Nerve And Muscle Flashcards
What is an afferent nerve?
Transmits information from the body to the CNS
What is an efferent nerve?
Transmits commands from CNS to all areas of the body
What does the autonomic system relate to?
Supplies the internal organs
Involuntary issues- has both parasympathetic and sympathetic functions
What direction does an impulse travel along a neuron?
From dendrites towards axon terminals
In the phospholipid bilayer which is hydrophobic and which is hydrophillic?
Tails are phobic, heads are phillic
What is depolarisation?
Polarity inside the cell becoming more positive
What is hyperpolarisation?
Polarity in the cell becoming more negative
what is potassium diffusion potential?
K+ diffuses down the concentration gradient via leaky channels, as positive charges leave the cell becomes more negative compared to outside causing some K+ to diffuse back, eventually hits equilibrium where inflow=outflow
Sodium potassium pump
Electrogenic pump
Pumps 3 Na+ ions out in exchange for 2K+, inside of cell loses 1+ ion maintaining negative potential inside
What happens inside a resting cell?
Potassium leak channels open- diffusing down the conc gradient
Voltage-gated sodium channels closed- no free movement of sodium across the membrane
Sodium-potassium pump working- effective loss of +ve charges from inside the cell
What is the resting membrane potential?
Electric potential that exists across the cell membrane in the resting cell, normally around -70mV
What is an action potential?
All or nothing events
Process of neuronal signal transmission, rapid changes to membrane potential allowing electricity to flow along the neurons
What is an action potential stimulated by?
Depolarisation of the cell which leads to the opening of voltage gated sodium ion channels, depolarising the cell further, when membrane potential hits -55mV permeability increases as more sodium channels open.
What is the threshold potential of an action potential
-55mV! If not hit the action potential can’t go through
What is the absolute refractory period?
Voltage gated sodium channels will not respond to any amount of stimulus so no action potentials possible.
What is the relative refractoryperiod?
Voltage-sodium gates are closed but voltage gated potassium channels are open allowing for hyperpolarisation but a much stronger stimulus is needed to reach the threshold potential
What is saltatory conduction?
Action potentials jump between nodes of ranvier between each myelinated sheath, allows for faster conduction
Where is myelin produced in the PNS?
Schwann cells
Where is myelin produced in the CNS?
Oligodendrocytes
What are chemical synapses?
Specialised region for transmission of chemical signals (usually via neurotransmitters)
One way transmission only
What is a neurotransmitter?
Chemicals that cross the synapse inducing changes in membrane potential
Effects can be excitatory (depolarisation) or inhibitory (hyperpolarisation)
How do neurotransmitters cross the synapse?
1)Presynaptic membrane depolarises causing voltage gated calcium ion channels to open.
2) calcium allows the neurotransmitter vesicle to bind to the presynaptic membrane and then be released
3) signal crosses the synaptic cleft and enters the post synaptic terminal via ionotropic or metabotropic receptors
Name two excitatory neurotransmitters
Acetylcholine and glutamate
Name two inhibitory neurotransmitters
Dopamine and glycine
Which neurotransmitter is used in skeletal muscle?
Acetylcholine
What neurotransmitter is used in the parasympathetic system?
Acetylcholine in both pre and post ganglionic receptors
What neurotransmitter is used in the sympathetic system?
Acetylcholine for preganglionic receptors
Epinephrine and norepinephrine for postganglionic receptors
What are the three types of muscle?
Skeletal, smooth and cardiac
What is the name of a contractile unit of muscle fibres?
Myofibrils
What sheaths a fasicle?
Perimysium
What sheaths a bundle of myocytes?
Endomysium
What sheaths the entire muscle?
Epimysium
What is a sarcomere?
A repeating contractile section of thick/thin muscle filaments
What is needed to remove troponin-tropomyosin?
Calcium
