Nerve Cells and Nerve impulses

What are the two main parts of the Nervous system?

1. Central nervous system (CNS)

2. Peripheral nervous system (PNS)

What are the two main types of cells in the nervous system?

Neurons and glia cells

What is cephalisation?

Nerve tissue concentrated toward one end of an organism

Who demonstrated that neurons are separate cells

Ramon y Cajal and Camillo Golgi (Nobel Prize 1906)

What are the three main parts of a neuron?

1. Soma (Cell body)

2. Dendrites

3. Axon

What is the function of dendrites?

Receive input from other neurons

What is the function of the axon?

Transmit information to other neurons or effectors

What is the myelin sheath?

An insulating layer that speeds up electrical transmission

What cells form the myelin sheath in the CNS and PNS?

A. Oligodendrocytes (CNS)

B. Schwann Cells (PNS)

What are the three functional types of neurons?

A. Afferent (Sensory)

B. Efferent (Motor)

C. Interneurons

What is the role of Afferent neurons?

Carry information from receptors to eyes, ears, veins

What is the role of Efferent neurons?

Carry signals away to the effectors, either to muscles or glands

What is the role of interneurons?

Connect to other neurons and send information

What are the five key functions of glia?

1. Structural support

2. Myelination

3. Nutrient/ oxygen supply

4. Immune defence

5. Guide neuron migration

Which glia cell modulates synaptic transmission?

Astrocytes

What is resting polarisation?

When the membrane of a neuron maintains an electrical gradient between the inside and the outside of the cell

What is the resting membrane potential of a neuron (in mV)

-70

What causes the excitation of a neuron/ transmission of information

The change of the neurons’s potential

What two stages cause the excitation of a neuron?

1. Transmission of information from the exterior through dendrites to the cell body

2. Transmission from the cell body through the axon out of the neuron

What causes an action potential?

If the summed excitatory input exceeds threshold, the neuron fires

What is the “all or none” principle?

An action potential either occurs fully or not at all- its size does not vary

What is an EPSP?

Excitatory Postsynaptic Potential- depolarises the membrane (more positive)

What is an IPSP?

Inhibitory Postsynaptic Potential- hyperpolarises the membrane (more negative)

What are the 2 types of synapses?

Excitatory and Inhibitory

What is the deciding factor of whether the neuron is excited or inhibited?

The type of chemical released in the synaptic gap

What is summation in neural activity?

Combining postsynaptic potentials across space or time to reach threshold

What is threshold potential (in mV)

-55

What is action potential (in mV)

+40

What causes the huge spike in mV from resting to action

depolarisation

What causes the huge decrease in mV from action back to resting state

Repolarisation

Where does the action potential start?

At the axon hillock

How is action potential propagated?

Via saltatory conduction- jumps between nodes of Ranvier in myelinated axons

What causes symptoms in Multiple Sclerosis?

Demyelination of axons in the CNS