Physiology notes
Local communication between cells
a. Gap junctions form direct cytoplasmic connections between
adjacent cells.
Single-unit smooth muscle cells are connected by gap junctions, and the cells
contract as a single unit.
b. Contact-dependent signals require interaction between
membrane molecules on 2 cells. A natural killer immune cell recognizes a
healthy cell of the body by binding to a ‘self’ marker on the cell’s surface.
c. Autocrine signals act on the same cell that secreted them.
Paracrine signals are secreted by one cell and diffuse to adjacent
cells.
Long distance communication between cells. Hormones in the endocrine
system are always travelling via the blood. Hormones effect cells with
receptors response. Hormones are secreted by endocrine glands or
cells into the blood. Only target cells with receptors for the hormone
respond to the signal.
Neurotransmitters and neurohormones in the nervous system.
Neurotransmitters are chemicals secreted by neurons that diffuse
across a small gap to the target cell. Neurohormones are chemicals
released by neurons into the blood for action at distant targets.
Speaking and listening
Ligands: first messengers
Bind to receptor proteins response
Intracellular processes
o Signal pathways: second messengers
2 messengers cellular response
nd
Behavioural and physiological response
Intracellular (in the cell) and membrane receptors (on the cell)
a. Intracellular signal receptors: lipophilic signal molecules diffuse
through the cell membrane. Binding to cytosolic or nuclear receptor
triggers.
b. Cell membrane receptors: extracellular signal response binds to a
cell membrane receptor binding triggers rapid cellular
response.
Intracellular receptors:
Lipid soluble ligands
Steroid hormones
o Corticosterone/cortisol
o Testosterone
o Oestradiol
o Thyroid hormones
Cell membrane receptors:
Water soluble ligands
Neurotransmitters
Lipophobic hormones
Local communication between cells
a. Gap junctions form direct cytoplasmic connections between
adjacent cells.
Single-unit smooth muscle cells are connected by gap junctions, and the cells
contract as a single unit.
b. Contact-dependent signals require interaction between
membrane molecules on 2 cells. A natural killer immune cell recognizes a
healthy cell of the body by binding to a ‘self’ marker on the cell’s surface.
c. Autocrine signals act on the same cell that secreted them.
Paracrine signals are secreted by one cell and diffuse to adjacent
cells.
Long distance communication between cells. Hormones in the endocrine
system are always travelling via the blood. Hormones effect cells with
receptors response. Hormones are secreted by endocrine glands or
cells into the blood. Only target cells with receptors for the hormone
respond to the signal.
Neurotransmitters and neurohormones in the nervous system.
Neurotransmitters are chemicals secreted by neurons that diffuse
across a small gap to the target cell. Neurohormones are chemicals
released by neurons into the blood for action at distant targets.
Speaking and listening
Ligands: first messengers
Bind to receptor proteins response
Intracellular processes
o Signal pathways: second messengers
2 messengers cellular response
nd
Behavioural and physiological response
Intracellular (in the cell) and membrane receptors (on the cell)
a. Intracellular signal receptors: lipophilic signal molecules diffuse
through the cell membrane. Binding to cytosolic or nuclear receptor
triggers.
b. Cell membrane receptors: extracellular signal response binds to a
cell membrane receptor binding triggers rapid cellular
response.
Intracellular receptors:
Lipid soluble ligands
Steroid hormones
o Corticosterone/cortisol
o Testosterone
o Oestradiol
o Thyroid hormones
Cell membrane receptors:
Water soluble ligands
Neurotransmitters
Lipophobic hormones
