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Development and Physiology - Coggle Diagram
Development and Physiology
Development
multicellularity
prokaryotes (bacteria and archaea): all unicellular but can form co-operative communities
can reproduce via binary fission
eukaryotes: protists, plants, animals, fungi - all mulitcellular except most protists are unicellular or show some partial multicellularity e.g. slime mold
Dictyostelium
Dictyostelium- a cellular slime mold as a model
for the evolution of multicellularity --> feeding stage consists of single cells that function individually but when starved, cells can migrate and co-operate to form a motile aggregate w/specialised fruiting body to release spores <-- mulitcellular existance formed by aggregation of single cells
multicellular organisms can reproduce asexually (offspring are clones) - types:
spore formation
(in Dictyostelium),
budding
(in hydra) - new individuals arise from outgrowths of existing ones,
fragmentation
- body can regrow from a fragment (e.g. flat worms),
parthenogenesis
(virgin birth, e.g. hammerhead shark) - arise from unfertilised eggs,
vegetative propagation
- propagation w/out seeds - cuttings
sexual reproduction
requires: production of two types of germ cells (egg and sperm gametes) via meiosis, form two types of indiviuals, mechanism to fuse egg and sperm
whys sex?: provides genetic variation between individuals - variation allows a population to adapt and is the driving force of evolution - neccessary for healthy adaptive population
fertilisation = union of gametes - fertilised egg =zygote, zygote produces somatic cells by mitosis // offspring share 50% of their genes with each parent - siblings share an average of 50% genes
gametogenesis: spermatogenesis: formation of sperm in male // oogenesis: formation of egg in female
oogenesis differs from spermatogenesis in 3 major ways
cytokenesis is unequal in meiosis - mots cytoplasm goes to daughter cell to form ovum - the polar bodies degenerate
sperm develop form spermatogonia, which continue to be generated by mitosis throughout life
oogenesis marked by long resting periods whereas spermatogenesis is continuous
fertilisation: bringing sperm and egg gametes together to form diploid zygote -> also activates the egg, triggering begining of embryonic development - model organisms : sea urchin
how polyspermy (entry of multiple sperm into egg) prevented:
acrosomal reaction
: acrosome at tip of sperm releases hydrolytic enzymes that digest material surrounding egg - recognition between sperm and egg triggers plasma membrane fusion and depolarisation of egg cell membrane - sets up a FAST BLOCK, as a polyspermy barrier
cortical reaction
: fusion of egg and sperm initiates calcium ion release from endoplasmic reticulum in a wave across egg - after sperm binds to egg, vesicles beneath egg plasma membrane release their contents and form a fertilisation envelope which hardens the plasma membrane // Ca release also causes egg activation, increasing rate of cellular respiration and protein synthesis - entry of sperm causes egg activation but doesn't supply any material needed, can be achieved acrtificially by increased calcium -> parthenogenesis can be induced
fertilisation in mammals: differences:
fertilisation is internal
egg cloaked in follicle cells released w/egg
sperm undergoes capacitation in unterus - can penetrate egg
egg has tough extracellular matrix = zone pellucida -presents receptors for sperm
binding of receptor leads to acrosomal reaction
no known fast block to polyspermy but similiar cortical reaction for slow block
whole sperm taken into egg egg - base used to form centrioles for spindle
nucleid don't fuse together - both nuclear envelopes disperse - chromosomes align on spindle in cytoplasm
first cell division slower
general development principles: fertilised egg must give rise to many cell types - all cell types produced progressively as embryo develops in right place at right time --> 1. cell division, 2. cell differentiation, 3. morphogenesis ( how the organism takes on 3d shape)
model systems for development
invertebrate: - nematode worm, Caenorhabditis elegans
easily grown on petri dish, 1mm long, simple transparent body w/only a few cell types, zygote matures quick, genome is sequenced
vertebrate : The frog, Xenopus laevis
large eggs, accessible embryos, short development time (4 days), robust embryos, can tolerate manipulation
plants: arabidopsis thaliana
v small: 1000s of it in small lab space, short generation time, have genome sequenced, small genome, deveopled for gene maipulation - can be induced to take up foreign DNA
