Neuroanatomy Flashcards
What does the CNS include?
Brain, cerebellum, brain stem, and
spinal cord
What does the PNS include, and how is it divided?
– All the components outside the
cranium and spinal cord
– Divided into Somatic Nervous System
and Autonomic Nervous System
What is the Nervous System?
Highly organized communication system
What do cells do?
Cells receive, transmit, analyze, and
communicate information throughout the
body
What are the brain, brain stem, and spinal cord composed of?
composed of two basic types of nerves –
neurons and neuroglia
What are the types of neurons?
afferent (sensory), interneurons, efferent (motor)
What are afferent neurons?
(sensory) responsible for receiving
sensory input from the PNS and transporting it to the CNS
What are interneurons?
connect neurons to other neurons and
organize information received from different sources for
later interpretation
What are efferent neurons?
(motor) transmit information to the
extremities to signal muscles to produce movement
What are neuroglia?
non-neuronal supporting cells that
provide critical services to the neurons
What are the types of neuroglia?
astrocytes, oligodendrocytes, microglia (phagocytes)
What are astrocytes?
provide vascular link to neurons, contribute to
the metabolism of CNS, and regulate extracellular
concentration of neurotransmitters
What are oligodendrocytes?
wrap myelin sheaths around axons in
the white matter and produce satellite cells in the gray
matter (participate in ion exchange between neurons)
What are microglia?
(phagocytes) engulf and digest pathogens and
assist in nervous system repair after injury
What does a neuron consist of?
cell body (gray matter), dendrites, axon (message sending component)
What is a cell body?
(gray matter) synthesizes
proteins, transmits electrochemical
impulses, and repairs cells
What are dendrites?
receives information and
transfers it to the cell body for
processing
What are axons?
(message sending component)
transmits impulses from cell body to
target cells
What are synapses?
connections between the axon of one neuron and the dendrite of another; allow different parts of the nervous system to communicate and influence each other
What are neurotransmitters?
chemicals that transmit
information across the synapse
What do pharmaceuticals do to neurotransmitter activity?
facilitate or inhibit
neurotransmitter activity
What are common neurotransmitters?
acetylcholine, glutamate (excitatory), GABA (inhibitory), dopamine, norepinephrine (ANS)
What is acetylcholine?
used by all neurons that synapse with
muscle fibers, regulates heart rate and other autonomic
functions
What is glutamate?
(excitatory) facilitates neuronal change during
development and destroys neurons after CNS injury
What is GABA?
(inhibitory) exerts influence over interneurons in
the spinal cord
What is dopamine?
influences motor activity, motivation, and
cognition
What is norepinephrine?
(ANS) produces the “flight or fight
response” to stress
What do axons do?
Conducts processed information to other neurons, muscle
cells, or glands
Are axons myelinated?
Axons can be myelinated (insulated) or unmyelinated
Is the myelin sheath continuous?
Myelin sheath is not continuous separated by the Nodes of
Ranvier
What is saltatory conduction?
Electrical impulses jump from one node to the next increasing
the velocity of the impulse
What is white matter composed of?
composed of axons that carry
information away from cell bodies and has high
concentrations of myelin (white appearance)
Where is white matter found?
found in the brain and spinal cord
What does gray matter contain?
contain large number of nerve cell
bodies and dendrites (gray appearance)
Where is gray matter?
covers the entire surface of the
cerebrum (cerebral cortex) and is also present in the
spinal cord
Where does sensory information enter the CNS?
through the
spinal cord or cranial nerves
What forms fiber tracts?
Myelinated axons are bundled together within the
CNS to form fiber tracts
Where does information travel?
Information travels in these fiber tracts from the
sensory receptor to the cortex for interpretation
How are fiber tracts designated?
point of origin
and their point of termination (lateral spinothalamic)
What are the brain and spinal cord protected by?
protected by the skull and
spine and is covered by three layers of membranes
(meninges)
What is the dura mater?
(outer most layer) thick, fibrous connective
tissue that adheres to the skull
What is the arachnoid?
(middle layer)
What is the pia mater?
(inner most layer) adheres to the brain and
contains the cerebral circulation
Where are epidural and subdural space?
epidural space is between the dura matter and the skull; Subdural space is between the dura matter and arachnoid
Where does cerebral spinal fluid bathe and circulate?
bathes and circulates within the
subarachnoid space
How is the cerebrum divided?
