Download The Brain

Cerebrum:
The major parts of the
voluntary
Brain…..
Frontal Lobe
• The frontal lobe begins at the central
sulcus and extends down to the top
of the lateral sulcus.
• It is the largest lobe of the brain and
is protected by the frontal bone.
Frontal Lobe cont’d…
• The frontal lobe is the part of the
brain that contains our:
– Personality
– Morals and ethics
– Ability to form words for speaking
– Skeletal muscle movement (voluntary)
The frontal lobe is the OUPUT
center of the brain.
Pre-Central Gyrus
• The gyrus located just in front of the
central sulcus and has been
“mapped” so that we know what part
of the brain instructs that particular
part of the body’s voluntary muscles.
Parietal Lobe
• The parietal lobe is the major INPUT
lobe.
• It is the “files” of our hardrive or
memory. The more often the
memory is enforced through
repetition the “linked” up the memory
becomes. Short-term memory
hasn’t had enough repetition to stay
“filed” and can be lost quickly.
Parietal Lobe cont’d…
Many memory problems can be seen
in the elderly or people with
Alzheimer’s. One common problem
occurs when a patient can
remember what happened when
they were five, but can’t seem to
remember what they had for lunch.
As the brain deteriorates, more longterm memory files are broken down.
Parietal Lobe Cont’d…
• Short-term memory problems can
also be seen in head injury patients.
They may recover reading, writing,
speech, and motor skills, but they
struggle in school because the brain
can not seem to hold the short term
lesson of the class long enough to
be able to reinforce it.
Parietal Lobe cont’d…
• Other major functions of the parietal
lobe…
– Understanding speech (Broca’s area)
– Recognition of objects, people, places,
and events
– Memory of events and outcome of
choices (files for the hard drive)
Post-Central Gyrus
• The gyrus located just posterior to
the central sulcus has been
“mapped” so that we know what part
of the brain receives input from
what particular part of the body.
Post-Central Gyrus Cont’d…
• Sensory Homunculus…
– Notice how some of the body part are
larger than others. The larger the
body part drewn on that part of the
brain, the MORE brain area used for
that part!
• This is why some areas of the body are
more sensitive than others.
• Ex. Allergy testing: The back is not one of
the most sensitive areas, so testing here is
less annoying to the pt.
Occipital Lobe
• The occipital lobe is located in the
back of the brain.
• Do you see with your eyes OR do
you see with your brain?
Occipital Lobe Cont’d…
• The brain is easily fooled….
– Especially the occipital lobe!
• The “cameras” or the eyes are located at the
front of the head (which helps in survival) and
the image is “wired” under the brain, back to the
occipital lobe.
• The occipital lobe receives images upside down
and then breaks patterns down into familiar
items.
– The parietal lobe helps identify these items
with the use of language.
Temporal Lobe
• The temporal lobe is located under
the parietal and frontal lobes on the
side of the brain.
• The temporal lobe is responsible for
hearing and balance, it also helps
place an identification with the
sounds that the temporal lobe
“hears”
RECAP…
• Frontal, Parietal, Occipital, and
Temporal lobes of the brain make up
the Somatic or Volumtary Brain.
• The frontal lobe is the only OUTPUT
lobe or motor lobe of the voluntary
brain.
• The parietal, occipital, and temporal
lobes are all INPUT lobes.
The Brain
The Major Parts of the
Involuntary Brain…
Cerebellum
• The cerebellum is located in the back of
the brain under the occipital and temporal
lobes.
• It has very fine and horizontal gyrus.
– The white matter forms a tree known as the
“tree of life” or Arbor Vitae
• Controls coordination…It is much like a
“traffic controller” at an airport.
• It is quite developed (compared to the
cerebrum) at birth and develops as the
infant uses repetitive movements.
Brain Stem: Pons and Medulla
Oblongata
• The Pons: remember the “poochy pons”,
since it “pooches” out from the brain stem
• The M.O. is found under the pons and
exits the skull through the magnum
foramen. It ends at C2.
– Controls breathing and connects the brain to
the spinal cord.
– An injury here can cause quadriplegia and a
quick death if breathing is not aided.
Topics of Discussion:
• Effects of Alcohol
• The real meaning of “brain dead”
Use Your Grey
Matter…
Grey Matter
vs.
White Matter
White Matter….What we need to
know first….
• Nerve cells (Neurons) carry
messages in one direction.
• Most nerve cells have a
oligodendrocyte (Responsible for
insulating the CNS neurons) wrapped
around them. - White Neurons
– Responsible for carrying messages to
and form specific areas of the CNS,
especially to the cortex of the brain.
White Matter cont’d…
• Think of white matter much like
telephone lines going to and from a
house.
– Think of the house as the decision
maker of the brain (cortex)
Cerebral Cortex
• Outer layer of the brain
• Composed of gray neurons
– Unmyelinated
– Carry messages slower
• 1-4 mph…..much slower than white
neurons (250 mph!!!!)
