Topic 8: Muscle & Spinal cord Flashcards
What are the movements that motor systems generates?
reflexive
rhythmic
voluntary
reflexive movements
the involuntary movements generated in response to sensory stimuli
rhythmic movements
the repeatedly patterned movement
How is the voluntary movement different from others?
it is generated to achieve a goal
voluntary movement is the ultimate result of excitation of motor neurons in ________ & _________?
brainstem
spinal cord
T/F: strength of muscle contraction is proportional to the amount of excitation receives in lower motor neurons?
True
Larger amount of excitations -> greater force generation
What are parts of cerebral cortex that in upper motor neurons?
Explain each function
association cortex - desire to move
premotor cortex - motor programs
motor cortex - commands
What do association cortex influence?
cerebellum
basal ganglia
Where does the cerebellum influence?
motor cortex
brainstem
What does the basal ganglia influence on?
premotor cortex
Where does the brainstem influence on?
spinal cord
Where does the motor cortex influence on?
spinal cord
brainstem
Where do the vestibular receptors influence on?
cerebellum
brainstem
Where does the afferent voluntary movements travel to?
spinal cord
cerebellum
What are structures that have influences on brainstem?
cerebellum
motor cortex
vestibular receptors
brainstem control the muscle of ______
spinal cord control the muscle of ______
face
body
Upper motor neurons consist of ____?
motor & premotor cortex
basal ganglia
brainstem
Lower motor neurons consists of _____?
brainstem
spinal cord
What are the muscle fiber types?
slow oxidative fibers
fast, resistant fatigue (FR) or fast-oxidative glycolytics (FOG)
fast, fatiguable (FF) or fast-glycolytics (FG)
Characteristics of slow oxidative
high oxygen content, low ATPase activity & glycolytics
produce smallest force
high resistance
Characteristics of fast-oxidative glycolytics (FOG)
high ATPase activity & glycolytics & oxidative
generate medium force
Characteristics of fast-glycolytics
produce largest force of all 3 fibers
low resistance to fatigue
high ATPase activity & glycolytics but low oxidative capacities
What are muscle fibers that have slow oxidative?
What are muscle fibers that have fast-glycolytics?
postural muscles & soleus
gastrocnemius
What are structures that have influence on spinal cord?
motor cortex
brainstem
voluntary movements
motor unit
motor neurons & all of its fibers that innervated
What part of cerebral cortex is the motor command?
What part of cerebral cortex is the motor programs?
What part of cerebral cortex control the desire to move?
motor cortex
premotor cortex
association cortex
T/F: Most of the time, each muscle only contain one motor units?
False
It can contain different number of motor units
T/F: one motor unit can only innervate one type of muscle fibers?
True
T/F: Under normal conditions, when a motor unit stimulated then not all of the fibers in motor unit are stimulated?
False
In normal conditions, all of fibers innervated by motor units are stimulated
Motor unit recruitment refer to?
the # of motor units are activated during contraction
Few motor units, _______ (more/less) fibers activated, _____ (smaller/larger) force
less
smaller
Henneman’s Size Principle
motor units are recruited in order from smallest to largest
SO > FR > FG
What does Henneman’s Principle allow us to do?
allow a fine control of force at all levels of ouput while minimizing fatigue by using SO & FR first and only recruit FF fibers when higher forces are required
What will the higher frequencey of firing rate in motor neurons cause?
the larger amount of force
When do twitch contractions happen?
Will its force to be smallest or largest?
when the firing rate is slower than the contraction & relaxation of muscle fibers btw stimuli
smallest
When will the temporal summation contractions happen?
when firing rate is faster than the contraction & relaxation of muscle fibers -> increase force with each successive stimulus
How does unfused tetanus contraction compare to twitch, temporal summation & fused tetanus contractions in force generation & firing rate?
higher rate & force than temporal summation & twitch contractions but lower than in fused tetanus contraction
Proprioceptors
What are those types?
the receptors that respond to change in space & balance of the body to environment
Muscle spindles & golgi tendon organs
What are characteristics of muscle spindles?
innervated by gamma motor neurons
enclosed by connective tissue
run parallel with other fibers
have large-diameter sensory axons
What is the other name for muscle spindles?
What is the other name for Golgi tendon organs?
intrafusal fibers
extrafusal fibers
What type of contraction will cause the maximum force possible?
