Chapter 7: The Nervous System Flashcards
Sensory Input
Gathering information
- to monitor changes occurring inside & outside the body
- changes = stimuli
Integration
To process and interpret sensory input and decide whether action is needed
Motor Output
- A response to integrated stimuli
- The response activates muscles or glands
Central Nervous System
(CNS)
Consists of organs that interpret incoming sensory info and issue instructions based on past experiences and current conditions
- Brain
- Spinal Cord
Peripheral Nervous System
(PNS)
Nerves extending from the brain and spinal cord.
- Spinal nerves
- Cranial nerves
- Functions: Serve as a communication lines among sensory organs (brain & spinal cord) and glands or muscles.
Spinal Nerves
Carry impulses to and from the spinal cord
Cranial Nerves
Carry impulses to and from the brain
Sensory (afferent) Division
Nerve fiber that carry info to the central nervous system
Somatic Sensory Fibers
Carry info from the skin, skeletal muscles, and joints
Visceral Sensory Fibers
Carry info from visceral organs
Motor (efferent) Division
Nerve fibers that carry impulses away from the central nervous system
- 2 Subdivisions
- Somatic Nervous System
- Autonomic Nervous System
Somatic Nervous System
- Voluntary
- Consciously controls skeletal muscles
Autonomic Nervous System
- Involuntary
- Automatically controls smooth and cardiac muscles and glands
- Further divided into the sympathetic and parasympathetic nervous systems
Neuroglia
Nerve glue
Functions:
- Support
- Insulate
- Protect Neurons
Astrocytes
(CNS Glial Cell)
Abundant, star-shaped cells
Functions:
- Brace Neurons
- From barrier between capillaries and neurons
- Control the chemical environment of the brain
Microglia
(CNS Glial Cell)
Spider-like Phagocytes
Functions:
- Dispose of debris
Ependymal Cells
(CNS Glial Cell)
Lines cavities of the brain and spinal cord. Cilia assist with circulation of cerebrospinal fluid.
Oligodendrocytes
(CNS Glial Cell)
Wrap around nerve fibers in the central nervous system
- Produce myelin sheaths around axons
Satellite Cells
(PNS Glial Cell)
Protect neuron cell bodies
Schwann Cells
(PNS Glial Cell)
Form myelin sheath in the peripheral nervous system
- Form around axons in a jelly-roll like fashion
Neurons
nerve cells, specialized to transmit messages
Major regions
- Cell body
- Processes
Cell Body
Nucleus and metabolic center of the cell
Processes
Fibers that extend from the cell body
Dendrites
Conduct impulses toward the cell body
- Neurons may have hundreds
Axons
Conduct impulses away from the cell body
- Neurons have only one, arising from the cell body at the hillock
- End in terminals
Axon Terminals
Contain vesicles with neurotransmitters, and separated from each other by gaps
Synaptic Cleft
Gap between adjacent neurons
Synapse
Junction between nerves
Myelin Sheaths
Whitish, fatty material covering axons
Nodes of Ranvier
Gaps in myelin sheaths along the axon
Gray Matter
Cell bodies and unmyelinated fibers and cell bodies
In the brain: outer layer in the cerebral cortex; composed mostly of cell bodies.
Nuclei
Clusters of cell bodies within the white matter of the central nervous system
Ganglia
Collections of cell bodies outside the central nervous system
Tracts
Bundles of nerve fibers in the CNS
Nerves
Bundles of nerve fiber in the PNS
White Matter
Collections of myelinated fibers (tracts), fiber tracts deep to the gray matter
Sensory (afferent) Neurons
Carry impulses from the sensory receptors to the CNS
Cutaneous Sense Organs
Simpler types of sensory receptors in the skin
Proprioceptors
Detect stretch or tension
Motor (efferent) Neurons
Carry impulses from the central nervous system to viscera, muscles, or glands
Interneurons (association neurons)
Found in neural pathways in the CNS, connect sensory and motor neurons
Multipolar Neurons
Many extensions from the cell body
- All motor and interneurons are multipolar
- Most common structure
Bipolar Neurons
One axon and one dendrite
- Located in special sense organs (nose and eye)
- Rare in adults
Unipolar Neurons
Have a short single process leaving the cell body
- Sensory neurons found in PNS ganglia
- Conduct impulses both toward and away from the cell body
Polarized
There are fewer positive ions sitting on the inner face of the neuron's plasma membrane than on its outer face
Irritability
Ability to respond to a stimulus and convert it to a nerve pulse
Conductivity
Ability to transmit the impulse to other neurons, muscles, or glands
Resting Neurons
The plasma membrane at rest is polarized, as long as the inside is more negative then the outside the cell stays at rest.
Action Potential
Activates the neuron to initiate and transmit a long-distance signal
Reflexes
Rapid, predictable, and involuntary responses to a stimulus
- occur over neural pathways called reflex arcs
Somatic Reflexes
Reflexes that stimulate the skeletal muscles.
- Ex: pulling you hand away from a hot object
Autonomic
Regulate the activity of smooth muscles, the heart, and glands
- Ex: Regulation of smooth muscles, heart and blood pressure, glands, digestive system.
Sensory Receptor
Reacts to a stimulus
Sensory Neuron
Carries messages to the integration center
Integration Center (CNS)
Process info and directs motor output
Motor Neuron
Carries message to an effector
Effector Organ
Is the muscles or gland to be stimulated
2-Neuron Reflex Arcs
Simplest type
- Ex: Patellar (knee-jerk) reflexs
3-Neuron Reflex Arcs
Consists of 5 elements: receptors, sensory neuron, interneuron, motor neuron, and effector
- Ex: flexor (withdrawal) reflex
Lobes
Divided by fissures (deep grooves)
Primary Motor Area
Sends impulses to skeletal muscles, located in frontal lobe