Neuroanatomy and Nervous System Function

Ancient Neurosurgery

• Trephination/trepanning involves making holes in the skull, a practice that is not common now.
• Reason to do this now includes brain swelling.
• This process is now called a craniectomy.

Where Does Behavior Originate?

• Cardiac and brain hypotheses offer potential sources.
• Aristotle suggested it was cardiac.
• Brain: Hippocrates and Galen.

Levels of Analysis

• Behavioral/Action Level: Observable to outsiders and insiders (examples - walking, playing piano).
• Structural Levels: Macroscopic (anatomical structures) and Microscopic (layers, cells), Chemical structures.
• Functional Levels: Macroscopic (blood flow) and Physiological/chemical processes within and between cells, Physical/chemical principles (ionic forces).

How Does Behavior Originate?

• The humor and ventricular theories offer potential explanations.

What is The Structure of The Brain?

• Galen dissected pigs and other animals.
• Vesalius challenged Galen, stole corpses, and fought to cut up executed criminals; was interested in the entire body; used to not be allowed to cut up dead bodies.

Where's the Mind?

• Descartes: mind is immaterial, the brain is material. -Problems exist W/ causality (how does mind cause body to move?).
• Materialism suggests that all that exists is physical, so there is no mind.
• Monism suggests that the mind and brain are identical.
• Dual aspect theory provides that two views exist on the same thing: mind is experience from "inside," and brain is "outside."

Where In The Structure is The Function?

• Localization of function has evidence from researchers like Franz Joseph Gall (1758-1828) and Johann Casper Spurzheim.
• Phrenology, a pseudoscience.
• Equipotentiality and mass action suggested by Pierre Flourens and Karl Lashley.
• Other parts of the brain can take over.

Hierarchy of Organization

• John Hughlings-Jackson: need lower levels to function in for higher levels to work.
• The nervous system is hierarchical, moving from:
• Brain stem
• Temporal/other
• Frontal lobe
• Alexander Romanovich Luria described a synthesis of localization of function.
• Combining plasticity with localization of function with the higherarchy of organization.

Afferent and Efferent Nerves

• Afferent nerves travel toward the brain and provide sensory input.
• Efferent nerves travel away from the brain and control movement.

Terminology Directions (Created for 4 Legged Animals)

• Dorsum = back → dorsal
• Venter = Stomach → ventral
• Cauda = tail → caudal
• Rostrum = snout/beak → rostral
• Anterior = in front
• Posterior = behind
• Superior = above/upper
• Inferior = below/lower
• Lateral = to the side
• Medial = to the middle

Cells Neurons

• There are ~86 billion neurons.
• Each has an average of 7 connections or 700 synapses.
• In the cortex, there is an average of 38,000 synapses. Processes are things coming from the cell body.
• Information transmission within the cell is electric; between neurons, it is chemical.
• Neurons come in all shapes.

Glial Cells

• Surrounding glial cells include:
• Microglia
• Macroglia
• Oligodendrocytes (central nervous system)
• Schwann cells
• Astrocytes (largest in number, star-shaped).
• Ependymal cells
• Speed in the brain:
• Unmyelinated axons 400 vs 100 ft/s
• Myelinated axons 120 vs 30 ft/s

Myelin

• A layer of fat wrapped around the axon.
• Oligodendrocytes and Schwann cells create Myelin
• Schwann cells: responsible for myelination in the peripheral nervous system

Myelinated Axons

• Myelinated axons are faster.
• Neuron bodies and axons: white matter (mostly axons) and gray matter (mostly cell bodies).

Multiple Sclerosis

• The mechanism involves myelin breaking down (demyelination).
  • Proximal cause: immune system attacking oligodendrocytes (autoimmune).
• Distal cause: genetic susceptibility and environmental trigger.
• Symptoms: Sensory, motor, cognitive, emotional.

MS Details

• MS typically starts ages 20-40.
• It is more common for women.
• It has various forms of progression (attacks, remission).
• It gets worse over time.
• 1 in 2000 in the United States.
• Latitude vs. ethnicity (more north you go, the more common it is; lack of sun).
• Treatments aim to elongate time between attacks.
• Attacks last on average 4-8 weeks.

