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Chapter 9. The Central Nervous System. About this Chapter. Emergent properties of the nervous system Anatomy and functions of the CNS Divisions of the brain and what each controls Integration of complex pathways for behavior Language, memory and others. Evolution of the Nervous System.

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chapter 9

Chapter 9

The Central Nervous System

about this chapter
About this Chapter
  • Emergent properties of the nervous system
  • Anatomy and functions of the CNS
  • Divisions of the brain and what each controls
  • Integration of complex pathways for behavior
  • Language, memory and others
evolution of the nervous system
Evolution of the Nervous System
  • Nerve net – jellyfish
  • Simple brain & nerve cord – flatworm
  • Brain & nerve cord with ganglia – earthworm
  • Increasing forebrain – fish, bird & human
    • Olfactory – fish
    • Complex behavior – birds
    • Reasoning & cognition – humans
evolution of the nervous system1
Evolution of the Nervous System

Figure 9-1: Evolution of the nervous system

embryonic development of nervous system
Embryonic Development of Nervous System
  • Neural plate to neural tube
  • Neural crest–PNS
  • Anterior forms brain
    • Forebrain
    • Midbrain
    • Hindbrain
  • Hollow ventricles
  • Spinal cord

Figure 9-2: The embryonic nervous system develops into a hollow tube

embryonic development of nervous system1
Embryonic Development of Nervous System

Figure 9-3 a-c: The neural tube specializes into the six major regions of the nervous system.

central nervous system overview
Central Nervous System: Overview
  • Brain
  • Spinal cord

Figure 9-4a: ANATOMY SUMMARY: The Central Nervous System

protecting the brain
Protecting the Brain
  • Hair, skin, cranium
  • Venous sinus blood
  • Meninges
    • Dura mater
    • Arachnoid membrane
    • Pia mater
  • Cerebrospinal fluid

Figure 9-4b, c: ANATOMY SUMMARY: The Central Nervous System

cerebrospinal fluid
Cerebrospinal Fluid
  • Produced by choroid plexus
  • Fills ventricles & subarachnoid space
  • A fluid pillow that floats the brain
  • Exchange transport
    • From blood
    • To brain tissue
csf functions
CSF Functions:

The CSF has several functions:

  • it provides physical support for the brain;
  • it protects against acute changes in arterial and venous blood pressure;
  • it is a route of waste excretion, replacing in many ways the function of lymphatics [the brain has no lymphatics);
  • it is involved in intra-cerebral transport, ex. hypothalamic releasing factors; 5) it helps maintain the ionic homeostasis of the CNS.
csf composition
CSF Composition
  • A comparison of the composition of CSF and plasma reveals that:
  • 1. CSF proteins are 1 % that of plasma;
  • 2. CSF calcium levels are 50% that of plasma;
  • 3. CSF glucose levels are 60% that of plasma;
  • 4. CSF chloride and magnesium levels are higher than plasma;
  • 5. CO2 diffuses rapidly, and HCO3 slowly, from the plasma into the CSF.
spinal tap clinically relevant csf information
Spinal Tap: Clinically Relevant CSF Information

Important information on CSF can be derived from the following parameters:

  • 1. opening pressure;
  • 2. gross appearance;
  • 3. total and differential cell count;
  • 4. bacterial culture and sensitivity;
  • 5. protein and glucose;
  • 6. analysis of immunoglobulins [detect chronic CNS inflammatory conditions);
  • 7. cytology [detect malignant cells).
csf appearance
CSF Appearance
  • clear and colourless (normal);
  • bright red - This indicates the presence of blood. The appearance of fresh blood in all three tubes supports the diagnosis of a subarachnoid hemorrhage. A traumatic tap [blood vessel damaged as the needle enters the spinal canal) will be indicated by the presence of blood in the first sample, with the disappearance of blood in subsequent samples
  • xanthochromic (yellow) - If there is no liver failure (jaundice can cause CSF to be yellow), xanthochromic CSF suggests that a subarachnoid hemorrhage has recently occurred [within days). The yellow color is due to bilirubin generated in the CNS by the breakdown of hemoglobin released from ABC's.
  • turbid - This indicates the presence of white cells and is suggestive of a CNS infection.
csf cell counts
CSF Cell Counts
  • CSF normally contains a small number of cells (usually lymphocytes and monocytes) and the total cell count is less than 5 cells/ cu mm. An increase in cell counts suggests either an infection of the CNS, or a number of CNS pathological conditions. The differential cell count provides further information regarding the possible cause of the CNS disease:
  • increased neutrophils - This indicates a bacterial meningitis. Other causes of an increased neutrophil count include a cerebral abscess, following seizures and following CNS hemorrhage;
  • increased lymphocytes - This indicates a viral meningitis. Lymphocyte counts are also elevated in meningitis, due to TB, syphilis, fungal and parasitic infections. Degenerative diseases of the CNS, such as multiple sclerosis, will also generate elevated lymphocyte counts.
  • “mixed reaction” - Here, there is an increase in neutrophils, lymphocytes and plasma cells. This is characteristic of TB meningitis, fungal meningitis and chronic bacterial meningitis;
  • increased plasma cells - This is a feature of TB meningitis and chronic inflammatory disorders, ex. multiple sclerosis;
  • leukemic cells - The presence of leukemic cells in the CSF indicates meningeal infiltration by leukemic cells. Leukemic cells typically appear in the CSF after several remissions have been achieved by chemotherapy. The blood-brain barrier prevents chemotherapeutic drugs from reaching the CNS and allows leukemic cells to escape treatment.
cerebrospinal fluid1
Cerebrospinal Fluid

