Download The Nervous System

The Nervous System
Nerve Cells (SEM x 2,250).
• http://www.pbs.org/wgbh/nova/mind/probe.html
• http://www.pbs.org/wnet/brain/
http://science.howstuffworks.com/brain9.htm
Nervous System
• the body's information gatherer,
storage center and control system
Neurons – specialized cells; functional
unit of nervous system
The Neuron
http://www.brainpop.com/health/nervoussystem/nervoussystem/
.
• basic unit of structure and function
• nerve cells – conduct impulses
Cell body
• contains nucleus & most organelles
Dendrites –branchlike extensions
• receive signals from other neurons
Axon – long fiber; transmits signals to other
cells (neurons or effectors)
– myelin sheath a lipid layer which covers some
axons
• insulates
• speeds up transmission through axon
Neural Signaling
• Neurons do
not act alone
as individual
cells
• Neurons lie
end to end
with axons
to dendrites
(do not
touch)
middle.
Some types of neurons: motoneuron (a), sensory neuron (b), cortical pyramidal cell (c)
Neurons also vary with respect to their functions:
3 types of neurons
• Sensory neurons – transmits info
from sensors (receptors)to the CNS.
– detect external or internal
changes
• Interneurons –within the CNS.
Analyze and interpret the sensory
input
• Motor neurons – transmits motor
output from the CNS to muscle cells
or endocrine cells (effectors)
Nerve Impulses
• a flow of electrical charges along The
cell membranes of a neuron.
• electrical activity
causes the release of
neurotransmitters
(chemicals) into the
synaptic cleft
• neurotransmitters
trigger activity in the
second neuron
• neurons have an electrical charge
different from the fluid that surrounds
them.
– A difference in electrical charge
between two locations is called a
potential
Resting Potential
• neuron is not receiving or sending a signal
• inside of the neuron is negatively charged
– concentration of negatively charged
proteins and K+ is greater inside the cell
• outside the cell is positively charged
– Na+ is greater outside the cell
Action Potential
• when a neuron is stimulated it becomes
permeable to Na+
• Na+ rapidly moves into the cell
• Results in a change in the charges inside
and outside the cell or
depolarization
Repolarization
• K+ diffuse outward resulting in the inside of
the neuron to become negatively charged
again
Review
• A neuron at rest has a higher concentration
of K+ inside the cell and a higher
concentration of Na + outside the cell.
Why?
The Nerve Impulse
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html
•
http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter45/animations.html#
•
http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120107/anim0013.sw
f::Voltage Gated Channels and the Action Potential
•
http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120107/bio_a.swf::Sodium-Potassium
Exchange
•
Chemical Synapse
2 Major Divisions
Central Nervous System (CNS)
• consist of the brain and the spinal cord.
Peripheral Nervous System (PNS)
• consists of the neurons NOT included in the brain
and sp cord.
– afferent neurons - collect info and transmits it toward
the CNS
– efferent neurons – transmit info away from the CNS
Neuron Signal
Transmission
2 major divisions of N. S.
• 1. Central Nervous System (CNS)
– Control center of the body
– Brain and spinal cord
• The spinal cord carries messages from the body to
the brain
• Messages are analyzed and interpreted
• Response messages are passed from the brain
through the spinal cord and to the rest of the body
The Brain
http://www.brainpop.com/health/nervoussystem/brain/
• The brain is the main unit of the central
nervous system
• It is the place to which impulses flow and
from which impulses originate
• Forebrain
3 main parts
– Cerebrum – the control center of the brain
– Responsible for all the voluntary activies of the
body
– The site of intelligence, learning and judgement
– Functions in language, conscious thought,
memory, personality development, visions and
other sensations.
• Cerebrum - divided into two hemispheres
– The right and left
– Each hemisphere is divided into regions called
lobes
• Frontal, parietal, temporal and occipital lobes
– The left side of the body sends its sensations to
the right hemisphere, and the right side of the
body send its sensations to the left hemisphere
– The r. hem is associated with creativity and
artistic ability
– The l. hem is associated with analytical and
mathematical ability
– Thalamus - relay station for nerve impulses carrying
sensory information into the brain
– Hypothalamus - regulates certain metabolic
processes and other autonomic activities.
• Cerebellum – located at the back of the
brain
– Coordinated muscle movements
– Controls balance, posture and coordination
• The brain stem – connects the brain to the
spinal cord
– controls the automatic functions (heart rate, blood
pressure), limb movements and organ functions
(digestion, urination).
– every nerve impulse that passes between
the brain and the spinal cord must pass
through the brainstem
• Brain stem divided into 3 parts:
– Midbrain
– Pons
– Medulla oblongata
The spinal cord
http://www.brainpop.com/health/nervoussystem/spinalcord/
• communication link between the brain and the
peripheral nervous system (PNS) – the rest of the
body
– Carries impulses to and from the brain
• Regulates reflexes
– A reflex is a response to a stimulus
• Examples: sneezing , blinking
– Reflexes are very fast and most never reach the brain
• 2. Peripheral Nervous System (PNS)
– Consists of nerves or neurons that extend
outside the CNS
• connects the CNS to other parts of the body
• Example: serves the limbs and organs
2 divisions of PNS
Somatic nervous system
• regulates activities that are under conscious
control
– (movement of skeletal muscles)
• and external sensory receptors
– reflexes
• Autonomic Nervous System - consists of
motor neurons that control internal organs.
– The autonomic system controls muscles in the
heart, the smooth muscle in internal organs
such as the intestine, bladder, and uterus.
– involves the homeostasis of organs
•
THE AUTONOMIC NERVOUS
SYSTEM IS FURTHER SUBDIVIDED
INTO TWO PARTS:
–
–
•
THE SYMPATHETIC DIVISION
THE PARASYMPATHETIC DIVISION
The TWO parts have OPPOSITE
EFFECTS on the ORGANS they control.
Fight or Flight
• When the brain perceives a threat or danger, messages are sent
to a section of your nerves called the autonomic nervous system
(ANS) which then activates the adrenal glands in the kidneys to
secrete chemicals, such as adrenaline and noradrenaline, which
key up the body for fight or flight.
• The autonomic nervous system is divided into two sub-sections
called the sympathetic nervous system and the parasympathetic
nervous system. The sympathetic nervous system is the actual
system that releases energy and prepares the body for action.
The body then typically restores itself back to normal after a
period of time by the parasympathetic nervous system, which
acts as a kind of stabilizer.
• Destruction of large patches of Myelin
characterize a disease called Multiple
Sclerosis.
• Normal nerve function is impaired, causing
symptoms such as double vision, muscular
weakness, loss of memory, and paralysis.
Stroke
• Blood vessels in the brain are blocked by
blood clots
• Circulation to an area is blocked and the
brain tissue dies
– A severe stroke in one side of the brain may
cause paralysis of the other side of the body
• Meningitis –
• inflammation of the membrane covering the
brain
• Epilepsy
– - storms of electrical activity in the brain that can cause
seizures
• Shingles
– - infection of sensory nerves caused by a virus