Flashcards in Anatomy Deck (42):
What functions are found in each part of the brain?
-rostral: planning, problem solving, short term memory, controlling behavior
-Broca area: speech formation
-rostral the motor strip: skilled movement
-motor strip: voluntary
-rostral: sensory perception of self and world
-central: sensory data analyzed
-auditory data analyzed
*Wernicke area: language interpretation
-visual data interpreted
Limbic: contains the hippocampus and amygdala. Emotional processing and memory consolidation
What are the 12 cranial nerves and their functions?
1. Olfactory: smell
2. Optic: vision
3. Oculomotor - all eye muscles except superior oblique muscle and external rectus
4. Trochlear - superior oblique muscle
5. Trigeminal - sensory: face, sinuses, teeth
-motor: muscles of mastication
6. Abducens - external rectus
7. Facial - muscles of the face
8. Vestibulocochlear - sensory inner ear
9. Glossopharyngeal - pharyngeal musculature
Sensory: posterior part of tongue, pharynx and tonsils
10. Vagus - heart, lungs, bronchi, trachea, larynx, pharynx, GI tract, external ear
11. Accessory - sternocleidomastoid, trapezius
12. Hypoglossal - muscles of the tongue
What are the functions of astrocytes
1. Form glial membrane (external limiting membrane)
2. Component of blood-brain barrier
a. Control K+
b. Modulate vascular tone in the brain, controlling cerebral blood flow.
a. K+ from extracellular fluid at nodes of Ranvier during action potentials.
b. Neurotransmitters from synaptic clefts (Prevents glutamate excitotoxicity.)
4. Communicate through gliotransmitters (D-serine, glutamate, ATP) in response to adjacent synaptic activity.
5. Produce neurotrophic factors.
6. Produce scar tissue in response to CNS injury
What are satellite cells?
Satellite glial cells are the principal glial cells found in the peripheral nervous system, specifically in sensory, sympathetic, and parasympathetic ganglia. They compose the thin cellular sheaths that surround the individual neurons in these ganglia.
SGCs have been found to play a variety of roles, including control over the microenvironment of sympathetic ganglia. They are thought to have a similar role to astrocytes in the central nervous system (CNS). They supply nutrients to the surrounding neurons and also have some structural function. Satellite cells also act as protective, cushioning cells. Additionally, they express a variety of receptors that allow for a range of interactions with neuroactive chemicals.
What are the components of spinal nerves?
1. Motor efferents to muscle
2. Sensory afferents from skin, muscle, joints, visceral receptors.
3. Autonomic efferents to viscera*
-sympathetic in the thoracic and upper lumbar
-parasympathetic in the sacral
What are the vertebrae and nerves of the spinal cord?
Vertebrae - C1-C7 *
Nerves, C1-C7, C8*. So the spinal nerves exit in the intervertebral foramen above the vertebraes. So C8 vertebrae does not exist but the nerve does. All the other nerves exit in a foramen below so T1-T12, L1-L5, S1-S5
The conus medullaris is around L1
Describe the spinothalamic tract
A unipolar primary sensory neuron synapses with a secondary sensory neuron in the dorsal horn. The tract neuron crosses the midline (decussation) and travels up to the brain via the anterolateral pathway aka spinothalamic and synapses at the thalamus where an interneuron that takes the signal to the primary somatosensory cortex
A major sensory tract fro the spinal cord to the cortex, crosses in the spinal cord, so the representation is in the opposite brain.
Describe the stretch reflex circuit
A muscle sensory receptor detects stretch in the extensor muscle. Too much stretch and it travels up the afferent axon, synapses in the grey matter of the spinal cord, with help from interneurons, and then inhibit the extensor while stimulating the flexor using efferent axons.
Describe the features of the brain stem
The brain stem - features long pathways, and cranial nerves instead of spinal nerves.
