Gnarly Nervous Physiology Chapter Notes

I. Nerve Structure Review

II. Nerve Signals Membrane Potential Electrical charge difference across the plasma membraneElectrical charge difference across the plasma membrane Anions (-): Concentrated inside the cellAnions (-): Concentrated inside the cell Cations (+): Concentrated in extracellular matrixCations (+): Concentrated in extracellular matrix

II. Nerve Signals Resting potential: Membrane potential of an unstimulated neuronResting potential: Membrane potential of an unstimulated neuron Action potential: A nerve impulse that can be transmitted to another nerveAction potential: A nerve impulse that can be transmitted to another nerve

Nerve Signals Details 1.Resting: Na+ and K+ gates closed (resting potential) 2.Threshold: Na+ gates open 3.Depolarization: Na+ rushes into the cell (interior more +) 4.If signal is strong enough – generates an ACTION POTENTIAL 5.Repolarization: Na+ gates close, K+ channels open. K+ leaves cell (interior more -)

Nerve Signal Details (cont) 6.Undershoot: Inside gets extra – 7.Refractory Period: Na+ / K+ pump gets things back to normal.

III. Neuron communication at the Synapses A. The ProcessA. The Process *Cytoplasm at end of axon contains synaptic vesicles*Cytoplasm at end of axon contains synaptic vesicles The vesicles contain neurotransmittersThe vesicles contain neurotransmitters These are chemical messengersThese are chemical messengers

Neuron Communication at the Synapses 1. Ca+ gates open. Ca+ enters the cell 2.Synaptic vesicles merge with presynaptic nerve’s membrane 3.Releases neurotransmitter into synapse. Neurotransmitter binds with receptors on next neuron (postsynaptic) 4.Neurotransmitter bound to ion channel, opens it which allows ions to rush in (depolarize)

Nerve Communication at the Synapses If Na+ gates open, membrane becomes depolarized (more +) and results in excitatory postsynaptic potential. It may generate an action potential if strong enough.If Na+ gates open, membrane becomes depolarized (more +) and results in excitatory postsynaptic potential. It may generate an action potential if strong enough. If K+ gates open, membrane becomes polarized and results in inhibitory postsynaptic potential (more - because K+ goes out). No action potential.If K+ gates open, membrane becomes polarized and results in inhibitory postsynaptic potential (more - because K+ goes out). No action potential.

IV. Common Neurotransmitters A.Acetylcholine *Found at neuromuscular junctions. Stimulates muscle contraction. B. Epinephrine, Nor epinephrine, Dopamine, & Serotonin *Secreted between neurons in CNS *Dopamine and serotonin affect sleep, mood, attention and learning *Excessive dopamine is linked to schizophrenia *Some hallucinogenic drugs bind to serotonin and dopamine receptors

Mighty Muscular Physiology I. Mighty MuscularI. Mighty Muscular *Muscles only shorten or contract*Muscles only shorten or contract

Mighty Muscular A. Muscle StructureA. Muscle Structure *Muscle Cell= muscle fiber*Muscle Cell= muscle fiber *Cell Membrane= sarcolemma*Cell Membrane= sarcolemma *Cytoplasm= sarcoplasm*Cytoplasm= sarcoplasm *Endoplasmic Reticulum= Sarcoplasmic Reticulum*Endoplasmic Reticulum= Sarcoplasmic Reticulum

Mighty Muscular 1.Muscle fibers are made up of myofilaments 2.Myofilaments are made of actin (thin) and myosin (thick) microfilaments. 3.Repeating units along a muscle fiber are called sarcomeres--they are the contractile unit of the muscle. 4.Note on diagram: Z line, H zone, I band, A band, M line

Muscle contractions *Length of sarcomere is reduced (distance between Z lines gets smaller)*Length of sarcomere is reduced (distance between Z lines gets smaller) *I band shortens, A band stays the same, H zone disappears*I band shortens, A band stays the same, H zone disappears

Sliding Filament Model 1.ATP binds to myosin head 2.ATP----- ADP + Pi 3.Myosin head binds to actin forming cross-bridge 4.ADP + Pi are released. Myosin head changes shape. This slides the actin toward the center of the sarcomere (Z lines get closer) Whoo Hoo! Contraction! 5. ATP binds, releases myosin head. We start again. (Corpse is “stiff” because there is not ATP to undo the contraction)

It Can’t Be That Simple It Can’t Be That Simple *When muscles are at rest, the myosin binding sites on the actin are blocked by a protein called tropomyosin. The proteins in the troponin complex control the position of tropomyosin on the actin.*When muscles are at rest, the myosin binding sites on the actin are blocked by a protein called tropomyosin. The proteins in the troponin complex control the position of tropomyosin on the actin. For contraction to occur, the binding sites need to be uncovered. For contraction to occur, the binding sites need to be uncovered. Ca+ to the rescue!! Calcium binds to troponin, it alters the shape and exposes the myosin binding sites on the actin.Ca+ to the rescue!! Calcium binds to troponin, it alters the shape and exposes the myosin binding sites on the actin. So drink lots of milk!! No Ca+ ---no contraction!!So drink lots of milk!! No Ca+ ---no contraction!!