HUBS1403 Lecture Notes - Lecture 18: Extracellular Fluid, Osmoreceptor, Proprioception
8 Jun 2018
School
Department
Course
Professor
Communication, Integration and Homeostasis
Cell-to-cell Communication
Occurs by 2 basic types of physiological signals:
• Electric signals
o Changes I a cell's membrane potential
• Chemical signals
o Secreted by cells into the extracellular fluid
Cells that receive signals are called target cells
Methods of cell to cell communication
1. Gap junctions: form direct cytoplasmic connection between adjacent cells
2. Contact dependent signals: require interaction between membrane molecules on 2 cells
3. Autocrine signals: act on the same cell that secreted them. Paracrine signals: are secreted by one cell and
diffuse to adjacent cells
4. Long distance communication: electric signals carried by nerve cells, chemical signals transported by blood
Signal Pathways
A cell cannot respond to a chemical signal if the cell lacks the appropriate receptor proteins for that signal
Receptor proteins
Can be located
a. Inside the cells
b. On the cell membrane
Signal Pathways
Binding of the signal to a receptor protein will initiate a response by
• Activation of the receptor
• Subsequent activation of one or more intracellular signal molecules, leading to
• Modification of existing proteins or synthesis of new proteins, resulting in:
• A response
Receptor types
- Peripheral: lie outside brain
o Chemoreceptor – pH, gases, chemicals
o Osmoreceptor: osmolarity
o Thermoreceptor: temperature
o Baroreceptor: pressure
o Proprioceptor: body position
o Other mechanoreceptors: pain, vibration, touch
- Central: in close to brain
o Eyes – vision
o Ears – hearing balance
o Nose – smell
o Tongue - taste
Modulation of Signal Pathways
Different cells can respond differently to the same signal
- Eg Adrenaline:
o β recptors on heart → increase HR
o α receptors on blood vessels → vasoconstriction
Control Pathways: Homeostasis
• 2 control systems involved:
o Nervous
o endocrine (often both)
