High School Biology : Tissues, Organs, and Organ Systems
Study concepts, example questions & explanations for High School Biology
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Example Questions
Example Question #271 : Tissues, Organs, And Organ Systems
Into what structure does a neuron release neurotransmitters?
Soma
Axon
Dendrite
Synaptic cleft
Nodes of Ranvier
Synaptic cleft
Neurotransmitters are released from the axon terminal into the synaptic cleft.
Neurons are essential for transmitting signals, but do so without actually touching one another. The space between neurons is known as the synaptic cleft, or synapse. When a signal reaches the end of one neuron at the axon terminal, it causes neurotransmitters to be released from vesicles. The neurotransmitter molecules travel to the dendrites of the next neuron, which receives the signal and passes it down the next axon.
The soma is the cell body of the neuron, which synthesizes proteins and integrates incoming signals. Nodes of Ranvier are regions along myelinated axons that allow for faster action potential conduction.
Example Question #11 : Nervous Tissue
Influx of sodium ions is very crucial for cell activity. The influx of sodium ions in an action potential causes which of the following?
Depolarization
The fusion of vesicles to the presynaptic end plate
Hyperpolarization
Repolarization
Depolarization
Influx of sodium ions causes depolarization in a cell. Influx of sodium ions causes the membrane potential to become more positive and leads to activation of cell activity. Repolarization is done by the efflux of potassium ions. Hyperpolarization is a state in which a cell cannot conduct another action potential. It must reach its resting membrane potential before it can cause another action potential to occur.
Example Question #12 : Nervous Tissue
Which of the following cells proliferates in response to injury?
Astrocytes
Microglial cells
Oligodendrocytes
Ependymal cells
Astrocytes
Astrocytes are responsible for proliferating in regards to brain injury. They also help to make the blood brain barrier (BBB) and are a glycogen fuel reserve buffer. Microglial cells are phagocytes of the central nervous system. They respond to tissue damage by differentiation into large phagocytic cells. Myelin helps to wrap and and insulate axons. It increases space constant (length constant) and increases conduction velocity. Oligodendrocytes myelinate the axons of neurons in the central nervous system.
Example Question #273 : Tissues, Organs, And Organ Systems
What is the standard resting potential in a neuron?
The inside of a neuron always has a net negative charge at resting state and only becomes positive briefly when threshold is reached causing an action potential. This is due to the concentration and flow of positive sodium and potassium ions that exist at differing gradients when the neuron is at rest.
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