Brain and the Nervous System Flashcards
The brain and spinal cord are protected by the _______ and ____
Meninges and Bone
What are the 3 meningeal layers?
Dura Mater, Arachnoid Mater, Pia Mater
Describe the Dura Mater?
A strong outer fibrous membrane that adheres to the skull and vertebrae
Describe the Arachnoid Mater?
The middle interposed membrane between the Dura and Pia
Describe the Pia Mater?
Inner thin membrane that adheres to the surface of the brain and spinal cord
Between the Pia and Arachnoid Maters is called the _____________
Sub-Arachnoid space
What is found in the sub-arachnoid space?
CSF - a watery fluid that nourishes and cushions the nervous system
The PNS is made up of all the nerves _______ the CNS
Outside
A group of nerve cell bodies in the PNS is called a _______
Ganglion
How many cranial nerves are there?
12 pairs
How many spinal nerves are there?
31 pairs
Nerves can be divided into the _______ or sensory pathways and the _______ or motor pathways
Afferent - Sensory
Efferent - Motor
How many cervical nerves are there?
8 pairs
How many thoracic nerves are there?
12 pairs
How many lumbar nerves are there?
5 pairs
How many sacral nerves are there?
5 pairs
How many coccygeal nerves are there?
1 pair
The brain is divided into 3 parts, what are they?
Cerebrum
Cerebellum
Brain Stem
The brain requires a rich blood and oxygen supply, how is this need met?
There are a large amount of blood vessels in the space between the cerebrum and the skull in the Circle of Willis
Shallow grooves in the cerebrum are called ______
Sulci
The raised regions surrounded by grooves are called _____
Gyri
Deep grooves in the cerebrum are called _______
Fissures
What are ventricles?
A series of spaces and tunnels within the center of the brain that secrete and house CSF which suspends the brain in the skull
The largest part of the brain is the ______ it is made of ____________ which are connected by the ____________
Cerebrum
2 Hemispheres
Corpus callosum
Nerve tracts ______ at the brain stem which results in ________________________
Cross over
Left side controls the right, Right side controls the left
The cerebral cortex is a thin layer, about _____ thick. It provides _______ and _______ for higher cognitive function. It houses _________ neurons
1.5-4mm thick
Connections and pathways
25 billion
The cerebellum is connected to the ________ and is responsible for ________________ and _______
Brain Stem
Coordination of movement and balance
The brain stem consists of the _______, ___ and _____________. It is responsible for ____________ and _______
Midbrain, Pons, Meddulla Oblongata
Basic Function and reflexes
What are the 2 main functions of the spinal cord?
- Conduct nerve impulses to and from the brain
- Process sensory information in a limited manner and perform reflex actions
Describe the structure of the spinal cord.
- Outer region is white matter(myelinated)
- The inner H-shaped region is grey matter (un-myelinated)
- A central canal is present which is continuous with the 4th ventricle in the brain
What are neuroglial cells?
Supportive cells found in the nervous system
What neuroglial cells are found in the CNS?
Astrocytes
Oligodendrocytes
Microglia
Ependymal cells
What neuroglial cells are found in the PNS?
Schwann cells
Satellite cells
Briefly describe the structure of a neuron
1 Cell body
Multiple processes on one end that receive impulses are called dendrites
A single process on the other end conducts impulses and is called an axon
Axons end is multiple processes called telodendria
Most axons are covered in a fatty sheath called _____. In the CNS axons are myelinated by _________, in the PNS axons are myelinated by ________.
Myelin
Oligodendrocytes
Schwann cells
A nerve is composed of the ____________________ joint together by a ______________
Processes of many neurons
Connective tissue sheath
Describe Astrocytes:
- Large star shaped cells
- Most abundant glial cell
- Has numerous processes that attach neurons to capillaries
- The provide nourishment for the neurons
Describe Oligodendrocytes:
- Smaller than Astrocytes with fewer processes
- Myelinate in CNS
Describe Microglia:
- Smallest glial cells
- Resident macrophages
Describe Ependymal cells:
- Line the ventricles and brain
- Involved in the production of CSF
There are more than __ types of neurotransmitters. What are some common examples?
