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The Brain and
Cranial Nerves
The Brain
– Introduction
– Development of brain
 Embryology
– Anatomy of brain
 Parts and functions
The Brain
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
– First two weeks – neural tube forms
– 4th week - anterior end of the neural tube forms
the
 forebrain
 midbrain
 hindbrain
Embryology – 3-4 Weeks
Embryology – 4 Weeks
Embryology – 5 Weeks
Embryology – 11 Weeks
A Child’s Brain
Adult Brain
– Forebrain
 Cerebrum
 Thalamus & hypothalamus
– Midbrain
– Hindbrain
 Cerebellum & pons
 Medulla oblongata
Adult Brain
Protections and Coverings
– Cranial bones – strong support
– Cranial meninges – shock absorbers
 Dura mater
 Arachnoid
 Pia mater
The Cranial Meninges
The Ventricles of the Brain
– Hollow areas within the brain
 Connect to spinal canal and space around the brain
– Cerebrospinal fluid circulates around the brain,
down through the ventricles, and into the spinal
cord.
Ventricles of the Brain
Ventricles of the Brain
Cerebrospinal Fluid
– Composition
 Clear, colorless, watery
 Contains proteins, glucose, urea, salts
 Contains white blood cells
– Functions
 “Floats” the brain
 Medium of transport
Circulation of
Cerebrospinal Fluid
Problems Associated with
CSF
– Hydrocephalus
– Meningitis
– Headaches
Hydrocephalus
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
Blood-Brain Barrier
The Parts of the
Brain
Forebrain
Cerebrum,
Hypothalamus, Thalamus
Cerebrum – Gray & White
Matter
– Outer layer – cerebral cortex
 Gray matter
– Inner portion
 White matter
 Masses of gray matter – cerebral nuclei
Cerebrum – Gray & White
Matter
Cerebral Cortex
– Gyri are separated by grooves (sulci)
 Fissures – deeper grooves
– Divided into cerebral hemispheres
Gyri & Sulci
Cerebral Cortex
– Divided into lobes
– Well mapped
 Decision-making, planning, personality
 Primary motor cortex
 Primary sensory cortex
Cerebral Lobes
Homunculus
Primary Motor Cortex
Primary Sensory Cortex
Cerebral Nuclei
– Collections of cell bodies (gray matter)
– Mostly control the movement of skeletal
muscles
Cerebral Nuclei
Limbic System
– Functional unit (not anatomical)
– Emotional part of the brain
 Feelings of fear, loss, love, rage, etc.
– Includes parts of several anatomical structures
 Cerebrum
 Hypothalamus
 Thalamus
Limbic System
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
Hypothalamus
– Location – under thalamus
– Structure
 Clusters of nerve cell bodies
– Autonomic centers
 Infundibulum
Hypothalamus
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
The Thalamus
Thalamus
Epithalamus
– Location
 Above thalamus
– Contains the pineal body
 Secretes melatonin
Midbrain
Midbrain
– Relay station
– Tracts of motor and sensory neurons
– Contains nuclei
 Substantia nigra secretes dopamine
– Modifies muscle tone & motor activity
– Parkinson’s disease
Midbrain
Hindbrain
Cerebellum, Pons, &
Medulla Oblongata
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
Cerebellum
– Functions – controls subconscious movements
in skeletal muscle
 Coordination
 Posture
 Balance
Cerebellum, Pons, Medulla
Oblongata
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)
Medulla Oblongata
– Continuation of spinal cord
– Functions
 Maintains wakefulness and alertness
 Contains reflex centers
– Cardiac center, vasomotor center, respiratory rythmicity
center
– Other nonvital centers
Medulla Oblongata
Cranial Nerves
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
thorax
The Cranial Nerves