1. tissues Flashcards
1
Q
summarise the lipid distribution in the plasma membrane
A
extracellular half;
phospholipid choline (PC), glycolipids
intracellular half;
Phosphatidylserine (PS), Phosphatidylethanolamine (PE) and Phosphatidylinositol (PI)
*cholesterol is distributed evenly between the two halves
phospholipids are a class of lipids containing a hydrophilic head (phosphate group) and two hydrophobic tails (fatty acids)
*heads face outwards.
uneven distribution of phospholipids (3 in the intracellular and 1 extracellular)
**lots of proteins associated with membrane
2
Q
FRAP
A
Fluorescence recovery after photobleaching (FRAP) is a standard technique used to study the diffusion properties of biomolecules in artificial or cell membranes.
3
Q
what does it mean that the proteins associated with the membrane are dynamic?
A
Dynamic Regulation of Plasma Membrane Protein Organization
Protein function is often directly coupled to lateral organization by clustering proteins in functional membrane domains or separating them in different domains. The formation of protein domains occurs over a broad range of length scales and is highly dynamic.
the “dynamic” nature of membrane-associated proteins means that they are constantly in motion, adjusting their positions, structures, and interactions to enable proper cellular responses and functions.
4
Q
what type of adult cell does not generally replicate?
A
neurons
5
Q
what is the nucleus of a cell important for?
A
for protein synthesis
6
Q
what are some common components of an animal cell?
A
endosome
peroxisome
free polyribosomes
plasma membrane
nucleus
endoplasmic reticulum with membrane-bound polyribosomes
mitochondrion
golgi apparatus
lysosomes
cytosol
7
Q
function of ER
A
The ER is the largest organelle in the cell and is a major site of protein synthesis and transport, protein folding, lipid and steroid synthesis, carbohydrate metabolism and calcium storage
8
Q
golgi apparatus function
A
a factory in which proteins received from the ER are further processed and sorted for transport to their eventual destinations: lysosomes, the plasma membrane, or secretion.
9
Q
spectrin and ankyrin
A
Spectrin and ankyrin are membrane skeletal proteins that contribute to mechanical support of plasma membranes and micron-scale organization of diverse membrane-spanning proteins.
10
Q
summarise glucose uptake in the gut
A
epithelial tissue lines the gut with microvillus for increased surface area and therefore increased absorption.
Na+/K+ ATPase is important for maintaining the Na+ gradient, which drives the apical absorption of glucose in SGLT1.
Glucose enters the epithelial cells by a process catalyzed by the cotransporter SGLT-1. Intracellular cAMP activates the transepithelial transport by a mechanism possibly involving phosphorylation of SGLT-1. The glucose accumulated intracellularly can diffuse out of the cells by facilitated diffusion through GLUT2 into the blood stream.
*significantly more glucose transporters in apical membrane vs basal
[Sodium/glucose cotransporter 1]
11
Q
Na+/K+ ATPase
A
The sodium-potassium pump system moves sodium and potassium ions against large concentration gradients. It moves two potassium ions into the cell where potassium levels are high, and pumps three sodium ions out of the cell and into the extracellular fluid.
3Na+ out
2K+ in
12
Q
apical vs basal membrane
A
The membrane facing the lumen or free surface is known as the apical membrane, while the membrane oriented away from the lumen, contacting the extracellular matrix, is known as the basal membrane and the sides of the cell contacting the neighbouring cells form the lateral membrane
The Apical surface faces lumens or outside environments, showcasing Specialised systems for features including absorption or secretion. Contrastingly, the basal surface adheres to the basement membrane, offering structural help and anchorage to underlying tissues.
*significantly more glucose transporters in apical membrane vs basal in epithelial cells lining lumen of small intestine
13
Q
mechanisms of protein transport
A
Protein sorting occurs through three mechanisms: gated transport, transmembrane transport, and vesicle transport, all utilizing sorting signals—short. Gated transport involves nuclear localization signals (NLS) allowing proteins to enter the nucleus via nuclear pores.
From the endoplasmic reticulum, proteins are transported in vesicles to the Golgi apparatus, where they are further processed and sorted for transport to lysosomes, the plasma membrane, or secretion from the cell.
14
Q
secretory pathway of proteins
A
The secretory pathway ensures the transport of proteins from the endoplasmic reticulum (ER) via the Golgi complex to their destination compartment, such as the cell surface, the endosomes or the lysosomes
rough ER → Golgi → secretory vesicles → cell exterior
15
Q
TIM/TOM complex mitochondria
A
The TIM/TOM complex is a protein complex in cellular biochemistry which translocates proteins produced from nuclear DNA through the mitochondrial membrane
TOM complex is outer membrane. TIM is inner membrane. TOM allows precursor protein to move through mitochondrial membrane. It then passes through TIM complex to pass into the mitochondrial matrix. (proteins within matrix will cleave signal peptide)
16
Q
precursor protein
A
A protein precursor, also called a pro-protein or pro-peptide, is an inactive protein (or peptide) that can be turned into an active form by post-translational modification, such as breaking off a piece of the molecule or adding on another molecule.
Signal sequences are N-terminal extensions of nascent polypeptide chains that mediate protein targeting to the membrane of the endoplasmic reticulum (ER).
17
Q
transcription vs translation
A
The process by which DNA is copied to RNA is called transcription, and that by which RNA is used to produce proteins is called translation.
18
Q
translation
A
The process through which information encoded in messenger RNA (mRNA) directs the addition of amino acids during protein synthesis
- mRNA binds to the ribosome. mRNA binds to the ribosome. This binding is helped by the 5’ cap of the mRNA, which the ribosomes recognise and bind to. The poly-A tail of the mRNA also binds to the ribosome in order to increase translational efficiency.
- The ribosome reads the first codons. The ribosome reads the codons on the mRNA, beginning with the start codon “AUG”.
- A tRNA will bring the complementary amino acid for the first codon. Amino acids are found in the cytoplasm. Each specific tRNA has a complementary amino acid, and can bring it over. This is an ATP driven process (it requires the hydrolysis of ATP). As the start codon is “AUG”, the first amino acid will be methionine, brought by a tRNA with the anti-codon “UAC”.
- Another tRNA brings the second amino acid. The ribosome continues to read the next codon, and another tRNA brings the correct amino acid.
- The first tRNA leaves. The first tRNA is then released from the ribosome, and the second tRNA takes its place. This process is repeated for each codon that the ribosome reads.
- A peptide bond forms. A peptide bond forms between the two amino acids. An enzyme called aminoacyl transferase catalyses this.
- The process continues until a stop codon is reached. Ribosomes continue this process until they reach a stop codon on the mRNA. Stop codons are either “UAA”, “UGA”, or “UAG”. tRNAs do not have anti-codons for stop codons. Once the ribosome recognises the stop codon, a terminating factor catalyses the hydrolysis of the bonds between the final tRNA and the amino acid chain, which then releases the polypeptide chain.
