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PHYG > Module 3 Section 2.1 > Flashcards

Module 3 Section 2.1 Flashcards

1
Q

Compare and contrast the parasympathetic and sympathetic nervous systems.

A

Sympathetic nervous system: always active; stimulates the flight-or-flight response (the adrenal medulla produces epinephrine and norepinephrine during this).

Parasympathetic nervous system: also constantly active; responsible for rest-and-digest activities (processes include digestion, urination and salivation).

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2
Q

Describe what is meant by sympathetic tone and parasympathetic tone and what is their relationship.

A

Their relative contributions are called either sympathetic tone or parasympathetic tone.

In other words, one system gets activitated more while the other one decreases its firing, thus, one system becomes the dominant influence on the organ.

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3
Q

Compare and contrast sympathetic dominance and parasympathetic dominance.

A

Sympathetic dominance
- Ex: if you were out on a hike and encountered a bear, this would be activated w/o conscious thought (fight-or-flight).
- This will resut in:
• increased HR & force of contraction
• constrict arterioles to increase BP
• dilate resp airways to bring more O2
• breakdown carbs & fat stores to make sure you have plenty of glucose for your muscles
• arterioles in the muscles dilate so there is increase O2 & glucose delivery
• inhibit digestion and renal function
• increased sweating to prepare for excess heat generation of phys activity
• vision and hearing are heightened

Parasympathetic dominance
- Ex: you out-ran the bear and are now safe. Your PNS would be activated to relax/calm your body while you recover
- This will result in:
• decreased HR & force of contraction
• dilate arterioles to decrease BP
• constrict resp airways since not as much O2 is needed
• liver stops producing glucose and focuses on digestion (i.e., produces bile)
• arterioles in the muscles constrict since there is not a need for as much O2 & glucose delivery
• promote digestion and renal function
• pupils constrict back to normal
• adrenal glands stop producing NE and Epi

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4
Q

Describe the role of the adrenal glands in the autonomic nervous system.

A

Adrenal medulla
- Functions like a sympathetic ganglia
- Innervated by: sympathetic preganglionic fibre
- Does NOT give ride to a postganglionic fibre
- Upon sympathetic stimulation, it releases chemical transmitters (hormones) into the blood
• 20% = NE
• 80% = Epi
- Thus, upon stimulation it acts as a global amplifier of the sympathetic system

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5
Q

Describe the receptors of the autonomic nervous system.

A

Although ACh, NE and Epi are the neurotransmitters, it is the receptors for these chemicals that defines how a tissue will respond to ANS stimulation.

Cholinergic receptor: a receptor on the membrane of cells that responds to the neurotransmitter ACh
- Muscarinic receptors:
• activated by the mushroom poison muscarine
• found on the effector cell membranes
• respond to ACh released by parasympathetic postganglionic fibres
• binding of ACh or muscarine to muscarinic receptors triggers a G-protein coupled reaction that results in the opening of cation channels
• they create a depolarized potential
- Nicotinic receptors:
• activated by the tobacco plant derivative nicotine
• found on the cell bodies of postganglionic cells in all autonomic ganglia and bind ACh released from parasympathetic preganglionic fibres
• binding of ACh or Nicotine to nicotinic recepots on cation channels leads to opening of the channel, thus leading to the response

Adrenergic receptor: a G-protein coupled receptor in the membrane of cells that responds to catecholamine neurotransmitters. These catecholamines and epinephrine and norepinephrine
- Epinephrine (systemic circulation)
• released from the adrenal medulla
• a1
• B1
• B2
- Norepinephrine (local release)
• released from the postganglionic fibres as a neurotransmitter and adrenal medulla as a hormone
• a1
• a2
- Alpha receptors
• both a1 and a2 receptors have a greater sensitivity to NE than Epi
• Activation of a1 receptors activates the Ca second messenger system
• a2 activation suppresses the cAMP pathway
- Beta receptors
• B2 receptors have a greater affinity for Epi than B1 receptors
• B1 receptors respond equally to NE and Epi
• Both B1 and B2 receptors enhance the cAMP pathway

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6
Q

What does the ANS influence?

A

Heart, smooth muscle, and glands through the PNS and SNS.

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7
Q

Where does the output of the ANS come from?

A

Output = hypothalamus, brainstem and spinal cord

Goes to = periphery via the sympathetic and parasympathetic pathways.