choice for model organisms: biological considerations (access to embryo and availability), practical considerations (cost of maintaining in lab, space to maintain), historical considerations (is the bio understood)
approaches: Observation and descriptive embryology, experimental embryology, cell lineage analysis, developmental genetics
Differences between plant and animal development: 1. movement of cell are involved in transforming animal embryo but not plant 2. morphogenesis and growth isn't limited to embyronic and juvenile growth in plants - have apical meristems for continual growth and formation of new organ- animals don't have an equivlent except for differentiation of cells
unique genome of zygote is replicated during mitotic division and present in all somatic cells of body
cell differentiation is achieved via differential gene expression
stem cells - cells that have not full differentiated - can be a source of cells for growth, repair and regeneration
how to express a gene (turn it on); Transcription - when a gene is 'turned on' its DNA sequence is used as a template for the synthesis of a complimentary RNA // translation - production of protein from RNA - sequence of AA that make up protein depend on genetic code carried by the RNA
gene also includes regulatory sequnces (non-coding DNA segments) - determine which cells express that gene and when they turn it on - regulate transcription by binding TFs
two types:
promoters: located at transcription site, needed for transcriptional machinery to assemble and begin to transcribe, promoter sequnces are similiar in diff eukaryotic genes
enhancers : gene specific control regions that determine when and where a gene will be turned on - can be situated close to the coding seuqnce (proximal) or at large distinaces (distal)
initiation of gene expression controlled by presence/absence of regulatory proteins that turn gene on/off working through enhancer regulatory sequnces
how enhancers influence gene expression: cell specific transcription factors (actiavtors) bind to specific control elements (enhancers) - influencing the efficiency of binding the General Transcription Factors to the initiation site (promoter) - this interaction determines if a gene is transcribed or not - if factors needed to turn on a gene are not present the gene remains off
diff cells have diff sets of control elements driving them e.g. in a liver cell, the activators are present to turn on the albumin gene
TFs = proteins that interact w/DNA to regulate transcription
cellular differntiation in the embryo - usually is a result of transcriptional regulation : turning genes on/off - differentiation happens progressively as embryo develops - changes might be taking place inside cell at molecular level logn before it visibly differentiates - when differentiated cells appear they already produce the proteins that allow them to carry out their specialised roles in the organism
following the invisible changes at the molecular level: embryonic precursor cells have potential to become cartilage, fat cells or multinucleate muscle - determination irreversibly commits a cell to becoming a particular cell type - determination precedes differentiation - cells determined to be muscle = myoblasts - can be recogniseed by the genes they express
how do muscle precursor cells (myoblasts) turn on the right genes to form functioning muscle fibres: hypothesis - myoblasts are distinguished by the activity of certain muscle specific regulatory molecules - these actiavte the expression of the correct proteins leading to muscle differntiation --> experiment to test: 1. mRNA isolated from cultured byoblasts 2. DNA copies of the mRNA were cloned 3. cloned genes were forced into embryonic precursor cells 4. the premise: the cells that form muscle must have received a gene for a muscle regulatory molecule (special determinant)
one gene identfiied: MyoD - encodes a cell specific TF that commits cells to becoming skeletal muscle - some target genes for MyoD (protein) encode additional muscle-specific TFs - the MyoD protein is capable of starting a cascade that changes non-muscle cells into muscle cells
master regulatory genes = developmental regulators
product of a master regulatory gene under the right circumstances willl turn the rigt genes on or off (downstream genes) to initiate a program of cellular diffrentiation - many of the downstream genes may also be regulatory genes controlling expression of more target genes = how cascade event along a differentiation pathway may be controlled
how were developmental genes identified: studying developmental mutants - spontaneous mutatiosn i.e. chnage in eye colour (rare) / large scale mutant screens - animals exposed to mutagens (radiation) to increase frequency of genetic damage -> drosophila well suited - mutant screens designed to identify genes involved in determining body plan - categorised mutations into: 1. Maternal Effect genes 2. Segmentation genes 3. Homeotic genes
