a and p lecture 4 Flashcards

Dura mater - a tough
outer covering
 Arachnoid mater - a
spidery layer
 Pia mater - a thin and
delicate layer

continuous with spinal meninges and mirror their structure

Falx cerebri - strong sickle-shaped fold of dura
mater which descends vertically in the longitudinal
fissure and separates the two cerebral hemispheres

Falx cerebelli - small triangular
process that separates the two cerebellar
hemispheres

tentorium cerebelli

Brain tumors are often characterized as supratentorial (above the tentorium) and infratentorial (below the tentorium).  Most childhood tumors are infratentorial, while most adult tumors are supratentorial.

Contains sensory areas for skin senses, vision, hearing, olfaction

Motor areas for voluntary control of movement

Association areas for interpreting sensations, language, thinking, decision making, self-awareness, creativity, and storage of memories

Relays information between the cerebellum or spinal cord and the cerebrum

integrates sensory input

Allows left and right cerebral hemispheres to communicate with one another

A bridge between higher and lower brain centers

Processes all sensory information except olfaction

Relays information to appropriate higher brain center

Contains autonomic centers for heart rate and digestive activities

Relays sensory information to thalamus

Controls heart rate, blood pressure, breathing rate, body temp, food intake

A center of emotions

serves as master biological clock

Coordinates sensory-motor voluntary movement

Stores memory of learned motor patterns

outer rim of gray matter that contains the cell bodies of neurons Cerebral white matter = internal region  Nuclei = gray matter deep within the white matter “Seat of our intelligence”– it’s because of billions
of neurons in the cortex that we are able to
read, write, speak, remember, and plan our
life. During embryonic development, the grey matter
of the brain develops faster than the white
matter - the cortical region rolls and folds on
itself. Ridges (gyri) and crevices (sulci) on the surface of the brain are created in the
cortex during this growth
process

Especially expanded are the frontal lobes
which are associated with higher
(executive) functions such as
 self-control
 planning
 reasoning
 abstract thought
 speech
 emotional outbursts
 motor function

memory
 hearing and language
comprehension

Somatosensory area
 mathematics

Processing visual information

 Primary somatosensory area - receives nerve impulses
for, and consciously perceives the somatic sensations of
touch, pressure, vibration, itch, tickle, temperature (coldness
and warmth), pain, and proprioception (joint and muscle
position)
 Primary motor area - controls
voluntary muscle movements throughout
the body, including those of hands, feet,
arms, legs, face , and tongue.
Association area – concerned
with emotional and intellectual
Processes; involved in recognizing
and analyzing incoming information

Primary somatosensory area receives sensory information from the
body

Primary motor area controls the skeletal muscles
• Premotor cortex coordinates learned motor skills

Communicate with the sensory area, motor areas, and other parts of
the brain to analyze and act on sensory input
• Prefrontal cortex enables us to reason and think

large groove that separates frontal lobe
from parietal lobe

primary
motor area

primary somatosensory
area

large cleft that separates cerebrum
into R & L cerebral hemispheres

a bundle of transverse white fibers
(consisting of glial cells and myelinated axons) that allows for
communication between the R & L cerebral hemispheres

consists primarily of
myelinated axons in 3 types of tracts

contain axons that
conduct nerve impulses between gyri in the
same hemisphere

conduct nerve impulses
between corresponding gyri from one
hemisphere to another

convey impulses to
lower parts of the
CNS (thalamus,
brain stem, or spinal cord

a ring of structures on
the inner border of the cerebrum

plays a primary role in
promoting a
range of emotions, including pleasure, pain,
docility, affection, fear, and anger Together with parts of the
cerebrum, the limbic system
also functions in memory

Vascular endothelium around brain capillaries forms tight
junctions with the end-feet of nearby astrocytes.
 Allows passage of essential metabolites (O2 & glucose) but
prevents passage of larger, hydrophilic materials from the
blood to the cerebrospinal fluid The BBB protects the brain from some harmful substances (like bacteria), but at a cost:
 For one thing, certain molecules needed to meet
metabolic needs (such as glucose) must be actively
transported across the barrier using specific
transport proteins and energy.
 Another aspect of the BBB is that if a brain infection
were to develop, antibiotics (and many other drugs)
have difficulty crossing into the brain tissues and
reaching therapeutic levels (should be lipid soluble
to pass).

