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PHOL1001 > Cardiovascular system (cardiac and smooth muscle) > Flashcards

Cardiovascular system (cardiac and smooth muscle) Flashcards

1
Q

what stops the myosin head from binding to actin ?

A

Tropomyosin

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2
Q

why are cardiac muscle cells striated ?

A

because of the alternating thick and thin myosin fliaments

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3
Q

what are intercalated disks?

A

made of three types of cell-cell junctions: 1. Fasica adherens

  1. Desmosomes
  2. Gap junctions
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4
Q

What are Fasica adherens?

A

They are anchoring sites for intracellular actin filaments which connect to integrins ( membrane bound proteins) which connect to fibronectin. Fibronectin can act acts as bridges connecting integrins to proteglycans complexes (collagen and carbohydrate). This anchors the cell to it’s extracellular matrix and plays and important role in cell signalling.

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5
Q

What are desmosomes ?

A

Stop the separation during contraction by binding intermediate filaments via cadherins( membrane bound proteins) , joining cells together.

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6
Q

What are gap junctions ?

A

From when 6 membrane proteins called connexins form an elongated, donut-like structure called a connexon. Allow for the transport of ions, water and other structures between cells without escaping to the extra cellular matrix. i.e action potentials spread between cardiac muscle cells, i.e depolarisation in sync.

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7
Q

Are pacemaker cells cardiac muscle cells ?

A

No

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8
Q

What is the sinus rhythm ?

A

Pacemaker cells in sino atrial node automatically depolarise resulting in a wave that results in the sinus rhythm

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9
Q

How does wave spread ?

A

SA in RA to LA then to AV node (delay) down the bundle of his to purkinji fibres to ventricles. Delay is to ensure atria have finished contracted before the ventricles contract.

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10
Q

What is meant by the contraction is myogenic in origin ?

A

originating in muscle tissue rather than from nerve impulses

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11
Q

Where is the origin of the nerve fibres ?

A

autonomic ganglia

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12
Q

what do the autonomic nerves do ?

A

they control the functions of internal organs like the heart, stomach and intestines.. specifically in the context of the heart, they act to modulate the rate and force of the contraction of cardiac muscle

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13
Q

which nervous system are the autonomic nerves part of?

A

peripheral nervous system

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14
Q

autonomic nervous system split into ?

A

sympathetic nerves (fight or flight) and parasympathetic nerves (at rest) both

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15
Q

Vagus nerve in association with what ?

A

parasympethetic nervous system..

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16
Q

What is the force of contraction regulated by ?

A

The degree of stretch of muscle fibres.. hormonal signals and autonomic nerves

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17
Q

Effect of increased stretching of cardiac myocytes on tension

A

directly proportional

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18
Q

Effect of Norepinephrine of tension ?

A

directly proportional

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19
Q

100 beats/min

A

heart rate of SA pacemaker cells without innervation by sympthetic nerves or parasympathetic nerves

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20
Q

60-70 beats/min

A

heart rate due to parasympathetic nerves innervating pacemaker cells in SA

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21
Q

What effect does acetylcholine have on the heart ?

A

acts by opening K+ channel via g protein, hence lowering heart rate - hence this is parasympethteic signal - think vagus nerve

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22
Q

what effect does noraepinephrine have on the heart’s pace maker cells ?

A

opens Ca2+ channels via G proteins. The inotropic response.

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23
Q

does epinephrine and norepinephrine have the same effect of the heart’s pace maker cells ? if so, why ?

A

yes, because the adrenegic receptors in the heart are all beta receptors. However, this is not the case in various other organs.

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24
Q

how do the depolarisation phases vary between pacemaker cells and non-pacemaker cells ?

A

in pacemaker cells, calcium ions are involved in the initial depolarisation of phase of the action potential.
but in non-pacemaker cells depolarisation is caused by an opening of sodium channels.

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25
Q

what is the depolarisation phase of skeletal muscle action potential caused by ?

A

an opening of sodium ligand gated channels which causes vg gated sodium channels to open .. depolarisation which causes ca2+ to be released from SR.. contraction

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26
Q

What modulates pacemaker activity ?

A

Autonomic nerves - chronotropic regulation

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27
Q

How is a muscle contraction initiated in skeletal muscle ?

