Week 3 Flashcards
1
Q
why are human cells soft?
A
human cells are soft due to a lack of cell wall, and a thinner, flexible cell membrane. this allows them to move and mould in the human body, and to inflate/deflate.
2
Q
what does the cell membrane do?
A
enclose and protect. regulate water/soltue intake
3
Q
cytoskeleton
A
mini ‘skeleton’ of protein inside the cell to give it structure.
4
Q
what is physiological homeostasis?
A
the maintanence of a constant internal environment
5
Q
what is an important homeostaticly controlled variable of the cells
A
the composition/tonicity of the fluid inside and outside your cells
6
Q
what is osmosis?
A
the process of water moving through a membrane from high concentrate to low concentrate.
7
Q
what % of your body is water? what are the other parts?
A
male: 60% water
female: 50%
+ proteins, fats, minerals
8
Q
why do women have lower water %?
A
because they tend to have a higher fat %
9
Q
what compartments of water are there in our bodies?
A
intracellular: 33% of body weight
interstitual: 21.5% (salty water in between cells)
plasma: 4.5%
other fluids (eg synovial fluid): <1%
10
Q
how much water do cells make as a biproduct of chemical reactions?
A
300ml per day
11
Q
what are the ways that the body looses water and how much?
A
urine - 1200ml
feces - 150ml
vapor (skin/lungs) - 1150ml
sweat glands - variable amounts
12
Q
what is the total that the body makes and looses in water everyday. how much is needed to drink to make up for the losses?
A
make 300ml
loose 2.5L
drink 2.2L to maintain equalibrium
13
Q
what does ICF and ECF stand for?
A
intracellular fluid and extracellular fluid
14
Q
what does isotonic mean?
A
loosing and gaining water and solutes at a equal balance as to not loose or gain any net fluid. the solution concentration stays at a normal balance.
15
Q
what is tonicity?
A
meause of effective osmotic pressure gradient. the concrentration of solutes dissolved inn the solution
16
Q
what causes death due to dehydration?
A
if extreme water loss occurs within the body (eg severe diareha), the amount of water in the ECF decreases, causes water to come out of the cells (bc of osmosis), to regain isonticity. this causes the cells to shrink inhibiting their function and eventually causes them to die.
17
Q
what does hypertonic mean?
A
more concentrated (less water) - shrinking cells
18
Q
what does hypotonic mean?
A
too much water - swelling cells
19
Q
how can you die from too much water?
A
if too much water is taken into your ECF then it causes more water travel through the cell membrane into the ICF, diluting the important solutes, flooding the cell and causing it to swell and eventually burst.
20
Q
what does hyponatremia mean?
A
too little sodium, too much water
21
Q
sodium
A
Na+
22
Q
potassium
A
K+
23
Q
how do our cells get ions/electrolytes?
A
through consumption - eating and drinking.
they absorb through the epipthelial lining in the small intestine/colon
24
Q
where are ions/electrolytes stored and lost?
A
stored in skeleton
secreted through sweat
primarily lost in kidney (removes excess)
25
what is the difference between ions and electrolytes?
electrolytes are the chemicals from which ions are made.
26
what are the 3 most important electrolytes to the function of the cell?
NaCl (sodium chloride) Na+ + Cl-
KCl (potassium chloride) K+ +Cl-
CaPO4 (calcium phosphate) Ca2+ +PO42-
27
what are Excitable tissues?
neurons and muscle (excitable cell membrane potential)
28
what does CMP stand for?
cell membrane potential
29
____ also have ___ ____ but arent excitable.
epithelial cells also have membrane potential but arent excitable.
30
what has to be controlled and maintained to sustain life in the cells?
voltage difference across the cell membrane between outside and in.
31
Cmp relies of the seperation of what ions?
K+ and Na+ seperated between the outisde and inside of the cell.
32
what is a cation?
a positively charged ion eg. K+, Na+
33
where are cations and anions found?
inside and outside of cells
34
what are some examples of cations and anions found inside and outside the cells
cations: sodium, potassium, calcium
anions: chloride, proteins
35
what does the lipid layer do?
it is a seperative membrane that keeps K+ and Na+ seperate
36
explain the distribution of Na+ and K+ inside and outside the cells:
ICF: low Na+, high K+
ECF: high Na+, low K+
37
what is membrane potential?
the distribution of ions that create electricity
38
what is the resting membrane potential?
-70mV (slightly negative on the inside)
39
what does being the ICF being slightly negative mean?
it creates a charge difference between the 2 sides of the membrane, like a small battery.
