Download The Nervous System 9.14 Brain

The Nervous System
9.14 Brain
Zahraa A.
Rima S
2nd hour
Content objective: SWD understanding of
section 9.14 dealing with the human brain
Language objective: SWD understanding of
the human brain by listening, taking notes,
filling in work sheet, and participating in a
game
NOTE: Worksheet will be collected and graded
for 10 formative points
Introduction
Composition: The brain is made up of 100 billion multipolar neurons
Function: neurons communicate with each other and other neurons in various parts
the nervous system
Division: 4 parts
1.
2.
3.
4.
The cerebrum
The diencephalon
The brain stem
The cerebellum
1.
The cerebrum: biggest part
composition: includes nerve centers that
deal with sensory and motor functions.
Its also provides higher mental functions
ex: memory and reasoning
2. The diencephalon: process
sensory information
3. The brain stem: contains nerve
pathways that connect different parts
of the nervous system,and control
specific visceral activities
4. The cerebellum: includes
centers that coordinate voluntary
muscular movements
Structure of the Cerebrum
Composition of the cerebrum:
1.
Cerebral hemispheres: 2 large masses refers to a
the left and right cerebral hemispheres
2.
corpus callosum: a deep bridge of nerves that
connect the cerebral hemispheres
3.
dura mater: Thick, outermost layer of the meninges
surrounding and protecting the brain and spinal cord
4.
gyri: ridges located on the surface of the cerebrum,
composed of single gyrus separated by grooves
A.) sulcus: shallow groove
B.) fissure: deep groove
Examples of distinct patterns formed in brain
1.
2.
Longitudinal fissure:deep groove
that separates the left and right
cerebral hemisphere
Transverse fissure:deep groove that
separates the cerebrum from the
cerebellum
sulci divides each hemisphere into lobes
Lobes of the cerebral hemisphere
lobes name is based on the bone the underlie
1.
2.
Frontal lobe: forms the anterior portion of each cerebral
hemisphere. Its posteriorly bordered by the central
sulcus. The central sulcus extends from the lateral
fissure at a right angle. It inferiorly extends by a lateral
sulcus which extends from under the brain's surface
along its sides
Parietal lobe: located behind the frontal lobe and is
separated by the central sulcus
3. Temporal lobe: located under the frontal
and parietal lobe and is separated by the
central sulcus
4. Occipital lobe : forms the lower part of
each cerebral hemisphere and is separated
from the cerebellum by a shelf like extension of
dura mater.
5. Insula: located deep within the lateral
sulcus and is covered by portions of frontal,
parietal, and temporal lobes. Insula is
separated from other lobes by a circular sulcus.
Lobe overview
Cerebral cortex
Cerebral cortex: thin layer of grey matter
located on the outer most portion of the
cerebrum.
A.
B.
The layer covers the gyri and it dips into
the sulci and fissures.
It contains 75% of neuron cells bodies in
the nervous system
White matter
White matter: composed of bundles of myelinated
axons located under the cerebral cortex.
A.
B.
C.
D.
This matter connects neuron cell bodies of the
cortex with other parts of the nervous system
makes up the mass of the cerebrum.
Some the fibers pass from one cerebral
hemisphere to another by the way of the
corpus callosum
Other fibers also carry sensory or motor
impulses from parts of the cortex to nerve
centers in the brain or spine
Functions of the Cerebrum
The cerebrum:
1.
2.
3.
4.
5.
Provides higher functions of the brain
Contains centers for interpreting(viewing) sensory impulses coming from
sense organs.
contains centers for starting voluntary muscular movement.
stores information that make up memories used for reasoning
Activity originates (forms) intelligence & personality
Functional Regions of the Cerebral Cortex
1. Motor area:
a.
b.
c.
d.
e.
part of cerebral cortex, found in frontal lobes.
Type of nerve tissue: pyramidal cells/ upper motor neurons = Signal =>
lower motor neurons.
Axons crisscross along the two hemisphere of the brain. (that’s why the
left side of brain controls the right side of body).
Ex: Frontal eye field - eye and eyelid, voluntary movement.
Other part control hand and finger movement.
Functional Regions of the Cerebral Cortex
2. Sensory area:
Responsible for feelings and sensation by interpreting impulses. Like the
motor fibers, the right side is controlled by the left hemisphere and vise versa.
Interpretes the 5 senses:
●
●
●
●
●
Cutaneous
Visual
Auditory
Taste
Smell
Functional Regions of the Cerebral Cortex
3.
Association areas:
a.
b.
c.
d.
e.
Processing unit- memory, emotions, perception, cognition, etc..
Located at the anterior of frontal lobes, in lateral area of parietal,
temporal, occipital lobes.
Helps with planning, solving, speech, expressing of emotion.
