NEU Quiz Movement Flashcards
Categories of Movement
Reflex → involuntary reside in spinal cord, can be complex and modified by signals from brain
Rhythmic → include patterns elicited pattern generators → locomotion, chewing, swallowing, breathing → control from brain
Voluntary → movements initiated to accomplish a specific goal
Motor Nerves
Peripheral nerves - mixed sensory and motor axons (mix of sensory sending signals towards spinal cord and motor axons sending signals to muscles)
Split into dorsal and ventral roots → Roots enter dorsal horns and exit ventral horns
Ventral ROOTS = Lower motor neurons
Neurons between ventral horn and cortex = Upper motor neurons
Organization from largest to smallest:
Muscle, Fascicles (nerve), Muscle Fibers (CELLS) Myofibrils, Sarcomeres, Myofilaments
Epimysium (connective tissue):
helps muscle maintain structural integrity while contracting also separate muscles from other tissues and organs in that area
Sarcolemma:
contains sarcoplasm which is the cytoplasm of the muscle cell
Anatomy of a Skeletal Muscle Fiber:
- Cylindrical cell
- Multiple nuclei
- Sarcolemma (plasma membrane)
- Organelles:
- Myofibrils (actin and myosin)
- Sarcoplasmic reticulum (type of smooth ER, Stores Ca2+, has voltage gated Ca2+ channels)
- T tubules (link SR to Sarcolemma, helps carry action potential to SR to release Ca2+)
- Mitochondria
Muscle Fiber Organelles Myofibrils:
SHORTEN for muscle contraction and contain sarcomeres(contractile units which is smallest contractile unit of muscle fiber AND during contraction each sarcomere along a myofibril shortens to shorten the entire myofibril) Sarcomeres contain myofilaments: Actin – thin filaments and Myosin – thick filaments (6 subunits two heavy and four light subunits; breaks down ATP for muscle contraction)
Myofibrils - basic contractile element of muscle. Bundled into muscle fibers with a contractile subunit called sarcomere. Sarcomere are made of actin and myosin protein filaments. The sarcomeres shorten when myosin hydrolyzes ATP and slides along the actin. Hydrolysis of ATP causes myosin and actin filaments to slide past one another. Sarcomeres shorten and muscle contracts. Sarcomeres are made of actin and myosin protein filaments also called a myocyte. The sarcomeres shorten when myosin hydrolyzes ATP and slides along the actin. Sliding filament is during contraction, thin filaments slide past thick filaments actin and myosin overlap more and occur when myosin heads bind to actin.
AP happen from end plate potential to an AP and between then we reach threshold and the same VG the Na depo and K+ repo just liek normal neuron what differs is what happens next. After AP sent in muscle cell it travels to sacorrlmmea once travleign have the AP travels to the T-tubles which link the sacrollema to teh scaroplamic reticulm. Here there are VG calcium channels and so AP traveling being transferred opens the VG Ca channels which is conceratred in teh retiucilm and Ca wants to leave th sacroplaimu reticulum bc of its concentration gradient. Ca being released acatavates our contrction this Ca is able to attach to actin and moves/activates troponin which moves tropomyosin off of the mysoin binding sites and allows mysoin to attach to actin and mysoin plulss myoisn towards each other inorder to shorten the sarcomere. Shorten sacromeres in one muscle fiber.
Actin myofilaments
Myosin myofilaments
Actin myofilaments = thin filaments, site where myosin attaches, Tropomyosin – covers myosin binding site, Troponin holds tropomyosin in place over myosin binding site on actin
Myosin myofilaments = thick filaments, head of myosin has binding sites for actin binding sites for ATP, ATPase enzymes – break down ATP
How Does Contraction Happen?
