question 31

Sensory-motor hierarchy: Spinal cord

Answer 31

-protective reflexes
-locomotion

Question 32

Stretch reflex

Answer 32

-one of the simplest of sensory to motor movements
-mediated by the spinal cord

→proprioceptive neurons get activated and they send axons into the spinal cord (main branch goes up to the brainstem, so our brain has some information about what’s going on), but there’s a branch that goes into the spinal cord grey matter and directly activates motor neurons in the spinal cord, causing the muscle to contract

Question 33

Withdrawal reflex

Answer 33

-one of the simplest of sensory to motor movements
-mediated by the spinal cord

→when you touch a hot stove, primary nociceptors are activated, which then send a signal to the spinal cord, which activates motor neurons in the spinal cord and then your hand can pull away

Question 34

Central pattern generator

Answer 34

Formed by the intrinsic circuitry of the spinal cord responsible for rhythmic movements like walking, scratching…

→facilitated by interneurons