Nervous Flashcards
What is in the central nervous system (CNS)?
Brain & spinal cord
What is in the peripheral nervous system?
Everything apart from the brain & spinal cord
What does the motor efferent division do?
Conducts impulses from CNS to effectors with somatic and visceral sensory nerve fibres
What does the sensory afferent division do?
Conducts impulses from receptors to CNS with motor nerve fibres
What does the somatic nervous system do?
Conducts impulses from the CNS to skeletal muscles
- Somatic motor (voluntary)
What does the autonomic nervous system do?
Conducts impulses from the CNS to the cardiac muscles, smooth muscles and glands
- Visceral motor (involuntary)
What does the sympathetic division do?
Mobilises body systems during activity
What does the parasympathetic division do?
Conserves energy; promotes housekeeping functions during rest
What do neurons do?
- Communicate by electronic and chemical receptors and transmitters
- Messengers of the brain
What are the neurotransmitters in the brain?
- Acetylcholine
- Dopamine
- Noradrenaline/adrenaline
- Serotonin
- GABA
- Beta-endorphins
- Gluatamine
What are low levels of acetylcholine associated with?
Alzheimers
What are low levels of dopamine associated with?
- Parkinson’s disease
- Dopamine hypothesis for schizophrenia
What are varied levels of noradrenaline/adrenaline associated with?
- Elevated levels with arousal & excitement
- Low levels in depression
What are low levels of serotonin associated with?
Depression
What are low levels of GABA associated with?
Convulsions & epilepsy
What is over activation of glutamine associated with?
- Neural damage and death
- Damage from stroke
What stroke is more common?
Ischaemic stroke
What is an ischaemic stroke?
A blood clots stop the blood of blood to an area of the brain
What are causes of an ischaemic stroke?
- Thrombus (blood clot, damage to inside of blood vessel, fatty streak, plaque platelets stick to)
- Atheroma (atherosclerosis clot)
- Tumour (squeeze and press on blood vessels)
- Embolus (clot that travels from somewhere else)
- Atrial fibrillation (uncoordinated contraction of heart causing blood to recirculate and clot)
- DVT (deep vein thrombosis)
What is a hemorrhagic stroke?
Bursting blood vessel in the brain
What causes a hemorrhagic stroke?
- Aneurysm (abnormal dilation of the artery wall causes bursting leads to a brain bleed leading to apoptosis killing further cells surrounding)
- Congenital arteriovenous malformation - abnormal connection between arteries and veins
- Trauma
What is the difference between stroke and MI?
- A stroke is when neurons die
- A MI is when heart muscle dies
What is the pathophysiology of a hemorrhagic stroke?
- Blood leaks out of the cerebral circulation
- Nowhere for blood to go inside the enclosed cranial cavity
- Increased pressure on delicate neurons and blood vessels
- Less blood for perfusion of downstream tissue
What weakens the artery wall?
- Atheroma
- Destruction of elastin by proteolytic enzymes
- Continue high pressure on the collagen matrix due to hypertension
- Marfan’s syndrome
What is decussation?
Brain controls opposites side of the body
What are signs and symptoms of a stroke?
- FAST (Face dropping, Arm weakness, Speech difficulty, Time)
- Gait (ataxia) difficulties, balance
- Dysphagia
- Cognitive issues
- Anxiety
- Hemi-neglect
- Visual field changes
What is a TIA?
- Transient ischaemic attack
- Result when cerebral artery is temporarily blocked, decreasing blood flow to brain
What are some stroke risk factors?
- Increased age
- Gender (male)
- Ethnicity (more in non-europeans)
- Heredity
- Excessive alcohol and cigarette consumption → kills blood cells; increases BP
- High blood cholesterol levels (high ratio of LDL vs HDL; fatty acids)
- Diabetes → hypertension, hyperglycaemia
- Hypercoagulability
- Hypertension
What are modifiable risk factors?
- Excessive alcohol + cigarette consumption
- Cholesterol levels
- Hypertension
- Type 2 diabetes
How do you diagnose a stroke?
- Angiogram
- MRI
How do you treat ischaemic stroke?
The objective - remove obstruction & reperfusion
- t-PA tissue plasminogen activator, activate plasmin to dissolve clot e.g. Atleplase
How do you treat haemorrhagic stroke?
The objective - stop bleeding, stabilise intracranial pressure
- Decrease BP, anti-seizure meds, drain/evacuate, clip/coil aneurysm
- Sit the patient up to decrease pressure in head
What is a contusion?
Bruising/bleeding which is visible in imaging at the surface of the brain and also the back
What is a concussion?
Microscopic damage not visible on imaging with an expected full recovery
Why is mannitol given for brain damage?
- It is a diuretic
- Increased fluid loss lowers pressure in the brain
What is a epidural hematoma?
Bleeding between dura mater and skull
What is a subdural hematoma?
Bleeding between arachnoid mater and dura mater
What is coup/contrecoup?