Basic Processes

• Basic brain processes include:
• Neurogenesis & migration (mostly prebirth)
• Formation of new neurons
• Synaptogenesis: forming connections between neurons
• Myelination
• Synaptic pruning
• Synaptic pruning gets rid of synapses for efficient info transmission .

Three Germ Layers

• Three essential germ layers:
• Ectoderm: nervous tissue and epidermis
• Mesoderm
• Endoderm

Nonclosure

Nonclosure includes:

• Neuropore closing
  • Day 24-28
• Anencephaly
• Spina bifida

Lissencephaly

• Due to defective neuronal migration.
• Is genetic, viral, and from hypoxia during first trimester.

Microcephaly

• Descriptive: small head circumference.
• Pre/post natal causes.
• Rare.
• In the news because of the Zika virus.

7 Central Nervous Parts (CNS)

• Frontal, Parietal, Temporal and Occipital lobes.
• Corpus Callosum
• Cerebellum

Phylogenetics

The Divisions of the Brain

• Brain composed of the forebrain, midbrain and hindbrain.
  • The forebrain subdivided into the telencephalon and diencephalon
• The hindbrain subdivided into the metencephalon and myelencephalon

The Meninges

• A series of membranes protects the CNS.
• Dura mater: outer layer.
• Arachnoid: middle layer
  Overlies the subarachnoid space & Contains blood vessels.
• Pia mater: inner layer Overlies every detail of the outer brain

Additional Meninges Facts

• Dura mater
• Arachnoid
• Pia mater
• Subarachnoid cavity with CSF circulating
• Trabeculae

Cerebrospinal Fluid

Contained within 4 brain ventricles.

• CSF build up can result in hydrocephalus Produced by the choroid plexus of the ventricles (ependymal cells). Functions of CSF are numerous.

Dural Folds

• Dural folds "divide" the brain into hemispheres; separates cerebrum and cerebellum.

Cerebral Blood Supply

• Study of the Circle of Willis required.

Circle of Willis Variants

• Numerous variations.

Major Arterial Supply of Principal Structures

• Frontal lobe:
  • Lateral surface: Middle cerebral artery.
  • Medial surface: Anterior cerebral artery.
  • Inferior surface: Middle and anterior cerebral arteries.
• Temporal lobe:
  • Lateral surface: Middle cerebral artery.
  • Medial surface: Middle and posterior cerebral arteries.
  • Inferior surface: Posterior cerebral artery.

Blood Supply To Structures (Cont.)

• Parietal lobe:
  • Lateral surface: Middle cerebral artery.
  • Medial surface: Anterior cerebral artery.
• Occipital lobe: all surfaces
  • Posterior cerebral artery.

Middle Cerebral Arteries

Venous Returns

Blood-Brain Barrier (BBB)

• Endothelial cells of brain capillaries have tight junctions.
• Astrocyte feet cover endothelial cells. Small uncharged molecules can pass. Other molecules get across w/ active transport.

Absent BBB

• Absent BBB in circumventricular organs. -3rd ventricle, SFO, and OVLT.
• 4th ventricle - area postrema..

Spinal Cord

Shows major areas of the spinal cord.

Vertebra

Diagram of key parts of a vertebra.

Spinal Cord

• Spinal cord dermatomes are body segments innervated by spinal nerves.

Lumbar Puncture

• Area numbed by local anesthetic; a small needle is passed between vertebrae and posterior to the end of the spinal cord, which carries no risk of paralysis.

Anatomy of Motor Neuron

Diagram of key parts of a motor neuron within the peripheral nervous system.

Sensory Neuron Details

-Spinal cord damage level and extent. -Main-car bike accident:38%, falls: 25%, sports: 13%, violence: 10 % Christopher Reeves: at C1-C2. Paraplegic: Loss of control over lower limbs.

• Quadriplegic/ Tetraplegic: loss of control over all limbs.

