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physio exam 3 > Peripheral nervous system: efferent division > Flashcards

Peripheral nervous system: efferent division Flashcards

1
Q

what is the efferent division of the PNS?

A

the communication link by which the CNS controls the activities of the effector organs

Allows CNS to control muscles, glands, secretions, movement: homeostasis

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2
Q

What nervous system is involved in the efferent PNS?

a. autonomic
b. somatic
c. both a and b

A

c

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3
Q

What are the two branches of the autonomic nervous system?

A

sympathetic and parasympathetic

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4
Q

What is the autonomic nervous system controlling?

A

involuntary responses of visceral organs(cardiac and smooth muscles) exocrine and some endocrine

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5
Q

What does the somatic nervous system control?

A

voluntary e.g. skeletal muscles

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6
Q

What are the two neurons in the autonomic nervous system?

A

preganglionic fiber

postganglionic fiber

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7
Q

How many neurotransmitters are released by the autonomic nervous system on the structures it controls?
What are the two neurotransmitters?

A

Only two different neurotransmitters: acetylcholine and norepinephrine

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8
Q

What is the significance of varicosity? (the postganglionic fiber terminates in a structure ) ** slide 5 listen

A

Affect all of the effector organs innervated at once. Helps the entire organ function together instead of separate units

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9
Q

The following are characteristics of the sympathetic or parasympathetic nervous system?

a. nerve fibers originate from thoracic and lumbar regions of the spinal cord
b. preganglionic fibers: short, release Ach
c. postganglionic fibers: long, release norepinephrine (andrenergic)
d. synapse within the blank ganglion chain/collateral ganglion

A

Sympathetic nervous system

blank = sympathetic

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10
Q

The following are characteristics of the sympathetic or parasympathetic nervous system?

a. nerve fibers originate from the cranial and sacral levels of the CNS
b. preganglionic fibers: long, release Ach
c. postganglionic fibers: short, release Ach (cholinergic)
d. most synapse at terminal ganglia near effector organs

A

parasympathetic nervous system

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11
Q

If you want to walk, you think about it, but the actions to walk are via involuntary actions, what part of the PNS is involved with this?

A

The somatic nervous system

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12
Q

What is true about the action of parasympathetic and sympathetic nervous systems?

A

They are both active at all times, but one may predominate at any given moment

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13
Q

What is an example of sympathetic dominance?

A

Fight or flight response, prepares the body for stressful situations

  • all responses are to protect the body
  • perform functions more efficiently
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14
Q

what is an example of parasympathetic dominance?

A

dominates in a quiet, relaxed situation

  • low heart and respiratory rate
  • promote digestion and urination
  • responsible for house keeping activities (cook and clean, but don’t do it when you have an exam)
  • conserves energy
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15
Q

Does the autonomic nervous system have synapses?

A

No, only varicosity

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16
Q

What are some involuntary functions the ANS is responsible for ?

A

circulation, digestion, sweating urination

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17
Q

What organs receive dual/reciprocal innervation?

A

visceral organs

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18
Q

What is the advantage of dual/reciprocal innervation?

A

It allows precise control over the activity of an effector organ

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19
Q

What happens in the body during sympathetic dominance?

A
  • dilate blood vessels supplying skeletal muscles
  • increases heart and respiratory rate
  • converts glycogen to glucose (needed by muscles) in liver
  • promote sweating
  • dilate pupils of the eye and bronchioles (far vision can see clearly ahead)
  • inhibit digestion and urination (don’t want these to happen in emergency)
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20
Q

What is sympathetic dominance aimed at?

A

increasing flow of oxygenated, nutrient rich blood to skeletal muscles: strenuous physical activity

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21
Q

What are the exceptions of dual/reciprocal innervation?

A
  • sympathetic only: arterioles and veins, sweat glands
  • salivary glands: have both systems, but leads to increased salivation (thicker saliva sympathetic, parasympathetic saliva = more enzymes so it is thinner)
22
Q

When there are receptors present at different locations, the receptors are coupled to different signaling pathways, and different kinds of receptors have different sensitivity to the neurotransmitters, what is this called?

A

Target specificity

23
Q

The somatic nervous system signals what?

A

skeletal muscle via motor neurons

24
Q

What constitutes the somatic nervous system?

A

Axons and cell bodies

the cell bodies lie in the ventral horn

25
Q

How do the somatic nervous system and the autonomic nervous system differ?

