Autonomic nervous system

Question 1

What division of the nervous system is ANS a part of and what are its characteristics?

Answer 1

• Part of the peripheral nervous system
• Not under conscious control.

Question 2

What parts of the body does the ANS control?

Answer 2

• Non-skeletal peripheral function:
  
  • Cardiac muscle
  • Smooth muscle
  • Internal organs
  • Skin

Question 3

What are the two types of afferent neurones and what are their characteristics?

Answer 3

• Somatic sensory and visceral sensory
• Somatic deals mainly with external stimuli e.g muscles sensing movement during walking.
• Visceral mainly deals with internal stimuli.

Question 4

How does information from the sensory afferent divisions reach the CNS?

Answer 4

• The afferent division feeds information to the PNS (from both visceral and somatic sensory divisions):
  
  • To cranial/spinal nerves
• The PNS then feeds the information to the CNS where it is processed.

Question 5

How does information from the CNS reach the motor efferent divisions?

Answer 5

• The CNS processes information and produces a signal.
• The signal is passed onto the PNS, cranial/spinal nerves.
• The PNS then feeds the signal to the motor efferent divisions (both visceral and somatic motor divisions) to produce a response to the initial sensory information.
• In the visceral motor divisions, it is further divided into sympathetic and the parasympathetic arms.

Question 6

What kind of effect do the sympathetic and the parasympathetic arms of the ANS have and what are the implications of this?

Answer 6

• Parasympathetic = ‘rest and digest’, routine maintenance.
• Sympathetic = ‘Fight or flight,’ mobilisation and increased metabolism.
• They often innervate the same tissues and generally they have antagonistic effects.

Question 7

What effect will the parasympathetic/sympathetic arm have on:

1. The heart
2. The stomach
3. The pupil
4. The lungs
5. The liver
6. The bladder

Answer 7

• Contractility = pumping stronger

Question 8

Do the PNS/SNS always carry out opposing effects?

Answer 8

• No. In the case of blood vessel tone - they are both responsible for constriction and dilation.

Question 9

How do baroreceptors work to regulate BP (make sure to understand the concept of PNS/SNS)?

Answer 9

• If BP is high - baroreceptor (visceral sensory) firing rate is high and this is passed onto the sensory (afferent) division -> PNS (cranial and spinal nerves) -> CNS.
• Then the sensory information is processed in the integrating centre and the efferent signal, in this case, is passed onto the PNS -> motor (efferent) division -> visceral motor division ->positive signal on parasympathetic increases and negative signal on sympathetic increases -> cardiac muscles -> heart rate slowed.
• If the baroreceptor firing rate is slow the sympathetic nervous system is more positively stimulated than the parasympathetic and thiw will work to increase the heart rate.