Introduction To CNS Anatomy Flashcards
What is the main aim of the nervous system?
Enables the body to react continuously to changes in the internal and external environment
What are the 2 sub divisions of the nervous system?
CNS
PNS
What does the Central Nervous System (CNS) contain?
Brain
Spinal Cord
Retina
Optic nerve (CNII)
What does the Peripheral Nervous System (PNS) contain?
Spinal + cranial nerves (except optic nerve (CNII))
ANS (sympathetic + parasympathetic)
Somatic sensory + somatic motor nerves
What are the 2 main nervous tissue cell types?
Neurons (nerve cells)
Neuroglia (glial cells)
What are neurons? What is their function?
Structural + functional units of the NS including afferent/efferent neurons + interneurons
They have rapid communication across synapses via neurotransmitters
What are neuroglia? What is their function?
Non-neuronal/non-excitable cells that support, nourish + insulate neurons so they are 5x more abundant than neurons
What do the different structurally components of neurons do?
Dendrites: receptive projections sensitive to neural inputs
Cell body (soma): metabolic input
Axon: signal transmission
Axon terminal: passes signal onto other neurons + body tissues via synapses
What are the different types of neuroglia cells?
CNS: Oligodendrocytes Astrocytes Microglia Ependymal cells
PNS:
Satellite cells
Schwann cells
What do oligodendrocytes do?
Myelinate axons in the CNS and provide a structural framework
What do astrocytes do?
Maintain the BBB and help preserve the chemical environment by recycling ions and neurotransmitters in the environment itself
What do microglia do?
Help to remove debris, waste and pathogens via phagocytes so they are essentially a type of macrophage
What do ependymal cells do?
Line the ventricles/spaces in the brain or in the spine, mainly the central spinal canal
Help produce CSF
What do satellite cells do?
Help to regulate nutrient and neurotransmitter levels around the neurons and the ganglia
What do schwann cells do?
Myelinate axons in the PNS
What neurons are sensory afferents?
Somatic sensory: sensations from somatic tissue
Visceral sensory: sensations from organs
Special visceral sensory: e.g. taste
What are spinal nerves?
Mixed nerves containing motor + sensory neurons (some contain autonomic nerves)
What neurons are motor efferents?
Somatic motor: skeletal muscle
Branchio-motor: pharyngeal arch muscle
Visceral/autonomic motor: organs + vessels
How does the neural tube fold in embryology?
Neural ectoderm folds to form the neural tube by thickening, elevating + lifting away from the rest of the ectoderm approaching eachother at the midline, moving together + fusing
This occurs in the head to feet direction so the cranial neuropore closes at day 25 + the caudal neuropore closes at day 27
What can go wrong with the neural tube folding?
Failure of cranial neuropore closure = anecephaly (complete failure to form) or meroancephaly (herniation through the head)
Failure of caudal neuropore closure = spina bifida is most common - mild (incomplete neural arches of lumbar or sacral vertebra) or severe (malformations of meninges or spinal cord tissues)
What supplement prevents 70% of neural tube defects?
Folic acid
What does the brain look like at week 4 of development?
Primary brain vesicles x 3:
- Prosencephalon
- Mesencephalon
- Rhombencephalon
What does the brain look like at week 6 of development?
Secondary brain vesicles x 5:
- Telencephalon + diencephalon (from prosencephalon)
- Mesencephalon
- Metencephalon + myelencephalon (from rhombencephalon)
What do the 5 secondary brain vesicles go onto form in the adult brain?
Telencephalon: cerebral hemispheres
Diencephalon: thalamus/hypothalamus
Mesencephalon: midbrain
Metencephalon: cerebellum + pons
Myelencephalon: medulla