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
What is meningitis?
Inflammation of the meninges, especially the pia matter, arachnoid, and subarachnoid space
Can be very serious as can cause brain damage via cerebral oedema leading to raised intracranial pressure that may result in herniation (movement) of the brain tissue, leading to brain damage.
What is a lumbar puncture?
Taking sample of CFS
Insert needle between L4/5 vertebra
What is cerebral spinal fluid?
Fluid within the CNS
Contains few cells and less protein content than blood
Electrolyte levels differ from plasma and are optimized to promote function of nervous tissue
What are ventricles?
Spaces within the brain and meninges that are filled with CSF
They are connected to each other to allow flow
What is the role of CSF?
Cushions the brain against force
Prevents the brain from crushing itself with weight
Chemically provides electrolytes that are suitable for brain function
Provides nutrients and removes waste products, exchanging this with blood.
Where is CSF produced?
Choroid plexus in lateral and 4th ventricles
How is CSF removed?
Resorbed into the venous system by arachnoid granulations
How can obstruction of CSF flow impair a person?
Causes hydrocephalus
In children, it can alter the shape of the head.
In adults, may cause headache, double vision, poor balance, urinary incontinence, personality changes, or mental impairment
What is the blood brain barrier?
Regulates movement of substances between the CNS and the rest of the body
What are the structural features of the BBB?
- Capillaries have continues thick basement membrane and endothelial cells joined by tight junctions that restrict movement in and out of CNS
Astrocytes contribute as their feet cover the small blood vessels helping to block movement - Ependymal Cells (Ependymocytes) line the ventricles and spinal canal and are joined by tight junctions
What is the area postrema?
Area in the medulla of the brainstem that contributes to toxin detection and vomiting reflex
Permeability is slightly higher and thus allows for small amounts of toxins through the BBB to be “sensed”
What is the BBB permeable to?
Small lipophilic molecules, gases, water
What substances are actively transported across the BBB?
Glucose and amino acids
What is the autonomic nervous system?
Uncontrolled, automated nervous system
What specific body functions/responses are controlled by autonomic nervous system?
Digestion, fight or flight, micturition, sex and reproduction, heart rate
What are similarities between the autonomic and somatic nervous systems?
Both synapse via ganglions
Both have sensory and effector effects
Both use acetyl choline in ganglion transmission
What are the major differences between the autonomic and somatic nervous systems?
Location in body
Location of ganglion
Post-ganglionic neurotransmitters (epi/norepi)
Function
What is the origin of the sympathetic nervous system?
Lateral horns of T1-L2/3
Thoracolumbar
Exception: pre-ganglionic stimulation using acetylcholine on adrenal medulla
Where are the ganglion of the SNS?
Within/beside the CNS, typically in the chain ganglion
What neurotransmitters are involved in the SNS?
Pre-ganglionic synapse- Acetylcholine (cholinergic)
Post-ganglion neurons- Noradrenaline called adrenergic neurons (except for sweat glands and deep muscles which use acetylcholine)
What are the neurotransmitters involved in the PNS?
Pre-ganglionic synapse- Acetylcholine
Post-ganglionic synapses- Acetylcholine
Both are cholinergic
What are the branches of the autonomic nervous system?
Sympathetic (fight or flight- stress response)
Parasympathetic (rest and digest)
What physiological responses are associated with a sympathetic nervous response?
Capillary dilation (see more light)
Decongested nose and dry mouth (increases oxygen intake)
Increased heart rate (pushing more oxygenated blood to body- chronopy/isotropy)
Vasodilation (aid in blood movement into tissues)
Constipation (reduced blood supply, relaxation of the smooth muscle, to prevent need for toilet)
Urinary retention (need fluid retention)
Renal blood flow decreases (this increasing renin which will convert angiotensinogen to angiotensin 1 increasing vasoconstriction to kidneys)
Direct synapsis onto the adrenal medulla causing secretion of corticosteroid and adrenal release
Reduce excessive heat via sweating
What are the receptors involved in the somatic nervous system?
