LESSON 5 (A) Flashcards
CNS consists of:
brain
spinal cord
- consists of either nerve cell bodies, dendrites, axon terminals, bundles of unmyelinated axons and neuroglia
gray matter
- aggregations or bundles of myelinated and unmyelinated axons located in the brain and spinal cord
white matter
- cranial bones (brain), vertebral column (spinal cord)
bony covering
- spinal meninges; cranial meninges
- fibrous connective tissues that cover the brain & spinal cord
- provide support, protection, nourishment to the brain & spinal cord
meninges
3 meninges:
dura mater
arachnoid mater
pia mater
- hard mother
- outermost layer
- very tough membrane
dura mater
- the delicate membrane lying beneath the dura
- spongy, web like structure, thus covering the brain more loosely;
- has no blood supply
arachnoid mater
- nnermost layer;
- VASCULAR membrane having many small plexuses of blood vessels
- layer that keeps the brain & it extends into every
fold of the brain surface
pia mater
the 3 spaces:
- epidural
- subdural
- subarachnoid
- space located above the dura mater (seen in the
spinal cord)
epidural space
- space beneath the dura mater
subdural space
- space beneath the arachnoid layer
subarachnoid space
- clear & colorless liquid that protects the brain
and spinal cord against chemical and physical injuries
cerebrospinal fluid (CSF)
CSF is continually produced by
choroid plexus
- network of capillaries (MICROSCOPIC BLOOD
VESSELS) in the walls of the ventricles
choroid plexus
- These capillaries are covered by EPENDYMAL CELLS
(line the fluis-filled cavities of the brain) that form CSF from blood plasma
through the processes of FILTRATION & SECRETION
choroid plexus
total volume of CSF in adult
80-150 ml
CSF pressure
120-180 mm of H20/ 0-10mmHg
CSF composition:
- composed primarily of water
*Glucose
*Proteins
*lactic Acid
*Urea
*Cations (Na, K, Ca, Mg ions)
*Anions (Chloride ions and Bicarbonate ions)
*some white blood cells
main function of CSF
- mechanical protection
- chemical protection
- circulation
- CSF serves as a shock-absorbing medium that shields the delicate tissues of the brain & spinal cord, from blows that would otherwise cause
them to hit the bony walls of the cranial cavity and vertebral canal. The fluid also
buoys the brain so that it “floats” in the cranial cavity.
mechanical protection
- It provides an OPTIMAL CHEMICAL ENVIRONMENT for accurate neuronal transmission of signals.
chemical protection
- CSF is a medium of EXCHANGE of nutrients from the blood & metabolic waste products from the nervous tissues.
circulation
cavities in the brain that communicate with each other with the central canal of the spinal cord & the subarachnoid space
- ventricles
ventricles:
- 2 lateral ventricles
- third ventricle
- fourth ventricle
- narrow oval opening thru which each lateral ventricle communicates with the 3rd ventricle
*Interventricular foramen – FORAMEN OF MONRO
interventricular foramen
- foramen monro
- opening of the roof of the 4th ventricle thru which it communicates with the 3rd ventricle
*Cerebral Aqueduct /AQUEDUCT OF SYLVIUS
cerebral aqueduct
- aqueduct of sylvius
one median aperture
foramen of magendie
2 lateral apertures
foramen of luschka
- the fingerlike projections of the arachnoid membrane that project into the epidural venous
sinuses, especially the superior sagittal sinus
arachnoid villi
Most of the fluid is absorbed into blood vascular sinus called
superior sagittal sinus
supplies the brain with blood
circle of Willis/cerebral arterial circle
an arrangement of blood vessels at base of brain called
circle of Willis/cerebral arterial circle
the Circle of Willis is formed by the interconnection of the following arteries
- Posterior Cerebral Artery
- Anterior cerebral artery
- Internal carotid artery
- Middle Cerebral artery
- Posterior Communicating artery
- Anterior communicating artery
SPECIAL CHARACTERISTICS OF THE Circle of Willi
- ability for collateral blood flow
- ability for autoregulation
- ability to respond to biochemical changes
- The circle is a structure credited for its ability to
compensate for reduced blood flow from anyone of the major contributors.
ability for collateral blood flow
- the brain is able to autoregulate its blood flow to
respond to changes in intraluminal pressure
ability for autoregulation
- Increased CO2 content –causes notable VASODILATION of cerebral vessels to
increase O2 perfusion.
