Lecture 18: Nervous System Cells and Resting Membrane Potential

Question 1

what are the three main functions of the nervous system?

Answer 1

1. sensory input - the info gathered by sensory receptors about internal and external changes. this info comes from skin and muscles (somatic) and from organs (viscera).
2. integration - the processing and interpretation of sensory input
3. motor output - activation of effector organs (muscles and glands) produces a response

Question 2

what cells make up the nervous system? and whats the name of the wiring that connects the nervous system?

Answer 2

cells are neurons and glia and the wiring is nerves.

Question 3

briefly explain structure of neuron and the role of components.

Answer 3

cell body - integrates all the input received
dendrites - receives input from other neurons
axon - sends output signals to next neuron

Question 4

what are the three different neurons? describe their structure and function.

Answer 4

multipolar - many processes extend from the cell body, all are dendrites except for a single axon

bipolar - two processes extend from cell body, one fused dendrite and one fused axon

unipolar - one process occurs from the cell body formed in centre of an axon

Question 5

how is information sent around the body?

Answer 5

sent through nerves, cranial nerves that connect to the brain and spinal nerves that connect to the spinal cord.

Question 6

what are glial cells?

Answer 6

glia = glue; they are connective and support function. there are four types in the CNS and two types in the PNS.

Question 7

what are the four different glial cells in CNS and function?

Answer 7

1. astrocytes; forms blood brain barrier and regulates ion and neurotransmitter levels. structural support
2. oligodendrocytes; myelinate axons which is a fatty layering around axons of neurons which insulates and increases speed of signal transmission
3. microglia; immune cells of the CNS
4. ependymal cells; line ventricles, e.g. lining cerebrospinal fluid in CNS cavities

Question 8

what are the two glial cells in PNS and function?

Answer 8

1. satellite cells; surround cell bodies in ganglia and regulate nutrients, gas and neurotransmitter levels around neurons
2. schwann cells; myelinate axons

Question 9

what is a membrane potential?

Answer 9

a membrane potential is caused by a difference in distribution of ions on each side of a membrane. thus, this creates a voltage across the membrane.

Question 10

what is the resting membrane potential in neurons?

Answer 10

approximately -70mV.

Question 11

how is a potential generated in a neuron?

Answer 11

1. differences in ionic composition of the intracellular fluid and extracellular fluid
2. differences in membrane permeability to ions

Question 12

how is the resting membrane potential maintained in neurons?

Answer 12

1. potassium channels in the membrane allow K+ to leak out of the cell
2. The Na+/K+ ATPase pumping 3 Na+ out and 2 K+ in (thus maintaining the concentration gradients of Na+ and K+).