2 Neurons, Glial Cells, Synapses

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

Neurons and glial cells

Neurons

• Generate and transmit information to control body functions and allow for thought, emotions and memories

• Contains a cell body, numerous dendrites and a single axon with many terminal s

Glial cells (neuroglial cells)

• Surround and support the neurons

• Some speed nerve transmission by insulating axons with myelin

• Can divide

Cell body

Contains the cell nucleus and DNA

Dendrites

• Outgrowths of the cell body

• Have branches and small outgrowths called dendritic spines

Axon

Single long process that extends from cell body to make connections with other cells

Neuron axons

• Have branches called axon collaterals

• Each branch ends in an axon or synaptic terminal

• Contact other neurons, mm cells or glands

• Can be a few mm to 3 m

Babies have few dendritic spines which are developed by maintenance of knowledge and development of skill.

True

Action potential

• Movement of ions across the cell membrane that creates an electrical signal

• Membrane potential must reach threshold for this to happen

• Always travel towards the axon terminal

Astrocytes

• Glial cell

• Cause capillaries to form a blood-brain barrier to protect neurons from substances in the brain

• Help growing neurons find their targets during nervous

  system development

• Contribute to metabolism of the CNS

Oligodendroglial cells

• Glial cell

• Form the myelin sheath that insulates axons in the brain

  and spinal cord (forms the white matter in the CNS)

Microglia

• Glial cell

• Migrate to the site of injury. Act like phagocytes to remove and degrade damaged cells

Ependymal cells

• Glial Cell

• Line ventricles of the brain and central canal of the spinal cord

• Produce CSF (in ventricles)

Schwann cells

Surround and protect the peripheral nerve fibers, form myelin

sheath, assist in regeneration by forming guiding tunnels for regrowth

Multiple sclerosis (MS)

 Autoimmune

 Immune system attacks and injures myelin in the brain and spinal cord

 Sensory loss and spastic paralysis

Gillian-Barre Syndrome (GBS)

 Autoimmune

 Immune system destroys myelin surrounding

peripheral nerves

 Flaccid paralysis, sensory loss or hypersensitivity, blood pressure fluctuations, dysarthria (diff. speaking), dysphagia (diff. swallowing).

 Ability to breath is affected if phrenic nerve is involved

When neuron cell bodies are damaged, only part of the nerve cell dies.

False; the entire nerve cell dies

Necrosis

• Cell death caused by injury or illness

• Can be spread via a chemical toxin that is released

Which is true about neuron regeneration?

Neurons in CNS are unable to regenerate and neurons in the PNS can regenerate (at 1 mm per day)

Electrical synapses

• Tiny channels called gap junctions that all ions to flow from one neuron to the next

• Produce very fast responses

Chemical synapses

One neuron communicates with another cell by releasing a chemical (a neurotransmitter)

Small-molecule neurotransmitters

• Amines or amino acids

• Ex. acetylcholine, dopamine, histamine, norepinephrine

• Acetylcholine is always the one at the NM junction

Large-molecule transmitters

• Peptides

• Ex. substance P, endorphins, enkephalins

What is an example of a pathology related to the neurotransmitter acetylcholine?

• Myasthenia gravis

• Antibodies block, alter or destroy the receptors for the acetylcholine at the NM junction preventing muscle contractions

• S/S: weakness of eye mms, difficulty swallowing, weakness in extremities

What is a pathology related to the neurotransmitter dopamine?

• Parkinson’s disease

• Decrease of dopamine stored in substantia nigra

• S/S: bradykinesia, rigidity, tremor and postural instabiliy

Botox

• Prevents the release of acetylcholine at the neuromuscular junction, which results in lack of muscle contraction

• Can be uses to dec mm contraction for patients with spastic mm (such as cerebral palsy)

Synaptic formation is believed to be the biological basis of long-term memory and helps explain why, if not used, certain synapses (or memories) fade over time.

True

Quiz 1: People with Parkinson's disease usually have a deficit of which neurotransmitter?

Dopamine

Quiz 1: Where do neurons usually receive input from other neurons?

dendritic spines

Quiz 1: Which type of cells produce cerebrospinal fluid?

ependymal cells

Quiz 1: The electrical signal created by the movement of ions that sweeps across the cell membrane is called what?

action potential

Quiz 1: Which glial cells form the myelin sheath that insulates axons in the brain and spinal cord?

Oligodendroglial cells

Quiz 1: Which kind of glial cell helps create the blood-brain barrier?

astrocytes

Quiz 1: In the PNS, does damage to the axon typically cause the neuron to die?

No

Quiz 1: Does multiple sclerosis affect the CNS or the PNS?

CNS

Quiz 1: In which disease does the immune system produce antibodies to Ach receptors which result in muscle weakness and fatigue?

myasthenia gravis

Quiz 1: What is the result of a botulism toxin injection?

Decrease muscle contraction in patient with spastic muscles