Simple reflexes Flashcards
What is a reflex?
Rapid involuntary response to a stimulus
What are the general functions of reflexes
Protective - limb withdrawal/cough reflex
Postural control - walking
Homeostasis - blood pressure stability
What is the chain of a reflex arc?
Receptor Afferent Integration <=> CNS efferent effector
What are the neuronal components of a reflex?
Receptors
Afferents - sensory neurones
Interneurones - modulation of information in and out
Efferents - (If somatic) innervate muscles
Effectors - Carry out the response
What are interneurones?
Found in the CNS and ENS
They modulate the information coming in and out and tell the brain what is happening
Enable us to overcome the reflex
Give 2 examples of simple stretch (myotatic) reflexes
Posture - important for the adjustment of muscle contraction
Receptors - proprioceptors (muscle spindle and GTO)
Explain the process of a myotatic reflex in muscle spindle
- Muscle is stretched
- Nerve endings are stretched (mechanoreceptors)
- Sensory afferent releases excitatory neurotransmitters
- More efferent activity
- ACh released at NMJ
- Muscle contraction causing a response
What type of reflex arc is found in the muscle spindle?
Monosynaptic (1 synapse with no interneurone)
Afferent directly synapses with efferent
Explain the process of a myotatic reflex in the golgi tendon organ
- Increased contraction stretches tendon
- GTO activation increases
- Increased sensory activity
- Increased inhibition of neurone firing
- Decreased efferent activity
- Muscle no longer contracts
What type of reflex arc is found in the golgi tendon organ?
Polysynaptic reverse myotatic reflex
What is the purpose of a myotatic reflex?
Prevents muscle damage by tearing
Prevents muscle damage by overworking
Fine control of muscle tension.
