Lecture 11: Communication Pathways

Question 1

What is the difference between a reflex and a reaction?

Answer 1

Reflex: Coordinated by reflex centers in the spinal cord or brainstem.
Reaction: Coordinated by higher brain centers: cerebrum, basal nuclei, and cerebellum.

Question 2

What are the five elements of a reflex arc?

Answer 2

1. Receptor: (Stimulus detected here)
2. Sensory neuron (Transmit afferent impulse to CNS).
3. Integration center (cranial/spinal reflex, mono or polysynaptic)
4. Motor neuron (Transmit efferent impulses to the effector).
5. Effector (Muscle or gland cell)

Question 3

What is the functional classification of reflexes?

Answer 3

Somatic reflex: Effectors are skeletal muscles only.
Autonomic reflex: Effectors are smooth muscles, cardiac muscle or glands.

Question 4

What are some examples of somatic reflex?

Answer 4

1. Remove a limb from a hot/damaging object.
2. Muscle and tendon stretch
3. Blinking
4. Swallowing
5. Turning head towards auditory and visual stimuli.

Question 5

What are some examples of autonomic reflex?

Answer 5

1. Salivation reflex
2. Defecation reflex (bowel movement)
3. Micturition reflex (urination)
4. Chemoreceptor reflex
5. Enteric nervous system of digestive system.

Question 6

What is a consequence to spinal cord trauma?

Answer 6

Loss of voluntary control of defecation and micturition.

Question 7

What is the enteric nervous system?

Answer 7

Controls local activity of smooth muscle and gland secretion to optimize digestive and absorptive functions.

Question 8

What are the two nerve plexuses found within the wall of the GI tract?

Answer 8

1. Submucosal Nerve Plexus (Controls activity of glands)
2. Myenteric Nerve Plexus
   (Controls motility; between circular and longitudinal smooth muscle layers).

Question 9

Which parts of the brain are involved in improving reactions?

Answer 9

Premotor cortex in the frontal lobe and the cerebellum.