Transcript Central Nervous System

Unit IV: Coordination
Central Nervous System
Chapter 12 and 13
Central Nervous System
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Consists of the brain and the spinal cord
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Functions of the CSF:
1.
Buoyancy
2. Protection
3.
Interstitial fluid
in thalamus
Chemical stability
Nutrients,
O2
Capillaries
Waste products,
CO2
Astrocyte
Removal
of waste
Production
of CSF
Neuron
Ependymal
cells
Cerebrospinal
fluid in
third ventricle
Blood - Brain Barrier
• Composed of tightly joined blood capillaries in the brain
• Highly permeable to:
– H2O, glucose, O2, CO2, alcohol, caffeine, nicotine, anesthetics
• Circumventricular Organs
• Blood – CSF barrier
Functions of the Spinal Cord
• Conduction
• Locomotion
– central pattern generators (walking)
• Reflexes
Anatomy of the Spinal Cord
• Cylinder of nerve tissue within the
vertebral canal
– 1.8 cm x 45 cm
• Spinal cord extends to L1 in adults
• 31 pairs of spinal nerves
• Cervical, thoracic, lumbar, and sacral
regions
Meninges of the CNS
• Fibrous membranes surrounding brain and spinal cord
• Dura mater
– epidural space
• Arachnoid mater
– layer of simple squamous epithelium adhering dura mater
– loose mesh of fibers joining to the pia mater
– creates subarachnoid space
• Pia mater
– denticulate ligaments anchor the cord
Meninges of the Spinal Cord
Structure of Spinal Cord
Dorsal root
White matter
Gray
matter
• Central area of gray matter
shaped like a butterfly and
surrounded by white matter in
three columns
Dorsal root
ganglion
Spinal nerve
Segment C3
Ventral root
White matter
• Gray matter =
neuron somas with little myelin
Gray matter
Segment T3
• White matter =
myelinated axons
Segment L1
Segment S
Central
canal
Gray Matter
• Dorsal/posterior horns
– Sensory neuron fibers enter here and may synapse with interneuron
• Ventral/anterior horns
– Contain somas of somatic motor fibers
• Lateral horns – thoracic and lumbar regions, contain neurons of sympathetic
nervous system
• Gray commissure – connects right and left sides
• Central canal – lined with ependymal cells and filled with CSF
Gray matter:
Central canal
Posterior horn
Gray commissure
Lateral horn
Anterior horn
Dorsal root of spinal nerve
Dorsal root ganglion
Spinal nerve
Ventral root
of spinal nerve
White Matter
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Bundles of myelinated axons
3 pairs of columns or funiculi
Ascending and descending tract
Contralateral Ipsilateral Decussation Ascending
tracts
Descending
tracts
White matter:
Posterior column
Lateral column
Anterior column
Spinal nerve
The Brain - General
• Directions: Rostral and Caudal
Cerebrum
Diencephalon
(covered by
cerebrum)
• Major parts:
− Cerebrum
− Cerebellum
− Brainstem
• Cerebrum is largest area
• Cerebellum contains 50% of
the neurons
Pons
Medulla
oblongata
Cerebellum
Spinal cord
Mesencephalon
(covered by
cerebrum)
White Matter of Cerebrum
• Most of cerebrum is white matter
• Types of tracts:
– projection tracts
– association tracts
Projection fibers Longitudinal
fissure
– commissural tracts
Corpus callosum
Anterior commissure
Anterior view
Gray Matter of Cerebrum
• Involved in neural integration
• Three places:
1. Cerebral Cortex
• Motor cortex, sensory cortex, auditory, visual
Gray Matter of Cerebrum
• Three places:
2. Basal Nuclei
• Subconscious motor control
3. Limbic System
• Emotional states
• Memory storage
• Thinking – linking conscious
intellectual functions of
cerebral cortex with
unconscious autonomic
functions of brainstem
Brain Scans
Rostral
Caudal
Visual cortex
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The word cad is seen in
the visual cortex.