They are important for functions the head can do like facial expression, ingestion, respiration
--keep in mind the flexure when taking locations---
from rostral to caudal - midbrain, pons, medulla oblongata
Midbrain: cerebral peduncle
*Cranial, only 3 and 4
-visual reflexes, visual motor control
-**has dopamine projections to corticol areas significant for movement and "reward"
Pons - balloon aka "big bridge to cerebellum"
Cranial nerves - 5,6,7,8
Function - balance, sound localization, eye movement coordination
Cranial nerves - 9,10,11,12
-regulation of body homeostasis/heart rate, respiration, vasomotor tone, gastric secretions
-vomiting, coughing, sneezing, swallowing, gagging
Damage to medulla is death
Describe the RAS-reticular activating system
Major component: reticular formation---
Nuclei and neuronal circuits
• Net-like appearance
• Through the core of the brainstem. • Include projections to the cortex or spinal cord.
RAS - beings in the reticular formation
Rostral projections from the pons and midbrain (pontomesencephalic)
• Projection controls attention, arousal, sleep and wakefulness.
• Includes several neurotransmitters systems
What is contained in the cross sections of these three
1. Cerebral peduncle (ventral)
2. Cerebral aqueduct
3. Colliculi (lil bumps dorsally)
1. large round base (ventral)
2. 4th ventricle
2. 4th ventricle
Describe the corticospinal tract:
Corticospinal tract: Major motor pathway from the cortex to the spinal cord. Upper motor neuron crosses in the medulla to control contralateral muscles.
Projects to the spinal cord from the primary motor cortex as all do,
-crosses at the medulla "pyramid decussation
-travels through the lateral corticospinal tract
-synapses in the anterior horn with the lower motor neuron which synapses on skeletal muscle
There are 6 layers of grey matter *cerebral cortex surrounding the white matter in the brain. What do each do?
Layers 2-3 contain neurons that project mainly to other areas of cortex
Layer 4 is sensory inputs from the thalamus (thalamocortical)
Layer 5 is motor output, projecting mostly to subcortial structures other than the thalamus such as brainstem, spinal cord and basal ganglia.
Association cortex: thick 2,3
Primary motor cortex: thick 5
Primary somatosensory cortex: thick 4
Electrical synapses - pros and where are they found?
They have faster, and more preserved event transfer between neurons.
direct physical connection allows flow of ions between cells
through gap junctions
• transmit depolarizing & hyperpolarizing currents
• gap junctions are composed of many individual channels
• each connexon is composed of a pair of hemi-channels (one
presynaptic, one post-synaptic)
low-resistance (high-conductance) pathway • near instantaneous (very short latency) transmission
*they do not regenerate their action potentials, the transmission diffuses all the way through
Coordinated connection of large groups of neurons
Found - retina, glial cells, astrocytes, enteric nervous system, cardiac
Describe and distinguish between the components of the blood-CSF and blood-brain
-choroid plexus which produces CSF and is found in all the major ventricles
-blood vessels entering the choroid plexus
1. Endothelial wall of the choroidal capillaries: No barrier-- are
2. Scattered pial cells.
3. Choroidal epithelial creates a blood-CSF barrier by tight junctions
– active transport, ion exchange mechanisms to determine
flow of molecules (e.g., Na+, K+, Cl-, Mg++, folates)
-blood vessels in subarachnoid space meeting brain tissue
-is formed by tight junctions between the brain capillary endothelial cell. Astrocyte foot processes surround the capillary but are not part of the barrier. They can control blood flow
Controls ionic environment--neurotransmission
Protects brain from toxins
Prevents drugs from entering brain Contains transporters for some critical molecules (glucose and proteins)
The blood-brain barrier may be disrupted by infections, tumors or trauma, causing
Describe the function of CSF
Is in the subarachnoid space around the brain and within the ventricles
*CSF provides bouyancy! and protects against sudden movements
-Maintains constant intracranial pressure
-Some antibacterial properties
-Controls the extracellular fluid of the brain
-Possible role in clearing metabolic wastes and toxins from interstitial space (especially during sleep)
Explain the flow of CSF beginning from the choroid plexus to the arachnoid villae.
