Exam 4 Flashcards
What are alpha motor neurons?
Neurons that send signals from the spinal cord to muscle fibers, directly triggering muscle contractions
What is a motor unit?
It’s a single alpha motor neuron and all the muscle fibers it controls (A coach and it players)
What is a motor neuron pool?
A group of alpha motor neurons that innervate a single muscle, collectively coordinating its movements (Lots of coaches for one player)
What are the major differences between slow and fast motor units?
Slow Motor Units contract slowly and are more useful for endurance purposes
Fast Motor Units contract quickly producing high force for brief periods
What is Excitation–Contraction Coupling?
It’s the process in which a muscle receives a signal to move and then actually does the movement.
What is the Sarcolemma?
The outer layer or “skin” of a muscle cell. (helps pass the signals into the muscle cell)
What are Myofibrils?
They are tiny fibers in a muscle cell that shorten when a muscle retracts (Made of sarcomeres)
What is the Sarcoplasmic Reticulum?
It’s a specialized form of the endoplasmic reticulum in muscle cells that stores and releases calcium ions
What are T-Tubles?
These are tunnel-like extensions of the sarcolemma that go deep into the muscle fiber. They help transmit electrical signals to all parts of the muscle fiber.
What is a sarcomere?
The sarcomere is the basic contractile unit of muscle.
What is the difference between thick and thin filaments?
Thick filaments: Made of Myosin, Pull the thin filaments to shorten the sarcomere
Thin filaments: Made of the actin, pulled in by the myosin head of the thick filament
What are muscle spindles?
These are sensory receptors within muscles that detect changes in muscle length.
What is proprioception?
This is the body’s ability to sense its position and movement in space.
What is the stretch reflex?
It is a reflex in which if you stretch a muscle too fast the muscle will automatically contract to counteract and prevent injury
What are gamma motor neurons?
These neurons control the sensitivity of muscle spindles. (They ensure that proprioceptive feedback is accurate during muscle contractions)
What is the Golgi Tendon Organ?
Located at the junction of muscles and tendons, they detect tension in the muscle and send signals to the brain when excessive force is detected to prevent muscle damage
What is Reciprocal Inhibition and how does it affect muscle coordination?
This is the process by which muscles on one side of a joint relax to allow muscles on the other side to contract.
What are Central Pattern Generators (CPGs)?
They are neural circuits within the spinal cord that produce rhythmic movements, like walking or breathing, without needing conscious thought.
What are the two main motor pathways?
The Lateral pathway and the Ventromedial pathway
What is the lateral pathway?
A group of nerve pathways in the spinal cord that help control precise, VOLUNTARY movements, especially in the distal areas of the body. (Feet and Hands)
What is the Ventromedial pathway?
Another set of spinal pathways, that controls posture and balance by affecting muscles closer to the body’s center, like those in the back and trunk. (Proximal/Axial)
What is the Corticospinal tract?
A spinal cord pathway that carries movement signals from the brain’s motor cortex to the spinal cord, helping control fine motor movements. (Lateral cortiospinal tract crosses at the medulla)
What is the Rubrospinal tract?
A pathway that starts in the red nucleus of the brain and helps with voluntary control of big muscles (Can act as a backup if the Corticospinal tract is injured)
What is the red nucleus?
A part of the brainstem that acts as a relay center for motor signals, especially those involving movement and coordination of the arms.
What is the Vestibulospinal tract?
A pathway that helps keep balance and posture by sending signals from the inner ear
What is the Tectospinal tract
A pathway that helps coordinate head and neck movements, especially in response to visual or auditory stimuli
What is the Reticular formation?
A network of neurons in the brainstem that plays a role in alertness, but also helps control muscle tone and some reflexes.
What is the Pontine reticulospinal tract? (From the Pons)
It’s part of the reticular formation pathway that helps maintain posture and muscle tone.
What is the Medullary reticulospinal tract? (From the Medulla)
It’s part of the reticular formation pathway that helps relax muscles so movements are smoother.
What is the difference between low motor neurons and upper motor neurons?
LMN: Found in the spinal cord, they receive signals from UMNs and transmit those signals to muscle fibers
UMN: Found in the motor cortex, sends signals to LMNs and
are responsible for initiating and planning voluntary movement
What is the purpose of the Premotor Area (PMA)?
The PMA is involved in planning movements and coordinating movements in response to external cues, like seeing a target to reach for.
What is the purpose of the Supplementary Motor Area (SMA)?
The SMA helps with planning and coordinating more complex sequences of movements, often involving both sides of the body, such as clapping.
What is special about mirror neurons?
They activate both when you perform an action and when you see someone else performing the same action, like grasping an object.
What is the Ventral Lateral Nucleus (VLN)?
A region in the thalamus that relays motor information from the cerebellum and basal ganglia to the motor cortex
What is the striatum?
The input region of the basal ganglia (Made of the Caudate Nucleus and Putamen)
What are the two different pathways Imputs to the striatum can go through?
The direct pathway (The short one) and the indirect pathway.
What are MSNs? What are the two types?
Medium spiny neurons. They are both dopamine receptors where one expresses dopamine D1 receptors and one expresses dopamine D2.
Explain the direct pathway.
Excitatory synapses come into the striatum to target (MSNs)
D1 MSNs are then activated and inhibit Globus Pallidus internal or (GPI) which project to and inhibits the VLN
-NET EXCITATORY
Explain the indirect pathway.
Excitatory synapses come into the striatum to target (MSNs)
D2 MSNs are then activated and inhibit Globus Pallidus external which inhibits Globus Pallidus internal which project to and inhibits the VLN (Can also use the Subthalamic Nucleus)
-NET INHIBITORY
What structure in the basal ganglia helps decide which pathway dominates and plays a significant role in learning?
The “Substantia Nigra pars compacta” are dopamine neurons that synapse at all portions of the striatum to release dopamine onto MSNs (Excites the D1 neurons, inhibits the D2 neurons)
What is different about the eye movement pathway of the basal ganglia?
The pathway is identical until it replaces the VLN with the Substantia Nigra pars reticulata which then affects eye movements through the superior colliculus
What is Parkinson’s disease?
A neurodegenerative disorder due to the loss of dopamine-producing cells in the substantia nigra.
What are common symptoms of damage to upper motor neurons?
-Loss of voluntary movement (Retention of reflexes)
-Increased reflexes
-Clonus/hypertonia (Rhythmic, repetitive muscle contractions)
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What are common symptoms of damage to lower motor neurons?
-Flaccid paralysis
-Decreased reflexes
-Severe muscle atrophy (due to not using them)
