Neuroanatomy Backup 4/7/13

Front 1

Posterior column-medial lemniscal pathway

Back 1

Carries info about proprioception, vibration sense, and fine touch. Primary sensory neuron (dorsal root) --> ascends via ipsilateral white matter dorsal column --> synapse w/ dorsal column nuclei medulla --> secondary sensory neuron decussates --> synapse in the thalamus --> project to the primary somatosensory cortex in the postcentral gyrus

Front 2

Anterolateral pathway

Back 2

Carries info about pain, temperature sense, and crude touch. Primary sensory neuron (dorsal roots) --> synapse in gray matter of the spinal cord --> secondary sensory neuron decussates and ascends in anterolateral white matter (spinothalamic tract) --> synapse in thalamus --> project to the primary somatosensory cortex in the postcentral gyrus

Front 3

Which sensory input does not pass through the thalamus?

Back 3

Olfactory

Front 4

Components of the diencephalon

Back 4

Thalamus, hypothalamus, epithalamus

Front 5

Monosynaptic stretch reflex

Back 5

Reflex arc that begins with muscle spindles (sense stretch) --> transmission to sensory neurons --> dorsal root --> synapse in spinal gray matter with lower motor neurons (LMN's), causing contraction.

Front 6

Deep tendon reflex

Back 6

Muscle stretch reflex arc that begins with muscle spindles sensing stretch. Response can be routed via a monosynaptic stretch reflex (direct to LMN) and via interneurons (inhibitory). Tested clinically by tapping tendon with reflex hammer.

Front 7

CN I

Back 7

Olfactory nerve. Olfaction.

Front 8

CN II

Back 8

Optic nerve. Vision.

Front 9

CN III

Back 9

Oculomotor nerve. Extraocular muscles, except those innervated by CN IV and VI; parasympathetics to pupil constrictor and to ciliary muscles of lens for near vision

Front 10

CN IV

Back 10

Trochlear nerve. Superior oblique muscle; causes the eye to move downward and to rotate inward (depression and intorsion)

Front 11

CN V

Back 11

Trigeminal nerve. Sensations of touch, pain, temperature, vibration, and joint position for the face, mouth, nasal sinuses, and meninges; muscles of mastication; tensor tympani muscle.

Front 12

CN VI

Back 12

Abducens nerve. Lateral rectus muscle; causes abduction (outward movement) of the eye

Front 13

CN VII

Back 13

Facial nerve. Muscles of facial expression; also stapedius muscle and part of digastric; taste from anterior 2/3 of tongue; sensation from a region near the ear; parasympathetics causing lacrimation and supplying the submandibular and sublingual salivary glands

Front 14

CN VIII

Back 14

Vestibulocochlear nerve. Hearing; vestibular sensation.

Front 15

CN XI

Back 15

Glossopharyngeal nerve. Stylopharyngeus muscle; taste from posterior 1/3 of tongue; sensation from posterior pharynx, and from a region near the ear; chemo- and baroreceptors of the carotid body; parasympathetics to the parotid gland

Front 16

CN X

Back 16

Vagus nerve. Pharyngeal muscles (swallowing); laryngeal muscles (voicebox); parasympathetics to the heart, lungs, and digestive tract up to the splenic flexure; taste from epiglottis and pharynx; sensation from the pharynx, posterior meninges, and a region near the ear; aortic arch chemo- and baroreceptors

Front 17

CN XI

Back 17

Spinal Accessory nerve. Sternomastoid muscle; upper part of the trapezius muscle.

Front 18

CN XII

Back 18

Hypoglossal nerve. Intrinsic muscles of the tongue.

Front 19

From what does the CNS form?

Back 19

Wall of the neural tube

Front 20

Where does the ventricular system of the brain originate?

Back 20

The lumen of the embryonic neural tube

Front 21

Dorsal/ventral roots vs dorsal/ventral rami

Back 21

Roots are unimodal (they only carry information in one direction). Rami carry both afferent and efferent information.

Hint 21

Front 22

Describe a neuron nucleus

Back 22

Large nucleus and large nucleolus

Front 23

Major types of neuron interconnections

Back 23

Axoaxonic, axosomatic, axodendritic

Front 24

Embryologic origins of afferent cells, efferent cells, and association cells

Back 24

Afferent cells (bipolar and pseudounipolar) derive from neural crest cells. Efferent cells (multipolar) come from basal lamina. Association cells come from alar lamina.

Front 25

White matter

Back 25

Essentially tons of myelinated axons without cell bodies. Myelin lipids gives rise to white color.

