Transcript The Fore Brain - White Plains Public Schools

The Fore Brain
Diencephalon
Diencephalon
This represents the central core of the
forebrain and is surrounded by the cerebral
hemispheres. It is made up of three major
paired structures:
– The thalamus
– The hypothalamus
– The epithalamus
Diencephalon
Thalamus is a bilateral egg shaped nuclei that
makes up 80% of the diencephalon.
It is the relay station for information coming
into the cerebral cortex.
Thalamus
The thalamus is a collection of smaller nuclei,
each having a functional specialty.
All afferent impulses converge on to the
thalamus and synapse with at least one of its
nuclei.
It serves as the gateway to the cerebral cortex.
Thalamus
All the sensory fibers except olfaction go
through one of the thalamic nuclei.
For example the lateral geniculate nuclei
receive input from the retina.
The thalamus also plays an important role in
sleep.
Dorsal nuclei
Medial Lateral
dorsal
Lateral
posterior
Pulvinar
Anterior
nuclear
group
Medial
geniculate
body
Reticular
nucleus
Lateral
geniculate
body
Ventral
anterior
Ventral
Ventral posterolateral lateral
Ventral nuclei
(a) The main thalamic nuclei. (The reticular nuclei that “cap” the
thalamus laterally are depicted as curving translucent structures.)
Copyright © 2010 Pearson Education, Inc.
Thalamus
Disorders of the Thalamus are usually due to
stroke which can lead to the thalamic pain
syndrome.
Hypothalamus
Hypothalamus lies just below the thalamus
and forms the lower walls of the third
ventricle.
It is the major visceral control center of the
body and is the major center for regulating
the body’s homeostatic mechanisms.
Hypothalamus
These functions include:
–
–
–
–
–
–
–
Autonomic control
Emotional response
Temperature regulation
Food intake
Water balance
Sleep wake cycles
Endocrine function
Epithalamus forms the roof of the third
ventricle. Its most visible landmark is the
pineal gland which secretes melatonin and is
involved in the sleep wake cycle.
Brains Stem
The brain stem is made up of the midbrain,
pons and medulla oblongata. The brain stem
produces programmed automatic behaviors
necessary for survival.
It is similar in make up to the spinal cord and
consists of projection fibers.
Pons
It is noticeable as a bulge on the anterior
surface of the brain stem.
It is made up of conduction tracts.
Dorsally it forms part of the forth ventricle.
Medulla Oblongata
It is the most inferior part of the brain stem.
As it passes through the foramen magnum, it
becomes the spinal column.
Medulla Oblongata
The medulla plays an important role in
maintaining certain autonomic functions
including:
– Heart rate
– Respiration
– Swallowing, sneezing & vomiting
Hanging
The medulla oblongata
is destroyed when a
person is hung, leading
to “instant” death.
Cerebellum
It consists of two hemispheres connected by
the vermis. It is highly convoluted and has
gyri known as folia.
The cerebellum controls body movements. It
is also involved in recognizing the sequence of
events so adjustments in limb action can be
made. Disorders are described as an ataxia.
Figure 12.17a Cerebellum.
Anterior lobe
Arbor vitae
Cerebellar
cortex
Pons
Fourth
ventricle
Medulla
oblongata
(a)
Copyright © 2010 Pearson Education, Inc.
Posterior
lobe
Flocculonodular lobe
Choroid plexus
Functional Brain Systems
Functional brain systems are networks of
neurons that incorporate various areas of the
brain. Two major systems are the:
– Limbic system
– Reticular formation
Limbic System
Limbic System is a groups of structures located
on the medial aspect of each cerebral
hemisphere and the diencephalon. Its cerebral
structures encircle the brain stem.
Limbic System
It is a complex system with multiple functions.
Included in it are the:
– Septal nuclei
– Cingulate gyrus
– Parahippocampal gyrus
– Dentate gyrus
– Hippocampus
– Amygdala
These are all found in the cerebrum
Limbic System
In the diencephalon:
– Hypothalamus
– Thalamic nuclei
Limbic System
The limbic system is our emotional brain.
– The Amygdala recognizes angry or fearful facial
expressions and assesses danger.
– The cingulate gyrus plays a role in expressing our
emotions through gestures and helping us to
“cope”.
– The hippocampus is involved with long term
memory
Limbic System
The limbic system is our emotional brain.
– Dentate gyrus is thought to regulate happiness 
– Parahippocampal gyrus is thought to regulate
spatial memory
Premotor cortex
Corpus
callosum
Cingulate
gyrus
Primary
motor cortex
Frontal eye field
Prefrontal
cortex
Processes emotions
related to personal
and social interactions
Orbitofrontal
cortex
Olfactory bulb
Olfactory tract
Fornix
Occipital
lobe
Visual
association
area
Primary
visual cortex
Temporal lobe
(b) Parasagittal view, right hemisphere
Primary motor cortex
Sensory association cortex
Copyright © 2010 Pearson Education, Inc.
Central sulcus
Primary somatosensory
cortex
Parietal lobe
Somatosensory
association cortex
Parieto-occipital
sulcus
Motor association cortex
Uncus
Primary
olfactory cortex
Primary sensory cortex
Multimodal association cortex
Calcarine sulcus
Parahippocampal
gyrus
It looks like a sea horse?
Septum pellucidum
Diencephalic structures
of the limbic system
•Anterior thalamic
nuclei (flanking
3rd ventricle)
•Hypothalamus
•Mammillary
body
Olfactory bulb
Copyright © 2010 Pearson Education, Inc.
Corpus callosum
Fiber tracts
connecting limbic
system structures
•Fornix
•Anterior commissure
Cerebral structures of the
limbic system
•Cingulate gyrus
•Septal nuclei
•Amygdala
•Hippocampus
•Dentate gyrus
•Parahippocampal
gyrus
Reticular Formation
This system extends from the medulla
oblongata, pons and midbrain.
The reticular formation is involved in actions
such as awaking/sleeping cycle, and filtering
incoming stimuli to discriminate irrelevant
background stimuli.
Reticular Formation
Lesions affecting the reticular formation cause
severe alterations in level of consciousness
and coma.
Figure 12.19 The reticular formation.
Radiations
to cerebral
cortex
Visual
impulses
Auditory
impulses
Reticular formation
Ascending general
sensory tracts
(touch, pain, temperature)
Copyright © 2010 Pearson Education, Inc.
Descending
motor projections
to spinal cord