124 Hormones & Development Flashcards
why are signalling systems needed
1) neurotransmission
2) coordination of developmental processes
3) homeostasis
what are the three types of signalling between cells
1) free diffusion between cells
2) cytoplasmic connections
3) direct cell-to-cell contact
what are the 3 types of signalling by free diffusion
- autocrine
- paracrine
- endocrine
describe autocrine signalling
signalling and reception by the same cell, the cell secretes signals that modify its own behaviour
where is autocrine signalling used
cell division
describe paracrine cell signalling
cell signalling to neighbouring cells, the effects are local and short-lived
where is paracrine cell signalling used
embryonic development
describe endocrine signalling
signalling between distant cells via hormones
what is the fastest method of cell to cell communication
signalling via cytoplasmic connections
briefly describe signalling via cytoplasmic connections
transfer of a signal from one cell to another via pores in the membrane, occurs in cardiac muscle cells allowing simultaneous contractions
describe signalling by cell-cell contact
involves specific interactions between surface molecules on one cell and receptors on another
what are local regulators
molecules that act on cells in the vicinity (paracrine & autocrine)
what are hormones
signalling molecules that act at a distance (endocrine signalling)
name 4 types of local regulators
- Growth factors
- Gases
- Prostaglandins
- neurotransmitters
what are growth factors
molecules that stimulate cell proliferation, may have more than one target cell
give an example of a gas, how is this a local regulator?
nitric oxide
= induces vasodilation in the cardiovascular system
acts as a paracrine signal molecule
short half-life
what are prostaglandins
modified fatty acids that have multiple functions e.g.
- excitability of uterine wall during childbirth
- indication of fever and inflammation in the immune response
how are neurotransmitters local regulators
some are inhibitory, some are excitatory, occurs in CNS and PNS
how are hormones secreted and transported
secreted by endocrine glands- transported in the bloodstream
what controls hormone production
the neuroendocrine system (hypothalamus)
what are the two main classes of hormones
Peptides & proteins
Steroids
define homeostasis
maintenance of a relatively stable internal environment in the face of stress from the external and internal environment.
the internal environment is in a state of dynamic equilibrium
describe the stages of signal transduction
1) reception: signal molecule binds to receptor on cell surface
2) transduction: signal is converted into a response- e.g. by protein phosphorylation
3) the cellular response