Maternal Effect Genes
establish poles (egg polarity genes)/major axes of Drosophila body plan -> genes aren't active in the embryo itself - gene products are supplied to the egg/early embryo by the mother - maternal genes encode mRNA and proteins that are placed in egg while it is maturing in ovary - not uniformly distributed so they act as cytoplasmic determinants
example of maternal effect gene = bicoid gene - in bicoid absence (bicoid mutant) - posterior structures (tails) form at both ends - bicoid gene needed for forming the anterior structurees (head)
bicoid mRNA is concentarted at the extreme netrior end of the egg cell - there is a gradient of proteins in the early embryo, high at the anterior - bicoid is necessary to organise body plan of fly along AP axis -> high bicoid = anterior / low bicoid = posterior structures
segmentation genes
divides embryo into segments along AP axis - among one of the first genes to be turned on
bicoid and other maternal effect genes are TFs that regulate activity of some of the embryo's own genes - a cascade of gene actiavtion sets up the segmental pattern
three groups of segmentation genes for finer details: Gap Genes = subdivisions along AP axis, Pair Rule Genes = define pairs of segments, Segment Polarity Genes = define the segment and establish pattern in each segment
homeotic genes
control the anatomical identity of segments - mutant homeotic genes - structures in wrong places
homeotic genes encode TFs - they control the expression of specific target genes - responsible for generation of anatomical structures // maternal effect gene bicoid also encodes a tF // segmentation genes encode TFs but not all - some genes involved in cell signalling = cells influence each other by sending molecular signals tahts are converted to responses within the cell - molecular explanation for induction
overall, genes that direct drosphila development were found to control: 1. TFs that regulate expression of target genes 2. signaling molecules responsible for cell communication 3. other components of signalling pathways e.g. receptors
similiar gene sequence (homebox) found in several homeotic genes - homeobox genes were highly conserved through evolution - distant relatives in yeast - homeotic genes fall into Hox genes category of homeobox genes - hox genes are a subset of all homeobox genes involved in positional identity - Hox genes found in all animals w/an organised body plan
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describing development : fertilisation -> cleavage -> gastrulation -> organogenesis-> neurulation
Fertilisation
leads to egg activation - Ca2+ eflux (release) - increasing rate of cellular respiration and protein synthesis - starts the first cleavage cell division
cleavage
: rapid cell division of fertilised egg - converts zygote to a ball/disc of cells - cell cycle involves S phase (DNA synthesis) and M phase (mitosis) but skips G phases (no growth) - FASTER - is marked by little/no protein synthesis and no growth of embryo - no change in size, just an increase in cell number = first 5-7 divisions produce a hollow ball of cells = blastula, surrounding a fluid filled cavity = blastocoel
cleavage in frog: egg has polarity - movement of molecules triggered by fertilisation - appearance of gray crescent - firs two cleavages are vertical - cleavage 3 is horizontal - yolk content displaces plane of division toward animal pole -> smaller cells and blastocoel in animal half / vegetal pole is the other
cleavage in the chick: the entire egg cell is yolk - the 'white' (protein rich solution) = nutrition - all cytoplasm is in a tiny disk at animal pole - cleavage planes can't penetrate the dense yolk so only animal pole is cleaved - incomplete cleavage = meroblastic cleavage (complete cleavage = holoblastic) - cleavage produces a cap of cells sitting on top of yolk = blastoderm - cavity forms (blastocoel) divides two layers of cells - hypoblast and epiblast - embryo emerges from epiblast
blastoderm in chick = blastula in frog
cleavage in diff species produces a ball or disk of cells
gastrulation = extensive cell movement where cells of blastula/blastoderm become organised into three layers - 3 layered embryo has a primitive gut = gastrula // 3 layers : ectoderm, mesdoderm, endoderm
occurs in all eumatazoa (animals with a body plan), sponge is not a eumatazoa
tracked via cell fate mapping with injected dye
