Neurons, glial cells, & synapses

2 types of cells

1. neurons

2. glial cells (neuroglial cells)

Neurons

generate and transmit info to control body functions and allow thought, emotions, and memories

Glial cells

surround and support the neurons. some speed nerve transmission by insulating axons with myelin

Cell body

contains cell nucleus and DNA

Dendrites

dendretic spine are usually where nerve cells recieve input from other neurons

axon

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

axon terminal

aka synaptic terminal

action potential

the movement of ions across the cell membrane creates an electrical signal

- travel towards the axon terminal

5 types of glial cells

1. Astrocytes

2. Oligodendroglial cells

3. Microglia

4. Ependymal cells

5. Schwann cells

Astrocytes

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

(contributes to metabolism of the CNS)

Oligodendrogllial cells

form the myelin sheath that insulates the axons in the brain and spinal cord (forms white matter in CNS)

Microglia

migrate to site of injury. act like phagocytes to remove and degrade damaged cells

Ependymal cells

line ventricles of the brain and central canal of the spinal cord, produce CSF

Schwann cells

surround and protect the peripheral nerve fibers, form myelin sheath, a assist in regeneration by forming guiding tunnels for regrowth

Multiple Sclerosis

• autoimmune

• ammune system attacks and injures myelin in the brain and spinal cord

• sensory loss & spastic paralysis

Guillain-Barre Syndrome

• autoimmune

• immune system destroys myelin surrounding peripheral nerves

• Flaccid paralysis, sensory loss, or hypersensitivity

• ability to breath is affected if phrenic nerve is involved

Damaged neuron cell bodies

the entire nerve cell dies

when neurons die

they release chemical that can be toxic to nearby cells

CNS neuron repair

Neurons in CNS are unable to regenrate their axons

Peripheral neuron repair

neurons in PNS regenerate their axons at a rate of approximately 1 mm per day

2 types of synapses

1. Electrical synapses

2. Chemical synapses

Electrical synapses

tiny channels called gap junctions that allow ions to flow from one neuron to the next

(produce very fast response)

Chemical synapses

one neurons communicates with another cell by releasing a chemical called a neurotransmitter

Small-molecule neurotransmitters

are either amines or amino acids

Ex: Acetylcholine, dopamine, histamine, norepinephrine

Large-molecule transmitters

are peptides

Ex: substance P, endorphins, enkephalins

Myasthenia gravis

antibodies block, alter, or destroy the receptors for acetylcholine at the neuromuscular junction which prevents the muscle from contracting

signs of myasthenia gravis

• weakness of eye muscles

• droopy eyelids

• blurred or double vision

• difficulty swallowing

  • impaired speech

Parkinsons

patients have a decrease of dopamine stored in the substantia nigra

signs of parkinsons

• bradykinesia

• rigidy

• tremor

• postural instability

Botox (botulism toxin)

prevents the release of acetylcholine at the nueromuscular junction, which results in lack of muscle contraction

Use of botox

to decrease muscle contraction for patients with spastic muscles (Ex: CP)

Synaptic plasticity

biological basis of long-term learning and memory

synaptic pruning

little-used neurons and synapses explain why memories may fade with time