A

Nevre action potential - ACh secretion by nerve ending - End-plate potential - Muscle Action potential - Depolarise T-tubules and open Ca2+ channels of SR - increased Ca2+ conc from SR - contraction - Pump Ca2+ into SR - Relaxtion

28
Q

What is the shape of cardiac muscle cells ?

A

discrete rod shaped cells linked together by intercalated disks and connected electrically via gap junctions

29
Q

what is the heart rate set by ?

A

the pacemaker activity of the sion-atrial node.

30
Q

What is the long plateau of the cardiac action potential due to?

A

Ca2+ influx through voltage-gated calcium channels.

31
Q

Why does the cardiac action potential coincide with the contractile response ?

A

So cardiac muscle cannot be tetanized

32
Q

What is the force by which cardiac muscle is regulated by ?

A

The Frank-Starling mechanism (preload) and by its inotropic state (intrinsic contractility)

33
Q

where are smooth muscle cells found ?

A

the walls of hollow organs of the body and the blood vessels. it is also found in the eye.

34
Q

What are the two main types of smooth muscle ?

A

single unit smooth muscle and multi unit smooth muscle

35
Q

Are the smooth muscle contractions in single unit smooth muscle myogenic or neurogenic in origin ?

A

myogenic

36
Q

Are the smooth muscle contractions in multi unit smooth muscle myogenic or neurogenic in origin

A

largely initiated by autonomic nerve fibres and therefor neurogenic in origin

37
Q

How are the contractile proteins of smooth muscle arranged ?

A

They are arranged in a loose matrix ?

38
Q

How does the loose arrangement of smooth muscle matter ?

A

allows for a greater degree of shortening than seen in striated muscle

39
Q

is there troponin, tropomyosin in smooth muscle?

A

no - think myosin light chain kinase reaction. Agonists can act via second messenger IP3 releasing Ca2+ from SR leading to contraction via activation of myosin light chain kinase

40
Q

What is the shape of smooth Muscle ?

A

spindle shaped cells

41
Q

Are the contractile proteins arranged in regular sarcomeres ?

A

no therefore no striations

42
Q

How does smooth muscle maintain a steady level of tension known as tone ?

A

it is modulated by autonomic nerves, by local chemical factors (paracrine agents) and by circulating hormones

43
Q

How does the myogenic activity of single unit smooth muscle behave ?

A

in syncytium

44
Q

What is the shape of skeletal muscle cells ?

A

long cylindrical cells with many nuclei, striations

45
Q

What is the shape of cardiac muscle ?

A

irregular rod shaped cells with many nuclei, striations

46
Q

What is the shape of smooth muscle cells ?

A

spindle shaped with a single nucleus, no striations

47
Q

30 cm (length) times 100 micrometers (diameter)

A

skeletal muscle cells

48
Q

100 micrometres (length ) times 15 micrometers (diameter)

A

cardiac muscle

49
Q

200 micrometres (length) times 5 micrometers (diameter)

A

smooth muscle

50
Q

do skeletal muscle show myogenic activity ?

A

no, they exhibit neurogenic activity

51
Q

innervation of skeletal muscle

A

somatic

52
Q

innervation of cardiac and smooth muscle

A

autonomic

53
Q

Contraction type of skeletal muscle ?

A

phasic

54
Q

Contraction type of cardiac muscle ?

A

Rhythmic

55
Q

Contraction type of smooth muscle ?

A

Mostly tonic

56
Q

Basis of muscle tone for skeletal muscle

A

neural activity

57
Q

Basis of muscle tone for cardiac muscle ?

A

None

58
Q

Basis of muscle tone for smooth muscle ?

A

Intrinsic and extrinsic factors

59
Q

Cells electrically coupled ?

A

skeletal no cardiac yes smooth - only single unit

60
Q

T- system ?

A

skeletal muscle yes , cardiac muscle yes but only in ventricular muscle , smooth muscle no

61
Q

Mechanism of e/c coupling in skeletal muscle ?

A

Action potential and T -system

62
Q

Mechanism of e/c coupling in cardiac muscle ?

A

action potential and t system

63
Q

Mechanism of e/c coupling in smooth muscle ?

A

action potential and second messengers(IP3)

64
Q

Hormonal regulation ?

A

Skeletal muscle no, Cardiac muscle yes, smooth muscle yes

65
Q

What is cardiac output ?

A

HR*SV

PHOL1001 (8 decks)

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