- After translation, the polypeptide chains are folded. This folding is a spontaneous process but is also guided along by specialised proteins.
- Polypeptides can also undergo post-translational modifications. Modifications can occur. For example, carbohydrate chains can be added onto proteins, depending on the type of protein and its function. Also, all polypeptide chains start with methionine, but in some proteins this starting methionine can be cleaved off following translation.
- Proteins destined to leave the cell go to the rough ER. Proteins that need to be secreted from the cell are translated and folded in the rough endoplasmic reticulum. Ribosomes can recognise if a protein is meant to be secreted. If this is the case, the ribosomes will attach themselves to the rough endoplasmic reticulum, and the translated polypeptide chain will be released into the lumen of the endoplasmic reticulum where it will be folded and packaged for secretion and sent to the Golgi apparatus.
- Proteins destined to stay in the cell go to the cytoplasm. Proteins meant for use inside of the cell are synthesised and released into the cytoplasm.
19
Q
SRP
A
The signal recognition particle (SRP) is a ribonucleoprotein particle essential for the targeting of signal peptide-bearing proteins to the prokaryotic plasma membrane or the eukaryotic endoplasmic reticulum membrane for secretion or membrane insertion.
SRP locks to ribosome and signal complex of protein. Whole protein SRP complex binds to receptor protein which omits opening of translocator and docking of translocator.
20
Q
vesicles and protein transport
A
A vesicular transport protein, or vesicular transporter, is a membrane protein that regulates or facilitates the movement of specific molecules across a vesicle’s membrane. As a result, vesicular transporters govern the concentration of molecules within a vesicle.
The finished new proteins end up in the trans Golgi network, which packages them in transport vesicles and dispatches them to their specific destinations in the cell.
Newly formed protein buds off from vesicle when it fuses with plasma membrane. Secretory vesicle fuses with plasma membrane and protein is released through exocytosis.
21
Q
which neurotransmitter does not get processed in ER?
A
acetyl choline
22
Q
acetylcholine
A
neurotransmitter (released by neuron )
acetylcholine is released from nerve cells at the neuromuscular junction via calcium mediated exocytosis.
acetylcholine binds to receptors on skeletal muscle to cause contraction.
botox can block this muscle relaxation.
causes muscle contraction; botox prevents muscle contraction so can be used medically to prevent issues like muscle stiffness/excessive swearing but is now more often used for aesthetic purposes.
23
Q
how does botox work?
A
SNARE- soluble NSF attachment protein receptor
v-SNAREs- found on vesicles
t-SNAREs located in the target membrane
botox cleaves SNARE proteins
fusing of vesicle to membrane for release of acetylcholine at the neuromuscular junction but botox cleaves this so acetylcholine is not released.
Botulinum Neurotoxin causes functional damage to SNARE proteins, which has significant physiological and medical implications. By damaging SNARE proteins, the toxin prevents synaptic vesicles from fusing to the synaptic membrane and releasing their neurotransmitters into the synaptic cleft.
24
Q
function and main components of the cytoskeleton
A
cell shape
mechanical support for the cell and tissues
cellular locomotion
intracellular movements of cytoplasm, organelles and chromosomes
microfilaments
microtubules
intermediate filaments
*gives cell distinctive shape and is vital for movement of cells
25
describe the components of the cytoskeleton
intermediate filaments
microtubules
actin filaments
Intermediate filaments provide mechanical strength and resistance to shear stress. Microtubules determine the positions of membrane-enclosed organelles and direct intracellular transport. Actin filaments determine the shape of the cell's surface and are necessary for whole-cell locomotion
microtubules are largest with diameter of ~25nm composed of protein called tubulin
intermediate filaments have diameter of ~10nm
actin filaments are smallest with diameter of ~7nm composed of protein called actin
26
give examples of actin structures
severing protein
cross-linking protein (in cell cortex)
capping (+end blocking) protein
side-binding protein
myosin motor protein
bundling protein (in filopodia)
nucleating protein
actin monomers
monomer-sequestering protein
27
actin organisation is skeletal muscle
The striations of skeletal muscle are created by the organization of actin and myosin (thick) filaments resulting in the banding pattern of myofibrils. These actin and myosin filaments slide over each other to cause shortening of sarcomeres and the cells to produce force.
28
actin organisation within neurons
Actin filaments (microfilaments) form a dense network close to the neuronal membrane.
They give the neuron its shape and allow motility.
Structural organization of actin filaments within neuronal subcellular compartments. The actin cytoskeleton has a highly specialized organization of dynamic filaments in different subcellular compartments. This allows it to support a diversity of functional requirements in neuronal cells.
29
what are the different names given to intermediate filaments in different cells.
cytoplasmic:
keratin filaments (in epithelial cells)
vimentin and vimentin-related filaments (in connective-tissue cells, muscle cells, and glial cells)
neurofilaments (in nerve cells)
nuclear:
nuclear lamins (in all animal cells)
**intermediate filaments provide strength and stability - 'bones' of the cytoplasm
30
function of intermediate filaments
to provide strength and stability - the 'bones' of the cytoplasm
31
function of actin filaments
Actin filaments are particularly abundant beneath the plasma membrane, where they form a network that provides mechanical support, determines cell shape, and allows movement of the cell surface, thereby enabling cells to migrate, engulf particles, and divide.
32
function of microtubules
Microtubules are major components of the cytoskeleton. They are found in all eukaryotic cells, and they are involved in mitosis, cell motility, intracellular transport, and maintenance of cell shape.
33
microtubule organisation
In the cytoplasm, microtubules grow from specialised centres called microtubule organising centres (MTOCs).
These control the number, position, and orientation of microtubules in the cytoplasm.
In animal cells, the major MTOC is the centrosome, usually found at one side of the cell nucleus
*composed of alpha and beta tubules (gamma at the non-growing, negative end?) - γ-tubulin is a member of the tubulin superfamily thought to be important for microtubule nucleation and minus end capping.
34
basal body in eukaryotic cell
microtubular structure at base of cili in a cell
The basal body (also known as the kinetosome) is a highly conserved cellular organelle discovered over one hundred years ago. Basal bodies are barrel-like microtubular structures located near the cell surface that provide the template for the nine-fold symmetry upon which the cilium is assembled.
35
microtubules and cell division
During mitosis, microtubules similarly extend outward from duplicated centrosomes to form the mitotic spindle, which is responsible for the separation and distribution of chromosomes to daughter cells.
36
intracellular transport - kinesins and dyneins
(motor proteins facilitate movement of different proteins)
Kinesins and dyneins use their head groups to walk along microtubules in opposite directions.
Most kinesins move along microtubules towards the + end.
All dyneins move along microtubules towards the - end.
Proteins transported may be enzymes, receptors, neurotransmitters etc.
