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Main Function:
Communication system controls and coordinates functions throughout the body and responds to internal and
external stimuli.
.
Physiological functions• Governs the functions of the body
• Control over muscles, glands, and organs
• Controls heartbeat, breathing, digestion,
and urination
• Regulate blood flow , concentration of
chemicals in the blood.
• Maintaining homeostasis
• Formation of ideas
Central nervous system (CNS)
• Brain and spinal cord
• Housed in the skull and vertebral column
• Three layers ( meninges) ,surround the
brain and spinal cord (Pia matter,
Arechenoids and Dura matter).
• The space between middle and inner
layer is filled with cerebrospinal fluid
(CSF).
Includes all sensory
and motor nerves
Somatic division
(Motor function)
autonomic division
(visceral function)
peripheral nervous system (PNS).
Somatic and autonomic.
• Somatic nervous system controls voluntary
functions of the body, such as the muscle
contractions that cause the limbs to move
• Autonomic nervous system controls the rest of
the involuntary functions such as heart rate and
breathing, digestion and body temperature
regulation
• Parasympathetic:Housekeeping tasks
• Sympathetic: Fight or escape
•
• 12 cranial nerves & 31 spinal nerves.
• Carry two types of information:
(1) sensory impulses traveling to the
CNS from sensory receptors in the
body
(2) motor impulses traveling away
from the CNS to muscles and glands.
A nerve is an organ
containing a bundle
of nerve cells called
neurons.
Neurons carry
electrical messages
called impulses
throughout the
body. Picture shows hundreds of
neuron axons
Parts of a Neuron
Axon: long projection that carries impulses away from cell body
1
32
Dendrites: projections that bring impulses into the neuron to the cell body.
Cell body: contains nucleus & most of the cytoplasm
Sensory Neuron
Interneuron
Motor Neuron
Sensory Neuron
Interneuron
Motor Neuron
Muscle Contracts
Synapse
Synapse
Synapse
Motor Neurons
carry impulses from the
brain & spinal cord to
muscles & glands
Axon End
Axons branching out
to muscle fibers
.
Neurotransmitters
Synapse (gap)
The message
is transferred
when
RECEPTORSreceive neurotrans-mitters.
(pink
spheres)
Nerve Cell Impulses: •Flow of ions across the plasma membranes
(force drive sodium & potassium ions from one side to the other)** Tiny electrodes on the outside and inside of the plasma membrane**Potential difference (- 70 millivolts)resting P. **Plasma membrane is positively charged on the out side and negatively charged on the inside.** Sodium ions are found in greater concentration outside ,potassium ions are found in greater concentration inside the cell.
Action Potential
Neuron stimulated sudden membrane permeability protein pores open sodium flow in.
(1) upswing, depolarization(voltage goes from -70 millivolts to +30)
(2) downswing, repolarization, the return to the resting potential.
** Increases cell permeability, resulting in a
change in the resting potential
** Protein pores in the plasma membrane open.** Sodium ions flow into the cell through the pores.
** Shift in the resting potential from-70 to +30 (depolarization).** After depolarization, the membrane
returns to its previous state(repolarization) : (1) a sudden decrease in the membrane’s
permeability to sodium (stops the influx of sodium
(2) a rapid outflow of potassium ions
Synaptic Transmission:
• .A synapse consists of
• (1) a terminal (presynaptic neuron)
• (2) a gap (synaptic cleft)
• (3) the membrane of the
• dendrite or postsynaptic cell
• Rapid influx of calcium ions into the bouton from the
extracellular fluid
• Calcium stimulate the release of a chemical substance
stored (neurotransmitters) into the synaptic cleft
• Bind to receptors in the plasma membrane of the
postsynaptic neuron
• Rapid increase in the permeability of the membrane of
the postsynaptic cell to sodium ions.
• Nerve impulse travels down the new nerve cell
• Nerves work together with muscles for movement.
• An impulse begins when one neuron is stimulated by
another neuron or by the sense organs.
• The impulse travels down the axons of Sensory
neurons to the brain cells called Interneurons.
• The brain will then send an impulse through motor
neurons to the necessary muscle or organs, telling it
to contract.