The Brain
The Brain
Weighs almost 3 lbs
Consists of about 100 billion neurons
and 10-50 trillion neuroglia
Parts of the Brain
The Brain Stem


Continuous with the
spinal cord
Consists of medulla
oblongata, pons and
midbrain
Diencephalon


Above the brain stem
Consists of the thalmus,
hypothalmus and pineal
gland
Parts of the Brain
Cerebrum


Forms most of the brain
Consists of a thin layer
of gray matter, the
cerebral cortex and
white matter
Cerebellum


Posterior to the brain
stem
Means “little brain”
Cranial Meninges


Continuous with the spinal meninges
Includes the Dura Mater, Arachnoid Mater
and Pia Mater
Brain Blood Supply
Oxygen – The brain requires 20% of
the body’s oxygen supply. Neurons
that are without oxygen for 4 or more
minutes may be permanently damaged
Glucose - the glucose in the blood is the
source of energy for the brain’s cells.
Very little glucose is stored in the brain,
so if there isn’t enough glucose in the
blood a person can experience
confusion, dizziness, convulsions and
loss of consciousness.
The Blood Brain Barrier (BBB)
Protects the brain from
harmful substances and
pathogens by blocking passage
of many substances from the
blood into brain tissue. Does
NOT protect from lipid-soluble
substances such as oxygen,
carbon dioxide, alcohol, and
most anesthetic agents.
Cerebrospinal Fluid (CSF)
A clear, colorless liquid that carries
oxygen, glucose, and other needed
chemicals from the blood to the
neurons. It removes wastes and toxic
substances produced by the brain and
spinal cord cells
Brain Stem
Medulla Oblongata

a continuation of the spinal cord
containing all the sensory and motor
tracts extending between the spinal
cord and other parts of the brain
1. Cardiovascular Center – regulates
the rate and force of the heartbeat and
the diameter of the blood vessels
2. Medullary Rhythmicity Area –
adjusts the basic rhythm of breathing
3. Other areas also responsible for
reflexes for swallowing, vomiting,
coughing and sneezing
4. Receives input from or provides
output to cranial nerves 8 – 12
Pons

Above the medulla and anterior to
the cerebellum
 1. bridge that uses axons to connect
parts of the brain with one another
 2. helps to control breathing
 3. associated with cranial nerves 5 – 8
Midbrain - connects the pons to the
diencephalon
1. Cerebral Peduncles – conduct
nerve impulses from the cerebrum to
the spinal cord, medulla and pons
 2. Substantia Nigra – large and
darkly pigmented. Associated with
Parkinson’s Disease
 3. Red Nucleus – looks red due to
rich blood supply. Helps to coordinate
movement.

Diencephalon
Thalamus – paired oval masses of
gray matter. Important relay
stations for sensory impulses.
Plays a role in acquisition of
knowledge (cognition). Also
contributes to motor function and
regulation of autonomic activities
Hypothalamus – small portion below
the thalamus. Functions in control of
the autonomic nervous system, pituitary
gland, regulation of emotional and
behavioral patterns, eating and drinking,
body temperature and circadian
rhythms.
Pineal Gland – size of a small pea.
Part of the endocrine system because it
secretes the hormone melatonin which
contributes to sleepiness.
Cerebellum
Compares intended movement with
what is actually happening. Regulates
posture and balance. Coordinates
complex motor activities


A. Cerebellar Hemispheres – located
posterior to the medulla and pons and
below the cerebrum.
B. Cerebellar Cortex – Surface
consisting of gray matter
Cerebrum
interprets sensory impulses, controls
muscular movements and functions in
emotional and intellectual processes
A. Gyri – folds of brain tissue
B. Fissures – deep groves between folds
C. Sulci – shallow groves between folds
D. Corpus Callosum – broad band of
white matter containing axons that
extend between the 2 hemispheres
E. 4 Lobes (per hemisphere) – named
by the bone that covers it

1. Frontal, parietal, temporal and occipital
F. Basal Ganglia – coordinates
automatic muscle movements and
regulates muscles tone.