Ph1 general

Phase 1 - General
Membrane Transport Processes
1. What kind of molecules can cross selectively permeable biological membranes
without the aid of channel proteins?1
2. Give some examples of small uncharged polar molecules2
3. Why do ions need the help of a specialist channel protein to cross the membrane?
3
4. What is the difference between diffusion and facilitated diffusion?4
5. What is the difference between primary and secondary active transport?5
6. What is the partition coefficient?6
7. By what means can a transmembrane channel protein be ‘gated’?7
8. How do the kinetics (rate of uptake vs. concentration) differ between facilitated
and simple diffusion?8
9. What is Km in relation to substrate uptake by channel proteins?9
10.What are the 3 main types of glucose transporter and where are they generally
found?10
1 Water, small uncharged or hydrophobic molecules via simple diffusion down a concentration gradient
2 H20, CO2, Urea and glycerol
3 Because they are charged
4 Facilitated diffusion uses transmembrane carrier proteins, although energy is not used up and it requires a
concentration gradient just the same as simple diffusion
5 In primary active transport ATP is used as an energy source, in secondary active transport the energy
source is an electrochemical gradient, e.g. Na+/Glucose transporter in the gut
6 Measure of how lipid soluble (read: hydrophobic) something is. The more lipid soluble something is the
faster it will travel across a lipid bilayer.
7 Voltage, ligand or mechanically gated
8 Simple diffusion is entirely linear (assuming there is infinite space to expand into), whereas with facilitated
diffusion the increase in rate of uptake is greater but plateaus off at a certain concentration once all the
channels become fully utilised.
9 Transporter affinity for the substrate, the lower the Km, the higher the affinity
10 Glut-1 = blood cells, Glut-2 = liver, pancreatic B-cells, Glut-4 (insulin regulated) = muscle, adipose

11.If having a low Km for glucose means a high affinity for it, why do liver cells have a
high Km for glucose?11
12.Where would you find Ca2+ATPase?12
13.Describe the mechanism of Na/K+ ATPase13
14.What substances used in the treatment of heart failure block the Na+/K+
ATPase?14
15.How does inhibition of Na+/K+ ATPase increase cardiac muscle contraction?15
16.Which two areas of the body widely use Na+/Glucose co-transporters?16
17.What keeps the intracellular Na+ concentration in intestinal lumenal cells low so
that the glucose/Na+ transporter functions effectively?17
pH and Buffers
1. What is the normal range for blood pH?18
2. Where do acids in the body come from?19
3. Which two organs in particular regulate acid-base balance?20
4. What effect does a rising level of OH- have on pH?21
11 Because they only want to absorb glucose when it is at high concentration in the blood, so need a high Km
12 Sarcoplasmic reticulum in muscle cells
13 Na+ binds to intracellular site (when high Na+ in cell), triggers phosphorylation of the pump,
phosphorylation causes a conformational change, release of Na+ into exterior and exposes K+ binding site,
K+ binds and triggers dephosphorylation, moving K+ into the cell.
14 Ouabain/Digoxin, prevent K+ binding.
15 Increases intracellular Na+ (because less is pumped out), which inhibits the Na+/Ca+ (which normally
takes Ca2+ out of the cell), so raised intracellular Ca2+ increases the force of contraction.
16 Absorbtion of glucose against concentration gradient in the kidneys (from filtrate) and in the small intestine.
17 Na+/K+ ATPase takes Na+ out of the cell on the basolateral side
18 7.35-7.45
19 Food, breakdown of protein, incomplete oxidation of fats or glucose, carbon dioxide in the blood
20 Lungs, kidneys (and chemical buffers in blood)
21 Raises pH because it binds H+, decreasing acidity