gastrulation in frog: line of cells changes shape and invaginates - occurs at site (dorsal lip) of blastopore - future mesoderm and endoderm cells at site of dorsal lip involute into interior of embryo - the original blastocoel acvity has collapsed by the movement - new cavity called archenteron - form future gut - cells on surface that from ectoderm move completely to cover embryo
celluar processes in making a new organismss as a result of cell movement, the embryo elongates as cells meet and converge inside embryo -> convergent extension - can lead to alongation - directed by cytoskelton
derivitives of germ layers
ectoderm (outisde) - epidermis of skin, nervous and sensory systems, pituaitary gland, adrenal medulla, jaws and teeth
mesoderm (middle layer) - skeletal and muscular systems, ciruclatory and lymphatic system, notochord
endoderm (inside) - epithelial lining of digestive tract and organs, epithelial lining of respiratoy, excretory and reproductive, liver, pancreas
features of gastrulation: elaborate cell movement, differentiation of cells into 3 types, formation of 3 layered gastrula, positioning of cell layers in gastrula to allow communication between cells
gastrulation in the chick - different as the early embryo is a flat disk of cells w/masses of yolk underneath - entire embryo form from one layer (epiblast) - cells from epiblast move underneath through line at midline of disk (primitive streak) - some involuting cells form endoderm and some mesoderm - primitive streak marks future anterior-posterior axis of embryo - is equiv to the blastophore in frog (site through which cells involute)
organogenesis
= development of organs
many changes brought about by induction = influence of one group of cells on a neighboruing group of cells, changing the way in which the responding cells develop - how tissue interactions are important
Hans Spemann and Hilde Mangold : 1. transplanted dorsal lip of blastophore in an amphibian embryo to ventral side on anther amphibian embryo 2. monitored subsequent development of recipient -> demonstrated the inductive action of the organiser
an almost complete second axis could be formed in the ventral side of the developing embryo -> organiser cells set in motion a chain of events leading to production of new body plan = primary organiser
cells from the secondary axis aren't all derived from the donor but are from the recipient - means organiser cells fro the donor could change the fate of the recipient cells
other organs form as neurulation proceeds
coelum = fluid filled cavity formed by splitting the mesoderm- surrounded by mesoderm on all sides - many organs push into this space
somites = mesoderm cells that form blocks on either side of neural tube - are transitory structures that dissociate to form diff cell types i.e. muscle blocks and vertebrae
somites show that vertebrates are partially segmented animals -> neural crest cells develop along neural tube of vertebrates and migrate in body to form various parts of embryo eg teeth, skull
organogenesis in chick - proceeds similiar to frog but appears different due to flat embryo - to achieve the same 'tube within a tube' edges of blastodisk (flat chick embryo)fold ventrally to enclose gut - still joined in middle of body to yolk in the yolk sac
special adaptations in animals that reproduce on dry land (amniotes) - lay an egg and nourishing and protecting an embryo on dry land: 1. a protective egg shell on externally laid eggs (reptiles) 2. by uterus - internal development in mother's body in mammels --> in both cases, the have an extra-embryonic membrane - amnion! - formed from the germ layers that extend outside the future body of the chick embryo
4 membranes
amnion: surrounds embryo, forms fluid filled sac that bathes embryo - made from ectoderm and mesoderm
chorion - outer membrane, exchange gases between embryo and surrounding air - diffuse oxyegn and CO2 across egg shell
yolk sac : encloses yolk - blood vessels develop in yolk sac to bring nutrients to embryo - first site of blood production
allantois: waste disposal sac - metabolic wastes - also performs gas exchange
amniote evolution: v. few predators so extrenal egg archietcture could evolve - multiplied and diversified - much harder to protect egg now // endothermy (maintains own body temp)
viviparity = giving birth to live young e.g. marsupials and placental mammels
advantages: protection, incubation, mother can still hunt and forage, had a new structure - placenta
placenta = exchange between mother and foetus , made from extra-embryonic membranes and part of mother's uterine wall
how mammels develop - specialisations of mammels : small non-yolky egg fertilised in oviduct and cleaves as it moves into uterus - cleavage is holoblastic and no apparent polarisation of egg and morula - further cleavage produces hollow blastocyst, thickened on one side - Inner Cell Mass - gives rise to entire embryo and most extra-embryonic membranes / trophoblast - involved in implantation -gives chorion and placenta
