Download BRAIN ANATOMY Central Nervous System (CNS) is the brain and

BRAIN ANATOMY
Central Nervous System (CNS) is the brain and spinal cord. The brain and spinal cord
are so critical. The brain is the executive of you; and, it is as critical as the heart. It is so
important to protect your brain; hence, the brain and spinal cord are protected by bone.
They are encased in the skull and the vertebrate in the spine.
Peripheral Nervous System (PNS)are the nerves that emanates out of the spinal cord or
go into the brain or spinal cord. PNS is composed of the Somatic Nervous System (SNS)
and the Autonomic Nervous System (ANS).
1. Somatic Nervous System is made up of sensory nerves and motor nerves.
Sensory nerves bring in sensory information (vision, smell, touch, taste and hearing.
Motor refers to movement or muscles. Motor nerves are nerves that send information
to the muscles. Motor nerves make voluntary movements.
2. Autonomic Nervous System, however, is in-charge of involuntary functions such as
breathing, digestion and other internal organs. Functions that happen automatically
such as pupil constriction or dilation, breathing, digestion, etc.
The two branches of autonomic nervous system:
a. Sympathetic Nervous System (SNS) – activates most of the functions mentioned
above. It is activated during fight or flight situations. When one is in an
emergency or stressful situation or confronted with threat, it will activate your
sympathetic NS; hence, your perspiration is increased, breathing increases, blood
pressure goes up, etc. SNS are functions which consumes energy to fuel your
muscles so you can either fight or run from the threatening situation. It
suppresses digestion, so the resources that would normally go to digestion is
diverted away from digestion, and directed to other sympathetic functions instead.
b.Parasympathetic Nervous System (PSNS) – when you’re done with the fight or
flight situation, PSNS helps you calm down and recover. It helps slow heart rate,
drops blood pressure, constrict pupil, etc. PSNS is mostly in-charge with
digestive system. It is concerned with conservation of energy which will be
needed later (during the fight or flight situations). Generally PSNS and SNS work
in opposition, (when one is active the other is inactive). Examples of situations of
activation of SNS: stage fright or speaking in public; roller coaster ride; watching
a scary movie; stressful or tension-filled situations; wherein the muscles tensed,
pupil dilate, heart rate increased, blood pressure goes up. While PSNS stores
calories, carbohydrates and proteins for use in times like mentioned above.
Nucleus (nuclei for plural) vs. Ganglion (ganglia for plural)
The cluster of cells in the Central Nervous System are called Nuclei, while
The cluster of cells in the Peripheral Nervous System are called Ganglia.
Sulcus (sulci for plural) vs. Gyrus (gyri for plural)
In the dorsal view of the cortex, gyrus, sulcus and fissure were shown.
Sulci are valleys or fold, or groove in the cortex. Deep valley is called a fissure.
Gyri are ridges on the cortex.
The fissure that bisects the cortex is called the longitudinal fissure, that is why we
have the right and left hemisphere which are lateralized. The right hemisphere
controls the left side of the body while the left hemisphere controls the right side of
the body.
In the sagittal view of the cortex, the Central sulcus which is the major groove going
down the center and another fissure called the lateral fissure were shown.
Two-thirds of the cortex is contained within the sulci; hence, majority of the surface
of the cortex is not visible.
Tracts vs. Nerves
Neuro fibers are bundles of axons.
Tracts are bundles of axons in the Central Nervous System, while
Nerves are bundles of axons in the Peripheral Nervous System.
Gray matter vs. White matter
Gray matters are densely packed of cell bodies and dendrites, while
White matters are mostly of myelinated axons.
Corpus Callosum connects the left and right hemispheres in very large bundles of
axons. Generally we understand that it is the opposite hemisphere that controls the
contralateral side of the body, so there must be some communication between the two
hemispheres. It is in the corpus callosum where the crossover happens.
