CHAPTER 3 Structure of 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. 3.1

Coronal
Fig. 3.2
Brain Slices and Planes
Coronal *Cross Section or *Frontal Section
Transverse section at right angles to the neuraxis.

Sagittal
Fig. 3.2
Brain Slices and Planes
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.

Horizontal
Fig. 3.2
Brain Slices and Planes
Horizontal Section
Section made through the brain parallel to the ground.

The MENINGES 
Meninges
 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.


Figure 3.6
Obstructive hydrocephalus
Figure 3.4




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


Begins around 18 th day after conception

A patch of tissue on the dorsal surface of the embryo becomes the neural plate

Neural plate folds to form the neural groove
Figure 3.7


The neural groove then fuses to form the neural tube…

Walls of the neural tube become the CNS

Neural crest becomes the
PNS
Figure 3.7

Figure 3.8
Brain Development

Early and later development of the human nervous system


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


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 3.10

•development where a progenitor cell divides into one progenitor cell and one brain cell

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



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

Major Division Ventricle Subdivision Principle Structures
Forebrain
Lateral
Third
Telencephalon
Diencephalon
Cerebral cortex
Basal ganglia
Limbic System
Thalamus
Hypothalamus
Midbrain
Cerebral aqueduct
Mesencephalon
Tectum
Tegmentum
Hindbrain
Fourth Metencephalon
Myelencephalon
Cerebellum
Pons
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 3.8

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 3.8
Figure 3.16

The Forebrain

Telencephalon

Primary cortices



Visual cortex
Auditory cortex
Somatosensory cortex

Motor cortex
Figure 3.15

Association cortices

Associated with all primary cortices
Figure 3.16
Figure 3.16

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 3.19

3.
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 3.20

Forebrain: The Diencephalon

Thalamus and hypothalamus

Thalamus :
 Dorsal diencephalon
 Two lobes connected by the massa intermedia
 Many nuclei
 LGN
 MGN
 Cerebellum->VLN-> motor
Figure 3.8

Forebrain: The Diencephalon
Hypothalamus




Below thalamus
Many nuclei
Many diverse behaviours
Endocrine- Pituitary
Figure 3.21
Hypothalamus regulates the autonomic nervous system, controlling the pituitary gland, and integrating species-typical behaviors.


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

 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 3.8
Figure 3.23c and d


 Contains both the metencephalon and the myelencephalon .
Figure 3.8

 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 3.23

 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 3.23



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


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


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


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’