The Brain and Cranial Nerves
Chapter 9c
The Brain
– Introduction
– Development of
brain
• Embryology
– Anatomy of
brain
• Parts and
functions
Introduction to the Brain
– Weighs about 3 lbs. in adults
– Structures
• Divided into 3 general areas
– Functions
• Controls the bare necessities of life
• Location for primal drives and emotions
• Intellectual thought, imagination, perception,
interpretation, etc.
Human Development - Embryology
– First two weeks - neural tube forms
– 4th week - anterior end of the neural tube forms the
• forebrain
• midbrain
• hindbrain
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Embryology – 4 Weeks
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Embryology – 5 Weeks
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Embryology – 11 Weeks
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A Child’s Brain
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Adult Brain
– Forebrain
• Cerebrum
• Thalamus &
hypothalamus
– Midbrain
– Hindbrain
• Cerebellum
& pons
• Medulla oblongata
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Protections and Coverings
– Cranial bones
– Cranial
meninges
• Dura mater
• Arachnoid
• Pia mater
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The Ventricles of the Brain
– Hollow areas within the brain
• Connect to spinal canal and space around the brain
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Ventricles of the Brain
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Cerebrospinal Fluid
– Composition
• Clear, colorless, watery
• Contains proteins, glucose, urea, salts
• Contains white blood cells
– Functions
• “Floats” the brain
• Medium of transport
– Formed by specialized cells along edges
of ventricles
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Circulation of Cerebrospinal Fluid
– Cerebrospinal
fluid circulates
around the brain,
down through
the ventricles,
and into the
spinal cord.
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Problems Associated with CSF
– Hydrocephalus
– Meningitis
– Headaches
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Blood-Brain Barrier
– A function of glial cells
• Secrete chemicals that
maintain the BBB
• Absorb materials from
blood
• Extract materials from
brain
– Cells of capillaries form
tight junctions
– Differential rates of
passage of certain
materials
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The Parts of the Brain
Forebrain
Cerebrum, Hypothalamus,
Thalamus
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Cerebrum – Gray & White Matter
– Outer layer
• Cerebral cortex
– Gray matter
– Inner portion
• White matter
• Cerebral nuclei
– Masses of gray
matter
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Cerebral Cortex
– Gyri are separated
by grooves (sulci)
• Fissures – deeper
grooves
– Divided into
cerebral
hemispheres
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Cerebral Cortex
– Divided into lobes
– Well mapped
• Decision-making,
planning,
personality
• Primary motor
cortex
• Primary sensory
cortex
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Homunculus
Primary Motor Cortex
Primary Sensory Cortex
Cerebral Nuclei
– Collections of cell
bodies (gray
matter)
– Mostly control the
movement of
skeletal muscles
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Limbic System
– Functional unit
– Emotional part of
the brain
• Feelings of fear,
loss, love, rage, etc.
– Includes parts of
several anatomical
structures
• Cerebrum
• Hypothalamus
• Thalamus
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Hypothalamus
– Location – under
thalamus
– Structure
• Clusters of nerve cell
bodies
– Autonomic centers
• Infundibulum
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Hypothalamus
– Initiates primal drives
• Hunger, thirst, sex, rage, etc.
• Controls autonomic nervous system
– “fight or flight” sympathetic response.
– Controls pituitary gland (“master gland”
of endocrine system)
• Infundibulum (“funnel”) funnels secretions
to the pituitary gland
Thalamus
– Functions as a relay station between the body
and the cerebral cortex
• Inform us of our
emotional state
• Relay information
concerned with
motor requirements
& actions
• Integrate visual and
auditory reflexes
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Epithalamus
– Location
• Above
thalamus
– Contains the
pineal body
• Secretes
melatonin
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Midbrain
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Midbrain
– Relay station
– Tracts of motor and
sensory neurons
– Contains nuclei
• Substantia nigra
secretes dopamine
– Modifies muscle
tone & motor
activity
– Parkinson’s
disease
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Hindbrain
Cerebellum, Pons, &
Medulla Oblongata
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Cerebellum
– 2nd largest structure of
the brain
– Divided into 2 lateral
hemispheres
– Cortex – gyri & sulci
• Gray matter
– Interior
• White matter
– Cerebellar nuclei –
deep within white
matter
• Gray matter
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Cerebellum
– Functions – controls subconscious
movements in skeletal muscle
• Coordination
• Posture
• Balance
Pons
– Pons = “bridge”
• Connects the spinal
cord with the brain
and parts of the
brain with each
other
• Consists mostly of
white fibers
– Functions
• Controls
respiration rate
(with medulla)
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Medulla Oblongata
– Continuation of
spinal cord
– Functions
• Maintains
wakefulness and
alertness
• Contains reflex
centers
– Cardiac center,
vasomotor center,
respiratory
rythmicity center
– Other nonvital
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centers
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Cranial Nerves
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Introduction to Cranial Nerves
– 12 pairs
– Leave the skull
through foramina
– Types
• Mixed
• Sensory
• Motor
– Part of the somatic
nervous system
– Innervate organs in
head, neck and upper
Human Anatomy, 3rd edition
thorax
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