40
moving __ across the ____ uses a lot of ___.
ions, membrane, energy/ATP
41
how do the ions actually get into the cell?
through passageways in the plasma membrane that are made of proteins.
42
what swaps out the ions to maintain isotonic balance inside/outside the cell and what is it run by?
the sodium-potassium exchange pump. it is fuelled by ATP
43
if something happens to cause a ion channel to open too wide what will happen?
osmosis of the ions will occur - Na+ into the cell, K+ out of cell
44
what is depolarisation?
the loss of cell membrane potential (less than - 70mV) due to a disrupted balance of ions
45
what is repolarisation?
the cell membrane potential recovering from depolarisation (gaining mV)
46
what is hyperpolarisation?
when there is a rise in cell membrane potential (more than 70mV)
47
what are the 3 types of muscle?
smooth, cardiac, skeletal
48
what is the primary job of the skeletal muscle?
develop force and resist movement
49
muscle is not only used for movement but also:
maintain posture
50
explain how skeletal muscle cells can be so big, and how big are they.
20-100 microns, many nuclei and many blood vessels
51
because skeletal muscle has many blood vessels and nuclei:
it is quick to heal and excitable.
52
what are the secondary functions of skeletal muscle?
- support/protection of internal organs
- provide voluntary control over major openings (mouth, anus)
- converts energy to heat (shivering)
- major store for energy + protein.
53
which of the types of muscle are voluntary?
ONLY skeletal msucle
54
skeletal muscle is ensheathed in:
connective tissue
55
what us a bundle of muscle fibres?
fascicles
56
what is a fascicle?
a bundle of muscle fibres.
57
what do muscles start out as early in development?
myoblasts (single nuclei)
| then multi-nucleated cells enclosed in sarcomere/ cell membrane.
58
how many nuclei does each muscle fibre have and where are they roughly situated?
100s - 1000s, on the outside of the muscle fibre.
59
we can think iof the fibre as a ____ of _____ (which is:)
cylindar of cytoplasm (fluid solution, proteins + ions)
60
myofibres are made of:
which are:
made up of:
myofibrils
bundles of contractable proteins made of organised proteins that make up the length of the fibre. made up f myofilaments.
61
what are myofilaments made up of?
organised proteins: myosin and actin. look striped.
62
which is the thick and thing myfilaments?
actin thin
| myosin thick
63
if muscle fibre is damaged to the point of not being able to heal, it is ____. this allows for adaption (how? exaplain)
replaced. the muscle fibred will adapt to be bigger to cater for the new needs of the muscle.
64
what shape are the actin and myosin arranged into?
| what is their ratio to each other?
```
hexagonal array (striped)]
1:6 thick to thin (myosin to actin)
```
65
what is sarcolema?
| what % of the sarcolema is invaginated?
specialised plasma membrane. penetrates into the cell at some points. helps disperse AP making the whole muscle move all at once. 80-90% invaginated.
66
what are transverse tubules?
| what do they do?
extensions (invagination) of the surface membrane that run from the cell surface membrane into the fibre (net-like). they conduct electrical systems into the core of the fibre.
67
what is the sacroplasmic reticulum?
| What does it contain?
an extensive membranous tubula network associated with the T tubules at regular intervals. (a type of specialsed endoplasmic reticulunm)
Contains calcium for the cell.
68
What is the terminal cisternae?
The enlarges part of the SR that is where the t tubules come down.
69
What is a triad?
The triad is the spot at which there is a xombo/ overlap of the t tubules, terminal cisternae, and the SR.
70
Ttubule recieves:
| SR releases ____ into ____
Action potential signal
| Ca into the cytoplasm
71
Why do the myofilaments have a sa____ structure?
Sarcomeric structure
| Because of the arrangements of contractile proteins
72
What kind of protein is actin?
| what is attached to the actin at regular intervals?
Myofilament, globular protein
| Tropomyosin
73
What is troponin?
It is a globular protein that binds tropomyosin and actin together.
74
The heads if myosin can ____ ATP to release ____
Hydrolyse
| Energy
75
What is the epimysium?
The covering / protecting layer that covers the fibre.
76
Larger muscle =
More fibres in the fasciculi
77
What is the sarcomere?
Repeated segmants if the myofibrils that are the basis of muscle contraction theory.
78
What is the neuromuscular joint?
A myelinated axon of the motor neuron that terminates at a single point on the muscle fibre.
