spinal cord Flashcards
what is gray matter?
- part of CNS that are abundant in cell bodies of neurons> axons
- unmyelinated
what is white matter?
- axons that carry info up and down
- myelinated
what is the structure of spinal cord?
cervical (7), thoracic (12), lumbar (5), sacral (5) , coccyx (4)
describe cross section of spinal cord
- white matter surrounds gray matter
what does ventral horn contain ? what does this allow?
- motor neurons so stimulation causes movement
how does info travel in ventral horn?
- info travels down ventral roots
what happens in dorsal horn?
- sensory information is localised
where does info travel in dorsal horn?
- travels down dorsal roots
what is the intermediate zone? what does it contain?
- contains interneurons which intergrate info
what is the relationship between body regions known as?
- somatotopy
what does the lateral descending system contain?
- corticospinal and rubrospinal tracts
what is the purpose of corticospinal fibres?
- influence movement of every body part
- useful for individual finger use
what do rubrospinal fibres compensate for?
- loss of descending corticospinal input
- can’t compensate its ability to use fingers individually
where are lateral descending system fibres found and what movement does it influence?
- fibres found in dorsolateral part
- influences lateral muscular movement
what does medial descending system consist of?
- vestibulospinal and reticulospinal tracts
what is vestibulospinal tract involved in?
- retains balance when body is moved
- external disturbance
what is reticulospinal tract involved in?
- retains posture and balance during own volitional movements
- internal disturbance
where are the fibres in medial descending system found and what does it influence?
- fibres found in ventro- medial white matter
- influences medial muscles
why is the vestibulospinal tract important?
- maintenance of balance
what is reticulospinal tract important for?
posture
what is the medial lemniscus ascending pathway? what info?
- carries sensory info from joint and skin
- info about fine touch, vibration, 2 point discrimination, proprioception
what is the spinothalamic ascending pathway?
- conveys sensory info about crude touch, pain and temperature
what does the position of spine determine?
- what part of body each nerve serves
how many pairs of spinal nerves are there and how is size determined?
- 31 pairs
- determined by how many muscles served
what is the two point discrimination?
- ability to recognise that two objects are touching you
what is a motor unit?
- neurone and the fibres they contract
how are muscles controlled?
motor pools of neurons
how many fibres can a single neuron innervate?
many fibres
how many neurons used for fine movements?
many neurons used
why are hands and feet special?
- highly innervated
- areas have enlarged spinal nerves
how is info coded in sensory system?
- firing frequency codes for intensity
what does intensity of stimulus determine?
- size of receptor potential and frequency of action potential
what code is used by motor neurons?
rate code = signals amount of force exerted by a muscle
what is the dorsal root ganglion?
- cell bodies of incoming sensory neurons lie outside the spine in a series of ganglion
- unlike motor neurons as cell bodies in ventral horn
what is a dermatome?
- area of a skin supplied by nerves from single spinal root
compare single action potentials to multiple action potentials
- single APs produce single twitches
- multiple APs occur in quick succession; force in muscle builds up
what is maximal contraction?
- tetanic contraction where rate of muscle will be unable to contract further
- muscles cannot relax between
what are reflexes?
- rapid automatic control of movement
- little or no voluntary control
what are the two types of reflexes with examples
- simple e.g. spinal stretch reflex
- complex e.g. swallowing
what is reticular formation?
- set of interconnected nuclei that are located through brainstem
what are vestibular nuclei?
- nuclei for vestibular system
- located in brainstem
what are Gnana cells?
- tiny cells that contain neurons, involved in filtering information
what are the three pathways of the cerebellum?
- superior cerebellar peduncle, middle cerebellar peduncle and inferior cerebellar peduncle
describe superior cerebellar peduncle path
- efferent pathway to red nucleus and cortex via thalamus and sup colliculus
describe middle cerebellar peduncle path
- most fibres originate in pons, input from sensory, visual, vestibular and motor systems
describe inferior cerebellar peduncle path
- carries info to and from spinal cord and vestibular nuclei
why does red nucleus appear pink?
- due to blood vessels
what does red nucleus receive?
- large input from cerebellum and primary motor cortex
what are the two basal ganglia pathways? what do they do?
- direct pro- movement
- indirect anti- movement
- work in opposition
what is the direct pathway in basal ganglia?
- runs directly through; short loop has excitatory effect on cortex
- net movement is pro- movement
what is the indirect pathway of basal ganglia?
- takes a longer loop that has inhibitory effect so anti- movement
what does basal ganglia damage cause? give an example
- states where there is too much/ too little movement
Parkinson’s disease can’t trigger movement
