Transcript Essentials of Human Anatomy Nervous System II Brain • An adult brain weighs between 1.35 and 1.4 kilograms (kg) (around 3 pounds) and has.

Essentials of Human Anatomy
Nervous System II
Brain
• An adult brain weighs between 1.35 and
1.4 kilograms (kg) (around 3 pounds) and
has a volume of about 1200 cubic
centimeters (cc).
• Brain size is not directly correlated with
intelligence
• It is not the physical size of the brain that
determines intelligence—it is the number
of active synapses.
Functions of the Brain
• interprets sensations
• determines perception
• stores memory
• reasoning
• makes decisions
• coordinates muscular movements
• regulates visceral activities
• determines personality
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The Brain’s 4 Major Regions
• Prosencephalon (forebrain)
– Telencephalon: cerebrum
– Diencephalon: epithalamus,
thalamus,hypothalamus
• Mesencephalon (midbrain)
– Mesencephalon: cerebral peduncles, colliculi
• Rhombencephalon (hindbrain)
– Metencephalon: pons, cerebellum
– Myelencephalon: medulla oblongata
The Brain’s 4 Major Regions
• The cerebrum is divided into two halves, called
the left and right cerebral hemispheres.
• Each hemisphere is subdivided into four
functional areas called lobes.
• Outer surface of an adult brain exhibits folds
called gyri (gyrus) and shallow depressions
between those folds called sulci (sulcus).
• The brain is associated with 12 pairs of cranial
nerves.
Lobes of Cerebral
Hemispheres
1. Frontal
2. Parietal
3. Temporal
4. Occipital
Insula
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Functional Regions of
Cerebral Cortex
Cerebral Cortex – thin layer of gray
matter that constitutes the outermost
portion of cerebrum; contains 75% of
all neurons in nervous system
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Diencephalon
• Between cerebral hemispheres and above the brainstem
• Surrounds third ventricle
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Diencephalon
Thalamus
• gateway for sensory impulses
heading to cerebral cortex
• receives all sensory impulses
(except smell)
• channels impulses to
appropriate part of cerebral
cortex for interpretation
Hypothalamus
maintains homeostasis by
regulating visceral activities
links nervous and endocrine
systems
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Diencephalon
Limbic System
Consists of
• portions of frontal lobe
• portions of temporal lobe
• hypothalamus
• thalamus
• basal nuclei
• other deep nuclei
Functions
• controls emotions
• produces feelings
• interprets sensory impulses
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Brain Stem
Three Parts
1. Midbrain
2. Pons
3. Medulla Oblongata
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Midbrain
• between diencephalon and
pons
• contains bundles of fibers
that join lower parts of
brainstem and spinal cord
with higher part of brain
Pons
• rounded bulge on underside of brainstem
• between medulla oblongata and midbrain
• helps regulate rate and depth of breathing
• relays nerve impulses to and from medulla
oblongata and cerebellum
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Medulla Oblongata
• enlarged continuation of spinal cord
• conducts ascending and descending
impulses between brain and spinal cord
• contains cardiac, vasomotor, and
respiratory control centers
• contains various nonvital reflex control
centers (coughing, sneezing, swallowing,
vomiting)
Cerebellum
• inferior to occipital lobes
• posterior to pons and medulla
oblongata
• two hemispheres
• vermis connects hemispheres
• cerebellar cortex – gray matter
• arbor vitae – white matter
• cerebellar peduncles – nerve fiber
tracts
• dentate nucleus – largest nucleus in
cerebellum
• integrates sensory information
concerning position of body parts
• coordinates skeletal muscle activity
• maintains posture
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Cranial Nerves
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membranes surrounding CNS
• protect CNS
• three layers
• dura mater – outer, tough
• arachnoid mater – thin, weblike
• pia mater – inner, very thin
Meninges
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Spinal Meninges
Three membranes
surround all of CNS
1) Dura mater - "tough
mother", strong
2) Arachnoid meninx spidery looking, carries
blood vessels, etc.
3) Pia mater
2) Arachnoid
Subarachnoid space
1) Dura mater
3) Pia mater - "delicate
mother", adheres
tightly to surface of
spinal cord
Ventricles
• interconnected cavities
• within cerebral
hemispheres and brain stem
• continuous with central
canal of spinal cord
• filled with cerebrospinal
fluid (CSF)
• lateral ventricles
• third ventricle
• fourth ventricle
• cerebral aqueduct
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Cerebrospinal Fluid
• secreted by choroid
plexus
• circulates in ventricles,
central canal of spinal
cord, and subarachnoid
space
• completely surrounds
brain and spinal cord
• clear liquid
• nutritive and protective
• helps maintain stable ion
concentrations in CNS
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Lumbar Puncture (= Spinal Tap)
L3
L4
For clinical examination of CSF or
administration of radiopaque dyes,
drugs and sometimes anesthetics
However: mostly “epidurals” for
anesthetics
THE END