Cavities Within the
Brain

Mechanical
Protection
• Shock-absorbing
tissues that
protect delicate
tissues of the
brain
• “buoys” the brain
so it floats in the
cranial cavity
Homeostatic
Function
• pH affects
pulmonary
ventilation and
cerebral blood
flow
• Transport system
for
neurosecretory
hormones
Circulation
• Medium for
exchange of
nutrients and
waste products
• Between blood
and nervous
tissue

The majority of CSF production - 80 to 150 mL at
any given time in an adult - comes from
ependymal cells in the choroid plexuses
(networks of blood capillaries that line the
ventricles).
 The pathway CSF follows from the internal
ventricles to the SAS is given in the following
sequence:
• lateral ventricles  interventricular foramina
 third ventricle  cerebral aqueduct

networks of blood
capillaries in the walls
of the ventricles

3 openings:
one median
aperture &
paired lateral
apertures

Functions:
Origin of many cranial
nerves
Reflex center for
movements of eyeballs,
head, & trunk
Regulates heartbeat
& breathing
Plays role in
consciousness
Transmits impulses

Its white matter contains all ascending and
descending tracts between spinal cord and other
parts of the brain
Contains nuclei
which are
regulators for
vital body
functions
Nuclei are clusters of neuronal
cell bodies in the CNS

Cardiovascular center - controls rate
and force of heartbeat; diameter of blood
vessels
Medullary rhythmicity center – controls
rate and rhythm of breathing
Vomiting, coughing, hiccupping,
deglutition, and sneezing centers
also located here

Pyramids – white matter protrusions found on the medulla
oblongata which are formed by the corticospinal tracts
(motor tracts which conduct nerve impulses controlling
voluntary movements of limbs and trunk.
 Decussation of pyramids - axons from left
pyramid cross over to the right; axons on the
right cross over to the left
 Left hemisphere of brain controls voluntary
movement on right side of body; right
hemisphere controls voluntary
movement on left

"bridge"  connects
spinal cord with brain
 Consists of nuclei and tracts
 Relays nerve impulses related to voluntary
skeletal movements and coordination from
cerebral cortex to the cerebellum
 Contains pneumotaxic center
which controls breathing rate.
 The pontine respiratory group is
normally inactive during quiet
breathing. This group of neurons acts
like an “off-switch” to terminate
medullary inspiratory activity.
Early termination of inspiration leads to
an increase in the rate of breathing

pons to the
diencephalon
Cerebral peduncles (“little feet”) are the main sites through
which tracts extend and nerve impulses are conducted
between the superior part of the brain and the inferior parts of
the brain and the SC

Superior colliculi serve as reflex centers for movements of the head,
eyes, and trunk in response to visual stimuli.
 inferior colliculi serve as reflex centers for movements of the head,
eyes, and trunk in response to auditory stimuli, and also the startle
reflex

little brain”
It is separated from the cerebrum by the transverse
fissure (in which the tentorium cerebelli is located) second largest
part of the brain

Performs 4 Activities:
1. Monitoring intentions for
movement
2. Monitoring actual
movement
3. Comparing command
signals with sensory
information
4. Sending out corrective
feedback

intended movements with what is
happening with skeletal muscles, and regulates posture,
equilibrium, and balance
Damage to the
cerebellum results in
ataxia

Brain structure which is critical for formation of
new memories and spatial orientation
In Alzheimer’s
disease, the
hippocampus
sustains early
damage

to the thalamus,
hypothalamus, and epithalamus

major relay station for most
sensory information to the primary
sensory areas of cerebral cortex
Relays motor information from
cerebellum to primary motor area
of cerebral cortex
Plays role in maintenance of
consciousness

Controls autonomic centers for:
 heart rate
 blood pressure
 respiration
 digestion
 body temperature
 hunger
 thirst
 fight or flight response
 rest and digest response
 emotional & mating behavior

Mammillary bodies
 Two small, rounded
projections that serve as
relay stations for reflexes
related to the sense of
smell
The Diencephalon - Hypothalamus
Infundibulum
 Stalk-like structure
which connects
hypothalamus to
the pituitary gland

Summing waves of different frequency produces
some characteristic, and diagnostic patterns.
 Alpha (10–12 Hz (cycles/sec) waves are present
when awake but disappear during sleep.
 Beta (14–30 Hz) waves are present with sensory
input and mental activity when the nervous
system is active.
 Theta (4–7 Hz) waves indicate emotional stress
or a brain disorder.
 Delta (1–5 Hz) waves appear only during sleep in
adults but indicate brain damage in an awake
adult.

