Nervous systems

Question 1

Anatomical components of central and peripheral nervous systems

Answer 1

Central Nervous System (CNS)
-Brain and spinal cord
-Located in the cranial cavity and spinal canal

Peripheral Nervous System (PNS)
-Nerve fibres (cranial and spinal nerves) and ganglia outside of the CNS

Question 2

Classification of nervous system

Answer 2

Question 3

Structure of the brain

Answer 3

Question 4

Nuclei, ganglia, grey matter, white matter definition

Answer 4

Nuclei - Collections of cell bodies in the CNS
Ganglia - Collections of cell bodies outside the CNS
Grey matter - Collection of nerve cell bodies
White matter - Axons with a glial sheath (myelin)

Question 5

Grey and white matter in the brain and spinal cord

Answer 5

Brain:
-Grey matter outside
-White matter inside

Spinal cord:
-White matter outside
-Grey matter inside

Question 5

What are the 2 different types of nerves?

Answer 5

Cranial nerves - 12 pairs that exit the cranial cavity through foramina in the cranium

Spinal nerves - 31 pairs arising from a specific segment of spinal cord and exiting the vertebral column through intervertebral foramina

Question 6

What are nerve rootlets?

Answer 6

-Connect the CNS and the PNS and are groups of axons
-Exit the ventral aspect of the spinal cord (axons of motor neurones)
-Enter the dorsal aspect of the spinal cord (axons of sensory neurones)

Question 7

What is the cauda equina?

Answer 7

-Group of nerves and nerve roots at the end of the spinal cord
-Cauda equina follows the conus medullaris

Question 8

Dermatome definition

Answer 8

-Area of skin supplied by a single spinal nerve

Question 9

Myotome definition

Answer 9

-Group of muscles supplied by a single spinal nerve

Question 10

What does spinal nerve divide into?

Answer 10

Dorsal ramus
-Supply nerve fibres to the back (joints of the vertebral column, muscles of the back and the overlying skin)

Ventral ramus
-Supply nerve fibres to skin and muscles of the anterior and lateral regions of the trunk, lower and upper limbs

-At certain levels, ventral rami merge to form nerve plexuses (e.g. brachial/lumbosacral plexuses)

Question 11

Features of cranial nerves

Answer 11

-12 pairs numbered 1-12
-Their numerical order is from rostral to caudal direction
-All originate from brainstem except I and II

Question 12

Which cranial nerves are parasympathetic?

Answer 12

-Oculomotor
-Facial
-Glossopharyngeal
-Vagus

Question 13

General functions of cranial nerves

Answer 13

Question 14

Nerve fibres vs nerves

Answer 14

-Nerve fibres are the neurones
-Nerves are bodies which branch into nerve fibres

Question 15

What are the types of nerve fibres

Answer 15

Somatic fibres
-General somatic afferent (GSA) fibres =>sensations from the skin or pain and proprioceptive sensations from muscles, tendons and joints
-General somatic efferent (GSE) fibres
=>transmit impulses to skeletal muscles

Visceral fibres
-General visceral afferent (GVA) fibres
=>transmit pain or subconscious visceral reflex sensations (blood gas/pressure) from hollow organs and blood vessels to CNS
-General visceral efferent (GVE) fibres - transmit impulses to smooth muscle and glandular tissues

Question 16

3 types of special cranial nerves

Answer 16

Special somatic afferents - transmit impulses of special senses (e.g retina/vestibular apparatus)

Special visceral afferents - transmit impulses from taste buds of tongue/olfactory mucosa

Special visceral efferents - transmit impulses to skeletal muscled derived from the branchial arches

Question 17

What is the autonomic nervous system?

Answer 17

-Visceral efferent part of the nervous system
-Sympathetic system for excitatory processes
-Parasympathetic system for rest and digest

Question 18

Division of ANS into Sympathetic and Parasympathetic

Answer 18

Sympathetic:
-Shorter preganglionic neurone
-Longer postganglionic neurone

Parasympathetic:
-Longer preganglionic neurones
-Shorter postganglionic neurones

Preganglionic neurones:
-Cell bodies located in CNS grey matter
-Synapse with postganglionic neurones

Postganglionic neurones:
-Cell bodies located outside CNS in autonomic ganglia
-Axons terminate on effector organs

Question 19

Sympathetic and parasympathetic cell body locations

Answer 19

Sympathetic
-Preganglionic neurones are located in the lateral horn of grey matter of the the spinal cord level T1-L2/3
-Postganglionic neurones are located in either paravertebral or prevertebral ganglia

Parasympathetic
-Pregnaglionic neurones are located in cranial nerves III,VII,IX,X and the lateralhorn of grey matter of the spinal cord S2-4
-Post ganglionic neurones are located close to their effector organs

Question 20

How do preganglionic neurones leave to the sympathetic ganglion?

Answer 20

-Preganglionic neurones leave the ventral ramus and pass to sympathetic ganglion through white ramis communications (white communicating rami)

Question 21

How do postganglionic neurones return to spinal nerves?

Answer 21

-Postganglionic neurones following course 1-3 return to spinal nerves via grey rami communications (grey communicating rami)

Question 22

Within the sympathetic chain, what 4 courses can preganglionic fibres follow?

Answer 22

-Ascend then synapse at the ganglion
-Descend then synapse at the ganglion
-Synapse at the ganglion at the level of entry
-Pass through the sympathetic chain without synapsing, continue to reach a prevertebral ganglion via the splanchnic nerves