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27 Cards in this Set

  • Front
  • Back
What is the Central Nervous System (CNS)?
Brain and spinal cord
What is the Peripheral Nervous System (PNS)?
Nerve fibres and ganglia (clusters of nerve cell bodies outside the CNS)
What are the four primary tissue types?
Connective tissue
Muscle tissue
Nervous tissue
- Central nervous system (CNS)
- Peripheral nervous system (PNS)
What are the two functional divisions of the nervous system?
Somatic parts of CNS and PNS. Excludes innervation of viscera, smooth muscle and glands. (Gr soma = body)

Automomic parts of CNS and PNS
- Efferent (away from CNS) - smooth muscle, heart, glands
- Afferent (towards CNS) - pain and autonomic reflexes
What are the 3 components found in all nervous tissue?
Nerve cells (neurons)
Supporting cells (glial or neuroglia)
Blood vessels
How many neurons are in the human cortex?
30-(100?) billion
What are neurons able to do?
Receive information - signals from external or internal sources
Process and integrate these signals
Conduct nerve impulses (action potentials) to designated target tissues such as other neurons, muscles and glands.
What does a typical neuron consist of?
Cell body (soma, perikaryon)
One axon
What are the different types of neurons? Describe.
Mulipolar - more than two processes (most common)
- common in CNS and ANS

Bipolar - one dendrite and one axon
- olfactory epithelium

Pseudo unipolar - single process that branches close to cell body
- dorsal root ganglia
What is the functional characterisation of neurons?
Motor (efferent) neurons - control effector organs such as muscle fibres and exocrine and endocrine glands

Sensory (afferent) neurons - receive sesory stimuli from the environment and from within the body

Interneurons - establish relationships between other neurons - form complex functional networks
What are features of the neuronal cell body?
Axon (Myelin) sheaths
- axons are mylinated by oligodendrocytes (CNS) and Schwann cells (PNS.

Nodes of Ranvier
- Allow for saltatory or discontinuous conduction
- conduction speed determined by
> diameter of axon
> thickness of myelin
- length segments 0.2-1.0mm
What do synapses do?
- from synapsis Gr. union
- responsible for unidirectional transmission of nerve impulses
Sites where contact occurs between neurons or between neurons and other effector cells (muscle, gland cells)
- most synapses transmit the nerve impulse by releasing neurotransmitters at the axon terminal - these induce the transfer of the nervous impulse
- more than 35 known neurotransmitters - most are amines, amino acids or small peptides
- synapses can excite or inhibit impulse transmission
What is the motor end plate?
The highly-excitable region of muscle fiber plasma membrane responsible for initiation of action potentials across the muscle's surface, ultimately causing the muscle to contract.
Describe neuroglia and where they are found.
- 10 times more abundant than neurons in mammalian brain
- surround neuron cell bodies and axonal and dendritic processes
- nervous tissue has no intercellular matrix - glial cells provide a microenvironment suitable for neuronal activity.

- astrocytes
- oligodendrocytes
- microglia

- Schwann cells
What are the kinds of neuroglia found in the CNS?
What are the kinds of neuroglia found in the PNS?
Schwann cells
Describe oligodendrocytes.
- produce the myelin sheath that surrounds axons in the CNS
- can provide myelin to more than one axon (sends out proceses which wrap multiple adjacent axons (50+))
- Cf Schwann cells 1:1
Describe astrocytes.
- star-shaped cells
- bind neurons to capillaries and to the pia mater - inntermost layer of the meninges

Fibrous astrocytes
- have few long processes
- found in white matter

Protoplasmic astrocytes
- have many short-branched processes
- found in grey matter

- form part of the blood- brain barrier
- influence neuronal survival and activity through release of metabolic substrates and neruoactive molecules (including vasoactive endothelins, opioid precursors called enkephalins)
- communicate with one another via gap junctions (nexus)
Describe Microglia.
- small elongated cells with short irregular processes
-phagocytic cells derived from bone marrow
- involved in inflammation and repair in CNS
- can act as antigen-presenting cells
- secrete neutral proteases, oxygen radicals and immunoregulatory cytokines
Descibe the organisation of white matter in CNS.
- white matter forms bulk of deep parts of the brain and the superficial parts of the spinal cord
- aggregates of grey matter such as the basal ganglia (caudate nucleus, putamen, globus pallidus, subthalamic nucleus, nucleus accumbens) and brain stem nuclei (red nucleus, substantia nigra, cranial nerve nuclei) are spread within the cerebral white matter
- The cerebellum is structured in a similar manner as the cerebrum, with a superficial mantle of cerebellar cortex, deep cerebellar white matter (called the "Arbor vitae") and aggregates of grey matter surrounded by deep cerebellar white matter (dentate nucleus, globose nucleus, emboliform nucleus, and fastigial nucleus).
- The fluid-filled cerebral ventricles (lateral ventricles, third ventricle, cerebral aqueduct, fourth ventricle) are also located deep within the cerebral white matter
Describe the layering of gray matter in CNS.
The standard areas of cortex (isocortex) is characterized as having six distinct layers. From outside inward:

1. Molecular layer
2. External granular layer
3. External pyramidal layer
4. Internal granular layer
5. Internal pyramidal layer
6. Multiform layer.

- input layer 4 - distribute apical and basal directions
What are the important parts of the cerebellum?
- folia of cerebellum (large mass of brain cells)
- white and gray matter of the cerebellum
- purkinje cell layer
What are the parts of the Purkinje cell layer?
- Purkinje cells
- Molecular layer (superficial)
- Granular layer (deep)
What is the architecture of the PNS?
- collections of nerve cell bodies outside the CNS
- also contain glial cells supported by connective tissue
- serve as relay stations - once nerve enters and another leaves each ganglion
- Sensory ganaglia - receive afferent impulses that then go to the CNS
- Autonomic ganglia - present in the autonomic nervous system (for control of smooth muscle, some glands, cardiac rhythm)
What is an example of autonomic glangion?
Autonomic ganglion gut
What is an example of parasympathetic ganglion?
Describe how peripheral nerves exist in the body.
- In the PNS, nerve fibres are grouped in bundles to form the nerves
- In addition to axons, Schwann cells and collagen fibrils, peripheral nerves consist of:
> Epineurium - external fibrous coat of dense CT
> Perineurium - surrounds bundles of nerve fibres
> Endoneurium - consists of delicate CT fibres produced by Schwann cells