Figure 9-5: ANATOMY SUMMARY: Cerebrospinal Fluid

blood brain barrier
Blood Brain Barrier
  • Extensive capillaries & sinuses
  • Tight junctions: limit permeability
  • Astrocyte foot processes: secrete paracrines
  • Protects brain: hormones & circulating chemicals
  • Many glucose transporters

Figure 9-6: The blood-brain barrier

spinal cord regions
Spinal Cord Regions
  • Cervical
  • Thoracic
  • Lumbar
  • Sacral

Figure 9-4a: ANATOMY SUMMARY: The Central Nervous System

spinal cord organization
Spinal Cord Organization
  • Gray matter: mostly cell bodies
    • Dendrites & terminals
    • Spinal reflex integrating center
  • White matter
    • Bundles of myelinated axons
      • Ascending tracts – sensory
      • Descending tracts – motor
    • Dorsal roots
    • Ventral roots
spinal cord organization1
Spinal Cord Organization

Figure 9-7: Specialization in the spinal cord

brain overview
Brain Overview
  • Trillion interneurons fill the brain
  • Up to 200,000 synapses each
  • Brain divisions
    • Cerebrum
    • Diencephalons
    • Midbrain
    • Cerebellum
    • Pons
    • Medulla oblongata
brain overview1
Brain Overview

Figure 9-9b, c: ANATOMY SUMMARY: The Brain

brain stem overview midbrain pons medulla
Brain Stem Overview: Midbrain, Pons & Medulla
  • Many cranial nerves enter
  • Pyramids – nerve tracts crossover
  • Midbrain – eye movement control
  • Pons – breathing, signal relay
  • Medulla – involuntary functions
    • Examples: Blood pressure, vomiting
  • Reticular formation:
    • Network in brain stem
    • Arousal, sleep, pain, & muscle tone
brain stem overview midbrain pons medulla1
Brain Stem Overview: Midbrain, Pons & Medulla

Figure 9-9d: ANATOMY SUMMARY: The Brain

cranial nerves
Cranial Nerves

Table 9-1: The Cranial Nerves

  • Homeostatic control centers
  • Thalamus – relay & sensory integration
  • Hypothalamus: Homeostatic Functions
    • Hunger, stress
    • Thirst: body osmolarity
    • Flight/fight pathways
    • Anger & fear
    • Circadian rhythms
    • Coordinates with endocrine system
additonal functions of hypothalamus
Additonal Functions of Hypothalamus
  • heart rate
  • urinary bladder contraction
  • blood pressure
  • oxytocin release
  • vasopressin release
  • corticotropin-releasing hormone release[8]
  • thermoregulation
  • panting
  • sweating
  • thyrotropin inhibition
  • GI stimulation
  • satiety
  • neuroendocrine control
  • Gonadotropin-releasing hormone (GNRH), also known as Luteinizing-hormone-releasing hormone(LHRH)
  • pupillary dilation
  • shivering

Figure 9-10: The diencephalon

pituitary and pineal glands
Pituitary and Pineal glands
  • Pituitary trophic & other hormones
  • Pineal
    • Melatonin
    • Sleep coordination

Figure 9-10: The diencephalon

  • Gray and white matter areas
  • Higher brain functions
  • Hemispheres
    • Corpus callosum- interconnection
    • Cerebral laterialization
      • Left brain – language
      • Right brain – special skills

Figure 9-11: The basal nuclei

Figure 9-16: Cerebral lateralization

more cerebrum
More Cerebrum:
  • Basal nuclei –control of movement
  • Limbic System
    • Cingulate gyrus –role in emotion
    • Hippocampus –learning & memory
    • Amygdala –emotion & memory

Figure 9-13: The limbic system

cerebral cortex outer layer of neurons 1mm thick
Cerebral Cortex: Outer layer of neurons (1mm thick)
  • Perception: hearing, vision, olfaction, muscles & viscera
  • Reasoning, information integration
  • Directing voluntary behavior
cerebral cortex outer layer of neurons 1mm thick1
Cerebral Cortex: Outer layer of neurons (1mm thick)

