Nervous System Flashcards
Is the optic nerve similar to the rest of the cranial nerves?
No, it is essentially an ‘extension’ of the brain and moves anteriorly
Name the types of glial cells.
Astrocytes Schwann Cells Oligodendrocytes Ependymal Cells Microglia
What are components of a neuron?
Dendrites (signal entry), nucleus, cell body, axon, possible myelin sheath around it, axon terminus
What are the categories of neurons in terms of action potential propagation?
Unipolar (sensory neuron)
Bipolar (interneuron)
Multipolar (Motor neuron, interneuron, pyramidal cells)
What are Astrocytes important in?
Structural support and forming the blood-brain barrier
Star shaped
What are Schwann Cells important for and where are they located?
Apart of PNS
Enable fast signal transduction due to myelination
Involved in Multiple Sclerosis
What are Oligodendrocytes important for and where are they located?
In CNS
Enable fast signal transduction due to myelination
Involved in Guillain-Barre Syndrome
What are Ependymal Cells important for and where are they located?
Found in ventricle of brain
Help with circulation and production of CFS
What are microglia important for?
Immune protection- innate immunity, similar to macrophages
What is a glioma?
A type of brain tumour.
Glioblastoma is an example of a very aggressive form of cancer (grade 4 glioma) within the brain
What is grey matter, where is it found in brain/spinal cord, and what does it contain?
Has more cell bodies, dendrites, axon termini, unmyelinated
Found internally within spinal cord, and on periphery of brain
Contain glial cells and some blood vessels
What is white matter, where is it found in brain/spinal cord, and what does it contain?
More matter that contains myelinated axons
Found internally in brain, and on periphery of spinal cord.
Contain glial cells and some blood vessels
How many neurons and synapses are in the brain?
86 billion
100-500 trillion synapses
What is the weight of the brain?
1.5kg
How does folding help the brain?
Helps get more material into a small space
What are the sulci and gyri
Divide the brain into specific lobes
Sulcus are grooves
Gyri are ridges
What are the different lobes of the brain?
Frontal Parietal Temporal Occipital Deep limbic lobe
What are the different areas of the brain from developmental origin?
Cerebrum (telencephalon) Diencephalon (gives rise to hypo/thalamus) Midbrain (mesencephalon) Pons (metencephalon) Cerebellum (metencephalon) Medulla Oblongata (myelencephalon)
What does the brainstem do?
Consciousness, breathing, heart rate
How is the brainstem divided?
Midbrain, Pons, Medulla
How is the midbrain related to parkinsons?
It contains the Substantia Nigra, which is impacted in Parkinson’s disease
This area degenerates and results in problems with motor function
What is the function of the spinothalamic tract and medial lemniscus, and where are they found?
Within the midbrain of the brainstem
Aid in conduction of impulses between the brain and body
What is the cerebral aqueduct?
Found in the midbrain, dorsal to the pons of the brainstem
A part of the ventricular system connecting the 3rd and 4th ventricles
Where do most cranial nerves emerge from?
Brainstem
What are important characteristics of the brainstem?
Many nuclei for reflexes
Many reflex centres (i.e. vomiting reflex in medulla)
Are there any nervous system functions specific to the brainstem?
Autonomic nervous system controlled in the medulla
What is the pre-frontal cortex responsible for?
High level thinking, problem solving, behaviour, mood,
What separates the frontal and parietal cortex?
The central sulcus
What is found anterior to the central sulcaus?
Primary motor cortex
Motor control
What is found immediately posterior to the central sulcus?
Primary somatosensory cortex
Sense and touch
Where is the visual cortex?
Back occipital lobe
Where is Broca’s area found, and why is it important?
Lateral, bottom edges of the frontal lobe, just anterior to the primary motor cortex, and posterior to the pre-frontal cortex, within the left hemisphere
This impacts the production of speech, however understanding of speech typically isn’t impacted.
Most common type of aphasia is Broca’s
Where is Wernicke’s area found, and why is it important?
Found on the posterior aspect of the temporal lobe of the left hemisphere.
Used in language (more superior) and speech.