4 lobes: frontal (motor), parietal (sensory), temporal (auditory), occipital (visual)
What does the frontal lobe do?
(primary motor cortex) is responsible for
voluntary complex motor activities, cognitive
functions (judgment, attention, awareness,
abstract thinking, mood, and aggression), and
speech
What does the parietal lobe do?
(primary sensory cortex) is responsible
for processing sensory information and applying
meaning to it, and short-term memory functions
What does the temporal lobe do?
(primary auditory cortex) is responsible
for hearing, comprehension of the spoken
language, visual perception, musical
discrimination, and long-term memory
What does the occipital lobe do?
(primary visual cortex) is responsible for
organization, integration, and interpretation of
visual information
What is the association cortex and what does it do?
– Areas in the parietal, temporal, and occipital lobes
that horizontally link different parts of the cortex
– Other functions include personality, memory,
intelligence, and emotions
Where are the motor areas located?
frontal lobe
What is the primary motor cortex?
responsible for contralateral
voluntary control of upper extremities and face
What is the premotor area?
controls muscles of trunk and
postural adjustments
What is the supplementary motor area?
controls initiation of
movement, orientation of the eyes and head, and
bilateral sequential movements
How is the cerebrum divided?
left and right hemispheres
Which hemisphere is responsible for language?
dominant hemisphere (95% left side)
What is the left hemisphere for?
verbal or analytic side
What is the right hemisphere for?
non-verbal and artistic side
Can the hemispheres do the same actions?
Even though the hemispheres have discrete
functional capabilities, they perform many of the
same actions
What is the corpus callosum?
connects right and left
hemispheres and allows constant communication
between the two
What is the internal capsule and what could a lesion here cause?
all descending fibers leaving the
motor area of the frontal lobe pass through here (a
lesion in this area can cause contralateral loss of
voluntary movement and conscious ability to
perceive tactile and proprioceptive input)
What is the diencephalon?
major sensory tracts, and visual and
auditory pathways synapse
What does the diencephalon include?
thalamus and hypothalamus
What is the thalamus?
receives all sensory impulses (except smell),
including pain and peripheral numbness, and receives
motor information from the basal ganglia and cerebellum
channeling this information to appropriate regions of the
cortex for interpretation
What is the hypothalamus?
regulates homeostasis, hunger, thirst,
digestion, body temperature, blood pressure, sexual
activity, sleep-wake cycles, and the pituitary gland and its
release of hormones (endocrine system and ANS)
What is the basal ganglia?
made up of the caudate, putamen,
globus pallidus, substantia nigra, and subthalamic
nuclei
What does the basal ganglia influence?
Influences motor planning, regulates posture, muscle tone,
controls volitional and automatic movements, and is
involved in cognitive functions
What does the limbic system do?
guides emotions that regulate
behavior, controls memory, pain, pleasure, rage,
affection, sexual interest, fear, and sorrow
What does the cerebellum control?
Controls balance and complex muscular movements
Where is the cerebellum located?
Located below occipital lobe/posterior to brain stem
How is the cerebellum divided?
two hemispheres
What is the cerebellum responsible for?
integration, coordination, and
execution of multi-joint movements
What does the cerebellum regulate?
initiation, timing, sequencing, and force
generation of muscle contractions
What does the brain stem control?
functions related to sensation, cranial
nerves, heart rate, and respiration
What is the brain stem divided into?
midbrain, pons, medulla
What is the midbrain?
connects diencephalon to the pons, is a relay
station for tracts between cerebrum and the spinal cord or
cerebellum, and houses reflex centers for visual, auditory
and tactile responses
What is the pons?
regulates breathing rate, contains reflex centers for
orientation of the head in response to visual and auditory
stimulation, and carry motor and sensory information to
and from the face (cranial nerves)
What is the medulla?
is extension of the spinal cord, contains fiber
tracts that run through the spinal cord, reflex centers for
the heart and respiratory rate, vomiting, sneezing, and
swallowing
What is the reticular formation?
maintains and adjusts level of
arousal including sleep-wake cycles, facilitates
voluntary and autonomic motor responses for selfregulation,
homeostatic functions and modulates
muscle tone throughout the body
What do brain cells depend on?
uninterrupted supply of blood
for glucose and oxygen
Where do all arteries rise from?
All arteries to the brain rise from the aortic arch
What are carotid arteries responsible for?
supplying the
bulk of the cerebrum circulation
What do middle and anterior cerebral arteries make up?
anterior circulation to the brain
What is the largest cerebral artery and most often occluded?