• Choice making occurs here….
– Like “voting”…
• Neurons “vote” and from the voting a
choice is made.
Cerebral Spinal Fluid…. (CSF)
• Functions:
– Supportive, protective cushion
– Reservoir of circulating fluid that, along
w/ blood, the brain monitors for
changes in the internal environment
• Changes in CO2 content of CSF trigger
homeostatic responses in the resp. control
centers of the brainstem that help regulate
the overall CO2 content and pH of the body
Fluid spaces…
• CSF is found in the:
– Subarachnoid space:
• Around the brain and spinal cord
– Ventricles:
• Large, fluid filled spaces w/in the brain
• There are 4:
– Lateral (2) …..meet on the midline…
– Third …. thin vertical pocket of fluid below and
medial to the lateral ventricle
– Fourth….tiny, diamond-shaped space where the
cerebellum attaches to the back of the brainstem
» p.231
Formation of CSF…
• Formation:
– Occurs mainly by separation of fluid
from blood in the choroid plexuses
• Network of capillaries that project from the
pia mater into the lateral ventricle and into
the roofs of the 3rd and 4th ventricles
• Ependymal Cells
– Sheet of cells that cover the CP, and release
CSF into the ventricles
Circulation of CSF…
• Formed by separation of fluid from
bl.in the CP into the ventricles
• Circulates through the ventricles and
into the central canal and
subarachnoid spaces
• Absorbed back into the blood
Statistics……… CSF
• In the average adult there is about
140mL
– 23mL in the ventricles
– 117mL in the subarachnoid space of
brain and spinal cord
• Hydrocephalus
– When CSF is blocked
• Internal: CSF builds up in the ventricles
• External: CSF builds up in the sub.A space
Spinal Cord…The interstate that
connects the brain to the body!
• Structure:
– Lies w/in the spinal cavity
– Extends from the foramen magnum to
the lower border of the L1 (L3 for
infants and young children)
• 45cm (18inches) in the ave. adult body
• Does NOT completely fill the spinal cavity
– Oval shaped cylinder that taper slightly
as it descends and has 2 bulges
• Cervical region
• Lumbar region
Spinal Cord cont’d…
• 2 deep grooves just miss dividing the cord
into symmetrical halves.
– Anterior median fissure (deeper/wider)
– Posterior median sulcus
• 2 bundles of nerve fibers project from
each side of the Spinal cord
– Nerve Roots
• Dorsal nerve root: sensory info. into SC
– Dorsal root ganglion: cell bodies of these
unicellular, sensory neurons make up a small
region of gray matter
Spinal Cord cont’d…
• Ventral Nerve Root: motor info. out of SC
– Cell bodies of these multipolar neurons are in the
gray matter that composes the inner core of the
SC
– Spinal nerves
• The dorsal and ventral nerve roots join
together
• Component of the Peripheral NS
Spinal Cord cont’d…
• Cross Section view
– Gray matter looks like a flattened “H”
• Extends the length of the SC
• Limbs of the “H” are called:
– Anterior horn or column
– Posterior horn or column
– Lateral horn or column
• Consist redominantly of cell bodues of
interneurons and motor neurons
Spinal Cord cont’d…
• Cross Section view
– White matter
• Surrounding the gray matter, is subdivided
in each half of the SC into 3 columns (or
funiculi)
– Anterior
– Posterior
– Lateral
• Each column/funiculus consists of a lg.
bundle of neree fibers (axons) divided into
smaller bundles
– Tracts
Spinal Cord cont’d…
– Tracts cont’d…
» The names of most SC tracts indicate:
1. the white column in which the tract is
located
2. the structure in which the axons that
make up the tract originates
3. The structure in which they terminate
» Example: the anterior spinothalmic tract
The Reflex Arc
How a Stimulus Elicits a
Response
Reflex Arc
• Quick Review….track the sensory
input going into the CNS….
– ascend. Tracts Cerebral Cortex
(interpret/make decisions….grey matter…1-4 mph)
– Decend. Tracts innervate an effector
• Gland, muscle, etc.
But….What happens if we are in danger?
Cont’d.
• The reflex arc is built in and is for
protection. It by-passes the brain to
produce movement to help move the
body out of harms way.
A Knee-Jerk Response
• What happened?
• When the hammer hit the
knee the foot jerked up.
• Why?
http://www.youtube.com/watch?v=qpw31bvoL
pg
• What is the stimulus?
The hammer hits the tendon.
• What is the response?
The muscle contracts, causing
the foot to jerk upward.
http://www.youtube.com/watch?v=qpw31bvoLpg
Other Reflexes
Stimulus
Response
The aroma of your favorite
food
A nasty odor
Salivation
Nausea
A bright light shining in your Pupils get smaller
eye
An insect flying towards your Blinking
eye
How is a Stimulus Detected?