Olfactory nerve

Optic nerve

Moving eyes

3 = occulomotor nerve pupil and eyelid motor

4 = trochlear nerve

6 abducens nerve

Trigeminal nerve - three branches for supplying the face

ophthalmic

maxillary

mandibular

facial nerve - sensory and motor for the face / some taste sensations

Vestibulocochlear nerve - sensory - balance and hearing

damage causes vertigo ataxia nystagmus ringing in ears and deafness

Glossopharyngeal - sensory and motor - some taste

Vagus - organs of thoracic and abdominal cavities - hunger fullness - throat structures - smooth muscle in GI tract

Spinal accessory nerve - entirely motor - supplies somatic motor innervation to the trapezius and sternocleidomastoid muscles to coordinate head movements

Hypoglossal Nerve
 This is a very large nerve (a lot of resources) to be devoted solely to
the tongue
 It takes a lot more coordination than you might guess to chew, talk,
and swallow without injuring our tongue
 Entirely motor

The spinal cord begins as a continuation of the
medulla oblongata (the most inferior portion of
the
brain stem) extending
from the foramen
magnum of the
occipital bone to its
termination as the
conus medullaris
between L1 - L2

Reflex circuits – coordinate &
control rapid reactions to
environmental changes
Gray matter – integrates
IPSPs and EPSPs triggered by
nerve impulses from brain
(motor) and peripheral
nerves (sensory)
White matter – contains
major sensory and motor
tracts (“highways”) to and
from the brain

The spinal cord is oval in shape and slightly
flattened anteriorly and posteriorly.
 Two types of connective tissue
coverings protect the cord
and provide physical stability:
The bony vertebral column
provides the backbone.
The spinal meninges surround
the cord as a continuation of
the cranial meninges that encircle the brain.

Surround & protect
spinal cord and
provide physical
stability
Continuation of
cranial meninges
Filled with
BV that
supply
nutrients
Denticulate
ligaments –
thickenings of pia
mater which
suspend spinal
cord in its dural
sheath

The space between the middle layer of the meninges and
the deepest layer of the meninges
Contains circulating CSF
Serves as cushion to protect spinal cord
Functions as medium through which nutrients are
delivered and wastes removed

A needle is inserted into the epidural space yet
remains superficial to the dura mater

Cervical C4 - T1

Lumbar T9-T12

Conus medullaris
 The spinal cord ends between the
first and second lumbar
vertebrae (the conus medularis).
 Cauda equina
 “horses tail”
 roots of the lower spinal nerves
that angle down alongside the
filum terminale
 Filum terminale -
 extension of pia mater that
extends inferiorly and blends with
the
arachnoid and dura to anchor
the
spinal cord to the coccyx
External Cord Anatomy

Two bundles of axons, called roots, connect
each spinal nerve to a segment of the cord by
even smaller bundles of axons called rootlets.
 The posterior (dorsal) root and rootlets
contain only sensory axons, which conduct
nerve impulses from sensory
receptors in the skin, muscles,
and internal organs into the
central nervous system

posterior is sensory and anterior is motor

Names of tracts are formed by using compound
words that denote the origin of the tract, and the
place where it ends.
 The spinothalamic tract goes from the spinal cord
to the brain – it is an afferent tract.
 The corticospinal tract goes from the cortex of
the brain to the spinal cord – it is an efferent tract.
 The vestibulospinal tract originates from an area
in the brain which you probably don’t recognize;
however, you can recognize the destination in the
spine, and therefore deduce that it is a motor tract

The skin over the entire body is
supplied by somatic sensory
neurons that carry impulses
from the skin into the spinal
cord and up to the brain
 Sensory input to the CNS is
provided via the posterior roots of
one pair of spinal nerves or via
the trigeminal (V) cranial nerve
 The only spinal nerve without a
corresponding dermatome is C1
Dermatomes

Monoplegia = paralysis of one limb
Diplegia = paralysis of both upper limbs or both
lower limbs (if both lower, then also called
paraplegia)
Paraplegia = paralysis of both lower limbs
Hemiplegia = paralysis of the upper limb, trunk,
and lower limb on one side of the body
Quadriplegia = paralysis of all 4 limbs