Middle cerebral artery
What is posterior circulation made up of?
two vertebral arteries
What do anterior and posterior communicating arteries do?
interconnect at the base of the brain (circle of Willis)
and provide a protective mechanism to the
structures of the brain
What happens when there isn’t adequate circulation?
death will occur within minutes and the cells
deprived of oxygen can not regenerate
When would changes to the neurons happen?
Changes in the neurons are not evident for 12-24
hours but at 24-36 hours the damaged area becomes
soft and edematous
Can damaged neurons recover?
The damaged neurons will not be replaced and the
original function of the area will be lost
What happens with nearby undamaged axons?
Nearby undamaged axons demonstrate collateral
sprouting in 4-5 days after injury increasing input to
other nearby neurons
What does the spinal cord do?
Coordinates sensory information, motor information
and movement patterns between the brain and
peripheral nerves
What is integrated in the spinal cord?
reflexes
How is the spinal cord connected to the brain stem?
Direct continuation of the brain stem
Where does the spinal cord end?
Direct continuation of the brain stem
What is the spinal cord composed of?
Ends around the first or second lumbar vertebra then
becomes the cauda equina
What are the dorsal and ventral horn responsible for?
• Upper portion (dorsal horn) is responsible for
transmitting sensory stimulus
• Lower portion (ventral horn) is responsible for
transmitting motor impulses
What is the lateral horn responsible for?
From T1-L2 (lateral horn) is responsible for
processing autonomic information
What does the periphery (white matter) do?
has fiber tracts that carry
sensory (ascending) and motor (descending)
impulses to various areas within the nervous system
What are dorsal columns?
carry information about proprioception,
vibration, two-point discrimination, and deep touch
What are ventral columns?
carry information about light touch and
pressure sensations
What is the Corticospinal tract?
primary motor pathway and
controls skilled movements of the extremities
What is Babinski sign?
An indicator of damage to the corticospinal tract is
a positive Babinski sign (great toe extends and
other toes splay)
What other descending tracts affect muscle tone?
rubrospinal, lat/med vestibulospinal, lat/med reticulospinal, tectospinal
What does the rubrospinal do?
facilitates flexor motor neurons and
inhibits extensor motor neurons (mainly proximal
upper extremity muscles) – assist in correction of
movement errors
What does the lateral vestibulospinal do?
assists in postural adjustments
through facilitation of proximal extensor muscles
What does the medial vestibulospinal do?
regulates muscle tone in the neck
and upper back
What does the lateral reticulospinal do?
facilitates flexors and inhibits
extensor muscle activity
What does the medial reticulospinal do?
facilitates extensors and inhibits
flexor muscle activity
What does the tectospinal do?
provides orientation of the head toward a
sound or moving object
What does the PNS consist of?
Consists of nerves leading to and from the CNS
(including the cranial nerves) connecting the CNS
with the rest of the body through sensory and motor
impulses
What do signs and symptoms of PNS involvement relate to?
relate to
motor and sensory systems as well as the ANS
What are primary functions of the cranial nerves?
eye
movements, smell, face and tongue sensation, and
innervations to the SCM and trapezius muscles
What are the spinal nerves?
8 cervical, 12 thoracic, 5
lumbar, 5 sacral and 1 coccygeal
Where do the spinal nerves exit?
C1 to C7 exit above the corresponding vertebrae (C8 above
T1) and from T1 on down exit below the corresponding
vertebrae
Are the spinal nerves sensory or motor?
they can be both
What is a dermatome?
region of skin innervated by a sensory
nerve from an individual spinal nerve
What is a myotome?
group of muscles innervated by an
individual spinal nerve
What is the cervical plexus?
spinal nerves C1-C4 and primarily
innervates the neck muscles
What is the brachial plexus?
spinal nerves C5-T1 and innervates
the majority of the upper extremities
What is the lumbar plexus?
spinal nerves L1-L4 and along with
the sacral plexus, innervates the lower extremities
What is the sacral plexus?
spinal nerves L4-S3 and innervates the
lower extremities
Are peripheral nerves motor or sensory?
they can be both
What does the ANS do?
Regulates circulation, respiration, digestion,
metabolism, secretion, body temperature, and
reproduction
What is the ANS controlled by?
hypothalamus and the brain stem
How is the ANS separated?
sympathetic and parasympathetic divisions
What does the sympathetic division do?