A

In the somatic nervous system axons do not synapse in the ganglion, the SNS can only stimulate skeletal muscle contraction - cannot relax

26
Q

What diseases can result from disturbances in the somatic nervous system?

A

polio, lou gehrig’s disease (ALS)

27
Q

Efferent motor neurons are also composed of two neuron chains. True or false?

A

False - they don’t synapse or stop anywhere, they go directly to the fiber

28
Q

Why are the somatic motor neurons known as the final common pathway?

A

Because once the signal is transferred in a particular axon fiber, it will bring about skeletal muscle contraction and it cannot make the muscle relax

29
Q

What is the neuromuscular junction?

A

The point where the terminal branches (unmyelinated) terminate on the muscle fiber is known as the neuromuscular junction

30
Q

Efferent neuron (myelinated) -> terminal branches (unmyelinated) -> ?

A

neuromuscular junctions

31
Q

What is a neuromuscular junction made of?

A

terminal button: knob like terminal at muscle fiber

Motor end plate: muscle cell membrane below terminal button

32
Q

What chemical messenger (neurotransmitter) is released when an action potential reaches the terminal button?

A

acetylcholine

33
Q

In a neuromuscular junction what leads to the generation of end plate potential?

A

the release of Ach

34
Q

What is an end plate potential responsible for?

A

muscle contraction

35
Q

where is the action potential initiated?

A

axon hillock

36
Q

What happens when the action potential at the axon terminal reaches the terminal button?

A

it brings about a conformational change in the voltage gated calcium channels in the terminal button, therefore opening them

37
Q

When the VG calcium channels open as a result of the action potential what happens?

A

Calcium is usually more concentrated outside, so calcium rushes into the cell (influx) at the terminal button, when the calcium comes into the cell, exocytosis of Ach from the terminal button is initiated

38
Q

When Ach is released from the terminal button what happens?

A

Ach diffuses through the space between the nerve cell and muscle cell and binds to receptor sites on the motor end plate of the muscle cell, which produces a local current flow that opens adjacent sodium channels in the motor end plate, the electrical gradient of sodium favors the inside so it goes into the muscle cell resulting in initiation of a small depolarization (graded potential)

39
Q

After graded potentials in the motor end plate summate and cause an action potential through the muscle fiber, how is the process stopped?

A

acetylcholinesterase (AChe) terminate the activity of Ach at the nerumuscular junction (NMJ)

40
Q

How is the neuromuscular junction similar to synapses?

A

It is an important drug target because it is vulnerable to chemical agents and diseases

41
Q

What is acetylcholinesterase

A

a membrane bound enzyme that destroys floating Ach -> rapid hydolysis

42
Q

What are some things that affect neuromuscular junctions?

A

Toxins (black widow spider venom, botulinum toxin)
Curare
Organophosphates
Myasthenia gravis

43
Q

What do toxins do?

A

they alter the release of Ach causing respiratory (diaphragm) failure

44
Q

What is the toxic effect of black widow spider venom?

A

explosive release of Ach (think spider man exploding web)

45
Q

What is the toxic effect of botulinum toxin?

A

Blocks release of Ach

- food poisoning - food not stored properly can create botulinum toxin

46
Q

What happens when Ach is explosively released?

A

too much Ach release can cause continuous influx of sodium ions, even though potassium is leaving the cell, sodium keeps coming in other channels, not allowing the membrane to get back to -70 mV making the muscle unresponsive

47
Q

What happens if there is too much ach in the diaphragm (respiratory muscle)?

A

the diaphragm stays in contraction

48
Q

What happens if Ach is released?

A

If the diaphragm does not receive Ach, it will be unable to contract, so inhalation and exhalation will not be possible

49
Q

How does curare effect the neuromuscular junction?

A

it blocks ach receptors at the motor end plate

  • if animals are shot with curare arrows they become immobile and are easily hunted
  • Ach receprots are blocked so even if Ach is released there is no action potential and one dies of respiratory failure
50
Q

How do organopohsphates effect neuromuscular junctions

A

organophosphates are insecticides and pesticides
- they irreversibly inhibit acetylcholinesterase (AChE), so Ach levels will rise which has a similar effect as black widow spider venom

51
Q

What is myasthenia gravis?

A

loss of Ach receptors at motor end plate, so action potentials can’t be generated
- auto- immune disease, causes extreme muscular weakness

physio exam 3 (6 decks)

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