Unit 1: Introduction to Neuroanatomy, Universidad Europea Presentation

Introduction to Neuroanatomy

Unit 1: Introduction to Neuroanatomy @ Copyright Universidad Europea. Todos los derechos reservados ue Universidad Europea 1Ue Universidad Europea

Index

• General organization of the Nervous System and anatomical terminology 03
• Neurons 10
• Planes, axes and neuroimaging 13
• Embryonic development of the CNS 23
• Questions 31

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General Organization of the Nervous System

01 General organization of the Nervous System and anatomical terminology

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Anatomical Division of the Nervous System

1. General organization of the Nervous System and anatomical terminology

Anatomically the nervous system is divided in:

1. Central Nervous System (CNS): . Brain: Located in the skull · Spinal cord: encircled by the vertebral column bones
2. Peripheral Nervous System (PNS): All the nervous tissue outside the CNS. This nervous tissue connects the CNS with the peripheral structures of the body. It includes nerves (cranial and spinal), ganglia, plexuses and sensory receptors.

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Brain Divisions

1. General organization of the Nervous System and anatomical terminology

The brain is located in the skull and is divided into:

Brain Telencephalon Diencephalon Mesencephalon Pons Medulla oblongata Cerebellum

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Spinal Cord Structure and Nerves

1. General organization of the Nervous System and anatomical terminology

The spinal cord starts rostrally in the foramen magnum as an extension of the medulla oblongata.

• It is a segmented structure with: · 8 cervical segments . 12 thoracic segments · 5 lumbar segments · 5 sacral segments · 1 coccygeal segments
• The spinal cord ends caudally with the cauda equina (horse tail) and the filum terminale.
• Spinal nerves serving the upper or lower limbs coalesce to form the brachial or lumbar plexuses respectively. A plexus, therefore, refers to a network of peripheral nerves. The fibres of these plexuses are redistributed into the peripheral nerves.

Base of skull Cervical nerves C3 Cervical enlargement TI 127 137 T2 Thoracic nerves T4 TS 17 18 19 T10 -118 T11 -m T12 T12 Comus medullaris L2 -U Cauda equina L4 3 Sacral/ coccygeal nerves Termination of dural sac 51 External filum terminale of dura mater LS

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Neuroanatomy Vocabulary: Grey and White Matter

1. General organization of the Nervous System and anatomical terminology

Neuroanatomy vocabulary:

Grey matter: CNS regions rich mainly in neuron cell bodies but also dendrites, unmyelinated axons and glial cells. For example, the central region of the spinal cord and the cerebral cortex.

White matter: is the pale part of the CNS. Its colour is due to the presence of axonic myelinated fibres.

White matter Grey matter

Coronal section of the brain Transversal section of the spinal cord

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Functional Divisions of the Nervous System

1. General organization of the Nervous System and anatomical terminology

Functionally the nervous system is divided into:

Somatic Nervous System (SNS): composed of neurons related to the detection of external environmental changes and the control of movement.

Autonomic Nervous System (ANS): refers to neurons that detect changes in and control the activity of involuntary structures and internal viscera (heart, smooth muscle, glands ... ). Together with the endocrine system, it maintains the body homeostasis. The ANS is divided into two anatomically and functionally distinct parts:

Sympathetic system: prepares our body for emergencies. Parasympathetic system: involved with energy maintenance.

Enteric System: involved in the gastrointestinal tract. Can be influenced £ by the Sympathetic and Parasympathetic system.

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Nervous System Overview

1. General organization of the Nervous System and anatomical terminology

Nervous System

Central Nervous System (CNS)

Peripheral Nervous System (PNS)

Somatic Nervous System

Autonomic Nervous System

Sympathetic system

Parasympathetic system

Enteric system

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Neurons

2100 Dendrites (@)123P 23RI Axon Presynaptic terminals Dendrites (0)123RF' (2)129/F® 02 Neurons

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Basic Neuron Types

• Unipolar: Has a small axon and doesn't have dendrites coming from the soma. Ej: Photoreceptive neurons.
• Bipolar: Has an unique dendrite and axon. Ej .: Photoreceptive neurons of the eye.
• Pseudounipolar: A cell that has a peripheric and central projection. The soma, sits besides the axon. Ej .: Sensitive afferences
• Multipolar: A big nucleus, loads of dendrites and a long axon. Ej .: In the nervous system.

(123RF® Basic Neuron Types Dendrites (0)123P 3RF® Axon Presynaptic terminals Dendrites (0) 123RF' 123/F

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Neuron Structure and Components

A neuron is the individual anatomical, physiological, genetic, and trophic unit of the nervous system.

