Homeostasis - Maintenance of relatively constant conditions in the internal environment
Significance of Homeostasis - Disruption can lead to disease; Body can adapt to mild stressors; Variables that need to remain constant: composition, temperature, volume
Positive Feedback Loops - Positive F...
BIOL2220 final exam Questions and
Answers
Homeostasis - Maintenance of relatively constant conditions in the internal
environment
Significance of Homeostasis - Disruption can lead to disease; Body can adapt to
mild stressors; Variables that need to remain constant: composition, temperature,
volume
Positive Feedback Loops - Positive Feedback: the response of system goes in the
same direction as the change
Negative Feedback Loops - Negative Feedback: [definition not provided]
Cellular Signalling - Specialised cells → tissues → organs; Communication via
transmitters allows functioning; Involves gap junctions and cell-to-cell interactions
Juxtacrine Signalling - Direct contact between cells; Gap junctions
Paracrine Signalling - Short distance, immediate cellular environment; Local
coordination (proliferation and differentiation)
Autocrine Signalling - Cell signals to self; Self-stimulation (immune system) or
self-identity (development)
Endocrine Signalling - To distant sites, via hormones in the bloodstream;
Development and physiology
,Processes in Cell Signalling - Paracrine: signal received from presynaptic neuron
on nearby postsynaptic neuron; Autocrine: signal sent + received by presynaptic
neuron
Receptors - Bind to initiate a physiological response - transmit through sequences
of molecular switches to signalling pathways
Gap Junctions - Formed when 2 connexons adjacently come together to form a
narrow pore between cells - allowing small molecules and ions to move from cell
to cell providing metabolic and electrical coupling
Hormones - Produced in specialised cells/organs, travel via blood
Endocrine Glands - Have specialised cells, produce hormones
Target Organs/Tissues - Must have specific receptors, circulating hormones will
contact, only some respond
, Steroid Hormones - Derived from lipid cholesterol
Peptide-Protein Hormones - Long amino chains or short linked chains
Amine Hormones - Modified amino
Hormone Actions - Synthesised and released (stored in vesicles/released as
synthesised); Transported in blood (protein (un)bound); Received at cell
(intra/extra-cellular); Elicit cell actions and responses
(rapid/slow/sustained/cyclical/pulsatile)
Signal Transduction - Classical Genomic Signalling: lipophilic - can diffuse across
membrane + interact with receptors inside cell; Non-Genomic Signalling:
extracellular receptors (GPCRs) have been identified - exact contributions not well
understood
Types of Receptors - G-protein coupled; Ion channel; Enzyme-linked; [can be
ligand-gated channels]
G-Proteins and Signal Transduction - No hormone = GDP is bound to α subunit of
G protein; Hormone attaches to receptor = regulatory components (β & γ) detach
from α and GDP bound to α is exchanged for GPT; Activated α alters function of
another membrane protein usually a channel/enzyme (adenylate cyclase,
phospholipase C)
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