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Circulation and Breathing > The Nervous System > Flashcards

The Nervous System Flashcards

1
Q

What are the 5 parts of the nervous system?

A

1) Brain
2) Spinal cord
3) Peripheral nerves
4) Automonic nervous system - to organs
5) Enteric nervous system - for motility and secretion from GI tract

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2
Q

What does the autonomic nervous system control?

A

Regulates cardiac muscle, smooth muscle, exocrine glands, neurones of the gut.
Everything except from skeletal muscle and bone.

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3
Q

What controls the autonomic nervous system?

A

It is innervated by the sympathetic and parasympathetic pathways.
Responsible for passing impulses from neurone to neurone via ganglia or neurone to effector. Only passes impulses from CNS to the effector.

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4
Q

What does the peripheral nervous system control?

A

Regulates only skeletal muscle and bone.

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5
Q

What is the afferent (arriving) part of the peripheral nervous system?

A

The sensory system consists of exteroreceptors (external stimuli) and interoreceptors (interior stimuli).
Takes nervous impulse to the CNS.

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6
Q

What is the efferent (exiting) part of the peripheral nervous system?

A

The somatomotor system innervates slow twitch and fast twitch muscle. It is independent of the autonomic nervous system and is only excitatory.

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7
Q

Where are the synapses in the autonomic nervous system?

A

There is always a synapses(apart from with the adrenal medulla) between the preganglionic neurone that arises from the CNS and post ganglionic neurone that arises from the ganglia and activates the target organ.

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8
Q

How does the position of the ganglia in the autonomic nervous system differ?

A

If the action of the neurone is sensory the ganglia is usually closer to the spine.
If the action of the neurone is to an effector and has a motor effect then the ganglia is closer to the effector organ.

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9
Q

Where do the neurones that are part of the sympathetic pathway arise from?

A

They arise in the ventral roots of the thoracic and lumbar segments.

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10
Q

Where do neurones that are part of the parasympathetic pathway arise from?

A

They arise in the ventral roots of the cranial and sacral segments.

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11
Q

What part of the nervous system controls the GI tract?

A

The enteric nervous system.

There are more neurones in the GI tract than in the spinal cord!

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12
Q

List 4 differences between the autonomic and somatic nervous system

A

1) Autonomic efferent fibres do not pass directly to effectors, but synapse at autonomic ganglia. (Apart from adrenal medulla). Somatic efferent fibres only have 1 neurone.
2) Autonomic system is involuntary, somatic system is voluntary.
3) Autonomic system is excitatory and inhibitory, somatic system is only excitatory.
4) MOST autonomic neurones are nonmyelinated, MOST somatic neurones are myelinated.

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13
Q

Where are all sensory nerves (receptor to CNS) located?

A

In the dorsal roots

sensory

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14
Q

Where are all motor nerves (CNS to effector) located?

A

In the ventral roots

autonomic and somatic

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15
Q

What are ganglions?

A

Swellings on all autonomic nerves (apart from adrenal medulla). Neuronal cell bodies are found in the ganglion. Also contains the synapse between pre and post ganglionic neurones.

Pre ganglionic nerves are myelinated = white rami. Allows fast transmission from CNS to ganglion.
Post ganglionic nerves are non myelinated = grey rami. Means that transmission from ganglion to effector is quite slow.

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16
Q

Describe where the sympathetic pathway is innervated from in the spine

A

Cell bodies are concentrated in the interomediolateral column (lateral horn). There are left and right outputs of the thoracic and lumbar segments.
Medial organs are innervated by both left and right nerves.
Organised viscerotopically - organs located higher in the body are innervated from higher in the spinal cord.

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17
Q

Describe the sympathetic pathway route

A

Preganglionic neurone from thoracic and lumbar regions of the spine located in the lateral horn.
They connect to the sympathetic ganglia via the ventral route. They are myelinated.
The post ganglionic neurones project from ganglia to the target - smooth/cardiac muscle, glands. Have extensive branching so there are multiple points of contact with the target.

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18
Q

Describe the parasympathetic route

A

Preganglionic neurone from specific cranial nerve nuclei or sacral spine lateral horns. They project towards their target with lots go branching, especially in the vagus nerve!
They connect to the parasympathetic ganglia that are located close to or are embedded in the target(heart and lungs). They are widespread and localised.
Postganglionic neurones have very short axons and minimal branching. From parasympathetic ganglia to the effector - smooth/cardiac muscle or glands.