Acetylcholine acts on nicotinic receptors on skeletal muscle
Where do parasympathetic nerves leave the spinal cord?
Cranial nerves 3, 7, 9, 10, and from S2-S4
Craniosacral Outflow
How do pre/post-ganglion nerves differ in terms of length in the PNS and SNS?
Pre-ganglionic nerves are short in the SNS, but long in PNS
Post-ganglionic nerves are long in SNS but short in PNS
Where are pre-ganglionic ganglia of the SNS found?
Chain Ganglia in CNS
(Pre-ganglionic nerve moves from intermediate lateral grey horn to ventral root into ventral ramus, through the white rami communicans and to the chain ganglion where the synapse is located)
Where do the post-ganglionic SNS nerves move following the synapse?
Moves from the chain ganglion, out the grey rami communicans and out the ventral ramus then to different tissues.
Instead of synapsing at immediate ganglion, the pre-ganglion can also travel along to other ganglions within the chain
How are sweat glands an exception in the SNS?
The post-ganglionic synapse uses muscarinic receptors and acetylcholine neurotransmitters
What are the receptors found within the sympathetic nervous system?
Alpha 1/2 and beta 1/2, nicotinic and 1 exception (sweat glands) that use muscarinic
What are the roles of the alpha receptors in the Symp NS.?
- Arteriole vasoconstriction in periphery
2. Coronary and venous vasoconstriction
What are the roles of the beta receptors in the Symp NS.?
Beating and breathing
Beta 1- heart (^HR, ^ Cardiac Output)
Beta 2- Bronchodilation (uterus/GI/secretions reduce/relaxation, peripheral vasodilation (skeletal muscle blood vessels), pupil dilation (via relaxing of lens)
How does the beta 1 receptor influence physiological responses in the body?
Increases heart rate and contractility
How does the beta 2 receptor influence physiological responses in the body?
Causes smooth muscle relaxation in areas that are advantageous (i.e. running away needs skeletal muscle)
Bronchodilation, dilates eye, relax gut, uterus,
What are some alpha 1 agonist?
Metaraminol- We can give this to cause arteriole or vasoconstriction. Used for treatment of acute hypotension
Pseudoephedrine- baby adrenaline, constricts blood vessels, particularly in the nose, tend to get a bit hypertensive as well.
Phenylephrine- dilates pupils
Whats an alpha 1b antagonist?
Doxazosin- antihypertensive
Whats an alpha 1a antagonist?
Tamsulosin- Prostatic in bladder relaxation and renal stones, causes constipation
What is an example of alpha 2 agonist?
Yohimbine- Cause venous vasoconstriction (mild erectile dysfunction drugs)
Reversal of sedation in veterinary practice
What is an example of a B1 agonist?
mimicking
Isoprenaline- heart block, will try to stimulate the beta 1 receptors to increase heart rate
What is an example of a B2 agonist?
Salbutamol- inhaled into lungs causing smooth muscle relaxation and bronchi dilation
Can be used intravenously to tell uterus to relax in premature labour.
What is an example of a B1 antagonist?
Blocking the receptor
Atenolol- causes the opposite effect, lowers BP/HR
Used in tachycardia and secondary MI prevention (too much adrenaline stimulation increases rates of death often due to arrhythmias)
Bisoprolol- Prevent heart failure and works similarly to atenolol
Beta Blockers- used to reduce cardiac output and blood pressure
What is an example of a B3 antagonist?
Propranolol (non-selective beta-blocker)- Used for treating migraine, panic attacks, and anxiety
Where are B3 receptors typically found?
In the gallbladder, bladder, and adipose tissue.
Thought to cause relaxation of bladder (preventing urination)
Where are B2 antagonists used?
Used in labs to increase peripheral BP to assess agonists
Butaxamine
What are physiological responses caused by the parasympathetic system?
Pupil constriction, salivary release, enhanced smell, slowed HR, bronchoconstriction, micturition, ejaculation, defecation
What is the origin of the paraNS?
Craniosacral
Cranial Nerves 3 (ocular), 7 (taste/salivation), 9 (glossopharyngeal, increases salivation), 10 (vagus)
Sacral - 2, 3, 4
Where are the ganglion of the ParaNS?
