Transcript Nervous System & Endocrine System

The Nervous System
Anatomy & Physiology 2
Organization of the nervous
System
• Central nervous system
(CNS) – the brain and
spinal cord
– Interprets incoming sensory
information and issues
instructions based on past
experiences and current
conditions
• Peripheral nervous system
(PNS) – the nerves that
extend from the brain and
spinal cord
– Link and carry all the
information to the CNS
Organization of the nervous
System
• The PNS is divided
into 2 subdivisions
– Sensory division:
keeps the CNS
informed of events
going on both inside
and outside the body
– Motor division:
activates muscles and
glands
Organization of the nervous
System
• The motor division
has two subdivisions:
– Somatic nervous
system: voluntary
controls the body
– Autonomic nervous
system: regulates
involuntary activities
Nervous Tissue
• Nerve Cells
– The main part of the nervous
system
– The human body contains
numerous nerve cells
– Nerve cells are called neurons
– Neurons are similar to
electrical wires and carry
messages along long, thin
strands
– They can reach up to a meter
in length
– A nerve is a bunch of neurons
bunched together
Nervous Tissue
• Nerve Cells
– Have all the organelles that
other cells have, but look
very different
– Dendrites receive
information from other
neurons
– Axons sends information to
other neurons
– A synapse is a connection
between 2 neurons
Nervous Tissue
• Nerve fibers are
covered with a
whitish, fatty material
called myelin
• When the myelin
completely cover the
nerve cells it called the
myelin sheath
• It’s function is to
make nerve cells faster
Nervous Tissue
• Not all cells are
mylinated
• In the brain there are
dense collections of
myelinated regions
called white matter
and dense collections
of unmyelinated
regions called gray
matter
Pathway of Messages
• Information is sent on 2
different pathways – it is not the
same pathway
• For example: if you touch
something hot the information
is sent to your brain on one
pathway and the result of
touching something hot (it
burns) is sent on another
pathway
• Nerve cells do not touch one
another – the information skips
across the synapse
Nervous System Parts
•
• Nerve cells are important
parts of the nervous
system, but others include:
• The brain
– The organ that sends, receives
and processes information
from all body parts
– It is made of billons of neurons
• Spinal cord
– Carries information from the
brain to the body
– All information from the body
is first sent to the spinal cord,
then to the brain
The Brain
The Brain
• Parts:
–
–
–
–
Cerebrum
Diencephalon (interbrain)
Brain stem
Cerebellum
The Brain
• Cerebrum
– The cerebrum has two
cerebral hemispheres
– Has elevated ridges of
tissue called gyri and
shallow grooves called sulci
which provide landmarks
– Controls thought, reason,
senses, speech, memory,
consciousness,
interpretation of sensation
and voluntary movement
The Brain
• Cerebrum
– Occipital lobe – visual area
– Temporal lobe – auditory
area
– primary motor area –
controls movement
– Broca’s area – involved in
speech
– Frontal lobe – intellectual
reasoning and socially
acceptable behavior
The Brain
• Cerebrum
– Corpus callosum –
connects the cerebral
hemispheres
• Diencephalon
– Sits atop the brain stem
– Contains the thalamus,
hypothalamus and
epithalamus
The Brain
• Diencephalon
– Thalamus: quickly
recognizes pleasant or
unpleasant sensations
– Hypothalamus:
controls body temp,
water balance and
metabolism; also
drives emotions
– Epithalamus: important
to the endocrine system
The Brain
• Brain stem
– About the size of a human
thumb
– 3 parts midbrain, pons,
medulla oblongata
– Midbrain: controls and
directs incoming impulses
– Pons: helps control
breathing
– Medulla oblongata: controls
heart rate, blood pressue,
breathing, swallowing and
digestion
The Brain
• Cerebellum
– Has two hemispheres
– Large cauliflower-like
structure under the occipital
lobe
– Helps make movement
smooth and not robot-like
and controls balance
Nervous System Parts
• Spinal Cord
– About 17 inches long
– Can be thought of as the power
lines from the power plant
– Spinal cord is protected by
vertebrae (series of bones)
• Is a two-way passage system
• All the nerves that extend from
the spinal cord are called body
nerves
Reflexes
• Reflexes are reactions that are
quick and protective
• During a reflex the message
does not reach the brain first,
but reacts, then tells the brain
the information
• How a reflex works
– If you put your hand on a hot
stove the information is sent to
your spinal cord through one
pathway, through another
pathway information is sent
back to your hand to move,
along yet another pathway
information is sent to your
brain and finally through
another pathway information is
sent to your hand that it hurts