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8
Q

Which of the following effects is mediated by the SNS?

a) pupil constriction
b) inhibition of the adrenal glands
c) increased heart rate
d) decreased lung capacity

A

c) increased heart rate

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9
Q

Which of the following effects is mediated by the PNS?

a) stimulation of the digestive system
b) bronchodilation
c) increased blood flow to the lungs
d) secretion of epinephrine and norepinephrine by the adrenal glands

A

a) stimulation of the digestive system

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10
Q

True or false: all autonomic nerve pathways involve a 2 neuron chain connecting the CNS to the effector.

A

True

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11
Q

Discuss the role of the first neuron.

A

The cell body of the first neuron is located within the CNS and its axon (called the preganglionic fibre) synapses with the cell body of the second neuron.

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12
Q

Discuss the role of the second neuron.

A

The second neuron’s cell body is located within a cluster of neuronal cells called a ganglion. The axon of the second neuron (called the postganglionic fibre) innervates the effector organ.

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13
Q

Test yourself: list the characteristics and neurotransmitters relating to sympathetic and parasympathetic regulation.

Preganglionic fibre

  • SNS:
  • PNS:

Postganglionic fibre

  • SNS:
  • PNS:

Neurotransmitters released from preganglionic fibre

  • SNS:
  • PNS:

Neurotransmitters released from postganglionic fibre

  • SNS:
  • PNS:

Fibre type

  • SNS:
  • PNS:
A

Preganglionic fibre

  • SNS: short
  • PNS: long

Postganglionic fibre

  • SNS: long
  • PNS: short

Neurotransmitters released from preganglionic fibre

  • SNS: ACh
  • PNS: ACh

Neurotransmitters released from postganglionic fibre

  • SNS: NE and Epi
  • PNS: ACh

Fibre type

  • SNS: adrenergic
  • PNS: cholinergic
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14
Q

Compare the autonomic nerve origin for the SNS and PSN.

A

SNS

  • Fibres originate: thoracid and lumbar regions of the spinal cord
  • Preganglionic fibres = short and end in ganglia located in chains down both sides of the spinal cord. Some, however, end in ganglia that’s located halfway b/w the CNS and effector organ
  • Postganglionic fibres = long and end on the effector organs.

PNS

  • Preganglionic fibres arise from the brain or lower spinal cord
  • Preganglionic fibres = long and end in ganglia (terminal ganglia) near the effector organ
  • Postganglionic fibres = very short
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15
Q

Compare the neurotransmitters of the SNS and PNS.

A

SNS

  • Preganglionic fibres: short; ACh
  • Postganglionic fibres: long; NE (mostly) or Epi

PNS

  • Preganglionic fibres: long; ACh
  • Postganglionic fibres: short; ACh
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16
Q

What is dual innervation? What are some exception?

A

A concept where effector organs receive input from both the SNS and PNS.

Exceptions:
- Most arterioles and veins recieve sympathetic stimulation only & regulation is acheived by increasing or decreasing activity.
• However, the only ones that have dual innervation are the vessels found in the penis and clitoris.
- Most sweat glands only recieve sympathetic innervation.
• These postsynaptic fibres release ACh instead of NE.
- The salivary glands recieve dual, however, both systems can stimulate salivary secretion.

17
Q

Generally, the SNS is excitatory while the PNS is inhibitory. Ex: SNS increases HR and PNS decreases it.

Discuss the exceptions to this rule.

A

SNS decreases gastric motility and the PNS increases it.

18
Q

Discuss the effect the SNS and PNS have on each organ: heart, eye, digestive tract, blood vessels, lungs and urinary bladder

A

Heart

  • SNS stimulation: increased rate and force of contraction (of whole heart)
  • PNS stimulation: decreased rate and force of contraction (of atria only)

Eye

  • SNS stimulation: dilation of pupil; adjustment of eye for far vision
  • PNS stimulation: adjustment of eye for near vision

Digestive tract

  • SNS stimulation: decreased motility (movement); contraction of sphincters (to prevent forward movement of contents); inhibition of digestive secretions
  • PNS stimulation: increased motility; relaxation of sphincters (to permit forward movement of contents); stimulation of digestive secretions

Blood vessels

  • SNS stimulation: constriction
  • PNS stimulation: dilation of vessels supplying the penis and clitoris only

Lungs

  • SNS stimulation: dilation of bronchioles (airways); inhibition of mucous secretion
  • PNS stimulation: constriction of bronchioles; stimulation of mucous secretion

Urinary bladder

  • SNS stimulation: relaxation
  • PNS stimulation: contraction (emptying)
19
Q

Fill in the blanks with the following words:

  • preganglionic
  • cholinergic
  • sympathetic
  • Norepinephrine
  • parasympathetic
  • postganglionic
  • adrenergic
  • autonomic
  • Acetylcholine
  • epinephrine

___ is the neurotransmitter that is released from the ___ nerve fibre in both branches of the ___ nervous systems. Thus, we call these ___ neurons. In the ___ system, this neurotransmitter is also released from the postganglionic nerve fiber.

