NERVOUS SYSTEM: CENTRAL CONTROL OF AUTONOMIC FUNCTION

Question 1

Define: referred pain?

Answer 1

pain felt in one location but the source of the pain may be somewhere else.

Question 2

Describe the general functions of the autonomic nervous system (ANS) and name its two major divisions.

Answer 2

• Controls cardiac and smooth muscles, endocrine glands, GI system
• sympathetic and parasympathetic

Question 3

How do the sympathetic and parasympathetic preganglionic cell bodies differ in terms of
- location
- neurotransmitter

Answer 3

sympathetic preganglionic cell body
- thoracolumbar spinal cord
- ACh

Parasympathetic preganglionic cell body
- craniosacral
- ACh

Question 4

How do the sympathetic and parasympathetic postganglionic cell bodies differ in terms of
- location
- neurotransmitter

Answer 4

sympathetic postganglionic cell bodies
- close to vertebrae and far from target
- norepinephrine

parasympathetic post ganglionic cell bodies
- near to or within wall of organ target location
- ACh

Question 5

How do preganglionic efferents and post ganglionic efferents differ?
- Cell type
- fiber dimeter
- conduction velocity

Answer 5

pre ganglionic efferents are type B fibers
- fiber diameter is 0.21 - 33 um
- conduction velocity is 3-15 m/s

post ganglionic efferents are type C fibers
- fiber diameter is 0.2-2um
- conduction velocity is 0.5-2m/s

Question 6

Explain an autonomic sympathetic reflex from the visceral general afferent to the digestive tube

Answer 6

• Visceral general afferents release excitatory neurotransmitters on preganglionic cells concentrated in the lateral horn.
• Preganglionic fibres exit the spinal cord via ventral root and enter paravertebral ganglia in the same level.
• Exit spinal cord via ventral root and enter paravertebral ganglia at the same level
  
  • Some synapse here
  • Some give off collaterals that travel rostrally or caudally
  • Some pass through the ganglia and enter a splanchnic nerve to travel to a prevertebral ganglia. Splanchnic nerves are mixed nerves that innervate the viscera
• Splanchnic nerve contains both postganglionic fiber and visceral sensory fiber

Question 7

How do sympathetic reflexes in the autonomic nervous system differ from the somatic nervous system?

Answer 7

• reflexes involve 2 neuron efferent pathway
• afferents are known as general visceral afferents

Question 8

Describe what adrenergic receptor type is located at the ciliary muscle and what response sympathetic stimulation elicits

Answer 8

a type

pupil dilation (mydriasis); enhancing far vision

Question 9

Describe what adrenergic receptor type is located at the heart muscle and what response sympathetic stimulation elicits

Answer 9

B1

acts on SA node and ventricles increased heart rate, increased contractility

Question 10

Describe what adrenergic receptor type is located at the stomach and what response sympathetic stimulation elicits

Answer 10

a, and B2

decreased motility, sphincter contraction, reduced secretions

Question 11

Describe what adrenergic receptor type is located at the small intestine and what response sympathetic stimulation elicits

Answer 11

a, B2

decreased motility, sphincter contraction, reduced secretions

Question 12

Describe what adrenergic receptor type is located at the lungs and what response sympathetic stimulation elicits

Answer 12

B2

bronchodilation, increased ventilation

Question 13

Describe what adrenergic receptor type is located at the abdominal arterioles and what response sympathetic stimulation elicits

Answer 13

a, B2

constriction and diversion of blood from GI tract to muscles

Question 14

What are the key differences between parasympathetic reflexes and sympathetic reflexes

Answer 14

parasympathetic reflexes
- cell bodies of presynaptic neurons are in cranial nerves III, VII, IX, X and sacral spinal cord S2, S3, S4

• post synaptic neurons are located in ganglia near or even in wall of target organ
• not present in smooth muscles of most blood vessels (primarily sympathetic innervation)

Question 15

Describe what muscarinic receptor type is located at the ciliary muscles and what response parasympathetic stimulation elicits

