Motor System Flashcards
What are movements of the skeletal muscles and functions of the smooth muscle, cardiac muscle, and glands controlled by
- skeletal muscle = somatic motor system
2. Smooth muscle, cardiac muscle, glands = autonomic system
What anatomy is in the somatic motor system?
What is important about all these structures?
- Motor cortex in telencephalon = highest centre. Involved with organising fine voluntary movements
- Basal nuclei (corpus striatum) = planning motor function
- Thalamus
- Red nucleus and substantia nigra in the mesencephalon, midbrain = generate motor output
- Cerebellum: compare what planned to do with what happened
- Nuclei in pons and medulla oblongata
- Spinal cord
- Cranial and spinal nerves
- efferent spinal nerves which supply skeletal muscle via NMJ
- ## Skeletal muscleAll these structures must be functioning for a muscle to do what you want it to do
What influences what in the somatic motor system?
- Higher centres influence lower
When do and how come skeletal muscle act in isolation?
Even though the higher centres influence the lower, spinal/ cranial nerves and the skeletal muscles they innervate also communicate directly with the sensory system and can act in isolation (reflexes)
Diff types of SOMATIC motor neurons
- Upper motor neurons (take info from brain to lower motor neurone)
- Lower MN (synapses with muscle via NMJ)
What is the highest centre involved in motor system
Motor cortex which is involved in organising really fine, complex movements
What is the role of the Basal nuclei (corpus striatum)
involved in planning and decide what movement going to do
Role of thalamus
relay point for lot of functions.
Involved in sending info to areas where motor output is generates from
Red nucleus and substantia nigra
- in midbrain (first part of brain stem)
2. generate motor output
Cerebellum
- involved in coordination and comparing what planned to do with what actually happened
Nuclei in pons and medulla oblongata
- Nuclei in very back of brain in brain stem
2. contain nuclei that are cell bodies that can generate motor output
Upper motor neurones
- contained entirely within the CNS, cell bodies in the motor cortex or motor nuclei of other areas of the brain
- synapse directly on lower motor neurons or via interneurons
- Initiate, regulate, modify and terminate LMN activity required for voluntary movement of skeletal muscle
- not required for muscle function*
Lower motor neurons
- cell body in the CNS (brain or spinal cord)
- axon in the peripheral nervous system. = form NMJ
- Run via spinal or cranial nerves to innervate skeletal muscle
- If AP in LMN = contraction
- Functionality regulated by UMN but can fire without UMN input = REFLEX = INVOLUNTARY
- Muscle can onyl contract with intact LMN
What are 2 diff pathways UMN can run?
- Run entirely in brain = area of brain to cell bodies for a particular cranial nerve
- from brain, down spinal cord to synapse
- whole job to tell LMN what to do
- Initiate, regulate, modify and terminate movement
- needed for any kind of movement
- Not required for muscle function
- Exitatory or inhibitory (more)
What is different about the UMN synapsing for particular vs general movement?
- Specific = UMN synpase directly onto LMN
2. supplying several diff muscles at once = via internerone
Where do the UMN that are supplying LMN for flexor and extensor muscles
- UMNs to spinal LMNs supplying flexor muscles travel in the lateral funiculi (outsides) of the spinal cord.
- UMNs to LMNs
supplying extensor muscles travel in the ventral funiculi of the spinal cord. - Helps to localise lesion e.g. if issue with extensor muscles
LMN for fore and hind limb location
- forelimb = cervical intumescence (C6-T2)
- ## Hindlimb = lumbar intumescence (L4-S3)so thick as loads of motor cell bodies
Why does muscle feel slightly hard even when not contracting?
- LMNs have constant sub threshold depolarisation so ACh is being released.
- If lost LMN funciton or under deep anaesthesia = flacid
What clinical sings would you except to see in hindlimbs of an animals which had damage to spinal cord in the region of the lumbosacral intumescence
- Lost muscle tone in muscles of hind limb
- no reflexes
- just to motor = can still feel just not do anything about
- won’t be able to walk as can’t make muscle move
- bulk of muscle would atrophy v quickly
What is a motor unit
LMN, NMJ and skeletal muscle fibres
How would damage to radial nerve affect the function of the muscle supplied by this nerve
- Radial nerve = LMN in terms of motor function
- atrophy, loss of reflexes, loss of tone
- doesn’t matter where along nerve damage occurs = same sing
What is happening is super rigid
- Inhibitory UMN help to reduce output of LMN = upright but not stiff.
- Damage to UMN inhibitory as muscles can still contract and not being told not to.
- UMN modulate amount of movement and contraction