Chapter 9 The Nervous System Flashcards
At what level does the spinal cord end?
The spinal cord ends at L1-L2
What is anencephaly?
A severe malformation in which the cranial vault is absent and the cerebral hemispheres are either missing or markedly reduced in size
What is microcephaly?
Means the infant is born with an exceedingly small head. This occurs when there is failure of the cerebrum to develop properly
What is hydrocephaly?
It literally means “water brain” and occurs within the ventricles
What are the different way hydrocephaly may occur?
Congenitally or may arise from a variety of causes at any time after birth
What happens in hydrocephalic individuals?
The ventricles enlarge as a result of a blockage in the flow of CSF at some level
What is the most common type of congenital hydrocephalus?
Stenosis of the aqueduct of Sylvius, which causes enlargement of the lateral and third ventricles with a normal sized fourth ventricle
What happens if the obstruction occurs at the level of the foramen of Monro with hydrocephalus?
The lateral ventricles enlarge, leaving the third and fourth ventricles at normal size
What are transient ischemic attacks?
Mini strokes - they are a temporary interruption of circulation usually caused by arteriosclerotic plaque
What are TIAs characterized by?
fleeing attacks of faintness, localized paralysis, and aphasia
TIAs are a warning of what?
A warning sign that a major stroke may be imminent
What is the most common head injury?
A concussion
When does a concussion occur?
When there has been violent blow or jar to the head
What happens when there has been a violent blow or jar to the head with a concussion?
The brain strikes the opposite side of the cranium, resulting in momentary loss of consciousness
What symptoms may be associated with a concussion?
Transient amnesia, vertigo, nausea, weak pulse, and slow respiration
Where do most aneurysms occur?
The circle of Willis, in particular the anterior communicating artery and the major subdivisions of the middle cerebral artery
What is encephalitis?
Inflammation of the brain
What is encephalitis almost always caused by?
A virus
What are many of the viruses that cause encephalitis spread by?
Mosquitoes
What are the symptoms of encephalitis?
Irritability, drowsiness, and headache
What is another cause of encephalitis?
Herpes simplex 1
Although encephalitis is rare, what can happen?
It can invade the brain in a susceptible person and result in severe destruction of large areas of the temporal or frontal lobes of the brain
What are contra coup lesions?
Contusions that occur on the opposite side of the head
What is a coup lesion?
When the bruise occurs on the same side of the brain as the trauma
What is a contusion?
bruises on the surface of the brain and are a result of the brain shifting inside the skull during acceleration and rapid deceleration such as “whiplash” reaction received from a MVA
What do contusions result in?
Hemorrhages from small blood vessels, which cause further vessel occlusion and edema
What must be closely watched for with contusions?
intracranial pressure
What is the nervous system divided into?
The central, peripheral, and autonomic systems
What does the central nervous system include?
The brain and the spinal cord
What does the peripheral nervous system include?
The cranial and spinal nerves
What is the autonomic nervous system divided into?
The sympathetic and parasympathetic systems
What is the most highly organized system of the body?
The central nervous system
What is the central nervous system also referred to as?
The cerebrospinal system
What accounts for about 98% of the entire central nervous system?
The brain
About how many neurons are in the brian?
11 billion
What is the function of the neurons?
They transmit a message from one cell to the next through a series of axons and dendrites
What are the divisions of the brain?
The cerebrum and diencephalon; the brain stem and the cerebellum
What does the term brain stem refer to?
The midbrain, pons and medulla
How many hemispheres is the cerebrum divided into?
Two hemispheres and are held together by the corpus calosum
How many lobes are the two hemispheres of the cerebrum divided into?
Four lobes each named after the cranial bone to which it is related; frontal, occipital, parietal, and temporal
What is the entire cerebrum covered with?
The cerebral cortex where the highest level of neural processing takes place including language, memory and cognitive functions
What is located below the cerebrum?
The diencephalon which is the part of the brain between the cerebellum and the cerebrum
What does the diencephalon contain?
The thalamus and the hypothalamus
What is the thalamus?
An importnat relay station, distributing sensory information from the periphery to different regions of the cortex
What is underneath the thalamus?
The hypothalamus which contains the third ventricle
What does the brian stem consists of?
The midbrain, pons, medulla and the nuclei of the 12 cranial nerves
What are the functions of the brain stem?
Many important reflex centers which control vital functions such as heartbeat and respiration. It is also important in regulating levels of consciousness as injury to the brain stem can result in prolonged loss of consciousness or death
What is the most posterior part of the brain?
The medulla oblongata
Where is the fourth ventricle formed?
In the medulla oblongata. The central canal of the spinal cord enlarges which forms the fourth ventricle
What secretes some of the cerebrospinal fluid and contains openings that connect the cavity with the subarachnoid space with the lateral ventricles in the cerebral hemispheres?
The medulla oblongata (fourth ventricle)
What connects the cerebellum, the cerebrum and the medulla oblongata?
The pons
What is the second largest division of the brain?
The cerebellum, which is latin for “little brain”