Figure 9-15: Functional areas of the cerebral cortex

A Florida teen is undergoing a miraculous recovery after he was accidentally shot in the head with a spear gun.
  • Yasser Lopez, 16, was on a fishing trip with friends June 7 when the spear gun they had brought along accidentally went off, shooting the 3-foot-spear through the teen's skull, according to Miami’s WSVN 7 News.
  • The spear miraculously missed all the major blood vessels in Lopez’s brain, doctors at Jackson Memorial Hospital told reporters during a press conference Monday.
  • The spear entered the boy's head about an inch above his right eye and went straight through the skull, doctors said.
  • "It's a striking injury," Dr. George Garcia told reporters. "It's something you don't see every day, a patient who arrives awake and speaking with a 3-foot-spear in his head."
the brain of a government employee
The Brain of a Government Employee!!!

This brain scan of a 44-year-old French civil servant, published in the journal Lancet, reveals his brain to be much smaller than normal. The dark area on the scan shows the swollen, fluid-filled space that has crowded his skull, leaving little room for his brain. Oddly, the man's cognitive abilities did not seem to be profoundly affected by his unusually small brain, as he was deemed to possess only moderately below-normal intelligence.

brushing a little too vigorously
Brushing a little too vigorously

In December, Vignesh Nageshwaran, 11, of Delhi, India, was simultaneously riding his bicycle to the florist's to pick up flowers for his mother and brushing his teeth when he fell off his bike while attempting a stunt. When he fell, the toothbrush pierced his soft palate and entered his skull. Nageshwaran was rushed to the hospital, where surgeons operated immediately. Despite the brush narrowly missing his spinal cord and a crucial blood vessel, Nageshwaran has recovered from his mishap.

i ve got a splitting headache
I’ve got a splitting headache!!

On July 3, 2007, a teenage Iraqi insurgent attacked Sgt. Dan Powers on the streets of Baghdad, plunging a 9-inch knife deep into his skull. Powers later recalled that he believed he had been punched, not stabbed -- and only when one of his comrades told him he had a knife in his head did he realize the extent of his injury.

Despite the severity of his injury, Powers remained alert as he was rushed to a combat hospital, where surgeons removed the knife, seen here in an X-ray image. He was then airlifted to the United States and taken to Walter Reed Army Medical Center. The injury left him barely able to walk, but after a grueling rehabilitation, Powers has rejoined his fellow paratroopers of the 118th MP Company out of Fort Bragg, N.C. Next month, Powers -- a fully qualified paratrooper once again -- will be boarding another military plane, this one bound for Afghanistan.
the one that got away
The one that got away.

Emerson de Oliveira Abreu required five hours of high-risk surgery after a fishing spear, which he apparently fired himself, ricocheted off rocks and penetrated his head and brain, The Associated Press reports. Abreu was injured while diving off the coast of Rio de Janeiro. The six-inch blade penetrated so deeply into his head that only the tip was visible, according to family members and authorities. (ABC)

In what Abreu's father, Edilson, described to the Brazilian press as a "miracle," the fishing spear entered just above Abreu's left eye and missed the most critical areas of his brain. Doctors say he is unlikely to suffer major, lasting damage from the accident. (ABC)
the old knife in the head routine
The old Knife in the Head Routine!!

The blade penetrated Wen's head above his right ear and reached down into the nasal cavity, finally emerging into his mouth. Surprisingly, it missed several major arteries, blood vessels and nerves -- which means that Wen could make a full recovery, according to doctors quoted in the news report.

Wen Wen, 38, of central China walked into Jiaotong University clinic in Xi'an with the entire blade of a knife buried in his head after his father allegedly stabbed him, according to a report from Central European News. One ER nurse reportedly fainted as Wen walked up to reception with the hilt of the knife poking out of his head and casually answered questions about his injury. (CEN Online)
the old arrow through the head routine
The Old Arrow through the Head Routine!!

Eleven-year-old Chinese schoolboy Liu Cheong had a brush with death when his friend shot him in the head with a 16-inch arrow, according to numerous international media reports. The arrow entered his skull through the eye socket and lodged in the back of his head. Somehow, the boy was spared a fatal brain injury

now where did i put my car keys
Now where did I put my car Keys??!!!