5. What is the difference between a weak base and a strong base?22
6. What is the difference between a weak acid and a strong acid?23
7. What is the difference in proportion of water in body mass in infants compared
to old age?24
8. What is the equation for working out pH when you know the hydrogen conc?25
9. What is pKa?26
10.What is the Henderson-Hasselbalch equation?27
11.Why is buffering best at the pKa?28
12.What makes haemoglobin a good blood buffer?29
Electrical Properties of Cells: Membrane Potentials
1. What is the resting membrane potential for neurons and skeletal/cardiac muscle?
30
2. With reference to charge, what is current?31
3. What affects current through a circuit?32
22 A strong base dissociates completely into a metal/salt and hydroxide in aqueous solution (and therefore
raises the pH signiﬁcantly, a weak base only dissociates partially and so has less effect on pH.
23 A strong acid is one which ionizes completely in water to produce a high concentration of H+, a weak acid
only partially ionizes so does not decrease the pH of the solution as dramatically
24 73% in infants goes down to 43% in old age. (60% in average man, 50% in average woman)
25 pH = - log [H+]
26 pKa = -log Ka (Ka is the dissociation constant, i.e. the pH at which the acid is half dissociated, (the middle
curve), the lower the pKa, the stronger the acid because the acid dissociates more readily.
27 pH = pKa + log conjugate base
! ! ! acid
28 Because if H+ are added they can be picked up at the conjugate base, if OH- are added they can form
H20. There are equal amounts of acid and base so pH changes are resisted.
29 presence of large number of histidine residues, pKa close to blood pH. (pKa = 6-6.5, blood is 7.35-7.45)
30 -70mv for neurons, -90mv for cardiac muscle
31 movement of charge
32 Electrical resistance (measured in ohms)

4. What is Ohm’s law?33
5. What is capacitance?34
6. How does charge separation arise across a cell membrane?35
7. What is equilibrium potential?36
8. What is the Nernst equation?37
9. What maintains the ionic gradient across cell membranes?38
Communication Between Excitable Cells
1. What is the difference between the resting membrane, active membrane and
refractory membrane?39
2. What factors determine the speed of an action potential?40
3. What is the approximate conduction speed of an unmyelinated fibre?41
4. ... and a myelinated fibre?42
5. Which are the slowest and the fastest out of sensory, motor, slow sensory and
autonomic fibres?43
33 V = I x R
34 Storage of charge
35 Salt dissolved in water dissociates into ions. Inequality of charge across an impermeable membrane would
create charge separation and therefore a potential difference. One side has more Cl- than K+ the other has
more K+ than Cl-, the membrane acts as a capacitor. The separation arises when the membrane is
permeable to K+ but not negative ions.
36 The potential when the concentration and electrical driving forces are equal
37 For working out the equilibrium potential.
38 Na/K ATPase maintain ionic gradient, otherwise it would just degrade and cell would die
39 Resting = no change in current -90mV, Active = site of AP, local currents flowing between areas of differing
polarity, Refractory membrane = Membrane which AP has just passed not yet ready for a second excitation
40 Diameter of axons (resistance decreases as diameter increases), myelination of axons (electrical
insulator), decreased temperature of axons decreases speed
41 0.5-2.5m/sec
42 faster at 2-15m/sec
43 Sensory and motor are fastest, then slow sensory, autonomic are slowest

6. How can AP conduction be blocked, give examples of what would do this
reversibly and irreversibly?44
7. Where are APs transmitted from cell to cell?45
8. What is the direct result of the binding of transmitter to a receptor at a chemical
synapse?46
9. What are the key differences between a chemical synapse and a gap junction?47
10.Where are APs initiated?48
11.What do orthodromic and antidromic mean?49
12.What is the approximate time delay caused by synaptic transmission vs. gap
junctions50
13.What does saltatory conduction mean?51
Anatomical Terminology
1. What are (i) Saggital (ii) Coronal (iii) Transverse plains of the body?52
2. What do (i) lateral, (ii) ipsilateral, (iii) contralateral mean in terms of relationship
to the body?53
3. What are abduction and adduction?54
44 Both by blocking Na+ channels, Na+ initiates AP ﬁring. Reversibly = lidnocaine, Irreversibly = poison
45 Chemical synapses between neurons, low resistance electrical gap junctions (e.g. myoﬁbrils in cardiac)
46 Either opening/closing of ion channel or activation of enzyme system which opens/closes ion channels
47 In a chemical synapse a transmitter is used (e.g. acetylcholine), the membranes are not in direct contact, it
is also uni directional and has a delay.
48 Receptors in sensory neurons, axon hillock in spinal cord
49 Propagation of APs in the normal (ortho) direction or against it (anti).
50 0.5ms
51 Greatly slowed down
52 Saggital - Vertical dividing the body into left and right, Coronal - vertical plane dividing the body into front
and back, Transverse - horizontal plane dividing upper and lower.
53 Lateral - away from the median plane, Ipsilateral = on the same side, Contralateral = on the opposite side
54 Abduction = away from the median plane, Adduction - towards the median plane