Near site of action
What is neurotransmitter used in the ParaNS?
Acetylcholine in both pre and post ganglionic neurons
What is the vagus nerve of the ParaNS responsible for innervating?
Lungs, Heart, Liver, Kidneys, Stomach, bowel, transverse colon
What are the types of ganglion used in the ParaNS?
Cervical Ganglion (in neck), Thoracic (behind heart), Celiac (Gut)
What are the receptors used in the ParaSN?
Muscarinic and Nicotinic
What are the muscarinic receptors in the periphery?
M1- Common in secretory glands
M2- Cholinergic receptors in heart which slows heart reducing chronotropy and inotropy
M3- Smooth muscle (Gut, bladder, blood vessels, eye) and secretory glands
M4
What antagonist drugs are used for the M2 receptors in the ParaNS?
Atropine- Acts by blocking effect of acetylcholine on the heart, allowing heart to speed up Hyoscine Glycopyrrolate Ipratropium Oxybutynin Benztropine
What are some M3 antagonists used in the ParaSN?
Tiotropium/ ipratropium- used on lungs (COPD)
Oxybutynin- Bladder (incontinence)
Mebervine- Gut
What muscarinic receptors are found in the brain?
M2/4/5 most commonly, but all are there
What are N1 antagonists?
Muscle blockers
Binds the neuromuscular junction irreversibly, so ACh cant penetrate this and we cant stimulate muscles.
i.e. Bungarotoxin from snakes
What is an example of a N2 receptor antagonist?
Curare- binds neuromuscular junction reversibly. Non-depolarizing block (plant- causes paralysis)
Vecuronium- can reverse using competitive inhibition (surgery muscle relaxant)
What is an agonist of M3 receptors?
Pilocarpine- Eye (glaucoma) causes vasoconstriction to allow the pupil to relax, therefore reducing pressure (which can lead to glaucoma)
What happens when the brainstem is damaged and function is lost?
Paralysis and unconsciousness
Apnoae
Loss of cranial nerve function (almost all)
What is brain coning?
Injury to head causes pressure to increase and brain to swell
Swelling causes brain to push down through foramen magnum, causing Cerebellar Tonsillar Herniation
Ischemia of brainstem
What is the first sign of brain coning?
Dilated pupil
What are the vessels supplying the brain?
Basilar artery (aorta -> Right/Left Subclavian Arteries -> R/L vertebral arteries -> conjoin to form Basilar Artery ) Carotid arteries (branching off of aorta)
How do you test Brain Stem Death?
Irreversible cortical death
Exclusion Criteria met
Unconscious, apnoeic
Normal temperature, blood glucose, electrolytes, endocrine function, and no drugs
2 doctors of consulting and senior registrar level
How do you test cranial nerve function?
Cranial Nerve 2- Light on pupil
CN 5-Corneal reflex, cotton ball on eye should cause blinking
CN 3, 4, 6, 8- Check eardrum isn’t burst, flex head forward at 30 degrees, inject cold saline into ear, head should move away
CN 5, 7- apply pressure to supraorbital notch
CN 9 - gag reflex
CN 10- check trachea using suction catheter or pulling intubation tube
In clinical settings, how would you test peripheral nerve response?
Pressure on nailbed
What is an example of a beta antagonist used in medicine, and why do we need to be careful when prescribing it?
Beta Blockers- commonly used to reduce cardiac output and therefore blood pressure by acting on beta 1 receptors
Also act on b2 causing bronchoconstriction, so don’t want to give to someone with difficulty breathing, or asthma
What are two amino acid derivatives that work to inhibit and excite the CNS?
Glutamate- excitatory neurotransmitter
GABA (Gamma-aminobutyric acid)- inhibitory neurotransmitter
What are the 4 main types of neurotransmitters?
Amino Acid Derivative (Glutamate, GABBA)
Catecholamines (Derived from Tyr- Epinephrine, Dopamine, Serotonin (Depression-Selective Serotonin Reuptake Inhibitors))
Acetylcholine’s (Neuromuscular Junctions)
Peptides (Substance P, endorphins)
How does GABBA signalling work and what are some examples?
