Nervous systems Flashcards
Anatomical components of central and peripheral nervous systems
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
Classification of nervous system
Structure of the brain
Nuclei, ganglia, grey matter, white matter definition
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)
Grey and white matter in the brain and spinal cord
Brain:
-Grey matter outside
-White matter inside
Spinal cord:
-White matter outside
-Grey matter inside
What are the 2 different types of nerves?
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
What are nerve rootlets?
-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)
What is the cauda equina?
-Group of nerves and nerve roots at the end of the spinal cord
-Cauda equina follows the conus medullaris
Dermatome definition
-Area of skin supplied by a single spinal nerve
Myotome definition
-Group of muscles supplied by a single spinal nerve
What does spinal nerve divide into?
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)
Features of cranial nerves
-12 pairs numbered 1-12
-Their numerical order is from rostral to caudal direction
-All originate from brainstem except I and II
Which cranial nerves are parasympathetic?
-Oculomotor
-Facial
-Glossopharyngeal
-Vagus
General functions of cranial nerves
Nerve fibres vs nerves
-Nerve fibres are the neurones
-Nerves are bodies which branch into nerve fibres
What are the types of nerve fibres
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
3 types of special cranial nerves
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
What is the autonomic nervous system?
-Visceral efferent part of the nervous system
-Sympathetic system for excitatory processes
-Parasympathetic system for rest and digest
Division of ANS into Sympathetic and Parasympathetic
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
Sympathetic and parasympathetic cell body locations
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
How do preganglionic neurones leave to the sympathetic ganglion?
-Preganglionic neurones leave the ventral ramus and pass to sympathetic ganglion through white ramis communications (white communicating rami)
How do postganglionic neurones return to spinal nerves?
-Postganglionic neurones following course 1-3 return to spinal nerves via grey rami communications (grey communicating rami)
Within the sympathetic chain, what 4 courses can preganglionic fibres follow?
-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
