Section 1 Functions amp Divisions of the Nervous System pp 386387 This is your brain The Nervous System And this is your brain IN ANATOMY Or better yet The Nervous System Functions of the Nervous System ID: 605045
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Ch 11: Nervous System & Nervous Tissue
Section 1 – Functions & Divisions of the Nervous System (pp. 386-387)Slide2
This is your brain…The Nervous SystemSlide3
And this is your brain – IN ANATOMY!!
Or better yet…
The Nervous SystemSlide4
Functions of the Nervous System 1) Sensory input
- information about internal/external
changes
gathered by
sensory receptors 2)
Integration
- interpretation of sensory input 3) Motor output - activation of effector organs (muscles, glands, etc.) - production of response
The Nervous SystemSlide5
Divisions of the Nervous System 1) Central nervous system (
CNS
)
-
brain & spinal cord
-
integration & command center The Nervous SystemSlide6
Divisions of the Nervous System 2) Peripheral nervous system (PNS
)
-
spinal
&
cranial nerves - carry messages to & from
CNS
Functional divisions of PNS: a) Sensory (afferent) division - carry information to the CNS from effector organs
b) Motor (efferent) division
-
carry
information
away
from CNS to
effector organs
The Nervous SystemSlide7
Divisions of the Nervous System 2) Peripheral nervous system (PNS) - spinal & cranial nerves
- carry messages to & from CNS
Motor
divisions of PNS:
a) Somatic (
voluntary
) nervous system - provides conscious control of skeletal muscles b) Autonomic (involuntary) nervous system - regulates smooth muscle, cardiac muscle, & glands
- divided into sympathetic & parasympathetic
systems
The Nervous SystemSlide8
Ch 11: Nervous System & Nervous Tissue
Section 2 – Histology of Nervous Tissue
(pp. 388-395)Slide9
Neurons (aka “Nerve Cells”) - Fundamental units of the
nervous system
- Cells that are capable of carrying
electrical signals
Special characteristics
:
1) long-lived (capable of living
100
years or more)
2) amitotic…cannot divide (with a few exceptions) 3) high metabolic rate (require continuous O2 & sugar supply) 4) plasma membrane designed for electrical signalingNeuronsSlide10
Typical neurons have 4 distinct regions: 1) Dendrites - Receive
&
respond
to signals from other neurons
- Use special
receptors
to respond to neurotransmitters - Deliver electrical
signal
to cell body
2) Cell body (aka “perikaryon” or “soma”) - Neuron’s integration center - Combines all incoming electrical signals - If incoming signals are positive enough, cell body allows signal to continue to axon
NeuronsSlide11
Typical neurons have 4 distinct regions: 3) Axon - Long, thin fiber
…makes neurons
longest
cells in body
- Carries
electrical
signal away from cell body - Allows signals to be carried
large
distances
- Multiple axons are bundled together to form “nerves” 4) Synaptic terminals - Endings of the axons - Contain neurotransmitters (NTMs) - Release NTMs to other neurons, glands
, or muscles
NeuronsSlide12
Neuroglia - Literally means “nerve glue”
- Cells that
support
the
function
of the nervous system
- Are not capable of carrying electrical impulsesExamples found only in Central
Nervous System
:
1) Astrocytes - Abundant, star-shaped cells that brace neurons - Control chemical environment of brain - Form barrier between capillaries &
neurons
Other Cells of Nervous SystemSlide13
Other Cells of Nervous System
AstrocyteSlide14
2) Microglia - Spider-like phagocytes
that dispose of
debris
3)
Ependymal
cells
- Line
cavities
of the brain & spinal cord - Circulate cerebrospinal fluid
Other Cells of Nervous SystemSlide15
4) Oligodendrocytes - Produce myelin sheath
around
nerve
fibers
in
central nervous system
*Myelin
sheath
- Acts like insulation - Prevents short circuitsOther Cells of Nervous SystemSlide16
Other Cells of Nervous SystemSlide17
Examples of Neuroglia in the Peripheral Nervous System: 1)
Satellite
cells
- protect neuron
cell
