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Cardiorespiratory > Smooth and Cardiac Muscle > Flashcards

Smooth and Cardiac Muscle Flashcards

1
Q

describe the appearance, if multi or single nucleated, and what smooth muscle controls

A
  • *- spindle shaped**
  • single nucleus
  • non-striated
  • mechanical control of organ systems
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2
Q

describe cardiac muscle

A
  • *-** cardiac myocytes are organised in branched meshwork of fibres that run in various directions
  • centrally located nuclei
  • invol. muscle
  • causes beating of the heart
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3
Q

describe skeletal muscle

how does it attach to the bone?

A
  • skeletal / voluntary muscle
  • anchored to bones via **tendons
  • **function: locomotion, posture maintenance and breathing
  • striated (made from actin and myosin)
  • multinucleated
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4
Q

describe the structure of cardiac muscle fibres

what are: a) sarcolemma b) sarcomere c) sarcoplasmic reticulum

what type of junctions exist?

A

made of:

i) A bands = thick filaments
ii) I bands = thin filaments

  • surroundered by membrane: sarcolemma
  • sarcoplasmic reticulum: like ER, contains Ca2+ ions
  • sarcomere: functional contractile unit of muscle (made of A&I band and actin and myosin)

gap junctions are in cardiac muscle fibres

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5
Q
A
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6
Q

what is the role of intercalated discs?

what type of cell-cell junctions do they contain?

A

connect cardiac myocytes together

  • *cell-cell junctions:**
  • fascia adherens (anchoring junctions) - attach sarcomeres to cell membrane
  • desmosomes - site of adhesion, keep muscle cells connected when they contract
  • gap junctions - faciliate electrical communication - passage of ions and AP spread through
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7
Q

which cell-cell junctions permit AP in intercalated discs?

A

gap junctions

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8
Q

what are the specialised properties of cardiac muscle cells regarding AP?

what does automaticity & rhymthmicity mean re AP?

A
  • DO NOT require depol from nerves
  • automaticity: spontaneously generate an electrical impulse (depol)
  • rhymthmicity: generate AP in regular and repetitve manner

properties:
- waves of depol propagate between cells via gap junctions on IC disks
- waves of depol propagate to adjacent cells: contract in synchronouse fashion = rapid, synchronous depolarization of the myocardium
myocardium functions as a single contractile unit: important for pumping action of the heart

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9
Q

which are the repolarsing ions and depolarsing ions involved in AP?

A

many ion channels are involved in the overall make up of the response

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10
Q

* why are there different AP in different regions of the heart *

A

different ion channels are expressed in different myocytes around the heart
means that the size and shape of AP can differ between cells, depending on function of cells

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11
Q

where do u find pacemaker cells?

how do u describe the AP that pacemaker cells create?

what do AP look like?

A

pacemaker cells

  • depolarise spontanously (automaticity)
  • characteristic shaped AP - wandering baseline
  • occur in: SA node & AV node (although atrial and v. cells can do this in disease)
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12
Q

what are the AP of non-pacemaker cells like (esp. ventricular cells?)

what does this mean the heart beats like?

A
  • ventricles act in coordinated fashion - contractile works to expell blood into vessels = WHY they have refractory period
  • means have to contract AND relax , rhythmically, before in order to go through cardiac cycle.
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13
Q

explain the mechanism of calcium signalling driving muscle contraction

A
  • depol of membrane from Na+, through Na+ channels = opens Ca 2+ channels
  • Ca2+ move through calciumc channels into cell membrane
  • rise in Ca2+ triggers further calcium release from the sarcoplasmic reticulum, via the ryanodine receptor
  • calcium associates with troponin C in the sarcomere, to initate contraction in the cardiac muscle (systole)

- events terminated by release of Ca2+ from sarcomere (relaxation - diastole), and reuptake into sarcoplasmic reticulum

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14
Q

what happens when calcium binds to troponin for striated muscle contraction?

what does ATP hydrolyse provide energy for ?

A

calcium: binds to troponin in troponin complex, exposes the myosin binding sites on the actin = allows the myosin to bind

ATP hydrolyses: provides the energy to drive filament sliding

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15
Q

what is the effect of sympathetic and parasympathetic on the heart?

what NT and receptor used for each? ^

A

sympathetic: increaeses HR and force of contraction. secretion of noradrenalin and activation of B1 adrenoreceptor

parasympathetic: decreases HR. secretion of ACh and activation of muscarinin (M2) receptors

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16
Q

for skeletal, cardiac and smooth muscle - what are they striated and vol / invol?

A

Skeletal muscle is voluntary and striated

cardiac muscle is involuntary and straited

smooth muscle is involuntary and non-striated.

17
Q

what is structure of smooth muscle like?

what do intermediate filaments do in SM?

what do dense bodies do?