1. Arterial blood crosses the choroid epithelium
2. Lateral ventricles >
3. Interventricular foramen of Monroe >
4. 3rd ventricles >
5. Cerebral Aqueduct >
6. 4th ventricle >
7. Foramen of Magendie (1 medial) and Luschka (2 lateral) >
8. Subarachnoid space around brain and spinal cord
9. Arachnoid granulations > venous sinuses END
Describe and give the clinical rationale for the lumbar puncture.
L3-L4 in adults
L4-L5 in children.
Contraindicated if there is HIGH Intracranial pressure: you could create a vacuum causing brain herniation
CSF pressure: normal is <20 cm H2O in lying position
1. Obtaining samples of CSF important for identifying:
-subarachnoid hemorrhage (detect blood)
-infections ex. meningitis
-Guillain Barre - an ascending weakness/paralysis commonly caused by GN Campylobacter Jejuni in which the body's immune system attacks part of the peripheral nervous system
2. Introduce drugs
Identify and the meningeal layers surrounding the spinal cord and brain.
Dura: 2 layers
-Arachnoid - many arachnoid trabeculae and cisterns
-1 layer of dura mater
-Arachnoid- fewer trabeculae and 1 cistern
-Pia - forms denticulate ligaments (secures to arachnoid), filum terminale internum attaches to arachnoid, externum attaches to coccyx.)
Identify the dural folds and describe, generally, the common areas of brain herniation.
Falx cerebri - in between
cerebral hemispheres (in longitudinal fissure).
Falx cerebelli - in between two
hemispheres of cerebellum.
Tentorium cerebelli - in
between the posterior
cerebral hemispheres and
the cerebellum. Wraps around the brain stem, forming a roof
Diaphragm sellae - circular
fold beneath the brain that
covers the sella turcica.
1- Temporal transtentorial herniation aka uncal
tentorial notch: the midbrain reticular formation goes right through the notch which is a tight space. If there is increased pressure in the supratentorial space, the brain can herniate right there, go into a coma because RAS is impinged. Tumor in temporal lobe can cause this.
2. Subfalcine aka Subdural- cingulate gyrus herniates below the falx cerebri - the most common form and does not necessarily mean severe symptoms, present as headache but can progress to contralateral leg weakness.
3. Central herniation or downward transtentorial: the diencephalon (thalamus and hypothalamus) and medial parts of both temporal lobes are forces through a notch in the tentorioum cerebelli.
4. Cerebellar tonsillar - is a type of cerebral herniation characterised by the inferior descent of the cerebellar tonsils below the foramen magnum. (seen in chiari I malformation
Describe the locations and causes of subdural, subarachnoid and epidural hematomas.
Epidural space: Potential space between the dura and the skull
*note in the spinal cord this is a real space filled with epidural fat.
-the middle meningeal artery lies on the dura mater so tearing can cause bleeding into the epidural space.
Subdural space: Potential space between the dura and arachnoid - subdural hematoma: usually venous blood (bridging veins)
Subarachnoid space: Real space where the major arteries of the veins are found
Identify the major vessels belonging to the anterior and posterior circulation.
Anterior: (internal carotid)
Posterior cerebral arteries
Superior cerebellar artery
Posterior inferior cerebellar
Anterior spinal artery
Describe the course of the ACA, MCA, and PCA.
PCA: goes mostly through the middle of the occipital
ACA - runs mostly in the midline, if you have a stroke in this artery, it will mostly effect legs - homunculus
MCA - Largest Cerebral artery Travels to the lateral cortex with several branches supplying subcortical regions
What are circumventricular organs?
Regions where the blood-brain barrier is interrupted. Enables brain to respond to changes in the blood chemistry (osmolarity for example)
Identify the location of lower motor neurons in the spinal cord.
Lower motor neurons
are located spinal cord ventral horn (lamina IX), or in brainstem motor nuclei.
Cell bodies serving more distal muscles are more lateral, proximal muscles are more medial. Flexors are dorsal, extensors are ventral.
ex. The ventral horns in the thoracic region don’t have any distal muscles to innervate, so ventral horn is thin.