Front 26

Gray matter

Back 26

Mainly cell bodies (nuclei) and dendrites without myelinated axons

Front 27

What kind of image is this?

Back 27

Myelin stained cross section.

Front 28

Describe the 3 primary brain vesicles and the 5 secondary brain vesicles.

Back 28

Front 29

Oligodendrocytes

Back 29

Glial cells that provide myelination to neurons in the CNS

Front 30

Nissl body

Back 30

Granules of RER with ribosomes attached that are located in neurons

Front 31

What kinds of things move by orthograde transport?

Back 31

Neurotransmitters, AA's, and membrane proteins. They travel via kinesin motor proteins.

Front 32

What kinds of things move by retrograde transport?

Back 32

Trophic factors/growth factors, viruses

Front 33

Axon hillock

Back 33

Junction between the cell body and the axon. Typically not covered by myelin or oligodendrocytes. More susceptible to changes in local ion concentrations. Site of departure of an action potential.

Front 34

How do you name the arms of pseudounipolar and bipolar neurons?

Back 34

Peripheral and central processes.

Hint 34

Front 35

Myelinated vs unmyelinated (structurally)?

Back 35

B. Unmyelinated axons are just "invaginations" into the Schwann cells (note they are not within the cytoplasm). i.e Remak Bundles

Front 36

Astrocyte functions

Back 36

Circumscribe the CNS (glia-pia membrane), induce blood brain barrier, buffer K+, regulated glutamate and glycogen in the brain, guide neurons during development, react to injury

Front 37

How do astrocytes buffer potassium?

Back 37

Astrocytes have many K+ channels and pick up the K+ ions that neurons release. There is also intra-astrocytic movement of K+ down its concentration gradient.

Hint 37

Bonus: when glial cells get sick and die, neurons can't survive.

Front 38

How do astrocytes regulate glutamate?

Back 38

Glutamatergic neurons release glutamate into the synaptic space. The glutamate is picked up by astrocytes, converted to glutamine, and given back to the presynaptic bouton.

Front 39

Excitotoxicity

Back 39

Path. by which neurons are damaged by excessive stimulation by NT's, e.g. glutamate.

Front 40

How do astrocytes regulate glucose?

Back 40

Most transfer of glucose from blood to CNS happens through astrocytes (they virtually envelop all of endothelial cells).

Front 41

Two types of astrocytes

Back 41

Protoplasmic astrocytes --> grey matter, more numerous.

Fibrous astrocytes --> white matter.

Front 42

Two types of oligodendrocytes

Back 42

Fascicular --> white matter

Perineuronal --> grey matter

Front 43

Internodal segment

Back 43

A segment of myelinated axon between 2 nodes of Ranvier

Front 44

How do oligodendrocytes and Schwann cells differ in the number of internodal segments they can make?

Back 44

ODC's can make an internodal segment on many different axons in the CNS, but SC's can only wrap one axon (1 internodal segment) in the PNS

Front 45

What is the dark purple material?

Back 45

Lipofuscin granules are lipid-filled waste products that can collect around neurons (as well as other cell types).

Front 46

What is this?

Back 46

Longitudinal view of nerve, with two internodal segments shown with a node of Ranvier between them.

Front 47

From which pharyngeal arches does the viscerocranium develop?

Back 47

1st and 2nd

Front 48

What are the nerve supplies to the pharyngeal arches?

Back 48

1st = trigeminal (V), 2nd = facial (VII), 3rd = glossopharyngeal (IX), 4-6th = vagus (X).

Hint 48

Mnemonic: when you eat something bad, you 1) chew 2) make a face 3) swallow

Front 49

What are the 5 prominences that come together to form the nose?

Back 49

Frontonasal prominence, lateral nasal prominence, medial nasal prominence, maxillary prominence, mandibular prominence

Front 50

What are the skeletal derivatives of pharyngeal arch 1?

Back 50

Meckel's cartilage, malleus, incus

Front 51

What are the skeletal derivatives of pharyngeal arch 2?

Back 51

Lesser horn of hyoid bone, styloid process, stapes

Front 52

At what level in the brain does the directional naming convention change?

Back 52

Between the diencephalon and the midbrain.

Front 53

The lumen of the primitive mesencephalon becomes what adult structure?

Back 53

Cerebral aqueduct

Front 54

Where does the cervical flexure occur in the primitive brain?

Back 54

Between the caudal end of the myelencephalon and the rostral end of the spinal cord

Front 55

Name the layers of tissue that one would have to pass through to reach the arachnoid mater superiorly.

Back 55

SCALP + calvarium + dura mater

Front 56

Where does the middle meningeal artery enter the skull? Where does it travel? What does it supply?