A

- loose lattice of thick and thin fillaments (actin & myosin) that run obliquely across the muscle

  • non striated
  • cytoskeletal intermediate filaments assist in the transmission of force generated by contraction
  • dense bodies: attachment for thick and thin filaments - (equivelent to z lines of striated muscle)
18
Q

what are the two types of attachment you get in smooth muscle?

A
  1. mechanical attachments: between cells
  2. gap junctions: provide a pathway for passage of electrical signals
19
Q

where is smooth muscle found?

function? (4)

A
  • *location:**
  • **within walls of organs and strucutres
  • **e.g. BV, bronchi, bladder, uterus, gut
  • *functions:**
  • *primary function is contraction:**
  • regulation of diameter of BV
  • regulating diameter of airways
  • propulsion of food through GI tract
  • contraction of uterus (deliver baby :))
20
Q

what are the different types of AP shape from SMC? (3)

can smooth muscle cells do spontaneous electrical activity?

A

shape of AP varies depending on where the SMC are

  • e.g. simple spike, spike and plateau , spikes on top of slow waves

smooth muscle cells do spontaneous electrical activity

21
Q

what is AP length in:

a) smooth muscle
b) skeletal muscle?

A

a) smooth muscle: 10-50ms
b) skeletal muscle: 2ms

smooth muscle is longer !!

22
Q

in smooth muscle

  • which ion-gate causes depolaristion of AP?
  • why do we see slower upstroke of AP compared to skeletal muscle?
A
  • smooth muscle: mainly Ca2+ channels (some Na+)
  • calcium channels open more slowly than sodium channels - why we see slower upstroke
23
Q

decribe the mechanism of excitation-contraction coupling happens in SMC

A
  • rise in intracellular calcium can occur by
    i) depol of membrane opens Ca2+ channels and calcium enters
    OR
    ii) agonist induced release of calcium via IP3., through sarcoplasmic reticulum
  • Calcium binds to calmodulin, which actiavtes an enzyme called myosin light chain kinase (MLCK)
  • MLCK activates myosin head by phosphorylating them (ATP -> ADP + Pi, Pi attaches to the head)
  • phosphorylation of myosin light chain increase ATP activity and allows myosin head groups to bind to actin & undergo cross-bridge cycling (which initiates contraction)

-

24
Q

describe the mechansim of SMC contraction

A
  • thin filaments slide past the thick filaments, pulling on the dense bodies (connected to the sarcolemma)
  • dense bodies pull on the intermediate filaments’ networks through the sarcoplasm
  • causes entire muscle fibre to contract - ends are pulled towards the centre, causing midsecction to bulge
25
Q

what are the different triggers for SMC contration and relaxation?

A

SMC triggers: hormones, neural stimulation by ANS and local factors

26
Q

how is smooth muscle innervated?

what are varicosities?

A

axon of postganglionic autonomic neuron terminates on SMC, via varicosity

varicosity: releases the NT into space surrounding the muscle. NT receptors are widely spread across the postsynaptic membrane

then between the SMC: have gap junctions that permit electrical coupling between cells

(how much that is gap junction or varicosity depends on tissue)

27
Q

what are the two overaching types of smooth muscle organization (think innervation) ?

what are the difference between these? ^

where each found?

A
  • *multi-unit smooth muscle:
  • **each smooth muscle cell recieves synpatic input.
  • little electrical coupling
  • each SMC can contract independently of neighbour: **fine control
  • (**similar to motor unit in skeletal muscle)
  • location: intrinsic muscles of eye & SM of larger BV
  • *single-unit smooth muscle:
  • ** autonomic NS innervates a single cell within a sheet or bundle
  • AP is propogated by gap junctions to neighboring cell: whole bundle contracts as a functional syncytium
  • slow, steady contractions (allow food substances to move around body)
  • location: walls of all viseceral organs
28
Q

which of single or multi unit SMC does:

  1. slow, steady contractions and is found in the walls of all viseceral organs?
  2. can contract independently of neighbour, has fine control and is found in intrinsic muscles of eye & SM of larger BV
A
  1. single unit smooth muscle
  2. multi unit smooth muscle
29
Q

what is vasucular smooth muscle?

how many factors influnce contraction or relaxtion of ^?

A

smooth muscle within walls of BV

APPRECIATE A LOT OF FACTORS (from different NT) CAN STIMULATE VASCULAR SMOOTH MUSCLE CONTRACTION AND RELAXATION

30
Q

what does parasym and sym effect on:

  1. the action
  2. the mechanism

of bronchial smooth muscle?

A

action:

  • parasympathetic: bronchial constriction and mucus secretion
  • sympathetic: bronchial dilation

mechanism:

  • parasympathetic: Ach & M3 muscarinin receptors
  • sympathetic: adrenalin / noradrenaline and B2 adrenergic receptor
31
Q

what are treatments that work on para and symp system for bronchial smooth muscle?

A

SABAs and LABAs are used in treatment of asthma bc work by bronchial dilation

32
Q

xox

A

Cardiorespiratory (41 decks)

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