Exam 1 Part 3 Nerve supply to skeletal muscle Flashcards
Each muscle is provided with a _____ ____ ___ and a _______ _____ _____
Motor nerve fiber and a sensory nerve fiber
Motor nerves transmit:
Efferent/ Motor impulses from the CNS to each individual muscle fiber, the result of which is a motor response (contraction)
The single motor neuron (nerve fiber) and the group of muscle fibers is supplies is known as the ____ ___
Motor unit
The ____ ___ is the smallest part of the muscle which can contract independently
Motor unit
Muscles that carry out precision type of activities contain motor units with:
fewer number of fibers
Muscles that carry out non precision type of activities have motor units which can consist of:
thousands of motor fibers
Originates in a motor neuron in the ventral horn of the grey matter of the spinal cord
- Continues as the spinal nerves and named peripheral nerves
- The neuromuscular junction
- the sarcolemma of the muscle fiber (terminal end of the unit)
Anatomical parts of the motor unit
Physiologically, biochemically and clinically complex portion of the motor unit
Neuromuscular junction
Parts of the neuromuscular junction
- Presynaptic portion
- Postsynaptic portion
- Synaptic cleft
The nerve ending
Presynaptic portion
Sarcolemma of the muscle fiber
Postsynaptic portion
Space b/t the pre and post synaptic portions
Synaptic cleft
- Most common neuromuscular junction disorder (autoimmune disorder)
- Produces abnormal antibodies which destroy the ACH receptor sites on the sarcolemma of the muscle fibers
- Inherited disorder
- Starts by affecting the muscles supplied by the cranial nerves and may progress to muscles of the extremities
Myasthenia Gravis
Patients will suffer from hyperplasia of the _____ _____ or a tumor of the gland
Thymus gland
- Example of a drug that is able to complete with ACH molecules in the binding to the ACH receptor sites
- However, its actions are much more prolonged than ACH
Nicotine
- Contains both cytotoxins and neurotoxins
- Prevents ACH from binding to the ACH receptor sites
- Do not cause an action potential to occur
Snake venom
Ex. include parathion and malathion, which are found in insecticides and are able to inactivate the ACHe
- ACH can no longer be rapidly degraded, resulting in an accumulation of ACH at the postsynaptic portion of the junction
Organophosphates
Botulin Toxin is the toxin that is released from the bacteria known as _______ ______, which causes a severe type of food poisoning known as botulism
Clostridium botulinum
Toxin blocks the release of ACH from the ________ portion of the neuromuscular junction
Botulin Toxin
Usually first affects the muscles supplied by the cranial nerves but can progress to affect limb and respiratory muscles
Botulin Toxin
Sensory nerve fibers convey to the CNS _______/_______ impulses which originate within the muscle as a result of a contraction
Afferent/ Sensory
In addition to coordination of muscle function, sensory nerve fibers are also involved with:
- Pain
- Proprioception
Are a category of sense organs that are found within the musculo-skeletal system
Proprioceptors
_____ _____ are an example of proprioceptors found scattered throughout a muscle and are fluid filled sacs.
Muscles spindles
Muscle spindles contain specialized muscle fibers known as ______ & ______ muscle fibers
Intrafusal & Extrafusal muscle fibers
Have both efferent and afferent nerve fibers associated with them.
Intrafusal muscle fibers
Have ONLY efferent nerve fibers associated with them
Extrafusal muscle fibers
Muscle spindles and their ________ muscle fibers detect stretch in a muscle
Intrafusal
_____ _____ ______ are located in tendons and detect stretch of the tendons, which triggers a reflex which inhibits muscle contractions to avoid injury to the muscle and it tendon
Golgi tendon organs
