M1 Anatomy Flashcards

Question

Facial Nerve

Answer 1

* 7th Cranial Nerve (VII) * Emerges from Pons * Afferent: taste for anterior 2/3rd of tongue * Efferent: muscles of facial expression

Answer 2

* Pons * Internal Auditory Meatus * Facial Canal in Temporal bone * Stylomastoid Foramen

Answer 3

* 8th Cranial Nerve (VIII) * Afferent: sound and equilibrium * Pons

Answer 4

1. Internal Acoustic Meatus 2. Pontomedullary junction 3. Pons

Answer 5

* 9th Cranial Nerve (IX) * Joins brainstem from sides of upper medulla oblongata * Exits skull via jugular foramen * Efferent: * Stylopharyngeal muscle * Parasympathetics to Parotid * Afferent: * Carotid sinus and body * tympanic membrane * Upper pharynx * Posterior 1/3 tongue: taste and sensation

Answer 6

* 10th Cranial Nerve (X) * Longest autonomic nerve in the body * Leave medulla between pyramid and cerebellar peduncle * Leaves skull via jugular foramen * Motor and sensory of viscera to colon

Answer 7

* 11th Cranial Nerve (XI) * Motor neuron to SCM and Trapezius * Neuron body in spinal cord * Enters skull via foramen magnum * Exits skull via jugular foramen

Answer 8

* 12th Cranial Nerve (XII) * Motor neuron to all extrinsic and intrinsic muscles of tongue * except palatoglossus * Arises from small rootlets anterior medulla oblongata * Exits skull via hypoglossal canal

Answer 9

* Canal between orbit and middle cavity of skull in Sphenoid bone * Optic foramen is opening * Contains Optic Nerve (CN II) and Ophthalmic artery

Answer 10

* Cleft between lesser and greater wings of sphenoid. * Contains: * Oculomotor Nerve (CN III) * Trochlear Nerve (CN IV) * 3 branches of Ophthalmic Nerve (CN V1) * lacrimal * frontal * nasociliary * Abducens Nerve (CN VI) * Ophthalmic Vein

Answer 11

* Sphenoid bone * Connects middle cranial fossa with pterygopalatine fossa * Contains Maxillary Nerve (CN V2)

Answer 12

* posterior part of the sphenoid bone, posterolateral to the foramen rotundum in Greater Wing. * Middle cranial fossa * Contents * O: otic ganglion (inferior) * V: V3 cranial nerve (mandibular division of the trigeminal nerve) * A: accessory meningeal artery * L: lesser petrosal nerve * E: emissary veins

Answer 13

* Temporal bone * Termination of Facial Canal * Transmits * Facial Nerve (CN VII) * Stylomastoid artery

Answer 14

* Petrous portion of Temporal bone * Connects Posterior Cranial Fossa with inner ear * Contents * Facial Nerve (CN VII) * Vestibulocochlear Nerve (CN VIII) * Labyrinthine artery * Vestibular ganglion

Answer 15

* Petrous portion of temporal bone and occipital bone * Contents * Interior petrossal sinus * Sigmod sinus * Glossopharyngeal Nerve (CN IX) * Vagus Nerve (CN X) * Accessory Nerve (CN XI)

Answer 16

* Occipital bone * Medial and superior to occipital condyles * Transmits Hypoglossal Nerve (CN XII)

Answer 17

* Occipital Bone * Contents: * Anterior and Posterior spinal arteries * Vertebral arteries * Medulla Oblongata * Ascending fibers of Accessory Nerve (CN XI)

Answer 18

* Oculomotor (CN III) * Trochlear (CN IV) * Abducens (CN VI)

Answer 19

1. Midbrain or mesencephalon 2. Pons 3. Medulla Oblongata

Answer 20

* vision * hearing * motor control * sleep/wake, arousal (alertness) * temperature regulation

Answer 21

* tectum (posterior) * cerebral aqueduct * tegmentum * cerebral peduncles.

