PNS pt 2

Question 1

Reflexes

Answer 1

Inborn intrinsic reflex: rapid, involuntary predictable motor response to stimulus
Ex: splashing hot water from pot on your arm

Learned (acquired) reflexes from practice/repition
Ex: driving skills

1. Receptor
2. Sensory neuron
3. Integration center
4. Motor neuron
5. Effector

Question 2

Reflex arc

Answer 2

Components of reflex arc
1. Receptor: site of stimulus action
2. Sensory neuron: transmits afferent impulses to the CNS
3. Integration center: monosynaptic/polysynaptic region within the CNS
4. Motor neuron: conducts efferent impulses from the integration center to an effector organ
5. Effector: muscle fiber/gland cell that responds to efferent impulses by contracting/secreting

Question 3

Spinal reflexes

Answer 3

Integration center is in spinal cord
Effectors are skeletal msucle
Stretch, flexor, crossed-extensor

Question 4

Stretch reflexes

Answer 4

How stretch reflex works:
- stretch activates muscle spindle (receptor)
- sensory neurons synapse directly w/ alpha motor neurons in spinal cord
- alpha motor neurons cause stretched muscle to contract
- all stretch reflexes are monosynaptic and ipsilateral

Question 5

Patellar knee jerk reflex

Answer 5

1. Tapping patellar ligament excites muscle spindles in quads
2. Afferent impulses travel to spinal cord, synpases occur w/ motor neurons
3. motor neruons senc activating impulses to quads, contractions, extending knee

Question 6

Abnormal stretch reflex

Answer 6

hyperreflexia, occurs when the stretch reflex response is exaggerated or excessive. This can manifest as brisk reflexes, muscle spasms, or even rhythmic jerking movements called clonus

Question 7

Flexor + crossed-extensor reflexes

Answer 7

Flexor withdrawal reflex
- initiated via painful stimulus
- automatic withdrawal of threatened body part
= ipsilateral + polysynaptic
- descending signals from brain can override flexor reflexes

Crossed extensor reflex
- flexor reflexes in weight-bearing limbs to maintain balance
- ipsilateral flexor reflex + contralateral extensor reflex
- stimulated side withdrawn (flexed)
- contralateral side is extended

Question 8

Superficial reflexes

Answer 8

Plantar reflex (babinski reflex)
- stimulus: stroking lateral of sole of foot
- normal response: downward flexion of toes
- tests fuction of corticospinal tracts