bodies in PNS 2)
Schwann cells
-
form myelin sheath around axons in PNS - vital to regeneration of damaged peripheral nervesOther Cells of Nervous SystemSlide18
More on Myelin Sheath of PNS: - formed in a “Jelly roll”-like fashion
-
insulates
the axons
- enhances
& increases speed of the electrical signal
Nodes of
Ranvier
- Gaps in the myelin sheath formed by spaces between Schwann cellsOther Cells of Nervous SystemSlide19
Multipolar Neurons - Characterized by many
extensions
from cell body
- All of the
motor
neurons
Structural Classification of NeuronsSlide20
Bipolar Neurons - Consist of only one dendrite & one
axon
- Found only in
nose
(
smell
) & eyes (
vision)
Structural Classification of NeuronsSlide21
Unipolar Neurons - Consist of a single,
short
extension
leaving the cell body
- All
sensory neurons
Structural Classification of NeuronsSlide22
Ch 11: Nervous System & Nervous Tissue
Section 3 – Neuron Function
& Action Potentials
(pp. 399-404)Slide23
Information Processing Requires 4 Basic Operations:Determine the type of stimulus
- Distinguished by
various
wiring
patterns in the brainDetermine the
intensity
of the stimulus
- Either by the number of times a single neuron “fires” or the total number of neurons “firing” at onceIntegrate information from many different sources
Initiate & direct a response
Information ProcessingSlide24
Basic Neuron Function: - Neurons are highly irritable (responsive to stimuli
)
- Send
signals
over long distances by generating “
action potentials
” Action Potential
- “nerve impulse
”
- a brief change in the electrical charges found on either side of the nerve cell membrane - travels from the cell body to the end of the axon - always the same strength regardless of stimulus
Neuron FunctionSlide25
More on Action Potential: - created by the movement of positively charged
sodium
&
potassium
ions across the cell membrane of the
axon
- as charged particles move, they create electrical
impulses
- considered “
all-or-none phenomenon”…either happen completely or not at allThreshold stimulus - minimum stimulus required to create an action potential
Neuron FunctionSlide26
Conduction velocity: - the speed
action potentials travel
- vary widely…some
faster
than others
- fastest occur at 100
meters/sec or more!
Rate determined by…
1) Axon diameter - larger diameter = faster conduction velocities 2) Degree of myelination - more myelin = faster conduction velocitiesNeuron FunctionSlide27
Ch 11: Nervous System & Nervous Tissue
Section 4 – The Synapse & Neurotransmitters (pp. 406-421)Slide28
Synapses: - junctions
that
regulate
information between two neurons
- also found between
neurons & effector cells/organs
Presynaptic
neuron
- conduct impulses toward synapsePostsynaptic neuron - conduct impulses away from synapseThe SynapseSlide29
Two most common types of synapses:
1)
Axodendritic
synapse
- between the axon of one neuron & the
dendrite of another
2) Axosomatic synapse - between the axon of one neuron & the cell body of another*These may be either “electrical” or “chemical” synapses…
Types of Synapses
Animation
:
SynapsesSlide30
Electrical Synapses: - not as common as
chemical synapses
- neurons are
physically
connected by
gap junctions
-
electrical
signal travels directly through the gap junction - very rapid; utilized in very fast events…reflexesElectrical SynapsesSlide31
Chemical Synapses: - specialized for releasing
&
receiving
neurotransmitters
Typically composed of two parts: 1) Axon
terminal
- found on presynaptic neuron - contains synaptic vesicles w/ neurotransmitters 2) Receptor region - found on postsynaptic neuron - has special receptors that
receive neurotransmitters
Chemical SynapsesSlide32
Synaptic Cleft: - fluid
-filled space between pre- & post-synaptic neurons
- prevents
nerve impulses
from
directly passing from one neuron to the next
Synaptic CleftSlide33
Transmission of Electrical Impulse Between Neurons: - Electrical signal reaches end of axon
