Animal Electrical Signaling

Updated 2007-05-23 23:00


Question Answer
Neurons- primary cells
Glial cells- support cells for other neurons (like those that make up myelin)
What are the three types of neurons?Sensory neurons, interneuron, motor neuron
Sensory neuron-take environmental stimuli to CNS (sends signals to CNS)
Interneuron-in CNS only and integrates signals from sensory neurons
Motor neuron-sends signals from central nervous system to an effector
What are the two parts of the PNS? Afferent and efferent division
Afferent division-transmits sensory information to CNS (sensory functions)
Efferent division-carries commands from the CNS to the body (motor functions)
What are the two parts of the efferent division? Somatic and autonomic nervous system
Somatic nervous system-controls skeletal muscles and voluntary movement
Autonomic nervous system- controls internal processes like digestion and heart rate (involuntary processes)
What are the to parts of the autonomic nervous system?Sympathetic and parasympathetic division
Sympathetic division-fight or flight response prepare organs for stressful situations by speeding up heart rate,inhibiting action by digestive organs etc
Parasympathetic division- rest and digest -promotes relaxation and digestion by slowing down heart rate etc
How is the brain structured?In four different divisions those at the top being the most advanced while those at the bottom are more primitive
Medulla oblingata-autonomic center for regulating heart lungs and digestive system and which connects spinal cord to brain (primitive) makes up brain stem
Pons-relays sensory info to cerebellum and controls urination (primitive) makes up brain stem
Cerebellum-coordinates complex motor patterns (primitive)
Cerebrum-conscious though and memory (higher more advanced part of brain)
What are nerves made up of? Millions o neurons
Dendrites-collect electrical signals
Cell body-integrates incoming signals and generates outgoing signal to axon
Axon- passes electrical signals to dendrites of another cell or to an effector cell
What do Na+K+ATPase pumps create? A resting membrane potential of -70 mV by having a ton of Na+ on outside of cell and K+ on inside of cell
When are voltage-gated Na+ channels closed? At resting potential
When do the voltage-gated Na+ channels open? When the membrane is depolarized
If Na+K+ATPase pumps were not there what would happen? There would be no concentration gradient and therefore the neurons couldn’t generate action potentials
Where are Na+ and Cl- ions more concentrated?Outside of cell
Where are K+ ions more concentrated?Inside of cell
Ion channels-K+ leak channel is always open creating K+ to diffuse to outside of cell causing the inside with a net negative charge and creating an electroconcentration gradient (other leakages Na+ and Cl-nhappen but not as much)
What do voltage-gated channels do?Produce a neural signal by making rapid changes in membrane potential
Why do voltage gated channels open?Open in response to changes in voltage when cell is stimulated by another cell
Where are the voltage-gated channels located?In the nodes of Ranvier
What are myelin made of and what are they good for? They are made of Schwann cells which are fat/protein and are good because they make transmittion faster there are no Na+KATPase pumps in them and they don’t leak ions
Multiple sclerosis- autoimmune disease where antibodies in blood stream eat away at myelin sheath and this slows down neural transmission
What happens when the voltage-gated channels open?Cations get repulsed and move to the next node of ranvier (they get repulsed in both directions)
Action potential-stereotyped all or none change in membrane potential in response to stimuli
What are the four steps of an action potential? Polarization, Depolarization phase, re-polarization phase, and undershoot
Polarization-occurs at resting potential when there are more positively charged ions on the outside of cell rather than the inside. This is caused by the Na+K+ATPase pump
Depolarization- occurs when Na+ channels open making Na+ flow into cell by diffusion and K+ channels open making K+ flow out of cell by diffusion
Re-polarization-occurs as ions flow out of the axon (K+ flows out of cell)
Undershoot or hyper polarization-occurs when K+ channels stay open longer
Why do voltage gated channels only open in one direction? The other direction is refractory meaning once they have opened and closed they are less likely to open again for a short period of time and its not at resting potential yet
How do nerves stimulate other nerves, glands or muscles?By releasing a neurotransmitter into a synapse
What does the action potential activate? It opens the voltage gated Ca+2 channels which causes Ca+2 to rush in which stimulates exocytose of vesicles filled with neurotransmitters into synapse
What are the three parts of releasing neurotransmitter? First the action potential arrives and triggers entry of Ca+2 then in response to this synaptic vesicles fuse with presynapstic membrane and release neurotransmitter then ion channels open when neurotransmitter binds and ion flows cause change in postsynaptic cell potential
Examples of neurotransmittersnor epinephrine, dopamine, seratonin
What happens if there is too much seratonin in body?Neurons get rid of receptors so when you get off a high you come way down since the receptors aren’t as sensitive
How does Prozac work? Theres selective seratonin reuptake it acts like an inhibitor and keeps seratonin in the synapse longer
How does stimuli go through neuron?From dendrite to axon only!
Electrochemical gradient-when you have both an electrical and concentration gradient together


Question Answer
How do non-steroid hormones signal transmitted into cells interior if it is lipid insoluble not able to get through plasma membrane?Target cells have receptors on cells suface, the hormone then binds to the receptor (first messenger) this activates the G protein which activates adenylyl cyclase which catalyzes ATP to cAMP (second messenger) whose concentration increases inside cell creating a signal which activates protein kinase A which phosphorolates phosphoroate kinase these break down glycogen to glucose and exit liver cells and enter the blood strem.