Download Central Nervous System

CENTRAL NERVOUS SYSTEM
TABLE OF CONTENTS
• Introduction
• Electrochemical impulse generation
• Synaptic transmission
• How is a reflex arc formed
FUNCTION
• Maintain homeostasis
• Control automatic functions
• React to stimuli
SET UP
• Central nervous system
• Periphiral nervous system
• Sensory pathways
• Motor pathways
• Autonomic nervous system
• Somatic nervous system
PERIPHIRAL NERVOUS SYSTEM
• Named because its located around the central nervous system
• Divided into sensory neurons and motor neurons
• Motor neurons can be divided into the automatic and somatic nervous systems
AUTONOMIC NERVOUS SYSTEM
• Responsible for involuntary body functions.
•
Heartbeat
•
Breathing
•
Digestion
•
Etc
• Divided further into sympathetic and parasympathetic nervous systems
• Sympathetic
• Parasympathetic
•
Controls fight or flight response
•
Maintain normal body function
•
Bladder relaxaion
•
Controls pupil dilation
•
conserves physical energy
•
Slows heart rate
CENTRAL NERVOUS SYSTEM
• Consists of the brain and spine
• Recieves information
• Controls the body’s response
STRUCTURE OF NERVOUS SYSTEM
• Made up of neurons
• Runs through the entire body
• Sends signals to muscles and to glands
NEURONS AND GLIAL CELLS
• Nervous system cells
• Three structural types of neurons
•
Bipolar
•
Unipolar
•
Multipolar
• Three functional types of neurons
•
Sensory input
•
Integration
•
Motor output
UNIPOLAR
• A single process that extends from the cell body
• Dendrite and axon are fused
• Found in the peripheral nervous system
• Created by the fusion of two polar processes during development.
MULTIPOLAR
• Has several dendrites
• Has a single axon
• Found in the brain and spinal cord.
BIPOLAR
• Has a single main dendrite
• Has a single axon
• Found in the inner ear, retina of the eye, and the olfactory center of the brain.
SENSORY NEURONS
• Sensory receptor, such as those in the skin
• Recieves input as a nerve impulse
• Part of the central nervous system
INTEGRATION NEURONS
• Known as interneurons
• Found in the central nervous system
• Act as a link between the sensory and motor neurons
MOTOR NEURONS
• Transmit information from the central nervous system
• Transmits to effectors, effectors include muscles glands, and other organs.
ELECTROCHEMICAL
IMPULSE
AKA: AN ACTION POTENTIAL
BY: RITA KUMAR
DISCOVERY OF ELECTROCHEMICAL IMPULSES
Luigi Galvani
Julius Bernstein
Luigi Galvani (1737 – 1798)
Julius Bernstein (1839-1917)
K.S. Cole
and H.J.
Curtis
•
experimented with frogs
at University of Bologna
in a solution of saltwater
•
Proposed the membrane
hypothesis (1902)
Cole and
Curtis
decided to
test this
theory
•
accidentally touched two
different metals together
•
Neurons have selectively
permeable cell
membranes. These
membranes allow for the
transport of K+ and Na+
ions
Extracted
neuron from
a squid
•
results indicated
electrical stimulation
•
At rest, the neuron has a
potential difference
across its membrane
tested with
an electrode
spanning the
cell
membrane
•
K+ flow out of the cell,
resulting in a decrease of
potential difference
They proved
Bernstein’s
hypothesis
K.S. Cole
WHAT DOES IT DO FOR THE BODY?
• The purpose of electrochemical impulse is to pass a stimulus-generated impulse down the neural axon
to a receptor, be it another neuron or a muscle.
• The passing of electrochemical impulses allows for organisms to recall, feel, think, emote, hear, see, etc.
• Without proper nerve conduction, diseases such as multiple sclerosis may occur.
• Since like charges repel, the highly
positive Na+ ions repel each other, and
want in the cell membrane.
SODIUM POTASSIUM PUMP
• The sodium-potassium pump allows
these ions to cross an otherwise
impermeable membrane.
• 3 Na+ ions move out of the membrane
using the pump
• 2 K+ move in the membrane using the
same pump
• The net effect, since there are more
Na+ ions outside than K+ ions inside,
the cell membrane has a strong
positive charge outside. The difference
from the inside to the outside is -70
mV, or the resting potential.