*uses ATP
37
comment on protein transport in neurons
Protein transport is really important in neurones as axons have no ribosomes so theres no protein synthesis; proteins still need to be transported and this is done by microtubules.
38
what are the four tissue types?
1. connective
(packaging/supporting fabric)
2. nervous tissue
(nerve and glial cells)
3. muscle
(generates force so produces movement)
4. epithelia
(sheets of cells covering body surfaces)
39
functions and characteristics of epithelium
basic cell type
tight cohesive sheet
covers and protects surfaces
line internal cavities and vessels
forms glandular structures
form barriers
combines with nervous tissue to make special senses.
Epithelial tissue is highly cellular.
Epithelial cells bind to each other and to basement membrane via adhesions/junctions.
Epithelial tissue is avascular (no blood vessels).
Capable of regeneration- important in tissues experiencing wear and tear.
Derived from all 3 germinal layers- ectoderm, endoderm and mesoderm.
Structurally and functionally distinct cell surfaces= polarity
- free apical surface (not attached to other cells, often lines lumen of ducts and cavities)
- lateral surface (attached to other epithelial cells)
- basal surface (attached to basement membrane which attaches epithelia to underlying tissues)
*each surface can have own specialisations
40
what are the three germinal layers?
1. ectoderm
2. endoderm
3. mesoderm
The three germ layers are the endoderm, the ectoderm, and the mesoderm. Cells in each germ layer differentiate into tissues and embryonic organs. The ectoderm gives rise to the nervous system and the epidermis, among other tissues.
The ectoderm gives rise to the skin and the nervous system. The mesoderm specifies the development of several cell types such as bone, muscle, and connective tissue. Cells in the endoderm layer become the linings of the digestive and respiratory system, and form organs such as the liver and pancreas
41
what are the surfaces of epithelial cells?
free apical surface: not attached to other cells, often lines lumen of ducts and cavities.
lateral surface: attached to other epithelial cells
basal surface: attached to basement membrane which attaches epithelia to underlying tissues.
**structurally and functionally distinct cell surfaces= polarity
- each surface can have own specialisations
42
apical specialisations of epithelial cells
1. microvilli
cytoplasmic protrusions 'brush border'. Often found on epithelium lining internal passages. Increases surface area.
2. Stereocilia
similar to microvilli but longer. Non-motile unlike cilia. Limited distribution- eppididymis/vas def and sensory hair cells inner ear.
3. Cilia
motile hair-like protrusions. Several hundred per cell. Beat in coordination to move substances over the. Found in respiratory epithelium and fallopian tubes. Smoking reduces cilia movement = impaired movement of mucous = reduced protection against bacteria.
*microvilli increase surface area- this specialisation is often found in areas where substance exchange occurs
stereocillia are not very common; only really found in ear and in the male reproductive system.
43
EM vs LM
electron microscopy vs light microscopy
44
what are junctions on epithelial cells?
specialisation at basolateral surface between cells or with underlying basement membrane
*epithelial cells
45
what are the functions of junctions on epithelial cells?
(specialisation at basolateral surface between cells or with underlying basement membrane)
maintain polarised state
join cells together
exchange info and metabolites
*specialisation help the cells to anchor together. help to maintain a polarised state
[basolateral membrane is to take up metabolic waste products into the epithelial cell for disposal into the lumen where it is transported out of the body as urine.]
46
what is the basolateral surface?
The surface of an epithelial cell that adjoins underlying tissue.
*the term basolateral membrane refers to the cell membrane which is oriented away from the lumen of the tubule, whereas the term apical or luminal membrane refers to the cell membrane which is oriented towards the lumen.
47
what are three junction types?
1. occluding/tight junctions
seals cells together, prevents leaving
zona occludens- apical part of lateral domain, almost fusing 2 cells
2. anchoring junctions
mechanically attaches cells to neighbours
abundant in tissue subject to severe stress e.g. skin/cardiac muscle
zona adherent or demosomes- strong junction joining cells at lateral domain
hemidesmosome- strong in basal domain
2. communicating/gap junction
- passage of chemicals/electrical signals between cells
48
what type of junction are zona occludens? and what do they do?
occluding/tight junctions: seals cells together, prevent leaking
zona occluddens- apical part of lateral domain, almost fusing 2 cells
*helps cells seal, found in places where you do not want things getting into epithelial cell- found in places such as brain
49
what type of junction are zona adherens/demosomes and hemidesmosome?
anchoring junctions: mechanically attaches cells to neighbours- abundant in tissue subject to severe stress e.g. skin/cardiac muscle
zona adherens/desmosomes- strong junctions joining cells at lateral domain
hemidesmosome- strong in basal domain
*get these where there is a lot of movement and a lot of stress (cardiac and skin tissue experiences a lot of stress)
50
desmosomes vs hemidesmosomes
desmosomes (zona adherents) are strong junctions joining cells at lateral domain
hemidesmosome are strong in basal domain
*both anchoring junctions= mechanically attaches cells to neighbours, abundant in tissue subject to severe stress e.g. skin/cardiac muscle
51
what type of junction allow cells to communicate with each other through the passage of chemical/electrical signals between cells?
communicating/gap junctions
52
epithelial cell functions
1. protecting underlying structures
2. permitting the passage of some substances through it (any substance entering/leaving body must cross epithelium, some epithelia more permeable than others)
3. barrier to prevent many substances from moving through it
4. secreting substances (discharges onto epith surface or released into body/blood)
5. provide sensations (large sensory supply to provide info about environment)
53
how are epithelia classified?
number of layers:
simple= single layer, goof for absorption/secretion, fragile
stratified= 2 or more layers of cells, good for protection
pseudostratified= one layer of mixture of cell shapes
shapes of cells:
squamous= flat shaped
cuboidal= cube shaped
columnar= tall cylindrical shaped
transitional= readily change shape, accommodates stretching
surface specialisations:
cilia, keratin etc.
in most cases epithelium is given 2 names (simple squamous, stratified cuboidal etc)
= number of layers + shape of cell at free surface
*surface specialisations can also be added
54
what are the three different layers to classify epithelia?
1. simple (single layer, good for absorption/secretion, fragile)
2. stratified (2 or more layer of cells, good for protection)
3. pseudostratified (one layer or mixture of cell shapes- looks like a lot of layer but theres only one)
55
what are the 4 different shapes of cells used in the classification of epithelial cells?
1. squamous (flat shapes)
2. cuboidal (cube shapes)
3. columnar (tall cylindrical shapes)
4. transitional (readily change shape, accommodates stretching)
56
simple squamous epithelial
structure: single structure of flat, often hexagonal cells: nuclei appear very flat
function: diffusion, filtration, some secretion, absorption, little barrier/protection against friction
location: lining of blood vessels and the heart, alveoli, etc
*very little structural protection because its single cell but is good for exchange
57
simple cuboidal epithelium
structure: single layer of cube shaped cells, some cells have microvilli or cilia
function: good for diffusion, secretion and absorption, movement of particles embedded in mucus out of the terminal brochioles by ciliated cells
location: kidney tubules, glands, lining of terminal bronchoiles of the lungs etc.
