FORM & FUNCTION (NS Overview) Flashcards
Key functions of the NS:
-receives sensory info from the environment
>external: temperature, pressure, pain
>internal: osmotic pressure, BP
-process information
-generate motor response
Key components of the NS:
-CNS: brain and spinal cord
-PNS: nerves and ganglia
Brain:
-receives and processes sensory information
-initiates responses
-stores memories
-generates thoughts and emotions
Spinal cord:
-conducts signals to and from the brain
-controls reflex activities
Nerves:
-cranial, spinal, peripheral nerves conduct impulses to and from the CNS
Ganglia:
-small groups of nerve cells outside the CNS
-sensory and autonomic
Main functions of the NS (3 steps):
- Sensory input (PNS)
- Integration (CNS)
- Motor output (PNS)
Sensory input (PNS):
-collects data from internal and external environments via sensory receptors
Integration (CNS):
-processes and interprets the sensory input and decides on the action to be taken
Motor output (PNS):
-executes the action by activating muscles or glands
NS coordinates with other systems:
-works with the endocrine system for physiological regulation
-interacts with the muscular system for movement control
Neurons:
-functional unit of NS
-receives signals from the environment and within the body, integrates sensory info and generates output signals to an effector organ of the body to elicit an appropriate response
-info processing
-gives rise to nerves
Neuroglia (>90% of the NS):
-most abundant cell types in the NS
-surround most of the neuronal cell bodies, processes of axons and dendrites
-provide structure and functional support for neurons
Anatomy of a neuron:
-soma or perikaryon
-dendrites
-axon hillock
-axon
-terminal arborization and boutons
Soma or perikaryon:
-cell body
-large spherical euchromatic nucleus and prominent nucleolus
-highly developed rER into aggregates of parallel cisternae and numerous polyribosomes
-golgi
-mitochondria found throughout
-neurofilaments are abundant (intermediate filaments)
-occasionally contain lipofusion
Dendrites:
-elongated process that receive stimuli
-usually short and branched
-covered with many synapses
-cytoplasmic composition similar to cell body, but no golgi
-dendritic spines
Dendritic spines:
-where synapses impinge on
Axon:
-elongated processes that specialize in propagating nerve impulses (action potential)
-most neurons only have one
-axon hillock
-axolemma
-axoplasm
Axon hillock:
-specialized in initiating nerve impulses (action potential)
Axolemma:
-plasma membrane of the axon
Axoplasm:
-cytoplasm of the axon
-contains mitochondria, cytoskeleton, cisternae of sER
-NO rER or polyribosomes
Terminal arborization and boutons:
-where NT are released into synapse
Different morphology of neurons:
-multipolar
-bipolar
-unipolar
Grey matter:
-groups of neuronal cell bodies
White matter:
-groups of axons
Ganglion:
-groups of neuronal cell bodies in the PNS
Nucleus:
-groups of neuronal cell bodies in the CNS
Classification of neurons by function (3):
-motor (efferent) neurons
-sensory (afferent) neurons
-interneurons
Motor (efferent) neurons:
-control effector organs such as muscle fibers and exocrine and endocrine glands
-neuronal cell body located in CNS
-signal direction: CNS to PNS
Sensory (afferent) neurons:
-reception of sensory stimuli from the environment and from within the body
-neuronal cell body is located within ganglion in the PNS
-signal direction: PNS to CNS
Interneurons:
-information processing
Components of the PNS:
- Sensory NS
- Motor NS
2 pathways in the PNS:
- Somatic (voluntary)
- Visceral (autonomic/involuntary)
Somatic (voluntary) pathway:
-sensation: conscious
-target: skeletal muscle
Visceral (autonomic/involuntary) pathway:
-sensation: unconscious
-targets: glandular cells, smooth and cardiac muscle
-subdivision: sympathetic and parasympathetic
PNS sensory pathways:
-similar both somatic and visceral
-receive afferent impulses that go to the CNS
-in both cranial and dorsal root of spinal nerves
-neurons relay information from the ganglions nerve endings to the gray matter of the spinal cord via synapses with local neurons
PNS motor pathways:
-differ between somatic and visceral
Somatic motor pathway:
-one-neuron system (“on-off control”)
-single motor neuron extends from CNS directly to the skeletal muscle fiber
*voluntary
Visceral motor (autonomic) motor pathway:
-two-neuron chain (“push-pull control”)
-a preganglionic neuron from the CNS synapses onto a postganglionic neuron in an autonomic ganglion
>postganglionic neuron innervates the target tissue (glandular cells, cardiac and smooth muscle)
*involuntary