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19
Q

Describe where the parasympathetic pathway is innervated from the spine

A

Only 4 nerves carry output from intermediolateral column in the sacral segments.
The cranial nerves are the 3, 7, 9, and 10.
10th is the Vagal and Ambiguus nuclei (thoracic and abdominal organs).

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20
Q

What is meant by sympathetic divergence?

A

Ganglion is closer to the CNS so nerves can spread further for widespread innervation.
One preganglionic neurone synapses with multiple ganglia so multiple post ganglionic neurones are stimulated. These can act on individual target organs.

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21
Q

What is meant by parasympathetic divergence?

A

Ganglion is closer to target so nerves diverge closer to target so there is focussed excitation.
One preganglionic neurone will synapse with multiple ganglia so multiple post ganglionic neurones are stimulated that are very close to the effector organ.

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22
Q

What is meant by convergence?

A

Multiple inputs can converge to a specific target, which can help to integrate CNS outflow and direct to one target.
Allows different parts of the spinal cord to control a different target organ.

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23
Q

How is the adrenal medulla different to other autonomic nerves?

A

The adrenal medulla is directly innervated by a sympathetic pre ganglionic nerve. No ganglion present.
The cells of the adrenal medulla are like neurones, they release noradrenaline and adrenaline into the bloodstream.

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24
Q

What are varicosities?

A

The synaptic contact between the post ganglionic neurones of the sympathetic nervous system through specialised structures = varicosities.
They are swellings along the axon that can release neurotransmitters.
Allows more points of contact between sympathetic nervous system and their targets.
Process = volume transmission

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25
Q

What neurotransmitter is used at the preganglionic synapses (neurone to neurone) for the sympathetic and parasympathetic pathways?

A

Acetylcholine - excites ganglia, adrenal medulla, skeletal muscle.
ATP (cotransmitter) - excites ganglia, adrenal medulla.

MEANS THAT postganglionic neurone has receptors for ACh and ATP.

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26
Q

What neurotransmitter is used at the postganglionic synapse (neurone to effector) for the sympathetic pathway?

A

Noradrenaline (sometimes Acetylcholine is used in the sweat glands)

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27
Q

What neurotransmitter is used in the postganglionic synapse (neurone to effector) for the parasympathetic pathway?

A

Acetylcholine

effector has ACh receptors

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28
Q

What neurotransmitter is used in the preganglionic neurone synapse to the adrenal medulla?

A

Noradrenaline, Adrenaline

effector has NorAdr and Adr receptors

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29
Q

Outline the changes of energy that occur at a synapse

A

Neurotransmitter released = chemical energy
Receptors activated = mechanical energy
Membrane potential changes = electrical energy

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30
Q

What type of receptors are present in all autonomic ganglia?

A

Nicotonic receptors.
These are ligand gated ion channels.
Activated by ACh and alkaloid nicotine.

31
Q

What type of receptors are present in parasympathetic targets?

A

Muscarinic receptors.
These are G protein coupled receptors.
Activated by ACh and muscarine.

32
Q

What type of receptors are present in sympathetic targets?

A

Adrenoreceptors (alpha and beta).
These are G protein coupled receptors.
Activated by adrenaline and noradrenaline.

33
Q

What drugs can be used on the nicotine receptors on the ganglion?

A

Hexamethonium

34
Q

What drugs can be used on the muscarinic receptors?

A

Atropine

35
Q

What drugs can be used on adrenoreceptors?

A

Phentolamine (for alpha receptors)

Propranlol (beta blocker for beta receptors on the heart)

36
Q

What drugs can used to regulate levels of cAMP (therefore regulates the heart rate as cAMP activated PKA for Ca2+ channels)

A

Phosphodiesterase inhibitors, Sildenafil

inhibits PDE-5

37
Q

The pacemaker frequency of the heart is 100bpm but resting rate is 70bpm. What explains this?

A

Means that thee must be more parasympathetic activity involved is maintaining the resting heart rate. (parasympathetic pathway slows down the heart rate).

38
Q

How is the heart rate determined by the pacemaker cells in the SAN and AVN?

