MSK 1 Flashcards
Describe the motor pathway from the cortex to the spinal cord
- signal comes from precentral gyrus and travels through internal capsule to the cerebral peduncles in the midbrain
- goes through the pons (through pyramidal tracts)
- in medulla, crosses over to the opposite side of the spinal cord
- lower motor neuron goes out the ventral horn of the spinal cord (cervical region for upper limb and lumbar region for lower limb)
What is the corticobulbar tract?
- some tracts from primary motor cortex don’t travel down spinal cord; corticobulbar tract
- CNIII synapses in midbrain
- CNV synapses in pons
- CN VI and VII synapse in pons
- CN X,XI,XII synapse in medulla
A spinal cord lesion will cause what effects on touch, pressure, proprioception, movement, pain, and temperature?
- ipsilateral loss of touch, pressure, proprioception and ipsilateral paralysis
- contralateral loss of pain and temperature (pain and temperature crosses over at the spinal level)
What effects would you expect to see with a lesion to the segmental medullary artery?
-none because it is part of the anastomosis
What effects would you expect to see with a lesion to the left posterior spinal artery?
- ipsilateral loss of pain, temperature, touch, pressure, proprioception at that spinal level (dorsal horn has lost its blood supply so no senses can come in)
- ipsilateral loss of touch, pressure, and proprioception at and below that spinal level (damage to the left dorsal columns will not allow these senses through)
What effects would you expect to see with a lesion to the anterior spinal artery?
- bilateral loss of movement at that level
- prevents crossing over of pain and temperature signals from the dorsal horn to the lateral spinothalamic tract on either side resulting in bilateral loss of pain and temperature sensation at that spinal level
What areas of the spinal cord are supplied by the branches of the segmental medullary arteries?
-lateral spinothalamic tract, corticospinal tract, extrapyramidal tracts
Describe how sensory information comes into the CNS from the PNS
- information travels along sensory axons of mixed spinal nerves to the dorsal root ganglion
- goes in through the dorsal root
- can cause immediate contraction of muscles by synapsing at ventral horn and going out through the ventral root
- synapse in the spinal cord between the dorsal and ventral roots indicates integration of information- can see central control so information is going up to the brain and going back down
What are limb compartments?
- limb compartments have one neurovascular bundle that supplies them (flexor nerves and extensor nerves)
- deep fascia is divided into an anterior flexor and posterior extensor compartment
- interosseous membrane between the bones (ligament- continuation of deep fascia)
- periosteum connects to layer of superficial fascia
What muscles can be synergistic with one another? Antagonistic?
- muscles that are within the same compartment can work together and be synergistic with one another
- antagonistic muscles are in different compartments
What is the purpose of the extensor muscles?
- reset the body into anatomical position from the changes that can happen from the flexor muscles
- many more flexor muscles because we have a greater ability to flex from anatomical position than we do to extend
What is supplied by the ventral and dorsal rami?
- ventral ramus innervates the muscles and skin on anterior body wall
- dorsal ramus innervates the muscles and skin on posterior body wall
What is the sensory component of the spinal nerves?
- mixed spinal nerve has deep muscular branches
- also has superficial cutaneous branches which bring sensation from the skin
What sensory receptors exist in the skin?
- free nerve endings which detect pain and temperature (unmyelinated fibres-allows for gate control of pain at spinal cord)
- Meissner’s corpuscles which detects touch/vibrations (round shape)
- Merkel cell which detects touch
- Ruffinian corpuscle which detects touch/pressure
- Pacinian corpuscle which detects pressure
What are ways to test proprioception?
- touch object with eyes closed
- heel to shin test
- take a digit and pull it into flexed or extended position and see if the patient can tell what position the toe is in
What is the breakdown of a motor nerve?
- 50% of axons coming from a motor nerve are sensory coming from sensory receptors in the muscle (wrap around skeletal muscle fibres in the spindle)
- large alpha motor neurons that cause the muscle to contract at the NMJ make up 30%
What sensory receptors are located in a muscle?
- Pacinian corpuscles that detect pressure in the muscle (part of proprioception)
- spindles and golgi tendon organs
- free nerve endings that detect pain within the muscle, joint capsule, around the joints, and within the joints
What is the pathway for a spinal cord reflex arc?
- information comes in and synapses in dorsal horn
- excitatory neuron sends message out ventral horn to the flexor muscle to contract
- inhibitory neuron sends message to inhibit the extensor muscles
Describe the Achilles tendon reflex
-S1, S2 buckle my shoe
Describe the patellar tendon reflex
-L3,L4 kick the door
Describe the biceps brachii tendon reflex
-C5, C6 pick up sticks
Describe the triceps tendon reflex
-C7,C8 lay them straight
Describe the brachioradialis tendon reflex
-C5,C6
What do central pattern generators allow for?
- spinal cord can coordinate complex movements
- ex: step on something sharp, withdraw the foot, at the same time neurons cross over to opposite side of spinal cord which causes the other side of the body to contract to prevent you from falling over
Describe central pattern generators of breathing
- pontine respiratory centres detect CO2 levels
- coordinates with two motor systems in brain stem that allow for diaphragm and intercostal muscles of thorax to contract
- breathing is somatic NS