• Some cells are specialized to react to a specific
stimulus. These are called receptors (they receive a
stimulus). The receptor cells of your eyes are
stimulated by light.
The Response
• When the receptor is stimulated, it sends a
message to a part of your body that effects the
correct response. This is called the effector.
How is the Hammer Tap Detected?
• The muscles in your leg
have stretch
receptors. They react
to a change in length of
the muscle. When the
hammer hits the tendon
at the knee, it makes a
muscle in the front of
your thigh longer
(stretches it). That
stimulates the stretch
receptors in that
muscle.
The Knee-Jerk Response
• When the stretch
receptors are
stimulated, they send a
message to the
muscles of your thigh.
• The muscles in the front of
your thigh contract.
• The muscles in the
back of your thigh
relax.
• Your foot jerks.
Change in Muscle Length
• Here is a similar reflex
in the arm, showing
muscle length.
• The weight dropping into
the hand is the stimulus.
Like the hammer tapping
the knee, it stretches a
muscle.
• The response is the muscle
contracting, jerking the arm up.
How the Message Travels From
the Receptor to the Effector.
• Nerve cells (neurons) carry the message from the
stimulated receptors to the correct effectors.
• A sensory neuron carries the message from the receptor to
the central nervous system (the spinal cord and brain).
• A motor neuron carries the message from the central
nervous system to the effector.
• This is a
reflex arc.
Reflex Arcs
• In a knee-jerk reflex arc the
sensory neuron directly
connects to the motor
neuron in the spinal cord.
This is called a simple
reflex arc.
• Follow the sensory neuron
from the spindle (receptor) to
where it connects with the
motor neuron in the spinal
cord.
• Follow the motor neuron to
the muscle (effector).
Reflex Arcs
• In most reflex arcs
the sensory
neuron connects to
motor neurons
through
association
neurons
(interneurons) in
the central nervous
system.
• Note the
interneuron in the
spinal cord.
The Correct Pathway.
• If you put your finger on
a hot stove, what is the
stimulus?
• What is the correct
response?
• Would it help your
finger if the response was
your foot moving?
The Correct Pathway.
• The correct connection
between the sensory neuron
carrying the message from
the receptor and the motor
neuron carrying the
message to the effector is
the work of the interneurons
of the central nervous
system. Making the right
connections is called
integration.
A Conscious StimulusResponse
• We react to all
stimuli in basically
the same way as a
reflex. The
integration just gets
more complex.
• Complex behavior
involves complex
integration in the
brain.
Making the Right Connection
• Integration in the central
nervous system works
like the central
switching office (CSO)
of a telephone system
• When you phone a
friend, the call is not
directly carried by a
wire going from your
phone to your friend’s.
Making the Right Connection
• The wire from your
phone goes to the CSO.
• The CSO connects your
wire to the wire going
between the CSO and
your friend’s phone
(integration).
• Hello.
Review
• When the receptor detects the stimulus, it excites a
sensory neuron.
• The message travels through the sensory neuron to an
interneuron in the central nervous system (labeled
control center).
Review
• The message travels through the interneuron to a
motor neuron.
• The message travels through the motor neuron to the
effector.
• The effector is stimulated and its reaction is the
response.
Name the Neurons
• Neuron 2
Sensory Neuron
Name the Neurons
• Neuron 3
Interneuron
Name the Neurons
• Neuron 4
Motor Neuron
Peripheral
Nervous System
The relationship of communication
between the spinal cord and nerves.
• Nerves are always found in the PNS
(tracts are always pathways on the
CNS)
• Sensory nerves ALWAYS go to the
CNS
• Sensory nerves ALWAYS have a
ganglion to house their nuclei
• Sensory nerves ALWAYS enter the
dorsal horn to pass their messages
along.
The relationship of communication
between the spinal cord and nerves.
• Once the message has arrived at
the spinal cord, it will then travel
along sensory pathways or tracts up
to the brain’s cortex for interpretation
A choice has been made!!!
• The output or motor message once
again travels along motor pathways
or tracts down the spinal cord.
• Once arriving at the area that has
the muscles to carry out the
movements, the message exits the
Motor nerves…
• When a motor nerve “hooks up” with a
muscle it can now tell it when to move, it
is known as innervation.
• The combination of the sensory and
motor nerve wrapped together produces
a structure known as a spinal nerve.
– Because this nerve has both sensory and
motor, it is known as a mixed nerve.
PNS nerves…
• 31 pairs of spinal nerves
– They enter and leave the spinal cord
• Not all nerves enter and leave the
spinal cord, there are 12 pairs of
nerves that enter and leave the brain
only.
– Crainal nerves
PNS nerves…
• Cranial and spinal nerves do not
have the protection of the verebral
column or skull.
• Instead they are wrapped up in CT
much like mms fibers and most of
the time, they hide under mms.,
which protect them from trauma.