chapter 7 the structure of the nervous system. introduction nervous system the structure of the...
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Chapter 7
THE STRUCTURE OF
THE NERVOUS SYSTEM
INTRODUCTION
Nervous System
The structure of the nervous system
will tell us about brain function
Brain organization
General organization and terms used to describe it
Examine how the 3D structure of the brain
arises through development
Cerebral neocortex
GROSS ORGANIZATION OF THE MAMMALIAN NERVOUS SYSTEM
Nervous System of all mammals has two divisions
CNS (central nervous system)
PNS (peripheral nervous system)
Anatomical References
GROSS ORGANIZATION OF THE MAMMALIAN NERVOUS SYSTEM
The Central Nervous System The parts of the nervous system that are encased in bone
Brain : Cerebrum, cerebellum, brain stem
Spinal cord
Relay information among
cerebrum, cerebellum, spinal cord
The site where vital functions are regulated
Breathing, consciousness, temperature
Contains as many neurons
as both cerebral hemispheres combined
Concerned with movements
of ipsilateral side of the body
Cerebral hemispheres,
separated by the deep sagittal fissure
Sensations and movements
on the contralateral side of the body
GROSS ORGANIZATION OF THE MAMMALIAN NERVOUS SYSTEM
The Central Nervous System
Spinal cord
Surrounded by bony vertebral column, attached to the brain stem
Conduit of information (brain body)
Skin, joints, muscles
Communication with body via the spinal nerves
Dorsal root : into the spinal cord
Ventral root : away from the spinal cord
GROSS ORGANIZATION OF THE MAMMALIAN NERVOUS SYSTEM
The Peripheral Nervous System
Nervous system outside of the brain and spinal cord
Somatic PNS Innervates skin, joints, muscles that are under voluntary control
Visceral PNS = autonomic nervous system (ANS) Innervates internal organs, blood vessels, glands
Afferent and Efferent Axons afferent : sensory axons bringing information into the CNS
efferent : axons that emerge from the CNS
GROSS ORGANIZATION OF THE MAMMALIAN NERVOUS SYSTEM
The Cranial Nerves 12 nerves from brain stem
Mostly innervate the head
Axons from CNS, somatic PNS, visceral PNS
The Meninges Three membranes that surround the brain Dura mater
Arachnoid membrane
Pia mater
Brain floats in cerebrospinal fluid (CSF)
GROSS ORGANIZATION OF THE MAMMALIAN NERVOUS SYSTEM
The Ventricular System CSF-filled caverns and canals inside brain
Choroid plexus : specialized tissue in ventricles that secretes CSF
Path : Cerebrum brain stem core subarachnoid space special structures called arachnoid villi absorb CSF
Imaging the Living Brain Computed Tomography (CT)
Magnetic Resonance Imaging (MRI)
Functional Brain Imaging Positron emission tomography (PET) Functional MRI (fMRI)
UNDERSTANDING CNS STRUCTURE THROUGH DEVELOPMENT
Ventricular System and the CNS
The entire CNS forms from the walls of a fluid-filled tube
The tube ultimately becomes ventricular system
Formation of the Neural Tube
The embryo begins as a flat disk with 3 distinct layers
Endoderm : the lining of many of the internal organs
Mesoderm : the bones of the skeleton and the muscles
Ectoderm : the nervous system – the neural plate
UNDERSTANDING CNS STRUCTURE THROUGH DEVELOPMENT
Formation of the Neural Tube Neural plate neural groove
Fusion of neural folds Neural tube (forms CNS neurons) Neural crest (forms PNS neurons)
Somites : vertebrae : skeletal muscle
Somatic motor nerves
Neurulation : the process which the neural plate becomes the neural tube
UNDERSTANDING CNS STRUCTURE THROUGH DEVELOPMENT
Three Primary Brain Vesicles
Differentiation : the process by which structures become more complex and functionally specialized during development
Primary vesicles : the entire brain derives from the three primary vesicles
UNDERSTANDING CNS STRUCTURE THROUGH DEVELOPMENT
Differentiation of the Forebrain
The secondary brain vesicles of the forebrain
UNDERSTANDING CNS STRUCTURE THROUGH DEVELOPMENT
Differentiation of the Forebrain
Differential of the Telencephalon and Diencephalon
Telencephalon
: cerebral hemispheres, olfactory bulbs, basal telencephalon
Diencephalon : thalamus, hypothalamus
Ventricles : lateral ventricles, third ventricle
Major white matter systems
: Axons extend from developing forebrain to other parts of the NS
Cortical white matter : cerebral cortex
Corpus callosum : two cerebral hemispheres
Internal capsule : brain stem, particularly the thalamus
UNDERSTANDING CNS STRUCTURE THROUGH DEVELOPMENT
Differentiation of the Forebrain
Forebrain Structure-Function Relationships
Cerebral cortex
: Analyze sensory input and command motor output
Thalamus
: Gateway of the cortex
: Carry information from contralateral side of the body
Hypothalamus
: Control of visceral (autonomic) nervous system
UNDERSTANDING CNS STRUCTURE THROUGH DEVELOPMENT
Differentiation of the Midbrain
UNDERSTANDING CNS STRUCTURE THROUGH DEVELOPMENT
Differentiation of the Midbrain
Midbrain Structure-Function Relationships
Information conduit from spinal cord to forebrain and vice versa
: Sensory systems, the control of movements… contralateral side
Tectum
Superior colliculus (216p)
: receives direct input from the eye, controls eye movements
Inferior colliculus : the ear instead of the eye
Tegmentum
: Substantia nigra (black substance), red nucleus
: Control of voluntary movement
UNDERSTANDING CNS STRUCTURE THROUGH DEVELOPMENT
Differentiation of the Hindbrain
Three structures
Cerebellum : Movement control
: Sensory systems, the control of movements
Pons : Switchboard connecting cerebral cortex to cerebellum
Medulla
Decussation : Crossing of axons from one side to the other
Neurons that perform many different sensory and motor function
UNDERSTANDING CNS STRUCTURE THROUGH DEVELOPMENT
Differentiation of the Spinal Cord
UNDERSTANDING CNS STRUCTURE THROUGH DEVELOPMENT
Putting the Pieces Together
UNDERSTANDING CNS STRUCTURE THROUGH DEVELOPMENT
Special Features of the Human CNS Many convolutions on the surface : Sulcus / Gyrus
The lobes of the human cerebrum
A GUIDE TO THE CEREBRAL CORTEX
Common Features of Cerebral Cortex Cell bodies in layers of sheets
Surface layer separated from pia mater
Apical dendrites form multiple branches
A GUIDE TO THE CEREBRAL CORTEX
Areas of Neocortex Brodmann construted a cytoarchitectural map : Cortical areas that look different perform different functions
A GUIDE TO THE CEREBRAL CORTEX
Areas of Neocortex
Neocortical Evolution and S-F Relationship
Cortex amount has changed, but not structure
Leah Krubitzer
: Primary sensory areas, secondary sensory areas, motor areas
Jon Kaas : Expansion of secondary sensory areas
Association areas
: ex) ability to interpret behavior in terms of mental state