(“fight or flight”) - helps prepare to cope with
stimulus by maintaining optimal blood supply
What does the parasympathetic division do?
maintains vital bodily functions or
homeostasis
How is autoregulation achieved?
achieved by integrating information
from peripheral afferents with information from
receptors in the CNS
What are some causes of peripheral nerve injuries?
stretching, laceration, traction,
compression, disease, chemical toxicity, nutritional deficiency
What happens if the cell body is destroyed?
• If the cell body is destroyed: regeneration is not possible
• If damage is not too severe and only to the axon:
regeneration is possible
What happens to nonviable tissue?
it must be removed
What is the rate of axonal sprouting from the proximal end?
<10 mm per day depending on the size and location of the
nerve fiber
Does surgical repair of transected nerve endure full functional recovery?
Surgical repair of transected nerve does not ensure full
functional recovery
Why must the axon re-innervate the appropriate muscle?
Axon must re-innervate the appropriate muscle or axonal
sprouting will degenerate
What does the rate of recovery depend on?
Rate of recovery depends on patient age and the distance the
nerve needs to grow (1-12 weeks)
What are the changes that follow the severance of an axon?
1) The axon terminal degenerates to closest node of Ranvier 2) Myelin breaks down and forms debris 3) The cell body undergoes metabolic changes 4) Subsequently, presynaptic terminals retract from the dying cell body 5) Postsynaptic cells degenerate
What is an upper motor neuron lesion?
damage to the corticospinal
tract anywhere from the frontal lobe to the end in
the spinal cord
What are clinical signs of an upper motor neuron lesion?
spasticity, hyperreflexia, positive
Babinski sign, and possible clonus
What is a lower motor neuron lesion?
damage to the anterior horn
cell, motor nerve cells of brain stem, spinal root or
spinal nerve
What are clinical signs of a lower motor neuron lesion?
flaccidity, marked atrophy, muscle
fasciculation, and hyporeflexia
What is Charcot-Marie-Tooth disease?
Also known as hereditary motor & sensory neuropathy or peroneal muscular atrophy (1 in 2500 people)
How common is CTS?
Most common
entrapment
neuropathy in
the U.S. (3.5 in 1000)
What are neuromusculoskeletal causes of CTS?
– Amyloidosis – Anatomic sequelae of medical or surgical procedures – Basal joint (thumb) arthritis – Cervical disk lesions – Cervical spondylosis – Congenital anatomic differences – Cumulative trauma disorders – Peripheral neuropathy – Repetitive strain injury – Poor posture (may be associated with TOS) – Wrist trauma – Tendonitis – Trigger points – TOS
What are systemic causes of CTS?
‒ Alcohol ‒ Arthritis ‒ Leukemia ‒ Liver disease ‒ Medications ‒ Nonsteroidal ‒ Oral contraceptives ‒ Stains ‒ Alendronate ‒ Multiple myeloma ‒ Obesity
What are endocrine causes of CTS?
– Acromegaly – Diabetes mellitus – Hormonal imbalance – Hyperparathyroidism (Grave’s Disease) – Hypocalcemia – Hypothyroidism – Gout
What are infectious disease causes of CTS?
‒ Atypical mycobacterium ‒ Rubella ‒ Fungal infections • Histoplasmosis • Sporotrichosis
What is Bell’s palsy?
a common
condition in which the
facial nerve is unilaterally
affected (20 in 100000)
What is TOS?
TOS is an entrapment syndrome caused by pressure from structures in the thoracic outlet on fibers of the brachial plexus at some point between the interscalene triangle & the inferior border of the axilla
What is diabetic neuropathy?
– Typically occurs in distal, symmetrical patterns
– Classified as rapidly reversible, generalized symmetric
polyneuropathies, or focal neuropathies
What is alcoholic neuropathy caused by?
Due to total lifetime accumulation of ethanol
What does chronic renal failure cause?
– Lower extremities more commonly affected
– Cognitive decline
What does anemia cause?
– Difficulty with handwriting
– Loss of balance and proprioception
What are some infections/inflammations that affects the nervous system?
• Guillain-Barre Syndrome
• Post-polio syndrome/post-polio muscular atrophy
• Herpes zoster/post-herpetic neuralgia (shingles)
• Trigeminal neuralgia (5th cranial nerve)
• Human immunodeficiency virus advanced disease
(acquired immunodeficiency syndrome)
• Vasculitis
