Neurology Pathophysiology Flashcards
Peripheral Nervous system can be broke down into which divisions?
CNS is made up of what?
PNS can be broken down into the Sensory(afferent) division and the Motor (Efferent) division.
The motor division is then divided into the Autonomic Nervous System and the Somatic Nervous system.
Autonomic NS is further divided into the sympathetic and parasympathetic divisions.
CNS is made up of the brain and spinal cord. Encased in bone.
Describe embryonic development of the brain and spinal cord.
- Neural plate forms from surface of ectoderm.
- neural plate invaginates forming the neural groove flanked by the neural folds.
- Neural fold cells migrate to form the neural crest, which forms much of the PNS.
- leading to neural tube?
What is responsible for the development of the CNS? nerves of the PNS?
ectoderm
neural crest responsible for nerve of the PNS
WHat are the nervous system cell types?
Astorcytes: connective tissue cells
Microglia: act as mfs
Ependymal cells: line cavities, cuboidal or columnar cells, they absorb fluid across spinal cord.
Oligodendrocytes: surround nerve fibers and act in the brain as the schwann cells do in the periphery. Form myelin sheath.
Nerve Conduction
- describe charge and solutes inside and outside of axon.
- describe an AP
- are AP summative?
- describe potential conduction velocity
- where do APs occur in myelinated and unmyelinated neurons?
- Inside: K+, negatively charged
- Outside: positively charged, Na+
AP:
- all or none events
- influx of Na+ into cell leads to depolarization, once this peaks K+ channels open and K+ leaves, repolarizing the cell.
No, AP are not summative.
Conduction velocity: depends upon fiber diameter and whether or not the axon is myelinated or not. Larger myelinated fibers conduct faster than smaller unmyelinated fibers.
APs occur at the nodes of Ranvier in myelinated axons, and occur subquentially one right after another the entire length of the axon in unmyelinated axons.
What are the 5 lobes of the brain and function of each?
Frontal: “secretary”, primary motor cortex, brocas area(speaking and writing), solving complex multitask problems, personality, judgement.
Temporal: understanding language (wernickes; comprehension and speech), memory, hearing, sequencing and organization.
Occipital: interprets color light and movement
Parietal: sense of touch, pain, temp (sensory cortex), Spacial and visual perception
Insula; deep within the lateral sulcus, conciousness, emotion, self-awareness, interpersonal experience.
Edema in the CNS:
- how might this occur?
- why is this a special problem in the brain and spinal cord?
- types
How: increase in tissue mass that results from the excess movement of body fluid from the vascular compartment or its abnormal retention in the tissue.
Special issue:
- enclosed space
- lack of lymphatics
- lack of anastomoses in venous drainage
Types:
- vasogenic
- cytotoxic
What is Vasogenic Edema?
Cytotoxic edema?
Vasogenic: occurs when the blood brain barrier is upset either d/t inflammation from infection, toxic agents that damage capillary endothelium, abnormal capillaries associated with malignant neoplasm….these all cause leakage of proteins and fluid into the interstitium leading to swelling!!!!
Cytotoxic: intracellular phenomenon, cells themselves are damaged d/t
-hypoxia; cardiac arrest, near drowning, strangulation, focal edema d/t blockage of an end artery.
-Toxic substances that impair Na/K+ pump, impair production of ATP
these lead to intracellular edema.
Treatment of:
Cytotoxic edema
Vasogenic edema
Cytotoxicity: give IV bolus of hypertonic solution such as mannitol to draw water into the vasculature and out of the brain.
* DO NOT DO THIS IN VASOGENIC SHOCK!!! it would further draw MORE fluid into the interstital space and INCREASE SWELLING!
Increased Intracranial pressure
- causes
- normal pressure
Causes: tumor growth, edema, excess cerebrospinal fluid blockage, hemorrhage
Normal: 5-15mmHg
Clinical Hallmarks of Increased Intracranial Pressure, can you do LP on these patients?
- HA
- Vomiting
- Papilledema
No, cannot do LP unless you want to herniate their brain and kill them.
When intracranial pressure is high, cerebral blood volume is altered in 4 stages…what are these?
- vasoconstriction and external compression of venous system; few sx
- increased intracranial pressure causes a decrease of O2 to neural tissue causing systemic vasoconstriction 3.; episodes of confusion, restlessness, drowsiness, and slight pupillary and breathing changes (hypoventillation)
- when ICP begins to =arterial pressure there is lack of compensation- beginning decompensation; hypoxia and hypercapneia leading to cytotxic edema, decreased level of arousal, widened pulse pressure, cheynes-Stokes respirations (abnormal breathing pattern characterized by progressively deeper and sometimes faster breathing, followed by apnea), bradycardia, pupils small and sluggish, surgical or medical intervention needed
- All compensatory mechanisms have been exhausted, dramatic rise in ICP in a short time, autoregulation is lost causing vasodilation and further increasing intracranial volume, decreased cerebral perfusion leading to severe hypoxia and acidosis, brain contents herniate from area of high pressure to lower pressure, small hemorrhages develop, ipsilateral pupil dilation and fixation, progressing to bilateral fixed and dilated pupils
What happens when mean systolic arterial pressure equals ICP?
cerebral blood flow ceases
Which cerebral artery often becomes obstructed and causes strokes?
-lenticulostriate arteries which branch off of the middle cerebral artery stem.
Which arteries supply the medial and lateral parts of the cerebrum?
Medial: anterior cerebral artery
Lateral: Middle cerebral artery
