Chemical Signals

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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?

hormones

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?

prostaglandins

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?

hormones

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?

Yes

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?

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

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