Cells and Action Potentials Flashcards
what is the heiracrhy of the body?
- chemical/atomic-proteins, ions, molecules
- Cells, basic building block of all life
- tissues- cluster of identical cells (eg epithelial, musclular, nerve)
- organs- a collection of the same tissue bunched together, forming a structure (eg. heart)
- Organ Systems- multiple organs grouped together(digestive system
- Body
what are the four components of the cell which is important when discussing EMGs and action potentials?
- nucleus
- cell membrane
- intracellular fluid
- extracellula fluid
what is the nucleus and why is it important?
brains of the cell, which stores the cells genetic material
what is the cell membrane and why is it important?
- made of a phospholipid bilayer with imbedded proteins.
- impedes water penetration, while fat solublle substances may pass through
- possess ionic channels
- contains the entirity of the cells contents
what is the extracellular fluid and why is it important?
- contains ions and nutrients required to sustain cell life.
- mainly consists of dissolved sodium, carbonate and bicarbonate ions
what is the intracellular fluid and why is it important?
- fluid enclosed by the cell membrane
- Contains dissolved potassium, magnesium, and phosphate ions.
- Also contains oxygen, glucose, fatty acids and waste products
what are the parts of a nerve cell?
cell body: soma
Dendrites: Recieving Ports
Axon: many times the length of cell body, connects to other nerves via synapses
how is a potential created across a cell membrane?
sodium/potassium pumps on the membrane fasciliate the flow of sodium and potassium ions to ensure there are more positive charges outside than inside the cell
this creates a resting cell membrane potential
what is the resting membrane potential by default?
-90mV(millivolts)
what is an action potential?
the change in electrical potential associated with the passage of an impulse along the membrane of a muscle cell or nerve cell.
what are the stages of an action potential and what to they entail?
- Resting State: all voltage gated sodium and potassium ions channels are closed
- Depolarisation: sodium channels open, an action potential begins when the neuron is deplarised to its threshold potential
- Repolarisation: once the cell reaches its peak positive potential, sodium channels become inactivated and potassium channels open. The cell repolarises to a negative membrane potential
- Hyperpolarisation: potassium channels remain open and sodium channels inactivated the membrane potential becomes more negative than the resting potential
what are the forms of excitiation that can initiate an action potential?
- mechanical disturbance( e.g sensory receptors on skin)
- chemical effects( e.g neutrotransmitters to transmit signals between neurons)
- passage of electricity( e.g current between heart muscle cells and smooth muscle cells)
what are the properties of the rarefactory period?
- a new action potential cannot occur in an excitable fibre if the membrane is still depolarised from the previous action potential
- the sodium channels remain inactivated after an action potential, and no amount of stimulus can reactive them
- the membrane potential must return to its resting potential to open these activation gates
- this rarefactory period last about 1/2500th of a second
why is the rarefactory period important?
- Ensure one-way traffic along a nerve
- Action potential travel away from the source of stimulation
- If the stimulus starts at one end, it will be forced to propagate along to the axon in the other direction
- Cannot re-excite the area it was already in
what is the general mechanism for a muscle contraction?
- Action potential travels along the motor nerve to ending on muscle fibres
- Neurotransmitter , acetylcholine(ACTY) secreted by nerve
- ACTY acts on local area of muscle fibre membrane, opens multiple ACTY gated channels
- Sodium ions rush through into the muscle fibre, initiating an action potential at this point along the membrane
- Action potential travels along muscle fibre membrane in the same way as the nerves
- Action Potential depolarises entire muscle membrane, action potential electricity flows through centre of muscle. Releases calcium ions.
- Calcium ions initiate attractive forces between actin and myosin filaments, causing them to slide along one another
- Calcium ions pumped back into sarcoplasmic reticulum, stored here until the next contraction
