Warm Up 1/21/11

**Reminder: Muscle Quiz #2 (last two pages of packet) next block day

1. What are the main divisions of the nervous system? (be very general)

2. What components make up these two divisions?

3. What is/are the function(s) of ependymal cells?

4. What is the name of the opening where the spinal cord enters/exits the cranial cavity?

Central Nervous System

Chapter 13

CNS Coverings

• Bone• Meninges

– Dura Mater: white fibrous tissue– Arachnoid membrane: cobweb-like layer– Pia Mater: adheres to outer surface of brain & cord;

contains blood vessels• Spaces surrounding meninges

– Epidural space: (“on the dura”) btwn dura mater and bone coverings

– Subdural space: (“under the dura”) btwn dura mater and arachnoid membrane

– Subarachnoid space: under arachnoid membrane; outside pia mater

http://faculty.irsc.edu/FACULTY/TFischer/AP1/meninges.jpg

Cerebral Spinal Fluid (CSF)

• Protective cushion of fluid

• Brain monitors CSF to help maintain homeostasis– Ex: CO2 levels

• Fluid spaces– Subarachnoid space– Spinal cord– Ventricles (4)

Formation of CSF

• Fluid separated from blood in choroid plexuses– Choroid plexus: network of capillaries that

project into ventricles– Lined with ependymal cells

• Circulation:– Separation in choroid plexuses ventricles

central canal of spinal cord & subarachnoid spaces blood

Diagnostic Study – Lumbar Puncture

• Removal of CSF from subarachnoid space in lumbar region of spinal cord

• Above/below L4, locate iliac crest• Side-lying, knees to chest• Sterile technique• CSF tested for abnormalities

– Blood counts, bacteria, pressure

• Administer diagnostic agents or medications

http://www.nlm.nih.gov/medlineplus/ency/images/ency/fullsize/19078.jpg

Hydrocephalus• Internal hydrocephalus

– Obstruction blocks drainage of CSF from ventricles (1-3)

• Ex: tumor

• External hydrocephalus– Obstruction in subarachnoid space causes build up of

CSF in subarachoid space• Hemorrhage blood clots

• Treatment– Infants

• Unfused sutures cranium swells• Shunt placement btwn lateral and 4th ventricles

– Adults • Pressure compresses brain coma, death

http://www.choa.org/images/graphics/hydrocephalus.jpg

http://bryanking.net/wp-content/uploads/2009/02/national_hydrocephalus_foundation.jpg

http://www.articleslounge.com/wp-content/uploads/2009/06/Hydrocephalus.jpg

Spinal Cord - Structure• Extends from foramen magnum to L1• Two enlargements (bulges)

– Cervical & lumbar• Fissures

– Anterior median fissure (larger) & posterior median sulcus• Nerve Roots – Project from each side of spinal cord

– Dorsal nerve root: carry sensory information to spinal cord• Unipolar neurons• Cell bodies make up dorsal root ganglion

– Ventral nerve root: carry motor information that exits spinal cord– Dorsal + ventral nerve roots = spinal nerve

• Gray matter (“H” in the center of the spinal cord)– Anterior, posterior, lateral horns (or columns)– Interneurons and cell bodies of motor neurons

• White matter (surrounds gray matter)– Anterior, posterior, lateral columns– Bundles of axons (tracts)

Warm Up 1/24/11Reminders:

– Muscle quiz block day this week (1/26 or 1/27)– Cat dissections on block day (wear close toed shoes and pull your

hair back)– Bring your book tomorrow!

Warm Up:1. List the meninges of the CNS from superficial to deep.2. What two other things help protect the brain and spinal

cord?3. Where is CSF formed?4. Where does a lumbar puncture usually take place?5. Your patient has a tumor preventing the circulation of CSF

from the ventricles. What would be this patient’s diagnosis?

Spinal Cord - Functions

Two main functions:

1. Conduction routes to/from brain

2. Integration or reflex center for all spinal reflexes

Spinal Cord – Conduction Routes

• Ascending tracts – conduct sensory impulses up to the brain– Lateral spinothalamic: pain, temperature, crude touch

opposite side– Anterior spinothalamic: crude touch and pressure– Fasciculi gracilis and cuneatus: discriminating touch &

pressure sensations (vibrations, stereognosis, two-point discrimination), conscious kinesthesia

– Anterior & posterior spinocerebellar: unconscious kinesthesia

– Spinotectal: touch that triggers visual reflexes

Spinal Cord – Conduction Routes

• Descending tracts – conduct motor impulses down from the brain– Lateral corticospinal: voluntary movement, contraction

of small muscle groups (hands, fingers, feet, toes of opposite side)

– Anterior corticospinal: same as above but affect muscles on same side

– Reticulospinal: maintain posture during movement– Rubrospinal: coordination of body movement &

posture– Tectospinal: head and neck movement during visual

reflexes– Vestibulospinal: coordination of posture & balance

Spinal Cord – Reflex Centers

• Center of reflex arc

• Switching from afferent to efferent– 3 neuron arc interneuron– 2 neuron arc synapse btwn afferent &

efferent

• Located in gray matter (“H”)

Brain• Consists of:

– 100 billion neurons– 900 billion glial cells

• Weighs approx 3 lbs in an adult• Mature neurons are incapable of cell

division– Only during prenatal and beginning months of

life– Malnutrition hinders neuron

growth/development

Brain - Divisions• Brainstem

– Medulla oblongata– Pons– Midbrain

• Cerebellum• Diencephalon

– Thalamus– Pineal body– hypothalamus

• Cerebrum– Cortex

Brainstem• Medulla Oblongata

– Enlarged extension of the spinal cord – Located just above the foramen magnum– Contains white matter and a network of gray & white

matter called the reticular formation• Reflex centers: cardiac, vasomotor, respiratory