How does it do that?
fused tetanus
highest firing rate
What are type of motor neurons innervate Golgi tendons organ?
alpha motor neurons
What does Golgi Tendons organ respond to?
What does muscle spindles respond to?
change in muscle tension
change in muscle length
What type of proprioceptors that LMN innervate?
Golgi Tendons Organ = extrafusal fibers
Explain the figure
When either Golgi Tendons or Muscle spindles stimulated, there will be a gap of afferent firing rate
Information from proprioceptors is ________ (afferent/ efferent)?
afferent information to CNS
Describe 12 cranial nerves by its mnemonic
Only oil on true tits are fun and
Oldfactory/Optic/Occulomotor/Trochlear/Trigeminal/Abducens/Facial/Auditory/
give virgins all heat
Glossopharyngeal/ vagus/ accessory/ hypoglossal
Explain each of cranial nerves is sensory/ motor or both by mnemonic
Some Say Marry Money But My Brother Says Big Brain Matter More
What are CNs responsible for eye movements?
Describe explicitly the name of each
CN 3,4 & 6
occulomotor, trochlear & abducens
CN 12 is _____, responsible for ______
hypoglossal
tounge
extrafusal fibers
Golgi Tendons organ
CN 5 is ______, responsible for ______
trigeminal
muscles of mastification
intrafusal fibers
muscle spindles
CN 7 is _______, responsible for ______
facial nerve
facial expressions
What are the cranial nerves that are both motor & sensory?
Trigeminal (CN 5)
Facial (CN 7)
Glossopharyngeal (CN 9)
Vagus (CN 10)
What are the CNs that respond to sensory?
oldfactory nerve (CN 1)
optic nerve (CN 2)
auditory nerve (CN 8)
nucleus ambiguous
brain stem nuclei that have motor neurons travel with CN 9, 10 & 11
CN 11 is _______, responsible for _______
accessory nerves
neck muscles
T/F : reflexive moments are generated within the cortex & require consciousness
False
It’s generated within spinal cord or brainstem
What type of proprioceptors that act to carry afferent information in stretch reflex?
Why does stretch reflex have this type?
muscle spindle
because it has the great conduction velocity due to large-diameter axons -> mediate rapid reflex adjustments
What type of proprioceptors that act to carry efferent information in stretch reflex?
Golgi Tendons organs or alpha motor neurons
Characteristic of stretch reflex circuit
single synapse circuit btw afferent & efferent limbs
CN 9 is ________
Is it sensory/ motor or both?
Glossopharyngeal nerve
Both
Inverse myostatic stretch
the stretch that help muscle relax to prevent overdoing force & injury
What type of proprioceptors that respond in inverse myostatic stretch?
only Golgi Tendons Organ
Mechanism of inverse myostatic reflex
the primary afferent make synaptic contact with inhibitory interneurons, which inhibit alpha motor neurons of the same muscle -> force reduction
During stretch what are two mechanisms that involve?
monosynaptic synapse (stretch reflex)
reciprocal inhibition
reciprocal inhibition
the inhibition of antagonist during stretch to aid the stretch reflex
CN 10 is _____, responsible for _______
vagus nerve
sensory, motor & autonomic functions of viscera (glands, heart…)
What mechanism is important for noiceptive stimuli?
flexion & cross extension
Mechanism of Flexion & Cross extension
flexor muscles are activated while extensor muscles inhibited on the noiceptive stimuli to move the limb away
On the side contralateral to noxious stimuli, cross extension activates extensors & inhibit flexors
T/F: Neuron circuit in spinal cord can’t generate rhythmic movements without ascending or descending input
False
What does this figure represent?
represent the synaptic connection of pacemaker cells in generating rhythmic movements by central pattern generator
Describe the synaptic connection steps in A,B,C,D
A - glutamate binds to receptors allowing slow Na+ influx -> slowly depolarizing
B - Mg++ unblocks the NMDA receptors allowing Na++ & Ca++ rapid influx of depolarization
C - K+ channels open slowly -> K+ reflux
D - Mg++ reblocks NMDA channels -> Ca++ & Na+ stop flowing into the cells
Explain the synaptic connections of central pattern generators
1) cortex activate excitatory interneurons
2) Excitatory interneurons activate extensors muscles & interneurons that inhibit the antagonist (flexor muscles)
Where is the final common pathway to initiate movements?
inputs to alpha motor neurons
Where do alpha motor neurons receive input from?
input from UMN
input from spinal interneurons
sensory input from muscle spindles
