Lecture 2: Spinal cord

Question 1

What is the purpose of the spinal cord

Answer 1

Send motor information from the CNS (brain) to the PNS (skin) and sensory information from the PNS to the CNS

Question 2

How the 31 nerves in the spinal cord divided up top to bottom

Answer 2

8 pairs of cervical nerves, 12 pairs thoracic nerves matching the ribs, 5 pairs of lumbar nerves, 5 pairs of sacral nerves and 1 pair of coccygeal nerves.

Question 3

What are the two enlargements on the spinal cord and why

Answer 3

Cervical enlargement- where all the sensory/ motor info for arms and hands are
Lumbar enlargement- where all the sensory/motor info for legs is.
Enlargement because they need more SA for more neurons

Question 4

What is the cauda equina

Answer 4

The horses tail, roots of the lumbar, sarcral and coccygeal nerves that spread out laterally

Question 5

What is the conus medullaris

Answer 5

Cone shaped end of the spinal cord

Question 6

What are dermatones

Answer 6

They are segments of the body that provides sensory input to the CNS through one pair of spinal nerves. As these areas are mapped, and although there can be some overlap between areas, they can be used to determine if there is damage to specific parts of the spinal cord

Question 7

What is the organisation of white matter and grey matter in the spinal cord and the orientation regarding anterior and posterior

Answer 7

White matter on the outside and grey matter butterfly in the middle The small wings of the butterfly are closest to the posterior

Question 8

How is the white matter of the spinal cord organised

Answer 8

Into three white columns sectioned off by the butterfly: anterior, posterior and lateral. These contain distinct bundles of axons going to the same destination carrying the same information= tracts.

Question 9

How is the grey matter of the spinal cord organised and what does each section contain

Answer 9

The tips of the butterfly are called ‘horns’. The posterior horns (small wing tips) contain the axons of incoming sensory neurons and interneurons. The anterior horns (bigger wing tips) contain somatic motor nuclei that give nerve impulses for skeletal muscle. The lateral horns- in the middle of the edge of the butterfly have autonomic motor neurons for cardiac, smooth and glands.

Question 10

What are ‘nuclei’ in grey matter and the two types

Answer 10

clusters of neuronal cell bodies that form functional groups. Sensory nuclei receive input from sensory neurons and motor nuclei provide output to effector tissues via motor neurons.

Question 11

Where do the cell bodies of incoming sensory neurons located in

Answer 11

the posterior (dorsal) root ganglion of the spinal nerve

Question 12

Where does sensory information sent to the CNS (general afferent pathway) first enter at what root

Answer 12

Nerve impulses from the sensory receptor go along the axon which enters the spinal cord at the posterior (dorsal) root. The cell bodies are in the dorsal root ganglia. They can then go 3 possible pathways

Question 13

What are the 3 possible pathways for sensory information to go from once it enters the spinal cord

Answer 13

1. Axons can extend into the white matter of the spinal cord and ascend into the brain as part of the sensory tract.
2. Axons of neurons may enter the posterior grey horn and synapse with interneurons whose axons extend into the white matter of the spinal cord.
3. Axons of neurons may enter the posterior grey horn and synapse with interneurons that in turn synapse with somatic motor neurons involved in spinal reflex pathways

Question 14

What is the difference between the first order neurons that carry touch/pressure and pain/temperature sensation

Answer 14

Pain and temperature is carried by unmyelinated neurons with free nerve endings.
Touch and pressure are carried by myelinated pseudounipolar neurons with encapsulated nerve endings

Question 15

The capsule of the nerve ending determines what type of information a nerve will respond to. What are the names of the different capsules for touch and pressure

Answer 15

touch: Meisners corpuscles, Pressure is pacinian corpuscle.

Question 16

Define sensation vs perception

Answer 16

The conscious or subconscious awareness of changes in the external or internal environments. Perception of sensation only happens when impulses reach the cerebral cortex.

Question 17

Each neuron only transmits information about one sensory modality. What is a sensory modality

Answer 17

A unique type of sensation- one type of sensory information.

Question 18

What are the four kind steps that lead to sensation being felt

Answer 18

1. Stimulation of the sensory receptor
2. Energy of Stimulus converted to graded potential (transduction)
3. Generation of nerve impulse that go to CNS
4. Integration of sensory input in the cerebral cortex which leads to perception.

Question 19

What are three main layers of the protective structures for the spinal cord and brain (CNS)

Answer 19

1. The outer skull/ vetebral column made of bone
2. The three connective tissue layers of the meninges
3. The cerebrospinal fluid/ fat and connective tissue in the space between two of the meningeal membranes

Question 20

What is the order of the 3 spinal meningeal membranes from outside to inside

Answer 20

Dura mater, Arachnoid mater and Pia mater.

Question 21

Describe the dura mater. What is it continuous with

Answer 21

Thick strong layer of dense irregular connective tissue. It forms a sac form the foramen magnum in brain to sacral vertebra 2. It is continuous with the meningeal dura mater of the brain and epineurium

Question 22

What is the epineurium

Answer 22

the outer covering of spinal and cranial nerves

Question 23

Describe the Arachnoid mater. What is it continuous with

Answer 23

Middle layer. It is a thin avascular covering made of cells and loosely arranged collagen and elastin fibres. Through the foramen magnum It is continous with the arachnoid mater of the brain

Question 24

Where is the subdural space and what does it contain

Answer 24

Between the dura mater and arachnoid mater and it contains interstitial fluid

Question 25

Describe the Pia mater. What other structures are at this layer

Answer 25

Thin transparent connective tissue layer that sticks to the surface of the spinal cord and brain. It is thin squamous cuboidal cells with collagen and elastic fibres interlacing.
At this layer there are blood vessels for the spinal cord and denticulate ligaments.

Question 26

What is the subarachnoid space and what does it contain

Answer 26

Between arachnoid and pia mater space containing shock absorbing cerebrospinal fluid.

Question 27

What are denticulate ligaments

Answer 27

triangular Thickenings of pia mater that stick outwards and fuse with the arachnoid mater + inner surface of dura mater between the nerve roots entering the spinal cords at both sides

Question 28

What is in the epidural space and where is it

Answer 28

Space between the dura mater and wall of the vertebral canal. It contains fat and connective tissue.