Nervous System Cells & Resting Membrane Potential

Question 1

Why is learning about the nervous system important?

Answer 1

Can provide new insights into methods of treatment

Question 2

Functions of the nervous system

Answer 2

1. Sensory input
2. Integration
3. Motor output

Question 3

Sensory input

Answer 3

Information from sensory receptors about changes, from skin/muscles (somatic) and organs (viscera)

Question 4

Integration

Answer 4

processing and interpretation of sensory input

Question 5

Motor output

Answer 5

activation of effector organs (muscles and glands) produces a response

Question 6

Components of the nervous system

Answer 6

Cells that make up the nervous system:
-neurons, glia

Wiring that connects the nervous system:
-nerves

Question 7

Neuron structure

Answer 7

Cell body
Dendrites
Axon

Question 8

Cell body

Answer 8

integrates all the inputs it receives

Question 9

Dendrites

Answer 9

receive inputs from other neurons

Question 10

Axon

Answer 10

Sends output signals, generates and propagates action potentials; sends signals around the nervous system

Question 11

neurons come in different shapes and sizes

Answer 11

multipolar, Bipolar, unipolar

Question 12

Multipolar

Answer 12

Multiple dendrites, single axon

Question 13

Bipolar

Answer 13

Two processes extend from the cell body. one is a fused dendrite, the other is an axon

Question 14

Unipolar

Answer 14

One process extends from cell body
Forms central and peripheral processes comprising an axon

Question 15

Information is sent around the body in nerves

Answer 15

• Bundles of axons surrounded by connective tissue; carry information around the body.

Cranial nerves: connected to the brain
Spinal nerves: connected to the spinal cord
Most nerves carry both sensory (afferent) and motor (efferent) axons.

Question 16

Components of the nervous system - glial cells

Answer 16

Glia= glue, connective and support function
-Four types in the CNS
-Two types in the PNS

Question 17

Glial cells in the CNS

Answer 17

Astrocytes: Form blood-brain barrier, regulate ion/neurotransmitter levels, provide structural support.

Oligodendrocytes: Myelinate axons, contributing to white matter.

Microglia: Immune cells of the CNS.

Ependymal Cells: Line ventricles.

Question 18

Myelination

Answer 18

Fatty layering around the axons of neurons

Question 19

Glial cells in the PNS

Answer 19

1. Satellite cells - surround cell bodies in ganglia
2. Schwann cells - myelinate axons

Question 20

Membrane potential

Answer 20

-Voltage across a cell membrane
-Caused by ion distribution differences
-Present in all cells
-Source of potential energy for neuron operation

Question 21

Resting membrane potential in neurons

Answer 21

-Approximately -70mV
-Neuron is ‘resting’ and not active
-Measured by an electrode inside the neuron

Generated by:
1. Differences in ionic composition (intracellular vs. extracellular fluid)
2. Differences in membrane permeability to ions

Question 22

Difference in ionic composition of the intracellular fluid in neurons and extracellular fluid

Answer 22

High K+ inside the cell
High negatively charged proteins inside the cell
High Na+ outside the cell
High Cl- outside the cell

Resting membrane potential of -70mV due to more negatively charged ions inside the cell compared to outside

Question 23

leakage channels

Answer 23

Always open, allowing ions to leak through. There are channels permeable to K+ and others permeable to Na+.

Question 24

Maintenance of the resting membrane potential in neurons

Answer 24

Maintained by:
1. Potassium channels allowing K+ to leak out (few Na+ leakage channels)

2. Na+/K+ ATPase pump moving 3 Na+ out and 2 K+ in, maintaining concentration gradients

Question 25

Neurons (and muscles) are excitable

Answer 25

-Rapid changes in membrane potential due to stimuli
-Voltage-gated ion channels required
-Contrasted with leak ion channels for maintaining resting potential