mammalian blastocyst = frog blastula = chick blastoderm // the diff names reflect the special characteristics of each animla grouo - blastocyst is made up of two distinctive cell types in prep for implantation
implantation - embryo attaches to uterine wall - trophoblast secretes enzymes that break down molecules of the endometrium
trophoblast thickens and sens finger like projections into blood rich maternal tissue - ICM forms a flat disk of cells = epiblast - similiar to chick -> gastrulation starts - epiblast cells move underneath through primitive streak emerging as endoderm and mesoderm
extra-embryonic membranes: amnion = encloses embryo in fluid filled sack and ruptured before birth, chorion = contributes to placenta in humans (outer membrane), yolk sac = no yolk but retains name - structure is homologous to that in birds - site of blood production, allantois = incorporated into umbilical cord
neurulation
= specialised type of organogenesis - sets aside cells and forms rudiment of nervous system - first organogenesis event - neurulation is initiated by induction
requires formation of rod-like group of mesoderm cells along dorsal midline of future embryo as cells are involuting during gastrulation - these special mesoderm cells form the notochord and have special traits i.e. have ability to induce - signals sent from notochord to ectoderm above induce the ectoderm to thicken and form neural plate
outer edges of neural plate fold upward, forming neural folds - two sides of neural folds fuse to enclose the neural tube - as neural tube fuses, the adjacent surface ectoderm also fuses to enclose the neural tube - becomes brain and spinal cord
at end of gastrulation and neurulation, embryo has elongated w/ a head end (anterior) and tail end (posterior) and has an internalised neural tube running along dorsal midline -> in the headregion, the neural tube is englarged to form brain chambers
morphogenesis = how body plans are built
cells receive info about where they are in the embryo and how such positional info can influence differntiation
postional info defined by co-ords along 3 axes
positional address - flash card analogy - a pattern could emerge in the embryo by cells receiving a positional address via a set of molecular signals unique to that position
two ways in which cells can receive info: 1. localisation of cytoplasmic determinants
induction
localisation of cytoplasmic determinants
rna and protein molecules are a source of info in cytoplasm (include TFs) - uneven distribution - following mitotic division cell nuclei are exposed to diff info and therefore express diff genes
induction
one group of cells influences the devlopment of a neighbouring group of cells - organiser cells from donor could chnage the afte of the recipient cells and set in motion a chain of events leading to the production of a new body plan
induction achieved at the molecular level via cell signalling - gene can be turned on/off in response to signals a cell receives = paracrine signalling (neighbouring cells)
signal transduction = mechanism that relays the signal received at the cell surface to the nucleus - cascade of events can be set in motion - ultimate effect of signalling at the cell surface is a change in gene expression in the nucleus
cell signalling: only the cells that possess a particular receptor on their cell surfaces can respond in a particular way - therefore some cells won't respond at all or two diff cells can respond in diff ways to the same signal
ability to respond to a signal = competence -> is a two part communication system
cell signalling is the way in which cells become diff from each other - important role players at molecular level: signalling molecules, their receptors, molecules that effect the changes inside the responding cell (TFs)
in the case of gastrulation: cells involute through blastopore and are exposed to strong signals from organiser and acquire info about their relative position in embryo - organiser fives rise to cells of the notochord - induces the neural tube
morphogenesis in plants : genetic control of flowering: position and emergence order reflets its afte - several identity organs (plant homeotic genes) that regulate the development of floral pattern - flower formation involves a phase chnage from vegetative growth to reproductive growth - mutation in one of the genes can cause abnormal floral development
