✅ M5 - Brain & Neurology Flashcards
What is the basic anatomy of the brain?
- Cerebrum containing the cerebral cortex: frontal, temporal, parietal and occipital (FPOT clockwise)
- Has grey matter (neural cell bodies) AND white matter (neural axon and dendrites)
- Has gyrus (ridges) and sulcus (valley) -> maximise SA - Cerebellum: coordinates movement posture
- Brainstem: cardiovascular and respiratory centre
What are the functions of the four lobes?
- Frontal lobe - primary motor cortex, responsible for movement, personality, and planning
- Parietal lobe: primary somatosensory cortex, responsible for awareness of surrounding & stereognosis (object manipulation)
- Temporal lobe: responsible for hearing and language.
- Occipital lobe: responsible for processing visual signals.
What are the different classifications of neurons?
- Structural:
- Unipolar
- Bipolar
- Multipolar
- Functional:
- Afferent (from receptor)
- Efferent (to muscle)
What parts are the neuron consist of?
- Soma (cell body)
- Dendrites
- Axon (tend to have myelin sheath & nodes of ranvier)
- Axon terminal (synapse)
What are different neuroglia and their functions?
- Astrocytes (‘star’)
- Provide physical support for neurons in CNS
- Help form blood-brain barrier (allows nutrition to comes in)
- Clean up debris & regulate neural environment - Oligodendrocyte: produce the myelin sheath to protect axon in neurons in CNS (multiple neurons at once)
- Muller: provide structural and metabolic (nutrition) support for neurons (mainly in the retina)
- Schwann: produces myelin sheath for neuron in PNS (one neuron at a time)
Describe the process of depolarisation - action potential - hypepolarisation in neural communication?
Axon has a selectively permeable membrane: allow some things through & stops others
-> Has ion channels (e.g. Na+ and K+ channels)
Neuron/Axon at rest:
- Na+ channels close
- Some K+ channels open
- Maintain in-axon potential at -70mV (RESTING MEMBRANE POTENTIAL)
Depolarisation (-ve to +ve)
- Reach threshold of excitation -> open Na+ channel AND change potential from -70mV to 40mV
- All Na+ channel open
- K+ channels close
Action potential/Repolarisation (+ve to -ve)
- K+ channel opens
- Na+ channel is blocked when 40mV is reached
=> reset the membrane potential to -70mV
Features of neural transmission?
- Saltatory conduction: action potential only occurs in nodes of ranvier, between myelin sheaths of axon => faster and save energy
- All-or-nothing: in order for an action potential to happen to pass electrical signals along the axon and between neurons, the membrane potential needs to exceed the threshold.
- Diffusion: movement of ions between outside and inside of the axon depends on diffusion (movement from high conc. to low conc. down the concentration gradient)
Describe the process of neural transmission between neurons? (mostly in chemical synapses)
- Action potential reaches axon terminal
- Vesicles containing neurotransmitters fuse with the pre-synaptic membrane.
- Release of the neurotransmitter into the synaptic cleft (exocytosis)
- The neurotransmitter binds to receptor on post-synaptic membrane (key-lock mechanism)
- Excitatory effect or an inhibitory effect on post-synaptic neuron -> leading or preventing an action potential to occur.
What are the structures in CNS and PNS?
- Central Nervous System (CNS):
- Brain (head)
- Spinal cord (rest of body) - Peripheral Nervous system (PNS):
- Cranial nerves (head)
- Spinal nerves (rest of body)
How is seizure defined?
- Same as convulsion
- Transient abnormal event resulting from discharge of cerebral neuron.
- Epilepsy is the continued tendency to have such seizures.
What are the features of seizures?
Two types of seizures: generalised (originate from one part, the spread to all parts of the brain) and partial seizure (only remain in one place)
- Generalised seizure
- Tonic clonic (grand mal): two phases, loss of body control (tonic phase) & body convulsion (clonic phase)
- Absence (petit mal): blanking/zoning out for few seconds
- Myoclonic: sudden, brief muscle jerks or twitches. - Partial seizure
- Induced aura: a sensory/perceptual experience prior to a seizure (warning sign).
- Jacksonian seizure (motor cortex): localized jerking movements in body
- Todd’s paralysis: temporary weakness or paralysis that occurs after a seizure
What are the causes of seizure?
- Trauma: Depressed skull fracture, penetrating brain injury, cerebral contusion, dural tear
- Cerebrovascular: Following cerebral infarction (stroke) -> abrupt loss of bloodflow to the brain
- Alcohol induced: Hypoglycaemia (low blood sugar levels) -> coma
- Others including pyrexia (high fever) and brain tumours.
=> In 2/3rds of cases, no definite cause is found.
What is Parkinson’s Disease, its causes and features?
- Overview: a neurodegenerative disorder, affecting 145,000 people in the UK
- Caused by genetic (10%) and environmental factors
- Genetic basis: associative genes (LRRK2, PARK2, SNCA, etc.)
- Environmental: reduced risk - coffee and smoking, increased risk - living in rural area and well-water - Features: motor symptoms
- Akinesia (impairment of voluntary movements)
- Resting tremor
- Rigidity
- Stooped posture and shuffling gait
- Other symptoms include: Loss of smell, Sleep disorders, Constipation, Depression & Anxiety, Mask-like face
What causes motor symptoms in Parkinson’s disease? (brain)
- Motor control in brain:
- Basal ganglia: subconscious control & coordination of learned movement => within the grey matter.
- Substantia nigra: moderates the activity of the basal ganglia with dopamine (neurotransmitter). - Why motor symptoms occur in Parkinson’s disease?
- Loss of dopamine producing neurones in the substantia nigra
- Lewy bodies within neurons disrupting normal neuronal functioning
- α-synuclein (regulating synaptic functions) is main constituent in Lewy bodies -> potential biomarkers
What is the diagnosis and treatment for Parkinson’s Disease?
- Diagnosis (clinical)
- Patients live ~10-15 years from diagnosis
- Death usually caused by bronchopneumonia - Treatment:
- Can give dopamine agonists (e.g. levodopa) => produce initial striking improvements
- No drugs alter the course of the disease (no cure)