58
microvilli vs cilia
Cilia are longer and thicker than microvilli. Cilia can move while microvilli cannot. Cilia look more like hairs, while microvilli are folded cell membranes.
Cilia are longer, thicker, and motile, used for movement, while microvilli are smaller, thinner, and non-motile, primarily used to increase surface area for absorption
59
simple columnar epithelium
structure: single layer of tall, narrow cells, some cells have cilia or microvilli
function: movement of substances, absorption and secretion. offer more protection than flatter cells
location: glands and some ducts, bronchioles of lungs, stomach and intestines etc
*gone columnar because they need to do a little more than the cuboidal ones. often secreting mucous and have to house goblet cells which secrete mucous. nuclei is at the basement membrane to protect it from the apical surface which might be at small intestine and have a low pH etc. there might be apical specialisations such as cilia. lost diffusion function because of shape.
60
comment on smoking and the destruction of epithelium
there should be columnar cells with cilia in the brinchoiles but smoking replaces these with the wrong cell type- lots of squamous cells (flat shaped).
this changes the cell type and function and is not the innate cell type- impacts function of bronchoiles. build up of nasty substances within these cells which ends up in an unhealthy lung.
*don't yet know the impact of vaping but it is being researched
61
stratified squamous epithelia
structure: multiple layers of cells that are cube-shaped in the basal layer and progressively flattened toward the surface. can be nonkeritinised (moist) or keritinised.
function: protection against abrasion. a barrier against infection, reduction of water loss from the body.
location: keritinised (skin), nonkeritinised (mouth, larynx, esophagus, anus etc)
*need to look at the cells closest to apical surface to classify the,
**stratified squamous epithelium prevents dehydration by preventing water loss
62
keritinised vs nonkeritinised stratified squamous
nonkeritinised (moist); found in mouth, larynx, esophagis, anus etc. has layers of fluid covering outermost layers of cells- males them moist.
keritinsed; skin, gums, hard palate of mouth. living cells in deepest layers but outer layers contain keratin (DEAD). dry and moisture resistant. keratin gets added at bottom of basement membrane the cells then eventually die. this means that when something scrapes the tissue it affects dead cells rather than healthy ones.
63
living layer of skin
epidermis
Stratum basale (stratum germinativum; pronounced stray-tum bay-say-lee or stray-tum germ-in-a-tie-vum). The stratum basale is in the deepest layer of your epidermis. New skin cells develop in this layer. It also contains the keratinocyte (cur-at-in-o-site) stem cells, which produce the protein keratin.
*keritinised dead skin on top
64
how are burns classified?
first degree is the epidermis
second is into the dermis
third is through the dermis to tissue underneath (potentially connective)
65
stratified cuboidal epithelium
structure: multiple layers of cube-shaped cells
function: secretion, absorption, protection against infection
location: (RARE), sweat gland ducts, ovarian follicular cells, salivary gland ducts
*rare configuration of tissue. involved in secretion and some absorption. there to protect against infection and is therefore beneficial to have multiple layer. secretion tends to be more watery.
66
stratified columnar epithelium
structure: multiple layer of cells with tall, thin cells resting on layers of more cube shaped cells. can be ciliated as in the larynx.
function: protection, secretion but no absorption
location: mammary gland ducts, larynx, a portion of the male urethra
67
pseudostratified columnar epithelium
structure: technically a single layer of cells but some cells reach the free surface and other do not, nuclei are at different levels so appears stratified. almost always ciliated and are associated with goblet cells.
function: synthesise and secrete mucus and move mucus (or fluid) that contains foreign particles over the surface of the free surface and from passages.
location: lining of nasal cavity, pharynx, trachea, bronchi of the lungs etc
*have goblet cells containing mucous therefore function is to secrete mucous. very much linked to respiratory system
68
transitional epithelium
unique type of stratified epithelium
(stratified= 2 or more layer of cells, good for protection)
lines urinary bladder, ureters, pelvis of kidney and superior part of urethra (structures where considerable expansion occurs, tolerated stretching and recoil without damage)
cell shape and number of layer vary depending on how stretched it is (not stretched= cuboidal/columnar, stretched= flattened/squamous) *as stretched, cells shift on one another so number of layer decreases from 5/6/ to 2/3
*only get this in the renal system. changes number of layer in response to the volume of fluid. needs to tolerate stretch/recoil and nasty chemicals.
structure: stratified cells cube shapes when organ or tube not stretched. squamous when organ or tube is stretched. number of layers also decrease on stretch.
function: accomodate fluctuations in the volume of fluid in organs or tubes. protects against caustic effects of urine.
*caustic= property of being able to erode organic tissue
location: lining of urinary bladder, ureters superior urethra
*when bladder is empty is lies within pelvis, shaped like and upside down pyramid
when it is full it is spherical and extends upward into abdominal cavity
(can hold 1L but is uncomfortable after 0.5L)
thickness of bladder wall changes as it expands
69
what are the 6 levels of organisation ?
1. organisms
2. organ system
3. organ
4. tissue
5. cell
6. chemical
70
what is the most abundant and most widely distributed of the tissues ?
connective tissue
71
what makes up part of every organ in the body?
connective tissue
72
what the connective tissue cells separated by?
cells separated from each other by extracellular matrix
73
what are the three main classes of connective tissue?
1. connective tissue proper
2. supporting connective tissue
3. fluid connective tissue
*several subclasses!
74
what are some connective tissue functions ?
connection (tendons/ligament)
support (bones/cartilage)
enclosing/protection (capsules/bones)
separation (sheaths)
cushioning/insulation (adipose tissue)
storage (adipose tissue)
transportation (blood)
75
tendon vs ligament
tendon= bone to muscle
ligament= bone to bone
76
what can generate connective tissue?
can only generate connective tissue from mesoderm (mesochymal stem cells)
common germ layer origin (embryonic mesoderm)
77
what is connective tissue composed of?
cells and ECM
(ecm= extracellular matrix)
78
what is ECM?
extracellular matrix
A large network of proteins and other molecules that surround, support, and give structure to cells and tissues in the body.
ground substance + extracellular protein fibres
*matrix properties allows connective tissues to bear weight and withstand tension and trauma
79
what do resident cells in connective tissue do?
each major class of connective tissue had resident cells which create, maintain or breakdown the ECM.
80
blasts vs cytes vc clasts
(each major class of connective tissue has resident cells which create, maintain or breakdown the ECM)
blasts create the ECM
cytes maintain the ECM
clasts break down the ECM
[Think clasts for cleaners and blasts for builders.]