It is a specialised synapse.
79
What does myelinated mean?
Enclosed in myelin sheath
80
What is an axon?
A nerve fibre that conducts electrical impulses (AP)
81
How many contacts with motor neurons does a muscle fibre have and what does that contact form?
One motor neuron at one site, to form an excitatory synapse
82
NMJ is the synapse between:
The muscle fibre and the motor neuron.
83
What does the motor neuron tell the muscle fibre when it sends a signal?
Tell
84
The motor neurons of the spine connect to the muscle fibres through their axon. The whole unit is called the motor unit.
:)) u got this babes
85
What is atrophy?
Tissue wasting away
86
Where are motor neurons found?
The anterior part of the spinal cord.
87
Where do the axons come out if and what do they form?
Come out if the motor neurons in spinal cord and form nerve roots and spinal nerves.
88
The ____ the motor units = the more ____
Bigger, force
89
what are muscle contractions triggered by? (basic)
electrical events called Action potentials.
90
show the path of the action potential:
brain - down spinal cord - motor neurons - axons - fibres - NMJ
91
what does the AP do when it reaches the NMJ?
it initiates synaptic tranmission, which generates AP in the postsynapticmsucle fibre (muscle fibre after the NMJ).
92
what does the postsynaptic AP do?
triggers excitation - concentration coupling that causes force in the muscle.
93
what is neuromuscular transmission?
when the AP invades the motor nerve terminal NMJ which causes depolarisation which causes release of neurotransmitters (ACh)
94
what kind of synapse is NMJ?
chemical cholinergic synapse
95
what is ACh?
a neurotransmitter called Acetyl Choline which initiates AP in the surface of the muscle fibre.
96
how are the calcium channels in the NMJ synapse opened?
they are voltage triggered and so are opened by AP
97
When the calcium channels are opened what happens?
calcium ions then enter bc of osmosis, and diffuse into the axon terminal. they then trigger synaptic vesicles to release ACh by exocytosis (which means transported to the membrane)
98
what happens after the release of ACh?
ACh diffuses across the synaptic cleft then binds sodium ion channels and causes graded depolarisation.
99
what does graded depolarisation mean?
It is described as 'graded' because its size and duration are proportional to the stimulus responsible for it
100
what happens once the ACh causes depolarisation?
ACh is broken down into acetate and choline by AChE, ending depolarisation.
101
once the ACh is broken down into acetate and choline what happens?
the axon terminal reabsorbs and recylces the choline to make more ACh.
102
how does the depolarisation spread over the whole motor unit?
the NMJ is only the middle 3rd of the fibres length so the wave of depolarisation has to spread through the sarcalemma away fro the NMJ in all directions.
103
where does the wave of depolarisation go after the sarcolemma?
down the t tubule to the core of the fibre. it then reaches the triad.
104
what does the depolarisation reaches the triad, what happens?
it causes CA channels to open in the SR membrane. the CA then diffuses from the inside of the SR (high conc) to the sarcoplasm.
105
explain the basic steps of excitation 0 contraction coupling:
1. AP from nerve causes synaptic transmission @ NMJ to trigger AP in muscle fibre.
2. Ap spreads over sarcolemma, to t tubule
3. depolarisation within t tubule system triggers release of CA from terminals in SR
4. CA into sarcoplasm, CA binds to troponin C molecule
5. binding of CA causes troponin to change shape, exposing actin binding site.
6. myosin heads bind to actin
7. cross bridges are formed and force is generated!!
106
when at rest, ca levels are very:
| in the :
low in the fibres cytoplasm
107
during E - C coupling what state are the myosin heads?
cocked/extended
108
during E - C coupling ATP is:
hydrolysed (broken down through water chem reaction) by ATPase. ADP and Pi remain bound to the myosin head. energy is released.
109
during E - C coupling:
| what is done with the energy released by the hydrolysis of the ATP?
it is used to cock/extend the myosin heads.
110
during E - C coupling:
| what does the CA do when it goes down the t tubule?
initiates contraction cycle.
111
explain the brief steps of th cross bridge cycle:
1. rest, CA levels low, ATP is hydrolysed, energy is used to cock myosin heads
2. CA binds to troponin changin its shape to make actin/myosin binding available.
3. myosin heads bind to actin binding site, forming cross bridges.
4/5? after nthe bridge forms, the ADP and Pi (are bound together) are released from myosin head, which causes a change in the shape of the head, then flexes (power stroke) The filaments are then pulled together generating force.
