functions of the nervous system functions of the nervous system sensory input – gathering...
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Functions of the Nervous SystemFunctions of the Nervous System Sensory input – gathering information
To monitor changes occurring inside and outside the body
Changes = stimuli
Integration To process and interpret sensory input and decide if
action is needed
Motor output
A response to integrated stimuli
The response activates muscles or glands
Organization of the Nervous System
• 2 big initial divisions:1. Central Nervous System CNS
• The brain + the spinal cord– The center of integration and control
2. Peripheral Nervous System PNS• The nervous system outside of the brain
and spinal cord• Consists of:
– 31 Spinal nerves» Carry info to and from the spinal
cord– 12 Cranial nerves
» Carry info to and from the brain
Peripheral Nervous System
• Responsible for communication between the CNS and the rest of the body.
• Can be divided into:– Sensory Division
• Afferent division– Conducts impulses from receptors to the CNS– Informs the CNS of the state of the body interior and exterior– Sensory nerve fibers can be somatic (from skin, skeletal muscles or
joints) or visceral (from organs w/i the ventral body cavity)– Motor Division
• Efferent division– Conducts impulses from CNS to effectors (muscles/glands)– Motor nerve fibers
Motor Efferent Division
• Can be divided further:– Somatic nervous system
• VOLUNTARY (generally)• Somatic nerve fibers that conduct impulses from the
CNS to skeletal muscles
– Autonomic nervous system• INVOLUNTARY (generally)• Conducts impulses from the CNS to smooth muscle,
cardiac muscle, and glands.
Autonomic Nervous System• Can be divided into:
– Sympathetic Nervous System
• “Fight or Flight”
– Parasympathetic Nervous System
• “Rest and Digest”
These 2 systems are antagonistic.
Typically, we balance these 2 to keep ourselves in a state of dynamic balance.
Nervous Tissue
2 cell types1. Neurons
• Functional, signal conducting cells
2. Neuroglia• Supporting cells
1.
2.
Neuroglia• Outnumber neurons by about
10 to 1 (the guy on the right had an inordinate amount of them).
• 6 types of supporting cells– 4 are found in the CNS:
1. Astrocytes• Star-shaped, abundant, and
versatile• Controls the chemical
environment of the brain• Involved in the formation of the
blood brain barrier• Function in nutrient transfer
Neuroglia
2. Microglia• Specialized immune cells that act as
the macrophages of the CNS• Spider-like phagocytes dispose of
debris
3. Ependymal Cells• Line cavities of the brain and spinal
cord• Some are ciliated which facilitates
the circulation of cerebrospinal fluid
Neuroglia
4. Oligodendrocytes
• Produce the myelin sheath which provides the electrical insulation for certain neurons in the CNS
• 2 types of glia in the PNS1. Satellite cells
• Surround clusters of neuronal cell bodies in the PNS
• Unknown function
2. Schwann cells• Form myelin sheaths around
the larger nerve fibers in the PNS.
• Vital to neuronal regeneration
Neuroglia
Neurons• The functional and structural unit of the nervous system• Specialized to conduct information from one part of the body to
another• There are many, many different types of neurons but most have
certain structural and functional characteristics in common:
- Cell body (soma)- One or more
specialized, slender processes (axons/dendrites)
- An input region (dendrites/soma)
- A conducting component (axon)
- A secretory (output) region (axon terminal)
Neuron AnatomyNeuron Anatomy
Slide 7.10
Extensions outside the cell body Dendrites –
conduct impulses toward the cell body
Axons – conduct impulses away from the cell body
Figure 7.4a
Axons and Nerve ImpulsesAxons and Nerve Impulses
Slide 7.11
Axons end in axonal terminals
Axonal terminals contain vesicles with neurotransmitters
Axonal terminals are separated from the next neuron by a gap Synaptic cleft – gap between adjacent
neurons
Synapse – junction between nerves
Functional Classification of NeuronsFunctional Classification of Neurons
Slide 7.14a
Sensory (afferent) neurons
Carry impulses from the sensory receptors
Cutaneous sense organs
Proprioceptors – detect stretch or tension
Motor (efferent) neurons
Carry impulses from the central nervous system
Interneurons (association neurons)
Found in neural pathways in the central nervous system
Connect sensory and motor neurons
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