Neuromuscular Muscle System Flashcards
What are the four big picture functions of the nervous system?
- Control of internal environment
- voluntary control of movement
- spinal cord reflexes
- assimilation of experiences necessary for memory and learning
The nervous system is organized into what two parts?
central nervous system (CNS) and peripheral nervous system (PNS)
The central nervous system (CNS) primarily consists of:
brain and spinal cord
What are the two divisions of the peripheral nervous system?
sensory division (incoming) and motor division (outgoing)
which division of the peripheral nervous system uses afferent fibers to transmit impulses from receptors to CNS?
sensory division (incoming)
which division of the peripheral nervous system uses efferent fibers to transmit impulses from CNS to effector organs?
motor division (outgoing)
in the motor division of the PNS, which nervous system is voluntary to skeletal muscles and which is involuntary?
somatic: voluntary, to skeletal muscles
autonomic: involuntary
What is somatic sensory?
sensory input that is consciously perceived from receptors (e.g., eyes, ears, skin)
What is visceral sensory?
sensory input that is not consciously perceived from receptors of blood vessels and internal organs (e.g., heart)
The somatic and visceral sensory systems are a part of which nervous system?
sensory nervous system
What does the sensory nervous system do?
detects stimuli and transmits information from receptors to the CNS
What is somatic motor?
motor output that is consciously or voluntarily controlled; effector is skeletal muscle
what is autonomic motor?
motor output that is not consciously or is involuntarily controlled; effectors are cardiac muscle, smooth muscle, and glands
somatic motor and autonomic motor are part of which nervous system?
motor nervous system
what does the motor nervous system do?
initiates and transmits information from the CNS to effectors
What is the basic functional unit of the nervous system?
neuron
What are the three primary regions of a neuron?
cell body (soma
dendrites
axon
What structure in the neuron contains the nucleus?
cell body
What structure in the neuron conducts impulses toward the cell body?
dendrites
What structure in the neuron carries electrical impulses away from the cell body?
axon
Axons may be covered by what?
schwann cells
What structure of a neuron has end branches, terminal, and neurotransmitters?
axon
The ability of a neuron to respond to a stimulus and trigger a neural impulse is called:
irritability
the ability of a neuron to transmit the impulse along the axon is called:
conductivity
What is a nerve impulse?
electrical signal which enables communication between periphery and brain
What three things must happen for a nerve impulse to occur?
- must be generated by a stimulus
- must be propagated down an axon
- must be transmitted to next cell in line
What are two types of synaptic transmission?
neuron - synapse - neuron
neuron - synapse - muscle
What is the resting potential of a cell membrane?
-70 mV
Why is the resting potential of a cell membrane -70 mV?
- Difference in ion concentrations across membrane
- high concentration of Na+ outside
- medium concentration of K+ inside
- inside more negative relative to outside
How does the cell membrane maintain its resting potential?
- cell membrane more permeable to K+ than Na+
- Na+ - K+ ATPase pumps
How many K+ and Na+ are moved in the Na+/K+ ATPase pumps?
2 K+ in and 3 Na+ out
Depolarization occurs when:
a stimulus of sufficient strength depolarizes the neuron
What happens to Na+ during depolarization?
Na+ channels open and Na+ diffuses into the cell (inside becomes more positive 70mV > 0mV)
What is repolarization?
returns to resting membrane potential
What happens to K+ and Na+ during repolarization?
K+ leaves the cell rapidly, Na+ channels close
What is the All-or-none principle?
once a nerve impulse is initiated, it will travel the length of the neuron
What is a synapse?
small gap between presynaptic neuron and postsynaptic neuron
What are the two types of postsynaptic potential?
excitatory (EPSP) and Inhibitory (IPSP)
What is a neurotransmitter?
chemical messenger released from presynaptic membrane
What does a neurotransmitter bind to?
receptor on a postsynaptic membrane, then causing depolarization of postsynaptic membrane
What is a motor unit?
alpha-motor neuron and all of the muscle fibers it innervates
What does the neuromuscular junction do?
allows the neuron and muscle fiber to communicate
synapse: allows for the communication of electrical and chemical signals
The synapse initiates:
muscle action
What is the most basic functional unit?
motor unit
The site of neuron-to-muscle communication uses what neurotransmitter?
acetylcholine (ACh)
A postsynaptic cell is equivalent to:
muscle fiber
What happens at a postsynaptic cell?
ACh binds to receptor at motor end plate which causes depolarization. AP moves along plasmalemma, down T-tubules. Undergoes repolarization, refractory period
What comes in to push NTs out to receptors in order to start depolarization?
calcium
what is the basic function of t-tubules?
carry signal deep into the muscle
When does the signal stop?
when enough NTs have broken off of their receptors
What triggers graded potentials on a new cell (neuron/muscle)?
neurotransmitters
What serves as an excitatory signal in muscle cells?
ACh
Where can ACh be inhibatory?
heart
Is Norepinephrine excitatory or inhibitory?
can be either depending on the tissue
What NT mediates sympathetic nervous system effects?
