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Transcript of NERVOUS SYSTEM: THE BRAINfaculty.mtsac.edu/mpresch/35_lecture_files_unit_4/18 Anat 35 Brain...
NERVOUS SYSTEM: THE BRAIN
Human Anatomy
Unit 4
Major Divisions of the Brain
Terminology
• Gray ma<er – Unmyelinated regions
• White ma<er – Myelinated axons
General Structures of Gray Ma<er (Cortex)
• Gyrus (gyri p.) – folds of the cerebral surface
• Sulcus (sulci p.) – grooves between gyri
• Fissure – deep groove
Ventricles of the Brain
• Lateral ventricles – 2 ventricles shaped like “ram horns” – inferior, medial to cerebral hemispheres
• Third ventricle – surrounded by diencephalon of brain stem
• Fourth ventricle – anterior to cerebellum – contains 3 apertures leading to the “subarachnoid space”
– (2 lateral and 1 median)
Ventricles of the Brain
Ventricles & Central Canal
• Cerebral aqueduct – canal between third and fourth ventricle
• Central canal – centrally located in the spinal cord
• Ventricles lined with choroid plexus and ependymal cells – cerebrospinal fluid producVon
• Cerebrospinal fluid circulates throughout ventricles, central canal and subarachnoid space
• Returns to general circulaVon through arachnoid villi at dural sinuses
The Cranial Meninges
Cranial Meninges Dura Mater
• “Tough mother” – dense connecVve Vssue – outer, double layered surrounding the brain • outer = periosteal layer • inner = meningeal layer (folded in certain locaVons as a “falx”)
– openings between the 2 layers are dural sinuses
Cranial Meninges Arachnoid Mater
• “Spidery mother”
• Arachnoid granulaVons – for return of CSF to general circulaVon
• network of connecVve Vssue
Cranial Meninges Pia Mater
• “Delicate mother”
• indissecVble from surface of the CNS
• loose connecVve Vssue
Falx Cerebri
Cerebrospinal Fluid
• Surrounds and bathes exposed surfaces of the CNS
• FuncVons – Prevents fricVon – Support – RegulaVon of microenvironment
• Choroid plexus – 500 ml/day
CirculaVon of CSF
• 150 ml in circulaVon
• CSF from lateral ventricles – Interventricular foramen ‐ ‐>
3rd ventricle
– Aqueduct of midbrain
– From 4th ventricle enters subarachnoid space • Lateral aperture • Median aperture
• 4th ventricle ‐ ‐ > central canal
– Subarachnoid space ‐ ‐> arachnoid granulaVons
Blood Supply to the Brain
Internal caroVd arteries Vertebral arteries
Jugular veins Drain the dural sinuses
Cerebrum
• Cerebral hemispheres – Leb and right halves – Separated by longitudinal
fissure
– Connected in spots by tracts • Lobes • Contain “higher brain
centers”
• Nuclei responsible for motor coordinaVon and control of memory, emoVon and other funcVons
The Cerebral Lobes
• 5 major divisions in each hemisphere • 4 named aber bones under which they lie – Frontal – Parietal – Occipital – Temporal
• 1 on interior – Insula
The Cerebral Lobes
Insula
• Small lobes deep in lateral sulcus beneath temporal lobes
• FuncVon: memory and interpretaVon of taste
insula New study suggests that the insula is involved in smoking addiction…
Naqvi, N.H., et al, 2007. Damage to the insula disrupts addiction to cigarette smoking. Science. V315;531-4.
Motor Areas of the Cerebral Cortex
• Control voluntary movement
• Precentral gyrus • Primary motor cortex
– Pyrimidal cells
• Pathway is corVcospinal tract
Sensory Areas of the Cerebral Cortex
• Conscious awareness of sensaVon
• Primary sensory cortex – Postcentral gyrus
• Collaterals also deliver info to basal nuclei and other centers
• Visual cortex • Auditory cortex • Olfactory cortex • Gustatory cortex
AssociaVon Areas of the Cerebral Cortex
• AssociaVon areas • Integrate and store informaVon
• Interpret sensory info • Help plan, prepare for and help coordinate motor output
• Somatosensory associaVon area
• Pre‐motor cortex
IntegraVve Centers of the Cerebral Cortex
• Receive, process informaVon from many associaVon areas
• Direct complex motor acVviVes
• Complicated analyVcal funcVons
The Central White Ma<er
• AssociaVon tracts – Connect regions of cortex within same hemisphere
• Commissural tracts – Bridges between cerebral hemispheres – Ex) corpus callosum
• ProjecVon tracts – Between cerebral cortex, caudal brain, and spinal cord
The Central White Ma<er
Basal Nuclei
• Paired, irregular masses of gray ma<er
• within white ma<er in basal region of cerebral hemispheres
• Involved in – Motor control – Learning
• Components – Caudate nucleus – Amygdala – Putamen & globus pallidus – Claustrum
The Basal Nuclei
Limbic System
• Large group of nuclei, inferior to the corpus callosum
• Responsible for control of emoVon, sex drive, aggression, memory consolidaVon among other funcVons
• Hippocampus • Responsible for memory consolidaVon
Limbic System
Diencephalon
• “in‐between” brain • Components – Epithalamus – Thalamus (right and leb) – Hypothalamus
• FuncVons – Relay and switching staVon for certain sensory and motor pathways
– Control visceral acVviVes
Epithalamus
• Covers 3rd ventricle • Contains choroid plexus and ependymal cells producing CSF and the pineal gland
• Posterior porVon – Pineal gland
• Melatonin
• Circadian rhythms
– Habenular nucleus • Relay staVon for limbic system • Visceral and emoVonal response to odors
Thalamus
• Clusters of nuclei organized into groups • Major relay staVon for sensory informaVon
• Gray ma<er on both sides of third ventricle
Hypothalamus
• Contains many diverse nuclei controlling – body temperature
– sex drive – feeding – drinking – thirst sensaVon – pituitary secreVons
• forms the inferior walls of the third ventricle
Diencephalon
Diencephalon
Brain Stem
• Connects forebrain (cerebrum, diencephalon) and cerebellum to spinal cord
• 3 parts – Midbrain – Pons – Medulla oblongata
The Diencephalon and the Brain Stem
The Diencephalon and the Brain Stem
Pons
• Contains sensory and motor tracts • Autonomic respiratory center – Pneumotaxic center – ApneusVc center
• origin for many cranial nerves (V‐VIII)
Medulla Oblongata
• DecussaVon of pyramids • the inferior most region of the brain stem • Nuclei controlling addiVonal respiratory funcVons, cardiac, vomiVng
• origin of many cranial nerves
Pons and Medulla
The Cerebellum
• the second largest single structure of the brain • Three lobes – Anterior – Posterior – Flocculonodular (small)
Anatomy of the Cerebellum
• arbor vitae – “the tree of life” – white ma<er (axon tracts) of the cerebellum
– cerebellar cortex folded into many plate‐like ridges called “folia”
• Vermis – narrow band of cortex that separates the cerebellar hemispheres
The Cerebellum