Location of Hindbrain
Cerebellum
Pons
Medulla Oblongata
Spinal Cord
Hindbrain
Medulla Oblongata
• 3 cm extension of spinal cord
• Ascending and descending nerve tracts
• Sensory and motor nuclei receive input from:
– controls:
– cardiac center
– vasomotor center
– two respiratory centers
• Cranial nerves IX – XII begin or end here
− Salivation, swallowing, gastric secretions and motility,
auditory
Hindbrain
Pons
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Relays signals from cerebellum to cerebrum
Cranial nerve V
VI, VII, VIII arise at junction with medulla
Contains nuclei concerned with swallowing, sleep, hearing, eye
movements, taste, facial expressions and sensations, and posture
Tracts
Ascending tracts Descending tracts
Respiratory Centers
Pneumotaxic center
Apneustic center
Transverse fibers
Cerebellum
Midbrain
Fourth
ventricle
Pons
Medulla
oblongata
Spinal cord
Olivary nucleus
Reticular formation
Hindbrain
Cerebellum
• 10% mass but 60% more surface area = ½ of all brain neurons
• Functions
− Adjust postural muscles (balance & equilibrium)
− Fine-tune movements
• General role in evaluation of sensory inputs
– Tactile sensors in fingertips (ex. Textures without looking)
– Timekeeping center (elapsed time between stimuli)
– Some hearing (pitch, distinguish between similar sounding words)
– AD/HD (small cerebellums)
Structures of the Midbrain
• Cerebral Peduncles
− Nerve fiber bundles
– Contain corticospinal tracts (fine motor control)
• Tegmentum
– Collaborates with cerebullum (fine motor control)
• Substantia nigra
– sends inhibitory signals to basal nuclei and thalamus
Pineal gland
– Parkinson disease
Thalamus
Superior colliculus
Posterior view of
brain stem and
diencephalon
Red nucleus
Substantia nigra
Inferior colliculus
Cerebral peduncles
Reticular activating system (RAS)
Structures of the Midbrain
• Central gray matter (pain awareness)
• Tectum (two of each)
– superior colliculi (visual reflexes)
– inferior colliculi (auditory reflexes)
• Reticular formation
– Somatic motor control
– cardiovascular control
– Pain modulation
– Habituation
– Sleep and consciousness
• Irreversible coma
Cranial Nerves of the Brainstem
Midbrain
Cerebral peduncle
Superior colliculus
Inferior colliculus
Oculomotor III
Trochlear IV
Trigeminal V
Pons
Abducens VI
Facial VII
Vestibulocochlear VIII
Glossopharyngeal IX
Vagus X
Accessory Nerve XI
Hypoglossal XII
Medulla oblongata
Spinal
nerve C1
Spinal
nerve C2
Spinal cord
Lateral view
Midbrain and Forebrain
leaves
Corpus callosum
Thalamus
Habenula
Anterior
commissure
Pineal gland
Hypothalamus
Optic chiasm
Pituitary gland
Midbrain
(a)
Epithalamus
Forebrain (Diencephalon)
Thalamus
• Relays nearly all sensory input going to cerebrum
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Key role in motor control output
arousal, eye movements, taste, smell, hearing, equilibrium and
somesthetic senses
Emotional and memory functions of limbic system
Thalamus
Optic chiasm
Optic tract
Cerebral peduncle
(midbrain)
Lateral view of the
left thalamus and midbrain
Forebrain (Diencephalon)
Hypothalamus
• Generally controls ANS and endocrine system
• Functions:
1. hormone secretion
Hypothalamic Nuclei
2. autonomic effects
Autonomic centers
3. thermoregulation
Preoptic area
4. food and water intake Suprachiasmatic nucleus
Hormonal centers
5. Sleep/wake cycles
6. Memory-mammillary
7. emotional behavior
Thalamus
Hypothalamus
Pons
Infundibulum
Anterior
pituitary
gland
Posterior
pituitary
gland
Mamillary body
Forebrain (Diencephalon)
Epithalamus
Consists of :
• Pineal gland
 secretes melatonin (Circadian rhythms)
• Habenula
 connects limbic system to cerebrum
Forebrain (Telencephalon)
Cerebrum
Right Cerebral Hemisphere
Left Cerebral Hemisphere
Sensory information
Interpretive centers
Analyzing the emotional
context of a conversation
General interpretive and speech centers
Reading, writing, and speaking
premotor cortex
analytical tasks
RIGHT HAND
LEFT HAND
Prefrontal
cortex
Prefrontal
cortex
Speech center
Writing
Auditory cortex
(right ear)
General interpretive center
(language and mathematical
calculation)
Visual cortex
(right visual field)
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Anterior commissure
Analysis by touch
Auditory cortex
(left ear)
Spatial visualization
and analysis
Visual cortex
(left visual field)
Forebrain (Telencephalon)
Cerebrum
• Gyri and Sulci – increase surface area for more neurons!
Cerebral Cortex Functions
• Brain waves
• Sleep
• Cognition
• Memory
• Emotion
• Sensation
• Special Senses
• Motor Control
• Language
• Lateralization of Cerebrum
Alpha waves
Beta waves
Theta waves
Delta waves