Answer 22

* Superior aspect of brainstem * Rostral: diencephalon * Caudal: Pons and Cerebellum

Answer 23

* Timeline * Begins at 6-12 weeks in utero * Begins unifying at 4 years old * Finishes unifying by 6 years old * Joins with sphenoid between 18 - 25 years old * 6 centers, all primary

Answer 24

5 Total 1 - centrum for body 2 - each half of neural arch 2 - dens

Answer 25

2 Total 1 - tip of dens 1 - lower surface of body

Answer 26

3 total start at 9 weeks in utero finish by one year 1 - centrum for body 2 - each half of neural ring

Answer 27

5 Total Appear at puberty and finish by 25-30 years old 1 - tip of SP 2 - tip of TPs 2 - ring epiphyses at upper and lower body surfaces

Answer 28

3 primary centers No secondary centers 1 - Anterior arch (fuses by age 7) 2 - each side of posterior arch (fuses by age 3)

Answer 29

1. Dens Primary centers fuse by 7th month in utero 2. 2-3 yo: Neural arch fuses posteriorly 3. 3-6 yo: Neural arch fuses to body and dens 4. 3-6 yo: Dens fuses with body 5. 3-6 yo: tip of dens appears 6. 12 yo: tip of dens fuses with dens

Answer 30

1. 8 Cranial bones 2. 14 Facial bones Total 22 bones

Answer 31

1. Occipital bone 2. 2 Temporal bones 3. 2 Parietal bones 4. Frontal bone 5. Sphenoid bone 6. Ethmoid bone

Answer 32

1. 2 inferior nasal conchae 2. 2 lacrimal bones 3. 2 maxilla bones 4. 2 nasal bones 5. 2 palatine bones 6. 2 zygomatic bones 7. mandible 8. vomer

Answer 33

* Passageway in temporal bone from neck to middle cranial fossa. * Contains: * Internal Carotid Artery * Carotid Plexus of nerves * Sympathetics to head from Superior Cervical Ganglion

Answer 34

* Greater wing of sphenoid connecting middle cranial fossa and neck. * Contains: * Middle meningeal artery * Middle meningeal vein * Meningeal branch of Mandibular Nerve (CN V3)

Answer 35

Where the brainstem and spinal cord meet in the Foramen Magnum

Answer 36

Stylohyoid Stylopharyngeus Styloglossus

Answer 37

Stylohyoid - CN VII Facial Stylopharyngeus - CN IX Glossopharyngeal Styloglossus - CN XII Hypoglossal

Answer 38

Convergence of lambdoid and saggital sutures

Answer 39

Convergence of coronal and sagittal sutures

Answer 40

Apical ligament

Answer 41

between basion and opisthion

Answer 42

between hard palate and opisthion

Answer 43

between hard palate and inferior most portion of occiput

Answer 44

most anterior portion of frontonasal suture

Answer 45

Normal position of the tip of the dens is 5mm below. Above this line it is a sign of basilar invagination.

Answer 46

If tip of dens is greater than 3mm above it indicates basilar invagination

Answer 47

Angle between posterior aspect of Clivus and posterior border of axial peg.

Answer 48

Angle should be 150-180 degrees. Less than 150 indicates possible compression of the contents of the foramen magnum. Less than 130 associated with delay or failure to recover after foramen magnum decompression.

Answer 49

The neuraxis stretches by about 10% of its total length on CCJ flexion.

Answer 50

Ratio of distance of two lines Basion to C1 spinolaminar line (BC) divided by C1 anterior arch to Opistion (AO)

Answer 51

If BC/AO is \>1 indicates possible anterior atlanto-occipital dissociation

Answer 52

Cranial Base Angle represents skull base curvature * normal: 125°-143° * platybasia: \>143° * basilar kyphosis: \<125° The more obtuse this angle the more retrognathic the mandible becomes.

Answer 53

Line at base of anterior cranial fossa to tip of dorsum sellae with clivus angle Normal is 114 - 134

Answer 54

Line drawn from basion to posterior inferior C2 body A perpendicular line drawn to dura A value of 9mm or more indicates ventral brainstem compression.

