1. Unit 5 Nervous System part 4: Autonomic Nervous System (ANS) & Reflex Arc Pathways

2. Autonomic Nervous System
Subdivison of the peripheral nervous system that regulates involuntary effectors (cardiac and smooth muscle, glands)
Controls internal body processes such as:
Production of bodily fluids
Blood pressure
Heart rate
Digestion
2 Divisions: Sympathetic & Parasympathetic
Act as antagonists

4. 1) Sympathetic Division
The major function of the sympathetic division is to serve as an “emergency system” called the “fight-or-flight” response
When the body is under stress, or might be threatened, the sympathetic responses increase greatly to prepare our body to “fight” or “flee”
Nerve fibers that play a role in the sympathetic response release epinephrine (more commonly known as adrenaline)

5. Epinephrine may cause the following responses:
Increased heart rate
Dilation of blood vessels in skeletal and cardiac muscles
Constriction of blood vessels in non-essential organs
Dilation of respiratory airways
Increased sweating
Increased blood glucose levels
Pupil dilation

6. This is a normal reaction in times of stress, which enables us to retreat or resist a perceived threat
However, chronic exposure to such stress can lead to dysfunction of the ANS

8. 2) Parasympathetic division
At rest, the parasympathetic division controls most effectors
Sometimes called: “rest and repair”
Parasympathetic division slows heart rate, promotes digestion, allows for urination, tears and salivation
Maintains homeostasis
Relax!

9. Reflex Arcs: simplest nerve pathway
Reflex- automatic subconscious response to changes (stimuli) within or outside the body
2 types:
autonomic reflex arc, affecting inner organs
somatic reflex arc, affecting muscles
Help to maintain homeostasis by controlling involuntary processes like breathing, heart rate, blood pressure, etc.
Usually used to describe only involuntary responses (swallowing, sneezing, coughing, vomiting)

10. There are 5 main components of a reflex arc:
1) Sensor/Receptor- receives a stimulus
2) Sensory Neuron- Sends the sensory information to the CNS
3) Interneuron- conducts/relays nerve impulse from sensory neuron to motor neuron
4) Motor Neuron- carries the motor response to an effector
5) Effector- Muscle or gland that responds to motor neuron stimulation

11. Sensory neuron: passes “hot” message to CNS 2. 2. 2. 1. 3. 4. 4. 5. 4.
Receptor: senses heat
Sensory neuron: passes “hot” message to CNS
Interneuron: routes message to motor neuron
Motor neuron: passes “contract” message to arm muscle
Effector: contracts to pull arm away from heat

12. Today we will test your somatic (voluntary body muscle) reflexes because the somatic reflexes have an important clinical significance
Abnormalities may be present in certain diseases
Somatic reflexes deal with muscles instead of internal organs

14. Patellar Reflex- animation (first one)

15. Biceps Jerk- animation

16. Achilles Reflex (Ankle Jerk)- animation

17. Plantar Flexion- animation

18. Testing the Pupillary Reflex- animation (stop at 55sec)
CN: cranial nerve