Biology A1 - cells, tissues and organs Flashcards
what is cell differentiation
the development of cells with specialised structure and function from unspecialised precursor cells
what is amoeba
a type of unicellular organism
lives in fresh water and moves by ameboid movement
inhibit top layer of decaying organic material on the bottom of ponds
what are the different categories of tissues
epithelium
connective
muscle
nerve
what is tissue
group of cells with a common structure and function
what is epithelial tissue
a tissue that covers the outside of the body or lines an organ or cavity within the body
what are the types of epithelial tissue and where are they found
1) simple squamous epithelium - lines alveoli in lungs
2) cuboidal epithelium - kidney tubules
3) simple columnar epithelium - lines digestive tract
4) stratified squamous epithelium - skin
5) pseudostratified columnar epithelium - lines trachea
what two sides do polar epithelia have
basal side = closely interacting with other cells
apical side = side exposed to the lumen
what are occluding junctions in epithelial tissue
multiprotein complexes that seal neighbouring cells together to prevent the leakage of water and solutes
eg. tight junctions, anchoring junctions
what are communicating junctions in epithelial tissue
gap junctions - allow molecules to pass through from one cell to another
how are cells in epithelial tissue arranged
tightly packed together
what is epithelial tissue important for
secretion and absorption
what are goblet cells
found within epithelial tissue
specialized epithelial cells that secrete mucus and play a key role in maintaining the body’s mucosal barrier
how are cells arranged in connective tissue
sparsely distributed within an extracellular matrix that may be solid, jelly like or even liquid
connective tissue often contains a web of protein fibres, what are the different types
collagen - strong, non elastic
elastic - made of elastin
reticular - thin and highly branched, reticular fibres serve to join connective tissue to adjacent tissues
what are the different types of connective tissue
loose connective tissue
fibrous connective tissue
bone
adipose tissue
cartilage
blood
what are the different types of muscle tissue
smooth muscle
cardiac muscle
skeletal muscle
what is an intercalated disk
a specialized structure in the heart that connects cardiac muscle cells together, allowing for electrical and mechanical communication between cells
what is a sarcomere
the basic unit of muscle fibre
made of protein filaments
repeated units that make up myofibrils that are bundles of fibres that make up muscle tissue
describe cardiac muscle
location: heart
structure: straited
control: involuntary
power: high
describe skeletal muscle
location: limbs
structure: straited
control: voluntary
power: high
describe smooth muscle
location: gut, blood vessels
structure: non- straited
control: involuntary
power: low
what does it mean if muscle tissue has a straited structure
a muscle that has a striped appearance
what two types of protein filaments make up sarcomeres (muscle tissue)
actin - thin filament
myosin - thick filament
describe the process of muscle contraction (sliding filament model)
results from interactions between actin and myosin filaments
1) The myosin heads, which are energized by ATP, bind to the exposed active sites on the actin filaments, forming cross-bridges
2) Myosin heads pull actin filaments toward the centre of the sarcomere, using energy from ATP.
3) As actin slides over myosin, without changing lengths, leading to muscle contraction
4) New ATP causes myosin to detach from actin, and the cycle repeats as long as calcium and ATP are available.
