RUSVM Physio Neuro Part 8 Motor System and Reflex Arch Flashcards
What is the spinal cord protected by
The Vertebral column
The spinal cord is anatomically divided into what
Peripheral white matter and central grey matter
Dorsal root (horn) of the grey matter is related to what system?
The sensory NS
The ventral root (horn) of the grey matter is related to what system
The motor NS
What are the 5 fundamental components of the arc reflex (Learning objective)
- A receptor
- A sensory neuron
- One or more synapses in the CNS
- A motor neuron
- a target organ
What is called a reflex in which the reflex arc passes through only a small segment of the spinal cord or a small rostrocaudal region of the brainstem
ex= stretch reflex or pupillary reflex.
Segmental reflex
What is called the reflex arc that transverses many segments of the spinal cord or several major brain divisions
Intersegmental reflex
What are the two main components of the motor system
Upper Motor Neuron (UMN) and Lower Motor Neuron (LMN)
What are the two types of muscle fibers of the motor neurons
Extrafusal fibers and intrafusal fibers
Extrafusal fibers are innervated for what neurons
The Alpha Motor Neurons (give rise to A alpha fibers)
Intrafusal fibers are innervated by what neurons
by Gamma motor neurons (give rise to alpha gamma fibers)
What two important muscle receptors provide the CNS with information
Muscle spindle and Golgi tendon organ.
Posture and movement depend on a combination of what
Voluntary actions controlled by higher brain centers and involuntary reflexes coordinated by the spinal cord.
What is defined as a single motorneuron and the muscle fibers that it innervates
A motor unit
T/F Each motor unit has a unique contractile force determined by the number of muscle fibers it innervates
TRUE
T/F The muscle spindle middle part is innervated by sensory neurons and carry action potentials from the spindle to the CNS
True
T/F the contractile part of the muscle spindle is not innervated by gamma motor neurons
False- they are innervated by gamma motor neurons
What are the motor systems 3 main functions (Learning objective)
- Maintain posture and provide a stable platform for movement (somatic)
- Controls vol. movement and locomotion (somatic)
- Controls visceral motor function (Visceral)
Describe Upper Motor Neuron (UMN) (learning objective)
- Completely contained in the CNS (aka central motor neuron)
- Cell body is located in a motor nucleus of the brain stem or the motor cortex of the forebrain
- THEIR AXONS CONNECT TO LOWER MOTOR NEURONS (either synapsing on them directly or indirectly via interneurons) INTERNEURONS ARE BIPOLAR 1 AXON 1 DENDRITE AND THEY INTERCONNECT VARIOUS NEURONS W/ BRAIN AND SPINAL CORD.
- Organize and direct the activity of LMN’s
Describe Lower Motor Neurons (LMN) (learning objective)
- They have their cell body in the CNS (brain or spinal cord)
- Their axons project into the PNS via cranial or spinal nerves.
- AKA peripheral neurons
- Autonomous NS have 2 LMN’s in series with the cell body of the second LMN located in a peripheral ganglion
- When stimulated LMNs induce muscle contraction
What is an encapsulated group about 3 to 12 small, slender, specialized skeletal muscle fibers.
Muscle Spindle
The contractile part of muscle spindles are innervated by what
Gamma Motor neurons
What is the purpose of a muscle spindle
Are stretch receptors whose function is to correct for changes in muscle length
How are action potentials generated along the spindle sensory neurons
Stretching the middle segment of the intrafusal muscle fibers generate AP’s along the spindle sensory neurons