Back 56

Enters through the foramen spinosum; runs in the epidural space; supplies the dura mater.

Front 57

Which arteries make up the circle of Willis?

Back 57

Anterior cerebral aa, anterior communicating, internal jugular aa, posterior communicating aa, posterior cerebral aa

Front 58

The dura mater is "glued" to the skull by what?

Back 58

Sharpey's fibers

Front 59

What is the most vulnerable part of the calvarium to fracture?

Back 59

Pterion - very thin, and also at risk for damaging the meningeal artery

Front 60

What part of the dura dissects due to injection of fluid or subdural hematoma?

Back 60

The deep layer of the meningeal dura because it has fibroblasts but not collagen. The more superficial layers of the dura have collagen and are very difficult to dissect.

Front 61

What is the tentorial notch?

Back 61

Also called the tentorial incisura, it is the opening between the right and left leaves of the tentorium cerebelli. The hindbrain passes through it. With increased ICP, structures may herniate through it, e.g. uncal herniation.

Front 62

Where are cerebral veins located?

Back 62

Subarachnoid space

Front 63

What cell-cell contact is made between the menginges and brain parenchyma?

Back 63

Pia mater - to - glial cell contacts. Pia mater does not contact neurons.

Front 64

What are the two layers of the pia mater?

Back 64

Epipia layer - collagen and fibroblasts.

Intima pia layer - reticular and elastic, in contact with glia

Front 65

Meningiomas are tumors of what layers of the meninges?

Back 65

Leptomeninges

Front 66

What is a dermatome?

Back 66

A peripheral region innervated by sensory nerve fibers from a single nerve root.

Front 67

Which of the two systems of ascending tracts is more primitive and of lower velocity?

Back 67

The anterolateral system, which transmits pain, temperature, and crude touch.

Front 68

GSE

Back 68

General somatic efferent. Cells that give rise to axons that innervate striated muscles.

Front 69

GVE

Back 69

General visceral efferent. Autonomic neurons that synapse with a postganglionic cell which eventually innervate smooth muscle and glands.

Front 70

SVE

Back 70

Special visceral efferent. Cells that give rises to axons that innervate structures of the branchial arches, e.g. facial muscles, mastication, pharyngeal muscle. These cells are only found in the brainstem.

Front 71

What are the two types of cells located in the dorsal root?

Back 71

Somatic afferents (from ectoderm and somatic mesoderm derived cells) and visceral afferents (from endoderm and splanchnic mesoderm derived cells).

Front 72

What is shown here (conceptually)?

Back 72

These are the columns of cells in the CNS that are derived from neural crest, alar lamina, and basal lamina. The basal lamina has 3 sub groups: GSE, GVE, and SVE. The alar lamina has 4 sub groups: general/visceral, somatic/special afferent association cells. Not all cell columns are present at each level of the spinal cord/brain stem.

Front 73

Dendritic spread

Back 73

The area where one nerve can communicate/synapse with another nerve is not just localized to the soma (axosomatic). It can be anywhere throughout the postsynaptic nerve's dendritic spread which may branch extensively throughout gray matter and even some white matter.

Front 74

Divergence

Back 74

The functional idea that a neuronal axon can branch and synapse with multiple cells.

Front 75

Convergence

Back 75

The functional idea that one neuron can receive synapses from multiple difference neuronal axons.

Front 76

Name the CT coverings of a nerve fiber and brief function.

Back 76

Endoneurium gives substance to surrounding nerve axons and capillaries. Perineurium sequesters groups of axons, is water tight, and forms the "blood-nerve barrier". Epineurium acts a protective layer around the nerve.

Front 77

What is the conduction speed of alpha motor neuron?

Back 77

70-120 m/s

Front 78

Shoulder abduction

Back 78

*C5, C6 via the axillary neve

Front 79

Elbow flexion

Back 79

C5, *C6 via the musculocutaneous nerve

Front 80

Elbow extension

Back 80

C6, *C7 via the radial nerve

Front 81

Wrist extension

Back 81

*C6, C7 via the radial nerve

Front 82

Wrist flexion

Back 82

*C7, C8 via the median nerve

Front 83

Finger extension

Back 83

*C7, C8 via the radial nerve

Front 84

Finger flexion

Back 84

C8, T1 via the median/ulnar nerves

Front 85

Finger abduction

Back 85

*T1 via the ulnar nerve

Front 86

What are the two fiber bundles of the posterior columns, and from which regions of body do the nerves inside them come?

