Lower Motor Neurones and Spinal Reflexes Flashcards
What is a lower motor neurone?
Cells who have cell bodies which collect to form discrete motor nuclei in the brainstem or spinal cord
Describe an A-alpha motor neurone
Large diameter
Myelinated
Where can a alpha neurone’s cell body be found?
Ventral horn of the spinal cord
What is the function of a gamma motor neurone?
Innervate intrafusal muscle fibres to provide constant muscle tone
What is the function of a alpha motor neurone?
Innervate extrafusal muscle fibres to contract muscles
What is a motor unit?
An alpha neurone and the area of muscle it innervates
How can the force of a muscle contraction be controlled?
Vary number of motor unit innervated
Vary number of impulses sent to that motor unit
How can more control of a muscle be gained?
Increase the number of motor units in that area
Why do elderly people have less control and stiffer muscles?
Lose motor units so the existing units become bigger
Atrophy of connective tissue
Describe an S type muscle fibre
Slow contracting
Fatigue resistant
Low force
Describe an FR type muscle fibre
Faster contracting
Fatigue resistant
Low force
Describe a FF type muscle fibre
Fast contracting
Fast fatigue
High force
Poorly vascularised
What is a spinal reflex?
Involuntary, unlearned, automatic, repeatable response to a specific stimuli
Are upper motor neurones involved in a reflex?
No
What is a muscle spindle?
Encapsulated sense organ found in muscles
What is the function of a muscle spindle?
Detects the amount of muscle contraction by monitoring the length of muscle fibres
Which neurones are responsible for innervating the muscle spindles?
Gamma motor neurones
What is the golgi tendon organ?
Organ found in the tendons of muscles responsible for detecting the degree of muscle contraction
What does the golgi tendon organ prevent?
Excessive muscular contractions
They inhibit the antagonistic muscle
What is a postural reflex?
A reflex which keeps the body upright by making small muscle changes
What is a righting reflex?
Helps body respond to a rapid loss of balance
What is a equilibrium reaction?
Affects the body’s centre of gravity
What is a protective reflex?
Reflexive withdrawal of the body from actual or percieved pain