Key Features of Vertebrae

• The medulla is located just above the spinal cord and could be regarded as an enlarged extension of the spinal cord.
• Several tracts cross (decussate)
• Responsible for vital reflexes (breathing, heart rate, vomiting, salivation, coughing, sneezing).
  • Diagram of medulla. Cranial nerves are functionally homologous to the spinal nerves: provide both somatic and visceral sensory and motor innervation of the head and neck, traditionally numbered I through XII in rostrocaudal sequence.

Control of Eye Movements

• N. IV (trochlearis) for m. obliquus superior
• N. VI (abducens) for m. rectus lateralis
• N. III (oculomotor) for four other extrinsic eye muscles, eyelid raiser, pupil constriction, lens accomodation.

Sympathetic vs. Parasympathetic Branches

Cranial Nerves

Don't Break Your Skull Base

• Structures of the vertebrae nervous system include the:
• Medulla
• Pons
• Cerebellum Key feature the hindbrain is located at the caudal portion of the brain.

Metencephalon

Mesencephalon

Reticular Formation

• A diffusely arranged network of neurons extends from the mesencephalon (midbrain) through the metencephalon to the myelencephalon.
• Descending portion is one of several brain areas that control motor neurons of the spinal cord.
• The ascending portion projects to much of the cerebral cortex, selectively increases arousal and attention. Major structures of the forebrain diencephalon ("subcortical," lying below the cerebral cortex):
• The diagram illustrates specific structures. "limbic system." "basal ganglia: "concerned w/ the control and coordination of movement patterns.

The Thalamus

Limbic System

The limbic system consists of a number of other interlinked subcortical structures that form a ring-like border (limbus) around the brainstem: includes the

• Olfactory bulb
• Hypothalamus
• Hippocampus, parahippocampal gyrus
• Amygdala
• Cingulate gyrus of the cerebral cortex: associated with motivation, emotion, drives, and aggression.
• Amygdala expression of fear.
• Hippocampus learning & memory storage, including emotional memory.

The Hypothalamus

Basal Ganglia

Associated w/ planning of motor movement. Execution of automatic, action sequences. Involved in aspects of memory and emotional expression. Diseases that affect the BG are notable by virtue of the dramatic change in motor performance. The Cerebral cortex sulci (small grooves), sulcus (singular), fissures (large grooves). Longitudinal fissure a groove that separates right & left hemispheres. Sylvian or Lateral fissure the bulges were termed gyri, gyrus-singular. Corpus callosum (cc) a large tract of myelinated fibers (bundled axons) connecting the cells of the cerebral cortex of each hemisphere. The brain image included depicts these key structures outlined.

Cerebral Cortex Areas

• Primary sensory cortex for vision, hearing, and body sensations.
• Primary motor cortex.
• Olfactory bulb – for sense of smell.

Neuropsychological Research Methods

• Three primary categories
• Examine the effects of brain damage on behavior
• Record brain activity during behavior Examine the effects of stimulating particular parts of the brain

Brain Injuries

• Common Types; are tumors
• Cerebrovascular accidents/disorders infections
• Traumatic brain injuries (TBI) less common
• Neurotoxins genetic factors

Inflammation

• NORMAL response to harmful stimuli. Vasodilation (redness/warm).
• Fluid build-up (edema). Cell infiltration. Cells of the immune system Pain Loss of function. Difference between acute and chronic inflammation acute will call for help/fix the damage chronic immune system remains activated

Causes of Brain Injuries

1. Trauma and tumors from cerebrovascular accidents and disorders.
2. Infections from less common neurotoxins.
3. Genetic factors and the most common cause is falls, specifically in the elderly/babies.

Head Injury Specifics

Penetrating/open head injury the skull will be punctured.

• Penetrating/open head injuries the skull will be punctured.
• Brain damage at the site of blow when a 'coup' occurs.
• Brain damage that is opposite to the site of blow is known as 'contrecoup'.
• Brain damage on both sides is known as 'coup-contrecoup'.

