Brain Stem / Pons - North Seattle College
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Transcript Brain Stem / Pons - North Seattle College
The Brain and
Cranial Nerves
Major Parts of the Brain
1. Brain stem – continuous with spinal
cord
Midbrain
Pons
Medulla Oblongota
Major Parts of the Brain
2. Cerebellum – Posterior to brain stem
Major Parts of the Brain
3. Diencephalon – superior to the brain
stem
Thalamus
Epithalamus
Hypothalamus
Subthalamus
Major Parts of the Brain
4. Cerebrum – largest part of the brain
supported by the diencephalon and brain
stem
Brain Stem
1. Medulla Oblongata
Continuous with spinal cord
Contains both motor and sensory tracts
Brain Stem / Medulla
Contains portrusions of white matter
called called pyramids
Brain Stem / Medulla
The crossing of pyramids result in
neurons in the left cerebral cortex
controlling skeletal muscles on the right
side of the body and neurons in the right
cerebral cortex controlling skeletal
muscles on the left side
Brain Stem / Medulla
There are reflex centers for regulation of
heart rate, respiratory rate,
vasoconstriction, swallowing, vomiting
Brain Stem / Pons
Superior to the medulla
Helps control breathing
It relays nerve impulses related to
voluntary skeletal movements from the
cerebral cortex to the cerebellum
Brain Stem / Midbrain
Extends from the pons to the
diencephalon
Cerebral Peduncles, superior colliculi,
and inferior colliculi located here
Brain Stem / Midbrain
Cerebral Peduncles – contain major
motor tracts
Brain Stem / Midbrain
Superior colliculi – help with reflex head
turning in response to visual stimuli
Responsible for the pupillary reflex and
accomodation reflex (adjusts shape of
lens for far versus close vision)
Brain Stem / Midbrain
Inferior coliculi – helps with reflex head
turning in response to auditory stimuli
Reflex center for startle reflex
Cerebellum
Vermis - central constricted area
Cerebellar hemispheres – lateral lobes
Cerebellum
Cerebellar cortex – superficial layer of
the cerebellum made up of gray matter
Cerebellum
Arbor Vitae – Deep to the gray mater
made up of tracts (White Matter)
Cerebellum
Main function – Regulates posture and
balance
Diencephalon / Thalamus
A pair of oval masses of grey matter,
organized into nuclei, with interspersed
tracts of white matter
Diencephalon / Thalamus
Intermediate mass – Joins the right and
left halves of the thalamus
Diencephalon / Thalamus
Surrounds the third ventricle
Diencephalon / Thalamus
It registers conscious recognition of pain,
temp., light touch, and pressure.
You need your cerebral cortex to
understand the nature of the pain.
Diencephalon /
Hypothalamus
Inferior to the thalamus
Diencephalon /
Hypothalamus
Mammillary bodies – serve as reflexes
related to the sense of smell
Diencephalon /
Hypothalamus
Infundibulum – Connects the pituitary
gland to the hypothalamus
Diencephalon /
Hypothalamus
Axons from the paraventricular and
supraoptic nuclei form the
hypothalamohypophyseal tract extends
through the infundibulum to the posterior
pituitary
Diencephalon /
Hypothalamus
Functions
Control of the ANS
Production of hormones
Regulation of emotional and behavioral
patterns
Regulation of eating and drinking
Control of body temperature
Diencephalon /
Epithalamus
Superior and posterior to thalamus
Diencephalon /
Epithalamus
Pineal Gland – It secretes the hormone
melatonin.
Diencephalon /
Subthalamus
Below the thalamus
Helps control body movements
Circumventricular Organs
Part of the diencephalon called CVOs
that can monitor chemical changes in the
blood because they lack a blood-brain
barrier
Circumventricular Organs
Part of the hypothalamus, the pineal
gland, and the pituitary gland
Circumventricular Organs
Thought to be the site of entry into the
brain of HIV.
Cerebrum
Largest part of the brain
Cerebrum
Cerebral cortex is composed of grey
matter
The deep grooves are called fissures
Shallower grooves are called sulci
Cerebrum
Beneath the cortex lies cerebral white
matter
Cerebrum
Longitudinal fissure separates it into right
and left halves
Cerebrum
The corpus callosum (a bundle of white
fibers) connects it internally.
Cerebrum
Each cerebral hemisphere is separated
into four lobes (frontal, parietal, temporal,
and occipital)
Cerebrum
White matter is under the cortex and
consists of myelinated axons running in
three principle directions
Cerebrum
Association fibers connect and transmit
nerve impulses between gyri in the same
hemisphere
Cerebrum
Commissural fibers connect gyri in one
cerebral hemisphere to the
corresponding gyri in the opposite
hemisphere
Cerebrum
Projection fibers transmit impulses from
the cerebrum to other parts of the brain
and spinal cord
Cerebrum
Basal ganglia are paired masses of grey
matter internally located in each cerebral
hemisphere
Cerebrum
The Basal Ganglia function in controlling
muscular movements
Cerebrum
Huntington’s disease is a hereditary
degenerative disorder of the basal nuclei.
Patients may suffer from abrubt, jerky,
almost continuous movements called
chorea
Cerebrum
Limbic System found in the cerebral
hemispheres and diencephalon
Cerebrum
It functions in emotional aspects of
behavior and memory, and is associated
with pleasure and pain
We tend to remember things associated
with strong emotions. (Think back to the
events you remember from early
childhood. What emotions pop up?)