- Excitation (at neuromuscular junction) * Must be nerve stimulation * Must generate action potential – change in voltage at sarcolemma
- Excitation-contraction coupling * Action potential moved along sarcolemma to T-tubule * Ca2+ released from SR and binds actin * Myosin binds to actin and sarcomeres shorten
The Nerve Stimulus:
- Skeletal muscles stimulated by somatic motor neurons
- Axons travel from spinal cord to skeletal muscle
- Each axon forms several branches as it enters muscle
- Each axon terminal forms neuromuscular junction with single muscle fiber
Neuromuscular Junction (NMJ):
- Axon terminal of a neuron and muscle fiber separated by space (synaptic cleft)
- Vesicles of axon terminal contain acetylcholine (ACh)
- Sarcolemma contains ACh receptors
- NMJ includes axon terminals, synaptic cleft, junctional folds
Generation of an Action Potential STEP 1
AP sent by LMN(lower motor neuron) so VG Ca channels open in axon terminal and Ach release at NMJ)
- Generate End plate potential (local depolarization)
- ACh binding opens ligand gated ion channels
- diffusion of Na+ into cell through ionotropic Ach receptors
- Local depolarization in the region of the ACh receptor = end plate potential(EPSP called end plate potential once threshold reached and AP sent in muscle fiber)
Events in Generation of an Action Potential STEP 2
- Depolarization - generation and propagation of an action potential (AP)
- End plate potential spreads
- Voltage-gated Na+ channels open(further depolarizing)
- Na+ influx decreases membrane voltage
- If threshold voltage reached, AP initiated(-55mv)
- Once initiated, is unstoppable muscle fiber contraction(all or none once AP start)
Events in Generation of an Action Potential STEP 3
Repolarization - REFRACTORY PERIOD
* Na+ channels close
* K+ channels open
* Restores the resting(normal) membrane potential(Na/K ATPase)
Destruction of Acetylcholine:
- ACh effects quickly terminated by enzyme acetylcholinesterase in synaptic cleft
- Breaks down ACh
- Prevents continued muscle fiber contraction – turns off end plate potential
Excitation-Contraction (E-C) Coupling:
Events that transmit AP along sarcolemma lead to sliding of myofilaments - AP propagated along sarcolemma to T tubules - Voltage gated Ca2+ channels open on SR - Ca2+ attaches to actin, revealing binding sites for myosin
Phase 1 Motor neuron stimulates muscle fiber: Action potential (AP) arrives at axon terminal at neuromuscular junction - ACh released; binds to receptors on sarcolemma - Ion permeability of sarcolemma changes - Local change in membrane voltage (depolarization) occurs - Local depolarization (end plate potential) ignites AP in sarcolemma
Phase 2: Excitation-contraction coupling occurs: AP travels across the entire sarcolemma - AP travels along T tubules - SR releases Ca2+; Ca2+ binds to troponin; myosin-binding sites (active sites) on actin exposed - Myosin heads bind to actin; contraction begins
Motor Pathways: Motor Unit
Each muscle served by at least one motor nerve - Neuron axons branch into terminals - Each branch forms NMJ with single muscle fiber - ACh is the NT - Myelination is important
Motor unit = motor neuron and all muscle fibers it supplies - Smaller number of fibers/neuron = fine control - Recruit more motor units = stronger contraction
Cerebral Motor Control:
Primary motor cortex (M1) controls voluntary movement (Frontal lobe)
Motor map – each part represented in space as it is on body - Size of area = complexity of movement
Signals descend from M1 to spinal cord - Corticospinal pyramidal tract (UMN) - Decussation(crossing over) – pyramids of medulla - Synapse on LMN at ventral horns
Control of Motor Movement Basal Ganglia, Thalamus and Motor areas:
1) Direct pathway: a. leads to movement
2) Indirect pathway: a. inhibits movement
3) Dopamine can modulate
Dysfunction (death of dopamine neurons in the substantia nigra) leads to Parkinson’s Disease
M1 sends “copies” of motor movement signals to cerebellum and Cerebellum feeds back to M1 to smooth and balance commanded movement corrects motor errors!
Spinal Reflexes:
Reflex – involuntary response to specific stimulus (Ex: Flexor and Stretch reflex). Generally work via SPINAL CORD and Requires integration of sensory and motor information. Reflex Arc (sensory) - Primary afferents synapse on interneuron - Interneuron synapses on motor neuron
The Flexor Reflex:
Flexor (withdrawal) reflex is Initiated by painful stimulus and Causes automatic withdrawal of threatened body parts. Is Ipsilateral and Brain can override.
