The Sympathetic NS Flashcards

1
Q

What is the somatic system responsible for?

A

voluntary movement e.g. writing, running, walking and talking

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2
Q

What is the autonomic system responsible for?

A

controlling organs in the body (involuntary)

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3
Q

What is the autonomic NS divided into?

A

sympathetic and parasympathetic nervous systems

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4
Q

Give examples of systems under autonomic control

A

visceral reactions e.g. food digestion and eye dilation

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5
Q

Where is the hypothalamus located?

A

at the bottom of the diencephalon

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6
Q

What does the hypothalamus do?

A
  • secrete hormones from the pituitary gland that act on the endocrine glands of the body
  • send projections down the spinal cord to control the sympathetic and (in part) parasympathetic nervous systems
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7
Q

What is the hypothalamus sensitive to?

A

the blood flowing through it

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8
Q

What 3 tissue types does the ANS stimulate?

A
  • cardiac muscle
  • smooth muscle
  • glands
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9
Q

How is the balance between the parasympathetic and sympathetic nervous systems maintained?

A

by increasing the amount of stimulation in one part of the system or decreasing the amount of discharge in the other

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10
Q

When does the sympathetic NS dominate?

A

when a person is in a stressful situation; the body reacts by preparing for ‘fight or flight’

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11
Q

What happens to the body under stress due to the sympathetic NS?

A
  • muscles work harder and need more oxygen and energy
  • one breathes faster and the bronchi and bronchioles open up for greater and quicker passage of air
  • the heart beats stronger and faster
  • the arteries to the heart and voluntary muscle dilate to increase blood flow
  • the arteries to the skin and other peripheral areas constrict
  • the liver secretes glycogen for quick supply of energy and the GI tract slows down
  • pupils dilate
  • one sweats to reduce elevated body temperature
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12
Q

What is cardiac output?

A

the amount of blood pumped by the heart per minute

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13
Q

What is the outflow of the sympathetic NS based on?

A

a two-neuron motor pathway consisting of preganglionic and postganglionic neurons

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14
Q

Where are the preganglionic neuron cell bodies located?

A

in the intermediolateral horn of T1 to L2 spinal segments; the thoracolumbar outflow

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15
Q

How do the preganglionic axons leave the spinal cord?

A

via the ventral roots into the sympathetic (chain) trunk

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16
Q

What is the sympathetic trunk?

A

a series of ganglia and axon fibres on each side of the vertebral column

17
Q

What is the chemical transmitter between the postganglionic sympathetic axons and the structures they innervate?

A

mostly noradrenaline and, in some cases, adrenaline

18
Q

What is adrenaline and noradrenaline used in hospitals for?

A
  • falling blood pressure and cardiac arrest
  • to counteract anaphylactic shock
  • to dilate the bronchioles in acute asthma
19
Q

Where are cell bodies of the sympathetic nerves that supply the heart?

A

in the intermediolateral horn of T1-T5 spinal segments

20
Q

What do postsynaptic sympathetic fibres that innervate the heart arise from?

A

the cervical and superior thoracic ganglia of the sympathetic trunks

21
Q

Where do the postsynaptic sympathetic fibres that innervate the heart go?

A

across cardiopulmonary splanchnic nerves and the cardiac plexus to end in the SA and AV nodes

22
Q

What does stimulation of the SA node and conducting tissue do?

A

increase the rate of depolarisation of the pacemaker cells while increasing atrioventricular conduction

23
Q

What does direct adrenergic stimulation from sympathetic nerve fibres to the heart do?

A

increase atrial and ventricular contractility

24
Q

What do chromaffin cells do?

A

secrete more adrenaline into the blood via the CNS to increase heart rate

25
Q

What are most adrenergic receptors on coronary blood vessels and what do they do?

A

β2-receptors, which, when activated, causes relaxation of vascular smooth muscles, and therefore, dilation of the arteries

26
Q

What do sympathetic nerves that supply the lungs arise from?

A

cell bodies that are located on the T1-T5 paravertebral sympathetic ganglia of the sympathetic trunks

27
Q

What do the sympathetic nerves travel through?

A

the pulmonary plexuses which are located posterior to the roots of the lungs

28
Q

What are the effects of the sympathetic supply to the lungs?

A
  • dilation of bronchial muscle (bronchodilator) which increases oxygen intake
  • inhibition to the glands of the bronchial tree which decreases secretion from the glands
  • vasoconstriction to bronchial vessels (not pulmonary vessels)
29
Q

What happens when the glands of the bronchial tree are activated?

A

they secrete mucus and other enzymes and hormones to essentially lubricate the bronchial tree but under stress, these processes must be cut off to conserve energy

30
Q

Where are the sympathetic nerves that supply the abdominal viscera found?

A

in the lateral horn of the thoracic segments T5-T12

31
Q

Where are the sympathetic nerves that supply the pelvic organs found?

A

L1-2

32
Q

Where do the preganglionic axons from T5 to L1/2 synapse?

A

onto postganglionic neurons outside of the trunk in the pre-aortic ganglia located in front of the abdominal aorta

33
Q

What do the postganglionic axons do?

A

“hitch a ride” on the arteries until they reach the glands or smooth muscle to innervate them

34
Q

What do some postganglionic axons do at the adrenal gland?

A

synapse on the cells in the adrenal medulla and release adrenaline intro the bloodstream via chromaffin cells to amplify the sympathetic response

35
Q

What does sympathetic supply of the male internal genital organs do?

A

cause contraction and initiate ejaculation

36
Q

What does sympathetic supply of the female internal genital organs do?

A

cause uterine contraction only in non-pregnant females; in pregnant females, the adrenergic receptors in the uterus switch from beta to alpha to prevent these contractions

37
Q

What does the sympathetic NS in the neck supply?

A
  • the muscle of the upper eyelid (levator palpebrae superioris)
  • dilator pupillae of the eye
  • the skin of the face and neck
38
Q

What can damage to the sympathetic NS result in?

A

Horner’s syndrome

39
Q

What is Horner’s syndrome characterised by?

A

deeply sunken eyes, droopy eyelids and lack of focus as well as flushing of the skin and absence of sweating on the affected side of the face and neck