Reflex Movement Flashcards
What are the different types of movements
Involuntary actions - reflexes
Semi-automatic actions
Voluntary actions
Describe involuntary actions
No conscious element - involuntary Centred on: - Spinal cord (spinal nerves) Brainstem (cranial nerves) Stereotyped response Monosynaptic circuit Rapid, short latency (delay)
How many synapses do reflex arcs have
1 central synapse so its a monosynaptic arc
How is matter arranged in the spinal cord
Central grey matter surrounded by white matter
What are the components of a reflex pathway
Stimulus Receptor Afferent (sensory neurone) Synapse(s) Efferent (motor) neuron Effector (muscle, gland) Response
Why is the intermediate horn important
Important for the thoracic and lumbar regions as this is the main source of output for sympathetic nervous system
Describe the interneurone
Isn’t always necessary
Can recruit motor neurones
Path is slower as the pathway isn’t monosynaptic
Give examples of somatic reflex receptors in the tendon jerk reflex
Proprioceptor endings
Group 1a muscle afferents
Homonymous motor neurons
Give examples of somatic reflex receptors in cutaneous reflexes
Mechanoreceptor endings
Nociceptor endings
Give examples of some other somatic reflex receptors
Chemoreceptors
Photoreceptors
Describe the ankle jerk reflex
Hammer tap to Achilles’ tendon stretches spindles within gastrocnemius
Action potentials conducted along 1a muscle afferents to spinal cord
Monosynaptic activation of motor neurons of gastrocnemius muscle
APs travel along Aa motor axon
Gastrocnemius muscle contracts and foot extends
Describe the jaw jerk reflex
Hammer tap to chin stretches spindles of jaw elevator muscles (masseter, temporalis, medial pterygoid)
APs conducted along 1a muscle afferents to brainstem
Monosynaptic activation of motor neurones of jaw elevator muscles
APs travel along A motor axon, jaw elevator muscles contract and jaw jerks upwards, closing the mouth
What are the protection mechanisms of somatic reflexes
Escape mechanism
Prevention of muscle overloading
Prevention of inadvertent foreign body ingestion
Digestive aid
Describe the flexion withdrawal reflex
Noxious stimuli activates As and C fibres which activate interneurone which send info through the spinothalamic pathway causing the recruitment of motor neurons which allow a flexion withdrawal reflex
Conscious element involved
Describe muscle loading in jaw muscles
No golgi tendon organs in jaw muscles
Bite force controlled by increasing loading of PDL
Afferents inhibit jaw elevator muscle motor neurones
Anaesthesia of molars increases maximum bite force
