WEEK THREE - DNA/RNA, HISTOLOGY, ORGANISATION AND HISTOLOGY OF NERVOUS SYSTEM Flashcards
Structure of DNA and organisation in nucleus
polymer of nucleotides with
- phosphate group
- sugar - deoxyribose
- nitrogenous base
non-dividing state - compacted, around histone protein
dividing state = DNA copies into 2 parallel sister chromatids
base pairing = A-T, C-G
compare the structure and function of DNA vs RNA
RNA - polymer of nucleotides
phosphate group
sugar - ribose
nitrogenous base
RNA = smaller than DNA
only one nucleotide chain not double helix
DNA = CTAG
RNA = CUAG [Uracil replaces Thymine as nitrogenous base]
DNA function - codes for protein synthesis
RNA function - interprets DNA code
Define the genetic code and describe how DNA codes for protein structure
system that enables FOUR nucleotides to code for amino acid sequence of proteins
three nucleotides / amino acids
codon = mirror image sequence of nucleotides found in mRNA
64 possible codons [AUG=start = codes for methionine]
[3 stop codons]
Explain the process of transcription
copying instructions from DNA –> RNA
- RNA polymerase binds to DNA
- opens DNA helix and transcribes bases from 1 strand of DNA into pre mRNA
[DNA ‘C’ = mRNA ‘G’]
[DNA ‘A’ = mRNA ‘U’ - rewinds DNA helix
Explain the process of translation
- RNA reads amino acids assembled into protein molecules in mRNA
- tRNA takes amino acids to ribosomes
- converts nucleotides into sequence of amino acids = proteins
ribosome in cytosol or RER
- small subunit attaches to mRNA leader sequence
- larger subunit joins and pulls mRNA along whilst reading it [from AUG start codon]
- small subunit binds activated tRNA with corresponding anticodon
- large subunit enzyme forms peptide bonds = growth of polypeptide chains
- process repeats until stop codon reached
- polypeptide chain released and ribosome subunits separate
Describe how DNA is replicated
DNA helicase open short segment of helix [creates replication fork]
Primase enzyme binds to spot -annealing RNA primer
DNA polymerase III binds to RNA primer and begins generating complementary strand of DNA
List and describe the 4 main phases of the cell cycle
G1 Phase [first gap phase]
Accumulates materials needed to replicate DNA
S phase [synthesis phase]
DNA replication
G2 [second gap phase]
Replicates centrioles
Synthesises enzymes for division
Growth for preparation for mitosis
M phase [Mitotic]
Nuclear and cytoplasmic division
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
G0 phase [cells that have left the cycle]
List the phases of mitosis and summarise the events that occur in each phase [IPMATC]
One cell divides into TWO DAUGHTER CELLS with identical copies of DNA
Function - growth and replacement of worn out cells
Phases
Interphase
Chromosomes duplicate = two duplicate chromatins joined at centromere
Prophase
Chromosomes condense + nuclear envelope breaks down
Spindle fibres grow from centrioles
Centrioles migrate to opposite poles of cell
Metaphase
Membrane breaks apart
Spindle fibres attaches to chromosome and line up equator of cell
Anaphase
Spindle fiber shortens and centromere divides = becomes two separate chromatins
Two chromatids are pulled to polar ends of cell by spindle fibers and centromeres
Telophase
Chromosomes arrive at cell poles
Nuclear membrane forms around each set of chromosomes
Spindle fibers break down
Cytokinesis
Cell membrane breaks into two separate sets of chromatins
= TWO DAUGHTER CELLS
List and define the 4 primary tissue classes [ECNM] - e-cinema
Epithelial
Layers of closely spaced cells that cover organ surfaces, form glands
Function = protection, secretion, absorption
Connective
Usually moe matrix than volume
