21 - The Nervous System Flashcards
(41 cards)
CNS, central nervous system consists of…
the brain and spinal cord
afferent nerve
sensory nerve
-transmits impulses to the nervous system
efferent nerve
motor nerve
-transmits impulses from brain or spinal cord to muscle
- destruction of motor neurons by disease
- interruption of reflex arc responsible for muscle tone
- muscle deprived of innervation
- low muscle tone
- peripheral nerve destruction
Flaccid paralysis
- reflex arc not disturbed
- injury to cortical neurons stops voluntary control
- muscle retains innervation
- increased muscle tone
spastic paralysis
anencephaly
- failure of normal development of brain and cranial cavity
- multifactorial inheritance
-alpha-fetoprotein leaks from fetal blood into amniotic fluid through open neural tube defect; high levels found in amniotic fluid
spina bifida
voluntary motor activity is controlled by the _____________ system and the ______________ system.
pyramidal system and extrapyramidal system
-controls voluntary motor functions
pyramidal system
-regulates muscle groups concerned primarily with balance, posture, and coordination
extrapyramidal system
- from congenital obstruction of aqueduct or absence of openings in roof of 4th ventricle
- head enlarges as ventricles dilate because cranial structures have not fused
congenital hydrocephalus
protein produced by fetal liver early in gestation. sometimes produced by tumor cells. level is elevated in amniotic fluid when fetus has neural tube defect.
alpha fetoprotein (AFP)
- obstruction of cerebral spinal fluid (CSF) by tumor or adhesions blocking opening in 4th ventricle
- ventricles dilate but head does not enlarge because cranial structures are fused
acquired hydrocephalus
treatment of hydrocephalus
-inserting a plastic tube into a dilated ventricle and rerouting (shunting) the fluid into another part of the body where it can be absorbed.
any injury to brain tissue from disturbance of blood supply to brain
stroke, or cardiovascular accident
most common; thrombosis of cerebral artery narrowed by arteriosclerosis
cerebral thrombosis
occurs less frequently; blockage of cerebral artery by fragment of blood clot from an arteriosclerotic plaque or from heart
cerebral embolus
most serious type of stroke; usually from rupture of a cerebral artery in person with hypertension
cerebral hemorrhage
ischemic infarct
no blood leaks into brain
hemorrhagic infarct
blood leaks into damaged brain tissue
- sclerosis of major artery from aorta that supplies brain
- common affected site: carotid artery in neck; arteriosclerotic plaque may narrow lumen and reduce cerebral blood flow
arteriosclerosis of extracranial arteries
cerebral angiogram
- dye is injected into the carotid and vertebral arteries that arise from the arch of the aorta to the brain
- the course of the dye is followed by serial x ray studies
temporary cerebral dysfunction as a result of transient obstruction of a cerebral vessel by a bit of atheromatous debris or blood clot usually embolized from an arteriosclerotic plaque in the carotid artery
transient ischemic attack (TIA)
About 1/# of patients with TIAs eventually suffer a major stroke.
1/3.