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The Nervous System. Functions of the Nervous System. 1. Monitors internal and external environment 2. Take in and analyzes information 3. Coordinates voluntary and involuntary responses. Organs of the Nervous System. Brain and Spinal Chord (CNS) - PowerPoint PPT Presentation
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Functions of the Nervous System
• 1. Monitors internal and external environment• 2. Take in and analyzes information• 3. Coordinates voluntary and involuntary
responses.
Organs of the Nervous System
• Brain and Spinal Chord (CNS)• Sensory Receptors of Sense Organs (eyes, ears
etc) • Nerves connect nervous system with other
systems
Divisions of the Nervous System
• 1. Central Nervous System– Spinal Chord and Brain– Processing coordination of stimulus and response
2. Peripheral Nervous System- All neural tissue outside the CNS
- Delivers sensory information to the CNS and carries motor commands to the effectors
Functions of the CNS
• Are to process and coordinate:• - sensory data:
• From inside and outside the body
– Movement: • Control activities of peripheral organs (e.g. skeletal
muscles)
– Higher functions of the brain• Intelligence, memory, learning, emotion
Functions of the PNS
• 1. Deliver sensory information to the CNS• 2. Carry commands to peripheral tissues and
systems
Nerves
• Also called peripheral nerves: – Bundles of axon with connective tissues and blood
vessels– Carry sensory information and motor commands
in PNS: • Cranial nerves: connects to brain (12 pairs)• Spinal nerves: attach to spinal chord (31 pairs)
Divisions of the PNS
• Afferent Division:– Carries information from PNS to CNS
• Efferent Division:– Carries motor commands from CNS to PNS – Has somatic and autonomic components
The Efferent Division of the PNS
• Somatic Nervous System (SNS)– Controls skeletal muscle contraction• Voluntary muscle contractions• Reflexes
• Autonomic Nervous System (ANS)– Controls subconscious actions • Contraction of smooth and cardiac muscle• Glandular secretions
Neural Tissue
• Contains 2 kinds of cells– Neurons• Cells that send and receive signals
– Neuroglia• Cells that support and protect nerves
Neurons
• The basic functional units of the nervous system
• Parts of a neuron – Cell body (Soma)– Short, branched dendrites – Long, single axon
Dendrites
• Highly branched• Dendritic spines:– Receive information from other neurons– 80-90% of neuron surface area
The Axon
• Long• Carries electrical signal (action potential) to
target• Axon structure is critical to function
Nodes and Internodes
• Internodes– Myelinated segments of axon
• Nodes– Also called nodes of Ranvier– Gaps between internodes– Where axons may branch
Synapse
• Areas where a neuron communicates with another cell
• Presynaptic Cell– Neuron that sends message
• Postsynaptic Cell – Cell that receives message
• Synaptic Cleft– Gap that separates the presynaptic membrane
and the postsynaptic membrane
The Synaptic Knob
• Is expanded area of axon• Contains synaptic vesicles of
neurotransmitters– Chemical messengers– Released at presynaptic membrane– Affect receptors of postsynaptic membrane
Functional Classifications of Neurons
• Sensory Neurons– Deliver information to CNS
• Motor Neurons– Stimulate or inhibit peripheral tissues
• Interneurons– Located between sensory and motor neurons – Analyze inputs, coordinates outputs
Neuroglia Functions
• Line of central canal of spinal chord and ventricles of brain
• Repair damaged neural tissue• Processes contact between other neuron cell
bodies
Neuorglia
• Wrap around axons to form myelin sheaths (Schwann Cells)– Increases speed of action potentials– Myelin insulates myelinated axons– Makes nerves appear white (white matter)