lesson 06: introduction to module 1 neuroanatomy

Module 1Lesson 06: Introduction to Neuroanatomy

Overview

1. Students will be able to identify the different types of brain sections and anatomical directions.2. Students will be able to distinguish between the different nervous system subdivisions.3. Students will be able to distinguish between white and gray matter in terms of function and composition.4. Students will be able to describe the gross anatomy of the brain and the function of its principal regions.5. Students will be able to describe the anatomy of the cerebral cortex.6. Students will be able to discuss the importance of anastomotic flow in brain vasculature.7. Students will be able to explain the structure and function of the ventricular system.8. Students will be able to describe the roles of physical and chemical barriers in protecting the brain.9. Students will be able to describe the gross anatomy of the spinal cord.

10. Students will be able to identify the principal functions of the cranial nerves.

2

Advanced Topics

A1. Students will be able to describe the cytoarchitecture of the cerebral cortex

1 Brain Sections and Directions

Common Sections of the Brain

Sagittal Horizontal Coronal

Dorsal/Ventral View of the Brain

Bear, Mark F. Neuroscience: Exploring the Brain

Lateral/Medial View of the Brain


2 Nervous System Subdivisions

Divisions of the Nervous System

● Central nervous system (CNS)○ Consists of the brain and spinal

cord○ Integrates sensory information○ Responds to sensory inputs

● Peripheral nervous system (PNS)○ Consists of the nerves and ganglia

outside of the brain and spinal cord○ Connects the CNS to the limbs and

organs.

The CNS & The PNS

Subdivisions of the PNS

● Somatic Nervous System:○ Controls voluntary

movement○ Movement of motor and

sensory information to and from the CNS

● Autonomic Nervous System:○ Controls involuntary

movement (e.g. heart rate, digestion, respiration)

○ Connects the brain and internal organs

● Parasympathetic system: ○ Controls regulatory functions

that conserving energy (e.g. slowing heart rate, relaxing muscles, etc.)

○ “Rest and digest”

● The sympathetic system: ○ Controls the body's rapid

involuntary response to dangerous or stressful situations

○ “Fight-or-flight”

The Sympathetic and Parasympathetic Nervous System

3 Gray and White Matter

● Nervous system contains two types of tissue: ○ Gray Matter (consists of

neuronal cell bodies) ○ White Matter (consists

of axons) ● In the brain, gray matter

surrounds white matter● In the spinal cord, white

matter surrounds gray matter

Tissue in the Nervous System

Classification of Matter

““

Multiple Sclerosis is an autoimmune disease in which

white blood cells destroy oligodendrocytes in the CNS.

Would you expect to see more damage in the gray or white

matter of an MS patient?

Discussion Question

Gross Anatomy of the Brain

4

● The brain can be divided into three subsections○ Brain Stem: Posterior part

of the brain (continuous with the spinal cord)

○ Cerebellum: Located in the back of the brain

○ Cerebrum: Largest portion; consists of two hemispheres

The Brain

● 3 major regions: ○ Medulla oblongata: Controls

autonomic functions (e.g breathing and digestion)

○ Pons: involved in breathing and communication between different brain regions

○ Midbrain: Plays an important role in communication and in the control of the motor system, vision and hearing, and the reflexes

Brain Stem

Brain Stem Structures


Cerebellum● Involved in motor control (coordination,

precision and timing of movements, motor learning)


● Largest and most developed portion of the brain

● Left and right hemispheres connected by a bundle of nerve fibers called Corpus Callosum

● Receives and processes visual, auditory, somatosensory, gustatory, and olfactory information.

● Each hemisphere consists of four lobes: frontal, parietal, temporal, and occipital

Cerebrum

Cerebral Structures


Cortical Anatomy

5

● The cerebrum is surrounded by the cerebral cortex

● Plays a large role in processing information and perception

● The cerebral cortex consists of folded bulges called gyri that create deep folds called sulci

● Sulci in the brain add to the surface area of the cortex○ Increases the amount of

information that can be processed

Cerebral Cortex

● Cortical areas can divided into○ Lobes ○ Functional areas○ Anatomical Areas

Cerebral Cortex

Lobes of the Brain Involved in cognition (e.g. personality, impulse control, social behavior, and problem solving


Involved in object recognition, hearing, and memory


Involved in visual perception




Involved in visual perception

Involved in sensation, perception, and integration of sensory information

Cortical Areas are Functionally Organized


● The primary motor cortex controls the instruction of movement

● The somatosensory cortex processes sensory information received from the body

● The auditory cortex processes sound information to determine intensity and frequency

● The visual cortex processes and relays visual information

Sensorimotor Regions


Speech Regions

● Broca’s area is located in the frontal lobe○ Plays a large role in

production of speech○ Located near the primary

motor cortex ● Wernicke's area is located in

the temporal region of the brain○ Plays a large role in speech

comprehension○ Located near the auditory

cortex

● Broca’s area is located in the frontal lobe○ Plays a large role in

production of speech○ Located near the primary

motor cortex ● Wernicke's area is located in

the temporal region of the brain○ Plays a large role in speech

comprehension○ Located near the auditory

cortex

Speech Regions

Brodmann Areas

● Korbinian Brodmann classified brain regions based on their cytoarchitecture (cell type composition)

● Cytoarchitectural classification closely correlated to function○ Motor areas (e.g. BA4, 6)

have more neurons which project to spinal cord


Cerebral Vasculature

6

Neurovasculature of the Brain

● The brain has its own system of circulation that is uniquely adapted to the brain’s metabolic demands○ Brain represents 2% of body

mass, but consumes 20% of oxygen

● Neurons die after minutes without oxygen

Neurovasculature: structure of nerves and blood vessels of a body part

““

How might brain vasculature be different from systemic

vasculature?