Back 86

Gracile fasciculus - sacral to T6.
Cuneate fasciculus - T6 up and cervical.

The lower extremity is represented medially (gracile) and the upper extremity is represented laterally (cuneate) within the posterior columns.

Front 87

Monoamines

Back 87

E.g. dopamine, NE, serotonin. NT's with an amino group and aromatic group--derived from aromatic amino acids.

Front 88

MAO

Back 88

Monoamine oxidase enzyme degrades monoamine NT's (DA, NE, S).

Front 89

COMT

Back 89

Catechol-O-methyl transferase enzymes degrades catecholamine NT's (NE, DA).

Front 90

AChE

Back 90

Acetylcholinesterase enzyme degrades acetylcholine.

Front 91

Benzodiazepines

Back 91

Sedative-hypnotic drug that binds to BZ receptor (part of GABA-A receptor). MOA: Increases GABA affinity and freq. of GABA-stimulated chloride channel opening. Leads to hyperpolarization. Rx orally for anxiety (short-term) and traditionally sleep disorders. Also, Rx for seizures, withdrawal states. Incr. lipid solublity, more rapid onset. Cleared by hepatic metab. SE: daytime drowsiness, sedation, ataxia, depressed respiration, *enhance CNS depression in combo with EtOH

Front 92

Diazepam

Back 92

Valium®. Benzodiazepine tranquilizer. Rx for anxiety, preanesthetic, seizures, withdrawal states, muscle relaxation. Long lasting, t1/2 > 24 hr.

Front 93

Alprazolam

Back 93

Xanax®. Benzodiazepine tranquilizer. Rx for anxiety, antidepression.

Front 94

Temazepam

Back 94

Restoril®. Benzodiazepine tranquilizer. Rx for insomnia.

Front 95

Phenobarbital

Back 95

Barbiturate, CNS depressant. Rx for anticonvulsant, sedative/hypnotic. MOA: acts allosterically on GABA-A receptors to potentiate and prolong effect of GABA. No real margin of safety. Very long acting (t1/2 ~ 2-7 days).

Front 96

Valproate semisodium

Back 96

Depakote®, divalproex sodium. Rx for manic episodes bipolar, epilepsy. MOA: possible GABA agonist. SE: teratogenic, liver disease.

Front 97

Zolpidem

Back 97

Ambien®. Nonbenzodiazepine sedative-hypnotic that acts on BZ receptor, potentiating GABA-A receptor. Rx for insomnia. In the class of "Z drugs" for insomnia.

Front 98

Eszopiclone

Back 98

Lunestra®. Nonbenzodiazepine hypnotic. Rx for insomnia. In the class of "Z drugs" for insomnia.

Front 99

Flumazenil

Back 99

Benzodiazepine antidote. Rx for BZ overdose.

Front 100

Inhibitory NT's bind to what kind of receptors to produce IPSP's?

Back 100

Ligand-gated K+ or Cl- channels. Both types push the local potential towards hyperpolarization, making it more difficult to achieve threshold.

Front 101

Nociception

Back 101

Experience of stimuli that damage tissue

Front 102

What's the function of the anterolateral pathway?

Back 102

To initiate the cells needed for protection and repair due to the stimulus of tissue damaging events. One thing is to make you aware, but the system actually developed to protect you from harm first.

Front 103

4 component operations of the ascending (sensory) system

Back 103

1. Transduction
2. Transmission
3. Perception/Localization
4. Interpretation

Front 104

Lissauer's tract

Back 104

Posterolateral tract. Contains Adelta and C fibers from dorsal rootlets entering spinal cord. Through this tract, these afferent fibers can ascend or descend 3 segments before entering gray matter.

Front 105

By the time afferent fibers from Adelta and C cross the midline, where in the spinal cord are they located relative to the segment it entered?

Back 105

They are about 2 segments upward when they have crossed the midline and entered the anterolateral column.

Front 106

How does encapsulation affect a sensory nerve ending?

Back 106

It lowers the threshold potential and allows for more sensitive nerve endings.

Front 107

What enters Lissauer's tract?

Back 107

A-delta and C fibers. NOT A-beta or Ia or Ib or II (muscle spindles)

Front 108

1) The central processes of afferent A-delta and C fibers synapse in which Rexed laminae?

2) And the cell bodies that provide the synapses (2nd order) are located in which laminae?

Back 108

1) I, II, V (A delta) and I, II (C fibers)

2) all but II and IX

Front 109

What is the somatotopic organization of the anterolateral column?

Back 109

Sacral is dorsolateral and cervical is ventromedial.
As the fibers enter the anterolateral column they enter laterally first.

