Transcript Nervous System

Nervous System
By: Daniel Aleynick
What does it do?
 Responsibilities:
 Receive signal
 Interpret signal
 Send signal to do an action
The Nervous System control most of the
actions your body performs
Organization of Nervous System
 Nervous System:
 Central Nervous System (CNS): Consists of the brain and
spinal cord.
 Peripheral Nervous System (PNS): Are the nerves that
connect the CNS to the rest of the body
Information Processing
 A sensor (example: eye or skin) picks up a signal,
which is sends to the brain.
 The CNS processes the information, and sends
another signal to a specific effector (example: muscle)
 Effector proceeds with an action, such as a movement.
Neuron Structure
 Composed of:
 Cell Body
 Dendrites
 Axon
 Synaptic terminals
Supporting Cells
 Supporting cells are known as Glia.
 Astrocytes: provide support for neurons and control
concentration of ion levels
 The blood-brain barrier is formed by astrocytes creating a
very tightly controlled extracelluar chemical environment.
 Radial Glia: Form tracks that newly formed neurons can
travel. Also act as stems cells and can generated new
neurons.
Astrocytes
Surrporting Cells Con’t
 Schwann Cells: They make up the myelin sheath which
covers the axon of neurons. They act as an insulator
and increase the speed of the action potentials.
Resting Potential
 Membrane potential: The electrical difference between
the inside and outside of a cell.
 Resting potential: The membrane potential when a cell
is not transmitting a signal.
Membrane Potential
Gated Ion Channels
 There are three types ion channels:
 Stretch-gated ion channels
 Ligand-gated ion channels
 Voltage-gated ion channels
Voltage and Lignad Ion Channels
 Voltage-gated Ion Channels:
 Are found in axons and open and close when the
membrane potential changes.
 Stretch-gated Ion Channels:
 Open and close when the cells sense it is being stretch.
This occurs when the cell becomes mechanically
deformed.
Ligand-gated Ion Channels
 Ligand-gated Ion Channels: Are ion channels that open
and close when a specific molecule binds to the
channel. This molecule is usually a neurotransmitter.
Action Potential Useful Terms
 Hyperpolarization: An increase of the magnitude of
membrane potential by becoming more negative. This
is caused by K+ channels to opening up.
 Depolarization: A reducation in the magnitude of
membrane potential. This occurred when Na+ channels
open up.
 The changes in the membrane potential are called
graded potentials.
Production of Action Potentials
Action Potentials
 What is an action potential?
 An action potential is a stimulus strong enough to
produce depolarization past the threshold
 The threshold is the membrane potential limit that must
be reached for an action to occur. This is a all or
nothing event so nothing occur unless the limit is
reached. Once reached, the whole action takes place.
Conduction of Action Potentials
 An action potential starts in
the axon hillock.
 From there a cascade effect
takes place:
 As the axon hillock is
depolarized, it depolarizes a
neighboring region of axon
membrane.
 This next region than
depolarizes another nearby
region until the action
potential reaches the synaptic
terminals
Conduction Speed
 The faster the body can send out
signals, the faster one can react.
But how does the body increase
the speed of conduction?
 The axon of some neurons is
covered by Schwann cells. Since
these cells are made from lipids,
they are insulators. This causes
the electrical signal to jump over
the Schwann cells increase the
speed of the signal. This is
known as salutatory conduction.
Neuron Communication
 A neuron pass a signal to another neuron by chemical
synapses.
 Synaptic terminals produce a neurotransmitter and
package then in synaptic vesicles.
 The neurotransmitter move across the synaptic cleft and
active the ligand-gated ion channels on the nearby
neuron.
Neurotransmitters
 Acetylcholine:
 Is one of the most common neurotransmitters.
 Functional Class: Is an excitatory in vertebrate skeletal muscles
and an inhibitory at other sites.
 It is secreted by the CNS, PNS, and neuromuscular junctions.
Neurotransmitters Con’t
 The next group of
neurotransmitters are the
Biogenic Amines:
 Norepinephrine: Can be
an excitatory or inhibitory
and is produced in the
CNS and PNS
 Dopamine: Is both an
excitatory and inhibitory
and is produced in the
CNS and PNS
 Serotonin: Is generally a
inhibitory and is produced
by the CNS
Neurotransmitters Con’t
 Amino Acids can also be used as
neurotransmitters:
 Gamma Aminobutyric Acid: Is an
inhibitory and is made in the CNS
and neuromuscular junctions.
 Glycine: It is an inhibitory
neurotransmitter and is created in
the CNS
 Glutamate: Is an excitatory and is
produced in the CNS and
neuromuscular junction.