This is the actual meaning of speech, so if damaged, you can still speak but it may not make sense, and you may not understand speech.
Comprehension of speech.
How do we determine what part of the brain is responsible for a given function?
Look at functional effects of damage to the specific area
Use PET, MRI scans to look at what areas are active when doing specific things.
What are the deep structures within the brain?
Limbic System Basal Ganglia White matter tracts Hypothalamus Amygdala Thalamus
What forms the limbic system?
Includes the hippocampus (lots of learning and memory) and amygdala
What does the Basal Ganglia do?
Movement, reward
What do white matter tracts do?
Communication tracts between areas of the brain
i.e. the two hemisphere communicate using the corpus collosum
What does the Thalamus do?
Sensory gateway
Relay centre
What does the Hypothalamus do?
Regulates body function, homeostasis
What does the amygdala do?
Emotions
What does the hippocampus do?
Memory
Why do we have two hemispheres?
Although mostly the same on both sides, specific areas have different functions
Language and production of speech is typically on the left
Right is typically controlling left body, and vice versus
What are the divisions of the spinal cord?
Cervical, thoracic, lumbar and sacrum
Where to spinal nerves exit from the CNS?
Between the vertebra
What type of control is passed through the spinal nerves?
autonomic, sensory and motor control
What are important actions controlled by the cervical spinal cord?
Breathing
What are important actions controlled by the thoracic spinal cord?
Sympathetic tone- cardiovascular function,
What are important actions controlled by the lumbar and part of the sacral spinal cord?
Knee and foot movement
Where does motor output travel out of the spinal cord?
Spinal nerve at ventral side
Where does sensory input travel into the spinal cord?
Spinal nerve at dorsal side
Why does the ratio of white: grey matter vary throughout the spinal cord? Give an example
The amount of input and output varies at different levels
In lower regions (i.e. lumbar), there is less white matter as there are few axons, whereas the cervical region has a lot of white matter as everything passes through.
Where does the spinal cord end?
Cauda Medullaris
The cord ends around L1 and then fans out below (cauda equina)
What are spinal cord tracts?
Bundles of nerve fibres that run up and down the spinal cord, taking information either to the brain, or down to the body
Contain autonomic, sensory and motor nerve fibres
What are some functions of the spinal tracts?
Sensory pathway of pain and temperature
Descending for voluntary motor control
What is decussate of spinal tracts?
When the tract crosses over to the opposite side to pass up the spinal cord.
Can be ipsilateral (travelling on the same side) or contralateral (crossing over and travelling up)
How can partial spinal cord injuries manifest clinically?
If you injure one side of the spinal cord (i.e. due to tumour growth), it may impact the opposite side due to contralateral decussating of the tract below the given injury/lesion.
If injury occurs, function is typically lost below the site of injury
What are the meninges?
3 membranes that surround the spinal cord and brain
dura, arachnoid, and pia
Describe the Dura layer with reference to location
Dura is tough, fibrous, and most peripheral
Has 2 layers (outer periosteal layer, inner meningeal layer) that form the vinous sinuses, within the brain.
Along brainstem, only contains 1 layer
Describe the Arachnoid layer with reference to location
Arachnoid is the middle, avascular layer that does NOT enter the grooves of the brain
Contains arachnoid granules which aid in clearance of CSF
Describe the Pia layer with reference to location
Pia is most internal and the thinnest layer.
It adheres to the brain’s surface, and enters all grooves/fissures formed by the brain
What is the role of the venous sinuses?
Complex branching sinus between layers of dura, collecting oxygen depleted blood and draining the CSF Arachnoid granules (arachnoid villi) project into the sinus and deliver CSF from brain to venous system
What is the subdural space and when does it fill?
Theoretical space between the arachnoid and dura layers of the meninges.
Generally only filled when bridging veins that connect to the venous sinuses is ruptured.
What is the epidural space and when is it filled?
Between skull and dura is epidural space, it shouldn’t be present in healthy person.
Haematoma rupture can cause it to fill with blood
What is the subarachnoid space?
Where cerebrospinal fluid loads
Cerebral arteries and veins found here
Connective structure, arachnoid trabeculae, that joins arachnoid and pia layer