Neurons and Glia

Cells of the nervous system

• mental experiences depend on the activity of sperate but interconnected cells

• two cells

  • Neurons

  • Glia

• brain contains approx. 86 billion individual neurons

Structure of a neuron

• neurons are similar to other cells of the body but have a distinctive shape

• shape goes to function of sending messages

• long extending branches

• spinal cord segment within the nerves are sensory and motor neurons

Types of neurons

Motor and sensory

Motor neurons

• responsible for motor information from CNSto the muscle to retract

• only sends go

• Soma in the spinal cord

• receives excitation from other neurons

• conducts impulses along its axon to a muscle

Sensory neurons

• Is specialised at one end to be highly sensitve to a particular type of stimulation

• brain can read electrical messages so the neuron changes the sensory information into neural impulses

• travels along the axons to travel up the spinal cord to the brain

• soma in the middle

• cluster is a ganglion

• transduction

Components of a neuron

Dendrites→Soma/cell body →. Axon

Dendrites

• branching fibres

• receive information through synaptic receptors

• dendritic spines that further branch out and increase the surface area of the dendrite

• the greater the surface area of the dendrite the more information it can receive

• information from lots of neurons and it combines the information

Soma/cell body

• contains the nucleus (DNA (genetic code), ribosomes (read genetic code than bring amino acids and creates a chain), endoplasmic reticulum (makes the protein from the amino acids), golgi apparatus (package for the protein to send it away)

• responsible for the metabolic work of the neuron

• constructs proteins

• covered with synapses on its surface in many neurons (also bringing in information)

Axon

thin fibre of a neuron responsible for transmitting nerve impulses toward other neurons, organs or muscles

has the axon hillock, presynaptic terminals, vesicles

Axon hillock

• connects the axon to the cell body

• site of summation of input occurs to initiate action along the axon

Presynaptic terminals

at the end points of an axon release chemicals to communicate with other neurons

Vesicles

• tiny spherical packets located in the presynaptic terminal where neurotransmitters are held for release

• Myelin sheath

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• Microtubules and neurofilaments (scaffolding) provide structure to the axon and assist in transport

Myelin sheath

• insulating material that contains interruptions in the sheath known as nodes of Ranvier (allow to boost the message because it leaks a little bit)

Direction of travel reference to the CNS

• Afferent axon

  • refers to bringing information into a structure

  • sensory

• Efferent

  • refers to carrying information away from a structure

  • motor

• Interneurons are those whose dendrites and axons are completely contained within a single structure

Glia

helper cells

Types of glia

• Astrocytes

• Microglia

• Radial glia

• Oligodendrocytes multiple and Schwann cells

Astrocytes

• help synchronise the activity of the axon by wrapping around the presynaptic terminal and taking up chemicals released by the axon

• provide glycogen to neurons by acting on blood vessels

• apart of that blood barrier

• permeable to potassium

  • overactivation of cells is epilepsy

• Encourages Neuroplasticity

  • maladaptive change

Microglia

remove waste material, viruses, fungi and and unnecessary neurons from the brain

Radial glia

guide the migration of neurons and the growth of their axons and dendrites

Oligodendrocytes multiple and Schwann cells one

build the myelin sheath that surrounds and insulates certain vertebrate axons