Function = often specilised to support, bind and protect organs
Nervous
Tissue contains excitable cells
Functions = rapid transport of coded info to other cells
Muscular
Elongated, excitable muscle cells
Function = contraction
Describe the structural properties that define epithelial tissue
Layers of loosely adhering cells with little extracellular matrix
One or more cells thick
Upper surface usually exposed to environment or internal space in body
Avascular [no room between cells for blood cells]
Relies on the diffusion of nutrients and gases from vessel-rich underlying CT layer
High rate of mitosis with cells closest to the CT layer [allows rapid repair]
List and exemplify 5 functions of epithelial tissue [PSAFS]
Protecting underlying structures
Eg outer layer of skin and epithelium of oral cavity protect underlying structures from abrasion
Secretion of substances
Eg mucous glands, sweat glands, enzyme-secreting portions of pancreas all composed of epithelial cells
Absorption
Absorption of nutrients across epithelium of small intestine
Filtration
Eg kidney epithelia is glomeruli filter out wastes from blood capillaries
Sensation
Epithelial structures with sensory nerve endings are found in the skin, nose, ears and eyes
List & define how epithelia are classified by layers & shape
LAYERS
Simple
Single layer of cells attached to basement membrane
Stratified
More than one layer
Only basal layer attached to basement membrane
Pseudostratified
Type of simple epithelium where epithelium appears to be stratified but is not
Some cells do not extend to free surface
SHAPE
Squamous
Cells are flat and scale-like
Cuboidal
Cube-shaped, as wide as tall
Columnar
Cells taller than they are wide
List the 8 types of epithelia, describe their structure and give examples where they can be found
Simple Squamous Epithelium
Single row of flat cells
Permits diffusion of substances//Secretes serous fluid
Alveoli, glomeruli, endothelium and serosa
Simple Cuboidal Epithelium
Single row cube shaped cells with microvilli
Absorption and secretion, mucus production
Liver, thyroid, mammary and salivary glands, bronchioles and kidney tubules
Simple Columnar Epithelium
Single row, tall narrow cells
Oval nuclei in basal half of cell
Absorption and secretion; mucus secretion
Lining and GI tract, uterus, kidney and uterine tubes
Pseudostratified Epithelium
Single row of cells some not reaching free surface
Nuclei give layer stratified look
Often with goblet cells and ciliated
Secretes and propels respiratory mucus
Typically found in trachea
Keratinised Stratified Squamous
Surface layer of dead cells
Multilayered epithelium covered with dead squamous cells packed with tough protein [keratin]
Retards water loss and barrier to organisms
Found in epidermal layer of skin where abrasion is high
Non-Keratinised Stratified Squamous
Multilayered surface epithelium forming moist, slippery layer
Without surface layer of dead cells
Resists abrasion
Tongue, oral mucosa, oesophagus, anal canal and vagina
Stratified Cuboidal Epithelium
Two or more cell layers; surface cells = square
Secretes sweat; produces sperm and hormones
Sweat gland ducts; ovarian follicles and seminiferous tubules
Transitional Epithelium
Multilayered epithelium surface cells that change from round to flat when stretched
Allows for filling of urinary tract
Lining Of urinary bladder and ureter
Exemplify how the structural differences between epithelia relate to their functional differences
Different tissue types are more suited to particular types of body - some need protection eg keratinized + non-keratinised stratified squamous, whilst others need diffusion of materials across membranes eg simple squamous.
