Mucle contraction Flashcards
What are the two pathways to control muscle innervation?
Somatic motor, autonomic (sympathetic and parasympathetic)
How does the somatic motor system work?
Signals from CNS down somatic motor fibre in peripheral NS, directly synapses to skeletal muscle
What is the sympathetic pathway?
Chain of sympathetic ganglion- preganglionic neurons release acetylcholine, postganglionic neurons release noradrenaline
Participates in fight or flight response so neurons close to target
What is the effect of noradrenaline binding to different postsynaptic adrenoreceptors?
Relaxes airway in lungs
Inhibits digestion
Accelerates heart rate
What is adrenaline used for in a clinical setting?
Cardiac arrest- increases peripheral resistance and accelerates heart rate
What is the parasympathetic pathway?
Long range projections, release acetylcholine
Compliments sympathetic nervous system by acting as brake
Controls actions that don’t need an immediate reaction- digestion, metabolic functions, regulating kidneys
What is the effect of acetylcholine binding to different postsynaptic receptors?
Constriction of airways
Stimulates digestion
Slows heart rate
What is the somatic motor system?
To innervate and command all skeletal muscles in the body (coordinate), under voluntary control and generates behaviour- talking, facial expression, eye movements
What is involved in the somatic motor system?
Motor cortex region of brain chooses movement, patterns of motor commands, descend into spinal cord synapse with upper motor neurons and then lower motor neurons- projections to muscles
What are lower motor neurons?
Directly command muscle contraction
Skeletal muscle movements initiated by LMN
Activated by local spinal cord circuits
Each motor neuron innervates a single muscle
How are lower motor neurons organised?
Distributed within the ventral horn in a predictable way
Spatial map of body musculature
Neurons innervating axial muscle are medial to neurons innervating distal muscle
Neurons innervating flexor muscles are dorsal to those innervating extensor muscles
What is an alpha motor neuron?
Directly trigger the generation of force by muscles
What is a single motor neuron?
Synapses with many muscle fibres to ensure the spread of contractile force is even
What is a motor unit?
An alpha motor neuron and all the muscle fibres it innervates
What is a motor neuron pool?
Collection of alpha motor neurons that innervate a single muscle, arrangement maintain normal muscle activity when damage to a single motor neuron occurs
