Autonomic Nervous System

Question 1

What is duel-innervation mean?

Answer 1

This refers to the ability of organs to receive impulses from both sympathetic and parasympathetic neurons

Question 2

Describe the following properties of the automatic nervous system;

• Effectors
• type of control
• neural pathway
• Neurotransmitters
• Action of neurotransmitters on effectors

Answer 2

Effectors include;

• cardiac muscle,
• smooth muscle
• glands

Type of control:

• Mainly involuntary

Neural pathway.

• a motor neuron extends and synapses with an automatic ganglion
  
  • called a sympathetic or parasympathetic preganglionic neuron
• From the automatic ganglion extends and synapses with an effector cell through the postganglionic neuron
• This can also happen with the adrenal gland called the adrenal medulla.

Neurotransmitter:

Preganglionic fibres release acetylcholine, and

• acetylcholine
• norepinephrine
• preganglionic fibres release acetylcholine
• postganglionic fibres release acetylcholine or norepinephrine.

Action of neurotransmitters on effectors

• sympathetic pathway is excitatory
  
  • increase activity
• parasympathetic pathway is inhibitory
  
  • decrease activity

Question 3

Describe the following properties of the automatic nervous system;

• Effectors
• type of control
• neural pathway
• Neurotransmitters
• Action of neurotransmitters on effectors

Answer 3

Effectors:

• skeletal muscles

Type on control

• voluntary

Neural Pathway

• a motor neuron extends from the CNS of the spinal cord and synapse directly with a skeletal muscle fibre

Neurotransmitters

• acetylcholine

Action of a neurotransmitter on effector:

• always excitatory contracts skeletal muscles

Question 4

Describe the structure of the autonomic nervous system (ANS).

Answer 4

Consists of the following 3 linked neurons

1. preganglionic neurons (myelinated)
2. Autonomic Ganglion
3. Postganglionic (unmyelinated)

The motor output consists of 2 main divisions

• Sympathetic
• Parasympathetic

The 3 linked neurons can be sympathetic or parasympathetic

Question 5

Describe the function of the sympathetic and parasympathetic divisions of the ANS.

Answer 5

Autonomic neurons are classified on the basis of the neurotransmitter they release:

• Cholinergic
• Adrenergic

Cholinergic neurons release acetylcholine, and their effects are short-lived and localized. There are 3 ANS that only release Acetylcholine

• all symp and parasymp preganglionic neurons
• all parasymp postganglionic neurons
• some symp postganglionic neurons

Adrenergic neurons release norepinephrine, and their effects are long-lasting and widespread.

• most used by sympathetic postganglionic neurons

Question 6

Discuss sympathetic and parasympathetic responses.

Answer 6

The sympathetic response is the “fight or flight” response.

1. Pupils dilate
2. Heart rate - Force of blood contraction increase
3. Blood pressure increase
4. Airways dilate
5. Blood vessel constriction in Nonessential organs such as the kidneys, gastrointestinal tract
6. Blood vessels of organs that assist in fighting off danger and exercising dilate
7. Nutrient Breakdown to supply ATP
8. The liver releases glucose into the blood

The parasympathetic response is the “rest and digest” response.

• SLUDD are 5 parasympathetic responses
  
  • Salivation
  • Lacrimation
  • Urination
  • Digestion
  • Defecation
• Also the 3 decreases
  
  • Heart rate
  • Diameter of airways
  • Diameter pf the pupils

Question 7

What is the Autonomic Nervous System?

Answer 7

• Part of the nervous system that regulates smooth muscle, certain glands and cardiac muscle.
• Operates without conscious control from the cerebral cortex
  
  • The hypothalamus and brain stem regulate it
• Contains 2 motor neurons
  
  1. Preganglionic Neuron leading to the autonomic ganglion
  2. Postganglionic neuron leading to the effector cell
• The motor portion of the ANS has 2 divisions which have opposing impacts on the body
  
  • sympathetic
  • parasympathetic

Question 8

Summarize the structure of the Sympathetic Division of the Nervous System

Answer 8

• Also known as the Thoracolumbar division
  
  • outflow comes from the thoracic and lumbar area
  • the cell bodies of preganglionic neurons occupy the 12 thoracic and first 2 lumbar segments of spinal cord
• Sympathetic Ganglia Classified as
  
  • Sympathetic Trunk Ganglia
    
    • lateral to the vertebral column
  • Prevertebral Ganglia
    
    • anterior to the vertebral column
• a sympathetic preganglionic axon can synapse with up to 20 or more postganglionic neurons
  
  • impacting organs throughout the body collectively

Question 9

Summarize the structure of the Sympathetic Division of the Nervous System

Answer 9

• the parasympathetic division is also called the Craniosacral division
  
  • the outflow of nerve impulses come from
    
    • cranial nerve nuclei
      
      • cell bodies found on 4 cranial nerves in the brain stem
        
        • 3 - oculomotor
        • 7 - facial
        • 9 - glossopharyngeal
        • 10 - vagus
    • sacral segments of the spinal cord
      
      • 3 sacral segments S2-S4
• Parasympathetic Ganglia are called terminal ganglia
  
  • found near or within autonomic effectors
  • postganglionic axons are very short
• usually, only synapse with 4 or 5 postganglionic neurons