Different areas of the brain
The brain stem is right after the spinal cord. It starts from the medulla all the way up
to the thalamus. The structure below the cortex are the subcortical structure. The
cortex is so overdeveloped in our species that it actually kind of flows over the other
structures. The lower structure starts with the hindbrain.
Major Division of the Brain :
1. Forebrain
2. Midbrain
3. Hindbrain
HINDBRAIN has 3 major structures:
1. Medulla which is responsible for vital functions and vital reflexes including
breathing, heart rate, vomiting, salivation, coughing and sneezing. Medulla is
crucial to your survival. Damage to the medulla is mostly fatal and too much
opiates slows down medulla activities and could lead to death.
2. Dorsal and superior to medulla are the Pons, which are involved in sleep and
dreaming. This is another area like the corpus callosom where the sensory
neurons and motor neurons cross over to the opposite side of the brain. Many
axons from the pons cross from one side of the brain to the other.
3. Posterior to pons is the Cerebellum which is responsible for controlling
movement (balance, coordination, timing and rhythm )
There is a nucleus that spans from the medulla up to the midbrain and a little bit
of thalamus called the reticular formation also known as reticular activating
system and is generally responsible for alertness, attention and arousal.
MIDBRAIN which is superior to hindbrain has 2 major divisions:
1. Dorsal is the Tectum (latin for “roof”). Tectum has 4 major bumps on it. The 2
on top are called superior colliculi, and the 2 below are called inferior colliculi.
The superior colliculi receives visual information and helps you orient where
things are in space. Inferior colliculi receives auditory information and helps to
orient where that sound is coming from.
2. Under the tectum lies Tegmentum (latin for “floor’). It has structure called
substantia nigra (greek for black substance). It is important because it is a
nucleus in the brain that creates dopamine and then gets projected to basal
ganglia for movement pathway. There are different dopamine pathways and
this is one. As in Parkinson’s disease where there is difficulty initiating
movement, speech impairment, and rigidity in muscles).
FOREBRAIN
Limbic system is a collection of structures that are generally responsible for
emotion, memory and smelling.
1. Amygdala the almond-shape structure involved on processing emotional
information.
2. Hippocampos involved in storing and consolidating new and short term
information .
3. Olfactory bulb
4. Hypothalamus
Basal ganglia includes 3 major structures each linking the thalamus and all
involved in movement, they are:
1. Caudate nucleus
2. Putamen
3. Globus palidus
LOBES OF BRAIN
1. Occipital lobe which is located at the very back of the brain and processes
visual information.
2. Frontal lobe which contains the primary motor cortex and the prefrontal
cortex, extends from the central sulcus to the anterior limit of the brain . The
posterior portion of the frontal lobe just anterior to the central sulcus is the
precentral gyrus specialized for the control of fine movements, such as
moving one finger at a time.
3. Temporal lobe is the lateral portion of each hemisphere which is responsible
for auditory information and also some visual information.
4. Parietal lobe is between the occipital lobe and the central sulcus. It has very
important strip of gyri, the somatosensory cortex. The parietal lobe biggest
function is for somatosensory, meaning sensations from the body such as
tactile, temperature, pressure, as oppose to sensation of hearing.
Motor cortex vs. Somatosensory cortex
Motor cortex cellular representation means that the areas that have more muscles
has greater representation in the motor cortex. For example, the face has more
muscles, so it has greater representation in the motor cortex which make it
possible to do a lot of facial expressions necessary for human
interaction/relationships.
Somatosensory cortex is located just posterior to central sulcus, and like the
motor cortex, areas that are more sensitive has more representation in the
somatosensory cortex. For example, fingertips are more sensitive as opposed to
toes or back; hence, have more representation in the somatosensory cortex.
Prefrontal cortex the most anterior portion of the frontal lobe, has executive
functions or higher order functions:
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ability to plan
ability to inhibit
abstract thinking
working memory
sequencing
set shifting