Front 110

The medial part of VPL receives synaptic input from which dorsal fasciculus?

Back 110

Fasciculus cuneatus

Front 111

Stereognosis

Back 111

The faculty of perceiving and understanding the form and nature of objects by the sense of touch--via the lemniscal system. The absence of this ability is astereognosis or tactile object agnosia.

Front 112

Why is the tuning fork placed on bone?

Back 112

To entrap the Pacinian corpuscle against a hard surface so that the cutaneous tissue above it doesn't absorb all the vibration.

Front 113

What segment is this? Why?

Back 113

~ S1. The ventral horn is large (limb enlargement) and the dorsal columns are relatively small (not much of the lemniscal column has been added).

Front 114

What segment is this? Why?

Back 114

~T2 to T6 probably. The ventral horn is relatively small (so we are not looking at a limb region). The dorsal columns and anterolateral columns are relatively large so we are higher up the spinal cord. Also, we see a lateral horn (IML) which is sympathetic preganglionic cell bodies that are ONLY located between T1 and L2

Front 115

What region is this? Why?

Back 115

Pyramidal decussation is present, therefore we are in the caudal part of the caudal medulla. Also present are the nucleus gracilis and nucleus cuneatus.

Front 116

What region of is this? Why?

Back 116

Inferior olivary nucleus is present therefore we are at lower border of rostral medulla.

Front 117

Where is the distribution of the C5 dermatome?

Back 117

Lateral aspect of arm (e.g. superior aspect of abducted arm).

Front 118

Where is the distribution of the C6 dermatome?

Back 118

Lateral forearm and thumb

Front 119

Where is the distribution of the C7 dermatome?

Back 119

Middle and ring fingers (or middle three fingers) and the center of the posterior and anterior forearm.

Front 120

Where is the distribution of the C8 dermatome?

Back 120

Little finger, medial side of hand and forearm

Front 121

Where is the distribution of the T1 dermatome?

Back 121

Medial aspect of the forearm and inferior arm

Front 122

Where is the distribution of the L1 dermatome?

Back 122

Inguinal/suprapubic region

Front 123

Which spinal nerve innervates the lateral calf region

Back 123

L5

Front 124

Which spinal nerve innervates the lateral foot region?

Back 124

S1

Front 125

What are the nerve roots for the lateral cutaneous nerve of the thigh?

Back 125

L2-L3

Front 126

What are the 3 trunks of the brachial plexus and which nerves give rise to them?

Back 126

Superior is from C5, C6 ventral rami. Middle is from C7. Inferior is from C8, T1.

Front 127

What are the 3 cords of the brachial plexus and which nerve structures give rise to them?

Back 127

Lateral cord comes from 1 branch off the superior trunk and 1 branch off the middle trunk. Posterior cord comes from 1 branch off the superior, middle, and inferior trunks. Medial cord comes from the continuation of the anterior division of inferior trunk.

Front 128

Where is the lower body located in the motor homunculus?

Back 128

Medial to the arms, near the sagittal fissure.

Front 129

Describe the layout of the internal capsule and its bordering structures.

Back 129

V-shaped, "pointing medially". Anterior limb is bordered by globus pallidus and putamen laterally and the caudate nucleus medially. The genu is the knee or bend. The posterior limb is bordered by the globus and put laterally and the diencephalon medially.

Front 130

Describe the spatial relationships of the posterior columns fibers as they cross the midline in the medulla.

Back 130

In the posterior column, FGr is medial and FCu is lateral. After synapsing with their respective nuclei, Gr moves ventrally and Cu moves dorsally via the interarcuate fibers.

Front 131

Renshaw cells

Back 131

Inhibitory interneurons in the spinal cord that receive their afferent input from collateral branches of nearby efferent cells. These cells are "unique" because they are interneurons that are activated by efferent cells rather than afferent or descending neurons.

Front 132

Where are LMN cell bodies that innervate trunk flexors and extensors located?

Back 132

Medially inside the ventral horn

Front 133

All LMN's are located in which Rexed lamina? Where is it located?

Back 133

Lamina IX are "islands" within the ventral horn. There is somatotopic organization within the lamina IX islands in which axial innervation is medial and limb innervation is lateral.

Front 134

Which muscle fiber type (white/red) are more sensitive to disuse atrophy?

Back 134

Red fiber type

Front 135

Compare/contrast motor unit size

Back 135

Front 136

What type of nerve fiber innervates the periequatorial region of a muscle spindle?

Back 136

Type II fiber -- afferent fiber from secondary nerve endings (predominantly nuclear chain fibers) of the muscle spindle

Front 137

What does the "total convergence/total divergence" idea mean for Ia fibers?

