W2/L4 - NEURONS, SYNAPSES & NERVOUS SYSTEMS Neural Communication – Cells & Resting Membrane Potential

Question 1

Textbook concepts

Answer 1

Campbell Biology, 11th edn, 2017 – Chpt 48
Concept 48‐1: Neuron structure and organisation reflect
function in information transfer
Concept 48‐2: Ion pumps and ion channels establish the
resting potential of a neuron

Question 2

Neuron

Answer 2

Most important cell in terms of relating information

The structure of neurons is important in order to understand its mechanism.

Dendrites - collects information to the main of the cell

Axon hillock, the “fatter” part of axon, where the signal path starts

Signals going out from axon hillock are electrical.

At the end of one neuron to the start of the next there is a synapse that releases chemical and transmits from one nuron to the next

First neuron of a chain is called a presynaptic neuron, second neuron is called postsynaptic neuron

Question 3

Structural divcersity of vertebrate neurons

Answer 3

Sensory neuron (visual, hearing, touch etc) cell body sits somewhere along the axon

Interneuron cell body sits in between axons (branched axons)

Motor neuron dendrites pull info from surrounding to the cell body which is then connected to axons

Question 4

Nerve

Answer 4

A nerve consists of many neurons.

Nerves have axons, connective tissue, axons and blood vessels.

Question 5

Glia - supporting cells

Answer 5

Glia – from Greek for glue
Vital for structural integrity and normal function
10‐50 times more glia than neurons in the mammalian brain

1. CNS: astrocytes, microglia, ependymal cells, oligodendrocytes
2. PNS: satellite cells, Schwann cells’

CNS = central nervous system

PNS = Peripheral nervous system

Question 6

Astrocytes

Answer 6

CNS
Provide structural support
Regulate extracellular concentration of ions and neurotransmitters
Formation of the blood‐brain barrier

Question 7

Oligodendrocytes and Schwann cells

CNS PNS

Answer 7

Form myelin sheaths around axons (electrical insulator)
Lipid membranes: the insulator

Question 8

In all cells

Answer 8

• THERE ARE GRADIENTS OF IONS ACROSS THE CELL MEMBRANE
• THE RESTING MEMBRANE POTENTIAL IS NEGATIVE

Question 9

Resting membrane potential applies to ALL CELLS

Answer 9

Na+/K+- ATPase (Active transporter) uses ATP directly

• Pumps 3x Na+ out of the cell
• Pumps 2 x K+ into the cell

Net negative charge inside compared with outside

Electrogenic pump generates a potential energy across cell

OUTSIDE (+)

5 mM K+ 150 mM Na+ 120 Mm Cl-

INSIDE (-)

140 mM K+ 15 mM Na+ 10 mM Cl- 100 mM A-

The membrane at rest has many open K+ channels and few on An_ or Cl- channels

• Buildup of ‐ve charge in neuron: limited by electrical gradient vs. chemical gradient of K+
• Equilibrium potential in neuron: approx ‐70 mV