81
osteoblasts
create bone
82
osteocytes
maintain bone
83
osteoclasts
break down bone
84
chondroblasts
create cartilage
85
chondrocytes
maintain cartilage
86
chondroclasts
break down cartilage
87
in addition to resident cells what other cell types does connective tissue house?
adipose cells (adipocyte)
macrophages (phagocyte)
lymphocyte
mast cells (mastocyte)
white blood cells (leukocytes)
undifferentiated mesenchymal stem cells
*all connective tissue contains some adipose, lots of immune cells reside in connective tissue and undifferentiated mesenchymal stem cells are there to help connective tissue regenerate
88
why are undifferentiated mesenchymal stem cells present in connective tissue?
there to help connective tissue regenerate
89
what does ECM properties allow for connective tissue?
matrix properties allows connective tissues to bear weight and withstand tension and trauma
90
comment on organ regeneration in terms of ECM and de-cellularisation
can de-cellularise a heart so that only the ECM scaffold remains.
very useful in artificial tissue and organ regeneration.
recellularising an ECM scaffold with a patients own cells eliminates adverse immune responses.
better than a donor heart.
91
what is ground substance in terms of ECM?
Ground substance is an amorphous gel-like substance in the extracellular space of animals that contains all components of the extracellular matrix (ECM)
fluid that fills the space between cells.
- gel-like, contains water and two main groups of soluble proteins:
1. cell adhesion proteins (connective tissue glue)
e.g. fribronectin, osteonectin, chondronectin (nectin=adhesion protein)
2. proteoglycans (macromolecule with the protein core to which glycosaminoglycans GAGs are attached)
this arrangement confers high viscosity and low compressibility (good for joints). the higher the GAG content, the more viscous the fluid.
important GAGs: hyaluronic acid, chondroitin sulfate, heparna sulfate, dermatan sulfate, keratan sulface
*hyaluronic acid is one of the most common proteoglycans in connective tissue
*the more GAGs the more viscose the substance is
92
how do GAGs affect the viscosity of a substance?
the more GAGs the more viscose the substance is
(glycosaminoglycans)
93
what two things comprise ground substance?
1. cell adhesion proteins (connective tissue glue)
e.g. fribronectin, osteonectin, chondronectin (nectin=adhesion protein)
2. proteoglycans (macromolecule with the protein core to which glycosaminoglycans GAGs are attached)
*gel-like, contains water and two main groups of soluble proteins
94
what are the important GAGs?
(glycisaminoglycans)
hyaluronic acid
chondroitin sulfate
heparan sulfate
keratan sulfate
dermatan sulfate
95
ECM three main fibres
fibres of connective tissue provide support
1. collagen
2. elastic
3. reticular
96
collagen fibres
most abundant (6% body weight)
created by fibroblasts
3x chains of amino acids wind around each other forming rope-like molecule (requires vitamin c)
in the ECM, triple helix modified into tropocollagen molecules which assemble into fibrils which are bundled into thick collagen fibres.
25 types of collagen.
type I most abundant (tendons, ligaments etc)
type II found in cartilage
type III mainly reticular fibres
97
what cells create collagen fibres?
fibroblasts
98
what vitamin is required to form collagen molecule?
vitamin C
3x chains of amino acids wind around each other forming rope-like collagen molecule
99
how many types of collagen are there?
25
type I= most abundant (tendons, ligaments etc)
type II= found in cartilage
type III= mainly reticular fibres
100
what comprises a collagen fibre?
amino acids -> tropocollagen -> fibrils -> fibres
101
elastic fibres
long, thin and contain elastin
secreted by fibroblasts
form branching networks in ECM
found in areas where greater elasticity needed (e.g. lungs, blood vessel walls)
102
what cells secrete elastic fibres?
fibroblasts
103
reticular fibres
short, fine fibres (0.5-2 micrometer diameter)
type III collagen fibres.
branch extensively forming networks. fill spaces between tissues and organs (e.g. basement membrane of epithelial tissue and around capillaries)
allow more 'give' than collagen fibres. abundant in liver, spleen and lymph nodes.
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give and overview of connective tissue components
functions of connective tissue (e.g. connection, support, protection, storage etc...)
general components of connective tissue:
cells
- resident cells (blasts. cytes and clasts)
- other cells (e.g. adipose, mast, macrophages, WBC and adult stem cells)
ECM
ground substance
- tissue fluid (water)
- cell adhesion proteins (e.g. fibronectin, osteonectin)
- proteoglycans (protein + GAG)
protein fibres
- collagen
- elastic
- reticular
105
what are the three main connective tissue classifications?
1. connective tissue proper
loose (areolar, reticular, adipose)
dense (regular collagenous, regular elastic, irregular collagenous, irregular elastic)
2. supporting connective tissue
cartilage (hyaline, fibrocartilage, elastic)
bone (spongy, compact)
3. fluid connective tissue
blood (red cells, white cells, platelets)
haemopoietic (red marrow, yellow marrow)
106
what connective tissue is classified under connective tissue proper?
loose: areolar, reticular, adipose
dense: regular/irregular collagenous, regular/irregular elastic
107
what connective tissue is classified under supporting connective tissue?
cartilage: hyaline, fibrocartilage, elastic
bone: spongy, compact
108
what connective tissue is classified under fluid connective tissue?
blood: red cells, white cells, platelets
haemopoietic: red marrow, yellow marrow
109
loose vs dense connective tissue
(connective tissue proper)
loose: fewer fibres more ground substance
e.g. areolar, adipose, reticular
dense: more fibres, less ground substance
e.g. regular collagenous, regular elastic, irregular collagenous, irregular elastic
*example of regular collagenous connective tissue is ligament/tendon
110
what is an example of a connective tissue disorder?
scurvy (defective collagen fibres)
vitamin C- ascorbic acid- deficiency results in unstable collagen molecule
*need vit c to form collagen fibres. in a vit c deficiency damaged collagen fibres cannot be replaced so collagenous tissues are affected. blood vessels in eyes burst, ligaments which hold teeth to gums are affected etc.
111
what is marfans syndrome ?
defective elastic fibres.
abnormal production of fibrillin-1 results in inefficient/weak elastic fibres and overgrowth of tissues.
allows tissues in body to grow too much. overgrowth of tissue leads to long limbs. eye lens is held by elastic fibres so it can dislocate.
most serious consequence of this syndrome is the dilation of large arteries. shorter lifespan because arteries eventually wear out.
*genetic disorder
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pulmonary emphysema
defective elastic fibres.
destruction of elastic tissue caused by increase in elastase activity.
air pollution and tobacco smoke stimulate excess release of elastase.
*elastase destroys connective tissue. bronchioles can collapse so process of getting oxygen into blood becomes less efficient.
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fibrosis
scar tissue formation
formation of excess fibrous connective tissue in an organ or tissue.
scarring is confluent fibrosis that obliterates the architecture of the underlying organ or tissue.
scars cause the tissues to harden reducing flow of fluids through affected tissues.
well known type- pulmonary fibrosis 'scarring of the lung'
*excess fibrous connective tissue. fibrosis is excess scar tissue formation. reduces overall surface area for gas exchange.