4. ... flexion and extension?55
5. ... pronation and supination?56
6. What are the three main layers of skin?57
7. Name the structures aligned to gap junctions which give continuous water-filled
pores allowing the passage of electrical currents58
8. What are the three layers of fascia? (one of them is a skin layer)59
9. What are the three areas/compartments of serous membrane?60
10.What layer do venules lack which is present in arterioles?61
11.What is the approximate thickness of a muscular artery wall in mm?62
12.Which vein does the thoracic duct (lymph) ultimately drain into?63
13.Where are the 4 main areas of lymph nodes in the body?64
The Skeleton
1. What are the basic cells of cartilage which are precursors to bone?65
2. What is the function of bone in relation to muscles?66
55 Flexion = increasing joint angle, Extension = decreasing joint angle
56 (If lying down) Supination: palm facing upwards, Pronation: palm facing downwards
57 Epidermis, dermis (connective tissue), hypodermis (superficial fascia, fat, collage, elastic fibres)
58 connexons
59 Hypodermis (superficial fascia), Deep fascia (interconnects organs and muscles, capsules around organs),
subserous fascia (loose connective tissue, between serous membranes and deep fascia).
60 Pleura (lungs), pericardium (heart) and peritoneum (abdominal cavity)
61 Smooth muscle tunica media, have a tunica externa instead
62 1mm, aorta is 2mm
63 Subclavian vein
64 Inguinal (inguinal ligament and groin), axillary, cervical (neck), GI tract and cysterna chyli
65 Chondroblasts which secrete ground substance and collagen to form a rigid gel, once formed the cells
remain in situ as chondrocytes
66 Provides leverage for movement of muscle

3.Why does cartilage not have neurovascular elements?67
4.What are the other main functions of bone?68
5.What is the difference between axial and appendicular
skeleton?69
6.What are the five classifications of bone by shape?70
7.What are the two types of tissue in a mature bone?71
8. Name parts A-E on the diagram of a long bone (left)72
9.What is the perichondrium?73
10.What is the difference between endochondrial
ossification and intramembranous ossification?74
11. Label the external markings A-H on the long bone
diagram (right)75
12.Describe what each of these are: Condyle, trochlea,
facet, process, ramus76
13.What is a tubercle?77
67 Because it gains its nutrients by diffusion from the ground substance
68 Haemopoesis (bone marrow), storage of calcium and phosphorus, protection (e.g. skull)
69 Axial = bones that derive from the central axis of the body i.e. ribs, skull, vertebral column. Appendicular
skeleton = more peripheral and derive from the bones of the axial skeleton (limbs, pelvis, scapula, clavicle)
70 Long bone, Flat bone (e.g. sternum), Irregular bone (e.g. vertebra), Sesamoid bone (e.g. patella), short
bone
71 Spongy (trabecular) bone and compact bone
72 A = articular cartilage, B = spongy bone, C = Endosteum, D = Compact bone, E = Periosteum
73 A layer of dense irregular connective tissue that surrounds the cartilage of developing bone
74 Endochondrial = development of bone at end of existing bone, Intramembranous = without the use of
cartilage and taking place within a mesenchyme or cavity of an existing bone
75 A =Trochanter, B = fossa, C = Head, D = neck, E = tuberosity, E = facet, F = trochlea, G = condyle, H =
tubercle
76 Condyle = a smooth rounded articular process, trochlea = a smooth grooved articular process, facet = a
small flat articular surface, Process = any projection or bump, Ramus = an extension of the bone at an angle
to the rest of the structure
77 A small roughened projection (as opposed to a rough one: trochanter or tuberosity)