• Oligodendrocyte vs. Schwann cells.
• Nodes of Ranvier.

(A) Apical dendrites Excitatory input terminal Node of Ranvier Inhibitory input terminal Presynaptic cell Basal dendrites Myelin sheath Cytoplasm Nucleus Cell body Axon hillock Axon (initial segment) Axon Oligodendrocyte (C) Synaptic vesicles Dendrite Neurotransmitter molecules Postsynaptic cell Neurotransmitter receptors Postsynaptic cells Synaptic cleft dad

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Planes, Axes and Neuroimaging

03 Planes, axes and neuroimaging

Lateral Medial Posterior Lateral Anterior Sagittal or median plane Coronal or frontal plane Rostral Caudal Superior Inferior Transverse, horizontal or axial plane

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Neuroanatomical Terminology and Planes

The neuroanatomical terminology aims at defining, placing and orienting each part of an organism.

Coronal Sagittal Horizontal

The localization or position of any anatomical structure is referred to three orthogonal planes: horizontal (also called transverse), sagittal (also called medium) and coronal (also called frontal).

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Magnetic Resonance Imaging (MRI)

• Principle: Uses magnetic fields and radio waves to create detailed images of brain structure.
• Advantages: High spatial resolution, non-invasive, no radiation.
• Applications: Diagnosis of tumours, structural abnormalities.
• Image: A detailed black-and-white image of the brain showing internal structures.

Functional Magnetic Resonance Imaging (fMRI)

• Principle: Measures changes in blood flow related to neuronal activity.
• Advantages: Good balance between temporal and spatial resolution, non- invasive.
• Applications: Studying brain activity during cognitive tasks.
• Image: Brain activity map with coloured areas indicating levels of activity

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Computed Axial Tomography (CT scan)

• Principle: Uses X-rays to create cross-sectional images of the brain.
• Advantages: Fast, effective for visualizing bones and acute injuries.
• Disadvantages: Exposure to radiation.
• Applications: Diagnosis of acute brain injuries, hemorrhages.
• Image: Cross-sectional image of the brain with good contrast between dense (bones) and soft tissues.

Positron Emission Tomography (PET)

• Principle: Uses radioisotopes to measure metabolic activity of the brain.
• Advantages: Provides precise functional information.
• Disadvantages: Invasive, exposure to radiation.
• Applications: Research on brain metabolism, neurodegenerative diseases.
• Image: Colorful image showing metabolic activity in the brain, with high activity areas highlighted in warm colors.

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Transverse Plane View

Transverse plane View B D left right right left A transverse section is also called a horizontal section

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Midsagittal Plane View

Midsagittal plane View Midsagittal section vs. parasagittal section. Paracentral sulcus (PCSul) uperior frontal gyrus (SFGy) Posterior paracentral gyrus (PP Marginal sulcus (MarSul) us callosum (BCorC) Precuneus (PCun) cus of the SulCorC)- Splenium of callosum (SE Gy)- -Parie sulcu 1- C of corpus 1 (RCorC)/ Fornix (For) Tectum Cerebellum Midbrain tegment Tonell of cerebellum (Ton) lad

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Frontal Plane View

Frontal plane 1 A coronal right left View A frontal section is also called a coronal section.

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Anatomical Directions and Axes

Superior Dorsal Anterior Posterior Rostral Caudal Rostral Dorsal Ventral Inferior Ventral Anterior (in front of) Caudal Rostral Midbrain- diencephalic junction Dorsal Posterior (behind) Ventral Dorsal Ventral Longitudinal axis of the brainstem and spinal cord Inferior (below) Caudal

@ Copyright Universidad Europea. Todos los derechos reservados Ue Universidad Europea 21 Caudal Superior (above) Longitudinal axis of the forebrain3. Planes, axes and neuroimaging

Summary of Planes and Relative Positions

) - Planes: - Sagittal - Coronal - Horizontal Relative positions: - Superior/Inferior - Medial/Lateral - Anterior/Posterior - Rostral/Caudal - Dorsal/Ventral

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Embryonic Development of the CNS

04 Embryonic development of the CNS

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Gastrulation and Embryonic Layers

A A Ectoderm Mesoderm Endoderm GASTRULATION fertilized egg

Gastrulation is the embryonic stage in which from a single layer of cells a three- layered embryo is formed:

1. Ectoderm: the outer layer (skin and nervous system)
2. Mesoderm: the middle layer (axial skeleton, muscles and connective tissue).
3. Endoderm: the inner layer (gastrointestinal, respiratory and urinary system).

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