nervous system Flashcards
(40 cards)
The central nervous system (CNS)
structural and functional centre of the entire nervous system. It consists of brain and spinal cord.
Integrates incoming sensory information
Evaluates the information
Initiates out going respond
The Peripheral Nervous System (PNS)
consists of the nerve tissue that lies in the periphery (outer regions) of the nervous system. These are cranial nerves and spinal nerves.
functional approach is divided Somatic and Autonomic.
Somatic system’s effector organ is voluntary (skeletal muscle)
Autonomic system’s effector organ is involuntary (smooth muscle and glands)
Two main type of cells made up the nervous system.
Neurons
Glia
neurons
excitable cells that conduct (transmits) the impulses that make possible all nervous system function (wiring of NS).
responsible for carrying information (or impulses) from one nerve to another. This nerve impulse also known as Action Potential (AP).
human brain 100 billion neurons
All neurons have a cell body
at least two processes - axon (only one branch) and dendrites (one, two or more branch).
Thread like extension often called nerve fibres.
Cell body (soma)
largest part. It has a nucleus, cytoplasm and various organelles such as mitochondria, ER and Golgi.
Dendrites
branched extensively like tiny trees
tiny branches receive information.
Axon
singe process of a neurone.
It emerges from cell body called axon hillock.
It can be long as 1m
has one or more side branches at the end.
The tip of axon have swellings called synaptic knobs or Synaptic button.
Each synaptic knob contains many small sacs (vesicles).
contains a chemical molecules called a neurotransmitter.
Glia
serves various roles in supporting the function of neurons.
Astrocytes
star shape glia
largest and most numerous glia in the CNS.
Astrocytes feed the neurons by picking up glucose from the blood.
They recycle chemical transmitters.
Influence the neuronal growth.
webs of astrocytes “feet” attached to brain’s blood capillaries, forms the blood brain barrier (BBB).
Encephalitis
inflammation of the brain
Most commonly caused by a viral infections.
The virus replicates outside the CNS and gains entry to the brain either via blood stream (BBB is not functioning).
Sometimes the virus also travel along the olfactory pathways.
Microglia
very small cells in the CNS.
stationary.
inflamed or degenerating brain tissue, they get enlarge and move about to get rid of cellular debris.
the immune cells of the brain tissue.
Ependymal cells
resemble epithelial cells.
line fluid filled cavities in the brain and spinal cord.
They are responsible for producing the fluid (cerebrospinal fluid).
They have cilia on their surface that help keep the fluid circulation.
Oligodendrocytes
smaller than astrocytes and have fewer processes.
Oligodendrocytes means “cell with few branches”.
Oligodendrocytes help hold nerve fibres together. produce the fatty myelin sheath around axons in the CNS.
Myelin sheath speed up nerve conduction
Multiple Sclerosis
chronic autoimmune disease of the CNS (the person’s own immune cells are responsible)
Immune cells target and destroy the myelin that wraps the nerves.
Loss of myelin reduces nerve conduction speed and
signals.
Signals are disturbed/abnormal.
The effects vary depending on which areas of the CNS are affected.
Sensory symptoms of Multiple Sclerosis
pain, tingling, numbness, visual and vestibular (balance) disturbances.
Motor effects - Multiple Sclerosis
difficulty moving, difficulty controlling movement, loss of accuracy of movement, weakening of muscles, tiredness.
Schwann cells
only found in the PNS. they have equivalent role with oligodendrocytes.
They also produce the myelin sheath.
Schwann cells also help debris removal and serve as guides for sprouts of regenerating axons after injury.
Meninges composed of three layers.
Dura Mater
Arachnoid Matter
Pia Mater
The Dura mater
strong fibrous tissue and serves as the outer layer of the meninges.
The Arachnoid matter
delicate, spider web like layer between.
The Pia Mater
delicate inner most layer of meninges. it is transparent and adhere to the brain tissue containing blood vessels.
Meningitis
(inflammation of meninges) is most often caused by bacteria or viruses.
Viral meningitis is self limiting with typically complete recovery.
Bacterial meningitis can have more serious effects.
Other pathogens such as fungi or parasite are also causes.
Bacterial meningitis is life threatening and less common than viral from.
Epidural Haematoma
Fracture of the skull can cause an accumulation of the blood outside the dura in the epidural space.
Cerebrospinal Fluid (CFS)
The CFS provides protection to brain and spinal cord.
present around the organs and within them.
When production of CFS exceeds resorption, hydrocephalus (also known as water in brain) results.