what does nerve tissue do
transmits electrical signals
interact using chemical signals
what are sensory and motor nerves
sensory = from sense organs, respond to stimuli
motor = nerves to muscle, activate contractions
what are the parts on a nerve cell
dendrites (stimulus)
cell body
axon (transmits signal to next cell)
what allows transition in long distance nerve cells to be fast
giant axons
myelination
what is myelin
extra membrane wrapped around axon as insulation
what produces myelin
produced by accessory cells - Schwann cells in motor neurons
how does myelin speed up transmission
by saltatory conduction at nodes of Ranvier (gaps in the myelin sheath)
myelinated nerves have a concentration of Na+ channels at nodes of Ranvier
conduct impulses rapidly because of potential changes at nodes
describe Na+ channels in non-myelinated nerve cells
action is slower and more chaotic
what is convergent evolution and what is an example of this
mechanism differs in the details but broad function is the same
eg. myelin sheath
what is multiple sclerosis
degenerative disease that attacks the nervous system
causes white blood cells to attach myelin around nerve fibres in brain and spinal chord, disrupts transmission
what are the tow ways intercellular signalling occurs between nerve cells
action potential transferred to another cell across synapse. two ways:
- chemical
- electrical
how does an electrical synapse work
ions flow from presynaptic to postsynaptic neuron through gap junction channels in neuron membranes
fast transmission
how does a chemical synapse work
in presynaptic neuron vesicles fuse will membrane and release neurotransmitters into synaptic cleft
neurotransmitters move across and bend with postsynaptic neurotransmitter receptors on post synaptic membrane
can have inhibitory or excitatory effect
ions flow through post synaptic channels
slower transmission
how does communication occur between nerve and skeletal muscle cells
through neuromuscular junction (chemical synapse)
describe blood (connective tissue)
extracellular mix = liquid (plasma)
contains red blood cells, white blood cells, platelets in the plasma
what happens at a wound (blood, connective tissue)
1) endothelium of blood vessel is Brocken
2) platelet adhere to fibres and release substance that makes platelets sticky attracting more plantlets to the area
3) form a plug (immediate protection)
4) clotting factors from platelets and from plasma for enzymatic cascade converting fibrinogen to fibrin
5) fibrinogen becomes solid creating mesh of fibres to plug the wound
describe loose connective tissue
- contains all three protein fibre types: elastin, collagen, reticular
- cells called fibroblasts secrete the matrix and proteins
- contains macrophage cells, engulf pathogens and dead cells
function: attaches skin to tissues
forms mesenteries that hold internal organs in place
describe adipose tissue (connective tissue)
type of loose connective tissue
stores fat which acts as an energy store
hormones can regulate its levels
each cell contains a fat droplet
where is adipose tissue found (connective tissue)
surrounds tissues and organs
gives protection to blood vessels
what is blubber
form of adipose tissue some marine animals posses (thick layer)
it is vascularised tissue (requires oxygen and nutrients) used for: energy, buoyancy, insulation and protection
what type of fibres is fibrous connective tissue made from
collagen fibres - a glycoprotein (inelastic and rigid but strong)
what are two types of fibrous connective tissue
tendons = attach muscles to bones
ligaments = link joints
what are fibroblasts
synthesise extracellular matric and collagen - most common cells of connective tissue
describe cartilage (connective tissue)
- composed of collagen fibres in rubbery matrix of chondroitin sulphate ( a protein carbohydrate complex)
- secreted by cells called chondrocytes
- resists compression, acts as shock absorber
what causes osteoarthritis (connective tissue)
loss of chondroitin sulphate from cartilage causing bones grinding against each other
what is cauliflower ear
separation of cartilage from the perichondrium capsule, results in loss of blood flow to cartilage in ear which deadens ad becomes lumpy scar tissue
what animal uses cartilage as its skeleton
shark
lighter, more flexible, bore buoyant
more energy efficient and faster in the water
describe bone
a mineralised- matrix of collagen fibres impregnated by salts
secreted by cells called osteoblasts (become osteocytes in fully formed bone)
more rigid than cartilage but not brittle
what are the 3 parts of bone
compact bone - gives strength and found on outer surface of bones
spongy bone - more delicate, found in centre and at the end of bones
bone marrow - in the centre of bone, red bone marrow is where blood cells are made, contains mostly fat
what remodels bone throughout your life
osteoclasts (break down bone) and osteoblasts (build it back up)
why is there blood supply to bones
get nutrients in and waste out of bone
how do hormones affect bone health
males have greater bone density due to testosterone levels
higher oestrogen levels encourage osteoblast activity
when will you reach peak of bone mass
in 20s
what is important for bone health and development
healthy diet and exercise
what is skin
an organ
what are the three layers of skin
epidermis
dermis
hypodermis
describe the epidermis of skin
tough outer layer
protective and impermeable
waste materials can be excreted
sensory organ
important for thermoregulation
describe dermis of skin
middle layer
contains sweat glands, oil glands, hair root and hair follicle etc.
describe the hypodermis of skin
deepest layer
contains adipose tissue (thermo regulation) and blood vessels
what are organs
a part of the body that is made up of tissues that perform a specific function
eg. stomach, liver etc.
what are organ systems
made up of organs working together to perform a function
eg. digestive, respiratory, circulatory
