Download Nervous System - Wando High School

 Neurons
are masses of nerve cells that
transmit information to other nerves, tissues
or cells (nerve impulses). Consists of
1. cell body- contains the nucleus and two
extensions.
 2. dendrites- shorter, more numerous, receive
information. (carry to the cell body)
 3. Axons- single, long
fiber which conducts
impulses away from
the cell body.

 Central
nervous
system (CNS)

Consists of the brain
and spinal cord
 Peripheral
Nervous
System (PNS)


Includes 31 pairs of
spinal nerves
Includes 12 pairs of
cranial nerves
 1.
Sensory Function- gathers information
within and around the body, sends nerve
impulses to the CNS.
 2.
Integrative function- information is
interpreted, to create sensations, create
thoughts, add to memory, make decisions,
etc.
 3.
Motor Function- responds to signals
(impulses). Signals go from the CNS to
effectors (muscles or glands).
 Integration
center of the body
Constant input from sensory organs
 Constant learning
 Memory of response or outcome
Huge collection of myelinated and unmyelinated
neurons

Divided into lobes: different sensory and motor
functions are controlled by different lobes.
 Three
major parts:

Cerebrum: largest, sensory and motor functions,
higher mental function (memory, reasoning)

Cerebellum- coordinate voluntary muscles

Brain stem- regulate visceral functions
 Sulci


and gyri are along the surface
Sulci are shallow grooves
Gyri are ridges or bumps
Fissures are deep grooves
 Major
sensory lobe
 Hard drive/memory
 Speech understanding-Broca’s area
 Recognition of people, places, items, events,
etc.
 Memory of outcomes
 taste
 Occipital

Receives input from the eyes and sends it to the
parietal lobe for interpretation
 Temporal


lobe:
lobe:
receives input from the ears and sends it to the
parietal lobe for interpretation
memory processing –short term
 Cerebellum:



fine motor coordination
balance and posture
*increases its control with practice
 1.



auditory and visual reflexes
eye movement
fluidity of movement
 2.





pons:
integration center for cerebellum and cerebral
communication
respiratory center
 3.

midbrain:
medulla oblongata:
involuntary muscle control
autonomic reflexes
respiratory/cardiovascular center
vomiting, coughing, hiccupping, sneezing,
swallowing
 The




neuron:
Large, complex cells
Longevity: long life
Lack centrioles- cannot perform mitosis
Classified by structure and function
 Cell
body: contains the nucleus and all other
cellular organelles along with the bulk of
cytoplasm
 Dendrites:
receptive or input regions that
provide enormous surface area for receiving
signals from receptor organs/glands
 Axon:
in each neuron, there is only one! It
can be very long or so short it seems
nonexistent. Conduction component that
generates and propagates nerve impulses
away from the cell body.
 Myelin:
fatty covering that insulates the
axon. Gaps between myelin are called nodes
of Ranvier.


2-4 mph without myelin
250 mph with myelin
 Axon
terminal: end of the axon where
neurotransmitters are stored and released.
 Sensory:
receive impulses and transmit to
the brain
-afferent neurons
 Motor:
receive impulses from the brain and
send them to effector organs
-efferent neurons
 Interneuron:
communicate between motor
and sensory along the spinal cord
-association neurons
 Multipolar:
3 or more attachments to the cell
body
*** most common structure
 Bipolar:
2 attachments to the cell body
*** rare- special senses
 Unipolar:
1 attachment to the cell body
*** rare- PNS sensations
 Supportive
tissue of the nervous system
(more numerous than neurons) 5 types:





Microglial cells
Oligodendrites
Astrocytes
Ependymal cells
Schwann cells
 Ependymal:
In CNS
Epithelial cells
 Produce and form a
barrier between
neurons and CSF

 Oligodendrocyte:
in CNS


Branching cells
Wrap their branches
around the neuron’s
axon insulating it
with myelin
 Astrocyte



–in CNS
Small, branching
cell
Most abundant
neuroglia
Braces neurons to
capillariesexchanges between
neurons and
capillaries
 Microglia-
in CNS
Thorny cells
 Monitors neuron
health

 Satellite
Cell: in
 Schwann
PNS
PNS
Looks like moons or
satellites
 Job is still unknown
but thought to act
as astrocytes



Cell: in
Has branching
extensions like
oligodendrocytes
Wraps its branches
around PNS neuron
axons to insulate
them with myelin
 Nerve
impulse: propagation of an impulse
from dendrite to axon terminal
 Resting
membrane potential: high
concentration of sodium ions outside the
membrane and a high concentration of
potassium inside the cell.
 Na/K
channel vs Na/K
pump: channels are
open and allow ions to
flow freely while pumps
turn off and on to reset
the membrane potential
Depolarization:
neuron membrane is more
permeable to sodium ions.
* Na+ flows into the neuron
Repolarization: neuron membrane is
more permeable to potassium ions.
*K+ flows out of the neuron
Hyperpolarization: too much
potassium leaves making the neuron
too negative
~ -90mV
After hyperpolarization,sodium/potassium pumps reset the
resting membrane potential.