NE
After the signal is transmitted, what happens to NTs?
degraded by enzymes, transported back into presynaptic terminal, or diffused away from synapse
How is ACh made?
by metabolizing Acetyl-CoA
What are the changes endurance and strength training can make to the NMJ?
- increase size of the NMJ
- increase the number of synaptic vesicles (NT ACh)
- increase number of ACh receptors on post-synaptic membrane
What does increasing the size of the NMJ do?
makes it easier to start electrical signal on muscle membrane
What does increasing number of synaptic vesicles do?
allows for enough reserves to keep pushing ACh and keep process happening
What does increasing number of ACh receptors do?
allows for more binding sites
Are the changes endurance and strength training makes to NMJ chronic or acute?
chronic
Where are motor units located?
spinal cord
What is an innervation ratio?
number of muscle fibers per motor neuron
Do muscles involved in fine motor control have a high or low innervation ratio?
low, 23:1 in extraocular muscles
Do muscles that do not require fine motor control have a high or low innervation ratio?
high, 1,000:1 or greater in large limb muscles
What is the size principle?
motor neurons with the smallest innervation ratios are recruited first
- less stimulation required
- slow twitch fibers
Explain the size principle in your own words:
starts with the smallest innervation ratio and then goes up to the largest depending on how much is needed to complete the action. Brings on fast muscle fibers if small innervation and slow muscle fibers cannot lift something
What are the three types of motor units?
- Type S (slow) or type one fibers (smallest)
- Type FR (fast, fatigue resistant) or type two A fibers (intermediate)
- Type FF (fast, fatigable) or type two X fibers (largest)
What is the recruitment pattern of motor units during incremental exercise?
Type S > Type FR > Type FF
Type FF:
- largest innervation ratios
- most force producing
- fastest fatigue
What are proprioceptors?
Receptors that provide CNS with information about body position
Where are proprioceptors located?
joints and muscles
What is Kinesthesia?
Conscious recognition of the position of body parts; recognition of speed of limb movement
Proprioceptors:
- general nerve receptors
- imbedded in or around joints and muscles
- tells us where our body is in space so brain and eyes don’t have to look to know where the body is
- always sending info about body position to brain
Kinesthesia:
- fear of movement after injury: kinesiophobia
- brains ability to take sensory info and say where the body is
- important to address after injury
- people with best kinesthesia are dancers, gymnasts, figure skaters
Free Nerve Endings:
- most abundant type of joint proprioceptors
- sensitive to touch and pressure
- initially strongly stimulated, then adapt
- embedded in joint
- tells brain about joint in terms of external/internal pressure
- if you wear a necklace/bracelet everyday you forget its there
- receptors are still being stimulated but brain says its okay to ignore
golgi-type receptors:
- found in ligaments and around joints
- functionally similar to free nerve endings
- tells mostly about pressure and movement
Pacinian corpuscles:
- located in tissues around joints
- detect rate of joint rotation
- limited after injury (especially ACL)
- body will start to reinnervate new tissue 2 years later
- for awhile, person is bad at detecting where their knee is in space
What are the 4 functions of muscle?
- joint stabilization
- heat
- posture
- movement
Describe the five steps involved in the sensory-motor integration
- stimulus sensed by sensory receptor
- sensory AP sent on sensory neurons to CNS
- CNS interprets sensory information, sends out response
- motor AP sent out on alpha motor neurons
- arrives at skeletal muscle, and response occurs
What do the two primary proprioceptors provide sensory feedback to nervous system about?
- changes in muscle length
- force development by muscle fibers
What does a muscle spindle provide information about?
muscle length and rate of shortening; tells brain if muscle needs to change size and if so, which way and how quickly
What does a golgi tendon organ provide information about?
muscle force production
Muscle proprioceptors are used to protect the muscle system from:
damage
A muscle spindle is made up of:
- intrafusal fibers
- gamma motor neurons
In fine motor muscles, what amount of muscle spindles is present?
high density
Gamma motor neurons:
- innervate muscle spindle
- reset or change length of muscle spindle
When quad detects muscle spindles are stretching, what happens and what occurs as a result?
it gives you extra power to jump higher which is why you can jump higher with a CMJ than a SJ
What are the steps of muscle spindle innervation?
- muscle spindles detect stretch of the muscle
- sensory neurons conduct action potentials to the spinal cord
- sensory neurons synapse with alpha motor neurons
- stimulation of the alpha motor neurons causes the muscle to contract and resist being stretched
Where is the Golgi Tendon Organ located?
within the muscle tendon at tendinous junction
Can the Golgi Tendon Organ (GTO) prevent muscle injury?
yes, during excessive force generation by monitoring force development in muscle
What does stimulation of the GTO result in?
reflex relaxation of the muscle, inhibitory neurons send IPSPs to muscle alpha motor neurons
What are the steps of the GTO at work?
- golgi tendon organs detect tension applied to a tendon
- sensory neurons conduct action potentials to the spinal cord
- sensory neurons synapse with inhibitory interneurons that synapse with alpha motor neurons
- inhibition of the alpha motor neurons causes muscle relaxation, relieving the tension applied to the tendon
GTO is used during what kind of stretching?