Back 137

The Ia fibers from muscles spindles in a given muscle diverge and converge to monosynaptically "communicate" with all LMN's of that muscle.

Front 138

Which spinal nerves does the knee-jerk reflex test?

Back 138

L2 - L4

Front 139

Why is normal muscle tone maintained when passive muscle lengthening occurs?

Back 139

The alpha motor neuron activity stimulated by Ia afferents is counterbalanced by alpha motor inhibition from GTO's.

Front 140

Define muscle tone

Back 140

The level of activity (contraction) seen in resting skeletal muscle. "Resting" means some motor units are activity but not sufficient to produce movement. I.e. a muscle's resistance to passive stretch during a resting state

Front 141

UMN lesions are characterized by:

Back 141

Weakness, spasticity (clasped-knife phenomenon), hyperreflexia, primitive reflexes and the Babinski sign. Primitive reflexes include the grasp, suck and snout reflexes.

Front 142

LMN lesions are characterized by:

Back 142

Weakness, hypotonia, hyporeflexia, atrophy and fasciculations.

Front 143

Fasciculations

Back 143

Fine movements of the muscle under the skin; indicative of lower motor neuron disease. They are caused by denervation of whole motor units leading to ACh hypersensitivity at the denervated muscle. Atrophy of the affected muscle is usually concurrent with fasciculations.

Front 144

Eccentric contraction

Back 144

Sarcomeres get longer as you contract because the opposing force is greater than what the muscle is generating.

Front 145

Concentric contraction

Back 145

Sarcomeres get shorter as you contract because the force of muscle contraction is greater than the opposing load.

Front 146

Which type of afferent nerve fiber supplies secondary endings in the muscle spindle?

Back 146

Type II afferent

Front 147

If gamma neuron firing goes down, spindle sensitivity goes...?

Back 147

Down. By decreasing gamma motor neuron activity, the spindle is allowed to relax and become "less sensitive to stretch".

Front 148

What's the goal of alpha/gamma coactivation in maintaining muscle tone?

Back 148

To maintain a constant afferent Ia pulse in order to keep the same number of motor units active throughout a full range of passive motion.

Front 149

Why are the lower limb reflexes more brisk than upper limb reflexes?

Back 149

Lower limb reflexes (especially the extensors) are modified to be brisk, automatic reflexes because they are working on anti-gravity muscles.

Front 150

What are some characteristics of automatic behaviors (responses/reflexes)?

Back 150

relatively simple;
relatively predictable response to a specific stimulus;
relatively independent of "higher centers";
not typically or greatly affected by alterations in consciousness

Front 151

Pronator drift

Back 151

When holding arms outwards and supinated, the arm (contralateral to the lesion in the brain due to stroke) drifts to a mid-pronated position. This is due to spasticity in the pronator muscle.

Front 152

Spasticity

Back 152

A motor disorder involving UMN's characterized by a velocity-dependent increase in tonic stretch reflexes (muscle tone) and exaggerated phasic muscle stretch reflexes.

Front 153

Muscle reflex latency

Back 153

How long after the stimulus does the reflex response occur? Not observable clinically, but can see it with nerve conduction studies. Demyelinating diseases can manifest this way.

Front 154

Muscle reflex amplitude

Back 154

How great is the response with a standardized stimulus? Compare bilaterally.

Front 155

Muscle reflex spread

Back 155

Does the stimulus cause alpha motor neuron activity in other muscles besides the one being tested? E.g. crossed-adductor reflex. By tapping the patellar tendon, the other leg adducts.

Front 156

Muscle reflex duration

Back 156

How long does the elicited reflex (contraction) occur? E.g. hanging reflexes.

Front 157

Plantar reflex

Back 157

Stroking of the lateral foot and across the plantar base of the toes. Normally, the toes should flex and curl inward. Abnormally, the Babinski sign is the extension and fanning of the toes in response to the plantar stimulus. This is due to a UMN lesion is adults, and can be normal in infants < 1 y/o.

Front 158

Which afferent fibers mediate the second, burning pain, warm, dull pain, itching, and sensual touch?

Back 158

C fibers

Front 159

Which afferent fibers mediate the first/fast pain, sharp pain, cold and pressure sensation?

Back 159

A delta fibers

Front 160

What is the midbrain tectum?

Back 160

Literally, the "roof" of the midbrain. Located in the dorsal mesencephalon (midbrain)-- it consists of superior and inferior colliculi (i.e. or the nuclei residing within these "bumps").