44

Discussion Question

Efficient Blood Flow in the Brain

Anastomosis: connection between two things (in this case, blood vessels)

● Blood vessels connect to allow alternative routes of blood flow○ Vasculature is redundant

● Prevents brain regions from losing blood supply if one region is damaged

● Blood flow to brain regions is dependent on regional activity

● Circle of Willis: The “central station” where many different train tracks meet

● Located underneath the brain where the brainstem and cerebellum reside

● First part of neurovasculature to receive oxygenated blood.

● Connects the anterior and posterior circulation of the brain into one system that stems from the aorta

Neurovasculature

Ventricular System7

Ventricles ● Structures in the brain carry

specialized fluid for “cleansing” the brain

● Four ventricles carry fluid in the brain

● First and second (lateral ventricles) are located deep in the cerebrum

● Third ventricle lies in the center of the brain

● Third ventricle connects to the fourth ventricle via the cerebral aqueduct


Cerebrospinal Fluid (CSF) ● Cerebrospinal fluid (CSF) is a

clear fluid surrounding the brain

● Located in the ventricles and surrounding the brain and subarachnoid space

● Brings nutrients to the brain and removes toxins from the CNS

● Produced by the choroid plexus

Pathway of CSF Flow

Protective Barriers Around the Brain

8

● Serves as a protective barrier for the brain

● Especially thick at the brainstem to protect life preserving functions

● The skull has a hole in the bottom through which the spinal cord passes (foramen magnum)

The Skull

““

Is the skull alone sufficient to protect the brain from damage

after injuries?

53

Discussion Question

● Three membranes (meninges) enclose the brain and spinal cord

● They protect the central nervous system

● Dura mater: thin and durable “cap” for the brain ○ Fixes the brain with respect

to the skull ● Arachnoid layer: contains fibrous

tissue to cushion the brain ● Pia mater: thin membrane

containing capillaries that supply the brain with nutrients

Meninges

http://www.youtube.com/watch?v=UkffBv4sh4U

Blood Brain Barrier● The brain’s blood vessels are lined

with endothelial cells○ Serve as an interface between

circulating blood and the vessel wall

● Endothelial cells in the brain are tightly wedged together, creating an impermeable boundary between the brain and bloodstream

● The blood-brain barrier helps block harmful substances from entering the brain

How the Blood Brain Barrier Functions

● Endothelial cells are structurally tightly wedged together unlike vasculature in other regions

● Endothelial cells, astrocytes, and pericytes work together to create a functional barrier to most solutes

● Not all brain regions are surrounded by a blood brain barrier

http://www.youtube.com/watch?v=e9sN9gOEdG4

Gross Anatomy of the Spinal Cord

8

Spinal Cord● The spinal cord is a long structure

that extends from the brainstem through the vertebral column

● Composed of nervous tissue● Provides a pathway to and from

the brain, and is a major reflex center

● Consists of four parts: cervical, thoracic, lumbar, and sacral sections

● Spinal nerves exit the spine through each vertebrae

Anatomy of the Spinal Cord● Contains a dorsal and ventral

component● Nerves exit each side forming

dorsal and ventral roots● Roots combine to form ganglia

(dorsal root ganglia and ventral root ganglia)

● Ventral roots carry motor information from the brain to the body

● Dorsal roots carry sensory information to the brain from the body


The Cranial Nerves9

● Cranial nerves stem directly from the brain rather than from the spinal cord

● The 12 cranial nerves have a variety of important sensory and motor functions○ Vision, taste, audition, touch

etc. ● Sensory neurons collect

information and carry it to the central nervous system via cranial nerves

Cranial Nerves

Cranial Nerves

Cytoarchitecture of the Cerebral Cortex

A1

Overview of the Cerebral Cortex

● A sheet of gray matter that covers the cerebrum

● Mostly neocortex, but some are allocortex

● Neocortex has 6 layers with different neuronal characteristics

● Major types of cells found:1. Pyramidal Cell2. Fusiform Cell3. Stellate Cell

Supragranular Layers(I-III)Responsible for intracortical connections. Afferent fiber bundles allow communication between different regions of the cortex, even with areas within the other hemisphere. It is highly developed in human brain.

Layer I: Molecular Layer

Layer II: External Granular Layer

Layer III: External Pyramidal Layer

● Few neurons observed● Transverse fibers from other cortical regions and

nonspecific thalamocortical fibers are located

● Small stellate cells are densely packed

● Consists of small to medium sized pyramidal cells● The axons of the pyramidal cells spread out both

association and commissural fibers to other cortical regions

THALAMUS

Other Regions

Internal Granular Layer(IV)Serves as the primary input layer. It receives signals from the specific thalamic nuclei.

Layer IV: Internal Granular Layer

● Small stellate cells are densely packed● Specific thalamocortical fibers are prominent● Outer band of Baillarger* is found

*Outer band of Baillarger indicates the transverse fibers of thalamocortical axon terminals

THALAMUS

Infragranular Layers(V-VI)Connect the cortex to subcortical regions by efferent fiber bundles. Mainly developed in motor cortical areas. It can be seen in most mammalian brain

Layer V: Internal Pyramidal Layer

Layer VI: Multiform Layer

● Betz cells (large pyramidal cells) are observed● Betz cells spread projection fibers to subcortical regions

and project apical dendrites up to layer I● Serves as the primary output layer● Internal band of Baillarger** is found

● Contains fusiform cells and variety of other cells that merge with white matter

**Internal band of Baillarger is thought to be the aggregate of associate fiber terminals from other cortices and axon branches of pyramidal cells in layer V

Subcortical Regions

THALAMUS

lesson 06: introduction to module 1 neuroanatomy

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