PNF to increase ROM
The Central Nervous System consists of:
brain (cerebrum, cerebellum, brain stem) and spinal cord
What does the cerebral cortex do?
- organization of complex movement
- storage of learned experiences
- reception of sensory information
Where does all sensory information go to?
cerebrum
What is Central Fatigue in the Central Governor Theory?
- fatigue due to neuronal dysfunction within higher brain centers and/or motor neurons
- dysfunction may be due to depletion of excitatory neurotransmitters in the motor cortex resulting in reduced motor output to muscle
What is the Central Governor Theory?
- central control center regulates exercise performance
- reduces motor output to exercising muscle
- protects against catastrophic disruptions of homeostasis
Research suggests that fatigue may be due to:
both central and peripheral factors
What is the MOI for a sports-related TBI?
- forceful blow to the head
- indirect trauma (i.e. car accident)
TBI’s are classified by amount of damage to brain tissue
- concussion is a “mild” TBI - typically resolves within a few days
- may or may not involve loss of consciousness
Concussions can cause:
permanent brain damage or death due to brain swelling
- second impact syndrome
- same season repeat concussion
- late-life consequences of repeated concussions
What does the cerebellum do?
coordinates and monitors complex movement by incorporating feedback from proprioceptors
Cerebellum is connected to:
- motor cortex
- brain stem
- spinal cord
Cerebellum can initiate:
fast movements
The brain stem is the information relay between:
brain and spinal cord
What are the major structures of the brain stem?
- medulla
- pons
- midbrain
- reticular formation
What is the brain stem responsible for?
- cardiorespiratory control
- many metabolic functions
- complex reflexes
The brain stem is crucial for maintaining:
normal upright posture
The spinal cord is continuous with:
the medulla oblongata
In the spinal cord, tracts of nerve fibers permit:
two-way conduction of nerve impulses
What are the two-way conduction of nerve impulses?
- ascending afferent (sensory) fibers
- descending efferent (motor) fibers
What is the pathway of sensory (afferent) fibers in the PNS?
sensory (afferent) > info > periphery to brain
What is part of the sensory (afferent) fibers of the PNS?
vessels, organs, senses, muscle/tendons
What kinds of receptors are associated with sensory (afferent) fibers in the PNS?
mechano- thermo- noci- photo- chemo-
what kind of exercise is associated with the sensory (afferent) fibers of the PNS?
- kinesthetic (joint angles, position, movement)
- muscle spindles (muscle length/stretch)
- golgi tendon organs (tension in tendon, strength of contraction)
What is the Motor (efferent) fiber pathway in the PNS?
motor (efferent) > info > brain to periphery
Motor (efferent) autonomic in PNS:
controls involuntary internal functions (e.g. HR, BP)
Motor (efferent) somatic in PNS:
provides instructions to muscles
Skeletal muscle chemoreceptors are sensitive to changes in:
the chemical environment surrounding muscle fibers
- H+ ions, CO2, and K+
Skeletal muscle chemoreceptors provide information about:
muscle metabolism during exercise; important in control of cardiovascular and pulmonary responses to exercise
Motor Division: autonomic nervous system controls:
involuntary internal functions
Exercise-related autonomic regulation in motor division of ANS
- HR, BP
- lung function
Two complementary divisions of the motor division ANS:
- sympathetic nervous system
- parasympathetic nervous system
During exercise, activity of the parasympathetic nervous system ___ and sympathetic ___
decreases, increases
Sensory-Motor integration:
communication and interaction between sensory and motor systems
What are the five sequential steps of Sensory-Motor Integration?
- stimulus sensed by sensory receptor
- sensory AP sent on sensory neurons to CNS
- CNS interprets sensory information, sends out response
- motor AP sent out on alpha motor neurons
- arrives at skeletal muscle, and response occur
Sensory-Motor Integration reflex activity:
- motor reflex
- instant, preprogrammed response to stimulus
- response to stimulus identical each time
- before conscious awareness
- fastest mode of response
Withdrawal Reflex: crosses extensor reflex:
- during the withdrawal reflex, sensory neurons from pain receptors conduct action potentials to the spinal cord
- sensory neurons synapse with excitatory interneurons that are part of the withdrawal reflex
- the excitatory interneurons that are part of the withdrawal reflex stimulate alpha motor neurons that innervate flexor muscles, causing withdrawal of the limb from the painful stimulus
Control of voluntary movement:
involves cooperation of many areas of brain along with subcortical areas
- motor cortex receives input from variety of brain areas including basal nuclei, cerebellum, thalamus
- spinal mechanisms (that is spinal tuning) results in refinement of motor control
- feedback from proprioceptors allows for further modification in motor control
Exercise training enhances:
brain health
regular exercise can protect the brain against:
- disease (alzheimer’s)
- certain types of brain injury (stroke)
How does exercise enhance brain health?
- enhances learning and memory
- stimulates formation of new neurons
- improves brain vascular function and blood flow
- attenuates mechanisms of driving depression
- reduces peripheral factors for cognitive decline
- inflammation, hypertension, and insulin resistance
