Reflexes Flashcards
What are reflexes
Involuntary actions
What about reflexes mean they have a short latency
Single synapse
What are motor neurons activated by
- various brain reflexes
- various peripheral receptors
Where can motor cell bodies
Ventral horn of the spinal cord or in cranial nerve nuclei
Describe muscle spindles
- sensory endings wrapped around the intrafusal fibres
- when the muscles contract the muscle spindles relax
How many synapses are the ventral horn
Only one synaptic transmission in the ventral horn
What are some components of the reflex pathway
- stimulus
- receptor activation (mechanoreceptor)
- stimulus transduction AP conduction along sensory axon (A alpha)
- synaptic transmission
- motor neuron recruitment AP conduction along motor axon
- synaptic transmission (effector recruitment)
- response
What are the different jerk reflexes
- biceps jerk reflex
- ankle jerk reflex
- tricep jerk reflex
- rectus abdominus reflex
Describe the jaw jerk reflex
- hammer tap to the chin
- stretches spindles of jaw elevator muscles (Masseter, temporalis, medial pterygoid)
- action potentials conducted along group 1a muscle afferents to the brainstem (Aalpha)
- monosynaptic activation of motor neurons jaw elevator muscles
- action potentials travel along motor axon
- jaw muscles contract
- jaw jerks upwards, mouth closes
What is the ankle jerk reflex
- hammer tap to Achilles’ tendon
- stretches spindles within gastrocnemius
- action potentials conducted along 1a muscle afferents
- monosynaptic activates neurons of gastrocnemius muscle
- axon potentials
- gastrocnemius muscle contracts
- foot extends (plantar extension)
What is the latency of the response
Time between stimulus and response
What latency is shorter, jaw jerk or ankle reflex?
The latency for the jaw jerk is less than that for the ankle jerk reflex
Why is the latency for the jaw jerk less than that for the ankle jerk reflex
Because the neural pathway for the jaw jerk is less than that for the ankle jerk reflex
Is the amplitude more for the jaw jerk reflex or for the ankle jerk reflex
The amplitude for jaw jerk is less than that for the ankle jerk reflex
Why is the amplitude bigger jaw jerk and the ankle jerk reflex
The masseter is a smaller muscle than gastrocnemius, recruitment of muscle fibres in masseter less than for gastrocnemius
What are the somatic reflexes receptors
Propnoiceptor endings, group la muscle fibres, homozygous motor neurons
Maintenance of posture and muscle tone
What are the somatic reflexes functions
- escape mechanism
- prevention of muscle overloading
- prevention of inadvertent ingestion of a foreign body
- digestive aid
What is the flexation withdrawal reflex
- inhibition of motor neuron activation
- inverse myotactic reflex (inverse stretch reflex)
- prevents over loading of muscle
What is bite force controlled by
Loading of the periodontal ligament
What does anaesthesia of molars do to bite force
Increases bite force
What is the activation of the pharyngeal reflex
Mechanoreceptor afferent from the posterior part of the tongue/ soft palate
The pharyngeal reflex involves the stimulation of what fibres
Stimulation of sensory fibres from the glossopharyngeal nerve and/or the Trigeminal nerve
Where do the afferents of the pharyngeal reflex
Afferents terminate in the brainstem
Where do the inter neurons in the pharyngeal reflex project from
The Spvn to nucleus ambigus (X motor neurons)
X afferents then terminate innervate muscles
What are the stimuli for salivary reflexes
Gustatory (taste), visual, olfactory, chewing
What is the outcome of salivary reflexes