Answer 55

Basion Axial distance and Basion Dental interval should both be less than 12mm (Rule of 12s)

Answer 56

distances of greater than 12mm is an indication of **craniocervical instability.** Rule of 12s

Answer 57

No, dural venous drainage does NOT follow the arteries of the brain.

Answer 58

The veins of the brain do not follow the arteries, but instead, drain into the dural sinuses, which subsequently drain into the internal jugular vein.

Answer 59

Visceral periosteum and dural reflection lined with endothelium.

Answer 60

The Inferior Sagittal and Straight Sinuses both lack bony components as part of their wall.

Answer 61

"ag" is arachnoid granulations

Answer 62

"s" is a sagittal sinus pocket

Answer 63

"SL" is the sagittal sinus (superior)

Answer 64

"VC" is a draining cortical vein

Answer 65

Area of bone where confluence of sinuses is located

Answer 66

Where Straight Sinus and Transverse Sinuses join

Answer 67

Superior Sagittal Sinus often becomes the Right Transverse Sinus. Straight Sinus often becomes the Left Transverse Sinus.

Answer 68

Superior and Inferior Petrosal sinuses.

Answer 69

Drains the temporal lobe to the Transverse Sinus

Answer 70

Drains into Superior Sagittal Sinus Largest Cortical Vein

Answer 71

Inferior Petrosal Sinus and Sigmoid Sinus

Answer 72

Drain into the Straight Sinus * Inferior Sagittal Sinus * Thalamostriate Veins * Internal Cerebral Veins

Answer 73

Connects the Inferior Petrosal Sinuses Lies on the Clivus

Answer 74

1. Anterior Condylar Vein 2. Lateral Condylar Vein 3. Anterior Condylar Confluence

Answer 75

Drains from the The confluence of Sinuses to Marginal Sinus

Answer 76

Drains from the Sigmoid Sinus to the Suboccipital Cavernous Sinus via posterior condyloid canal

Answer 77

1. Sub-occipital Cavernous Sinus 2. Marginal Sinus 3. Internal Vertebral Venous Plexus

Answer 78

a small parasympathetic ganglion located immediately below the foramen ovale in the infratemporal fossa and on the medial surface of the mandibular nerve. It is functionally associated with the glossopharyngeal nerve and innervates the parotid gland for salivation.

Answer 79

Otic Ganglion Ciliary Ganglion Submandibular Ganglion Pterygopalating Ganglion

Answer 80

3 years old.

Answer 81

Odontoid centrally.

Answer 82

V3: Mandibular

Answer 83

McGregor's Line

Answer 84

Petrosal Sinus

Answer 85

2. Sub-occipital sinus

Answer 86

4. The vertebral arteries turn posteriorly around the lateral masses of the atlas.

Answer 87

5. Anterior Choroidal Artery

Answer 88

3. 3rd and 4th Ventricles

Answer 89

3. Innervation: C2 The Rectus Capitus Posterior Major muscle is innervated, as are all four suboccipital muscles, by the suboccipital nerve (posterior ramus of C1).

Answer 90

5. 1, 2, and 4 The Levator Scapula can laterally flex the spine or rotate and elevate the scapula.

Answer 91

The Internal Carotid is anterior and medial to the Internal Jugular just outside the skull.

Answer 92

Under the occiput in the suboccipital compartment deep to the sternocleidomastoid, trapezius, splenius and semispinalis muscles.

Answer 93

They collectively act to extend and rotate the head.

Answer 94

Suboccipital nerve, from the posterior ramus of C1.

Answer 95

1. Internal Carotid 2. Vertebral basilar

Answer 96

Posterior communicating artery and rostral.