Joints and Muscle
1. What are the 3 types of joints in the body and what are they held together by?78
2. What are the three types of fibrous joints?79
3. What are the 3 types of sutures?80
4. What are synchondroses (primary cartilaginous joints)?81
5. ... and secondary cartilaginous joints?82
6. What are bursae?83
7. What does it mean to be uniaxial, biaxial or miltiaxial?84
8. What are ellipsoid and condyloid in relation to the shapes of synovial joints?85
9. What are the three types of common tendons (that serve as attchments to 2 or
more muscles)?86
10.What is a tendon sheath?87
11.Which end of the muscle, proximal or distal, correspond to origin and insertion?88
12.What type of role does the muscle have if it is a synergist?89
78 Fibrous - united by collagen, Cartilaginous = united by cartilage, Synovial = filled with synovial fluid
79 Sutures = skull bones, Syndesmoses = interosseous membranes (little movement), Gomphoses =
between skull/jaw and teeth
80 Squamous (flat), serrated (smooth wavy line), Denticulate (angular wavy line like teeth)
81 Cartilaginous joints between bones of endochondrial origin (e.g. long bones), have a plate of hyaline
cartilage between opposing surfaces, contain a joint cavity, fully moveable on angle.
82 Symphyses - are partially moveable joints covered in cartilage but are at the midline rather than the ends
of bones
83 Sacs in synovial joints filled with synovial fluid
84 one, two or three+ axes of rotation
85
86 Intermediate, Raphe and Aponeurosis
87 Synovial tendon sheaths offset friction and hear from synovial joints. Contains synovial fluid to do this.
88 Insertion = proximal, Origin = distal
89 Refine undesirable movement of the prime movers/agonists

Tissue Organisation and Epithelia
1. What layer do epithelia rest on top of?90
2. What process supplies epithelial cells with nutrients?91
3. What are the three classifications of epithelia based on cell shape?92
4. What are the three classifications based on layer structure?93
5. What are the three classifications based on surface specialisation?94
6. What is the difference between merocrine and apocrine secretion?95
7. What are desmosomes and hemidesmosomes?96
8. What are adherens junctions?97
9. What is the difference between tight and gap junctions?98
10.Name the two tight junction proteins?99
Soft Connective Tissue
1. What are fibroblasts?100
90 Fascia, basement membrane (ECM)
91 Diffusion entirely, no blood vessels leave the basement membrane
92 Squamous (flat), cuboidal or columnar
93 Simple (single cell thick), pseudo-stratified (only some permeate the whole layer), stratified (multi-layered)
94 Ciliated (mucus/respiratory), brush border (microvilli), keratinised (tough protective protein, e.g. palm of
hand/sole of foot)
95 Merocrine = vesicles open onto the surface of the cell, Apocrine = fragmentation of part of cell containing
vesicles into lumen, other half of cell remains.
96 anchors of intermediate fibres (keratin) between cells (desmosome = to similar bundle in neighbor cell),
(hemidesmosome = to basal lamina)
97 protein complexes that occur at cell-cell junctions in epithelial tissues, linked to actin skeleton
98 Tight = barrier junction (prevent passage of molecules), Gap = allow some molecules through the gap,
selective communication between cells
99 Claudin, occludin
100 Cell which synthesizes ECM and collagen, structural framework for animal tissues

