Nervous Tissue Flashcards
Name the two primary divisions of the nervous system and provide examples of the contents of each division.
The nervous system has two primary divisions.
- The central nervous system - composed of the brain and spinal cord
- The peripheral nervous system - composed of the peripheral (spinal) nerves, cranial nerves, and autonomic nervous system.
Name the two subdivisions of the peripheral nervous system and a function of each.
The sensory (also referred to as the afferent) pathway carries sensory information to the CNS. The motor (also referred to as the efferent) pathway carries motor function from the CNS to the periphery.
What are interneurons?
Interneurons are nervous tissue that provide communication between the sensory neurons and motor neurons.
What are the properties of neurons?
Neurons are excitable, conductive, and have the ability to secrete neurotransmitters.
Describe the difference between an unmyelinated neuron and a myelin neuron.
Unmyelinated neurons do not have the insulating covering (adipose and protein) over the axon of a neuron. Myelinated neurons have the insulating covering over the neurons (some are called Schwann Cells). Large myelinated neurons have the ability to conduct and process information quicker than smaller unmyelinated neurons. A myelinated neuron could be found in skeletal muscle; an unmyelinated neuron can be found in the digesting system.
Describe the resting state of a nerves. Describe it in terms of resting potential measure and polarity.
Resting neurons (those not receiving or sending information) have a negative polarity and have a resting potential of -70mV.
Explain how the Na/K pump impacts the resting membrane potential.
While a nerve is at rest, there is an abundance of + charges outside the nerve cell and an abundance of - charged particles on the inside of the neuron. When a nerve is stimulated, the Na/K pump opens allowing an influx of Na to flow into the neuron causing the neuron to become positively charged. This “opening of the Na/K pump” is a continuous process down the entire axon; it shutsdown after there is no need for the stimuli; the result is Na exits the neuron and the internal polarity of the neuron returns to negative.
Describe the reflex arc as it pertains to placing your hand on a hot surface.
The sensory (or afferent) neurons carry the “hot” sensation from the persons hand to the spinal cord (CNS). It enters the dorsal horn of the spinal cord where the information is interpreted by the innerneurons. The innerneurons pass the information to the ventral horn of the spinal cord. From this location, motor (or efferent) neurons carry the motor response to the individuals hand that is on the hot surface; the motor response causes the person to pull his or her hand away from the surface.
Resting membrane potential is -70mV. What is the threshold potential that causes the Na+/K+ pump to open?
Na+ is allowed to enter the neuron once the threshold potential reaches -55mV. Once this potential is reached, we also refer to it as the “all or none” response. In other words, the nerve either fires or does not and the intensity does not get weaker as it travels the neuron.
The Na+/K+ channels are present along the entire length of the neuron. In unmyelinated neurons, these channels appear more frequent; in myelinated neurons, these channels appear only at the Nodes of Ranvier (in the PNS). Explain how these channels prevent a nerve signal from weakening.
Na+/K+ pumps line the neuron in an effort to keep the nerve signal moving in a chain reaction type of sequence. In other words, the Na+/K+ pumps on any given neuron are not open all at once. Rather, one section of the neuron opens causing that section to become polarized sending the signal along the axon. Once the signal reaching a “non-stimulated” section of the neuron, that set of Na+/K+ pumps then open causing that section to become stimulated and allowing the previous section to depolarize.
The neuron that passes information to another (or next) neuron is called the _____________.
presynaptic