Impact/damage on front of brain then rebound against back of skull causing further damage
What is expected with a concussion?
- Brief disruption in LOC, amnesia
- Microscopic changes to neurons and neuroglia
- Brain imaging is usually negative
- May show post-concussion syndrome but full recovery is expected
- Recurrent concussions can cause permanent damage
What is expected with a contusion?
- Bruising of the brain visible with imaging
- Brain cells will die and effects vary according to area impacted
- Full recovery may not occur
What are signs of increasing intracranial pressure?
- Increased BP (to provide more oxygen)
- Decreased HR (Mary’s law, inverse reaction between HR and BP)
- Pupillary response (increased pressure on oculomotor nerve affects pupillary response)
- LOC (pressure on brain can change consciousness)
- Temperature (pressure of hypothalamus can change temperature)
What is Cushing’s reflex?
Increased BP, decreased HR
What is the tentorium?
A fold in the dura mater which separates the cerebrum and cerebellum. The upper brain stem passes through an opening in the tentorium
What is tentorial herniation (coning)?
- Increased pressure forces part of the temporal lobe through the tentorial opening, squeezing the brain stem and damaging blood supply
- This affects the reticular formation and results in a coma
What occurs with tentorial herniation (coning)?
- Nerve III (oculomotor nerve) may be damaged resulting in a fixed and dilated pupil, first on the side of herniation and then alter on the other side
- Permanent ischemic damage occurs if the herniation reduces oxygenated blood below a critical threshold for more than a few minutes
What is Alzheimer’s disease?
- Progressive, degenerative
- Diffuse atrophy of the cortex
- Widespread loss of cholinergic neurons
What occurs if the hippocampus degenerates?
Impaired memory and learning
What occurs if the amygdala degenerates?
Inappropriate emotions & anxiety
What occurs if the frontal lobe degenerates?
Impaired speech, reasoning, personality (can be agitated, aggressive)
What is the pathophysiology of Alzheimer’s?
- Neuritic/senile plaques (Abnormal clusters of protein fragments, build up between nerve cells)
- Neurofibrillary tangles (in dead/dying nerve cells, twisted strands of proteins)
- Loss of up to 95% of cholinergic innervation on the cortex
- Decline of enzyme that produces acetylcholine
What is treatment of Alzheimer’s?
- Cholinesterase inhibitors
- Help manage symptoms of mild to moderate Alzheimer’s
What is Parkinson’s disease?
- Progressive degeneration of dopaminergic neurons from substantia nigra
- Leads to reduction in dopamine activity in basal ganglia affecting:
1) Learned, automatic movement
2) Monitoring and smoothing of voluntary movement initiated by motor cortex
3) Inhibition of antagonistic or unnecessary movements
What are the primary motor symptoms of Parkinson’s disease?
- Tremor - one sided, resting tremor, pill-rolling
- Rigidity - cogwheel or lead-pipe
- Bradykinesia - slow movements
What is treatment for Parkinson’s disease?
Levodopa + carbidopa
- Dopamine too large to cross blood brain barrier (BBB)
- Administer Levodopa that can pass BBB where is converts to dopamine
- Carbidopa added (decarboxylase inhibitor) that blocks conversion of levodopa to dopamine in the periphery so all the levodopa gets into the brain
What is Huntington’s disease?
- Autosomal dominant
- Progressive loss of neurons in the basal ganglia
- Increased motor output “choreiform movements”
- Usually presents 20-50 years old
- Personality and cognitive changes in later stages
What is multiple sclerosis?
- Autoimmune, progressive, demyelination
- Gte neurodegeneration in later stages
- Diagnosis usually 20-40 years old, more in females
What are symptoms of multiple sclerosis?
- Motor - limb weakness, loss of bladder/bowel control, speech
- Sensory - numbness, pain
- Visual - double vision, loss of vision
- Cognitive degeneration - thinking
What are different types of epilepsy?
- Tonic/clonic
- Grand mal
- Petit mal
- Temporal lobe
What are common features of epilepsy?
- Uncontrolled firing of a group of neurons
- Symptoms/presentation depend on location and extent of spread
What are treatments for epilepsy?
Drugs that increase GABA (inhibitory neurotransmitter)
What are risk factors of unipolar depression?
- Personality traits
- Monoamine depletion
- Stress & HPA axis dysregulation
- Changes in morphology or function of brain regions
- Other medical conditions
- Side effects of drugs
- Post-natal
- Social/environmental effects
- Genetics
What is the proposed mechanism of unipolar depression?
- During stress - increased activation of hypothalamic-pituitary-adrenal axis → increasing CRH, ACTH, cortisol
- Many metabolic effects of cortisol and decreased immunity, decreased appetite and sleep changes
- Cortisol also binds to receptors in the hippocampus and may lead to decreased synapse formation & neurogenesis
What does imaging show in depressed people?
