UNIT 5 AUTONOMIC NERVOUS SYSTEM

Question 1

Intoduction to the ANA (Autonomic nervous system)

Answer 1

●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.

Question 2

Functions of ANS

Answer 2

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

●Plays major role in stabilizing internal environment.

Question 3

Effectors of ANS

Answer 3

Effectors:
●smooth muscle
●cardiac muscle
●glands

Question 4

Two neurons in ANS Motor pathway - 1

Answer 4

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

Question 5

Two neurons in ANS Motor pathway- 2

Answer 5

2. 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

Question 6

Additional notes on motor pathway

Answer 6

▪ 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.)

Question 7

Autonomic Ganglion

Answer 7

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

Question 8

Types of Autonomic Ganglia

Answer 8

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

Question 9

1. Paravertebral ganglia
   = sympathetic chain ganglia

Answer 9

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

(Also called sympathetic trunk)

Question 10

2. Collateral ganglia

Answer 10

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

Question 11

3. Terminal ganglia

Answer 11

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

▪ site where neurons of parasympathetic division synapse

Question 12

Innervation of effectors

Answer 12

Dual innervation & innervation by one division

Question 13

Dual innervation

Answer 13

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.

Question 14

Innervation by one division

Answer 14

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

▪ sweat glands ▪ adrenal medulla ▪ arrector pili muscles

Question 15

Parasympathetic Division - Introduction

Answer 15

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

●Active when the sympathetic system is inactive

●It is energy-conserving

Question 16

Parasympathetic Divisions - Characteristics

Answer 16

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

Question 17

Craniosacral division - parasympathetic

Answer 17

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.

Question 18

Preganglionic neuron - parasympathetic

Answer 18

▪ 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

Question 19

Postganglionic neuron

Answer 19

▪ Body is in terminal ganglion
▪ Axon extends to effector

Question 20

Parasympathetic ganglia

Answer 20

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

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

Question 21

Little divergence of PNS fibers - parasympathetic division

Answer 21

▪ 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.

Question 22

Neurotransmitter released - parasympathetic

Answer 22

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

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

Question 23

Sympathetic Division - Introduction

Answer 23

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

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

●It is energy-consuming.

Question 24

Sympathetic division- characteristics

Answer 24

“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.

Question 25

Sympathetic division chracteristics

Answer 25

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.

Question 26

Possibilities at sympathetic Chain

Answer 26

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

Question 27

Possibilities at sympathetic chain - 2

Answer 27

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

Question 28

Possibilities at sympathetic chain

Answer 28

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

Question 29

Divergence of fibers in ganglion - sympathetic di

Answer 29

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

Question 30

Result if divergence of fibers in ganglion - sympathetic

Answer 30

→ 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.

Question 31

Neurotransmitters released - sympathetic division

Answer 31

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

Question 32

Adrenal medulla

Answer 32

▪ 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”.

Question 33

Effects of sympathetic division

Answer 33

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

Question 34

Effects of sympathetic division

Answer 34

On Respiratory System: ▪ dilates bronchioles to allow more air flow

Question 35

Effects of sympathetic division

Answer 35

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

Question 36

Effects of sympathetic division - other effects SDCIMRIMAIUFV

Answer 36

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

Question 37

Effects of parasympathetic division

Answer 37

On Cardiovascular System: ▪ slows and steadies heart rate ▪ dilates blood vessels supplying blood to the digestive system and kidneys

Question 38

Effects of parasympathetic division

Answer 38

On Respiratory System: ▪ constricts bronchioles

Question 39

Effects of parasympathetic division

Answer 39

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

Question 40

Effects of parasympathetic division

Answer 40

Other Effects: ▪ constricts pupil ▪ promotes voiding of urine

Question 41

Cholinergic fibers

Answer 41

▪ axons that release acetylcholine as the neurotransmitter

Question 42

Adrenergic fibers

Answer 42

▪ axons that release norepinephrine (noradrenaline) as the neurotransmitter

Question 43

Cholinergic receptors = acetylcholine- binding receptors.

Answer 43

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

Question 44

Adrenergic receptors = norepinephrine- binding receptors.

Answer 44

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

Question 45

Control of the ANS( Autonomic nervous system)

Answer 45

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

Question 46

End :)

Answer 46

End :)