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bone marrow
fluid connective tissue.
soft spongy material in central cavity of larger bones and small spaces of spongy bone.
produces all 3 type of blood cell:
red, white, platelets, lymphocytes (support immune system)
red bone marrow: skull, vertebrae, ribs, sternum, heads of long bones.
yellow bone marrow: no longer produces blood
*when you're a child there's a lot of red bone marrow which is capable of producing red blood cells. this disperses into the end of the bone as you grow and the rest becomes yellow.
115
what are some examples of bone marrow diseases/blood cancers?
leukaemia: high numbers of immature/abnormal WBC's. symptoms- anaemia, reduced clotting, excess bruising, tiredness, increased infections.
lymphoma: abnormal lymphocytes
myeloma: abnormal plasma cells
treatment: radiotherapy, chemotherapy, bone marrow transplant
116
what cells are abnormal in lymphoma?
lymphocytes
117
what cells are abnormal in myeloma?
plasma cells
118
what cells are abnormal in leukaemia?
white blood cells. (leukocytes)
high numbers of immature/abnormal WBC's.
symptoms- anaemia, reduced clotting, excess bruising, tiredness, increased infections
119
what are the two parts of the nervous system?
1. central nervous system (CNS)
brain + spinal cord
2. peripheral nervous system (PNS)
cranial nerves + spinal nerves
120
what comprises nervous tissue?
neurones (nerve cells):
functional unit of nervous system. send signals around the body.
glial cells (support cells):
protect, provide nutrients and immune functions to the neurones.
*maintain chemical environment and give structural support and protection to the neurones
121
what are some properties of neurones?
1. irritability
2. receptors
3. conductivity
4. longevity
5. high metabolic rate- require continuous supplies of oxygen and glucose
*irritability means that they can respond to a signal via an electrical impulse. receptors allow signals to be received. signal is conducted. cells last a long time- pretty much for life. require lots of energy to carry out their functions.
122
comment on the fact that a nerve cell typically lasts a lifetime
nerve cells are highly specialised and once a connection is made it is difficult to replace the cell. (unlike epithelial tissue which is easy to replace when damaged)
123
what are the parts of a neuron?
dendrites -short branches from cell body
cell body/soma (contains nucleus)
axon - longer extension
axon terminal - at end of axon
124
what is found in the cell body of a neuron?
(soma)
central nucleus
usual organelles (the nucleus, nucleolus, endoplasmic reticulum, Golgi apparatus, mitochondria, ribosomes, lysosomes, endosomes, and peroxisomes.)
nissl bodies (clusters of free ribosomes and rER)
cytoskeleton (neurofibrils, microtubules and neurofilaments)
no centrioles
125
what organelles do neurones not have?
centrioles
Centrioles are paired barrel-shaped organelles located in the cytoplasm of animal cells near the nuclear envelope. Centrioles play a role in organizing microtubules that serve as the cell's skeletal system. They help determine the locations of the nucleus and other organelles within the cell.
126
what does the cytoskeleton in a neuron do?
keeps the shape and transports substances along axon (neurofilaments)
127
what are nissl bodies?
clusters of free ribosomes and rER
128
what does the presence of Nissl bodies tell us about the physiology of neuronal cell bodies?
made up of ribosomes and RER (rough endoplasmic reticulum) so is active in protein synthesis.
129
what does the absence of centrioles tell us about the physiology of neuronal cells?
centrioles are important for mitosis therefore they are amitotic. they cannot divide and make more cells. (very specialised)
*there are some exceptions to this particularly in the olfactory epithelium (related to sense of smell) and hippocampus
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neuronal dendrites
highly branched like trees.
location of synapses.
cytoplasm contain nissl bodies, mitochondria and other organelles.
*dendrites are the receivers. the branches gives them a large surface area.
nissl bodies= discrete clumps of rough endoplasmic reticulum and free ribosomes in nerve cells.- They are responsible for protein synthesis and play a crucial role in the functioning of the neuron.
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neuronal axon
thin, cylindrical projection of variable length.
only one per neurone.
specialised to conduct action potentials.
contains mitochondria and cytoskeletal proteins.
can be branched- axon collaterals and terminal branches.
*length depends on where they are in the body and on their function. axons can branch so it may look like theres more than one. axon collaterals are the main ones and terminal ones are smaller. cytoplasm in axon is specialised and contains mitochondria (high energy demand) and cytoskeleton structures to help the stability and direction. signal goes in one direction down a neuron.
axon= distributor
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axon collaterals and terminal branches
An axon typically develops side branches called axon collaterals, so that one neuron can send information to several others. These collaterals, just like the roots of a tree, split into smaller extensions called terminal branches. Each of these has a synaptic terminal on the tip.
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neuroglia
smaller than neurons but more numerous.
do not propagate action potentials.
able to divide and multiply.
in disease multiply to fill spaces previously occupied by neurones.
*glial cells are different as they do not propagate action potentials whereas neurones do. (one paper in which there is some evidence that they can but general consensus is that they can't).
if there is damage to neurones the glial cells will replicate and fill in the gaps. similar to scar tissue. the function of the cells is different so this can lead to reduction in normal function.
also known as glial cells or glia, are non-neuronal cells in the nervous system that support and protect neurons, maintaining homeostasis, forming myelin, and playing roles in development and repair
134
what 4 neuroglial cells are associated with the CNS?
1. astrocytes
2. microglia
3. ependymal cells
4. oligodendrocytes
135
what 2 neuroglial cells are associated with the PNS?
1. satellite cells
2. schwann cells
136
astrocytes
(CNS)
named because of their star-shape
- maintain chemical environment
- structural support
- guide growth and connections of new neurones
- blood-brain barrier
- forms scar tissue after brain injury
- provide nutrients to neurones
- take up excess neurotransmitters
(more functions than just this list)
*blood brain barrier is a protective mechanism. the blood can carry toxins and pathogens so a barrier is created between the neurones and the substances of blood. astrocytes create a physical barrier to stop toxic substances from crossing the blood brain barrier and only allowing nutrients to pass.
137
what cells in the CNS form the blood brain barrier?
astrocytes
blood brain barrier is a protective mechanism. the blood can carry toxins and pathogens so a barrier is created between the neurones and the substances of blood. astrocytes create a physical barrier to stop toxic substances from crossing the blood brain barrier and only allowing nutrients to pass.
138
what cells of the CNS take up excess neurotransmitters?
astrocytes
139
microglia functions
(CNS)
named because of their small size.
- protects the CNS by phagocytosis of invading microbes
- clear away debris of dead cells
*like immune cells of CNS
140
what cells act like the immune cells of the CNS?
microglia
named because of their small size.
