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A&P Class > UNIT 5 AUTONOMIC NERVOUS SYSTEM > Flashcards

UNIT 5 AUTONOMIC NERVOUS SYSTEM Flashcards

1
Q

Intoduction to the ANA (Autonomic nervous system)

A

●The autonomic nervous system (ANS) is a motor subdivision of the peripheral nervous system (PNS).

●It has two divisions:
◦ parasympathetic division
◦ sympathetic division

●Generally the two divisions have opposite effects.

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2
Q

Functions of ANS

A

Function:
●Helps regulate activity of body organs that are not under voluntary control

●Plays major role in stabilizing internal environment.

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3
Q

Effectors of ANS

A

Effectors:
●smooth muscle
●cardiac muscle
●glands

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4
Q

Two neurons in ANS Motor pathway - 1

A
  1. preganglionic neuron

▪ cell body is located in gray matter of brain or spinal cord

▪ axon synapses with a second (postganglionic) neuron within a ganglion outside of the CNS

▪ thin, lightly myelinated fibers

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5
Q

Two neurons in ANS Motor pathway- 2

A
  1. Postganglionic neuron
    ▪ receives nerve impulse from preganglionic neuron

▪ cell body is located in a ganglion

▪ axon extends from ganglion to the effector organ where it synapses with
cells of the effector organ

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6
Q

Additional notes on motor pathway

A

▪ Many pre-ganglionic and post-ganglionic fibers (axons) are incorporated into spinal or cranial nerves.

▪ Conduction in autonomic motor chain is slower than conduction in somatic motor pathway. (There is less myelination of the autonomic motor pathway.)

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7
Q

Autonomic Ganglion

A

●A cluster of cell bodies outside the CNS that serves as the location where a preganglionic neuron synapses with a postganglionic neuron.

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8
Q

Types of Autonomic Ganglia

A

3 types:
-Paravertebral ganglia
-Collateral ganglia
-Terminal ganglia

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9
Q
  1. Paravertebral ganglia
    = sympathetic chain ganglia
A

▪ a chain of ganglia on either side of the vertebral column
▪ site where most neurons of sympathetic division synapse

(Also called sympathetic trunk)

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10
Q
  1. Collateral ganglia
A

▪ located anterior to vertebral
column but still relatively
close to it
▪ not part of a chain
▪ synapse site for some of sympathetic division

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11
Q
  1. Terminal ganglia
A

▪ located next to or in the wall of the effector organ; farthest from vertebral column

▪ site where neurons of parasympathetic division synapse

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12
Q

Innervation of effectors

A

Dual innervation & innervation by one division

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13
Q

Dual innervation

A

Most effectors are innervated by both sympathetic
& parasympathetic divisions.

  • Each division releases a different neurotransmitter to the effector which accounts for the different effects produced by the two divisions.
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14
Q

Innervation by one division

A

A few effector organs are only innervated by the sympathetic division.

▪ sweat glands ▪ adrenal medulla ▪ arrector pili muscles

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15
Q

Parasympathetic Division - Introduction

A

●Division in control when we are in “rest & digest” mode

●Active when the sympathetic system is inactive

●It is energy-conserving

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16
Q

Parasympathetic Divisions - Characteristics

A

Craniosacral division
- Preganglionic neuron
- Postganglionic neuron
- Parasympathetic ganglia
- Little divergence of PNS fibers
- Neurotransmitter released

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17
Q

Craniosacral division - parasympathetic

A

Preganglionic axons arise from the brain and from the sacral region of the spinal cord.

Vagus nerve – most important parasympathetic nerve; supplies heart, lungs, GI tract, pancreas, etc.

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18
Q

Preganglionic neuron - parasympathetic

A

▪ Body is in one of nuclei in brain or in gray matter of spinal cord
▪ Axon travels over a cranial nerve or spinal nerve to reach postganglionic neuron

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19
Q

Postganglionic neuron

A

▪ Body is in terminal ganglion
▪ Axon extends to effector

20
Q

Parasympathetic ganglia

A

▪ Pre- & postganglionic neurons of parasympathetic division synapse in terminal ganglia.

▪ In general, these ganglia are located the farthest away from the spinal cord.

21
Q

Little divergence of PNS fibers - parasympathetic division

A

▪ Preganglionic fibers exhibit minimal branching; therefore, individual parasympathetic nerves can be stimulated.

▪ So, parasympathetic division is not necessarily activated as a whole; it can exert localized control over effectors.

22
Q

Neurotransmitter released - parasympathetic

A

▪ Preganglionic & postganglionic neurons both release acetylcholine (ACh).

Note:
ACh is rapidly inactivated by acetylcholinesterase
→ Therefore, the parasympathetic system produces short-term effects.

23
Q

Sympathetic Division - Introduction

A

●Division that is responsible for “fight-or-flight”.