 Aspartate: An excitatory that is
made in the CNS
Neurotransmitters Final
 The last group of major neurotransmitters are
Neuropeptides:
 Substance P (not a creative name): is an excitatory that is
produce in both the CNS and PNS
 Met-enkephalin: Is generally an inhibitory that is made in
the CNS
Gases as Neurotransmitters
 Gases can be dissolved in fluids of the body and used
as neurotransmitters as well.
 Common examples are:
 NO and CO
Regions of the Nervous System
 The peripheral nervous
system is made up of all
the nerves connect the
brain and spine to the rest
of the body
 Cranial nerves extend from
the brain and spread to
organs of the head and
upper body
 Spinal Nerves originate in
the spinal cord and extend
to parts of the body below
the head.
PNS
 The PNS can be divided into two functional
components:
 The Somatic Nervous System (SNS)
 The Autonomic Nervous System (ANS)
 The Autonomic Nervous System can then be divided
further into 3 more division
 Sympathetic division
 Parasympathetic division
 Enteric division
Somatic Nervous System
 Is considered voluntary because it is subject to
conscious control.
 Sends signals to and from the skeletal muscles of the
body.
ANS: Sympathetic
 The sympathetic division deals with arousal and energy
generation of the body
 The “Fight or Flight” response:
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Digestions stops
Energy production increases
Adrenaline is released
Faster Heart Rate
Adrenaline RUSH
ANS: Parasympathetic
 Self-maintenance functions known as “Rest and
Digest”
 Digetionenchanced
 Heart Rated Slowed
 Glycogen production
Resting and Digesting
ANS: Enteric Division
 Is a network of neurons
in the digestive tract,
pancreas and
gallbladder.
 They control the
secretions and smooth
muscle activities of the
body, such as peristalsis,
the uncontrolled
movement of food
through the body.
Brain Structure
 In adults the brain
consists of 5
structures:
 Cerebrum
 Dienceohalon
 Midbrain
 Cerebellum
 Medulla Oblongata
Cerebrum
 Is divided into two different regions
 The Right Cerebral Hemisphere
 The Left Cerebral Hemisphere
 Each Hemisphere has an other cover of gray brain matter
and an inner region, the cerebral cortex, that is white brain
matter.
 Basal Nuclei are groups of neurons in the cerebrum that are
centers for planning and learning movement
 A think band of axons known as the corpus callosum always
the right and left hemisphere to communicate.
Diencephalon
 Is divided into 3 regions:
 The Epithalamus
 The Thalamus
 The Hypothalamus
 The Epithalamus consists of the pineal gland and choroid
plexus that produces cerebrospinal fluid.
 The Thalamus is the sensory center. All incoming
information from sense is sorted here
 The Hypothalamus produced vital hormones and is the
body’s thermostat, control temperature as well as hunger,
thirst, and other survival mechanisms.
Midbrain
 Acts as the rely stations for all auditory and visual
information that brain receives.
 It also controls the eyes and how they move
Cerebellum
 The cerebellum is
important for
coordination and error
checking during motor,
perceptual, and cognitive
functions
 Is responsible for handeye coordination and
balance.
 Good way to remember
its function is “Cerebalance”.
Medulla Oblongata
 Is the control central for some of the most vital body
processes
 It controls automatic and homeostatic functions such as:
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Breathing
Heart Beats
Blood Vessel Activity
Swallowing
Vomiting
Digestion
Circadian Rhythms
 The biological clock of the body controlling cycles such
as the sleep/wake cycle
 Uses cues from the environment to change cycles.
 Examples of cues are light intensity and hunger.
 Paired up with the hypothalamic structures call the
Superchiasmatic nuclei, clusters of neurons in the
CNS.
Laterlization
 During brain development,
different function segregate to
either the left or the right
cerebral hemisphere
 The Left side is more adept to
language, math, logical
operations, etc
 The Right side is stronger at
pattern recognition, nonverbal
thinking and emotion
processes.
 Left side is factual
information while right side is
creativity.
Memory and Learning
 The body is constantly making connection
between what is happening to what has
already happen.
 Short-term Memory is stored in the frontal
lobe and are memories of what has recently
happened. When these memories become
irrelevant, the brain forgets them.
 Long-term Memory is aided by the
hippocampus. These are short-term
memories that were stored for later use. The
more a memory is used the easier it is to
remember, hence practice makes perfect
Disease/Nervous Problems
 Schizophrenia:
 A mental disturbance where the patient can no longer
distinguish between reality and imagination.
 Bipolar Disorder:
 Involves swings of mood from high to low and affects 1%
of the population
 Alzheimer's Disease:
 Mental deterioration which results in confusion, memory
loss, and other variable symptoms. Usually the results of
old age