ANAT 261 Lecture Notes - Epineurium, Autoimmune Disease, Morphine

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Naveen Sooknanan McGill Fall 2011
1
Nervous System:
The nervous system is made up of cells called neurons. Working together, neurons are
responsible for all of your thought and consciousness
Structurally speaking, neurons are made of the same components as other cells, but their
complex connections and active nature give us a sense of self
A very famous Canadian neurosurgeon names Walter Graves Penfield is actually responsible for
the mapping the brain using a technique now called the “Montreal procedure”
He was an American born Canadian neurosurgeon
He was responsible for figuring out how epileptic seizures worked
The patient was given a local anasthetic in the head, and the skull was cut open, exposing
the brain
o The brain was probed in different areas while the patient was awake
This is possible because the brain itself contains no pain receptors
o The patient said he smelled burnt toast before his/her seizure, which allowed Dr.
Penfield to examine and locate the region of the brain causing the seizures
The adult brain is comprised of around 10 billion neurons (a 21 year old). The number begins to
diminish as you age and these cells do NOT regenerate (i.e. you’re born with a certain amount
and that’s it). Nerve tissue is distributes throughout the body in an integrated communication
network
Classification of nervous tissue:
o Anatomically:
CNS: brain, cerebellum, spinal cord
Either grey (cell bodies) or white matter (axons)
PNS: Nerve fiber, nerve ganglia
o Histologically:
Neurons (nerve cells)
Neuroglial
Glial cells are the brain’s equivalent of CT; involved in support,
neuron protection, defence and nutrition
Glial cells also define the blood brain barrier
o Gray matter
Cell bodies of neurons, neuroglia
o White matter:
Neuronal processes (axons) and neuroglia
White matter gets it color from an axon coating made of myelin (which is
white)
The function of nerve tissue is to:
Detect, analyze, integrate and transmit information generated by sensory stimuli (heat,
light, etc.) and by chemical and mechanical changes in the external of internal milieu
o E.g. you touch a hot stove, you realize it hurts
o Done by afferent neurons coming into the CNS from the sensory inputs
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Naveen Sooknanan McGill Fall 2011
2
To organize and coordinate, directly or indirectly, most functions of the body, especially
the motor, visceral, endocrine and mental activities
o Done by efferent neurons sent out of the CNS
Neurons are capable of responding to stimuli by altering electrical potential differences between
their inner and outer surfaces
The same properties can be found in muscle and glandular cells
Neurons react promptly to stimuli; modification of electrical signals may be restricted to the
place that it received the stimulus or may be propagated as a nerve impulse (action potential) to
transmit to other neurons or to muscle/glands
E.g. the neuromuscular end plate located on the center of every striated muscle fiber
o This marks the connection (synapse) between a muscle fiber and the axon of a
nerve (motor neuron)
The nervous system can be divided into the central nervous system and the peripheral nervous
system
The peripheral nervous system (PNS) brings in
afferent neurons coming from receptors all over the
body (skin, eyes, taste buds, nose, ears, muscle
joints)
o They form synapses in the spinal cord where
they enter the central nervous system (CNS)
The central nervous system includes the brain and
spinal cord, which are the major information
processing units
o This is where thinking and conscious actions,
as well as subconscious actions, manifest
themselves
o The CNS sends out afferents neurons which outputs corresponding to the inputs
from the PNS
o These outputs travel to where they came from and give the body instructions on
how to respond to stimuli
They innervate mainly
muscle cells (smooth and
striated) as well as glands
All neurons have 2 processes: a number of
dendrites and a single axon
The perikaryon is the cell body of the
neuron, located within the CNS, where
the nucleus is
o This part of the neuron
resembles a typical cell,
containing organelles such as the
ER and the mitochondria
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