W5 The autonomic nervous system

Question 1

What are the functions of the autonomic nervous system?

What functions does it control?

Answer 1

• Maintains an internal environment
• Mostly involuntary (automatic)
• Controls visceral functions (organs-viscera)
• circulation
• digestion
• excretion
• Modulates endocrine function

Question 2

What does the ANS Input consist of ?(afferent)

Answer 2

Sensory neurones from peripheral organs to centres in the hypothalamus, medulla!

Question 3

What does the ANS Output (efferent) consist of?

Answer 3

Sympathetic or Parasympathetic neurons
- organs innervated by both types of neurones (often)
- generally opposing actions

e.g. heart has both

Question 4

What are the functions of Visceral sensory neurons?

Answer 4

• Monitor temperature, pain, irritation, chemical changes and stretch in the
  visceral organs
  (Brain interprets as hunger, fullness, pain, nausea, well-being)
• Receptors widely scattered – localisation poor (i.e. not easy to identify where pain originates) e.g. heart pain= arm pain
• Visceral sensory fibres run together with autonomic (output) nerves

Question 5

What do ANS nerves control?

Answer 5

• Mainly smooth muscle, cardiac muscle and secretory glands

Smooth muscle- Bronchioles, Iris
Digestive system, Bladder, Vascular system

Secretory glands- Adrenal medulla
Pancreatic islets, Salivary glands, Sweat,

Cardiac muscle- Control heart rate, Control contractile force

Question 6

What is the autonomic nervous system divided into?

Answer 6

Sympathetic and Parasympathetic division (SNS and PNS)

Question 7

What does ANS stand for?
What can motor division be divided into?

Answer 7

Autonomic nervous system
Autonomic and Somatic nervous systems

Question 8

What are examples of long and short reflexes?
(visceral reflex arc)

Answer 8

Long- Spinal reflexes e.g. defecation and micturition
Short- enteric” nervous system only involving peripheral neurons

Question 9

What is and what are the features of the Sympathetic nervous system (SNS)?
What increases? (4)

Answer 9

• ‘Fight or flight’ response
• Short term survival
• Generally increases energy availability/capacity and usage e.g.
  – Increase heart rate
  – Increase lung capacity
  – Increase blood flow to some skeletal muscles
  – Increase blood glucose

Question 10

What is and what are the features of the Parasympathetic nervous system? (PNS)
What decreases/increases? (4)

Answer 10

• ‘Rest and digest’
• Long term survival
• Generally reduces energy availability/
  capacity and usage e.g.
  – Decrease heart rate
  – Decrease lung capacity
  – Increase blood flow to digestive system
  – Increase fat/glycogen stores

Question 11

What are the effects of the Autonomic Nervous System?
(PNS ans SNS)

Answer 11

Each organ controlled by branches of both
parasympathetic and sympathetic NS

• Stimulation of the parasympathetic NS has
  broadly opposite effect to stimulation of the
  sympathetic in that organ (and vice versa)

Homeostasis: SNS and PNS are active
constantly - modulating = DYNAMIC BALANCE

Question 12

Structure of a (Somatic NS) motor neurone vs ANS Neurons

Answer 12

Somatic NS- Spinal cord, Somatic motor neurone (myelinated),ACh

Question 13

Similarities and differences in PNS and SNS

Answer 13

Similarities:
2 neurones in series

Differences:
* Where nerves originate ( leave CNS)
* Where the ganglia (cell bodies) are, ie where 2 neurons synapse
* Differences in neurotransmitters and receptor subtypes

Question 14

Where is the adrenal gland located?

Answer 14

On top of the kidneys

Question 15

What is the neurotransmitter released on the effector organ in they Sympathetic NS (SNS)

Answer 15

Noradrenaline

Question 16

What are receptors?

Answer 16

Protein structures that receive and transduce signals
– Include ligand gated ion channel-linked (ionotropic) receptors
– G protein-linked (metabotropic) receptors

Question 17

What are the 2 types of acetylcholine receptors?

Answer 17

Nicotinic and Muscarinic

Nicotinic
* 5 subunits
* 2 Ach binding sites
* (Skeletal muscle), autonomic
ganglia, adrenal medulla
* Ionotropic / ligand gated

Muscarinic
* 7-TM GPCR
* 3 subtypes
– M1 - brain, parietal cells (excitatory)
– M2 – heart (inhibitory)
– M3 - smooth muscle, glands, (excitatory)

Question 18

What does the PNS do to heart rate, lung capacity, blood flow and glycogen storage?

Answer 18

– Decrease heart rate
– Decrease lung capacity
– Increase blood flow to digestive system
– Increase fat/glycogen stores

Question 19

What is the effector neurotransmitter in the SNS?

Answer 19

NORADRENALINE

Question 20

What is the effector neurotransmitter in the PNS?

Answer 20

ACETYLCHOLINE

Question 21

What are Adrenoceptors and the 2 types?

Answer 21

• G-protein coupled receptors
  (metabotropic)
• 2 types: alpha and beta
• Respond to adrenaline,
  noradenaline
• Noradrenaline/Adrenaline:
  Diverse actions depending
  on target
• Depending on the
  downstream molecules that
  they activate
• Post and Pre synaptically

Question 22

Why does the sympathetic nervous system inhibit digestion?

Answer 22

To divert blood toward the muscles