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Chemical Signals

What are the two types of physiological signals?
electrical signals-changes in membrane potential, chemical signals-secreted into ECF, most communication
Communication can occur _____cells, _______ cells and from one _____ to another.
between, within, organ
What type of communication is used between cells?
neurotransmitters and hormones
What type of communication is used from one organ to another?
What type of communication is used with cells?
second messenger systems, enzyme cascades
How do all forms of communication operate?
via receptors in cell membranes
What are ligands?
specific chemical messengers synthesised by specialised cells to serve a designated purpose,
How do ligands work?
act on target cells and bind with target cell receptors to exert effects
What do chemical messengers include?
amines, amino acids, steroids, poypeptides (some instances lipids, purine nucleotides and pyramiding nucleotides)
What are the different types of chemical messengers?
autocrines, paracrines, neurotransmitters, hormones, neurohormones
What is paracrine communication?
chemical acts on another cell which is located close to the cell from which it is released
What is endocrine communication?
chemical acts on another cell which is locate far away from the cell which it is released, utilised bloodstream as a transport system
What is autocrine communication?
chemical acts on same cell from which it is released, often a mechanism for limiting release of the chemical
What are characteristics of paracrines?
derived from individual cells, effect on neighbouring cells in immediate environment of their site of secretion, don't enter blood as inactivated by enzymes
What is an example of a paracrine?
Histamine released by mast cell (connective tissue) dilates blood vessels in the vicinity
What is an example of a cell that is both autocrine and paracrine?
What cells in the body can release paracrines?
all cells
What is responsible for long distance communication?
endocrine and nervous systems
How do endocrine systems communicate?
How does the nervous system communicate?
using combination of electrical and chemical signals
How do the nerve cells work?
electrical signal travels along a nerve cell until it reaches the end of the cell where it is translated into a chemical signal secreted by the neuron
What are the 4 components of the chemical communication system?
neurotransmitters, hormones, neurohormones, cytokines
What do neurotransmitters do?
provide communication between one neuron and another or between a neuron and its effector cell
What is a chemical signal called a neurotransmitter?
if the chemical signal diffuses from the nueron across a narrow extracellular space to a target cell
Are neurotransmitters short or long range chemical messengers?
short range
What cells do neurotransmitters act on?
act locally on adjoining target cell, may be another neuron, a muscle or a gland
Are neuronal signals accurate?
Yes neuronal signals through neurotransmitters can be restricted to an individual cell.
Is neuronal communication fast?
Yes neuronal communication can be very rapid, essential for locomotion
What are the two classes of neurotransmitters?
excitatory neurotransmitters and inhibitory neurotransmitters
What do excitatory neurotransmitters do?
cause depolarisation of postsynaptic membranes, promote action potentials
What do inhibitory neurotransmitters do?
cause hyper polarisation of postsynaptic membranes, suppress action potentials
What are examples of catecholamine neurotransmitters?
epinephrine, norepinephrine, dopamine
What are examples of amino acid neurotransmitters?
glutamate, GABA, glycine, proline
What are examples of morphine like substance neurotransmitters?
endorphins, enkephalins, endomorphines, dymorphines
What are examples of peptide neurotransmitters?
insulin, prolactin, HGH, vasopressin
What are characteristics of hormones?
cell to cell communication, made in glands/cells, transported by blood, activates physiological response, distant target tissue receptors, provide communication that allows regulation of other cells
What do hormones control?
rate of enzymatic reactions, transport of ions or molecules across cell membranes, genes expression and protein synthesis
Can hormones exert effects at very low concentrations?
What are the 3 classification of hormones?
peptide hormones, steroid hormones, tyrosine derivatives
How are peptide hormones made?
made in advance, preprohormone-prohormone-active hormone
Where are peptide hormones stored?
in secretory vesicles
How are peptide hormones transported?
in dissolved form in blood
What are examples of peptide hormones?
insulin, parathyroid hormone, posterior pituitary hormone
How are steroid hormones made?
synthesised on demand from precursors, derived from cholestrol
Are steroid hormones lipophobic or lipophillic?
How are steroid hormones transported?
bound to carrier proteins in blood
Where are steroid hormone receptors found?
within the cell in cytoplasm or nucleus
What are examples of steroid hormones?
oestrogen's, androgens, cortisol
What are tyrosine derivatives?
amine hormones, small molecules structurally related to amino acids
What are derivatives of tyrosine?
Thyroid hormones, catecholamines, epinephrine, norepinephrine
What are derivatives of tryptophan?
dopamine, serotonin, melantonin
How are tyrosine derivatives formed?
by the actions of enzymes in cytoplasm of cells
How do the tyrosine derivatives exist in the body?
thyroid hormones use transport protein, catecholamines stored in performed vesicles or can exist in the plasma in free form
What are neurohormones?
chemical messengers released by the neuron that diffuse into the blood
What hormones does the hypothalamic neuron release?
oxytocin, antidiuretic hormones