Transcript Neuron - Cloudfront.net

Chapter 48
The Neurons
Cells Communicate
• Gap Junctions: communication
only between adjacent cells
• Hormones: distant cells but
very slow & broad.
• Neurons: fast & to specific cells
Different types of
neurons
• Sensory Neurons: carry impulses
from receptors to the spinal cord.
• Motor Neurons: carry impulses from
the spinal cord to the effectors.
• Association Neurons: = interneurons,
maintain connections within the
spinal cord
Reflex actions
• Reflex actions: involuntary and
usually self protective
movements.
• Reflex arc: the spinal cord is
responsible for transmitting the
response that pulls your hand
away.
Structure of a Neuron
• Neuron: nucleated cell body and 2
kinds of threadlike extensions,
dendrites and axons.
• Dendrites: receive impulses from
other neurons or receptors and carry
impulses to the cell body.
• Axon: carries impulses away from
the cell body.
• Synapses: small space between 2
neurons
• Schwann cells: cells organized on
layers that surround the axons.
These cells form a structure know as
myelin sheath, which insulates and
protects the axon.
• Nodes of Ranvier (ask Mr. Miller for
the pronunciation): gaps in the
myelin sheath.
NEURON
Nerve Impulses
• Resting Neuron
Na
K
K
Na
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• Active Neuron
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- - - - - - - - + + + + +
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Impulse conduction
• When a neuron is stimulated, its
membrane become permeable to
Na+.
• As a result the inner surface
becomes more positively charged
than the outer surface. This process
is called depolarization.
• K+ ions diffuses out of the cell.
Transmission across the
synapses
• Impulses are carried across a
synapse by chemical messengers
called neurotransmitters.
• Acetylcholine
• After transmission of an impulse,
neurotransmitters in the synapse are
destroyed by enzymes.
PERIPHERAL NERVE
CELLS
• RECEPTORS:RECEIVE INFO FROM
BOTH INTERNAL & EXTERNAL
STIMULI
• CONDUCTORS:TRANSMIT
MESSAGES FROM RECEPTORS TO
CNS
• EFFECTORS: RECEIVE MESSAGES
FROM CNS & CARRY THEM TO AN
AREA OF THE BODY
Senses: Receptors and
sense organs
• Mechanoreceptors: detect movement,
pressure, or tension.
• Photoreceptors: detect variations in
light.
• Chemoreceptors: detect chemicals
• Thermoreceptors: respond to both
internal and external heat and cold
• Pain receptors: respond to tissue
damage.
NERVOUS SYSTEM
NERVOUS
SYSTEM
CENTRAL
NERVOUS
SYSTEM
SPINAL CORD
PERIPHERAL
NERVOUS
SYSTEM
BRAIN
AUTONOMIC
NERVOUS
SYSTEM
SYMPATHETIC
NERVOUS
SYSTEM
SCARED
FRIGHTENED
PARASYMPATHETIC
NERVOUS
SYSTEM
SOMATIC
NERVOUS
SYSTEM
BRAIN
• CEREBRUM: 4 LOBES..1) FRONTAL,
2)PARIETAL, 3) OCCIPITAL,
4)TEMPORAL, THOUGHTS,
CONVOLUTIONS- FOLDS
• LEFT & RIGHT HEMISPHERE
• CEREBELLUM: COORDINATION &
BALANCE
• BRAIN STEM: THE MIDBRAIN,
MEDULLA and PONS
PROTECTION OF BRAIN
• MENINGES: THREE
PROCTECTIVE LAYER THICK
*DURA MATER: OUTER LAYER
*ARACHNOID: MIDDLE LAYER
*PIA MATER: INNER LAYER
 CEREBROSPINAL FLUID: FLUID
CUSHION BETWEEN THE
MIDDLE & INNER LAYERS
Divisions of the peripheral
nervous system
• Somatic nervous system consists of
nerves that control the voluntary
movement movement of the skeletal
muscles.
• Automatic nervous system consists
of the nerves that control involuntary
actions, such as respiration and
heart rate.
Divisions of the
Automatic NS
• The sympathetic nervous
system controls the stimulation
of internal organs during
conditions of high stress or
increased activity.
• The parasympathetic nervous
system controls internals organs
during routine conditions.