*Upper motor neurons
Begin in cortex or brainstem and project in long-pathways to brainstem or spinal cord motor neurons - they project to lower motor neurons
List the cranial nerves that have lower motor neuron
Several cranial nerves (originating in the brainstem) have Lower motor neuron components
Called “bulbar” motor neurons
Cranial nerves: 3, 4, 6 - oculomotor, trochlear, abducens
Cranial nerve - 5 jaw opening
Cranial nerve 7 - face reactions
9,10,11 - Laryngeal and pharyngeal muscles (speaking, swallowing)
-Trapezius and sternocleidomastoid
12 - hypoglossal nerve - tongue sticking out
3,4,5,6,7 _ 9,10,11,12
so 1, olfactory, 2 - optic, 8 - vestibulocochlear -pure sensation
Distinguish between the 3 types of motor units.
1. ATPase strong reaction: FF (fast, fatiguable) - large motor neuron
2. ATPase mild reaction: Fast response (fast, fatigue resistant) - medium motor neuron
3. ATPase weak reaction: S (slow, fatigue resistant) - smaller motor neuron
Motor units: One motor neuron and all of the muscle fibers it innervates.
The number of muscle fibers innervated by a motor neuron varies (1:10 in extraocular muscles; 1:1,000 in leg muscles) - finer vs broad movements
*Motor neurons will determine muscle fiber types within the motor unit. All of the muscle fibers innervated by a motor neuron will be the same type.
Explain the mechanisms by which motor neurons increase the
force of muscle contractions (motor-unit recruitment).
To increase muscle force, motor units are recruited by size: small (S) > large (FF)
-after a motor unit is recruited, its firing rate increases
Define fibrillation and fasciculation and explain their clinical
Electromyographic changes: fibrillations, positive sharp waves, fasciculations. These are measures of denervation.
Electromyography is an investigatory tool to assess the source muscle weakness
1. Needle electrodes inserted into muscle
2. Study muscle at rest (normal: no activity)
3. During a contraction
Fibrillation: only detected with EMG. Short-duration, spontaneous biphasic or triphasic potentials produced by single muscle fibers. These are indicative of a denervated muscle.
These are thought to represent an unstable muscle fiber cell membrane. They both occur in peripheral nerve injuries, axonal neuropathies, motor neuron disorders and some myopathies.
Fasciculations: Larger potentials caused by spontaneous activity in a motor unit or several motor units. Caused by lower motor neuron lesions, particularly in anterior horn cell disease such as ALS. Large potentials are suggestive of denervation and reinnervation.
Describe and recognize the post-polio syndrome and its clinical
.The polio virus attacks ventral horn motor neurons, causing LMN syndrome
Recovery and stable period is due to sprouting by neighboring motor neurons
So patient has period of years during which she was neurologically stable. (usually ~ 15 years) followed by progressive weakness in the same muscles originally affected.
Post-polio period occurs years later because those new sprouts cannot be sustained.
Describe the lower motor neuron syndrome and explain the
physiological basis for each of the symptoms.
@the muscles that are innervated by motor neurons
1.Weakness or paralysis
-Muscle atrophy: Without motor neuron innervation, muscles cannot contract, so lose mass. They also lose trophic support from the motor neurons.
3.Hyporeflexia or areflexia
4.Decreased tone (resistance to passive movement) “flaccid paresis/paralysis”
5.Fibrillations, positive sharp waves or fasciculations, measured by EMG
Describe the common sites and causes of lower motor neuron
Cell bodies in CNS (Ventral horn or brainstem nuclei)
Axons in the PNS in ventral root, spinal nerve, peripheral nerve, or cranial nerve
1. Peripheral nerve, spinal nerve, or cranial nerve lesions
2. Cauda equina lesions
3. Strokes or tumors affecting alpha motor neurons in
ventral horn or brainstem
4. Polio (viral infection of α-motor neurons)
5. Amyotrophic lateral sclerosis ( “ALS” or “motor neuron
disease” that also affects upper motor neurons)
6. Guillain-Barré (demyelinating disease)
7. Werdnig-Hoffman disease (degeneration of anterior horn)
Describe the innervation of clinically important dermatomes.
