neuromuscular structure and function Flashcards
what is the function of the cerebral cortex
- language
- reasoning and abstract thinking
- sensory and voluntary motor control
what is the function of the basal ganglia
- initiation and execution of movements
- facilitate desired movements and inhibit unwanted competing movements
(chooses actions that are likely to lead to positive consequences)
what is the function of the hypothalamus
- metabolism and temp
- autonomic NS (cardiovascular and cardiorespiratory rhythm)
what is the function of the limbic system
- processing and interpretation of sensory info
- controls motivation and goal directed behaviour influencing the initiation and maintenance of exercise routines
- promotes adaptive reactions to physical challenges and aids in the management of stress related hormones
what does the limbic system release and what is the function
- release of endorphins that contribute to the feelings of pleasure and euphoria (runners high)
- leads to improved mood and reduced perception of pain during PA (exercise induced hypoalgesia - pain reduction)
what is the function of the brainstem
- passage connects motor and sensory neurons to the spinal cord
- contain nuclei that regulate the cardiac and respiratory functions
what is reduced vagal tone from brainstem
increased sympathetic nerve activation therefore increased HR and ventilation
what is the function of the cerebellum
- processes the info necessary to regulate body posture and equilibrium (balance)
- receives sensory info form sensory afferents
- sends info to thalamus and than cerebral cortex
what is the corticospinal tract
collection of axonal nerves bundles (white matter) initiating at the cerebral cortex, passing through the brainstem and terminating on lower MNs
what occurs at the pyramidal decussation
90% decussate - lateral CST controls extremities
10% don’t decussate - ventral CST controls trunk and core muscles
how many pairs of spinal MNs are there
31
what is the pathway of a spinal cord reflex
- stimulus
- afferent pathway
- monosynaptic connection (afferent neuron connects directly to efferent neuron)
- efferent pathway
how long does a spinal cord reflex take
<150 ms
- doesn’t go all the way to the brain
what is a MU made up of
an aMN and the specific muscle fibres that it innervates
- makes up the functional unit of mvmt
what is the difference in ratios between small and large MUs (aMN:muscle fibres)
small = 1:5 - fine mvmt
large = 1:800 - gross mvmt
what are the 3 stages of an AP
- depolarisation (influx of Na+)
- repolarisation (outflux of K+)
- ions return back with Na+/K+ pumps
what does the speed of conduction depend on
unmyelinated vs myelinated
(nociceptors = unmyelinated)
- saltatory conduction on myelinated nerves
what occurs when an AP reaches the NM junction
- presynaptic terminal - AP reaches and releases ACh
- ACh travels across the synaptic cleft
- postsynaptic terminal - AP generates here due to ACh receptors
- synaptic vesicles contain ACh
- AP goes to t-tubule and touches sarcoplasmic reticulum causing Ca2+ release
what is the function of the spinal reflex
used for anything related to maintaining balance quickly
- skating, running on unstable surfaces, etc
what is the all or none principle
all muscle fibres innervated in a MU are stimulated to contract
what is the size principle
anatomic basis for the orderly recruitment of small to large MUs to produce a smooth muscle action
what is recruitment
increasing the number of MUs recruited
- occurs first
what is rate coding
increasing frequency of MUs discharge
- occurs second
what is the order of recruitment and rate coding during exercise
both increase as exercise intensity increases
- recruitment = first
- rate coding = second
what are muscle spindles
fusiform structure embedded in the muscle
- monosynaptic - no interneuron
what do muscle spindles respond to
any stretch of the muscle
- provides mechnosensitive info about changes in muscle fibre lngth and tension
- sends info to spinal cord and sends excitatory info back to the aMNs
what do nuclear bag fibres respond to
phasic stretch (changes in stretch)
what do nuclear chain fibres respond to
static stretch (maintained stretch)
where are GTOs
in the muscle tendon unit
what are GTOs
responds to the tenison created by muscle contraction
(active force production NOT stretching)
- protective sensory mechanism
what do GTOs do
reduces the level of muscle contraction and tension in the muscle
- has an inhibitory interneuron that inhibits the aMN during dangerously high active force production (main difference from muscle spindle)
what is the stretch (myotatic) reflex
involuntary contractions of muscle from a rapid stretch
- only involves afferent and efferent neurons and 1 synapse
- spinal cord only
what is the function of the stretch reflex
helps the body to maintain its balance in a fraction of a second
- tiny adjustments all the time to keep standing