STEPS IN AN ELECTROTONIC POTENTIAL
• There are voltage gated ion channels for sodium and channels for potassium ions.
• A stimulus forces a Na+ channel open.
• Sodium ions flow into the cell
• The voltage across the membrane will increase
• When the voltage reaches its threshold potential, other voltage gated ion channels are stimulated, and
they open as well
• Electrotonic potentials faster than action potentials.
• The effect of electrotonic potential diminishes the further down the cell you go.
STEPS IN AN ACTION POTENTIAL
•
The threshold potential for an action potential is -55 mV.
•
The Na+ channel is forced open.
•
Sodium ions flow into the cell, increasing the potential across the cell greatly.
•
The sodium ion channels close at +40 mV
•
Now, the inside of the cell is more positively charged than the outside.
•
The potassium gate opens at +40 mV
•
Potassium ions flow out of the cell due to repulsive forces, decreasing the voltage
•
The voltage overshoots since it went lower than the resting potential.
•
The potassium gate closes at -80 mV.
•
The sodium channel is reactivated to bring the voltage back up to 70 mV.
•
Action potentials are “all-or-none”, that is, the voltage must reach -55 mV before it can take place.
•
This is an endergonic process, and is slower than the electrotonic potential, but this works better over longer axons.
STRUCTURE OF A NEURON
WORKS CITED LIST
SIGNAL TRANSMISSION ACROSS A SYNAPSE
• -Impulse.... Origin of stimulus--> Sensory Neurons --> Brain --> Motor Neurons --> Muscles or Glands
• synapse: connection between 2 neurons or neuron & effectorExample of effector: Muscle Fibres
SIGNAL TRANSMISSION ACROSS A SYNAPSE
• Neurotransmitter: carry signal fom neuron to neuron or effector
• Pre-Before
Post-After
SIGNAL TRANSMISSION ACROSS A SYNAPSE
• 1) Action potential (A.P) arrives at end of presynaptic neuron, the impulse causes intracellular sacs
(synaptic vesicles) which contain neurotransmitters to fuse to the axons membrane. Synaptic vesicles
release neurotransmitter into synaptic cleft: (space between neurons) by exocytosis
SIGNAL TRANSMISSION ACROSS A SYNAPSE
• exocytosis: transport method in which vacuole fuses with cell membrane & releases contents outside
cell
SIGNAL TRANSMISSION ACROSS A SYNAPSE
• 2) Released neurotransmitter diffuses across synapse taking 0.5-1 ms to reach the dendrites of post
synaptic neuron or cell membrane of effector
SIGNAL TRANSMISSION ACROSS A SYNAPSE
• 3) Contents released (the neurotransmitters) and bind to receptor proteins which polarize the post
synaptic membrane and allow for Na + ions to flow through the ion channel protein into the
postsynaptic channel
• When the postsynaptic membrane is polarized, the threshold potential could be reached which initiates
an action potential. The impulse will travel along postsynaptic neuron to its terminal and to the next
neuron or effector.
SIGNAL TRANSMISSION ACROSS A SYNAPSE
• 4) Enzyme will break up the neurotransmitters in the postsynaptic neuron and its components will be
reabsorbed by the presynaptic neuron.
HOW IS A REFLEX ARC A
FORM OF FEEDBACK?
JUDY ZHONG
32
OVERVIEW
• Definitions
• The main sections of the Nervous System that are involved in the Reflex Arc
• Feedback System Vs. Reflex Arc
• Video
33
DEFINITIONS
• Reflexes:
•
An involuntary response to a certain stimulus
• Reflex Arc:
•
A simple connection of neurons that results in a reflex action
• Feedback systems:
•
A cycle of events in which a variable is monitored, assessed and adjusted (used to maintain homeostasis)
34
STRUCTURE OF NERVOUS SYSTEM
Nervous
System (NS)
Central Nervous
System (CNS)
Spinal Cord
Peripheral Nervous
System (PNS)
Brain
Sensory Pathways
Motor Pathways
Somatic Nervous
System (voluntary)
Autonomic Nervous
System (involuntary)
Sympathetic
Nervous System
Parasympathetic
Nervous System
35
COMPARISON
Reflex Arc
Negative Feedback
System
MHR Biology 12
Fig.8.3,pg 346 (Negative Feedback System)
Fig.8.11, pg 353 (Reflex Arc)
36
VIDEO
• http://www.youtube.com/watch?v=9uBjz5JpRAU
37