Answer 97

Posterior Cerebral artery and inferior

Answer 98

Post 1/3 taste and sensation : CN IX (glossopharyngeal) Anterior 2/3 taste: CN VII (facial) Anterior 2/3 sensation: CN V3 (mandibular)

Answer 99

1. Optic (II): Sensation of light 2. Oculomotor (III): 1. Most extraocular muscles 2. levator palpebrae superioris (upper lid) 3. iris sphincter (PaSNS) pupillary constriction (miosis) 4. ciliary muscle (PaSNS) contracture for accommodation. 3. Trochlear (IV): superior oblique (down and in) 4. Ophthalmic (V₁): 1. Sensory innervation 2. afferent part of the corneal and lacrimation reflex 5. Abducens (VI): lateral rectus (abduction) 6. Facial (VII): 1. Eye closure and blinking 2. efferent part of the corneal and lacrimation reflex 7. Long ciliary n. (superior cervical chain - SNS) pupillary dilation by contracture of iris dilator muscle [https://www.ncbi.nlm.nih.gov/books/NBK549919/#:~:text=Six%20cranial%20nerves%20innervate%20motor,facial%20nerve%20(CN%20VII).](https://www.ncbi.nlm.nih.gov/books/NBK549919/#:~:text=Six%20cranial%20nerves%20innervate%20motor,facial%20nerve%20(CN%20VII).)

Answer 100

The cerebellar tonsil is part of the posterior lobe of the cerebellum, also known as the neocerebellum, which is responsible for coordinating the voluntary movement of the distal parts of limbs

Answer 101

The flocculonodular lobe has important connections to the vestibular nuclei and uses information about head movement to influence eye movement. Lesions to this area can result in multiple deficits in visual tracking and oculomotor control (such as nystagmus and vertigo), integration of vestibular information for eye and head control, as well as control of axial muscles for balance. This lobe is also involved in the maintenance of balance equilibrium and muscle tone.

Answer 102

the vermis is associated with bodily posture and locomotion. The vermis is included within the spinocerebellum and receives somatic sensory input from the head and proximal body parts via ascending spinal pathways

Answer 103

The thalamus has several functions, such as the relaying of sensory signals, including motor signals to the cerebral cortex and the regulation of consciousness, sleep, and alertness.

Answer 104

The fornix is a C-shaped bundle of nerve fibers in the brain that acts as the major output tract of the hippocampus. The fornix also carries some afferent fibers to the hippocampus from structures in the diencephalon and basal forebrain. The fornix is part of the limbic system.

Answer 105

The corpos callosum spans part of the longitudinal fissure, connecting the left and right cerebral hemispheres, enabling communication between them. It is the largest white matter structure in the human brain

Answer 106

the cingulate gyrus is highly influential in linking motivational outcomes to behavior (e.g. a certain action induced a positive emotional response, which results in learning). Part of the limbic system

Answer 107

The telencephalon, commonly called the cerebral hemispheres, is the largest portion of the central nervous system (CNS) and consists of the cerebral cortex, subcortical white matter (commissural, association, and projection fibers), and basal nuclei.

Answer 108

Atlanto-Axial Rotary Fixation

Answer 109

Atlanto-Axial Rotary Fixation

Answer 110

Atlanto-Axial Rotary Fixation

Answer 111

Atlanto-Axial Rotary Fixation

Answer 112

Clinical considerations Larger lever arm Greater capacity to exert torque Local segmental instability if used in absence of deep muscle activation (Winters etal).

Answer 113

Clinical Consideration Contribute to fine control of head movement Segmentally arranged Shorter, stiffer (Toursel etal 2002) Higher spindle density More involved in postural support (due low-threshold, slow twitch characteristics) Boyd etal (2002)

Answer 114

1. Longus Capitis, 2. Longus Colli, 3. Rectus Capitus Anterior

Answer 115

a) Extension in the upper cervical region b) Flexion in the lower cervical region

Answer 116

1. Levator Scapulae 2. Trapezius (upper)

Answer 117

The mechanical properties of the atlanto- occipital joint are primarily determined by bony structures, whereas those of the atlanto-axial joint are primarily determined by ligamentous structures.

Answer 118

The predominant movements at the atlanto-occipital joint are flexion and extension. Lateral flexion at the atlanto-occipital joint is significantly limited by the contralateral alar ligament.

Answer 119

The ligaments (transverse ligament and alar ligaments) related to this particular articulation which stabilise the joint complex. In the event of traumatic disruption of these ligaments, the atlanto-axial joints are poorly equipped to tolerate axial rotation.

