Spinal reflexes Flashcards
What are the two functions of reflexes?
Protective: withdrawal of limb from hot surface
Postural: control of walking
What are the two categories of reflex?
Autonomic: responses are controlled by autonomic neurons
Somatic: responses are controlled by somatic motor neurons and skeletal muscle
What is the reflex arc?
1) Receptor - converts stimuli to electrical stimulus
2) Sensory afferent - carries information from receptor to CNS
3) Central neurons - synapse onto interneurons or cell bodies
4) Motor efferent - carries information to effector: two types:
a) Alpha - extrafusal
b) Gamma - intrafusal
5) Effector - converts electrical signal to appropriate response.
What are the two types of skeletal muscle reflex?
1) Monosynaptic - one synapse, stretch reflex
2) Polysynaptic - many synapses, golgi tendon
What is the muscle spindles role?
It is the stretch reflex, found in the bulk of the muscle parallel to muscle fibres. It detects change in muscle length and prevents over stretching.
Sensory afferent –> dorsal root –> alpha motor neurons –> contraction
What is the golgi tendons role?
The golgi tendon is located at the junction of muscle and tendon and protects from overload, it slows down contraction and detects changes in tension.
Contraction –> tendon tension –> GTO –> sensory neuron –> motor activity
What are CPGs?
Central pattern generators are networks of neurons in the CNS that cause rhythmic movements such as breathing and walking
What is reciprocal inhibition and how is it activated?
This is when the antagonist muscle is inhibited with excitation of the effector muscle, activated by ‘1A inhibitory neuron’
How do flexion reflexes work?
Sensory fibres carry information from nociceptors to spinal cord –> nerves activate excitatory interneurons –> some excite alpha motor neurons so the muscle contracts, some activate inhibitory interneurons so muscle relaxes
This is how a limb reflexes away from a stimulus
