Functional Anatomy & Physiology
Dr. Ra’ed Ahmed
MBChB, FIBMS
Neurologist March 31 - 2015
Lec. 1
09.00 AM
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Functions of the Nervous System
1. Sensory input – gathering information
To monitor changes occurring inside and outside the body (changes = stimuli).
2. Integration –
to process and interpret sensory input and decide if action is needed.
3. Motor output
A response to integrated stimuli.
The response activates muscles or glands.2
Structural Classification of the Nervous System
Central nervous system (CNS)
Brain
Spinal cord
Peripheral nervous system (PNS)
Nerve outside the brain and spinal cord
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Organization of the Nervous System
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Nervous Tissue: Support Cells (Neuroglia or Glia) of CNS
Astrocytes (largest of neuroglia)
Abundant, star-shaped cells
Brace neurons
Form barrier between capillaries and neurons
Control the chemical environment of the brain (CNS)
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Nervous Tissue: Support Cells
Microglia (CNS)
Spider-like phagocytes
Dispose of debris
Ependymal cells (CNS)
Line cavities of the brain and spinal cord
Circulate cerebrospinal fluid
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Nervous Tissue: Support Cells
Oligodendrocytes
(CNS)
Produce myelin
sheath around
nerve fibers in the
central nervous
system
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Support Cells of the PNS
Satellite cells
Protect neuron cell bodies
Schwann cells
Form myelin sheath in the peripheral nervous system
Figure 7.3e
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Neuron Anatomy
Slide 7.9b
Cell body : nucleus large nucleolus
Dendrites – conduct impulses toward the cell body
Axons – conduct impulses away from the cell body
Figure 7.4a
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Central Nervous System (CNS)
CNS develops from the embryonic neural tube
The neural tube becomes the
brain and spinal cord
The opening of the neural tube
becomes the ventricles
Four chambers within the brain
Filled with cerebrospinal fluid 11
Brain Part of CNS that lies within the cranial
vault, the encephalon.
Its hemispheric surface is convoluted and has gyri and sulci
Weighs 350 g in the newborn and 1400 g in the adult.
The male brain is on average slightly heavier than the female brain
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Regions of the Brain
Cerebral hemispheres
Diencephalon
Brain stem
Cerebellum
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Lobes of the Brain
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Frontal lobes:
• Reasoning,abstraction,concentration
• Control of voluntary eye
movements.
• Motor control of speech in the
dominant hemisphere.
• Motor Cortex
• Urinary continence.
• Emotion and personality
Parietal lobes:
• Sensory cortex – define size,
weight, texture and consistency
(contralateral).
• Sensation is localised, and
modalities of touch, pressure and
position are identified.
• Awareness of the parts of your body.
• Dominant is involved in ideomotor
praxis
• Non-dominant – visuospatial
information
Temporal lobes:
• Primary auditory receptive areas.
handle visual perception and olfaction.
• Learning and memory, emotional
affect.
• Dominant temporal lobe influences
comprehension of speech.
• Nondominant temporal lobe
mediates prosody and spatial
information
Occipital lobes:
• Primary visual cortex.
• Visual association areas.
• Visual perception.
• Some visual reflexes (i.e. visual
fixation).
• Involuntary smooth eye movements
Brodmann’s areas : mapping the cortical areas of the brain.
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Motor Homunculus
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Sensory Homunculus
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Layers of the CerebrumGray matter
Outer layer
Composed mostly of neuron cell bodies
White matter
Fiber tracts inside the gray matter
Figure 7.13a
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Basal Ganglia large masses of gray matter deep within
the cerebral hemispheres.
Include the caudate, putamen, and globus pallidus that lie lateral to the thalamus.
Functionally, substantia nigra (SN) and the subthalamic nucleus.
Motor control includes the preparation for and execution of cortically initiated movement
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Diencephalon
Sits on top of the brain stem
Enclosed by the cerebral hemispheres
Made of four parts
Thalamus
Hypothalamus
Epithalamus (roof of the third ventricle Houses the pineal body, choroid plexus)
Subthalamus25
Diencephalon
Figure 7.15
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Thalamus
Surrounds the third ventricle.