Answer 120

attach the axis to the base of the skull and originate from the posterior surface of the upper third of the dens and typically travel caudocranially (in 50 % of cadeveric dissections) or horizontally (in 50 % of subjects). Each ligament is narrowest at its origin and comparatively wider at its insertion giving it a “V-shaped” configuration The alar ligaments limit axial rotation and lateral flexion on the contralateral side and, apart from the transverse ligament, are the strongest stabilisers of the atlas preventing anterior displacement in the event of rupture of the transverse ligament.

Answer 121

The cruciform ligament is composed of transverse and vertical parts which form a cross behind the odontoid peg. The vertical component which is relatively weak and offers no discernible craniocervical stability consists of a cranially orientated longitudinal band which inserts on to the upper surface of the clivus between the apical ligament and tectorial membrane and a caudally directed band which inserts on to the posterior surface of the body of the axis.

Answer 122

arguably the most important ligament in the body. It is the largest, thickest and, crucially, the strongest of the craniocervical junction ligaments (and, in fact, the strongest ligament in the entire spine) and, therefore, a primary stabiliser of the craniocervical junction. The transverse ligament serves as the major stabiliser of the atlanto-axial articulation: it permits rotation at the atlanto-axial joints while, at the same time, the alar ligaments will prevent excessive rotation. Tears of the transverse ligament typically occur laterally at the attachment to the tubercle on the atlas.

Answer 123

an upward extension of the posterior longitudinal ligament

Answer 124

This ligament extends from the tip of the odontoid process to the basion and is situated between the anterior atlanto-occipital membrane and the cruciform ligament It may be absent in up to 20 % of subjects

Answer 125

anterior aspect of the atlas to the anterior rim of the foramen magnum and is located immediately posterior to the prevertebral muscles It serves to limit atlanto-occipital extension at the craniocervical junction.

Answer 126

believed to play very little part in stability of the atlantooccipital articulation This broad ligament attaches the posterior arch of the atlas to the posterior margin of the foramen magnum and is continuous with the posterior atlantoaxial membrane and, subsequently, the ligamentum flavum Interdigitations with both the dura mater and the related rectus capitis posterior minor muscle parenchyma may be present in this ligament; additionally, a connective tissue bridge (exhibiting increased vascularity) joining the rectus capitis posterior minor muscle to the spinal dura is frequently present, particularly in the midline. This myoligamentous complex (comprising the posterior atlanto-occipital membrane, interspinous ligament, ligamentum nuchae, rectus posterior major and minor muscles and obliquus capitis supripr and inferior muscles) adds further stability to the craniocervical junction

Answer 127

This is a cephalic extension of the supraspinous ligament and extends from the spinous process of the C7 vertebra attaching to the inion of the occipital bone. A sturdy structure, it limits hyperflexion of the cervical spine

Answer 128

The persistent ossiculum terminale results from failure of fusion of the secondary ossification centre (“terminal ossicle”) to the remainder of the odontoid process which has usually occurred by 12 years of age. It may be confused with a (type I) odontoid fracture. Identification of a smooth corticated margin is, again, central to discriminating the two aetiologies

Answer 129

a separate ossicle with a smooth cortical border lying superior to a small hypoplastic dens and body of the axis in the location of the odontoid process The anterior arch of the atlas may be rounded and hypertrophic in contrast to the normal anterior arch morphology. While the (type II) odontoid fracture is typically associated with a flattened uncorticated sharp margin to the adjacent body of the axis and normal morphology to the anterior arch of the atlas, the os odontoideum exhibits a well-corticated convex upper margin and rounded hypertrophic anterior atlas arch

Answer 130

Rarely, nodular calcification/ossification can be seen in the alar ligament which can mimic type III fracture of the occipital condyle or type I fracture of the odontoid process

Answer 131

Traumatic alar ligament injuries typically occur near the condylar insertion. Alar ligament failure predisposes to excessive axial rotation with resultant compression of or dissection injury to the vertebral artery and damage to the spinal accessory nerves

