Lecture 3: Intro to the Nervous system and Spinal Cord

What makes up the CNS?

Brain and spinal cord

What makes the PNS?

Nerves that go to and from the central nervous system.

What is the visceral part of the nervous system?

Subdivision of the nervous system that innervates organ systems

What is the somatic part of the nervous system?

Subdivision of the nervous system that innervates structures (like skin and skeletal muscles)

Where is the somatic part of the nervous system derived?

Derived from somites in embryo

What does the ANS (autonomic nervous system) innervate?

• Smooth and cardiac muscles

• Secretory cells (glandular epithelium)

What does the ANS regulate?

It regulates involuntary reflexive control such as organ function and homeostasis.

In the autonomic nervous system, the ______ nerves monitor changes in the viscera. While ______ nerves innervate smooth muscle, cardiac muscle, and glands.

sensory nerves; motor nerves

What nervous system is in charge of fight or flight?

Sympathetic nervous system

What nervous system is in charge of rest and digest?

Parasympathetic nervous system

What structures does the ANS regulate?

• Digestion

• Circulation

• Respiration

• Excretion

• Reproduction

• Body temp

What spinal levels are associated with the sympathetic nervous system?

T1-L2/L3

What spinal levels are associated with the parasympathetic nervous system?

S2-4

What are the general somatic afferents (GSA)?

Somatic sensory neurons that carry info → CNS

What are the general somatic efferents (GSE)?

Somatic motor fibers that carry info away CNS → skeletal muscles

What are general visceral afferent (GVA)?

Visceral sensory neurons associated with chemoreception, mechanoreception, and stretch reception.

What are the general visceral efferents (GVE)?

Visceral motor neurons related to ANS

What are dermatomes?

Area of skin supplied by a spinal cord level or by a single spinal nerve.

What do dorsal root fibers supply?

Sensory innervation to a skin segment in the human body,

What is a mytotome?

Portion of a skeletal muscle that is innervated by a single spinal cord level or by a single spinal nerve.

What is the spinal cord responsible for?

• Motor reflexes

• Conduct sensory info (environment → brain)

• Contain pathways for motor impulses

What is grey matter?

Aggregation of cell bodies

What is white matter?

Bundles of neuronal axons.

In the CNS, grey matter consists of ______ and _______.

Cortex and nuclei

In the CNS, white matter consists of ______, _______ and _______.

Tracts, fibers, and columns

White matter consist of ___________ nerves and grey matter consist of _________ nerves.

Mylenated nerves; unmylenated nerves

In the PNS, grey matter consist of __________.

Ganglia

In the PNS, white matter consist of _________.

Fibers

How many pairs of spinal nerves are in total?

31 pairs.

How many pairs of cervical spinal nerves are there?

8

How many pairs of thoracic spinal nerves are there?

12

How many pairs of lumbar spinal nerves are there?

5

How many pairs of sacral spinal nerves are there?

5

How many pairs of coccygeal spinal nerves are there?

1

Why is there an increase of grey matter volume in the cervical and lumbosacral enlargements?

It’s for innervations of the limbs

_________ spinal segments contain the largest number of fibers in the white matter.

Cervical

Where is grey matter found the most?

In cervical and lumbar enlargements

List the layers of the spinal nerve in order from most external to internal.

1. Dura mater

2. Arachnoid mater

3. Pia mater

Where is the lateral horn of grey matter found?

The thoracic and upper lumbar segments.

What is the dorsal root?

It’s where afferent fibers (sensory) enter the spinal cord.

Where does the amount of white matter increase?

Caudal-to-rostral direction

Why does the amount of white matter increase from top to bottom?

There are more nerves running upwards and less nerves running down the body.

What are the ventral roots?

Where the efferent fibers (motor) leave spinal cord

What do axons of alpha motor neurons innervate?

Innvervate extrafusal skeletal muscle fibers

What do axons of gamma motor neurons innervate?

Innvervate intrafusal muscle spindle fibers → regulate muscle tone and adjust spindle sensitivity

What is a multipolar neuron? Give an example.

Neuron with many dendrites and one axon.

Ex: Motor neuron at ventral horn

What is bipolar neuron? What is an example?

One dendrite and one axon attached to the cell body.

Ex: Neurons in eye and ear

What is a unipolar neuron? What is an example?

Neuron with one process from the cell body (an axon).

Ex: Cell of dorsal root ganglion

The white matter consists of 3 funiculi such as ______, _______, and ______ funiculus.

Dorsal, lateral, and ventral

What are the two Rexed’s Laminae?

• Laminae I-VI: posterior/dorsal horn

• Laminae VII-IX: anterior/ventral horn

What makes up the Intermediolateral cell column (IML)? Also give spinal levels.

• Spinal levels: T1-L3

• Preganglionic sympathetic neurons for GVE (from ANS)

What makes up the intermediomedial cell column (IMM)? Give spinal levels.

• Spinal levels: S2-S4

• Preganglionic parasympathetic neurons for the GVA (from ANS)

Where can the long ascending fibers (sensory) be found?

All funiculi

Where are the long descending fibers (motor) found?

Lateral and anterior funiculi

Where can the shorter propriospinal fibers be found?

In a thin shell surrounding the grey matter called propriospinal tract.

What does proprioception mean?

Sensing stimuli arising within the body → position, motion, and equilibrium

What can spinal cord injuries result?

Loss of function (mobility + feeling)