Anatomy &Physiology
REFLEX ACTIVITY
CHAPTER 13 PART 4
Reflexes
 much of what body must do every day is
programmed as reflexes
a
rapid, predictable, & involuntary
response
 occur over neural pathways called reflex
arches
Reflexes
Inborn or Intrinsic
1.



unlearned, unpremeditated , involuntary
designed to keep you in homeostasis w/out having to think
may or may not be aware of it
2. Learned or Acquired

result of practice or repetition
2 Types Reflexes
Autonomic reflexes:
1.




regulate activity of smooth muscles, heart, glands
examples:
salivating when smell Thanksgiving dinner cooking
pupils dilating/constricting with change in amount light
2. Somatic reflexes:

stimulate skeletal muscles

examples:

pull hand away from hot stove
5 Parts to a Reflex Arc
Receptor: site of stimulus
2. Sensory neuron
1.

afferent impulses to the CNS
3. Integration center

Monosynaptic: 1 synapse sensory  motor neuron

Polysynaptic: multiple synapses with interneurons
4. Motor neuron

efferent impulses to effector organ
5. Effector

muscle fiber or gland that responds to efferent impulse
5 parts of Reflex Arches
Spinal Reflexes
 somatic reflexes mediated by spinal cord (no
involvement of brain)
 mostly, remain intact even if brain not functioning
as long as spinal cord is intact
 most of these do send signals to brain
 clinically important to asses condition of the nervous
system

exaggerated, distorted of absent reflexes indicate degeneration
or pathology
Spinal Reflexes
What the Nervous System Needs to Know About
Skeletal Muscle so
there is Coordination
length of muscle
1.

muscle spindles
2. amount of tension on the muscle

tendon organs
Both called proprioceptors

important role in spinal reflexes

provide essential feedback to cerebral cortex & cerebellum
https://www.youtube.com/watch?v=obM1uHucAbM
Anatomy of Muscle Spindle
The Stretch Reflex
 makes sure muscle stays at length set by motor
cortex
 important for maintaining muscle tone


adjusts it reflexively
sustains upright posture in large muscles of back
https://www.youtube.com/watch?v=nuzx5WJc-mE
Stretch Reflexes
Autonomic Reflexes
 https://www.youtube.com/watch?v=krhTPjle7S8
Autonomic Reflexes
Pupillary Reflexes