eg Stratified epithelia are found where a barrier is needed and where there is abrasion present
Eg oral cavity and epidermis
Simple epithelium in these areas would just wear way
Describe the structural properties that define connective tissue
Most abundant and variable tissue type
Widely spaced cells - produces intracellular matrix
Multitude of different cell types
List and exemplify 5 functions of connective tissue (CT) [BSPST]
Binding organs
Tendons bind muscles to bone
Support
Bones of skeletal system provide rigid support for body
Physical protection
Vertebral column protects spinal cord
Fat cushions kidney organs
Storage
Bones provides storage for minerals - calcium
Transport
Blood transports gases, nutrients, hormones and waste through body
State the 5 main categories of CT & their different subtypes
Fibrous CT [two types]
Loose [two subtypes]
Areolar tissue
Reticular tissue
Dense CT [two subtypes]
Dense regular CT
Dense irregular CT
Adipose tissue
Cartilage [three types]
Hyaline cartilage
Elastic cartilage
Fibrocartilage
Bone [two types]
Spongy
Compact
Blood
List the distinguishing features for each CT type mentioned
Dense regular
Dense, packed parallel collagen fibres
Tendons/ligament hold bones together + attach muscles to bones
Dense irregular
Dense, randomly arranged
Withstands multidirectional stresses
Found in deeper layer of skin, around organs
Adipose
Empty looking, thin margins
Nucleus pressed against membrane
Hyaline Cartilage
Clear glassy matrix with collagen fibres not visible
ends of bones
Elastic Cartilage
Large chondrocytes with elastic fibres in matrix
external ear and nose
Fibrocartilage
Highlighted by visible parallel collagen fibres + chondrocytes
IV disc
Spongy bone
Spongy in appearance Honeycomb structure
Covered by compact bone
Compact bone
Solid in appearance
Found on periphery on bone [outer limits/ perimeter]
Blood
Fluid CT with variety of cells and cell fragments
Found in heart and blood vessels
Exemplify how CT structure reflects its function
- Bones needs to be tough and hard to serve protective function hence matrix is mineralised
- Cartilage consists of a flexible rubbery matrix that makes it well suited for shock absorption.
Name and define the major anatomical and functional subdivisions of the nervous system
anatomical subdivisions
-CNS [brain + spinal cord]
-PNS [all of nervous system apart from brain/spinal cord]
consists of nerves + ganglia
functional subdivisions
-sensory division [afferent]
receptors –> CNS
effectors = skeletal muscle
[VISCERAL and SOMATIC sensory subdivisions]
- motor division [efferent]
CNS –> effectors
[SOMATIC motor subdivision]
effectors = cardiac muscle, smooth muscle, glands
[VISCERAL motor subdivision]
effectors = cardiac muscle, smooth muscle, glands]
Name and describe the 3 universal properties of all neurons
- excitability [irritability]
ability to respond to stimuli by polarity changes [ action potential or changes to resting potential] - conductivity
produces travelling electrical signals - secretion
when electrical signal reaches end of nerve fibre, chemical neurotransmitter secreted
Name & describe the function of the 3 functional classes of neurons
- sensory neurons [afferent]
detect changes in body and external environment
info transmitted to brain or spinal cord - interneurons
between sensory and motor pathways
90% of neurons are interneurons
process store and retrieve info - motor neurons [efferent]
send signals to effectors eg muscles and glands
Name & identify the parts of a representative neuron
Name & describe the 4 structural classifications of neurons
- multipolar neuron
most common
many dendrites/ one axon - bipolar neuron
one dendrite/one axon
olfactory, retina, ear - unipolar neuron
sensory from skin and organs –> spinal cord - anaxonic neuron
many dendrites, NO axon
helps in visual processes
List the 6 different types of glial cells & state their role
Oligodendrocytes
Form myelin sheaths in CNS
Each wraps around many nerve fibers
Ependymal cells
Line cavities and produce CSF
Microglia
Formed from monocytes
Respond to pathogens/injury
Astrocytes
Most ABUNDANT glial cell - form framework of CNS
Contribute to blood brain barrier [BBB] + regulate composition of brain tissue fluid
Sclerosis - damaged neurons replace by hardened mass of astrocytes
Satellite cells
Surround cell bodies of neurons of PNS ganglia and similar role to astrocytes
Shwann cells [myelinate fibres of PNS]
Describe the myelin sheath & explain its importance
Insulating layer around nerve fibre
[20% protein and 80% lipid -looks white]
Increases speed of signal conduction = decrease reaction times
Decrease capacitance [stops cations and anions sticking on membrane] = aids in increasing conduction speed
