structure n function of motor neuron Flashcards
where do upper motor neurones originate and where do they travel to?
cerebral cortex -> brain stem/spinal cord
where do lower motor neurons begin and where do they travel to?
begin in spinal cord and go to innervate muscles and glands throughout the body
what neurotransmitters do upper motor neurons use?
glutamate
what neurotransmitter do lower motor neurons use
acetylcholine
which neurons are involved in reflexes - upper lower or both
just lower - quicker
in voluntary actions which neurons are involved - upper lower or both
both, because voluntary actions are backed by thoughts
involves motor neurons in the brain
what is a ganglion
a collection of neuronal bodies found in the voluntary and autonomic branches of the peripheral nervous system (PNS)
what are oligodendrocytes
myelinating cells of the CNS
they produce myelin
what are astrocytes
specialised glial cells
support neurons, provide a suitable environment for neuronal signalling
what are glial cells
help support, connect, and protect the neurons of the central and peripheral nervous systems
what does denervation mean
damage to peripheral nerves
what symptoms do upper motor neurons show if they are damage
spasticity
normal peripheral nerves
easily diagnosed by clinical examination
what symptoms do lower motor neurons show if they are damaged
flaccid
loss of axons or peripheral nerve cell body
what are the 2 types of sensory function
- Discriminative touch
- Ability to distinguish objects, shapes & surfaces with fingers & skin
- Pain & Temperature
how may myelin be damaged
acquired or inherited
how may the axon be damaged
- Direct injury
- Toxins
- Metabolic disturbances
- Secondary damage due to damaged myelin
how may there be loss of motor and/or sensory function in the distribution of the nerve affected
always due to axon damage
name the 3 different ways trauma can damage an axon
compression
transection
stretching
give examples of peripheral neuropathy which may lead to axon being damaged
- Diabetes, B12 deficiency
- Inflammation, autoimmune
- Infection, HIV, Leprosy
- Drugs & Toxins
- Inherited
how may peripheral neuropathy be classified (4 types) and briefly what does each one mean
- Length dependant
- Denervation & loss of function in a length dependent manner
- Non-length dependant
- Patchy process which affects both long & short nerves
- Traumatic causes tend to me non-length dependant
- Mononeuropathy
- Specific nerve damaged, e.g., median nerve
- Radiculopathy
- Damage at root
how may peripheral neuropathy be classified (4 types) and briefly what does each one mean
- Length dependant
- Denervation & loss of function in a length dependent manner
- Non-length dependant
- Patchy process which affects both long & short nerves
- Traumatic causes tend to me non-length dependant
- Mononeuropathy
- Specific nerve damaged, e.g., median nerve
- Radiculopathy
- Damage at root
how may damage to axons due to trauma be classified - 3 types, briefly describe them and state can it recover?
- Axonotmesis - only a few axons damaged
- Can recover but slow and may be incomplete
- Neurotmesis - complete transection of peripheral nerve - both nerve & nerve sheath are disrupted
- Recovery required grafting transected ends
- Medical cause
- Peripheral neuropathy
how fast can an axon regrow - distance
- Recovery required axon regrowth (1mm/day)
name two types of myelin damaged, and which is permanent
- Neuropraxia - damage to myelin on nerve - temporary & reversible
- Can happen due to trauma, surgery, anaesthesia, or sports like football and rugby that stretch or compress the nerve
- Demyelination - Damage to myelin around nerve
- slows down conduction of nerve, and can result in nerve not working at all where myelin is damaged
what is Wallerian degeneration
- Wallerian degeneration is the breakdown of nerve fibres and their protective coating after an injury or disease damages the nerve cell body.
symptoms of a damaged sensory nerve
- Altered sensation
- Numbness
- Pain
- Paraesthesia
symptoms of a damaged motor nerve
- Atrophy
- Weakness
- Paralysis
changes in muscles would you experience after denervation
- Atrophy
- Spontaneous motor activity
- Fibrillations and fasciculations
- Cramps
- Muscles remain visible for up to 2 years without a nerve supply after which they fibrose and cannot return to normal function