●Activated during times of stress, emergency, excitement, or exercise.

●It is energy-consuming.

24
Q

Sympathetic division- characteristics

A

“Thoraco- lumbar” division

Preganglionic neuron:
▪ Body is in lateral horn of thoracic or lumbar region of spinal cord
▪ Axon extends to postganglionic neuron

Postganglionic neuron:
▪ Body is in ganglion of sympathetic
chain or in a collateral ganglion
▪ Axon extends to effector.

25
Q

Sympathetic division chracteristics

A

Sympathetic ganglia:
▪ Pre- & postganglionic neurons of sympathetic division synapse in either:
◦ sympathetic chain ganglia or
◦ collateral ganglia

▪ In general, sympathetic
ganglia are located close to
spinal cord.

26
Q

Possibilities at sympathetic Chain

A

All preganglionic sympathetic neurons enter the sympathetic chain and then 1 of 3 things happen:

1) Preganglionic axon enters chain and synapses at that same level

27
Q

Possibilities at sympathetic chain - 2

A

2) Preganglionic axon enters chain, but then travels up or down to synapse at higher or lower level.

28
Q

Possibilities at sympathetic chain

A

3) Preganglionic axon passes through chain without synapsing; synapse will occur out at a collateral ganglion.

29
Q

Divergence of fibers in ganglion - sympathetic di

A

In the sympathetic nervous system, a preganglionic axon can branch to synapse with many postganglionic neurons located at different levels in the sympathetic chain.

30
Q

Result if divergence of fibers in ganglion - sympathetic

A

→ allows impulses from one preganglionic fiber to affect many postganglionic fibers.

→ contributes to “mass action” of the
sympathetic division; sympathetic division is activated as a whole.

31
Q

Neurotransmitters released - sympathetic division

A

◦ preganglionic neuron – acetylcholine

◦ postganglionic neuron – norepinephrine
(noradrenaline)
Note:
Norepinephrine has a longer-lasting effect
than the ACh released to effectors by the parasympathetic division.

32
Q

Adrenal medulla

A

▪ The adrenal medulla (central portion of adrenal gland) is innervated by preganglionic sympathetic neurons.

▪ It secretes epinephrine and norepinephrine when the sympathetic division is activated.

▪ In this way, the adrenal medulla is really an extension of the sympathetic division, so the sympathetic division plus the adrenal medulla is termed the “sympathoadrenal system”.

33
Q

Effects of sympathetic division

A

On Cardiovascular System:

▪ causes heart to beat faster & stronger
▪ dilates blood vessels supplying blood to heart & skeletal muscles
▪ constricts blood vessels supplying blood to the digestive system and kidneys

34
Q

Effects of sympathetic division

A

On Respiratory System:

▪ dilates bronchioles to allow more air flow

35
Q

Effects of sympathetic division

A

On Digestive System:

▪ decreases activity of glands and smooth muscle in walls
▪ causes liver to release glucose into the blood

36
Q

Effects of sympathetic division - other effects SDCIMRIMAIUFV

A

▪ sweating
▪ dilation of the pupil
▪ contraction of the arrector pili muscles
▪ increases metabolic rate
▪ increases mental alertness
▪ inhibits urine formation & voiding

37
Q

Effects of parasympathetic division

A

On Cardiovascular System:

▪ slows and steadies heart rate
▪ dilates blood vessels supplying blood to the digestive system and kidneys

38
Q

Effects of parasympathetic division

A

On Respiratory System:
▪ constricts bronchioles

39
Q

Effects of parasympathetic division

A

On Digestive System:
▪ increases activity of digestive system and associated glands

40
Q

Effects of parasympathetic division

A

Other Effects:
▪ constricts pupil
▪ promotes voiding of urine

41
Q

Cholinergic fibers

A

▪ axons that release acetylcholine as the neurotransmitter

42
Q

Adrenergic fibers

A

▪ axons that release norepinephrine (noradrenaline) as the neurotransmitter

43
Q

Cholinergic receptors = acetylcholine- binding receptors.

A

Two types:

▪ nicotinic receptors – effect of ACh binding these receptors is always stimulatory

▪ muscarinic receptors – effect of ACh binding these receptors may be inhibitory or stimulatory

44
Q

Adrenergic receptors = norepinephrine- binding receptors.

A

Two classes:

▪ alpha (α) receptors
◦ α1
◦ α 2
▪ beta (β) receptors
◦ β 1
◦ β 2
◦ β 3

45
Q

Control of the ANS( Autonomic nervous system)

A

The ANS is regulated by portions of the CNS located in the:
▪ spinal cord
▪ brain stem
▪ hypothalamus - primarly regulator of ANS
▪ cerebral cortex

46
Q

End :)

A

End :)

A&P Class (11 decks)

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