2. What are proteoglycans?101
3. List the main functions of soft connective tissue102
4. What is mesenchyme?103
5. What is reticular soft connective tissue?104
6. What are the three main proteins of the ECM?105
7. What types of tissue are collagens 1, 2, 3 and 4?106
8. What are the functions of adhesive proteins in connective tissue?107
9. Which two layers does the basement membrane separate?108
10.What kind of charge do GAGs have?109
11.Why does soft connective tissue hold water well?110
12.What are the indigenous cells of the soft connective tissue?111
13.What are the immigrant cells of the soft connective tissue?112
101 Proteoglycans = glycosylated proteins (carbohydrate attached)
102 Space ﬁller and mechanical support, attachment and protection, highway for nutrients, storage of fat and
calcium, site of immunological defence
103 Embryonic loose connective tissue (stem cells)
104 Bone marrow, lymph nodes
105 Collagen, elastin, adhesive
106 Type 1 = skin, bone, tendons, Type 2 = cartilage, Type 3 = blood vessels, skin, Type 4 = basement
membrane
107 Cross-link cells of CT to collagen, bind to transmembrane receptors called integrins.
108 Separated the epithelial layer from the connective tissue, maintains integrity of tissues
109 High density of negative charge
110 Made up of sugar/carb based protein which do not fold into compact structures, and are hydrophilic so
water sucked into large gaps between molecules, also have an ʻosmotically active ion cloudʼ.
111 Fibroblasts (ECM producer), adipocytes (leptin secretion, fat storage), Mast cells (histamine secretion)
112 All white blood cells. Mostly leukocytes.

Structure of the Skin
1. How much of the body’s total weight is made up of skin (%)113
2. What is the difference between vellus hair and terminal hair?114
3. What type of epidermis is the keratinocyte the primary cell type for?115
4. What is the stratum spinosum or prickle cell layer?116
5. What is pemphigus?117
6. What is the granular layer?118
7. What is the cornified layer?119
8. How long does transit of cells from the basal layer to the cornified layer take?120
9. What pigment protects against UV light and what kind of cells produce this?121
10.What do Langerhans cells do? (not Islets of Langerhans)122
11.What is the dermis?123
12.What are Meissner’s corpuscles and Pacinian receptors?124
113 16%
114 Terminal is the densely packed coarse hairs found on the scalp, Vellus hair is sparse, fine body hair
115 Keratinised (tough) epithelium
116 The first layer of keratinised epidermis, held together by numerous desmosomes
117 A blistering disease due to antibodies attacking desminogen, a component of desmosomes, many of
which are found in the prickle cell layer
118 Cells begin to flatten as they approach the surface of the skin, this layer lies above the prickle cell layer
and below the cornified layer.
119 Cells getting even more flattened by this stage (squamous), keratins become linked by disulphide
bridges, cells begin to die and get densely packed together
120 25-30 days
121 Melanin produced by tyrosine melanocytes (tumours of melanocytes are called melanoma)
122 Macrophage like, immune defence
123 Main thickness of skin, conveys blood vessels, lymph and nerves
124 Meissnerʼs Light touch sensitive mechanoreceptors in the skin, Pacinian - heavy, pressure and vibration

13.What are the four skin appendages?125
14.What is the function of sebaceous glands?126
15.What are the five distinctive layers (concentric rings) of a hair follicle?127
Body Fluids and Blood
1. Name the three main fluid compartments in the body and the volumes/
proportion of fluid in them128
2. What is the water content of lean tissue in L/kg?129
3. Name 4 ‘transcellular fluids’ apart from those in (1)130
4. What is the dilution method?131
5. What substances could be used for the dilution method to determine plasma
volume?132
6. What factor determines the osmolarity of a solution?133
7. What is the difference between osmolarity and osmolality?134
8. How many mOsm/L if 10mmol/litre CaCl2?135
9. What is the osmolarity of plasma?136
125 Sweat glands, hair follicles, sebaceous glands, erector pilli muscle
126 Secrete lipid rich sebum which maintains suppleness of skin, into upper 3rd of hair follicles
127 Medulla (large hairs only), cortex, cuticle, inner root sheath, outer root sheath
128 Blood (5%, 3.5L), intracellular fluid (40%, 28L), interstitial space (15%, 10.5L)
129 0.71L/kg (about 70%)
130 CSF, synovial (joint) fluid, chorionic fluid (in the amniotic sac), aqueous/vitreous humour of the eye
131 Adding a known amount of substance to an unknown volume of fluid and measuring the concentration of
the mixture. Vol = amount of substance added
! ! ! concentration
132 Evans blue, labelled Inulin, Albumin
133 Total number of diffusible entities in solution (osmotic potential)
134 Osmolarity = 1 osmole per litre, Osmolality = 1 osmole per kg
135 x by the number of diffusible entities (i.e. elements in CaCl2), so x3 = 30mOsm/L
136 290mmol/L (very closely controlled) (or isotonic saline = 0.9% w/v)

