Download Structure and Function of the Brain

Structure and Function
of the Brain
science.nationalgeographic.com
Major Divisions of the Brain
Brainstem
(Medulla)
Divisions are based on developmental origins; they do
not sub-serve discrete functions.
Myelencephalon
Myelencephalon
= Medulla oblongata
Evolutionarily the oldest portion
of the brain
Serves as the connection
between the higher levels of
the brain and the spinal cord.
Contains mainly axonal tracts,
but some nuclei
Myelencephalon: Nuclei
The medulla contains cardiac, respiratory and vomiting centers
and so deals with basic autonomic (involuntary) functions such
as heart rate and breathing. In addition, it contains the inferior
olivary nuclei (inputs to cerebellum; motor coordination) and the
dorsal column nuclei (cuneatus and gracilis; touch).
www.austincc.edu
Metencephalon: The Pons
Contains two major structures:
the pons; and
the cerebellum
The pons is situated dorsal to
the medulla. Like the medulla, it
is composed of many ascending
and descending fiber tracts.
Metencephalon: The Cerebellum
The cerebellum (Latin for “little
brain”) consists of a single,
tightly-folded layer of cortex, with
white matter underneath, and
several deep nuclei embedded in
the white matter.
It plays an important role in
motor control. It does not initiate
movement, but contributes to
coordination, precision and
timing. It may also be involved
with functions such as attention
and language, and regulate fear
and pleasure responses.
www.studyblue.com
Mesencephalon
Mesencephalon = Midbrain
Considered to be the top of
the brainstem
Two divisions:
• the tectum (roof) is the
dorsal surface
• the tegmentum is ventral
to the tectum
The tegmentum initiates the
division of the forebrain into
two separate hemispheres.
Mesencephalon: Tectum
In mammals, the tectum is composed of two pairs of bumps, called
the colliculi (little hills). The anterior pair, called the superior colliculi,
have a visual-motor function, specifically to direct the body’s
orientation towards or away from a visual stimulus. The posterior
pair, called the inferior colliculi, are part of the auditory system.
antranik.org
Mesencephalon: Tegmentum
The tegmentum has three
“colorful” nuclei:
• periaqueductal gray (cell
bodies)
– pain modulation
– defensive behavior
– maternal behavior
• red nucleus (iron)
– motor coordination
• substantia nigra (melanin)
– movement planning
www.studyblue.com
The Reticular Formation
The reticular formation is not a single structure but a complex
network of about 100 tiny nuclei that span the brainstem. It is
involved in a variety of behaviors including sleep-wake transitions
and arousal/attention (the reticular activating system; RAS),
voluntary motor control, reward and addiction (ventral tegmental
area; VTA), and mood (locus coeruleus, Raphe nuclei).
RAS
VTA
locus
coeruleus
Raphe nuclei
motor
Diencephalon
Composed of two structures:
• thalamus
• hypothalamus
The thalamus is a two-lobed
structure; one lobe sits on
each side of the third
ventricle. Lobes connected
by the massa intermedia.
Visible on the surface are
bands of axons
The hypothalamus is located
just below the anterior
thalamus (hypo = below)
Diencephalon: The Thalamus
Comprises many nuclei
Richly and reciprocally
connected to the cortex
Functions:
• Process/relay info to
cortex
• Consciousness
• Attention
• Sleep/wake states
brainmeta.com
Diencephalon: The Hypothalamus
Comprises many nuclei
Synthesizes and secretes
hormones; some into
systemic circulation, others
to stimulate/inhibit secretion
of pituitary hormones
Functions:
• Links the nervous
system to the endocrine
system
• Controls activities of the
autonomic nervous
system
brainmeta.com
Telencephalon: Cerebral Cortex
Edge: cell bodies
(cortex: gray matter)
Core: axons (white matter)
Cortex is convoluted in
humans to increase surface
area
Fissures: large furrows
Sulci: small furrows
Gyri: ridges
Commissures connect the
hemispheres: corpus callosum
Telencephalon: Lobes
The major fissures partially
divide each hemisphere into
four lobes: frontal; parietal;
temporal and occipital
Three large gyri: precentral;
postcentral and superior
temporal
Lobes are not functional
units
Telencephalon: Some Functions in Lobes
Sensory
speech
Motor
speech
Executive functions:
thinking, planning,
organizing and
problem solving;
emotions and
behavioral control;
and personality
Memory
Pearson Education, Inc
Telencephalon: Neocortex
Neocortex: 6 layers
• Layer 4, input from thalamus
• Layer 5, output to thalamus,
brainstem and spinal cord
90% of human cortex (an
exception: hippocampus)
Features:
• Pyramidal vs stellate cells
• Layers differ in thickness,
cell density and type
• Vertical axons give rise to
columnar organization
• Layer thickness differs from
brain area to area
Telencephalon: Limbic System
A circuit of midline structures
that circle the thalamus
(limbic = “ring”)
Includes: amygdala,
hippocampus, cingulate,
fornix, septum, mammillary
bodies
Regulates emotional life
including the four Fs, and
contributes to memory
formation
Telencephalon: Basal Ganglia
A circuit of midline structures
lateral to the thalamus
Includes: striatum (caudate
and putamen), globus
pallidus and substantia nigra
Plays a role in the
performance of voluntary
motor responses
virginia.edu
Summary of Major Brain Structures
Apps: Brain Tutor; 3D Brain