This X-ray shows how, during a fall, a car key penetrated the eyelid of 17-month-old Nicholas Holderman of Kentucky, reaching his brain. While doctors initially believed that the object had ruptured Nicholas' eyeball, another team of specialists later confirmed that the boy had sustained no permanent damage.

ow ow owwwwwww

According to local reports, 19-year-old Chris Clear was moving a roto-tiller on April 22 when a pin from the machine was thrown loose. It entered his nose and lodged in his brain, where it was eventually found by doctors during an X-ray. While Clear's initial prognosis was grim, surgeons were able to remove the pin in a marathon nine-hour surgery. Clear has reportedly lost some of his peripheral vision from the accident.

i think i ll use a hammer next time
I think I’ll use a Hammer next time!!

George Chandler of Shawnee, Kan., was installing latticework at his home with a friend when his nail gun fired unexpectedly, driving a 2.5-inch nail into the top of his head. According to local reports, Chandler arrived at the hospital via ambulance, his hat nailed to his head. Doctors used a claw hammer to remove the nail, and Chandler says he is none the worse for wear after the incident.

4 year old shot with a pellet gun
4 Year Old Shot with a Pellet Gun.

The white spot in the middle of this X-ray image is an air-gun pellet, lodged in the brain of 4-year-old British girl Somma Chapman. Doctors say Chapman is making an unlikely recovery after she was accidentally shot in the head by one of her playmates. The projectile caused a stroke, but fortunately it did not rupture any major blood vessels, the U.K. newspaper The Sun reported. (Caters News)

another knife in the head
Another Knife in the Head.

British military medics in Afghanistan were stunned when faced with a young patient who had a knife embedded in his head. Upon his arrival at the field hospital with his father, the boy was still conscious and able to walk. The boy reportedly received the injury when a man tried to attack his father.

the old screwdriver in the head routine
The Old Screwdriver in the Head Routine!!

A 2-year-old from Minnesota was treated at the Mayo Clinic in December after she tripped and fell on a screwdriver. The tool entered her head above her left eye. Fortunately, doctors were able to remove the screwdriver without surgery, and the girl escaped without major injury, according to media reports.

lobes of cerebral cortex and associated integration
Lobes of “Cerebral Cortex and Associated Integration
  • Frontal: voluntary movement, behavior, perception
  • Parietal – tactile sensory
  • Occipital – vision
  • Temporal – olfactory, auditory & gustatory
coordination of the brain functions
Coordination of the Brain Functions
  • Reticular activating system
    • From stem reticular fibers
    • Modulates consciousness
    • Distributes neuromodulators
  • NT/neuromodulator systems
    • Noradrenegic – norepinephrine
    • Serotonergeic – serotonin
    • Dopaminergic – dopamine
    • Cholinergetic – actetylcholine
coordination of the brain functions1
Coordination of the Brain Functions

Figure 9-19: The diffuse modulatory systems modulate brain function

coordination of circadian rhythms and sleep
Coordination of Circadian Rhythms and Sleep
  • Hypothalamic suprachiasmatic nuclei
  • Feedback loop: genes to regulator proteins
  • Most physiological systems have rhythmic patterns
  • Sleep: REM & deep sleep
coordination of circadian rhythms and sleep1
Coordination of Circadian Rhythms and Sleep

Figure 9-20: Electroencephalograms (EEGs) and the sleep cycle

complex pathways of emotion and motivation
Complex Pathways of Emotion and Motivation
  • Hypothalamus, limbic & cortex integration
  • Emotions: pleasure, sexual arousal, anger & fear limited cognitive control – "hard to turn off"
  • Motivation: "drives", increase arousal coordinate goal-oriented behavior
  • Moods:
    • Long term emotional states
    • Depression, SSRI
complex pathways of emotion and motivation1
Complex Pathways of Emotion and Motivation

Figure 9-21: The link between emotions and physiological functions

complex pathways of learning and memory
Complex Pathways of Learning and Memory
  • Learning – knowledge acquisition
    • Associative
    • Non-associative
  • Memory – retention & recall
    • Hippocampus & memory traces
    • Short term & working
    • Long term
    • Reflexive: "muscle memory"
complex pathways of learning and memory1
Complex Pathways of Learning and Memory

Figure 9-22: Memory processing

most complex pathways language and personality
Most Complex Pathways: Language and Personality
  • Language – exchange complex information
    • Wernike's area
    • Broca's area
  • Personality
    • Genetic components
    • Experiences
      • Learning
      • Memory
      • Perceptions
most complex pathways language and personality1
Most Complex Pathways: Language and Personality

Figure 9-23: Cerebral processing of spoken and visual language

pathologies of the brain
Pathologies of the Brain
  • Head trama
  • Schizophrenia
  • Epilepsy
  • Depression
  • Alzheimer's
  • CNS divisions: development anatomy & overview of functions
  • Brain protection & exchange: meninges, cerebrospinal fluid, blood brain barrier
  • Cranial nerves
  • Brain divisions and association areas
  • Regulation and regional coordination: neuromodulators
  • Complex pathways: emotion, motivation, behavior, learning, memory, & language