Nervous System

• Astrocytes: They provide structural support and help regulate the chemical environment around neurons.
• Oligodendrocytes and Schwann Cells: They produce myelin, a coating that helps neurons transmit signals faster.
• Microglia: These are immune cells that defend against pathogens and clean up dead or damaged cells in the nervous system.
• Ependymal Cells: They line fluid-filled spaces in the brain and spinal cord, producing cerebrospinal fluid for protection and nourishment.
• enteric: division of the autonomic nervous system that controls the gastrointestinal tract
• peripheral nervous system: Nerves and Ganglia, Somatic (sensory and motor), autonomic (sympathetic and parasympathetic), enteric
• •Leak channels–Always open (passive movement), Can establish an electrical gradient
• Neurons have a resting membrane potential, typically around -70 millivolts, due to the separation of positive and negative ions across the neuronal membrane.
• An action potential begins with a stimulus, which can be a change in the environment or a signal from other neurons.
• If the stimulus is strong enough, it causes the membrane to depolarize, meaning voltage-gated sodium channels in the membrane open, allowing sodium ions (Na+) to rush into the neuron.
• The influx of positive ions makes the inside of the neuron more positive.
• Once the depolarization reaches a certain threshold (typically around -55 millivolts), it triggers a rapid and complete depolarization of the membrane.
• At the threshold, voltage-gated sodium channels open fully, leading to a rapid influx of sodium ions.
• This causes a spike in membrane potential, known as the action potential.
• The inside of the neuron becomes positively charged during the action potential.
• Shortly after reaching its peak, voltage-gated potassium channels open, allowing potassium ions (K+) to leave the neuron, repolarizing the membrane, bringing it back to a negative charge.
• Hyperpolarization is a phase where the membrane potential briefly goes below the resting level, caused by the continued efflux of potassium ions.
• The sodium-potassium pump actively transports sodium ions out of the cell and potassium ions back in, helping to restore the original ion concentration and membrane potential.
• Membrane potential can be calculated by using what equation?​

  ​Goldman-Hodgkin-Katz equation
• ​Neurotransmitter is released by exocytosis into the synaptic cleft.

  True
• ​The outward movement of sodium ions rapidly restores the negative resting potential.

  fasle
• All molecules and ions are in continuous random motion at temperatures above absolute zero as a result of thermal (heat) energy.

  True
• ​Several mechanisms can remove the neurotransmitter, such as being inactivated by specific enzymes within the sub-synaptic membrane.

  True
• An example of a messenger that acts as a neurotransmitter when released from a nerve ending or a hormone when secreted by an endocrine cell is norepinephrine.
• Voltage-gated sodium channel can exist in how many different conformations?

  Three
• Graded potentials are local changes in membrane potential that occur in varying grades or degrees of magnitude or strength.
• Action potentials occur in an all or none fashion
• ​What ion is more concentrated in the extracellular fluid (ECF)?

  Sodium ions
• Nerve and muscle are considered excitable tissues because they produce electrical signals when excited.
• The voltage-gated sodium channel has two gates: an activation gate and an inactivation gate.

  True
•  Contiguous conduction involves the spread of the action potential along every patch of membrane down the length of the axon.
• Neuroglia are nonneuronal cells found within the CNS that support and protect neurons.
• Myelin sheaths are formed by Schwann cells in the PNS and oligodendrocytes in the CNS.
• The dendrites and cell body are the neuron’s output zone because these components send out signals.

  False
• What law governs how concentration gradients and other factors influence the rate of net diffusion?

  Ficks law of diffusion
• An unmyelinated fiber has a low density of voltage-gated channels along its entire length.

  False
• An almost insignificant fraction of the total number of charged particles present in the body fluids is responsible for the membrane potential.

  True
• The total grand postsynaptic potential (GPSP) is a composite of all ESPS's and IPSPs occurring around the same time.
• ​In addition to neuromodulation, another means of depressing or enhancing synaptic effectiveness is presynaptic inhibition or facilitation.
• contiguous conduction involves the spread of the action potential along every patch of membrane down the length of the axon.