Transcript Central Nervous System

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 space
– Subarachnoid space: under arachnoid; 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://bryanking.net/wp-content/uploads/2009/02/national_hydrocephalus_foundation.jpg
http://www.choa.org/images/graphics/hydrocephalus.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 1/24/11
Reminders:
–
–
–
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, twopoint 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 1/25/11
Announcements:
1. Muscles quiz this Wednesday or Thursday
2. Dissections this Wednesday or Thursday – hair back &
closed-toe shoes
Warm 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 side 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 basis
http://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
Warm Up 1/26-27/11
• Study quietly for your quiz (last two pages
of packet)
– It is multiple choice with 14 questions, you will
have 20 minutes.
Warm Up 1/28/11
• HAPPY FRIDAY!! 
• Pick up a worksheet from the counter
• Please write “quiz” for the block day warm up
• Warm ups are due today (no sheet = no credit)
Warm Up:
1. A cerebrovascular accident is also referred to as
a…..?
2. What are the 2 main causes of a CVA?
3. If there is damage to Broca’s area, what type of
deficit will this result in?
4. What are 3 possible causes of cerebral palsy?
5. Alzheimer’s disease is believed to be caused by…?