Neurons: Functional Unit

Sistema nervioso

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Nervous system

* Cns

-BRAIN AND SPC

. PNS

cranial and spinal nerves

Neurons: functional unit

Characteristics of a neuron:

1. Responsive: they respond to signals from other cells (electrical or chemical)

2. Conductivity: electrical impulses, that’s how they communicate with one another

3. Secretory: they secrete neurotransmitters, which is a form of exosytosis

4. Postmitotic: limited repair possible. They don’t divide.

BLOOD BRAIN BARRIER

The fact that the capillaries that are feeding the brain are held together by very tight junctions which makes the brain very selective on what can get in or out. Paracelular transport is very restricted. Obstacle for drug delivery, restrict a lot of drugs so is very difficult to treaties difficult.

astrocytes (glial cell): they help maintain the integrity of the blood brain barrier

GLIA CELLS: supporting cells, they outnumber the number of neurons. They are mitotic cells, they can divide.

NEURON:

Cell body or soma

Nucleus: where the genetic info is stored, nutritional center

Dendrites: they receive the signals (neurotransmitters) they have a lot neurotransmitters reseptors

AXON hillock: where the action potential starts. Beginning of axon

Mylin sheet: covering the axon. Separated in segments which are called inner nodes, and the parts that are not covered are the nodes frotviere (speeds up the signal)

Axon: where actions are propagated can have a collateral axon.

Dendrites: receptive processes

Axon: conduct impulses, axon can branch to axon collaterals, they can be to a meter in length.

Schwan cells wrap the axon as the mylin sheet in peripheral nervous system

Axonal transport:

Axons can be up to a meter in length. We need proteins that are made in the cell body but we said that neurotransmitters release down in the synaptic terminal, which in this case can be up to 3 feet away, and so it should make sense to you that there are gonna be a variety of proteins, like all of those proteins that are required for vesicle release and store neurotransmitters are gonna me made up in the cell body, but they re gonna be transported to the synaptic terminal. And also, all worked out things are gonna be brought up to the cell body. And in cells that are very small it is not a big deal, but when you have a cell that can be up to 3 feet, that transport is not a trubule process, so we have to have specific proteins to do that, all cells have these but in neurons it becomes a little bit fore essential. And so there are molecular motor proteins that actually carry cargo on their back though the microtubules which are like highway systems for proteins to literally walk to bring the substances doun the synaptic terminal and viseversa.

ANTEROGRADE:

Away from the cell body to the synaptic terminal KINESINS MOTORS

RETROGRADE:

Away from the synaptic terminal to the cell body DYNEINS MOTORS

How is moving with regard s to the cell body

SENSORY NEURONS: AFFERENT NEURONS

Into cns

Motor (efferent)

Exit CNS to effectors

Autonomic motor neurons:

Gland and organs

Sympathetic: scared running away and parasympathetic: relax

Association (interneurons)

Within CNS

NERVES:

Bundle of axons, outside CNS. Most nerves convine motor neurons and sensory neurons

Glial cells:

PNS