13. Nervous System I Workshop Flashcards
Describe the difference between the central nervous system and the peripheral nervous system
The CNS comprises the brain and spinal cord while the PNS is any nervous tissue outside of the CNS
The nervous system is a _________ of fibres which span the body, co-ordinating a diverse range of voluntary and ___________ actions. It transmits ______ between parts of the body and responds rapidly to changes within the internal and external ___________. It works alongside the _________ system to maintain __________.
network involuntary signals environment endocrine homeostasis
What is the role of the somatic nervous system?
It controls voluntary muscles and transmits sensory information to the CNS
What is being described by the following:
a. Processes sensory information, analyses, stores and makes decisions
b. Detects internal and external environmental changes
c. Produces a response to sensory information to effect change
a. Interneurons
b. Sensory neurons (Chemo-, Baro-, Osmoreceptors)
c. Motor neurons
Which nervous system controls involuntary movements
Autonomic
What effect does the sympathetic nervous system have on the following:
a. Pupil
b. Liver
c. Heart
d. Lungs
e. Gastrointestinal tract
a. Dilation
b. Stimulates the conversion of glycogen to glucose
c. Increase heart rate and blood pressure
d. Causes bronchodilation
e. Decreases motility and secretions
Name the specific body locations where the following branches of the ANS originate:
a. Sympathetic nervous system
b. Parasympathetic nervous system
a. Thoraco-lumbar
b. Cranio-sacral
Explain how the enteric nervous system is linked to the CNS.
Via the sympathetic and parasympathetic nerve fibres of the vagus nerve.
Describe the role of the following in the enteric nervous system:
a. Sensory neurons
b. Motor neurons
c. Interneurons
a. They monitor chemical changes via chemo-receptors and GI tract stretching via stretch-receptors
b. Governs the motility and secretions of the GIT and glands
c. Connects the two plexus
Define the following in terms:
a. Action potential
b. Nerve stimulus
c. Nuclei
d. Ganglia
e. Tracts
f. Nerves
a. The ability to create a nerve impulse
b. Anything that generates an action potential
c. Collections of neuronal cell bodies in the CNS
d. Collections of neuronal cell bodies in the PNS
e. Axon bundles in the CNS are called tracts
f. Axon bundles in the PNS are called nerves
Describe the main role of dendrites.
Dendrites are the receiving portion of the cell that communicates with other neurons/dendrites
Can axons regenerate? Explain.
If injured, axons can regenerate at a rate of 1-2mm per day, if the neuronal cell body is intact.
Describe TWO roles of the myelin sheath
Myelin sheath electrically insulates the axon and increases the speed of nerve conduction
State which vitamin is required as a co-factor in myelin production?
Vitamin B12
Describe ONE key difference between ‘grey matter’ and ‘white matter’.
Grey matter is mostly composed of cell bodies with dendrites and unmyelinated axons. White matter is composed primarily of myelinated axons.
Describe THREE key differences between ‘neurons’ and ‘neuroglial cells’.
Neurons are excitable while neuroglia are non-excitatory. Glial cells are far smaller than neurons and also 50 times more prevalent. They can also multiply and divide, unlike neurons.
List TWO key functions of neuroglial cells.
Surround and hold neurons in place
Supply nutrients and oxygen to neurons
Destroy pathogens and remove dead neurons
Name the different types of neuroglia that are found in the CNS and PNS respectively
CNS: Astrocytes, Microglia, Oligodendrocytes, Ependymal Cells
PNS: Schwann cells, Satellite cells
Name the neuroglial cell that:
a. Contributes to the blood brain barrier
b. Is phagocytic and is mobile in the brain
c. Provides structural support in PNS ganglia
d. Myelinates axons in the CNS
e. Produces cerebrospinal fluid
f. Myelinates axons in the PNS
a. Astrocytes
b. Microglia
c. Satellite cells
d. Oligodendrocytes
e. Ependymal cells
f. Schwann cells
Describe TWO key differences between ‘graded potential’ and ‘action potential’.
Graded potential is for short distance communication, occurs in dendrites and cell bodies and has no threshold. Action potential is for long-distance communication, is propagated along the axon and there is a threshold that has to be reached for it to take place.
Name TWO characteristics that facilitate graded and action potentials.
- Specific ion channels can open and close when stimulated
- Electrical difference accross the cell membrane (resting potential)
Name TWO stimuli that trigger ion channels
- Chemicals (hormones)
- Changes in voltage
- Mechanical pressure
Neurons at rest posess an _____________ gradient across the cell membrane. This is created by the build-up of __________ ions on the inside of the cell membrane relative to the extracellular fluid which contains more ___________ ions. The separation of charges create __________ energy. The resting potential is approximately_________ mV. Cells exhibiting a membrane potential are said to be ____________ or charged.
electrochemical negative positive potential -70 polarised
Describe in detail the resting potential of neurons
The resting potential is created by a build up of negative ions on the inside of the cell membrane, relative to the extracellular fluid:
- The extracellular fluid is rich in Na+ and Cl- ions and carries a positive charge.
