Transcript 2. Nervous system anatomy

Nervous System Structure
The Nervous System
• Central Nervous System
(CNS)
• Peripheral Nervous System
(PNS)
Neuraxis
• The imaginary
line drawn
through the CNS,
from the base of
the spinal cord to
the front of the
brain.
Nervous system directions, in
relation to the neuraxis
• Anterior / Rostral
– Toward the nose
(rOstral  nOse)
• Dorsal
– Toward the back
• Superior
– Above
• Lateral
– Away from the midline
• Ipsilateral
– Same side
• Posterior / Caudal
– Toward the tail
(cAudal  tAil)
• Ventral
– Toward the belly
• Inferior
– Below
• Medial
– Toward the midline
• Contralateral
– Opposite side
Contralateral
Ipsilateral
Nervous system planes
• Transverse
– Cross section
• Sagittal
– Sagittal section
• Horizontal
– Horizontal section
Meninges
• Three protective
layers
surrounding the
brain and spinal
cord
Layers of the
meninges
– Dura Mater
– Arachnoid
membrane
– Pia mater
Dura mater
Arachnoid
membrane
Subarachnoid
space
Arachnoid
trabeculae
Pia mater
Brain
Ventricles
• Openings in the brain that contain
cerebrospinal fluid (CSF)
Cerebrospinal fluid
• CSF is made in the choroid plexus
• CSF flows through the ventricles into
the subarachnoid space, where it
surrounds the CNS.
Neural development
• Neural tube
– Develops into the CNS
• Neural tube forms 3
ventricles at the rostral
end
• Tissue surrounding
ventricles = ventricular
zone
Neural development
• Forebrain
– Telencephalon
– Diencephalon
• Midbrain (Mesencephalon)
– Tectum
– Tegmentum
• Hindbrain
– Metencephalon
– Myelencephalon
Cellular development
• Founder cells - in developing brain
– Initial cells in the ventricular zone
– Symmetrical division
• Increases size of the ventricular zone
– Asymmetrical division
• Creates neurons while maintaining ventricular
zone
• Stem cells - in the adult brain
Cellular development
• Radial glia
• Radial glia ensure development of systematic
pathways in the brain.
Cellular development
• Cortical development ends with
apoptosis
• Neurons grow into adult form with
dendrites, axons & terminal buttons
• Neurons that do not connect with other
neurons die
Forebrain - Telencephalon
• Telencephalon
– Cortex
– Limbic system
– Basal ganglia
Telencephalon
• Cerebral cortex – surrounds the cerebral
hemispheres
– Gyri (singular: Gyrus)
– Sulci (Sulcus)
– Fissures
• Cortex consists of densely packed glia and
neurons
• Four lobes of the brain
–
–
–
–
Frontal
Parietal
Temporal
Occipital
Cortex - Frontal lobe
• Prefrontal Cortex
– Involved in organization of thought, planning
actions, and higher cognitive functions.
Cortex - Frontal lobe
• Primary motor cortex
(PMC)
– Directly controls motor
output
– Somatotopic organization
• Motor Association
Cortex
– Involved in planning
movement
Cortex - Parietal lobe
• Primary Somatosensory Cortex
– Receives sensory information
– Somatotopic organization
• Somatosensory Association Cortex
– Somatosensory perception and memories
Cortex - Temporal lobe
• Primary Auditory Cortex
– Receives auditory input
• Auditory Association Cortex
– Analyzes auditory information
– Auditory perception and memory storage
Coretex - Occipital lobe
• Primary Visual Cortex
– Receives input from the visual system
– Input comes from the contralateral
visual field
• Visual Association Cortex
– Analyzes information received in the
PVC
– Involved in visual perception
Cortical connections
• Corpus Callosum – large bundle of
axons connecting corresponding
regions of each hemisphere
Telencephalon – Limbic system
• Limbic system
– Located within the telencephalon
– Includes:
•
•
•
•
Limbic cortex
Amygdala
Hippocampus
Mammillary bodies of the
hypothalamus
• Fornix
Limbic system
• Major role in emotion, learning and
memory
Telencephalon – Basal ganglia
• Basal ganglia
– Motivation and generation
of movement
• Include:
– Caudate nucleus
– Putamen
– Globus pallidus
Forebrain - Diencephalon
• Diencephalon
• Located between the
telencephalon and the midbrain
– Includes:
• Thalamus
• Hypothalamus
Diencephalon
• Thalamus
– Composed of nuclei that relay information to
the proper cortical regions
– Projection fibers
Diencephalon
• Hypothalamus
– Controls the autonomic nervous system
and the endocrine system
– Two major structures control endocrine
function
• Anterior pituitary gland
• Posterior pituitary gland
Midbrain (Mesencephalon)
• Structurally and evolutionarily between
the diencepalon and the hindbrain
• Only two major structures
– Tectum
– Tegmentum
Midbrain - Tectum
• Located on the dorsal
mesencephalon
– Superior colliculi
– Inferior colliculi
Midbrain - Tegmentum
• Located on the ventral
mesencephalon
– Reticular formation
– Periaqueductal grey area
– Red nucleus
– Substantia nigra
Hindbrain
• Most primitive brain structure; responsible
for basic survival functions
• Consists of the metencephalon and
myelencephalon
Hindbrain - Metencephalon
• Cerebellum (dorsal brainstem)
– Attached to the pons by the cerebellar
peduncles
– Coordinates movement
• Pons (ventral brainstem)
– Projects information from cortex to
cerebellum
– Role in sleep and arousal
Hindbrain - Myelencephalon
• Caudal-most region of the brain
– Contains the medulla oblongata
• Cardiovascular & respiratory functions, muscle
tone, arousal
Spinal cord
• Cells of the spinal cord
– Grey matter
• Cell bodies and unmyelinated axons
• Dorsal horns
• Ventral horns
– White matter
• Myelinated axons
web.lemoyne.edu/.../graphics/spinal_cord.jpg
Spinal cord
• Spinal nerves
– 31 pairs of spinal nerves attach to the spinal
cord
– Each spinal nerve consists of a motor efferent
(output) and a sensory afferent (input)
– As each nerve approaches the spinal cord, it
splits into a dorsal and ventral root
Spinal cord
• Dorsal root – carries the sensory axon
– Cell body is in the dorsal root ganglion
– Axon enters the spinal cord
• Ventral root – carries the
motor axon
– Cell body is in the ventral
horn of the spinal cord
– Axon exits to the periphery
Cranial nerves
• 12 pairs of cranial nerves attach to the
ventral surface of the brain.
– Sensory & motor functions of the face,
head, neck and throat.
Peripheral Nervous System
Somatic Nervous System
Autonomic Nervous System
Sensory input
Motor control
Sympathetic
Nervous System
Parasympathetic
Nervous System
“Fight or Flight” Response
“Rest & Digest” Response
Utilization of energy
resources
Conservation of energy
resources