Answer 132

is relatively rare in the adult population, occurring more commonly in the paediatric population. In adults, the most common cause is trauma. when the head is rotated normally, the neighbouring segments of the vertebral arteries are structurally affected: the ipsilateral vertebral artery will be kinked and the contralateral vertebral artery will be stretched. Clinically, patients may demonstrate torticollis and adopt the cock-robin position of the head (because of the apparent descriptive resemblance of a robin listening for a worm in the ground) and occipital pain may occur as a result of compression of the greater occipital nerve or the C2 nerve root. Patients may also experience vertigo, nausea, tinnitus and visual disturbances, possibly related to haemodynamic compromise of the vertebral artery. Spasmodic torticollis (sternocleidomastoid muscle spasm) should be distinguished clinically from AARS—in the former, the shortened sternocleidomastoid on the side contralateral to the direction of head rotation is creating the force producing the deformity, whereas in the latter, the lengthened sternocleidomastoid muscle on the side ipsilateral to the direction of head rotation demonstrates spasm in an attempt to correct the deformity

Answer 133

1) each DL is composed of a single narrow fibrous strip that extends from the craniovertebral junction to T12, and each also features 18-20 triangular extensions that attach to the dura at their apices; (2) the triangular extensions are smaller and more numerous at the cervical levels, and are larger and less numerous at the thoracic levels; (3) the apices of the extensions attach to the dura via fibrous bands at cervical levels (each band 3-5 mm long) and lower thoracic levels (21-26 mm long), whereas they attach directly to the dura at upper thoracic levels; (4) the narrow fibrous strip of the DL features longitudinally oriented collagen fibers, whereas the triangular extensions are composed of transverse and obliquely oriented collagen fibers. The collagen fibers are thicker and more abundant at the cervical than at the thoracic levels. (5) The first (superiormost) pair inserts into the lateral borders of the foramen magnum, with the vertebral artery anterior to them and the hypoglossal nerve (CN XII) posterior. The inferiormost pair is at the level of the conus medullaris, namely, between the T12 and L1 segmental nerve roots, and its pia mater fuses with the filum terminale. (6) Each triangular ligament has a vertically oriented base that emanates from the spinal cord between the exit point of the ventral root and entry point of the dorsal root, and an apex which points laterally and attaches to the dura mater just posterosuperior to the neural foramen [https://pubmed.ncbi.nlm.nih.gov/22555553/](https://pubmed.ncbi.nlm.nih.gov/22555553/) [https://radiopaedia.org/articles/denticulate-ligaments?lang=us](https://radiopaedia.org/articles/denticulate-ligaments?lang=us)

Answer 134

The dorsal meningovertebral ligaments in the cervical region anchored the posterior dural sac to the ligamentum flavum or laminae. the occurrence rate of dorsal meningovertebral ligaments was 100% at C1-C2 and C4--C5. The thickest ligaments were observed at the C1 and C2 vertebrae. the orientation of the ligaments mostly was craniocaudal. At C1 & C2 the Dorsal Meningovertebral Ligaments become thicker and become known as Myodural bridges” Case courtesy of Dr Matt Skalski, Radiopaedia.org, rID: 65838

Answer 135

Anatomical soft tissue bridges which cross the cervical epidural space, connecting suboccipital muscle fascia and dura have passive and active functions to anchor the spinal cord. These myodural bridges may be involved in a dural tension monitoring system to prevent dural infolding and maintain patency of the spinal cord. Failure of this system could result in altered cerebral spinal fluid flow, changes in sensorimotor function, cervicocephalic headaches, and dural related pathologies. the Superior Myodural bridge connects the RCPMi fascia to the dura via the Occipito-atlantal interspace. The Inferior Myodural bridge connects the fascia of the RCPMa and OCI to the dura via the Atlanto-axial interspace. [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4025088/pdf/jcca\_v58\_2j\_p184-enix.pdf](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4025088/pdf/jcca_v58_2j_p184-enix.pdf)

Answer 136

total CSF volume in the adult is approximately **130 ml** of which about **60 ml** is contained within the cranial cavity and about **70 ml** is stored within the vertebral canal.