plant organ identity/homeotic genes - 3 classes of floral organ identity genes: A,B,C - ABC hypothesis identifies how floral organ identity genes direct the formation of the four types of floral organs - they generate positional information - ABC genes are homeotic genes that confer organ identity - are analogous to Drosophila homeotic genes - show they confer positional info using a code
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cells in v early drosphila embryos are distinguished by maternally produced determinants - cytoplasmic determinants e.g. bicoid - positional info present in unfertilised egg // in amphibians positional info generated by a combo of cytoplasmic determinants in egg and entry point of sperm
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morphogens and gradients
morphogen = substance involved in pattern formation where cells have a graded response depending on the level of the signal they are exposed to -> how patterns can be established over a whole organism - range of outcomes depending on concentration experienced (french flag model)
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cells can respond to morphogens by: dividing, changing expression of genes, changing shape, cell migration
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programmed cell death sculpts the embryo of unwanted cells e.g. in interdigital zone
Physiology
form and function
hierarchy of organisation
space between cells filled w/ interstitial fluid - links exchange surfaces to body cells - specialisation of cells/tissues/organs allows complexity
stem cells = undifferentiated cells - can give rise to special cells // embryonuc stem cells - can give rise to many cell types / adult stem cells are tissue specific / induced pluripotent stem cells developed from skin cells
tissue
epithelial - shape may be cuboidal, columnar or squamous / arrangement may be simple, stratified or pseudostratified
connective: binds and supports other tissues - contains sparsely packed cells scattered throughout an extracellular matrix - matrix consists of fibres in a liquid, jellylike or solid foundation - contains cells including fibroblasts which secret the protein of extracellular fibers
3 types of connective tissue fibre - all made of protein : collagenous fibers provide strength and flexibility, reticular fibers join connective tissue to adjacent tissues, elastic fibers stretch and snap back to their original length
loose connective tissue binds epithelia to underlying tissues and holds organs in place
muscle - consists of filaments of the proteins actin and myosin which together enable muscles to contract - 3 types: skeletal (voluntary movement), smooth (involuntary), cardiac (heart contraction)
nervous: transmission of information - contains: neurons (transmit nerve impulses) and glial cells (support cells)
internal environment: fluid compartments of human body: total bdoy water, intracellular fluid, extracellular fluid, plasma, interstitial fluid
maintaining homeostasis - variables are physiologically regulated
external environment: temp, oxygen, water, light
internal environment: temperature, blood pressure, composition of body fluids
fluctuations above or below serve as a stimulus that triggers a response - response returns the variable to the set point
normal ranges can change e.g. a circadian region governs physiological chnages that occur every 24hrs - we can acclimatize to environmental change
mechanisms of homeostasis
negative feedback - helps return a variable to a normal range e.g temp regulation
positive feedback amplifies a stimulus e.g. childbirth
feedforward - anticipatory responses to expected change
biosynthesis: after staying alive needs have been met, remaining food used in biosynthesis eg. body growth and repair
homeostasis regulated by NS and endocrine system
NS: network of specialized cells - neurons - transmit signals along pathways - fast, local, rapid response
at synaptic signalling, neurons form specialized junctions w/target cells = synapses - at synapses, neurotransmitters diffuse short distance and bind to receptors on target cells - neurons are supported by glia
sensory receptors transduce stimulus energy and transmit signals to the central NS for perception - when a stimulus is received and processed by NS, a motor response may be generated
sensory pathways have 4 functions: sensory reception, transduction, transmission, perception
types of receptors:
mechanoreceptors - sense physical deformation caused by forms of mechanical energy: consist of ion channels linked to structures that end outside the cell e.g. cilia // sensitivity of skin depends on size of receptive fields
chemoreceptors: some transmit info on solute conc and others respond to diff kinds of molecules // gustation (taste)