• Pons– White matter & reticular formation– Reflex centers for CN 5-8

• Midbrain– White matter & reticular formation– Reflex centers for CN 3-4

Cerebellum

• Structure– Lower posterior portion of brain– Outer region cortex gray matter– Internal areas white matter– Grooves sulci; raised areas gyri

• Function– Produce skilled movements by coordinating muscle

groups– Posture (unconscious) – Maintains balance

Cerebellar Disease• Diseases of the cerebellum (tumor,

abscess, trauma, hemorrhage) produce abnormalities in muscle coordination

• Most common – ataxia (muscle incoordination)

• Signs/symptoms: – Hypotonia– Tremors– Disturbances in gait & balance

Diencephalon

• Thalamus– Dumbbell-shaped mass of gray matter– Forms walls of third ventricle– Functions:

• Processes auditory & visual input• Conscious recognition of pain, temperature &

touch• Emotional responses (associates sensory

impulses with pleasantness vs unpleasantness)

Diencephalon• Hypothalamus

– Lie beneath thalamus and forms the floor of the 3rd ventricle

– Functions:• Controls responses made by autonomic effectors• Maintains water balance• Endocrine function – release hormones that

regulate actions of the anterior pituitary gland• Waking state (alert and arousal)• Regulating appetite• Maintaining normal body temperature

Warm Up 1/25/11Announcements:1. You need your book – go get it!2. Muscles quiz this Wednesday or Thursday3. Dissections this Wednesday or Thursday – hair back &

closed-toe shoesWarm Up:1. Ascending tracts carry ________ information; Descending

tracts carry ________ information.2. True/False: Conduction routes are symmetrical, meaning

they are found on both sides of the spinal cord.3. Reflex centers can be described as:4. What vital reflex centers are found in the medulla

oblongata?5. Which part of the brain produces emotional responses

associated with sensory impulses?

Diencephalon

• Pineal Body– Located just

above the midbrain

– Functions:• Regulates

biological clock

• Produces melatonin

Cerebrum• Largest, upper division of the brain• Two halves – right & left hemispheres

– Communicate via corpus callosum

• Cerebral cortex – surface of the cerebrum; gray matter– Gyri & sulci (shallow) or fissures (deep)– Frontal lobe, parietal lobe, temporal lobe,

occipital lobe, insula (under lateral fissure)

• Cerebral tracts – white matter beneath the cerebral cortex

Functional Areas of the Cerebral Cortex (fig 13-16)

Functions of the Cerebral Cortex

• Postcentral gyrus – termination area for sensory pathways– Touch,

pressure, temperature, body position

• Precentral gyrus – primary motor area– Neurons in

this area control individual muscles

Functions of the Cerebral Cortex - Consciousness

• Consciousness depends on the proper functioning of the reticular activating system– Reticular formation in the brainstem receives

impulses from the spinal cord – Relays signals to thalamus then to cerebral

cortex– Continual excitement of the neurons in this

system is necessary for a person to remain in a conscious state

Functions of the Cerebral Cortex - Language

• Speech centers are located in frontal, parietal & temporal lobes

• In 90% of the population these areas are found in the left hemisphere

• Aphasia = language defects

• Broca’s area – unable to articulate words; able to make vocal sounds

• Wernicke’s area – deficit in language comprehension

Functions of the Cerebral Cortex - Emotions

• Experiencing and expressing emotions involves the function of the limbic system– Area of the brain that surrounds the corpus callosum – For proper expression the limbic system functions with the

cerebral cortex

Functions of the Cerebral Cortex - Memory

• Temporal, parietal and occipital lobes

• Limbic system also plays a role– Removal of hippocampus inhibits a person

from recalling new information

Disorders of the Central Nervous System

Cerebrovascular Accident (CVA)

• Aka Stroke• Hemorrhage or cessation of

blood flow through cerebral blood vessels

• Lack of oxygen to neurons causes cell damage or death

• If motor areas are affected, patient loses function on opposite site of the body– (motor neurons cross over from

side to side in the brainstem)• Hemiplegia – paralysis (loss

of voluntary muscle control) on one whole side of the body

http://www.strokegenomics.org/img/stroke_hem_web.jpg

Cerebral Palsy

• Permanent, non-progressive damage to motor control areas of the brain

• Damage present at birth or shortly after birth; remains throughout life

• Possible causes:– Prenatal infection, trauma to head before/during/after

birth, reduced oxygen supply to brain

• Results in impairment to voluntary muscles• Most common spastic paralysis: involuntary

contractions of affected muslcles

Dementia

• Dementia: degeneration of neurons that affect memory, attention span, intellectual capacity, personality & motor control

Alzheimer’s Disease (AD)

• Lesions develop in the cortex of the brain

• Result is dementia

• No known cause; no effective treatment

• Genetic basishttp://www.crystalinks.com/alzheimersbrain.jpg

Seizures• Sudden bursts of abnormal neuron activity that

cause temporary changes in brain function• Mild seizures

– Small changes in level of consciousness, motor control & sensory preception

• Severe seizures– Convulsions (jerky, involuntary movements) &

sometimes unconsciousness

• Treatment– Drugs (phenobarbital, valproic acid) block

neurotransmitter activity in affect areas inhibits bursts of explosive neuron activity

http://theness.com/neurologicablog/?p=27