Lobes of the Cerebrum
Central Sulcus – Separates the frontal
lobe from the parietal lobe
Lobes of the Cerebrum
Precentral gyrus – immediately anterior
to the central sulcus
Lobes of the Cerebrum
Postcentral gyrus – Located immediately
posterior to the central sulcus
Lobes of the Cerebrum
Lateral cerebral sulcus – Separates the
frontal lobe from the temporal lobe
Parieto-occipital sulcus
Separates the parietal lobe from the
occipital lobe
Blood-Brain Barrier (BBB)
Prevents passage of many substances
from blood into brain tissue
Blood-Brain Barrier (BBB)
Endothelial cells of brain capillaries are
sealed together by tight junctions
Blood-Brain Barrier (BBB)
Processes of astrocytes press up against
the brain capillaries and only allow
certain substances to pass from the
blood to neurons
Blood-Brain Barrier (BBB)
Glucose (water soluble) crosses the BBB
via active transport
Blood-Brain Barrier (BBB)
Other water soluble substances such as
creatinine, urea, and most ions cross
slowly
Blood-Brain Barrier (BBB)
Proteins and antibiotics cannot cross
Blood-Brain Barrier (BBB)
Lipid soluble substances such as oxygen,
carbon dioxide, alcohol, and most
anesthetic agents cross easily
Protective coverings of
the Brain
1. Cranium
2. Cranial Meninges – continuous with the
spinal meninges
Protective coverings of
the Brain
Cranial Meninges made up of;
Dura Mater – outer
Arachnoid Mater – middle
Pia Mater – inner
Protective coverings of
the Brain
Subarachnoid space – between the
arachnoid mater and pia mater which
contains cerebrospinal fluid
Protective coverings of
the Brain
Three extensions of the dura mater
separate parts of the brain
Protective coverings of
the Brain
1. Falx Cerebri – Separates the two
hemispheres
Protective coverings of
the Brain
2. Falx Cerebelli – Separates the two
hemispheres of the cerebellum
Protective coverings of
the Brain
3. Tentorium Cerebelli – Separates the
cerebrum from the cerebellum
Cerebrospinal Fluid
Clear colorless liquid
Cerebrospinal Fluid
Protects the brain and spinal cord against
physical and chemical injuries
Cerebrospinal Fluid
Caries glucose, oxygen, and other
chemicals from blood to neurons and
neuroglia
Cerebrospinal Fluid
Circulates through cavities in the brain
and spinal cord and in the subarachnoid
space of the brain and spinal cord
CSF-filled cavities within
Brain
1. Lateral Ventricles – Within each
hemisphere of the cerebrum
CSF-filled cavities within
Brain
2. Third Ventricle – A narrow cavity along
the midline superior to the hypothalamus
and between the R. and L. halves of the
thalamus
CSF-filled cavities within
Brain
3. Fourth Ventricle – between the brain
stem and the cerebellum
Circulation of CSF
CSF is formed by filtration from networks
of capillaries called choroid plexuses
(found in the ventricles) and in the brain
tissue
Circulation of CSF
1.
2.
3.
4.
5.
It circulates through the;
Lateral ventricles
Third ventricle
Cerebral aqueduct
Fourth ventricle
Then down through the central canal
and around the brain (subarachnoid
space)
Circulation of CSF
Most of the fluid is absorbed by the
arachnoid villi
Sensory Areas
Sensory Areas of the cerebral cortex are
concerned with the reception and
interpretation of sensory impulses
Sensory Areas
Primary Somatosensory area – located in
the postcentral gyrus
Sensory Areas
Primary Somatosensory Area – Localizes
exactly the points of the body where
sensations originate
Sensory Areas
Primary Visual Area – located in the
occipital lobe and receives impulses that
convey information for vision
Sensory Areas
Primary Auditory Area – located in the
superior part of the temporal lobe
Sensory Areas
Primary Auditory Area – Helps you
interpret pitch, rhythm, and loudness of
speech
Sensory Areas
The primary gustatory area – it receives
impulses for taste and is located in the
parietal lobe
Sensory Areas
Primary Olfactory Area – Located in the
medial aspect of the temporal lobe and
receives impulses for smell
Motor Areas
Govern muscular movements
Motor Areas
Primary Motor Area – is in the precentral
gyrus
Motor Areas
Primary Motor Area - It has cell bodies of
neurons that descend to the cord
Motor Areas
Broca’s Area – Is located in the frontal
lobe close to the lateral cerebral sulcus
and is the motor speech area
Association Areas
Association areas are concerned with
complex integrative functions such as
memory, emotions, reasoning, will,
judgement, personality traits, and
intelligence
Association Areas
Wernicke’s Area – Is a broad region in
the temporal and parietal lobes
Association Areas
Wernicke’s Area – Responsible for
understanding language, but it may be
more involved in sounding out unfamiliar
words.
Aphasia
Aphasia is the inability to use or
comprehend words due to injury to the
association or motor speech areas
Aphasia
Receptive Aphasia – You have problems
with comprehension but your own
language is ok
Aphasia
Expressive Aphasia – You may
comprehend language but your speech
does not make any sense
Cranial Nerves
Twelve pairs of cranial nerves originate
from the brain
Cranial Nerves
Some cranial nerves (I, II, VIII) contain
only sensory fibers and are called
sensory nerves
Cranial Nerves
The rest are mixed nerves because they
contain both sensory and motor fibers