The Structure of the Nervous System. Divisions of the Nervous System.
Structure of the Nervous System
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Transcript of Structure of the Nervous System
Structure of the Nervous SystemCHAPTER 3
Directions in the Nervous SystemDirections in the Nervous System
Anterior/Rostral = Front Posterior/Caudal = Back Dorsal = Top Ventral = Bottom Lateral = Toward the side Medial = Toward the midline Ipsilateral= Same side Contralateral= Opposite side
Fig. 3.1Fig. 3.1
Coronal Coronal *Cross Section or *Frontal SectionTransverse section at right angles to the neuraxis.
Brain Slices and PlanesBrain Slices and Planes
CoronalCoronal
Fig. 3.2Fig. 3.2
Sagittal Section• Section parallel to neuraxis and perpendicular to the ground.• Midsagittal Plane – special type of sagittal section through the corpus callosum separating the hemispheres.
Brain Slices and PlanesBrain Slices and Planes
SagittalSagittal
Fig. 3.2Fig. 3.2
Horizontal SectionHorizontal SectionSection made through the brain parallel to the ground.
Brain Slices and PlanesBrain Slices and Planes
HorizontalHorizontalFig. 3.2Fig. 3.2
MeningesThe MENINGES MeningesMeninges
Dura Mater – tough, flexible outermost layer.
Arachnoid Membrane – middle layer of the meninges. Subarachnoid Space – space
between arachnoid membrane and pia mater filled with CSF.
Pia Mater – last layer of the meninges, which adheres to the surface of the brain.
The Ventricular System CSF surround the brain (protection) Four ventricles (lateral-2, third and fourth connected by cerebral
aqueduct) Choroid plexus- produces CSF (125 ml/day) Arachnoid granulations: absorb CSF
Figure 3.4Figure 3.4
Obstructive hydrocephalus
Figure 3.6Figure 3.6
Development of the CNS Begins around
18th day after conception
A patch of tissue on the dorsal surface of the embryo becomes the neural plate
Development of the CNS
Figure 3.7Figure 3.7
Neural plate folds to form the neural groove
Development of the CNS The neural groove then
fuses to form the neural tube…
Walls of the neural tube become the CNS
Neural crest becomes the PNS
Figure 3.7Figure 3.7
Brain Development
Figure 3.8Figure 3.8
Early and later development of the human nervous system
Cellular Development
Totipotent – earliest cells have the ability to become any type of body cell Stem cells
Multipotent – with development, neural plate cells are limited to becoming one of the range of mature nervous system cells Progenitor cells
Migration of Neurons Once cells have been created through cell division in
the ventricular zone of the neural tube, they migrate Migrating cells are immature, lacking axons and
dendrites Inside-out migration
Progenitor cells have limited capacity to replicate
First Step: Symmetrical Division Progenitor -> progenitor Increases the size of the ventricular zone
Figure 3.10Figure 3.10
Second: Asymmetrical Division
Asymmetrical division (7 weeks after conception) First produces radial glia Cell bodies of RG in the VZ and processes extend to
the pia Guide the migration of new neurons (neurogenesis) Ends after 3 months
•development where a progenitor cell divides into one progenitor cell and one brain cell
Cellular Development and Migration
Cajal-Retzius cells Develop after radial
glia Migrate to just inside
the pia (Layer 1) Orderly migration:
Build on each successive layer
All end up below C-R
Anatomical Subdivisions
Anatomy BasicsMajor Division Ventricle Subdivision Principle Structures
Midbrain
Hindbrain
Forebrain
Lateral
Third
Telencephalon
Diencephalon
Cerebral cortexBasal gangliaLimbic System
Cerebralaqueduct Mesencephalon
Metencephalon
TectumTegmentum
FourthCerebellum
PonsMyelencephalon
ThalamusHypothalamus
Medulla oblongata
The Forebrain
Largest section of the brain, comprised of the:
Telencephalon Cerebral hemispheres
Cerebral Cortex Limbic System Basal Ganglia
Diencephalon Thalamus Hypothalamus Figure 3.8Figure 3.8
The Forebrain
Telencephalon – contains most of the cerebrum.