6. after ADP and PI are released fr the myosin head the binding site is exposed and ATP binds to the head. this lowers the affinity of myosin to actin, the myosin detaches, and the cross bridges are broken.
7. the cycle is repeated once more, as long as CA and ATP are present. during each muscle contraction millions of these cyckes happen at billions of different cross bridges.
112
explain what happens when ATP is hydrolysed by myosin ATPase:
ADP, Pi remain bound to myosin head, energy is released that can now be used to extend myosin head.
113
explain cycle 1 of cross bridge cycle:
1. rest, CA levels low, ATP is hydrolysed, energy is used to cock myosin heads
114
explain cycle 2 of cross bridge cycle:
2. CA binds to troponin changin its shape to make actin/myosin binding available.
115
explain cycle 3 of cross bridge cycle:
3. myosin heads bind to actin binding site, forming cross bridges.
116
explain cycle 4/5 of cross bridge cycle:
4/5? after nthe bridge forms, the ADP and Pi (are bound together) are released from myosin head, which causes a change in the shape of the head, then flexes (power stroke) The filaments are then pulled together generating force.
117
explain cycle 6 of cross bridge cycle:
6. after ADP and PI are released fr the myosin head the binding site is exposed and ATP binds to the head. this lowers the affinity of myosin to actin, the myosin detaches, and the cross bridges are broken.
118
explain cycle 7 of cross bridge cycle:
7. the cycle is repeated once more, as long as CA and ATP are present. during each muscle contraction millions of these cyckes happen at billions of different cross bridges.
119
what are the main 2 things the cross bridge requires to continue?
ATP abnd CA
120
how cross bridge cycles happen for a muscle to contract?
during each muscle contraction millions of these cyckes happen at billions of different cross bridges.
121
explain why it is saisd that the myosin 'walk':
during the contraction of the croos bridge cycle, the myosin 'walk' along the actin as they are pulling the ends of the sarcomere closer together.
122
when is the contraction of a muscle terminated?
when the CA concentration falls, repolarisation.
123
what happens after the contraction is terminated?
the CA is pumped out of the sarcoplasm back into the SR by the SR pump which uses ATP to move CA into SR against its concentration gradient.
124
what are the specific terms 'excitation' and 'contraction' refering to in E - C coupling?
excitation - AP in the motor nerve + muscle fibre
contraction - development of tension by the actin/myosin interaction.
E - C coupling is the coupling of the 2.
125
what can a single AP do in E - C coupling?
release a pulse of CA into the sarcoplam, resulting in a short tension of the muscle fibre.
126
what is the result of many APs fired?
| ???
many APs fired in rapid sequence results in a sustained release of CA from the SR, and so a sustained period of contraction ensues, which is called tetanus.
127
what is the primary job of skeletal muscle?
develop force and apply it to the skeleton. postural control, limb/body movements
128
what are some factors that determine the amount of force that is delivered?
- amount of force produced by each fibre
- the number of fibres activated
- the more cross bridges the more force
129
what is a determinant of the number of cross bridges that can form?
the sarcomeres length.
| More cross bridges the more force, larger sarcomere is more force, big muscle = strong muscle (to a certain extent)
130
the amount of force the sarcomere can produce is maximal when:
there is the most overlap between thick and thin filaments (myosin, actin). force falls to 0 when they arent overlapped at all, force also declines if the myofilaments overlap too far and interfere with the cross bridges.
131
as a sarcomere gets longer, what happens to force?
as it gets longer, the actin and myosin filaments are less overlaped which results in less force, however as they get longer there can be more cross bridges, so every muscle has an optimal length at which it has the most force.
132
the amount of force a fibre can produce is proportional to:
the frequency of its stimulation (how much it is used)
133
what is rate coding?
As the frequency of AP (fr stimulus) increases, the amount of force produced byut the fibre increases (up to the fibre limit).
134
what is summation?
Summation occurs as successive stimuli are added together to produce a stronger muscle contraction, the gradual increase of force.
135
how is maximum force produced (what kind of stimulus)?
contractions arent stop/go, but are sustained and constant.
136
what is recruitment?
the amount of force a whole muscle can produce is based on the force produced by each fibre, and the number of fibres activated. Recruitment is activating more motor units to increase the force.
137
why are different motor units activiated at different times?
| why are all motor units not always activated?
activating different motor untis in tunrs means that muscle tension can be maintained whilst allowing for some units to rest.
if the muscle produces less than maximum force it was stay active for longer.
