Muscle Reflexes Flashcards
Where do alpha motor neurons get synaptic inputs from?
- Descending tracts (eg corticospinal)
- Spinal interneurons
- propriosponal neurons
- afferent fibres (type Ia)
What is a key when it comes to the motor and sensory systems?
They work together to coordinate movement
What main receptors control movement, and how do they?
Muscle spindles- monitor muscle length and the rate at which length changes.
Nociceptive receptors in the skin
Golgi Tendon Organs- monitor muscle tension
Joint receptors- monitor position
What are the 5 elements of all spinal reflexes?
Receptors Afferent (sensory) fibres Central synaptic relay Efferent (motor) fibres Effectors (skeletal muscle)
What is the stretch reflex(other name + elements)
Myostatic reflex/ Tendon reflex
- Receptors: Muscle spindles detect change in length
- Afferents: Type Ia fibres
- Synaptic relay: Ia afferents to Alpha MNS
- Efferents: Alpha MN axons
- Effector: extrafusal muscle fibres
What is reciprocal inhibtion?
Afferents also make contact with another synaptic relay, in this case and Ia interneuron.
This causes inhibition of MNs of the antagonist muscle
What spinal segments are involved in the biceps jerk?
C5 and C6
What spinal segments are involved with the knee jerk?
L3, L4
What is the role of gamma MNs?
- Ia afferents come off muscle spindle
- alpha motoneurons cause muscle contraction,flaccid muscle spindle
- As a result the Ia afferent does not fire as no stretch on spindle
- However gamma MNs stretch the muscle spindle during contraction, so the Ia afferents can fire during contraction and the CNS will receive information.
When do gamma MN’s fire?
Typically precedes alpha MN but not in isolation, so alpha-gamma coactivation.
What are golgi tendon organs?
Structures (receptors) found in tendons that send out an Ib afferent
What is the reverse myostatic reflex?
receptor-golgi tendon organs afferent-Ib type fibres Synaptic relay-Ib interneurons (these inhibit alph MNs) Efferent- alpha MN axon Effector-muscles
What is the function of the reverse myostatic reflex?
- To protect muscles from overload
- Normally to maintain muscle tension
What is the flexion reflex?
Receptor-Nociceptors Afferents- type III and IV fibres Synaptic relays- Excitatory interneurons located at MANY spinal segements. Efferents- axons of flexor alpha MNs Effectors- flexor muscles
How does the crossed extension reflex work?
Significance in terms of maintaining balance.
Interneurons relay information to OTHER SIDE OF SPINAL CORD, causing alpha MNs to cause extensor muscle contraction, and flexor inhibition (reciprocal inhibition)