Language and speech: (left hemisphere)
i. Sensory speech area/ Wernicke’s area. (parietal lobe)
ii. Motor speech area/ Broca’s area. (frontal lobe)
Recognition and memory- one or more sensory areas are used to create
patterns. (ex: smelling a certain food, and imagining it visually, or tasting
it)
Hemisphere Dominance
●
In most people, dominant hemisphere is a side of the cerebrum that controls
understanding and using language. (usually left, some people have right
dominance, and some have both).
●
Non dominant hemisphere would control nonverbal communication (body
language), musical and visual patterns, and emotions.
●
The two are connected by nerve fibers of corpus callosum. They allow
communication between, transfer of info. Dominant controls non dominant,
and nondominant sends info to dominant to make decisions.
Hemisphere Dominance
●
Basal nuclei: masses of gray
matter, the caudate nucleus, the
putamen, and the globus
pallidus. ‘relay stations’ for
motor impulses, or modify their
pattern which helps conscious
muscle movement. Respond to
dopamine (inhibitor).
Ventricles in the brain are cavities filled cerbronspinsol fluid
Ventricles & Cerebrospinal Fluid
Ventricles
1.
Series of interconnected cavities located within the cerebral hemispheres
and brainstem.
A. Lateral ventricles
1. Is the largest ventricle,
2. extending into the cerebral hemispheres,
3. taking over parts of the frontal, temporal, and occipital
lobes.
B. Third ventricle
1. located in the midline of the brain under the corpus callosum.
2. communicates with the lateral ventricles through openings in front of its
end
C.
The fourth ventricle
1.
D.
Located in the brain stem, in front of the cerebellum.
Cerebral aqueduct
1.
2.
A narrow canal that connects the fourth ventricle to the third
ventricle
Passes through the brainstem
E. The fourth ventricle continues with the central canal of the spine and
contains openings in its roof leading to the subarachnoid space of the
mennings.
Choroid plexuses and cerebrospinal fluid
A. Choroid plexuses : Tiny, reddish, cauliflower like
mass of specialized capillaries from the pia mater
B. Choroid plexuses projects into the ventricles &
secretes cerebrospinal fluid
which is formed in the
lateral ventricles
C. cerebrospinal fluid slowly circulates (flows) into
the third and fourth ventricles and into the spinal
cord's central canal.
D. Cerebrospinal fluid enters subarachnoid spaces of
the mennings through the fourth ventricle wall near the
cerebellum this causes the fluid to completely surround
the brain and spinal cord.
E. organs (brain and spine) that float in the fluid are
protected because the fluid absorbs any forces that
could potentially damage the organs
F. It completes its circulation by being absorbed into
the blood.
G. Cerebrospinal fluid maintains a stable ionic
concentration in the central nervous system and also
provides a path for wastes
Diencephalon
Diencephalon: Between cerebral hemispheres and
superior to the midbrain. Composed of gray matter.
●
●
Thalamus: within Diencephalon. Receives all sensory impulses, and directs
them to appropriate areas. Produces awareness of some sensations (temp.,
touch, pain)
Hypothalamus: region of diencephalon, includes many nuclei (gray matter).
Maintains homeostasis (by connecting nervous w/ endocrine system).
○
○
○
○
○
Heart rate & blood pressure
Water & ion balance
Hunger & body weight. + digestive system activities
Production of neurosecretory molecules (regulate pituitary gland)
Sleep cycle
Diencephalon
●
Limbic system: hypothalamus, thalamus, & basal nuclei. Controls actions
based on emotions. Sences dangerous physical & physiological conditions.
Increase survivability by changing behavior based on mood.
Other parts of Diencephalon:
●
●
●
●
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Optic tracts & optic chiasma: formed from optic fibers crossing over.
Infundibulum : attaches pituitary gland.
Posterior pituitary gland: bottom of hypothalamus.
Mammillary bodies: behind infundibulum.
Pineal gland: upper portion of diencephalon.
Brainstem
A.
Brainstem: bundle of nervous tissue that connects the cerebrum to the spinal
cord.
B.
It contains an abundant track of nerve fibers and a few nuclei.
C.
Parts of the brainstem include
1.
The Midbrain
2.
Pons
3.
Medulla oblongata
1. Midbrain
A.
Midbrain: Small section of the brainstem
B. Located between the diencephalon and the
pons.
C. It contains bundles of myelinated axons that
bring together the lower part of the brainstem and
spinal cord with higher parts of the brain
D. Corticospinal tracts: 2 bundles of axons,
located on the underside of the midbrain. They
function as the main motor pathways between the
cerebellum and the lower part of the nervous Fun fact: the Corticospinal tracts
carry voluntary impulses from the
system
brain to your skeletal muscles
E. The midbrain include masses of grey
matter that works as reflex centers.