- protects the CNS by phagocytosis of invading microbes
- clear away debris of dead cells
*like immune cells of CNS
141
ependymal cells function
(CNS)
- line the ventricles of the brain and central canal of the spinal cord
- form cerebrospinal fluid (CSF) and assist in its circulation
*CSF flows down central canal of spine and around brain. important that it is refreshed, monitored and circulated. needs to get rid of waste and be rich in nutrients.
- cilia encourage movement of CSF
- monitor composition of CSF
- selectively permeable; allows exchange of fluid and substances across lining
- barrier function
142
what cells associated with the CNS form cerebrospinal fluid and assist in its circulation?
ependymal cells
143
what other basic tissue type (other than nervous tissue) could ependymal cells be classified as?
specialised type of epithelial cells (glial cell)
144
what is cerebrospinal fluid and what does it do?
substance derived from blood that contains nutrients such as oxygen, ions and glucose to nourish the brain while protecting it from toxins. may also protect the rest of the body from escaped neurotransmitters.
145
what specialisation of ependymal cells of the CNS encourages the movement of cerebrospinal fluid?
cilia.
146
oligodendrocytes of CNS
names because of their dendrite-like processes
provide
- structural support (scaffolding)
- forms myelin sheath for some CNS cells
- foot process wraps around cell to be myelinated
*not limited to one axon segment or axon
147
what cell creates myelin sheath for some CNS cells?
oligodendrocytes
foot process wraps around cell to be myelinated.
*myelin sheath ensures actions potential can be propagated
148
myelin sheath
Myelin is an insulating layer, or sheath that forms around nerves, including those in the brain and spinal cord. It is made up of protein and fatty substances. This myelin sheath allows electrical impulses to transmit quickly and efficiently along the nerve cells. If myelin is damaged, these impulses slow down.
149
are oligodendrocytes of the CNS limited to one axon segment or axon?
no.
not limited to one axon segment or axon.
150
are schwann cells of the PNS associated with one axonal segment?
yes.
only associated with one axonal segment.
151
schwann cells
(PNS)
- only associated with one axonal segment
- wrap 'spiral' around axons of neurones
- collectively called the myelin sheath
- makes up white matter
- all other neural tissue is grey matter
*the cell themselves form the myelin sheath. the myelinated part looks white.
- acts like insulation on a wire
- spaces between are called Nodes of Ranvier
- intact sheath is critical to proper nerve impulses
- involved in repair and regeneration
- damaged in some conditions
152
what cells make up white matter?
myelinated axons
[oligodendrocytes in your brain and spinal cord (your central nervous system [CNS]) and by Schwann cells in your peripheral nervous system]
153
what are the gaps in the myelin sheath called?
Nodes of Ranvier
154
satellite cells of PNS
- flattened cells arranges around the cell bodies of neurones
- regulate chemical environment
- involved in repair
155
what are the 6 neuroglial cells and in what part of the nervous system are they found?
1. astrocytes (CNS)
2. microglia (CNS)
3. ependymal cells (CNS)
4. oligodendrocytes (CNS)
5. satellite cells (PNS)
6. schwann cells (PNS)
156
what two cells surround neurons in the PNS?
satellite cells and schwann cells (which form myelin)
157
tumours and the nervous system
- in the brain malignant and benign tumours can be equally serious
- most are gliomas
- symptoms depend on location, size and growth rate of tumour
- damage cannot be replace easily and excess growth can add pressure due to the skull which can have devasting effects
*gliomas= tumour that forms when glial cells grow out of control
158
what is a glioma?
glioma is a tumor that forms when glial cells grow out of control. Normally, these cells support nerves and help your central nervous system work. Gliomas usually grow in the brain, but can also form in the spinal cord. Gliomas are malignant (cancerous), but some can be very slow growing.
159
why are most brain tumours gliomas rather than neuronal cell tumours?
glial cells can divide and regenerate whereas neurones don't do this.
glial cells have much greater capacity for dividing.
160
give examples of nervous system disorders which cause demyelination
Loss or destruction of myelin sheaths. Can lead to paralysis.
e.g. multiple sclerosis
- progressive destruction of myelin sheath in CNS
- autoimmune
- can affect vision, speech, balance, and motor co-ordination
e.g. guillain barre syndrome
- immune response where macrophages strip myelin from axons in PNS
- most patients recover completely or partially
161
what cells are affected in guillain barre syndrome?
- immune response where macrophages strip myelin from axons in PNS
- most patients recover completely or partially
162
what percentage of body weight is made up by muscle tissue?
40-50%
(heavy tissue)
163
what are the functions of muscle?
movement
posture and joint stability
protein supply
regulate organ volume
propel fluids/food
heat generation
*movement of body as well as movement of substances within body. protein supply extreme circumstances so in a way a storage for protein. shivering is muscles working to generate heat. exercising also generates heat.
164
what are some properties of muscle tissue?
1. tightly packed and well-vascularised
2. excitability (ability to receive and respond to stimuli)
3. close relationship with surrounding connective tissue
4. contractility
5. extensibility (stretch without damage)
6. elasticity
*blood vessels take nutrients such as oxygen to tissue and removes waste. receive info such as from a nerve or a hormone and can respond to it. has a close relationship with CT as when muscle tissue contracts the surrounding CT attaches muscle to bone so everything moves. contractility is the ability to generate force (making muscle tissue distinct from other tissues). extensibility relates to elasticity as it goes back to original size.
165
what makes muscle tissue different from other tissue?
contractility (ability to generate force)
*muscles in neck and back are holding upward even if we're not moving but the muscles are still contracting
166
histology
Histology, also known as microscopic anatomy or microanatomy, is the branch of biology that studies the microscopic anatomy of biological tissues
167
what are the 3 type of muscle?
1. cardiac
2. smooth
3. skeletal
*differ in location, function, histology and control
168
cardiac muscle
located in heart.
large 10-20 micrometer fiber diameter
small 50-100 micrometer length
branched cyndrical shape (relates to function- cardiac muscle must contract in coordination)
functional syncytium- heart functions as one unit.
one centrally located nucleus in the cells. intercalated discs. gaps allow them to share electrical signals/info for the next cells to contract.
striated.
169
what term can be used to describe the muscle tissues of the heart?
functional syncytium
A functional syncytium consists of a group of cells that function as a single unit while still maintaining their individual cellular role.
170
intercalated discs
Intercalated discs are complex structures that connect adjacent cardiac muscle cells. The three types of cell junction recognised as making up an intercalated disc are desmosomes, fascia adherens junctions, and gap junctions. Fascia adherens are anchoring sites for actin, and connect to the closest sarcomere.
171
striated muscle
Striated muscles are highly organized tissues that convert chemical energy to physical work. The primary function of striated muscles is to generate force and contract to support respiration, locomotion, and posture (skeletal muscle) and to pump blood throughout the body (cardiac muscle).
172
smooth muscle
Smooth muscle fibres are located in walls of hollow visceral organs (such as the liver, pancreas, and intestines).