A

First hyper polarisation of the membrane occurs. This is determined by the Ifunny current.
The Ifunny current is driven by the concentration of cAMP, and this depends on which receptors are activated.
The sympathetic nervous system activates beta 1 adrenoreceptors. This increases the production of cAMP, so depolarisation of pacemaker cells occurs quickly, so faster heart rate.
The parasympathetic nervous system activates M2 muscarinic receptors . This decreases the production of cAMP so depolarisation of pace maker cells occur slowly, so slower heart rate.

39
Q

How is vasculature controlled by the ANS?

A

Vasculature is primarily controlled by the sympathetic pathway. Increased frequency of action potentials result in more noradrenaline being released to the alpha receptors. More NAdr = more constriction. If ACh present afterwards then vasodilation occurs.
Less NAdr = less constriction (more dilation)

Parasympathetic pathway only innervates the coronary vessels and genitalia. These have muscarinic receptors that respond to ACh. Activation of these causes vasodilation.
(blood vessels still have muscarinic receptors but aren’t of use).

40
Q

What is the function of the cerebrum diencephalon?

A

Generates the pattern of cardiovascular response depending on different behaviours.

41
Q

Where does the parasympathetic activity for the heart originate from?

A

The vagus nerve from the brainstem.

42
Q

Where does sympathetic activity for the heart and vascular smooth muscle originate from?

A

The T1-L3 sympathetic outflow from the spinal cord.

43
Q

What happened to blood pressure during the night?

A

Blood pressure decreases at night as when lying down it is easier for the heart to pump blood around the body so a high blood pressure is not needed.

44
Q

What does ABP blood profiles stand for?

A

Ambulatory blood pressure profiles.

Inspected in relation to dietary information and time of drug treatment.

45
Q

What happens to blood pressure and heart rate in response to painful stimuli?

A

They increases

46
Q

What happens to systolic and diastolic pressure when the ventral part of the brain is activated?

A

The systolic and diastolic pressure decreases

47
Q

What happens to systolic and diastolic pressure when the dorsal part of the brain is activated?

A

The systolic and diastolic pressure increases

48
Q

Which levels of sympathetic nerves innervate all vasculature of the body?

A

T1-L2

49
Q

Which levels of sympathetic nerve innervate the heart?

A

T1-L5

50
Q

Which autonomic nerves maintain control of the heart rate?

A

Mainly parasympathetic stimulation. This maintains heart rate around 70bpm. Means that decreasing parasympathetic innervation will increase the heart rate.

51
Q

What is the overall formula for blood pressure?

A

Blood pressure = Stroke volume x Heart rate x Total peripheral resistance

52
Q

What do baroreceptors detect changes in?

A

They detect changes in blood pressure.

53
Q

Where are baroreceptors located in the body?

A

Baroreceptors are located in the aortic arch (sends signals through her vagus nerve) and the carotid sinus (sends signals through the glossopharyngeal nerves).

54
Q

What happens when blood pressure increases above the set point?

A

Increases in blood pressure ->
Increases the stretch in the baroreceptors ->
Sends more signals to the brainstem ->
Decreases sympathetic tone -> Decreased vasoconstriction and venoconstriction -> Decreases cardiac contractility ->
Increased parasympathetic tone ->
Decrease in heart rate

55
Q

What happens when blood pressure decreases below the set point?

A

Decrease in blood pressure ->
Decreases the stretch in the baroreceptors ->
Sends fewer signals to the brainstem ->
Increases sympathetic tone -> Increased vasoconstriction and venoconstriction ->
Increased cardiac contractility ->
Decreased parasympathetic tone ->
Increase in heart rate

56
Q

How does acute haemorrhage trigger the baroreceptor reflex?

A

In a haemorrhage the blood volume is decreased.
This means the venous pressure and volume of venous return to the heart is also decreased.
This decreases the atrial pressure therefore the preload is also decreased.
Decreased preload also decreases the end diastolic volume.
Results in a decreased stroke volume and cardiac output.
Overall results in a lower arterial blood pressure.
This then triggers the baroreceptor reflex.

57
Q

How does the baroreceptor restore cardiac output in myocardial infarction?

A

Inability of heart to contract means the cardiac output is decreased.
This results in decreased arterial blood pressure, so the stretch of the baroreceptors is also less.
This increases sympathetic activity (higher contractility, vasoconstriction/venoconstriction) and decreases parasympathetic activity (higher heart rate).
This increases the filling of blood into the heart, which leads to a higher arterial blood pressure being generated, which acts to restore the cardiac output.