C2-back of head
C5-shoulder, lateral arm
C6-digits 1-2, lateral forearm
T10-umbilicus (belly butten)
L4-knee, and medial lower leg
(down on ALL 4's)
L5-dorsal foot, big toe
S1-lateral foot, small toe, So1e
Explain the functions of grey matter areas of the spinal cord.
I-VI Dorsal Horn: sensory processing
VII Intermediate zone: sympathetic preganglionic neurons in intermediolateral cell
column (T1-L3), parasympathetic neurons in intermediomedial cell column (S2-S4).
VIII-IX: Ventral horn. Motor neurons and interneurons.
X: Gray matter surrounding the central canal.
Distinguish between levels of the spinal cord in cross sections.
From superior to inferior there is decreasing white matter.
Cervical - oval, largest dorsal and ventral horns - they innervate alot of movements - arms, limbs which include sensory input then
Lumbar - Larger dorsal and ventral horns (round shaped)
Thoracic is particular in that it has a very small ventral and dorsal horn because it really doesn't innervate all that much.
Generally describe the anatomy of the SNS
They arise in levels T1-L3. Lateral horns (intermediolateral nuclei) contain the preganglionics. Then they synapse in sympathetic ganglia - prevertebral, paravertebral, adrenal. Lastly synapsing on End organs.
Preganglionics use NT - acetylcholine
Postganglionics use NT- norepinephrine.
Generally describe arrangement of PNS
-are synapse on parasympathetic ganglia in or near end organ
Octopus feels good vaginally
Preganglionics arise from S2-S4 intermediate zone
*all of these feature parasympathetic ganglia in or near end organs .
Describe the blood supply to the spinal cord
Anterior spinal artery
(1) located in the ventral median fissure
-Supplies anterior 2/3 of spinal cord
Posterior spinal artery
(2) located in the posterolateral sulci Supplies posterior 1/3 of spinal cord
Vasocorona: a series of branches from the anterior and posterior spinal arteries that form a crown (“corona”) around the cord.
Anterior and posterior radicular arteries arise from segmental arteries at each spinal
level to serve their respective roots and ganglia.
• The anterior and posterior spinal medullary arteries arise at intermittent levels to
augment the blood supply.
• The great Artery of Adamkiewicz is unusually large anterior radicular artery arising on
the left from T9-L1. It supplies the majority of the lumbar and sacral SC.
Great radicular artery of adamkiewicz is so important that it is thought to supply the whole bottom of the spinal cord and blockage presents as a lower spinal cord injury
What is the watershed area?
T4-T9 watershed area
• Fracture dislocations of
vertebra can interfere
with blood supply.
• Arterial disease can
obstruct great radicular
• Occlusion of aorta
during surgery can
damage to blood supply.
Its a region between the endpoints of the thoracic radicular artery
& great radicular artery of adamkiewicz
Drop in blood pressure, can lead to this watershed region being necrotic.
Describe spinal cord Lower motor neurons with important functions
C3-C5 Motor neurons to the Phrenic nerve controlling diaphragm.
S3-S4 Onuf’s nucleus: Motor neurons innervating urethral and external anal sphincter which enable voluntary control of urination and defecation.
S2-S4 Motor neurons to pelvic floor muscles.
*very low spinal cord lesions (cauda equina) can produce bowel and bladder incontinence
Describe a motor nerve conduction test
Surface electrodes stimulate skin over the nerve, to excite the nerve.
Recording electrodes record the Compound Action Potential.
Measure the size of the muscle response (CMAP)
=decreased in problems
with muscle, motor
neuron or neuromuscular
Measure conduction velocity Measure the time to the CMAP/distance btw. electrodes
• Normal values are published
• Only measures fastest fibers
• Decreased with demyelinating