Example #1: the midbrain has centers for
specific visual reflexes that include
1.
Centers responsible for moving your
eyes to see something while your head
turns
Example #2: the midbrain also has auditory
reflex centers that include
1.
Centers that you to move your head to
hear sounds clearly.
Brainstem- Pons
A.
Rounded bulge
B.
Located on the underside of the brainstem
C. It separates the midbrain from the medulla
oblongata
D. The dorsal part of the pons mostly contains
large longitudinal nerve fibers that rely on nerve
impulses from and to the medulla oblongata and
the cerebellum.
E. The ventral part of the pons has large bundles
of transverse nerve fibers that transmit impulses
from the cerebrum to centers in the cerebellum
Nuclei functions of pons
Some nuclei of the pons rely on sensory
impulses from the peripheral nerves to higher
brain centers.
Other nuclei function with center of the
medulla oblongata to maintain a stable
breathing rhythm.
Brainstem- Medulla Oblongata
A. Medulla oblongata: is Part of the brain stem,
located between the pons and spinal cord.
1.
Its dorsal (behind/lower) surface forms the floor of
the fourth ventricle.
2.
Its ventral (front) surface is marked by the
crossing over of corticospinal tracts
B. Because of the location of the medulla oblongata
the ascending(arising) and descending (plunging)
nerve fibers that connect the brain and spine must
pass through
Nuclei function within the medulla oblongata
A. white matter of the medulla oblongata surrounds a central mass of grey
matter.
B. “Nerve fibers separate the grey matter into nuclei which then rely on
ascending impulses to the other side of the brainstem and then onto higher brain
centers” (book page 242)
C. Other nuclei of the medulla oblongata control important visceral (deep)
activities including
1.
2.
3.
Cardiac center
Respiratory center
Vasomotor center
1. The cardiac center
The cardiac center: impulses
that originate in the cardiac
center are transmitted onto the
heart on peripheral nerves
changing heart rate.
2. Respiratory center
Respiratory center: adjusts
the rate and depth rate of
breathing by acting with the
pons to keep a stable
breathing rhythm
3. Vasomotor center
Vasomotor center : special cells initiate
(begin) impulses that travel (move) to
smoothe muscle in the walls blood
vessels that stimulate them to contract.
A. Vasoconstriction: Blood
pressure is raised due to constriction of
blood vesicles
B. Vasodilation: Vasomotor center
cells that produce dilating blood vessels
causing blood pressure to drop.
Brainstem- Reticular Formation
Reticular formation: network of nerve fibers. From the top of the spinal cord to
the diencephalon. Joins nerve fibers of major areas with the ascending &
descending tracts. When it senses impulses, it ‘wakes up’ the cerebral cortex.
(no activity in reticular formation = sleep).
When it’s damaged, a person becomes unconscious (comatose). Caused by
severe accidents, or drugs that negatively affect CNS.
Brainstem- Cerebellum
Cerebellum: found below occipital lobes, and posterior to pons.
Made of 2 hemispheres separated by layer of dura mater + connected by vermis.
Mostly white matter, w/ some gray matter on surface → Cerebellar cortex.
Cerebellar peduncles - 3 pairs of nerve traces that helps cerebellum communicate
w/ CNS.
1.
2.
3.
Inferior peduncles- joints & limbs to cerebellum.
Middle peduncles- move signals from cerebral cortex to cerebellum.
Superior peduncles- sends signals from cerebellum to midbrain.
Brainstem- Cerebellum
Cerebellum coordinates skeletal muscle
movement + maintains posture.
If damaged, then tremors develop,
inaccurate movement of muscles, losing
muscle tone & equilibrium.
Summary
Brain is composed of 4 parts:
●
The cerebrum: 4 lobes: Parietal, Temporal, Occipital, Insula lobe. (motor,
sensory, association areas)
●
The diencephalon: Thalamus (Produces awareness), Hypothalamus
(maintain homeostasis).
●
The brainstem: bundle of nervous tissue that connects the cerebrum to the
spinal cord. Has 3 parts: The Midbrain, Pons, Medulla oblongata
●
The cerebellum: coordinates skeletal muscle movement & maintains posture
Class question!
1.
What are the major 4 parts of the brain?
2.
What are the 3 functions of the Cerebral Cortex?
3.
What are two of the many functions of the Hypothalamus?
4.
What are the 3 parts of the brainstem?
Brain review game
Directions: come up and label each empty part. If
you get the answer correct you’ll get candy!
Look on page 235 for reference
#1
#2
#3
#6
#4
Word choices
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#5
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#7 ●
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#8
Spinal cord
Corpus
callosum
Cerebellum
Diencephalon
Brainstem
Skull
Cerebrum
menings