-
Neurotransmitters
are
released
from
synaptic terminals
- Neurotransmitters diffuse
through synaptic
cleft - Neurotransmitters bind to receptor sites on adjacent dendritesSynaptic CleftAnimation: NeurotransmittersSlide34
Terminating effects of neurotransmitters: - occurs within a few
milliseconds of NTM
release
- happens as a result of either the…
1) NTMs being broken
down by enzymes
2) NTMs being reabsorbed into the axon terminal 3) NTMs diffusing away from synaptic cleftSynaptic CleftSlide35
Types of neurotransmitters: - most neurons make 2
or
more
NTMs
- the number of
times per second that a neuron “
fires” determines which NTM is actually
released
- over 50 different NTMs have been identifiedNeurotransmittersSlide36
Specific Neurotransmitters
Neurotransmitters & Functions
:
1)
Acetylcholine
-
Activate skeletal muscles
2) Dopamine
-
Important in general movement 3) Epinephrine - Activates organs of sympathetic nervous system 4) Serotonin - Influences mood (“
mellow”) & sleep
5)
Endorphins
-
Influences
mood
(“feel good”), reduces
pain 6)
Nitric
oxide
-
Important in forming
memoriesSlide37
Ch 11: Nervous System & Nervous Tissue
Section 5 – Neural Integration…Circuits
(pp. 422-423)Slide38
Organization of Neurons
Types of circuits
:
1)
Diverging
circuits
- one incoming nerve fiber stimulates
multiple fibers
- often acts as an “amplifying” circuit Ex = single neuron in brain can activate hundreds of motor neurons in spinal cord and ultimately thousands of skeletal muscle fibersSlide39
Organization of Neurons
Types of circuits
:
2)
Converging
circuits
- multiple nerve fibers in different areas combine signals into
one fiber
- often have a “concentrating” effect; strong stimulation or strong inhibition Ex = seeing a baby smile, smelling baby powder, hearing baby laugh all combine to trigger “warm/fuzzy” feelings in parentsSlide40
Organization of Neurons
Types of circuits
:
3)
Reverberating
(oscillating) circuits
- chain of neurons arranged in a loop
- results in signal that is sent through the circuit over
&
over in a rhythmic pattern Ex = sleep-wake cycles, breathing, arms swinging when walkingSlide41
Organization of Neurons
Processing information in the nervous system
:
1)
Serial
processing
- input travels along one
path to a
specific
destination - works in all-or-none manner producing specific response Ex = spinal reflexesSlide42
Reflex - Simplest behavior -
Involuntary
movement of body part in
response
to stimulus
- Occur without involving the
conscious portions of the brain - Signal sent to
spinal
cord
& immediately back to source - Usually help keep you from being hurtNeural Pathways Direct BehaviorSlide43
Organization of Neurons
Processing information in the nervous system
:
2)
Parallel
processing
- input travels along several
pathways
- one
stimulus promotes many responses - crucial for higher-level mental functioning Ex = a smell usually isn’t processed as just an odor; also usually triggers memories of experiences associated w/ the
smellSlide44
Ch 11: Nervous System & Nervous Tissue
Section 6 – Homeostatic Imbalances
(pp. 422-423)Slide45
Homeostatic Imbalances
Multiple
Sclerosis
(MS)
:
-
autoimmune disease; mainly affects young adults
-
myelin
sheaths in the CNS become destroyed - sheaths turn into nonfunctional, hardened lesions - leads to short-circuiting of nerve impulses - eventually impulse conduction ceases Symptoms - visual/speech
disturbances, weakness, loss of muscle control, & loss of bladder
controlSlide46
Homeostatic Imbalances
Neuroblastoma
:
-
malignant
tumor that occurs in the
peripheral nervous system of childrenRabies
:
-
viral infection of nervous system - transmitted through bites from infected animals - causes inflammation of brain, delirium, & deathSlide47
Homeostatic Imbalances
Shingles
:
- viral infection of the
sensory
neurons found in the
skin - scaly, painful blisters
; similar to chickenpox
but w/ pain
- seen mostly in adults over 50 years old