- The intracellular fluid is rich in K+ and large negatively charged proteins and phosphates which cannot leave the cell, thus rendering a negative charge inside the cell relative to the outside.
- As the Na+ and K+ try to move back to equalise the charge, the separation of charges is maintained by the sodium-potassium pump which pumps 3 Na+ out for every 2 K+ it pumps in, using ATP.
Describe in detail all steps in the following processes:
a. Depolarisation
b. Repolarisation
a. Depolarisation is triggered by stimulation of a nerve ending. The threshold value of -55mV must be reached in order to generate an impulse. Na+ channels open, allowing Na+ to flood into the cell up to about +30mV, thus letting a positive charge build up inside the cell.
b. K+ channels open much more slowly than Na+ channels, so just as Na+ channels are closing, the K+ channels open, allowing K+ to flood out of the cell, restoring the membrane potential to -70mV.
Explain what is meant by the:
a. Refractory period
b. Absolute refractory period
c. Relative refractory period
a. The period of time after the repolarisation in which a neuron cannot generate another action potential since Na+ and K+ are on the wrong sides of the membrane
b. During the absolute refractory period, not even a strong impulse can generate an action potential
c. During the relative refractory period, a larger than normal stimulus is needed to generate an action potential
Describe the role of the Nodes of Ranvier.
At the nodes of ranvier, there are high concentrations of Na+ gates, causing the current to appear to jump from node to node.
Describe in detail how the ‘synapse’ transmits a signal.
When the action potential arrives at the synaptic end bulb, the depolarisation causes Ca2+ to flood in which causes exocytosis of synaptic vesicles, causing neurotransmitters to be released into the synaptic cleft.
Neurotransmitters diffuse accross the synapse and bind to receptors on the post-synaptic neuron, opening the ion channels, generating an action potential in the post-synaptic nerve.
Explain why ‘ice’ is applied to an injury.
To dampen the pain signals travelling from the site of injury to the brain.
Which category do the following neurotransmitters belong to?
a. GABA
b. Dopamine
c. Acetylcholine
d. Serotonin
a. Amino acid
b. Monoamine
c. Unique molecules
d. Monoamine
Explain TWO differences between ‘excitatory’ and ‘inhibitory’ neurotransmitters.
Excitatory neurotransmitters causes depolaristation of the post-synaptic neuron and causes Na+ ion channels to open, making the inner membrane more positive.
Inhibitory neurotransmitters causes hyperpolarisation of the post-synaptic neuron by causing the K+ ion channels to open and the inner membrane to become more negative.
Name TWO ways in which neurotransmitters are inactivated following a nerve impulse.
- Enzyme breakdown (eg. MAO)
- Diffusion
- Re-absorption
Name the amino acid precursor of glutamate.
Glutamine
Indicate if GABA is a major inhibitory or excitatory neurotransmitter.
Inhibitory
Name ONE vitamin needed for conversion of glutamate to GABA.
Vitamin B6
Name the amino acid precursor of:
a. Serotonin
b. Dopamine
a. Tryptophan
b.Tyrosine
Describe serotonin’s role in the gastrointestinal tract.
It is involved in intestinal motility (peristalsis) and epithelial cell secretion.
Name TWO functions (not GI tract) of serotonin.
Attention
Sleep
Pain regulation
State the location in the brain where most dopamine is stored.
The substantia nigra
List TWO functions of dopamine.
Plays a key role in movement and the reward mechanism. Also regulating muscle tone, cognition and emotion
List ONE function of acetylcholine.
Muscle contractions
Cognition
Name TWO natural body analgesics
Endorphins
Enkephalins
Dynorphins
List ONE neuropeptide that enhances pain.
Substance P
List TWO neurotransmitters broken down by MAO.
Serotonin
Dopamine
Adrenaline
Noradrenaline
List TWO neurotransmitters broken down by COMT.
Adrenaline
Noradrenaline
Dopamine
Describe TWO signs / symptoms of an injured spinal nerve.
Pain and altered sensation in the associated dermatome.
Describe the main role of spinal nerves.
Spinal nerves carry impulses to and from the spinal cord.
Describe how the signs / symptoms develop in carpal tunnel syndrome (CTS).
The median nerve in the carpal tunnel of the anterior wrist becomes compressed due to fluid retention (pregnancy), overuse, trauma or conditions such as RA, hypothyroidism or acromegaly. This causes tingling, numbness and pain in the median nerve distribution.
List TWO pathologies that can cause CTS.
Rheumatoid Arthritis
Hypothyroidism
Acromegaly
State TWO signs / symptoms of Carpal Tunnel Syndrome
- Tingling, numbness or pain in the median nerve distribution
- Weakness of grip and weak thumb opposition
List ONE test used to diagnose CTS.
Tinel’s test
Phalen’s test
Define Bell’s palsy.