50 types Acetylcholine Adrenaline and Noradrenaline Glutamate Serotonin Dopamine
Neurotransmitters are synthesised by _______ and stored in small compartments called ______________
Neurons
Synaptic vesicles
When an impulse reaches the axon terminals ____ rushes into the cell and triggers ___________________________
Ca 2+
Exocytosis and release of neurotransmitters
What proteins regulate synaptic vesicle exocytosis?
70 Small GTP binding Rab proteins regulate vesicle transport
SNARE proteins regulate membrane fusion
Describe the embryological development of the Nervous System
- Thickening of ectoderm becomes known as the neural plate, it appears after the 2nd week
- Lateral regions of the neural plate begin to grow upwards forming neural folds
- Folds fuse forming a neural tube by the 4th week
Pathologies involving the neural tube occur if the tube has not _____________
Closed properly
What pathology occurs when the Cephalic region does not close properly?
Anencephaly
What pathology occurs when the Caudal region does not close properly?
Spina Bifida
Neural tube defects are the _____ common congenital malformation of the CNS. It follows a _____________ inheritance pattern and is related to deficiencies in __________
Most common
Multi-factorial inheritance
Folic Acid
Anecephaly is most common in ______ infants and _____ compatible with life
Female
Not compatible
In anencephaly, the brain initially protrudes through _________________ and is gradually _________ by ____________ and ________________. This results in the brain becoming a _____________ of ______ and _______ tissue
A defect in the cranial vault
Destroyed
Mechanical injury and vascular disruption
Vascularised mass of brain and connective tissue
What are the clinical manifestation of anecephaly?
- Infant has no brain
- Lacks soft tissue of the scalp and bone for skull vertex
- Malformation of the base of the brain cavity causing bulging eyes
- Short trunk, broad shoulders and absence of neck
- May extend to the upper region of the spinal cord
What are the 3 types of spina bifida?
- Occult spina bifida = failure of fusion in the lower lumbar regions, prevents few clinical features
- Meningocele = protrusion of the meninges
- Meningomyelocele = parts of the spinal cord and meninges protrude
In severe cases of meningomyelocele how does the spinal cord present?
Spinal cord presents as a flattened mass of nerve tissue that is continuous with adjacent skin and covered by a fine meninge
How do we treat Occult spinabifida?
Usually asymptomatic and requires no treatment
How do we treat Meningoceles?
Surgery that excises the sac and closes the spinal dura
How do we treat Large Meningoceles?
- Surgery like a small meningocele
- Surgey can result in lower motor function damage
- Often requires lifelong care
How do we screen for NTDs (Neural Tube Defects)?
- Amniocentesis aka Amniotic Fluid Test (AFT)
- Test for levels of α-foetoprotein (AFP)
- High levels of AFP are ussually diagnostic
- Can be detected on ultrasound by 20 weeks
What is Hydrocephalus?
The dilation of the cerebral ventricles that is ussually caused by an obstruction in CSF circulation
Causes compression atrophy of the brain
Explain how CSF is produced and circulated:
- 600-700mml produced every day in the lateral ventricles by the Choroid plexus
- Enters the 3rd ventricle then the 4th via the cerebral aqueduct where it exits into the SAS
- CSF is absorbed into the venous circulation in the sinuses of the dura
What are the 2 types of Hydrocephalus and what causes them?
Congenital - caused by ventircle malformation, causes enlargement of head
Aqquired - caused by blockage of the 4th ventricle ussualy due to fibrous adhesion or tumours
How do we treat Hydrocephalus?
- Insertion of a shunt that diverts flow away from the blockage
- Catheter end is inserted usually into a ventricle and other end usually goes to the peritoneal/abdominal cavity for drainage and reabsorption
What are shunts?
Sturdy and flexible plastic tube that consists of a shunt, catheter and valve
Voluntary muscle action is controlled by 2 systems; the _________ system controls voluntary motor function, the _________ system controls balance, posture and coordination.
Pyramidal
Extrapyramidal
The axons of the Pyramidal system travel through fiber tracts called _______ or __________ tracts
Pyramidal
Corticospinal tracts
The neurons in Extrapyramidal system have connections with the _______ and ________
Cerebellum
Basal Ganglia
Both pyramidal and extrapyramidal systems are under _______ control and produce ____________________________.
Cortical control
Smooth, integrated function of muscle