Front 161

Who talks to the magnocellular cells of the red nucleus?

Back 161

Cortex, globus pallidus, cerebellum.

Front 162

What's the general role of the cerebellum in communicating with motor neuron pathways?

Back 162

The cerebellum determines the sequences of events (EPSP's and IPSP's) in time to achieve a specific motor task.

Front 163

What's the general role of the basal ganglia in communicating with motor neuron pathways?

Back 163

The basal ganglia determine which LMN's you need to sends EPSP's and IPSP's to in order to achieve a specific motor task.

Front 164

Describe the pathway of the rubrospinal tract.

Back 164

The tract begins in the red nucleus (midbrain), crosses midline at ventral tegmental decussation, and descends contralaterally in the lateral funiculus (along with the lateral corticospinal tract). Note, some collateral branches terminate early in the pons and medulla.

Front 165

What is the major target of rubrospinal innervation?

Back 165

Upper limb proximal flexor muscles. Although it does go to flexors in the lower limb.

Front 166

Where do tectospinal fibers decussate?

Back 166

Dorsal tegmental decussation

Front 167

What's the boundary between the medulla and the spinal cord, and where is it located?

Back 167

Cervicomedullary junction, located at the foramen magnum

Front 168

Where do fibers in the anterior corticospinal fibers cross the midline?

Back 168

Mostly at the segmental level via interneurons rather than crossing at the pyramidal decussation.

Front 169

What are the 3 regions that UMN's can be found in the frontal cortex?

Back 169

Precentral gyrus, premotor cortex, supplementary cortex.

Front 170

For corticospinal UMN's, the most rostral decussating fibers come from where in the cortex?

Back 170

Upper limb (lateral cortex). The upper limb ends up medial in the lateral tract and the lower limb is lateral.

Front 171

Betz cells

Back 171

Very large neurons in the primary motor cortex, but only make up 4% of corticospinal cells. These tend to go to the distal musculature of the limb and synapse with alpha motors without interneurons.

Front 172

What is this diagram showing?

Back 172

Not everyone has a "textbook" pattern of pyramidal decussation. Most normal is 85% decuss/15% ipsilateral. However, 3% of people don't decussate at all, and 13% of people decussate completely (leaving no anterior pathway).

Front 173

Corticospinal UMN's are influenced by:

Back 173

1) cortical-cortical connections (e.g. frontal lobe, what's the goal?, write a program)
2) cortico-ponto, ponto-cerebellar, cerebellar-thalamic, thalamic-cortical (control WHEN in time that EPSP's and IPSP's need to fire to achieve a particular muscle movement)
3) cortico-strio, strio-pallido, pallido-thalamic, thalamocortico (WHICH muscles need to contract/relax)

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Corticospinal fibers passing through the cerebral peduncle (midbrain)

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Genu of the internal capsule.

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VPL nuclei

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Cerebral peduncles

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Red nucleus

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Where are the corticospinal fibers located? What proportion of corticospinals make up this region?

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1 million out of 4 million in that "fifth" of the peduncle. In total, the peduncle has ~20 million axons.

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Ventral tegmental decussation

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MLF (medial longitudinal fasciculus). Interconnects the occulomotor, trochlear, and abducens nuclei so that we get conjugate eye movements.

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Longitudinal pontine bundles. These are formed by axons of the tightly compacted cerebral peduncles being separated by the pontine nuclei into less compact bundles.

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Where is this slice from?

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Caudal pons. 4th ventricle, inferior cerebellar peduncle, pontine nuclei and longitudinal pontine bundles (some of which are coalescing to soon become pyramids)

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Medial lemniscus

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Tectospinal fibers

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Medullary pyramid

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Erb's palsy

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Nerve injury to C5-C6 roots, with the suprascapular, musculocutaneous, and axillary being damaged most often. Loss of elbow flexion, supination, leads to "waiter's tip". Shoulder dystocia during childbirth is a common cause.

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Klumpke's palsy

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Primarily affects the lower roots of the brachial plexus (C8 - T1). Leads to weakness of the intrinsic hand muscles and flexors of the wrist and fingers. "Klumpke the monkey hung from a tree".

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Nerve branches of the posterior cord of the brachial plexus

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ARTS: axillary, radial, thoracodorsal, subscapular (upper and lower).

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5 parts of the brachial plexus

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Roots, Trunks, Divisions, Cords, Branches. Mnemonic: Russell Trigonis Drinks Cold Beers.

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Nerve roots of lumbosacral plexus

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L1 - S4

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What are the motor actions and sensory innervations of the median nerve?

