L59. Reflexes Flashcards
Reflexes are involuntary movements controlled by which nerves?
Spinal nerves and cranial nerves
Give the basic motor pathway:
________ -> ___________ -> ___________
Motor cortex -> Brainstem/spinal cord -> muscle
Which 2 regions activate motor neurons?
Brain regions (cortex) Peripheral receptors (reflexes)
Give the motor pathway for reflexes
Receptor reflexes -> brainstem/spinal cord -> muscle
Which section of the spinal cord in grey matter?
Inner portion of spinal cord is grey matter.
Which portion of the spinal cord is white matter?
Outer portion of the spinal cord is white matter.
Describe the position and shape of the dorsal horn.
The dorsal horn is at the back and is thinner.
Describe the location and shape of the intermediate horn.
The intermediate horn sits in between the dorsal and ventral horn.
Describe the position and location of the ventral horn.
The ventral horn is at the front and is thicker than the dorsal horn.
Where do sensory afferents travel to?
Dorsal horn
Ventral signals travel via _______ _____________.
Motor efferents
Name the 2 types of somatic reflexes.
Tendon - jerk
Cutaneous reflex
Give the path of a monosynaptic reflex arc.
Arrow 1 : Receptor to Ventral horn (via dorsal horn)
SYNAPSE 1
Arrow 2 : Ventral horn to effector
Fill in the following for a reflex pathway :
- Hammer tap to muscle
- ___________________________________
- Action potentials are _________________________________________
- Monosynaptic activation of motor neurons
- Axon potentials ________________________________________
- Muscles contract
- Hammer tap to muscle
- Muscle spindles stretch
- Action potentials are conducted along group 1a muscle afferents to the brainstem.
- Monosynaptic activation of motor neurons
- Axon potentials travel along A-alpha motor axon.
- Muscles contract
Describe the anatomical benefit of the reflex pathway.
A digestive aid, eg gag reflex.
Describe the route of a disynaptic pathway.
Stimulus receptor to dorsal horn SYNAPSE Dorsal horn to ventral horn (interneuron) SYNAPSE Ventral horn to muscle effector
During muscle loading, how is the receptor activated?
Stretch and contraction
Describe the anatomy behind muscle loading reflexes, and why this is of benefit.
Afferent signals cause the inhibition of motor neuron activation.
- > inverse stretch reflex
- > Group 1b muscle afferents
This prevents the overloading of muscles.
Biting force is controlled by load. Describe the effect of the muscle loading reflex on jaw muscles.
When hit, afferents inhibit jaw elevator muscle motor neurons (so jaw opens slightly to counteract the load)
Describe how the pharyngeal reflex is activated.
Activated by mechanoreceptor afferents in the posterior part of the tongue / soft palate.
Describe the path from stimulus to gag reflex.
Stimulus for gag reflex -> Lower medulla -> Upper medulla -> Bilateral contraction of posterior oral and pharyngeal muscles.
Describe what onsets a salivary stimulus.
Gustatory (taste)
chewing forces