The relay station for sensory impulses.
Transfers impulses to the correct part of the cortex for localization and interpretation.
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Hypothalamus
Under the thalamus.
Important autonomic nervous system center
Helps to regulate body temperature
Controls water balance
Regulates metabolism, appetite control.
An important part of the limbic system (emotions)
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Brain Stem
It is a small, narrow region connecting the spinal cord with the rest of the brain
Parts of the brain stem
Midbrain
Pons
Medulla oblongata
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Brainstem
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Midbrain
located between the diencephalon and the pons.
Mostly composed of tracts of nerve fibers
Reflex centers for vision and hearing
Cerebral aquaduct – 3rd-4th ventricles
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Pons
pons means “bridge” in Latin
The bulging center part of the brainstem
Mostly composed of fiber tracts
Includes nuclei involved in the control of breathing
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Medulla Oblongata
The lowest part of the brain stem
Merges into the spinal cord
Includes important fiber tracts
Contains important control centers
Heart rate control
Blood pressure regulation
Breathing
Swallowing
Vomiting 33
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Cranial nerves on the anterior surface of the
brain.
Cerebellum or "small brain"
Located in the posterior cranial fossa
Attached to the brainstem by three cerebellar peduncles
Forms the roof of the fourth ventricle
Anatomically divided into the two hemispheres, the midline vermis and the flocculonodulus ,consists of folia and fissures on its surface
Provides involuntary coordination of body movements
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Protection of the Central Nervous System
Scalp and skin
Skull and vertebral column
Meninges
CSF
BBB
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SKULL
22 bones in total, 8 make up the cranium, other 14 facial bones.
Cranium is that part of the
skull that encloses the brain
3 components within
the cranium have a balance
(80% brain ,
10% blood ,10% CSF).
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Meninges
Dura mater " hard mother"
Double-layered external covering
Periosteum – attached to surface of the skull
Meningeal layer – outer covering of the brain
Folds inward in several areas (falxcerebri, tentorium cerebelli & falxcerebelli)
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Meninges
Arachnoid layer " spider"
Middle layer ,extremely thin , nonvascular
Web-like, loosely encloses the brain
Pia mater:
Inner most, delicate highly vascular
Intimately adhere to the brain substance
Spaces of the meninges: extradural, subdural and subarachnoid.
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Cerebrospinal Fluid CSF
Similar to blood plasma composition
Formed by the choroid plexus
Reabsorbed into the venous blood flow via the arachnoid villi
Produces at a rate (~ 500mL/day) and total volume (~ 150mL)
Buoyancy , Protection ,Transport of nutrients, Removal of waste products
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Ventricles and Location of the Cerebrospinal Fluid
Figure 7.17b42
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Spinal Cord Continuous with the
medulla oblongata at the spinomedullary junction terminates caudally as conus medullaris.
Ends at the level of lower border of L1
Enlargements occur in the cervical and lumbar regions
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Spinal Cord cont.
lies within subarachnoid space and covered by three meningeal coats (pia , arachnoid and duramater).
Averges, in length, 45 cm in males and 42 cm in females
Weighs about 30 g , comprising 2% of the adult brain weight
The spinal cord comprises
31 segments defined by
31 pairs of spinal nerves 45
PNS : Spinal Nerves
Figure 7.22a 46
APPROACH TO THE PATIENT WITH NEUROLOGIC DISEASE
Where is the lesion?
What is the lesion?
Meridians of Longitude= motor, sensory
pathways (location, function, decussation)
–Corticospinal
–Spinothalamic
–Dorsal column – Medial Lemniscus
Parallels of Latitude( Cortex---muscle)
What are the most important regions for anatomic localization?
Cortical Brain
Subcortical Brain
Brainstem
Cerebellum
Spinal Cord
Root
Peripheral Nerve
Neuromuscular Junction
Muscle
How are symptoms localized to these neuroanatomic regions?