GABBA ligand binds GABBA-A Receptor, causing conformation change in receptors and allowing Chloride Ions into cell, causing hyperpolarization.
Benzodiazepines and ethanol (alcohol) both enhance action of GABBA (tranquilizing effect)
Inhibitory
How do electrical impulses move from one neuron to another?
Most commonly chemical, using neurotransmitters.
Can also use GAP junctions which directly pass ions through to adjacent cells (i.e. myocytes of the heart)
How many spinal and cranial nerves do we have?
62 spinal (31 on each side) 24 cranial (12 on each side)
What feature on ependymal cells aid in CSF circulation?
Cilia
They also have microvilli, but they don’t aid in CSF circulation
What is the most common neurotransmitter within the CNS?
Glutamate
What is the main role of the Parietal Lobe?
Sensory integration. language interpretation, spatial/visual perception
What is the main role of the Temporal Lobe?
Primary auditory cortex, memory, understanding language
What is the Glasgow Coma Scale?
Patients are scored out of 15, based on their ability to respond/perform given tasks
Low score is bad
Eye(4), Verbal (5), Motor (6)
What are the cauda medullaris and cauda equina?
CM: L1-L2, ending of spinal cord
CE: Nerve root L2-L5, after the spinal cord has ended
Where does somatic information enter, and motor/autonomic information leave the spinal cord?
Somatic- Dorsal Horn
Autonomic- Lateral Horn
Motor- Ventral Horn
What is a dermatome?
Area of the skin supplied by single nerve from a single spinal root.
C1 is an exception, it does not have a dermatome
What are myotomes?
A block of muscles that are supplied by the same motor neurons
Do sensory and motor neurons contain ganglia/synapses?
No, they synapse on their target organ but don’t contain pre-post ganglionic neuronal fibres.
What are the names of the cranial nerves?
I. Olfactory nerve II. Optic nerve III. Oculomotor nerve IV. Trochlear nerve V. Trigeminal nerve VI. Abducens nerve VII. Facial nerve VIII. Vestibulocochlear nerve IX. Glossopharyngeal nerve X. Vagus nerve XI. Spinal Accessory nerve XII. Hypoglossal nerve
Which cranial nerves are grouped together and what are their broad function?
3,4,6
Eye movements, move them up, sideways
What is the function of Cranial Nerve 5
Trigeminal,
Motor supply for muscles of mastication and general sensory supply to face
What is the function of Cranial nerve 7?
Facial- both
Supplies muscles of the face
What is the function of Cranial nerve 8?
Vestibulocochlear- sensory
Hearing
What is the function of Cranial Nerve 9?
Glossopharyngeal- Both
Swallowing and Taste
What is the function of Cranial Nerve 10?
Vagus (wondering nerve)
Lowers heart and lungs, G.I. motility
Nerve of rest and digest
What is the function of Cranial Nerve 11?
Spinal Accessory
Supplies head and shoulder muscles
What is the function of Cranial Nerve 12?
Hypoglossal- Motor
Muscles of tongue
What is the function of Cranial Nerve 2?
Optic- sensory
Sight
What is the function of Cranial Nerve 1?
Olfactory- Sensory
Smell
What way can nerves move, in terms of anatomical locations?
Rostrally to rostral pole (front of head) or Caudally to caudal pole.
How is the cerebellum attached to the rest of the brain?
To the pons of the brainstem
What features within the brain separate the lobes?
Central Sulcus- separates frontal and parietal lobes
Lateral Fissure- separates temporal lobe from frontal and parietal
Parietal-Occipital Sulcus- separates the occipital from the parietal
What does the top of the posterior ileac crest indicate in relation to the location of the spine?
L4
What do sacral dimples indicate in relation to the spine?
S2, which is where subarachnoid space ends.
Are the cranial nerves apart of the CNS or PNS?
Cranial Nerves 1 and 2 are apart of the CNS, the rest are the PNS