- Smaller hippocampus (Involved in memory and emotion) → impaired memory
- Smaller frontal lobe (Involved in cognitive processing, concentration, suppressing negative thoughts) → impaired cognitive function
- Increased activity of amygdala (involved in emotion, reactivity to “threatening stimuli”) → impaired ability to identify threat
What is treatment for unipolar depression?
1) Aim is to reduce chronic stress
2) Drugs:
- SSRIs (selective serotonin reuptake inhibitor) - block reuptake of serotonin selectively
- MAOIs (Monoamine oxidase inhibitor) - non-selective, block noradrenaline and serotonin breakdown
- TCAs (Tricyclic antidepressants) - nonselective, block noradrenaline and serotonin reuptake
What are the risks of unipolar depression medications?
- Thereapuetic effect takes 2-6 weeks
- Adverse effect can occur on the same day
Therefore there is increased risk of suicide in the first few weeks
What is schizophrenia?
- Abnormal perception of reality therefore is a psychotic illness
- Unknown cause
- Imaging shows:
1) Enlargement of ventricles in the brain
2) Reduced size of temporal and frontal lobe
What are some positive symptoms of schizophrenia?
- Hallucinations
- Delusions
What are some negative symptoms of schizophrenia?
Flattened mood
How does dopamine affect symptoms of schizophrenia?
- Too much dopamine causes positive symptoms
- Too little dopamine causes negative symptoms
How do dopamine antagonists treat positive symptoms of schizophrenia?
They block the dopamine receptors, lowering dopamine levels
What is spina bifida?
- Incomplete formation of the vertebral arches (“split spine”)
- Occurs at any point of the vertebrae
- The more neurological structure contained within the sac, the greater the neurological impairment
- Problems with infection are ongoing since the cyst call in thin, porous and liable to rupture
- Accompanied by hydrocephalus in 90% of cases
- Links between environmental factors such as inadequate maternal folic acid level
What treatment is therefore for spina bifida?
Surgery
What would prevent spina bifida?
Sufficient amount of folic acid before and during pregnancy
What is a lumber disc herniation?
Herniated disc pushing on spinal nerves, compressing spinal arteries reducing blood flow or directly damaging the spinal cord
What types of spinal injury are there?
- Paraplegia - no movement in legs and trunk
- Quadriplegia - all four limbs and trunk affected
- Monoplegia - 1 leg affected
- Hemiplegia - one side either left or right
What are signs of acute stage of spinal injury?
- Flaccid paralysis, loss of reflexes, absence of somatic/visceral sensations below level of injury
- Loss of bladder/bowel control
- Possible reduction in sympathetic tone leading to vasodilation, hypotension, & decreased sweating
Why might spasticity occur?
- After acute period, spinal reflexes may occur below level of injury as these are mediated by the spinal cord.
- Inhibitory messages from higher brain centres cannot be conducted past injured area of spinal cord
What pathways are affected by anterior damage?
Prevention of motor function while maintaining sensory function
Why is outflow from the sympathetic nervous system often disrupted in spinal cord injury?
Sympathetic ganglia lie alongside the spinal cord (vasodilation below LOI, decreased sweating below LOI)
What other difficulties can be experienced with a spinal injury?
- Problems with deep breathing/cough
- Bladder/bowel function impaired
- Sexual function possible affected
- Integumentary - skin breakdown
What is poikilothermy?
Taking on the temperature of the environment
Why is there increased risk of DVT with a spinal injury?
- Immobile - decreased skeletal pump
- Pooling of blood and oedema
- Increased clotting
What are the first, second, and third-order neurons involved in the perception of pain?
1) Nociceptive - spinal cord
2) Spinal cord to thalamus
3) Thalamus to somatosensory
How does referred pain occur?
- Visceral and somatic pathways converge on the same spinal dorsal horn neurons projecting to the brain
- Difficult for the brain to identify the original source of pain
What stimuli active nociceptors (pain receptors)?
- Extreme heat and cold
- Pressure/cut, damage tissue
- Histamine
How does the body produce pain relief?
Block messages of pain getting to the brain
What is visceral pain?
Pain from the organs
What are two examples of referred pain?
- Gallbladder and liver also has pain in right shoulder
- Heart also has pain in left arm
What are the brain regions involved in perception and understanding of pain messages?
- Somatosensory
- Emotional centres (limbic system)
- Frontal lobe
- Hippocampus
What are “A-delta” fibres?
- Thinly myelinated, conduct fast impulses
- Respond to heat and touch
- Usually superficial, somatic
- Quick conduction to thalamus & somatosensory cortex
- “Fast”, “first”, “good”, “acute”, pain
- Well-localized, shapr, stabbing pain
- May lead to reflex withdrawal of affected body part for protection
What are C fibres?
- Unmyelinated and conduct impulses slowly
- Respond to heat, touch or chemicals
- Can be somatic or visceral
- Slower, circuitous route through thalamus & limbic system
- “Second” or “slow” pain
- Poorly-localized, diffuse, buring, aching, itching, dull pain
- More likely to transmit chronic pain and can also amplify local inflammation by releasing more inflammatory chemicals