electromagnetic receptors: e.g. detect light, electricity, magnetism // photoreceptors : light reaches rods and cones - optic nerves meet at optic chiasm near centre of base of cerebral cortex - sensation of the left visual field of both eyes transmitted to right side of brain and vice versa
thermoreceptors: for heat and cold
nociceptos detect stimuli that reflect harmful conditions - respond to excess heat, pressure or inflammed tissues
endocrine system : chemical signalling by hormones - slow, long lasting
hormones secreted into extracellular fluids by endocrine cells reach their targets via blood
3 classes: polypeptides, steroids, amines
endocrine cells grouped in ductless organs called endocrine glands e.g thyroid // exocrine gland have ducts that carry secreted substances onto body
NS and endocrine regulation linked via hypothalamus - hypothalamus co-ords endocrine signalling - it receives info from nerves and initiates signals
base of hypothalamus - pituitary gland - composed of posterior and anterior pituitary
neuroscience
mind/body dualism: mind is non-physical, brain may control movement, mind and consciousness exist in a non-physical world, body is determined by the physical world, mind is not
behaviour = action carried out by muscles under control of the NS
innate behaviour : present in all members of a species, develops independently of environment, often present at birth, long lasting, slightly modifiable
general pattern generation (CPGs) are biological neural circuits that produce rthymic outputs in the absence of rythmic output - have at least two interacting components to allow rhythmic activity e.g. breathing, chewing, swallowing
fixed action pattern = sequence of unlearned acts directly linked to a simple stimulus - unchangeable and carried out to completion - triggered by an external cue known as a sign stimulus
learned behaviour: modification of behaviour w/experience, can be short or long-lasting, highly modifiable, diff for each person
imprinting =establishment of a long lasting behaviour response to a particular object/individual - can only take place during the sensitive period e.g. the first two days the parents must bond with offspring or it will reject offspring
spatial maps: spatial learning is the establishment of a memory that reflects the environments spatial structure - tinbergen showed how digger wasps use landmarks to find nest entrances // cognitive map= internal representation of spatial relationships between objects in an animal's surroundings
associate learning = animals associate one feature of their environment w/another
operant conditioning = type of associative learning in which an animal learns to associate one of its behaviours w/ a reward or punishment a.k.a. trial-and-error learning
classical conditioning = type of associative learning in which an arbitray stimulus is associated w/a reward or punishment, a.k.a. Pavlovian
social learning and culture - monkeys imitate sweet potato washing once they observe it
camillo golgi: developed golgistaining method - based on innate motivational drives - promoted 'reticular' theory for continuity of brain organisation
santiago ramón y cajal : discovered nerve growth cone - developed 'neuron' theory for brain anatomy
neuronal structure: most of a neurons organelles are in the cellbody, most neurons have dendrites (highly branched extensions that receive signals from other neurons), the axon is a much longer extensiion that transmits signals to other cells at synapses, the cone-shaped basis of an axon is the axon hillock,
most neurons are insulated by glial cells
Tinbergen's Four Question: 1. causation (stimulus and mechanism) 2. survival value ( adaptive function) 3. ontogeny (how it is built in development) 4. phylogeny (evolutionary history)
cognition: problem solving
cognition = process of knowing that involves awareness, reasoning, recollection, judgement // some bird species particularly corvids demonstrate complex problem solving
communication : bees communicate angle and distance to food sources - distnace as a number of waggles and angle from sun as direction
bees can be trained to generalise the learned rule for 'same' vs 'different' stimulus in a diff behavioral task
information processing - circuits: NS processes info in 3 stages: sensory input, integration, motor output
neuronal diversity: CNS where integration takes place, PNS which carries info into and out of CNS, neurons of PNS, when bundled together form nerves
neurotransmission theory etc etc - LECTURE 2
rate at which action potentials are produced in a neuron is proportional to input signal strength - speed of an action potential increases w/axons diameter - in vertebrates, acons are insulated by a myelin sheath which causes an action potantial's speed to increase - myelin sheaths are made by glia- oligodendrocytes in CNS and Schwanna cells in PNS