Most diverse group of muscles.
Small fibre diameter (3-8 micrometres) and medium fibre length (30-200 micrometres).
The shape of smooth muscle is fusiform, which is round in the center and tapering at each end. Nucleus is what gives the cell the bulge.
Smooth muscle can tense and relax but has greater elastic properties than striated muscle. This quality is important in organ systems like the urinary bladder, where the preservation of contractile tone is a necessity.
Non-striated
173
viscera
Viscera refers to the soft organs of the body. The soft interior organs of the body, such as the heart and lungs, and those in the abdomen, such as the liver, pancreas, and intestines, are known as visceral organs
174
what shape does smooth muscle have?
The shape of smooth muscle is fusiform, which is round in the centre and tapering at each end.
*Smooth muscle can tense and relax but has greater elastic properties than striated muscle. This quality is important in organ systems like the urinary bladder, where the preservation of contractile tone is a necessity.
175
skeletal muscle
mainly attached to bones
diameter is very large (10-100 micrometres) and length is also very large (100-3000 micrometres). most diverse in terms of size.
Long cylindrical shape. More force is generated by activating more muscle. Many peripherally located nuclei.
Striated.
176
what is NMJ?
neuromuscular junction
177
which muscle type is voluntary control?
Skeletal muscle: Skeletal muscles are voluntary muscles, meaning you control how and when they move and work. Nerves in your somatic nervous system send signals to make them function.
*some reflex control
178
what connective tissue surrounds muscle?
fascia.
- forms compartments separating muscles or muscle groups (skeletal muscle has several layers of connective tissue)
179
what are the functions of the fascia?
connects muscle to surrounding tissue and allows it to pull on it.
separates individual muscles or groups.
attaches and stabilises muscles.
maintains tension and prevents overextension.
180
epimysium, perimysium and endomysium
'my'= muscle
The outermost connective tissue sheath surrounding the entire muscle is known as epimysium. The connective tissue sheath covering each fasciculus is known as perimysium, and the innermost sheath surrounding individual muscle fibre is known as endomysium.
*skeletal muscle
181
what are individual skeletal muscle cell called?
fibre
182
where are nuclei located in fibres?
fibres (skeletal muscle cells) have many nuclei in the periphery of the cell below the sacrolemma
*The sarcolemma is the fine, delicate, extensible membrane surrounding each muscle fibre.
183
sacrolemma
The sarcolemma is the fine, delicate, extensible membrane surrounding each muscle fiber.
184
how to muscle fibres develop?
by fusion of myoblasts
185
what are muscle fibres abundant in?
mitochondria
- provides energy
186
sarcoplasmic reticulum (SR)
The Sarcoplasmic Reticulum or endoplasmic reticulum (more specialised as it stores calcium) is a network of tubules and sacs in skeletal muscle fibres that plays an important role in muscle contraction and relaxation by releasing and storing calcium ions.
*'sarco' refers to muscles
187
sarcoplasm
cytoplasm of muscle cell
188
what is the advantage to having lots of nuclei in the cell (fibre)?
skeletal muscle cells are often very long so it means that transcription- thus translation and protein production- can happen at various points in the cell.
189
what is skeletal muscle sarcoplasm filled with?
myofibrils
- cylindrical structures that carry out contractions
- these are where the striations can be seen
myofibrils
= rod-like, contractile organelles within muscle cells, composed of repeating units called sarcomeres, and responsible for muscle contraction through the interaction of thick (myosin) and thin (actin) filaments
190
what are myofibrils composed of?
of functional units called sacromeres.
1-2 micrometres diameter.
light bands= thin filaments
dark bands= thick filaments
this gives striations.
*skeletal muscle
191
what is built in the heart for autorhythmicity?
built in pacemaker for autorhythmicity
192
autorhythmicity
Cardiac automaticity also known as autorhythmicity, is the property of the specialized conductive muscle cells of the heart to generate spontaneous cardiac action potentials.
*built in pacemaker for autorhythmicity
193
what controls the speed and strength of heart contractions?
involuntary contraction and relaxation of cardiac muscle.
speed and strength of contractions can be controlled by hormones and neurotransmitters.
194
what muscle forms the majority of the heart?
cardiac muscle.
*striated
195
what regulates and controls smooth muscle?
regulated by ANS (autonomic nervous system) and endocrine system.
controlled by hormones and neurotransmitters.
non-striates. contains actin and myosin. action is involuntary. some smooth muscle has autorhythmicity e.g. GI tract
196
give example of smooth muscle with autorhythmicity
GI tract
*The mechanism underlying smooth muscle autorhythmicity seems different from that encountered in cardiac tissue, and evidence exists for metabolic regulation of the frequency of slow wave type action potentials.
197
diseases of muscle
myopathy: abnormal condition or disease of muscle tissue
dystrophy: muscle destroying disease-> progressive degeneration of muscles fibres (e.g. duchennes muscular dystrophy)
neuromuscular disorders: condition affecting any part of the motor unit (motor neurone, NMK or muscle fibre)
198
example of muscular dystrophy disease
duchenne's muscular dystrophy
*muscle destroying disease-> progressive degeneration of muscle fibres
199
metabolic myopathies
defects in any stage of muscle ATP metabolism can lead to a myopathy.
onset normally childhood/teenage years
- e.g. glycogen storage diseases
- mitochondrial myopathies
symptoms include:
- fatigue
- muscle weakness
- cramps and pains
^Metabolic myopathies are myopathies that result from defects in biochemical metabolism that primarily affect muscle. Myopathy is a general term referring to any disease that affects the muscles that control voluntary movement in the body.
200
inflammatory myopathies
chronic muscle inflammation and weakness
often idiopathic
autoimmune
progressive muscle weakness:
proximal->distal
201
idiopathic
relating to or denoting any disease or condition which arises spontaneously or for which the cause is unknown.
202
proximal vs distal
They describe the position of a structure with reference to its origin – proximal means closer to its origin, distal means further away.
203
cholesterol role in cell membrane
Cholesterol stabilizes the cell membrane by forming interactions with the phospholipid tails and heads. This makes their structure more rigid and helps provide stability.
Cholesterol: This is found within the phospholipid bilayer and helps to maintain the fluidity of the membrane. It helps to prevent the membrane from becoming too rigid or too fluid, allowing it to function optimally.
204
function of basolateral membrane
basolateral membrane is to take up metabolic waste products into the epithelial cell for disposal into the lumen where it is transported out of the body as urine.
205
corpus callosum
The corpus callosum is a bundle of nerve fibres that allow your brain's left and right hemispheres to communicate. It plays a role in how you think, remember and coordinate your movements.
206
dense irregular vs regular connective tissue
regular
Collagen fibers are arranged in a parallel, orderly manner, providing high tensile strength in one direction.
irregular
Collagen fibers are arranged in a random, interwoven pattern, providing strength in multiple directions.