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Motor: Thumb flexion and opposition, flexion of digits 2 and 3, wrist flexion and abduction, forearm pronation.

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What are the motor actions and sensory innervations of the ulnar nerve?

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Motor: Finger adduction and abduction other than thumb; thumb adduction; flexion of digits 4 and 5; wrist flexion and adduction

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What are the motor actions and sensory innervations of the musculocutaneous nerve?

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Motor: Flexion of arm at elbow, supination of forearm

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3 nerves acting on the thumb movement

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Radial: abducts thumb (plane of palm)
Ulnar: adducts thumb (plane of palm)
Median: opposes thumb, and abducts thumb (perp. to plane of palm)

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What are the motor actions and sensory innervations of the femoral nerve?

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Motor: Leg flexion at the hip, leg extension at the knee

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What are the motor actions and sensory innervations of the obturator nerve?

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Motor: Adduction of the thigh

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What are the motor actions and sensory innervations of the tibial nerve?

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Motor: Foot plantar flexion and inversion, toe flexion

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What are the motor actions and sensory innervations of the superficial peroneal nerve?

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Motor: Foot eversion

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What are the motor actions and sensory innervations of the deep peroneal nerve?

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Motor: Foot dorsiflexion, toe extension

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What innervates the hamstring muscles (for knee flexion)?

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Sciatic nerve

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What are the conduction speeds for A-delta and C fibers?

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A-delta fibers: 15 - 30 m/s
C fibers: 0.5 - 2 m/s

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Foramen Ovale:
Mandibular nerve (V3), Accessory Meningeal Artery, Lesser Petrosal nerve

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Optic canal:
Optic nerve (CNII), opthalmic artery

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Superior orbital fissure:
Oculomotor nerve (CNIII), trochlear nerve (CNIV), abducens nerve (CNVI), opthalmic nerve (V1), superior opthalmic vein

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Foramen rotundum:
Maxillary nerve (V2)

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Jugular foramen:
Glossopharyngeal nerve (IX), Vagus nerve (X), Accessory nerve (XI), Sigmoid sinus, Posterior meningeal artery, inferior petrosal sinus

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Foramen lacerum:
Greater petrosal nerve, internal carotid (via the carotid canal)

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Asterion

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Glabella

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Gonion

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Greater wing of sphenoid

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Rhinion

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Hoffman's reflex

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Test for UMN lesion - Flicking the middle finger to check for reflex contraction of the thumb or index finger. The positive response is abnormal if asymmetric and could be a normal finding if symmetric (e.g. hyperreflexia). Ex. testing for cervical myelopathy.

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Frontal process of the zygomatic bone

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Frontomaxillary suture

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Zygomatic process of the temporal bone

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Infraorbital foramen

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Frontonasal suture

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Middle nasal concha

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Greater palatine foramen

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The anterior spinal artery supplies what portion of the spinal cord?

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ASA supplies anterior 2/3 and PSA's supply posterior 1/3.

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Artery of Adamkiewicz

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A branch off of the thoracic aorta (variable) that supplies the anterior spinal artery (as an "anterior segmental medullary artery). Provides blood supply to anterior cord below T11-T12.

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CN VIII, Vestibulocochlear nerve passing through the internal acoustic meatus

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CN VII, Facial nerve passing through the internal acoustic meatus

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CN VI, Abducens nerve - will pass through the superior orbital fissure.

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CN XI, Spinal accessory - will pass through the jugular foramen.

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Nerve roots of femoral nerve

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L2 - L4

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Nerve roots of common peroneal nerve

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L4 - S2

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Nerve roots of sciatic nerve

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L4 - S3

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Nerve roots of tibial nerve

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L4 - S3

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Nerve roots of superficial peroneal nerve

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L5 - S2

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Nerve roots of deep peroneal nerve

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L4 - L5

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Nerve roots of dorsiflexion

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L4*, L5

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Nerve roots of toe extension

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L4, L5*

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Nerve roots of plantar flexion

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L5, S1*, S2

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Nerve roots of toe flexion

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S2, S3

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Nerve roots of foot eversion

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L5*, S1*, S2

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Nerve roots of superior gluteal

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L4 - S1

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Nerve roots of inferior gluteal

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L5 - S2

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Nerve roots of obturator nerve

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L2 - L4

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Nerve roots of finger extension

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C7*, C8

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Thumb abduction in the plane of the palm

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Radial nerve (C7*, C8)

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Finger abduction

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Ulnar nerve (C8, T1*)

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Lumbricals: function and innervation

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Flexion of the metacarpophalangeal joints, extension of the interphalangeal joints.