58
Q

Why can’t the baroreceptor reflex work indefinitely in low blood pressure situations?

A

Making the heart contract at a higher rate and greater force of contraction can cause cardiac hypertrophy in the long term.
This can reduce the lumen in the heart, so less blood can fill the heart.
Means the stroke volume decreases.
The renin angiotensin system also further increases the blood plasma volume and venous return to the heart, and this increase in preload puts even more pressure on heart to pump a greater volume.
Exacerbates the problem.
Not sustainable as the coronary arteries cannot supply the heart with enough blood.

59
Q

What is the baroreceptor response to hypertension?

A

Increased blood pressure in hypertension ->
Increased stretch so increased firing from baroreceptors ->
Decreased sympathetic tone (lower contractility and increased vasoconstriction/venoconstriction) ->
Increased parasympathetic tone -> Decreased blood pressure and heart rate respectively

60
Q

What would the firing rate of baroreceptors be during hypertension/systole?

A

Firing rate would be increased

61
Q

What would the firing rate of baroreceptors be during hypotension/diastole?

A

Firing rate would be decreased

62
Q

What is postural hypotension?

A

When blood pressure drops when standing and the baroreceptor reflex does not work to restore the blood pressure.

63
Q

Why is there a specific range within which the firing of baroreceptors has an effect?

A

Because speed at which the baroreceptor can send impulses can reach a maximum, as the baroreceptors can only stretch so far.

64
Q

What is the effect of gravity on venous return?

A

Gravity directs blood to the lower extremities, resulting in a reduced venous return to the heart -> Blood pooling

65
Q

What is the compensatory mechanism for blood pooling in the lower extremities?

A 
Increased force of contraction
Vasoconstriction/venoconstriction
(sympathetic)
Increased heart rate
(parasympathetic)
66
Q

How does the valsalva manoeuvre test the baroflex function?

A

1) Exhaling against a closed glottis
2) Intrathoracic pressure increases
3) Venous return is prevented
4) Increased heart rate tries to maintain the blood pressure

5) Pressure is released
6) Intrathroacic pressure returns to normal
7) Venous return increases massively
8) heart rate has to slow down to maintain the blood pressure

67
Q

Outline what aspects of the cardiovascular system is altered during exercise?

A 
Cardiac output and heart rate increases.
Total peripheral resistance decreases.
Systolic blood pressure increases.
Diastolic blood pressure decreases.
Stroke volume usually increased.
68
Q

Outline the feed forward mechanism that takes place after the thought of exercise?

A

This mechanism inhibits the cardiac vagal fibres and the excitation of the sympathetic nervous system.
This changes the sensitivity so the pressure range is shifted to the right.
The resulting higher blood pressure means the baroreceptor has to react to a higher blood pressure to overcome it - means it is harder for the baroreceptors to greatly influence sympathetic or parasympathetic effects.

69
Q

Outline the function of atrial receptors

A

These are stretch receptors located in the atria.
Stimulated by increased filling pressure in the atria.
Causes an increase in cardiac output, similar to baroreceptors.
Means that atria can fill the ventricles with more blood.

70
Q

Outline the function of ventricular mechanoreceptors

A

Ventricular mechanoreceptors cause bradycardia and vasodilation.
This prevents the heart from overworking.
Vasodilation prepared the body for a larger ejection of blood from the heart.
Bradycardia allows time for the blood pressure to drop before the next ejection of blood.

71
Q

List 3 other factors that can also have an effect on cardiovascular responses

A

1) Temperature (cold = vasoconstriction, warmth = vasodilation)
2) Pain (increases the cardiac output)
3) Metabolites from muscle (CO2, lactic acid)

72
Q

What can stimulates the chemoreceptors?

A

Low pO2 or high pCO2 (acidosis)

73
Q

What is the function of chemoreceptors?

A

When stimulated, chemoreceptors increase respiration from the respiratory centres.
It also stimulates the cardiovascular system to increase the cardiac output and blood pressure.

74
Q

When does self preservation occur?

A

Occurs if there is increased reparation and if gas exchange cannot be increased through tachycardia.
The body tries to send blood to organs that need it.

Circulation and Breathing (7 decks)

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