WEEK 5 Flashcards
What is a neural reflex?
A stereotyped, involuntary reaction of the CNS to specific sensory input
What are the three general functions of reflexes?
Protective-limb withdrawal, cough reflex
Postural control-walking
Homeostasis-BP
Describe the characteristic chain of components of a reflex arc
sensory receptor-afferent neurone-(integration centre)-efferent neurone-effector
What is the role of sensory receptors in the reflex arc?
Where information comes into reflex arc, detect sensory stimuli-can be part of sensory neurone/can be afferent neurone
What is the role of afferent/sensory neurones in the reflex arc?
Convey AP from sensory receptor site towards CNS
What is the role of the integration centre in the reflex arc?
It contains interneurones (not relay neurones) in CNS/enteric NS which cause modulation, allowing adjustment of reflex arc activity via brain involvement
What is the role of efferent/motor neurones in the reflex arc?
Convery AP from CNS to effector
What is the role of the effector in the reflex arc?
causes reflex action-muscle/gland
What is the role of simple stretch reflexes?
Posture control, adjusting degree of skeletal muscle contraction to allow postural change
What sensory receptors are responsible for simple stretch reflexes?
Proprioceptors
Give two examples of proprioceptors
Muscle spindles
Golgi tendon organs (GTO)
What are muscle spindles?
Proprioceptors consistent of intrafusal muscle fibres enclosed in a sheath (spindle), providing information on muscle length/stretch and the rate of stretch (myotatic reflex)
Process of muscle spindle action in knee jerk reflex
Spindles stretched when quadricep muscles lengthen, depolarisation causing AP, sensory neurone carries AP into spinal cord via dorsal root and synapses directly to motor neurone (MONOSYNAPTIC)/inhibitory interneurone, motor neurone carries/doesn’t carry AP to quadricep/hamstring muscles, quadricep muscles contract/hamstring muscles relax, leg extension
What are golgi tendon organs (GTO)?
Sensory nerve endings found within tendons that are activated when muscle contracts due to collagen fibre stretching in tendons
Process of GTO action
muscle contraction, depolarisation of GTO nerve endings, AP transmitted to interneurone via sensory neurone, synapse with excitatory interneurone (POLYSYNAPTIC), synapses with inhibitory interneurone, synapses with motor neurone, motor neurone lacks AP, less muscle contraction (reverse myotatic reflex)