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Physiological Systems Lecture 6
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- 1What are the four mechanisms of cell communication?Direct Contact
Paracrine Signalling
Endocrine Signalling
Synaptic Signalling - 2What two things does cell communication require?Ligand - signalling molecules
Receptor Protein - molecule to which receptor binds - 3What is Direct Contact Signalling?Molecules on the surface of one cell are recognised by the receptors on the adjacent cell.
- 4What is Paracrine Signalling Communication?Signal released from a cell has an effect on a neighbouring cell
- 5What is Endocrine Signalling Communication?Hormones released from a cell affect other cells throughout the body
- 6What is Synaptic Signalling Communication?Nerve cells release the signal (neurotransmitter) which binds to a receptor on nearby cells.
- 7What are the types of Cell Surface Receptors?Ion Channel Linked Receptors
Enzyme Linked Receptors
G Protein Linked Receptors - 8What are the types of receptors?Cell Surface receptors or Intracellular receptors
- 9What are intracellular receptors?Located within the cell, they are receptive to steroid hormones that have a non polar lipid soluble structure, as they can cross the cell membrane to the steroid receptor and affect gene expression.
- 10What is a common way of changing the activity of a protein?Phosphorylation of proteins, a cells response to a signal that can activate or inactivate the protein.
- 11What are G Protein Receptors?G Protein Receptors can break down a substance or activate an enzyme or ion channel. Eg. cAMP, iP3, Ca²⁺
- 12What are receptor kinases?Receptor kinases are the most common type of enzyme linked receptors, and can influence cell cycle, migration, metabolism and proliferation. Eg. Insulin Receptors
- 13What are the types of ion channels?Leakage (non gated) channels
Gated channels - 14What are the features of Leakage (non gated) ion channels?They are always open
info: Nerve cells have more K⁺ than Na⁺ leakage channels, therefore membrane permeability to K⁺ is higher, explaining the resting membrane potential of -70mV - 15What are the features of Gated Ion Channels?Gated channels open and close in response to stimulus.
Eg. Voltage gated Na⁺ channels (one polypeptide chain with 4 domains) 6 membrane spanning α helices, one of which is a voltage sensing helix), voltage gated K⁺ channels (four separate polypeptide chains, each comprising one domain) - 16What is an action potential?Summarised: Resting potential is -70mV
Depolatisation is the change from -70mV to +30mV
Repolarisation is the reversal from +30mV back to -70mV - 17What is an action potential?A graded depolarization brings an area of an excitable membrane to threshold.
Sodium channel activation occurs.
Sodium ions enter the cell and depolarisation occurs.
Sodium channels are inactivated.
Voltage-gated potassium channels open and potassium moves out of the cell, initiating repolarization.
Sodium channels regain their normal properties.
A temporary hyperpolarization occurs. - 18How does propagation of an action potential work?An action potential propagates over the surface of the axon membrane.
As Na flows into the cell, the voltage of adjacent areas is effected and the voltage gated Na channels open.
The travelling is called a nerve impulse. Continuous conduction (unmyelinated fibres) - step by step
Saltatory conduction (myelinated fibres) - jumping, only at nodes of Renvier - 19What is a neuromuscular junction?Synapse is the functional junction between one neuron and another or between a neuron and an effector.
- 20What are the events that occur after the nerve signal?Arrival of nerve impulse at nerve terminal causes release of aCh from synaptic vesicles.
aCh binds to receptors on muscle motor end plate opening the gated ion channels so that Na can rush into the muscle cell.
Inside of the muscle cell becomes more positive, triggering a muscle action potential that travels over the cell and down T tubules.
The release of Ca from the SR is triggered and the muscles will shorten and generate force.
Acetylcholinesterase breaks down aCh attached to receptors on the motor end plate so the muscle action potential will cease and the muscle cell will relax. - 21What are some pharmacological examples of cell communication?Botulinum toxin - blocks neurotransmitter release
Curare - causes muscle paralysis by blocking ACh receptors
Pesticides - cholinesterase inhibitor causing paralysis
Neostigmine - anticholinesterase agent that strengthens weak muscle contractions - 22What is Myasthenia Gravis?Autoimmune disease in which antibodies attach neuromuscular junctions and bind ACh receptors in clusters.
Symptoms are drooping eyelids, weakness of eye muscles, double vision, difficulty swallowing, weakness of limbs, respiratory failure
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- Fichas sobre Physiological Systems Lecture 6, creado por finlayobrien el 13/04/2015.
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