Neurons Synapses and Signaling

A simple nervous system

• must include chemical senses, mechanoreception, and vision

• includes a minimum of 12 ganglia

• has information flow in only one direction: toward an integrating center

• has information flow in only one direction: away from an integrating center

• has information flow both toward and away from an integrating center

Most of the neurons in the human brain are

• sensory neurons

• motor neurons

• interneurons (relay neurons)

• auditory(hearing) neurons

• olfactory(smelling) neurons

Most of the organelles in a neuron are located in the

• dendritic region

• axon hillock

• axon

• cell body

• axon terminals

In certain large animals, this type of neuron can extend beyond one meter in length

• glial cell in the brain

• a sensory neuron

• an interneuron

• a glial cell at a ganglion

• a neuron that controls eye movements

A nervous system can alter activities in its target cells in muscles and glands because

• they are electrically coupled by gap junctions

• the target cells have receptor proteins for the signals released by the nervous system

• the nervous system releases signals into the blood to control the target cells

• the target cells that become disconnected from the nervous system rapidly die

• the target cells each have an internal neural network connected to the nervous system

In the communication link between a motor neuron and a skeletal muscle,

• the motor neuron is considered the presynaptic cell and the skeletal muscle is the postsynaptic cell

• the motor neuron is considered the postsynaptic cell and the skeletal muscle is the presynaptic cell

• action potentials are possible on the motor neuron but not the skeletal muscle

• action potentials are possible on the skeletal muscle but not the motor neuron

• the motor neuron fires action potentials but the skeletal muscle is not electrochemically excitable.

For a neuron with an initial membrane potential at -70 mV, an increase in the movement of potassium ions out of that neuronʹs cytoplasm would result in

• depolarization of the neuron

• hyperpolarization of the neuron

• the replacement of potassium ions with sodium ions

• the replacement of potassium ions with calcium ions.

• the neuron switching on its sodium-potassium pump to restore the initial conditions

Though the membrane of a ʺrestingʺ neuron is highly permeable to potassium ions, its membrane potential does not exactly match the equilibrium potential for potassium because the neuronal membrane is

• fully permeable to sodium ions

• slightly permeable to sodium ions

• fully permeable to calcium ions

• impermeable to sodium ions

• highly permeable to chloride ions

The operation of the sodium-potassium ʺpumpʺ moves

• sodium and potassium ions into the cell

• sodium and potassium ions out of the cell

• sodium ions into the cell and potassium ions out of the cell

• sodium ions out of the cell and potassium ions into the cell

• sodium and potassium ions into the mitochondria

The ʺselectivityʺ of a particular(specific) ion channel refers to its

• permitting passage by positive but not negative ions

• permitting passage by negative but not positive ions

• ability to change its size depending on the ion needing transport

• binding with only one type of neurotransmitter

• permitting passage only to a specific ion