Neurologic Examination:
1- Higher Cortical Function
2- Cranial Nerves
3- Cerebellar Function
4- Motor
5- Sensory
6- Deep Tendon Reflexes
7- Pathologic Reflexes
Characteristic of upper motor neurone lesions: UMNL
• No wasting, but from disuse;
• Increased tone “Spasticity” of clasp-knife
type;
• Weakness most evident in anti-gravity
muscles;
• Increased reflexes and clonus;
• Extensor plantar responses.
Characteristics of lower motor neurone lesions: LMNL
• Wasting “pronounced” ;
• Fasciculation;
• Decreased tone (i.e. flaccidity);
• Weakness;
• Decreased or absent reflexes;
• Flexor plantar responses.
Corticospinal Tracts
Pain & Temperature
Position sense
• Ataxia or clumsiness of movement
• Partial compensation by active monitoring of movement by the eyes;
• No weakness.
Patterns of sensory deficit
Clinical features of Cortical Brain lesion
Dominant (usually left) hemisphere is “aphasia”
Nondominant (usually right) hemisphere,
usually causes visual-spatial problems.
Cortical sensory loss such as two-point
discrimination, stereognosis, and
graphesthesia.
Seizures are almost always cortical in origin.
Incomplete hemiparesis, affecting the face and
arm, but not the leg.
The sensory homunculus has a similar
somatotropic arrangement
Clinical features of Subcortical Brain lesion
Higher Cortical Function: normal
Cranial Nerves: visual field cuts
Cerebellar Function: usually normal
Motor: weakness in face=arm=leg ,UMNL
Sensory: sensory abnormalities in
face=arm=leg
Deep Tendon Reflexes: hemi-hyper-reflexia
Pathologic Reflexes: extensor planter reflex
Clinical features of Brainstem disease
The brain stem is essentially the spinal cord with
embedded cranial nerves.
Cranial nerve signs: diplopia, decreased
strength or sensation over the face, dizziness,
deafness, dysarthria, dysphagia
Long tract signs: hemiparesis UMNL or
hemisensory loss
Crossed signs or Bilateral findings
Clinical features of Cerebellar disease
A. Incoordination of muscle activity:
• in the head: nystagmus, dysarthria;
• in the arms: finger–nose ataxia, kinetic
(intention) tremor, difficulty with rapid alternating
movements (dysdiadochokinesia);
• in the legs: heel–knee–shin ataxia, gait ataxia,
falls.
B. Hypotonia ,no Weakness, Sensory: normal
DTRs normal ,Pathologic Reflexes: none
Clinical features of Spinal cord disease
Atriad of symptoms (Sensory level,Spastic
weakness & Bowel and bladder problems)
Distal weakness greater than proximal
weakness (UMN signs below the lesion)
Increased tone (spasticity)
Increased reflexes ,Clonus
Extensor plantar response
Absent superficial reflexes
No significant atrophy or fasciculations
Clinical features of Root diseases (Radiculopathies)
Pain is the hallmark of root disease
Weakness, while asymmetric, may be either
proximal or distal, depending on which roots are
involved
O\ E = LMN findings
Atrophy and fasciculations.
Tone is normal or decreased, and hypo- to a-
reflexia if the root carries a reflex.
Sensory loss occurs in a dermatomal
distribution.
Clinical features of Peripheral neuropathies
Weakness leg, arm : distal predominant
Sensory changes : distal predominant
O\E
Distal, often asymmetric weakness with atrophy,
fasciculations
Muscle tone is often decreased. loss of distal
reflexes, Mute responses to plantar stimulation
Sensory loss
Clinical features of Neuromuscularjunction disease
“Fatigability” “Fluctuation” the hallmark of
NMJ
Proximal symmetric weakness
Weakness is often extremely proximal,
involving muscles of the face, eyes
(ptosis), and jaw.
Muscles are normal in size, without
atrophy or fasciculations, with normal tone
and reflexes.
No sensory loss.
positive response to anticholinesterase.
Clinical features of Muscle disease
Proximal symmetric leg & arm weakness
without sensory loss.
O\E
Muscles : normal in size, without atrophy
no fasciculation;
Tone : normal or reduced;
Reflexes : normal or reduced.
what is the lesion?
Happy Reading !
THANK YOU
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