Topic 6 Chemical Signals

two organ systems used for regulation

nervous system (NS), endocrine system (ES)

nervous system (NS)

regulates overall activity and function, responds to sudden stimuli

endocrine system (ES)

not as associated with sudden stimuli, typically regulates slower processes, responses are slower

nervous system (features)

working cell: neuron

distance from target cells: very close

type of signal: nerve signal (electrical)

speed of signal: fast

duration of signal: very brief

specificity of signal: very specific

coordinated signals? highly coordinated

endocrine system (features)

working cell: endocrine cell

distance from target cells: very far

type of signal: hormones (chemicals)

speed of signal: slow

duration of signal: prolonged

specificity of signal: nonspecific

coordinated signals? relatively not coordinated

transducers

things that can take one form of energy or information and convert it into another form of energy or information

BOTH NS and ES ARE ACTING AS TRANSDUCERS!

nervous system (process)

1. receptor for stimulus

2. electrical signal

3. gap between control cell and target cell

NS: synaptic cleft

4. secretion of chemical signal

NS: neurotransmitter

ES: hormone

5. receptor for chemical signal

6. signal transduction (may use 2nd messengers) 

7. response by target cell

neurotransmitters

neural signaling

autocrines

autocrine signaling

paracrines

paracrine signaling

hormones and neurohormones

endocrine signaling

pheromones

pheromonal signaling

first messengers

• neurotransmitters, chemical signaling

• come out of regulatory cell

second messengers

• intracellular

• don’t work outside cells

signal transduction using ion channels

signal transduction using cAMP/PK (diagram)

signal amplification by adenylate cyclase

signal transduction using cAMP/PK

stimulatory G-protein (Gs)

enhances activity

inhibitory G-protein (Gi)

inhibits activity

signal transduction using IP3 and DAG

signal transduction: ca++ and calmodulin

signal transduction: nitric oxide (NO) (w/ or w/o cGMP)

signal transduction using inherent Tyr-K

signal transduction using JAK (Janus Kinase)

signal transduction using eicosanoids

prostaglandins & prostacyclins: vascular actions, (stimulates) inflammation

leukotrienes & HETEs: mediate allergic and inflammatory reactions

thromboxanes: blood clotting, other vascular actions

signal transduction by gene expression

a cell's external signal activates intracellular signaling pathways that modify transcription factors, ultimately changing the expression of specific genes to produce a cellular response. This begins with a ligand (signal) binding to a receptor, triggering a intracellular cascade of molecular events, often involving second messengers. This cascade leads to the activation or modification of transcription factors, which then move to the nucleus to initiate or suppress the transcription of specific genes, altering the cell's function or behavior