anatomy and physiology

Question 1

what is Syringomyelia?

Answer 1

Cystic cavity (syrinx) within central canal of spinal cord. associated with chiari malformations,trauma,tumors

Question 2

Tract affected in syringomyelia and result

Answer 2

Fibers crossing in anterior white commissure (spinothalamic tract) are typically damaged first. Results in a “cape-like,” bilateral loss of pain and temperature sensation in upper extremities (fine touch sensation is preserved).

Question 3

Chiari 1 malformation

Answer 3

cerebellar tonsillar ectopia > 3–5 mm; congenital, usually asymptomatic in childhood, manifests with headaches and cerebellar symptoms.

Question 4

Anencephaly

Answer 4

Malformation of anterior neural tube Žno forebrain, open calvarium. Clinical findings:  AFP, polyhydramnios (no swallowing center in brain). Associated with maternal type 1 diabetes. Maternal folate supplementation  risk.

Question 5

holoprosencephaly

Answer 5

Failure of left and right hemispheres to separate; usually occurs during weeks 5–6. May be related to mutations in sonic hedgehog signaling pathway. Moderate form has cleft lip/palate, most severe form results in cyclopia. Seen in Patau syndrome and fetal alcohol syndrome.

Question 6

chiari 2 malformations

Answer 6

Herniation of low-lying cerebellar vermis through foramen magnum with aqueductal stenosis Žhydrocephalus. Usually associated with lumbosacral meningomyelocele (paralysis/sensory loss at and below the level of the lesion).

Question 7

Dandy Walker syndrome

Answer 7

Agenesis of cerebellar vermis with cystic enlargement of 4th ventricle (fills the enlarged posterior fossa A). Associated with noncommunicating hydrocephalus, spina bifida.

Question 8

Neurons

Answer 8

1.Signal-transmitting cells of the nervous system. 2.Permanent cells(do not divide in adulthood).
3.Signal-relaying cells with dendrites (receive input), cell bodies, and axons (send output).
4.Cell bodies and dendrites can be seen on Nissl staining (stains RER).
RER is not present in the axon.
Injury to axon ŽWallerian degeneration—degeneration distal to injury and axonal retraction proximally; allows for potential regeneration of axon (if in PNS).

Question 9

astrocytes

Answer 9

Physical support, repair, K+ metabolism, removal of excess neurotransmitter, component of bloodbrain barrier, glycogen fuel reserve buffer. Reactive gliosis in response to neural injury. Astrocyte marker: GFAP. Derived from neuroectoderm.

Question 10

microglia

Answer 10

Phagocytic scavenger cells of CNS (mesodermal, mononuclear origin). Activated in response to tissue damage. Not readily discernible by Nissl stain.
HIV-infected microglia fuse to form multinucleated giant cells in CNS.

Question 11

myelin

Answer 11

 conduction velocity of signals transmitted down axons Žsaltatory conduction of action potential at the nodes of Ranvier, where there are high concentrations of Na+ channels. CNS—oligodendrocytes; PNS—Schwann cells.
Wraps and insulates axons A:  space constant and  conduction velocity.

Question 12

schwann cell

Answer 12

Each Schwann cell myelinates only 1 PNS axon. Also promote axonal regeneration. Derived from neural crest.  conduction velocity via saltatory conduction at the nodes of Ranvier, where there is a high concentration of Na+ channels.
May be injured in Guillain-Barré syndrome. Vestibular schwannoma—typically located on CN VIII in internal acoustic meatus, may extend to cerebellopontine angle

Question 13

oligodendroglia

Answer 13

Myelinates axons of neurons in CNS. Each oligodendrocyte can myelinate many axons (∼ 30). Predominant type of glial cell in white matter.
Derived from neuroectoderm. “Fried egg” appearance histologically. Injured in multiple sclerosis, progressive multifocal leukoencephalopathy (PML), leukodystrophies.

Question 14

functions of hypothalmus

Answer 14

Thirst and water balance, Adenohypophysis control (regulates anterior pituitary), Neurohypophysis releases hormones produced in the hypothalamus, Hunger, Autonomic regulation, Temperature regulation, Sexual urges. Inputs (areas not protected by blood-brain barrier): OVLT (organum vasculosum of the lamina terminalis; senses change in osmolarity), area postrema (found in medulla, responds to emetics). Supraoptic nucleus primarily makes ADH. Paraventricular nucleus primarily makes oxytocin. Hypothalamus makes ADH and oxytocin. They are carried by neurophysins down axons to posterior pituitary, where they are stored and released.

Question 15

lateral hypothalmus

Answer 15

hunger,Destruction Ž anorexia, failure to thrive (infants). Stimulated by ghrelin, inhibited by leptin.

Question 16

ventromedial hypothalmus

Answer 16

Satiety. Destruction (eg, craniopharyngioma) Ž hyperphagia. Stimulated by leptin.

Question 17

anterior hypothalmus

Answer 17

cooling, parasympathetic

Question 18

posterior hypothalmus

Answer 18

heating symathetic

Question 19

suprachiasmatic nucleus

Answer 19

circadian rhythm

Question 20

BBB structures

Answer 20

1. Tight junctions between nonfenestrated capillary endothelial cells
2. ƒBasement membrane
3. ƒAstrocyte foot processes

Question 21

Poliomyelitis and Werdnig-Hoffmann disease

Answer 21

Congenital degeneration of anterior horns of spinal cord. LMN lesions only. “Floppy baby” with marked hypotonia and tongue fasciculations. Infantile type has median age of death of 7 months. Autosomal recessive inheritance. Poliomyelitis Žasymmetric weakness. Werdnig-Hoffmann disease Žsymmetric weakness

Question 22

Amyotrophic lateral sclerosis

Answer 22

Combined UMN and LMN deficits with no sensory or bowel/bladder deficits (due to loss of cortical and spinal cord motor neurons, respectively). Can be caused by defect in superoxide dismutase 1. Commonly presents with asymmetric limb weakness (hands/feet), fasciculations, eventual atrophy. Fatal. Commonly known as Lou Gehrig disease. Treatment: riluzole.

Question 23

Complete occlusion of anterior spinal artery

Answer 23

Spares dorsal columns and Lissauer tract; upper thoracic ASA territory is watershed area, as artery of Adamkiewicz supplies ASA below ∼ T8.

Question 24

tabes dorsalis

Answer 24

Caused by 3° syphilis. Results from degeneration (demyelination) of dorsal columns and roots Žprogressive sensory ataxia (impaired proprioception Žpoor coordination). Associated with Charcot joints, shooting pain, Argyll Robertson pupils. Exam will demonstrate absence of DTRs and ⊕Romberg sign.

Question 25

syringomyelia

Answer 25

Syrinx expands and damages anterior white commissure of spinothalamic tract (2nd-order neurons) Ž bilateral loss of pain and temperature sensation in cape-like distribution; seen with Chiari I malformation; can expand and affect other tracts.

Question 26

b12 deficiency

Answer 26

Subacute combined degeneration (SCD)— demyelination of Spinocerebellar tracts, lateral Corticospinal tracts, and Dorsal columns. Ataxic gait, paresthesia, impaired position/vibration sense.