1. Cerebral Cortex – thin, wrinkled layer of tissue covering the brain consisting of sulci (groove), fissures (big groove), and gyri (convolution). Frontal Lobe Parietal Lobe Temporal Lobe Occipital Lobe
Figure 3.8Figure 3.8
Figure 3.16Figure 3.16
The Forebrain
Telencephalon Primary cortices
Visual cortex Auditory cortex Somatosensory cortex Motor cortex
Association cortices Associated with all
primary cortices
Figure 3.16Figure 3.16
Figure 3.15Figure 3.15
Figure 3.16Figure 3.16
Limbic System
2. Limbic System – set of structures involved in learning, memory, and emotion. Major structures of the limbic system include: Limbic Cortex (cingulate!) Hippocampus Amygdala Fornix Mammillary Bodies (part of
the hypothalamus)Figure 3.19Figure 3.19
Basal Ganglia3. Basal Ganglia – set of
structures involved in processing information for motor movement. Major structures of the basal ganglia motor system include: Caudate Nucleus Putamen Globus Pallidus
Figure 3.20Figure 3.20
Forebrain: The Diencephalon
Thalamus and hypothalamus
ThalamusThalamus: Dorsal diencephalon Two lobes connected by
the massa intermedia Many nuclei
LGN MGN Cerebellum->VLN->
motorFigure 3.8Figure 3.8
Forebrain: The Diencephalon
Figure 3.21Figure 3.21
Hypothalamus Below thalamus Many nuclei Many diverse
behaviours Endocrine- Pituitary
Hypothalamus regulates the autonomic nervous system, controlling the pituitary gland, and integrating species-typical behaviors.
Hypothalamic Portal System Endocrine system
Hormones are secreted from the hypothalamus through the venous portal system to anterior pituitary
These stimulate hormone release from AP Can control other glands or the hormones are the messengers AP- ‘master gland’
Gonadotropin-releasing hormone causes the anterior pituitary gland to secrete gonadotropic hormones, which play a role in reproductive physiology and behavior
Hypothalamus also releases hormones in the posterior pituitary
oxytocin - stimulates milk ejection and uterine contractions during childbirth Vasopressin - regulates urine output by the kidneys
The Midbrain
Figure 3.8Figure 3.8
Also known as the mesencephalon and is comprised of the tectum and tegmentum.
Tectum (roof) – contains the superior (vision) and inferior (auditory) colliculi (singular is colliculus).
Tegmentum (floor) – contains the periaqueductal gray matter, reticular formation, red nucleus, and substantia nigra all of which share a role in motor movement.
Figure 3.23c and dFigure 3.23c and d
The Hindbrain The Hindbrain
Contains both the metencephalon and the myelencephalon.
Figure 3.8Figure 3.8
The Hindbrain
Metencephalon – a structure comprised of the cerebellum and the pons.
Cerebellum – appears as a mini brain and is involved in motor coordination.
Pons – contains part of the reticular formation and is involved in sleep and arousal.
Figure 3.23Figure 3.23
The Hindbrain
Myelencephalon – contains the medulla oblongata containing portions of the reticular formation
Is involved in basic life functions, such as respiration and regulation of the cardiovascular system. Figure 3.23Figure 3.23
The Central Nervous System
The Spinal Cord Function: distribute
motor fibers to the effector organs of the body (glands and muscles) and to collect somatosensory information to be passed on to the brain
Protected by the vertebral column Composed of 24
individual vertebrae
Primary Components of the Spinal Cord
Spinal Roots – a bundle of axons surrounded by connective tissue that occur in pairs, which fuse and form a spinal nerve
Dorsal Roots – the spinal roots that contain incoming (afferent) sensory fibers
Ventral Roots - the spinal roots that contain outgoing (efferent) motor fibers
The Peripheral Nervous System
Somatic Nervous System Portion of the PNS comprised of the spinal nerves
and cranial nerves involved in transmitting sensory information and controlling voluntary movement. Spinal Nerves
Peripheral nerves attached to the spinal cord. Cranial Nerves
Set of 12 motor and/or sensory nerves attached to the ventral surface of the brain.
The Autonomic Nervous System Portion of the PNS concerned with the regulation of
smooth muscle, cardiac muscle, and glands
The Autonomic Nervous System Sympathetic Division of the
ANS Nervous system components
involved in arousal and preparing the body for the expenditure of energy.
‘Fight or flight’ Parasympathetic Division of
the ANS Nervous system components
involved in relaxing the body, often competing with those of the sympathetic division.
‘rest and digest’