___ and ___ are the neurotransmitters released from the ___ nerve fibres of the ___ system. Thus, we call these neurons ___.

A

Acetylcholine is the neurotransmitter that is released from the preganglionic nerve fibre in both branches of the autonomic nervous systems. Thus, we call these cholinergic neurons. In the _parasympathetic _ system, this neurotransmitter is also released from the postganglionic nerve fiber.

Norepinephrine and epinephrine are the neurotransmitters released from the postganglionic nerve fibres of the sympathetic system. Thus, we call these neurons adrenergic.

20
Q

Discuss the selective tissue responses in regards to adrenergic receptors.

A

The effects of sympathetic stimulation is determined by the number and type of adrenergic receptors in the target tissues and organs.

Ex: a1 receptors are almost always excitatory and since they’re expressed in the smooth muscle cells of blood vessels, i their stimulation causes contraction.
- In contrast, a2 stimulation on the smooth cells of the digestive system causes a decrease in contraction.

  • Ex: stimulation of B1 receptors are usually excitatory. They are primarily found in the heart.
  • In contrast, B2 receptors are generally inhibitory and they are mainly found in the smooth muscle cells of arterioles and the respiratory airway.

In other words, when Epi acts on a1 receptors in the blood vessels, the vessel constricts.
Meanwhile, when Epi acts on B2 receptors on bloodvessels, the vessel dilates.

21
Q

Describe how salbutamol was specifically designed to target B2 receptors.

A

Salbutamol, an activator of B2 receptors, is a bronchodilator commonly used to treat asthma because it will open the airways yet have very little effect on heart rate.

This saved people w/ asthma from dying.

The molecule salbutamol is inhaled. It dilates the bronchioles in the lungs so that you can get more air in.

Adrenaline and noradrenaline can either increase HR, contrict your bloodvessels and constrict or relax the bronchials in your lungs. We need these to dilate the lungs. The creators of salbutanol added an extra carbon b/w the benzine ring so the OH bond is much stronger. Therefore, the methylation of the OH is much slower. Thus, its in the receptor longer and allows you to be able to breathe again.

The aeresol goes straight to the active site.

22
Q

What is the general action and tissue selective response for the alpha and beta receptors?

A

a1

  • General action: excitatory
  • Tissue selective response: smooth muscle cells of blood vessels, stimulation causes contraction

a2

  • General action: inhibitory
  • Tissue selective response: smooth muscle cells of digestive system, stimulation results in decrease in contraction

B1

  • General action: excitatory
  • Tissue selective response: primarily found in the heart

B2

  • General action: inhibitory
  • Tissue selective response: primarily found in smooth muscle cells of arterioles and the respiratory airway
23
Q

For each question, choose the neurotransmitter and receptor that you think is associated w/ each fight or flight response.

  1. Increased heart rate and force of heart contraction
    a) Epi
    b) NE
  2. Constriction of arterioles to increase BP
    a) Epi
    b) NE
  3. Dilation of respiratory airways to bring in more O2
    a) Epi
    b) NE
  4. Inhibition of digestion and renal function
    a) Epi
    b) NE
A
  1. a) Epi
    b) NE

2.
b) NE

3.
a) Epi

4.
b) NE

24
Q

For each question, choose the neurotransmitter and receptor that you think is associated w/ each fight or flight response.

  1. Increased heart rate and force of heart contraction
    a) a1
    b) a2
    c) B1
    d) B2
  2. Constriction of arterioles to increase BP
    a) a1
    b) a2
    c) B1
    d) B2
  3. Dilation of respiratory airways to bring in more O2
    a) a1
    b) a2
    c) B1
    d) B2
  4. Inhibition of digestion and renal function
    a) a1
    b) a2
    c) B1
    d) B2
A
  1. c) B1
  2. a) a1
  3. d) B2
  4. b) a2

PHYG (14 decks)

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