Closed Head Injuries

Hemorrhage can cause a hematoma. Also can cause edema inflammatory cascade with diffuse possible axonal injury. Concussion is mild TBI and 80% of hospital admissions for a head injury are mild. The secondary neural damage could cause: Mitochondrial failure, reactive oxidative species formation & free-radical accumulation, altered genetic expression patterns & induction of inflammatory meditators, lastly cell death and transneural degeneration.

High School Athletes

• Athletes can sustain a high amount of injury: 15% of all evaluated sport-related injuries/concussions.
• As a result of less than 50% reporting, percentages may rise.

Sensitive Brains

• Adolescent brains are more sensitive for axonal injury where the damage can have significant impact. The Glasgow coma scale will be helpful.

Key Observational Insights

• Can't recall events; appears dazed/stunned, forgets an instruction; moves clumsily; answers questions slowly, loses consciousness briefly, experiences mood and personality changes. Reports indicate the potential for headache or "pressure"; possible nausea vomiting.

Brain Tumors

• New tissue growth that is morbid leading to enlargement/new growth of that tissue
• Resulting in uncontrolled cell division proliferation
• With 3 classifications that overlap with badness, tendency to grow, and origin.

Classifications

• Key indicators of brain mass include malignant and progressive ie keeps growing, or benign which is the bodies cell growth is being ceased through. Resulting in infiltrative vs. non-infiltrative the local brain can originate and metastasize.
• Characteristics the local may arise from local cells that are residing in affected organ - blood vessels The details may vary with 60% are local ,30% are meningioma, 25% are glioblastoma Multiforme.

Metastasized Tumors

-Metastasis is circulation and spreading of cancer cells to locations distal to organ:

• Metastatic tumors in secondary sites are not of the same type as the infiltrated organtissue this growth in secondary sites may upset metabolic needs.
• The function resident cells will begin to become impaired.

Oxygen and Bloodflow Issues

-oxia: Oxygen, -emia:blood flow.

Strokes

• Cerebrovascular Accidents with stroke, -anoxia vs. hypoxia with insufficient O2 with the O2. that you starting of hypoxic with end of anoxic the situations includes drowning, high alt, cos poisoning
• ischemia = insufficient blood flow to tissues that can lead to.
• Infarction tissue dies with cerebro disorders CVA with the temporary strokes that stroke don't count as CVA.

Transient Ischemic Attack

With anterior circulation with temp of clumsiness:

• anterior circulation(temp clumsiness. weak limbs aphasia).
• posterior circulation is dizziness double vision numb or weak area is extremities).

Atherosclerosis

• If there is a larger chance of CVA: causes blockage of brain artery, clotocclusion (thrombus and atherosclerotic and/or embolus. can take blood,

Embolus

Embolus typically a substance that travels in blood until it creates a blockage where symptoms include reduced levels of: sudden conciousness loss sensation voluntary, FAST used to recognize such factors as arms speech and time stroke for face.

Other Vascular Problems

• Can lead to CVA: hemorrhages may lead to hemorrhagic stroke ie aneurism. It can be inside cerbreal or subarachnoid.
• Ishemic vs, Hemmorrhagic is a medical contrast and diagnostic. Also to note is clinical presentations with: vascular dementia where the impairment leads to infections.

-### Clinical and Disease Specifics Caused by exogenous with potential pathogens of viruses. -Potential for bacteria & parasites: may result in presence of microbial. These can lead to viral diseases like the herpes with genitial and oral for herpes viruses. -The resulting infection can occur from infection may occur outside CNS

• Once active the cell undergoes domancy until activity starts.
• Encephalitis can affect these viral diseases as well. the temporal lobe and is often is a limic system setting.

Neurotoxins

• Is toxin that works specifically on nerve cells (venoms).
• This can occur by affecting the environmental chemical toxicants. The can damage the nerve cells and that can includes such environmental factors as mercucy,
• The image will also demonstrate how lead influences violent crime and some the drugs of abuse. The can result in glutamate excito.

Questions about cranial nerves, spinal cord injuries, and brain structures. Focus on motor control, sensory processing, and dopamine production. This quiz covers key aspects of neuroanatomy and nervous system function.