The Stretch Reflex:
Maintains posture and adjusts and Requires proprioception – sensation of limb position. Special sensory muscle fibers - Muscle spindles - Sensory neurons wrapped around deep muscle fibers.
Stretch detected: Causes muscle contraction response. Ipsilateral
How stretch reflex works:
Stretch activates muscle spindle afferents - Spindle afferents synapse directly with motor neurons - Motor neurons cause stretched muscle to contract - Reciprocal inhibition also occurs
Example: Patellar reflex
The correct order for the largest to smallest unit of organization in
muscle tissue is:
a.Fascicles, myofibrils, muscle, muscle fibers, sarcomeres, myofilaments
b.Muscle, fascicles, muscle fibers, myofibrils, sarcomeres, myofilaments
c.Muscle, muscle fibers, fascicles, myofilaments, sarcomeres, myofibrils
d.Muscle, fascicles, muscle fibers, myofilaments, sarcomeres, myofibrils
b.Muscle, fascicles, muscle fibers, myofibrils, sarcomeres, myofilaments
Which ions bind to troponin to move tropomyosin away from actin, so that myosin can bind and the muscle can contract?
a.Fluorine ions
b.Potassium ions
c.Calcium ions
d.Sodium ions
c.Calcium ions
What role does the sarcoplasmic reticulum (SR) play in muscle contraction?
a.SR stores and releases calcium, which is released upon depolarization
b.SR stores and releases potassium, which is released upon depolarization
c.SR releases acetylcholine to depolarize the muscle cell
d.SR contains the myofilaments actin and myosin, which overlap to contract
a. SR stores and releases calcium, which is released upon depolarization
Which of the following must occur to signal a muscle contraction?
a.ADP must be produced
b.Sodium ions must bind to troponin
c.The sarcoplasmic reticulum must release acetylcholine
d.An action potential must reach a muscle cell
d.An action potential must reach a muscle cell
Which neurotransmitter is released at the Neuromuscular
Junction?
a.Glutamate
b.Acetylcholine
c.GABA
d.Serotonin
e.Substance P
b.Acetylcholine
Ava notices that when she consumes two alcoholic beverages within an
hour she has trouble controlling her movements. She stumbles occasionally
and may knock over a glass that she intended to pick up. She doesn’t have any trouble initiating movement, but all of her movements seem a little “off” and she’s making lots of motor mistakes. Which motor system is most
affected by Ava’s alcohol consumption?
a.Lower motor neurons
b.Upper motor neurons
c.Both lower and upper motor neurons
d.Cerebellum
e.Basal ganglia
d.Cerebellum
Upper motor neurons
a.control the upper half of the torso.
b.synapse on muscles in the eye, neck, and head.
c.synapse on lower motor neurons.
d.affect motor patterns only indirectly via their inputs to the basal ganglia.
e.have cell bodies that are located in the ventral horn of the spinal cord.
c.synapse on lower motor neurons.
A motor pool (as opposed to a motor unit) consists of:
a.all of the motor units that project to a given muscle.
b.all of the motor units within a single segment of spinal cord.
c.all of the motor units that project to a given limb.
d.a single motor neuron and all of the muscles it innervates.
e.a single motor neuron and all of its afferent interneurons
a.all of the motor units that project to a given muscle.
What is an end plate potential?
a.This is what an action potential in a muscle cell is called
b.A local depolarization of the muscle cell
c.Hyperpolarization of the muscle cell
d.The resting membrane potential of a muscle cell
b.A local depolarization of the muscle cell
At which level of the nervous system does the
corticospinal pyramidal tract decussation occur?
a.Cerebral cortex
b.Midbrain
c.Pons
d.Medulla
e.Spinal cord
d.Medulla
Muscle fibers are
cylindrical cell
What is motor pool?
bla
map
fucntion and complexity
