PSYC 280: UNIT 2

What are neurons?

• nerve cells

• 80 to 90,000,000,000

• You lose about 85,000 per day

• Diverse shapes and types

What is the Glia?

• The basic support cells

• 80 to 100,000,000,000 of them

• 4 main types

Multipolar neuron

a nerve cell with many branches coming off it
(most common type in the brain)

Bipolar neuron

a nerve cell with two branches
(often used in senses like vision or smell)

Monopolar neuron

a nerve cell with one main branch
(often carries touch or pain signals)

Golgi: reduced silver strain

• completely stains entire neuron

• Only stains a minority of cells

• Impressive views of complete cells against unstained background

How are cells studied?

They are studied by histology= Tissue analysis

Nissan stains

• Nissl substance a.k.a. rough ER distributed throughout cell body

• Thus all cell bodies are stained

weigert stain

Selectively stains, nerve fibres (axons)

autoradiogrqphy

• metabolic; 2 deoxyglucose

• Constituent e.g. steroid auto radiography

immunochemistry

• uses labelled antibodies to identify cell proteins

• In principle, what proteins are being made and where?

In situ hybridization histochemistry

• uses labelled antisense RNA to identify mRNA messages

• In principle, what genes have been turned on and where

How do you classify neurons?

• by shape

• By size

• By function

Neuron classification: By Shape

200 different shapes

Neuron classification: Size

• somata buddies range from 10 to 100+ micrometres

• Large types: pyramidal, perkinje , Golgi type one projection

• Small types: granule, spindle, Stellate, golgi type two (local)

Neuron classification: Function

• Motor neurons= motor= muscle

• Sensory neurons= sense receptors

• Interneuron= local circuit, neuron to neuron, the majority

What are dendrites?

• input

• Have a special membrane at synapsis called post synaptic thickening, which contains receptors

• Dendritic spines maximize surface area and appear to be plastic, which may change in learning

What is the soma?

• synthesis of many important substances, e.g. structural proteins, and transmitters

• Summation like integration of signals from the various dendrites

• Fire decision is made at axon hillock

What is the axon?

• conducts a electrical and fast neural impulse called the action potential

• May have numerous branching axon collateral

• At axon terminals a.k.a. Boutons, the impulse is translated into a release of neurotransmitter molecules.

How does transmitter get into the axon terminals?

1. Gene transcribed

2. Synthesis of either transmitter (if large molecule/ peptide) or transmitter synthesis enzymes by ribosomes of rough ER

3. Packaged into transport vehicles by Golgi apparatus

4. Axoplasmic transport down to axon terminals

   1. Kinesin associated with slow transport

   2. Dynein associated with fast transport

5. For small molecule transmitters: enzymes synthesis molecules of transmitter locally in axon terminal

6. Transmitter molecules are loaded into synaptic vesicles

7. Vehicles await impulses than migrate, synaptic membrane and rupture into the synaptic cleft

Afference vs. Efference

toward versus away from a particular location

Divergence vs. Convergence

• sensory info is divergent to many places from one place

• Motor control is convergent from many places to one place, the muscle

What is nuclear processing?

Glia: astrocytes

• star shaped

• Some have suckers connecting to blood vessels, conduit for nutrients

• Some contribute to the tough membrane surrounding the brain

• Secrete growth factors

• Can become cancerous- astrocytoma

Glia: microglia

• weenie

• Very migratory

• Scavenge at sides of damage

Glia: Oligodendrocytes

• project to numerous axons

• Wrap a myelin sheath around axons

• Milan insulate gaps between sheets, called nodes of Ravier

• Nodes allow for saltatory conduction

• Oligodendrocytoma

Glia: Schwann cells

• like oligos, but only on peripheral nerves

• Each one Schwann cell myelinates only one part of one axon

• Same nodes of Ranvier

• Schwannoma

Planes: Sagittal

Cutting the body in half nose to butt, separates left and right

Planes: Coronal

Cut the body in half in the middle vertically, separates back to front

Anterior versus posterior

Planes: Horizontal

cut the body in half horizontally in the middle, separates top to bottom

Grey matter vs white matter

• Grey matter = the part of the brain that thinks and processes information

• White matter = the part that carries messages between brain areas

The meninges

three types

• Dura Mater

  • Tough mother

  • Fibrous outer covering

• Arachnoid layer

  • Spider Webbie spongy layer full of fluid

• Pia Mater

  • Soft mother

  • Delicate cling to surface of brain

All of which are only 50 g