ability to respond to biochemical changes
- thickening of the walls of the
arteries)
arteriosclerosis
- the brain utilizes about ___ of the body’s oxygen supply
20%
Any _______ can result in weakening,
permanent damage, or death of brain cells
interruption of the oxygen supply
_________ may produce mental confusion, dizziness,
convulsions, and unconsciousness
glucose deficiency
- permits passageway of essential nutrients (glucose, O2, ions) excluding large
- molecules such as CHON molecules & peptides (long chains of amino acids)
- Inhibits potentially harmful substances and pathogens from entering the brain
BLOOD BRAIN BARRIER (BBB)
*SUBSTANCES THAT PASS RAPIDLY:
-Glucose, O2 & certain ions
*SUBSTANCES THAT PASS QUITE SLOWLY
-creatinine, urea, chloride, insulin, sucrose
*SUBSTANCES THAT DO NOT PASS AT ALL:
-CHON & most antibiotics
most complex and largest mass of the nervous tissue
brain
brain weighs about ___ of the TBW
2%
- utilizes ___ of the O2 supply of the body
20%
- receives ___ to ___ of the cardiac output
15-20%
- utilizes ___ to ___ of glucose in the body
65-70%
brain grows rapidly up to ___ year of life
5th
brain stops growing after
20
4 main parts of the brain
- brainstem
- diencephalon
- cerebrum
-cerebellum
-consists of the Medulla Oblongata, Pons & Midbrain
-connects the spinal cord to the remainder of the brain
brain stem
- most inferior part of the brainstem
medulla oblongata
- The medulla starts at the foramen magnum and extends to the inferior border
of the pons, a distance of about
3 cm/1.2 inches
medulla oblongata contains the vital centers for:
- cardiac control (HR)
- Respiratory control (MRA)
- regulates the rate and force of the heartbeat
and the diameter of blood vessels
cardiac control
- it contains the MRA/Medullary Rhythmicity Area
respiratory control
- adjusts the basic rhythm of breathing
inspiratory and expiratory areas
- In the medulla oblongata are bulging protrusions at its anterior portion known
pyramids
Most of the axons of the PYRAMIDS cross to
the opposite side & this crossing over forms the
DECUSSATION OF PYRAMIDS
Function: regulates Heart Rate, blood vessel diameter, breathing, swallowing, vomiting, coughing, sneezing, balance & coordination
medulla oblongata
- located immediately superior to the MO
pons
- means “bridge”, serves as a functional bridge bet the cerebrum & the cerebellum
pons
- it is anterior to the cerebellum and is about ___ cm
2.5 cm/1 in. long
pons contains ________ and _____ which maintain the rhythm of respiration
pneumotaxic and apneustic areas
These areas do not generate primary rhythm for respiration but rather act as
- modifiers
- These areas do not generate primary rhythm for respiration but rather act as MODIFIERS of the rhythm established by the
- rhythmicity area
- transmits inhibitory impulses to the
INSPIRATORY AREA at the M.O.
pneumotaxic area
- sends stimulatory impulses to the INSPIRATORY
AREA at the MO.
apneustic area
major effect of pneumotaxic area
- helps turn-off the INSPIRATORY AREA before the lungs become full of air
major effect of apneustic area
prolonged inspiration
it is called mesencephalon
midbrain
- located superior to the pons
- smallest portion of the brainstem
midbrain
about how long is the midbrain
2.5 cm
- (paired bundles of axons) which relay
motor impulses from the cerebral cortex to the pons & spinal cord
cerebral peduncles
which consists of 4 rounds of colliculi that
are involved in hearing & are integral portion of the auditory pathways in the CNS (2 inferior colliculi) and 2 superior colliculi involved in visual reflexes
corpora quadrigemina
scattered throughout the brainstem
plays an important role in arousal and in maintaining consciousness
thru the sleep & wake cycle
helps regulate muscle tone
alerts the cortes to incoming sensory signals
The broad region where white matter and gray matter exhibit a netlike
arrangement
reticular formation
-part of the brain between the brainstem & the cerebrum
-consists of the Thalamus, Pineal Body & Hypothalamus
diencephalon
-largest part of the diencephalon
thalamus
- serves as the RELAY STATION of sensory inputs from the spinal cord & brainstem
- Influences mood
- Registers an unconscious, unfocalized, uncomfortable perception of pain
- Serves as the interpretation center for sensory impulses such as pain,
temperature, light touch & pressure
thalamus
-located posterior to the thalamus
Functions:
a. an endocrine gland which influences the onset of puberty
b. secretes the hormone MELATONIN (released more during darkness than
during daytime)
pineal body
- it promotes sleep
- it sets of the body’s biological clock or circadian rhythm (the pattern
of each 24-hour period such as temperature and other vital signs)
effects of melatonin
