Intro to Neurology Flashcards
What is the PNS divided into?
- Somatic PNS: controls motor and sensory function for the body wall e.g. skin (sensory neuron), skeletal muscles (motor neuron)
- Autonomic nervous system: has sympathetic and parasympathetic arms.
what is the difference between afferent and efferent axons?
Afferent axons: arrives the CNS
Efferent axons: Exits the CNS
what are interneurons?
CNS neurons that synapse with other neurons within the brain and spinal cord
what are the dorsal and ventral roots that emerge from the spinal cord part of?
the PNS
what are the afferent and efferent axons bundled into
They are bundled into fascicles surrounded by perineurium
what is the whole nerve inside
the whole nerve is in a tough epineurium capsule.
what is the blood brain barrier formed of
Astrocytes
what is the function of microglia and oligodendrocytes
Microglia: act as immune cells
Oligodendrocytes: produce myelin sheath
what is the way PNS regenerate?
Axons in PNS can regenerate after injury:
-injury leads to stimulation of phagocytes, which remove debris which would otherwise inhibit regrowth
What causes neuropathic pain in the PNS?
May be compromised by aberrant axon sprouting and non-specific target reinnervation – can lead to neuropathic pain i.e. not very specific if you cut the nerve from your spinal cord to your toe, for the nerve to find its way back is quite hard, so you never get complete regeneration.
Why do CNS have limited regenerative capacity?
- there are inhibitory molecules in the CNS but not in the PNS, Glia exert inhibitory influence on regeneration
- Glial scars form in place of injured brain tissue
- Absence of guidance cues that stimulate axon growth
what are the 2 sensory pathways and what is a key difference?
Dorsal column-medial lemniscus pathway:
Conveys fine touch, vibration and two-point discrimination
Spinothalamic pathway:
Conveys pain and temperature sensation
the point at which they move from one side to another is the difference.
Dorsal column pathway- enters the spinal cord at the same side of the body and then goes to the brain-stem and then switches side.
BUT the spinothalamic pathway enters the spinal cord and immediately goes to the other side of the patient.
what is the grey matter and white matter
grey matter- cell bodies of neurones
white matter- contains ascending sensory axon tracts from spinal cord to sensorimeter of the brain and descending motor axon tracts from the sensorimeter cortex of the brain to the spinal cord.
what cells produce myelin sheath in the CNS and the PNS
Oligodendrocytes: CNS
Schwann cells : PNS
what cells produce myelin sheath in the CNS and the PNS
Oligodendrocytes: CNS
Schwann cells : PNS
What are the motor pathway types
Lateral corticospinal tract.
Motor pathways are an efferent pathway, so they come from the pregental gyrus (motor cortex) and then go down through the brainstem, which is where they jump to the other side of the nervous system and then go down the spinal cord. They send the signal down teh spinal cord on the (the same side the target cell is acting on), therefore if you injure that side of the system you will also injure that side of organs too.
Vestibulospinal tract:
receives input inside the ear. Creates microtwtiches to hold your balance.
-doesn’t cross sides, works on same side.
what side does stroke effect?
Clinical syndrome.
Tends to cause problems on the other side of the brain (contralateral)
What is upper motor neurone weakness and what is it caused by
Upper motor neurone and lower motor neurone.
Upper motor neurone:
Cerebral cortex to your spinal cord.
IF cord or brain is damaged you get upper motor neurone weakness.
Stroke, there flexing muscles in upper limb in stronger and it extenses a lot stronger in the leg which allows it to stay straight.
What type of arteries can strokes affect and what does it cause?
Middle cerebral artery: most commonly affected-often results in weakness and loss of sensation on the other side (contralateral)
Posterior cerebral artery: strokes often affect occipital lobe-result in visual loss on the contralateral side
Anterior cerebral artery: strokes often cause contralateral leg weakness
what does strokes in the brainstem affect?
-May cause problems with balance, eye movements, speech and swallowing, breathing.
What is parkinsons disease and what are the main clinical features and what treatment is there
-slowly progressive degenerative disease affecting the basal ganglia.
-loss of neurones from the substantia nigra to the caudate and putamen ( basal ganglia)
Main clinical features:
-Rigidity ( stiffness)
- tremor ( shaking)
- bradykinesia ( reduced movement)
Neurotransmitter associated is dopamine
-treated with the precursor levodopa, which is used as dopamine does not cross the blood brain barrier but levodopa crosses the blood brain barrier and is converted to dopamine.
Joe is a 72 year-old retired accountant. He has lost voluntary movement and sensation in his left arm, but the muscles still show reflex activity. His right arm and both legs function normally.
- Voluntary movement AND sensation lost but only LEFT arm. Legs fine.
- Injury must be to region(s) in RIGHT hemisphere containing both motor and sensory neurons/axons - but only from arm.
- Injury likely to be close to the sensorimotor cortex (in reality sensory and motor cortices, anatomically close but distinct) for the arm.
- Not peripheral nerve as reflex activity intact.
- Unlikely spinal cord as only ONE arm affected affected and legs fine.
- Cause - age 72- stroke?
Sophie is a 19 year-old motorcyclist. She has lost voluntary movement and sensation in her left arm. The muscles do not show reflex activity. Her right arm and both legs function normally.
Voluntary movement AND sensation lost but only from one side - but NO reflex activity. (Legs fine)
- Likely to be a peripheral nerve injury to the left arm/shoulder since there is no reflex activity.
- Unlikely to be spinal cord as right arm fine
- Young motorcyclist - motorbike fall/accident?
what is one spinal nerve surrounded by?
Epineurium