10.What is the crystalloid osmotic pressure?137
11.What is colloidal osmotic pressure?138
12.What are the plasma concentrations of Na+, K+ and Ca2+ in mmol/L?139
13.What are the intracellular concentrations of Na+, K+ and Ca2+ in mmol/L?140
14.What is the concentration of plasma protein in g/L141
15.What proportion of blood is haemocrit?142
16.What is the average lifespan of a red blood cell?143
17.What are the 5 different types of white blood cell and their functions?144
18.What is the healthy range for blood platelet count?145
Striated Muscle and the Contractile Mechanism
1. What are epimysium, perimysium and endomysium?146
2. What are the sarcoplasmic reticulum and sarcolemma?147
3. What structure is made up by myofibrils?148
137 due to small diffusible ions (Na+, Cl- and K+ in body fluids), not proteins
138 osmotic pressure exerted by non-diffusible proteins such as albumin in plasma (about 25mmHg)
139 Na+ 140, K+ 4, Ca2+ 2
140 Na+ 10, K+ 120, Ca2+ 100
141 70g/L of which 48g is albumin
142 40-50%
143 120 days
144 Lymphocytes (produce Ig), Monocytes (macrophages), Basophils (release histamine), Esinophils
(phagocytosis), Neutrophils (phagocytosis)
145 150-400 x 10^9/Litre
146 Connective tirssue surrounding contractile layers. Epi = surrounds the muscle, Peri = surrounds bundles
of myofibres, End = surrounds single myofibres
147 Sarcolemma = electrically exciteable and propagates APs. SR = stores and releases Ca2+ in response to
AP insarcolemma
148 Myofibre (myofibrils are made up by myofilaments)

4. What are thick and thin filaments?149
5. Where is the Z line?150
6. What are dark bands?151
7. What is a sarcomere?152
8. What is the function of transverse tubules in the sarcomere?153
9. What is the name for the state where a muscle produces force but does not
shorten? e.g. when supporting a weight154
10.What is the process where a muscle produces force whilst also shortening?155
11.... and where the muscle exerts a ‘braking’ action when being stretched by the
action of other muscles?156
12.Which filaments contain the ‘heads’ which make the cross bridges?157
13.What are the two crucial binding sites on the cross bridge?158
14.What does raised Ca2+ do to the cross bridge and its binding?159
15.What is the force generating step?160
149 thick = myosin, thin = actin
150 anchors the actin fibres together, midline of the actin fibres and shows up as a ʻlight bandʼ.
151 Where there are thick (myosin) filaments
152 Distance between Z bands, the contractile unit of cardiac and skeletal muscle
153 bring the AP signal to the sarcomere to start conduction
154 Isometric contraction
155 Concentric contraction
156 Eccentric contraction
157 Myosin heads (thick filament)
158 Myosin and ATP
159 Causes it to bind actin and split the attached ATP into ADP and Pi
160 Energy in the strain between actin and myosin caused by new binding and conformation once ADP and Pi
have been released

