Reflexes

Question 1

what are the components of a reflex arc?

Answer 1

stimulus triggers receptor of afferent nerve and sends signal to CNS
CNS sends signal to efferent nerve and triggers effector which initiates response action

Question 2

what happens in the stretch reflex arc?

Answer 2

spindle is stretched, activating sensory neuron
sensory neuron activates alpha motor neuron
alpha motor neuron stimulates muscle fibers to contract

Question 3

what is a muscle spindle?

Answer 3

a proprioceptor stimulated by increased muscle length, spindles allow continuous feedback of information to the brain through spinocerebellar pathway

Question 4

what is the body response in a flexor/withdrawal reflex?

Answer 4

activated in response to a painful stimulus (protective reflex) the crossed extensor reflex subsequently supports the body weight against gravity as you move away from the stimulus

Question 5

what is the golgi tendon organ?

Answer 5

located at the junction between tendon and muscle, very sensitive to muscle tension, nerve terminals innervate collagen of tendon

Question 6

describe the GTO reflex?

Answer 6

during muscle contraction, GTO detects tension in muscle, info is carried to spinal cord and synapses with an interneuron
if tension becomes excessive, contracting muscle is inhibited (reflex relaxation)

Question 7

which is a strech detector and which is a tension detector?

Answer 7

muscle spindle = stretch
golgi tendon organ = tension

Question 8

what is the pathway for the flexor/withdrawal reflex?

Answer 8

initiated by cutaneous receptors - pathway is spread over several segments of spinal cord

Question 9

what is the difference between upper and lower motor neurons?

Answer 9

UMN stimulates LMN through corticospinal tract, either facilitates or inhibits LMN - LMN cell body located in spinal cord from where the axon travels out directly to the skeletal muscle stimulating it to contract

Question 10

what is flaccid paralysis?

Answer 10

damage or weakness of lower motor neuron type, including weakness of the respiratory and pharyngeal muscles, progressing to maximum severity within several days to weeks

Question 11

what are the important features of muscle spindles and GTO? (7)

Answer 11

1. Continuous feedback of information to the brain from a contracting muscle about its status during contraction
2. they are stretch and tension/force detectors respectively
3. stretch reflexes are important in maintenance of normal posture and balance as reflexes allow for rapid automatic adjustments in the muscle
4. muscle spindles and stretch reflexes especially prominent in the anti-gravity muscles and muscles
   where fine control is required
5. they prevent overstretching of a muscle by initiating reflex contraction
6. GTO reflex prevents excessive force
7. feedback control of muscle length in response to a load helps prevent jerky movements