Theme 1: Cellular and anatomical
structure of Nervous system;
Neurophysiology
• To understand the relationship between histology and function of neurons and their
supporting cells the neuroglia
• To be able to explain how membrane- and action potentials are established in
unmyelinated and myelinated axons
• To be able to explain how neurons communicate with each other
• To understand how the ventricular system has developed and functions, and the way
cerebrospinal fluid is formed and reabsorbed
• To be able to explain the conduction of an action potential and to apply this
knowledge to the communication within the brain
General terms
Central nervous system: neuronal tissue encased by bones of skull and spinal column
Peripheral nervous system: nerves and most of the sensory organs located outside skull and
spinal column.
- Connects the CNS to the organs, limbs and skin.
- Carries sensory and motor information to and from the CNS.
- Allows the brain and spinal cord to receive and send information to other areas of
the body
- Regulates involuntary body functions like heartbeat and breathing
Motor nerve: A nerve that conveys neural activity to muscle tissue and causes it to contract.
Sensory nerve: A nerve that conveys sensory information from the periphery into the central
nervous system.
Somatic nervous system: The part of the peripheral nervous system that provides neural
connections to the skeletal musculature. The nerves that make up the somatic nervous
system form two anatomical groups: the cranial nerves and the spinal nerves.
• Cranial nerve: A nerve that is connected directly to the brain.
• Spinal nerve: Also called somatic nerve. A nerve that emerges from the spinal cord.
Autonomic nervous system: The part of the peripheral nervous system that supplies neural
connections to glands and to smooth muscles of internal organs
,Autonomic ganglia: Collections of nerve cell bodies, belonging to the autonomic division of
the peripheral nervous system, that are found in various locations and innervate the major
organs.
• Preganglionic: literally, “before the ganglion.” Referring to neurons in the autonomic
nervous system that run from the central nervous system to the autonomic ganglia.
• Postganglionic: literally, “after the ganglion.” Referring to neurons in the autonomic
nervous system that run from the autonomic ganglia to various targets in the body.
To understand the relationship between histology and function of
neurons and their supporting cells the neuroglia
In all types of neurons, the dendrites are in the input zone. In multipolar and bipolar cells,
the cell body also receives synapses and so is also part of the input zone.
• Unipolar
o Cell body + axon + myelin sheet
o Transmit information from the brain to the
spinal cord
o A nerve cell with a single branch that leaves
the cell body and then extends in two
directions; one end is the receptive pole, the
other end the output zone.
• Bipolar
o Sensory receptor + cell body + axon
o Have a single dendrite at one end of the cell and a single axon at the other
end. Common in sensory systems
o Neurons in general sensory neurons activated by sensory input from the
environment and signal them to the brain
• Pseudo-unipolar
o Sensory receptor + Cell body is on stolk
▪ No myelin sheets
o Neurons in general sensory neurons activated by sensory input from the
environment and signal them to the brain
• Multipolar
o Have many dendrites + cell body + single myelinated axon
o they are the most common type of neuron
o Function: the motor neurons of the spinal cord that connect to muscles,
glands and organs throughout the body. Transmit impulses from the spinal
cord to skeletal and smooth muscle → directly control all of our muscles
movements
▪ 2 types of motor neurons: those that travel from spinal cord to muscle
– lower motor neurons; those that travel between brain and spinal
cord – upper motor neurons
,Axon terminal/ terminal button: The
end of an axon or axon collateral,
which forms a synapse on a neuron or
other target cell.
Axon hillock/Integration zone: The
part of the neuron that initiates nerve
electrical activity.
The biggest difference between axons
and dendrites is that axons have myelin
sheeting and dendrites don’t. Axons
are myelated to prevent one axon from
affecting the other.
To be able to explain how neurons communicate with each other
A synapse has 3 critical components:
1. The presynaptic membrane of the axon terminal of the presynaptic neuron
2. The synaptic cleft, a gap of about 20–40 nanometers (nm) that separates the
presynaptic and postsynaptic neurons
3. The specialized postsynaptic membrane on the surface of the dendrite or cell body
of the postsynaptic neuron
Axon collaterals: most neurons have one axon, but axon can divide into several branches. By
this, 1 axon can contact different multiple neurons allowing the neuron to influence (or
innervate) a number of postsynaptic cells
, Neural plasticity: Neural contact is not
static, configuration of synapses as
dendrites change shape, synapses
come and go. The ability of the
nervous system to change in response
to experience or the environment.
Most axons divide and branch many
times. Neurons receivers thus
information from many other neurons,
which receive input again from other
neurons.
Axonal transport is the transportation
of materials from cell body to distant
regions and from axon terminals back
to the cell body. It can happen in two
directions:
• Anterograde transport:
transport from the soma to the
distal axon
• Retrograde transport:
transport from distal regions
back to the soma
Supporting cells
Central Nervous System
In the CNS are three main groups of supporting cells: neuroglia (astrocytes), microglia and
oligodendrocytes. Unlike neurons, glial cells continue to divide throughout life, and
consequently they form many of the types of tumors that may arise in the brain. Some glial
cells, especially astrocytes, respond to brain injury by changing in size—that is, by swelling.
This edema damages neurons and is responsible for many symptoms of brain injuries.
• Astrocytes: located close to synapses & can make neuronal contact, supply neurons
with glucose
o Phagocytosis
o Nourishment, can store glucose
o Nerve glue, involved in formation new synapses and pruning surplus synapses
▪ Provide stability of synapses and help with formation of new synapses
o Control composition neuronal extracellular fluid
▪ Role in epilepsy, changed neuronal excitability
o Surround synapses – limited dispersion neurotransmitter
▪ Receive synapses directly from neurons and surround and monitor the
activity of nearby neuronal synapses
o Communication between neurons
o Swelling in case of brain damage (edema)