Answer 137

**Nutrition:** The intervertebral discs, like other cartilages, have no blood supply. (outer 1/3?). They form the largest structures in the body without their own blood vessels. The nutrients they require are absorbed from circulating blood by means of **osmosis**. **Innervation:** The intervertebral disc is innervated through the **sinovertebral nerves**. The nerve fibres are mainly restricted to the outer lamellae in the endplate. Most of those sinovertebral nerves are meningeal branches of spinal nerves.

Answer 138

CN V CN X C1-3

Answer 139

Cardiac Respiration Vasomotor (autonomic)

Answer 140

The brain, blood and CSF are the space-occupying components of the cranium and they must co-exist in a state of dynamic equilibrium. A change in volume in one component requires a change in volume in either or both of the other two. Systole (brainstem and CSF move caudally) Diastole (brainstem and CSF move cephalad)

Answer 141

* generated by spontaneous pulsations of arterial, venous and lymphatic vessels. * independent of the respiratory and cardiac cycles * generally longer wavelengths than those of the respiratory and cardiac * mediated by the autonomic nervous system and * along with increased heart rate variability, are considered to be markers of good autonomic balance.

Answer 142

* intracranial arteries cause the propagation of waves of elevated intracranial pressure * first described Lundberg described C waves as rhythmic oscillations with a frequency of 4–8 per minute (most frequently 6 per minute) and an amplitude of up to 20 mm Hg. * Because of the close association between C waves and Traube-Herring Mayer waves, any effect of C waves is probably a healthy one”

Answer 143

* Located in midbrain * Lesion affect is contralateral * Plays an important role in locomotion and several theories suggest that it has evolved dramatically with the advent of bipedalism.

Answer 144

The reticular formation is made up of a net-like structure of various brainstem nuclei and neurons and covers an expansive portion of the brainstem, beginning in the mesencephalon, extending caudally through the medulla oblongata, and projecting into the superior cervical spinal cord segments. Due to the expansive network of tracts and the interconnected structure, the reticular formation functions as an integration, relay, and coordination center for many vital life functions and controls many of the protective reflexes. Regulator of arousal and consciousness Modifies reflex activity and muscle tone Modulates somatic and visceral sensation (regulation of pain perception) Coordinates respiratory centres that control the muscles of respiration Works with vestibular apparatus to preserve muscle tone in antigravity muscles Present bilaterally able to provide motor control to both sides of the brain when a person laughs or smiles

Answer 145

* Anterior/Superior semicircular canal is situated perpendicular to the temporal bone and detects motion in the sagittal plane - nodding * Lateral/Transverse semicircular canal (smallest & horizontal) detects rotation of the head in the transverse plane - no * Posterior semicircular canal detects rotation in the coronal/frontal plane – tilting * Note: Superior Semicircular Canal Dehiscence - the only canal not fully enclosed by bone but by dura at it’s superior most reach (if this herniates creates a third window to exchange CSF)

Answer 146

Impaired function of the spinal cord caused by degenerative changes of the discs and facet joints in the cervical spine compressing the cord. Common Symptoms: neck stiffness, arm pain, clumsy or weak hands, numbness in the hands, and weakness of the hands and legs, unsteady gait, hesitancy on urination DDx: multiple sclerosis, amyotrophic lateral sclerosis and masses (such as metastatic tumors) that press on the spinal cord Common signs: atrophy of the hand musculature, , sensory loss hyperreflexia, Lhermitte's sign (electric shock-like sensation down the center of the back following flexion of the neck) Hoffman Sign: a reflex contraction of the thumb and index finger after nipping the middle finger

Answer 147

C1 Upper Cervical Flexion C2 Upper Cervical Extension C3 Cervical Lateral Flexion C4 Shoulder Girdle Elevation C5 Shoulder Abduction C6 Elbow Flexion C7 Elbow Extension C8 Thumb Extension T1 Finger Adduction