voltage gated sodium channels are restricted to nodes of ranvier = gaps in the myelin sheath
action potentials in myelinated axons jump between nodes of ranvier in a process called saltatory conduction
synaptic conductance (two categories of postsynaptic potentials)
Excitatory Postsynatic Potentials (EPSPs) = depolarisations that bring the membrane potential toward threshold
Inhibitory postsynaptic potentials (IPSPs) = hyperpolarisations that move the membrane potantial farther from the threshold
throughout summation, an IPSP can counter the effect of an EPSP -> summed effect of EPSPs and IPSPs determines whether an axon hillock will reach threshold and genrate an action potential
perception
sensation leads to perception - travels from PNS to CNS - processing can happen before, during or after transmission of action potential to CNS - integration often begins as soon as info is received
action potentials travel from motoneurons - actiavte muscles through neuromuscular junction (NMH)
Brain distinguishes stimuli from diff receptors based on path by which action potentials arrive
receptor cells for taste in mammels are modified epithelial cells organized into taste buds located in several areas of mouth and tongue - most taste buds are associated w/projections called papillae - any regions w/taste buds can detect any of the five types of taste
taste sensations of sweet, unami and bitter require specific G protein coupled receptors (GPCRs) - receptor for sour belongs to TRP family and is similiar to capsicin - taste receptor for salt is a sodium channel
receptor swap experiments in mice: PBDG is bitter to humans but mice are indifferent as they have no receptor to sense it - genetically engineered mice to express the human PBDG recptor
the simplest animals, with NSs (cnidarians) have interconnected neurons arranged in nerve nets - more complex animals have nerves in which the axons of multiple nerves are bundled together - bilaterally symmetrical animals exhibit cephalization = clustering of sensory organs at front end of body
human brain structure:
grey matter - consists of neuron cell bodies, dendrites and myelinated axons
white matter = bundles of myelinated axons
vertebrate brain
forebrain - regulation of sleep, learning
midbrain - coordinates routing of sensory input
hindbrain controls involuntary activities and coords motor activities
human brain
cerebrum controls skeletal muscle contraction and is the centre for learning, emotion, memory and perception
outer layer of cerebrum = cerebral cortex - vital for voluntary movement, learning
thick band of axons = corpus callosum = enables right and left cerebral cortices to communicate
cerebellum coords movement and balance
hypothalamus constitutes a control centre and includes bodys thermostat and body cloclk
brainstem = midbrain, pons, medulla oblongata
midbrain receives and integrates sensory info
pons and meduall transfer info between PNS and midbrain and forebrain
medulla = control of automatic functions eg breathing
Broca's area = language production // Wernicke's area = language comprehension
generation and experience of emotions involve amygdala, hippocampus, parts of thalamus = grouped as the limbic system - amygdala is the emotional centre
hippocampus and amnesia and sensory input
platicity - neuronal platicity describes ability of NS to be modified after birth // synaptic plasticity means a stregthening or weakening of synaptic junctions
synaptic plasticity -> long term potentiation (LPS) - lasting increase in strength of synaptic transmission - involves a presynaptic neuron that releases the neurotransmitter glutamate - LTP involves two types of glutamate on the receiving cell (NMDA recptors are central)- receptors on the post synaptic membrane chnage in response to stimulus - agents that disrupt LTP seem to disrupt memory
brain development
midbrain and hindbrain form brainstem - joins w/spinal cord at base of brain / rest of hindbrain gives rise to cerebellum
forebrin divides into the diencephelon which forms endocrine tissues in the brain and the telencephalon which becomes cerebrum
nervous system
spinal cord conveys info to and from brain and makes general patterns of locomotion - spinal cord also produces reflexes independently of brain
peripheral NS
transmits info to and from CNS and regulates movement and internal enviornment - in PNS, afferent neurons transmit info to CNS and efferent neurons transmit info away from CNS
motor system : carries signals to skeltal muscles
autonomic NS : regulates breathing, HR, urination
enteric NS : exerts control over digestive tract, pancreas, gall bladder