Cerebrum:

The major parts of the voluntaryBrain…..

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 long-term memory files are broken down.

• 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…

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”

• 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.

RECAP…

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 originates3. 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?

• Why?

• When the hammer hit the knee the foot jerked up.

http://www.youtube.com/watch?v=qpw31bvoLpg

• What is the stimulus?

The hammer hits the tendon.

The muscle contracts, causing

the foot to jerk upward.

• What is the response?

http://www.youtube.com/watch?v=qpw31bvoLpg

Other Reflexes

Stimulus Response

The aroma of your favorite food

Salivation

A nasty odor Nausea

A bright light shining in your eye

Pupils get smaller

An insect flying towards your eye

Blinking

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 Stimulus-Response

• 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.