16.What causes the cross bridge to detach?161
17.Which parts of the sarcomere shorten during contraction out of I band, A band,
Z line, H zone?162
18.What is the A band?163
19.What type of reaction is the breakdown of ATP into Pi and ADP?164
Skeletal Muscle and the Regulation of Contraction
1. What is end plate potential?165
2. Into which structure does the AP travel to initiate SR release of calcium in
response to local depolarisation?166
3. What initiates muscle relaxation?167
4. What molecule on the actin filament does Ca2+ bind to?168
5. What is the difference between a twitch and a tetanus?169
6. What length of contraction in ms is caused by a single twitch?170
7. What two regulating factors increase the force of a contraction?171
161 the binding of new ATP
162 I band (area of only thin filament) and H zone (area of only thick filament) both shorten as there is
increased overlap of myosin and actin filaments
163 Length of thick filament (myosin), does not change during contraction, only overlap changes
164 Hydrolysis
165 End plate potential = local depolarisation resulting from Na+ influx, causes and AP to propagate away
from the NMJ to both ends of the fibre
166 Triad
167 Ca2+ pumped back (returned) to SR
168 When Ca2+ binds to troponin (specifically TnC), the actin changes shape so the myosin cross bridge can
bind to actin by shifting the position of tropomyosin
169 Twitch is the brief mechanical response (contraction) to a single AP, in skeletal muscle twitch is always
longer than the AP whereas the opposite is true for cardiac muscle. A tetanus is the sustained mechanical
response to a series of APs.
170 100-300ms, anything longer requires tetanus and a series of APs
171 Motor unit recruitment and rate recruitment

Cardiac Smooth, Smooth and Skeletal Muscle
1. Which muscle cells are shortest and which are longest out of smooth, cardiac and
striated?172
2. In which muscle type are the cells linked mechanically and electronically to each
other by tight junctions and adherens junctions in structures called intercalated
disks?173
3. How are smooth muscle fibres coupled to each other mechanically?174
4. Which muscle type does not contain troponin and t-tubules?175
5. What is the ‘steric blocking mechanism’?176
6. Describe how the contractile mechanism (with reference to Ca2+ binding) works
in smooth muscle?177
7. What are the two sources of Ca2+ for the contractile mechanism in cardiac
muscle?178
8. How is the Ca2+ concentration fine tuned once it has been released by either of
these mechanisms?179
9. Given that smooth muscle has very little SR, how does it get most of its Ca2+?180
10.How is Ca2+ in smooth muscle cells lowered for relaxation?181
172 Skeletal = longest at 10,000micrometres, cardiac is 200 and smooth 150
173 Cardiac muscle
174 By ʻmembrane dense areasʼ, between thin filaments (actin). (and electically by gap junctions)
175 Smooth muscle
176 The ability of troponin/tropoimyosin to block Ca2+ binding mechanism in striated muscle
177 Ca2+ binds to calmodulin, which activates myosin light chain kinase, adding a phosphate to the myosin
light chain so that it can bind to actin. (Doesnʼt use troponin). Stops when another enzyme acts on it to
remove the phosphate.
178 Some enters from the SR like in skeletal muscle, some comes from the extracellular space through L-type
voltage gated Ca2+ channels via. calcium induced calcium release.
179 By Ca/Na exchangers on the sarcolemma
180 From the extracellular space by Ca2+ channels, these are opened by the binding of phospholipase 3 to
receptors releasing IP3 which acts on SR, which then acts on ion channels to cause Ca2+ influx from ECM
181 Pumped out by Ca2+ pumps, Na+/Ca2+ exchanger and back into SR

11.Which muscle type increases force by increasing Ca2+ concentration?182
12.Why does cardiac muscle not work on the optimum portion of the length-
tension curve?183
13.Which muscle type does not contain mechanical or electrical junctions?
14.Which muscle type relies purely on the slow release of Ca2+ to initiate
contraction?184
15.Which muscle type does not use Ca2+ to initiate the AP (although it is used in
the cross bridge cycle)?185
182 Cardiac muscle, not skeletal muscle
183 Because it needs to be adaptable so works on the ascending portion so that force of contraction can be
increased or decreased in response to stimuli
184 Smooth muscle - so it contracts slower but doesnʼt tire as easily
185 Skeletal

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