In Bell’s Palsy, the nerve that controls facial muscles, becomes inflamed or compressed
List ONE viral cause of Bell’s palsy.
Herpes simplex
Name TWO characteristic signs / symptoms of Bell’s palsy.
- Sudden, unilateral weakness or paralysis of the facial muscles
- Cannot close affected eye
- Loss of taste and intolerance to loud noise if severe
Using definitions compare Guillain barre syndrome and multiple sclerosis.
Guillain-Barre is a form of post-infectious de-myelinating disease with neuritis and acute, ascending, progressive inflammation of peripheral nerves.
Multiple sclerosis is an autoimmune inflammatory disease causing demyelination of axons in the CNS and damage thereof.
Name the pathological feature common to Guillain Barre Syndrome (GBS) and multiple sclerosis.
They are both de-myelinating
List ONE viral cause of GBS.
EBV
flu
Describe what is meant by ‘molecular mimicry’ in GBS.
The antibodies formed against the virus cross-reacts with the lipids in myelin due to structural similarities.
Name TWO signs / symptoms of GBS.
- Sudden, progressive, bilateral, ascending paralysis
- Neuropathic pain in legs
- Paraesthesia and sensory changes
Describe the pathophysiology of multiple sclerosis.
T-lymphocytes attack myelin antigens, causing multiple areas of sclerosis along the axons which disrupts conduction
Describe the main pattern of multiple sclerosis.
Most MS follow a relapsing-remitting pattern (85%)
Explain how the following vitamins can contribute to multiple sclerosis:
a. Vitamin D
b. Vitamin B12
a. Vitamin D increases the myelin production by oligodendrocytes
b. Vitamin B12 acts as a co-factor in myelin formation and has immunomodulatory effects.
List ONE viral trigger of multiple sclerosis.
EBV, measles
Name the diagnostic tool which can be used to view optic nerve demyelination in multiple sclerosis.
Opthalmoscopy
List FOUR signs / symptoms of multiple sclerosis.
- Visual symptoms: blindness, double vision, nystagmus
- Deafness / loss of balance
- Burning, pulling sensations
- Tingling and loss of sensation
- Weakness
- Cognitive changes / depression
- Bladder urgency / incontinence
Define motor neurone disease (MND).
MND is the progressive degeneration of motor neurons in the spinal cord, motor cortex and brain stem.
Discuss ONE suggested pathophysiology for MND.
The current hypothesis focus on abnormal mitochondrial function causing oxidative stress in motor neurons.
List TWO characteristic signs / symptoms of MND.
- Weakness in upper limbs
- Wasting of hand muscles and limb tremors at rest
- Later stages: legs affected, slurred speech, dyspnoea, dysphagia, respiratory failure
Describe the difference between dementia due to:
a. Alzheimer’s disease (AZ)
b. Vascular dementia
a. In AZ, there is the degeneration of the cerebral cortex and reduced acetylcholine
b. In vascular dementia, the degeneration is due to cerebrovascular disease (eg. stroke) and poor oxygen to the brain.
Describe in detail the pathophysiology of AZ.
Beta-amyloid plaques deposited around neurons cause inflammation.
Lack of acetylcholine affects communication between neurons.
Widespread neuronal dysfunction and tissue atrophy.
Name the areas of the brain affected by:
a. Earlier stages of AZ
b. Later stages of AZ
a. Hippocampus
b. Amygdala
Using pathophysiology, compare Parkinson’s disease with Alzheimer’s disease.
In Parkinson’s disease there is the degeneration of dopaminergic neurons in the substantia nigra and the accumulation of abnormal proteins called Lewy bodies within neurons.
In AZ, there is the deposition of beta-amyloid plaques around neurons and decrease of acetylcholine.
List TWO causes of Parkinson’s disease.
- Mitochondrial dysfunction
- Toxic environmental factors: pesticides, herbicides, carbon monoxide poisoning
- Diet low in polyunsaturated fats, constipation
List THREE characteristic signs / symptoms of Parkinson’s disease.
- Bradykinesia (short shuffling gait)
- Resting tremor (pill rolling)
- Flexed posture
- Muscle rigidity: mask-like face
- Lack of normal subconscious movements: arm swinging
Explain how the following factors could contribute to AZ:
a. Homocysteine
b. Stress
c. Hormones
d. Heavy metals
e. Chronic inflammation
a. High homocysteine is pro-inflammatory
b. Chronic stress leads to high levels of cortisol
c. Low levels of oestrogen and testosterone can affect the brain negatively
d. Metals such as mercury, aluminium and copper degenerate the Blood Brain Barrier
e. Chronic inflammation promotes brain deterioration
Identify which gene is associated with AZ
ApoE4
Name TWO nutritional deficiencies associated with AZ.
B-vitamins (B1, B3, B6, Folate, B12), Omega-3 Fatty Acids
Name ONE micro-organism that may contribute to AZ.
P. Gingivalis; Herpes simplex