Answer 15

M3
- contraction for near vision

Question 16

Describe what muscarinic receptor type is located at the salivary and lacrimal glands and what response parasympathetic stimulation elicits

Answer 16

M3 - increased secretions

Question 17

Describe what muscarinic receptor type is located at the heart and what response parasympathetic stimulation elicits

Answer 17

M2

decreased heart rate and contractility

Question 18

Describe what muscarinic receptor type is located at the stomach and intestine and what response parasympathetic stimulation elicits

Answer 18

M1, M2, M3
Increased secretions, increased motility, sphincter relaxation

Question 19

Describe what muscarinic receptor type is located at the lungs and what response parasympathetic stimulation elicits

Answer 19

M3
brochoconstriction

Question 20

Describe what muscarinic receptor type is located at the abdominal arterioles and what response parasympathetic stimulation elicits

Answer 20

M3
vasodilation

Question 21

Describe what muscarinic receptor type is located at the bladder and what response parasympathetic stimulation elicits

Answer 21

M2, M3
sphincter relaxation

Question 22

What are the components of the pathways that control firing of the autonomic nervous system?

Answer 22

Spinal reflex arcs, brainstem reflex pathways, and descending controls from the hypothalamus

Question 23

What 3 regions regulate autonomic function

Answer 23

hypothalamus, preoptic and septal regions

Question 24

hypothalamus function

Answer 24

regulates body temperature, hunger and thirst, mood, sex drive, blood pressure, and sleep

Question 25

How does the heat loss centre of the hypothalamus respond if we are too warm?

Answer 25

decrease in thyroid activity,

sweat

vasodilation

Question 26

How does the heat conservation centre respond if we are too cold?

Answer 26

shivering, piloerection, increase in thyroid activity

Question 27

Describe the location of the heat loss centre and what a lesion to these areas would cause

Answer 27

• preoptic center and anterior hypothalamus
• prevent sweating and cutaneous vasodilation
• leads to hyperthermia

Question 28

Describe the location of the heat conservation centre and what a lesion to these areas would cause

Answer 28

• posterior hypothalamus
• hypothermia

Question 29

What happens in the hypothalamus when blood glucose levels drops?

Answer 29

glucoreceptors activate

Question 30

What happens if there is damage to the lateral hypothalamus?

Answer 30

aphagia (suppressed food intake - inability to swallow)

can cause starvation and death

Question 31

What happens if there is damage to the ventromedial area of the hypothalamus

Answer 31

it is the satiety centre.

results in hyperphagia (insatiable appetite), can lead to obesity

Question 32

What causes syphilis

Answer 32

bacteria called treponema pallidum

Question 33

Describe the primary, secondary, tertiary stages of syphilis

Answer 33

primary (days-weeks): single sore (chancre)

secondary (months): body, hands, feet, rash

tertiary (years-decades): neurological, cardiovascular, gummas, Argyll Robertson Pupil

Question 34

Define: gummas

Answer 34

soft swelling of brain, liver, testes, heart

Question 35

Define: Argyll Robertson Pupil

Answer 35

Pupil does not react to light but accommodation reflex is still normal;

Due to damage of the optic nerves in the pretectal area by bacteria

Question 36

define: micturition

Answer 36

the act of urination

Question 37

Describe the micturition reflex including the neurotransmitters, receptors, and intracellular signalling pathway

Answer 37

• Involves spinal reflex and descending input from a supraspinal centre
• sympathetic input: norepinephrine is released onto B adrenergic receptors of detrusor resulting in inhibition and on a adrenergic receptors on internal sphincter resulting in activation
• detrusor muscle contracts during urination to push urine out of bladder
• the external sphincter which is controlled voluntarily (somatic innervation - pudendal nerve), contracts to pee
• parasympathetic input originating from sacral nerve 1, 2, 3: ACh releases onto muscarinic receptors on urinary bladder and internal sphincter. results in urinary bladder contracting and internal sphincter relaxing