Nervous System Flashcards
Organs and Divisions
1) Central Nervous System
- brain and spinal cord
2) Peripheral Nervous System
- nerves of body
a) autonomic NS-involuntary
- sympathetic
- parasympathetic
b) somatic NS-voluntary
Overview
- transmits info rapidly by nerve impulses
- homeostasis possible only if physiological control and integration systems function properly
- by 2 processes
- conduction of nerve impulses
- exchange of ions b/w interior and exterior of neuron - passing of nerve impulse across synapse
- synapse req. production, release, deactivation of neurotransmitters
- function by stimulating receptors in neuron
- conduction of nerve impulses
Neurons
- nerve cells
- conduct impulses
- 3 parts-cell body, dendrites, axon
- classified by direction impulse transmitted
- sensory (afferent) -impulse TO brain/spinal cord from body
- Motor (efferent) -impulse FROM brain/spinal cord to body
- only to muscle and glandular epithelial
- interneurons
- impulse from sensory to motor neurons
- connect to form complex, central networks
- aka central or connecting neurons
Dendrites
- branching projection
- transmit impulse TO cell body
Axon
- one, elongated projection
- transmits impulse FROM cell body
- surrounded by myelin (fatty, formed by Schwann cells)
- Nodes of Ranvier-indentations b/w Schwann cells
- Neurilemma-outer cell membrane, for regeneration
- brain and spinal cord axons have no neurilemma
Glia
- aka neuroglia
- don’t transmit impulses
- supporting cells
- hold together and protect neurons
1) Astrocytes
- large, like stars
- form blood-brain barrier (BBB)
2) Microglia
- help clean up cell damage by eating microbes
3) Oligodendrocytes
- hold nerve fibers together
- produce myelin sheaths in brain and spinal cord (CNS)
4) Schwann Cells
- form myelin sheaths in PNS
Nerves and Tracts
Nerve
- group of peripheral nerve fibers bundled together
- have myelin sheath (gives white appearance)
Tracts
- bundles of axons in CNS
- myelinated (white matter), unmyelinated (grey matter)
Nerves and Tracts Terms
Endoneurium
- fibrous connective tissue wrapping each axon
- groups are fascicles
Perineurium
-thin fibrous tissue around each fascicle
Epineurium
-tough, fibrous sheath covering whole nerve
Reflex Arcs
- nerve impulses aka action potentials, travel along neural pathways
- basic type of neuron pathway, allowing impulse in one direction
- 2 neuron arc (sensory and motor neurons)
- 3 neuron arc (sensory, interneuron, and motor neurons)
- reflex is response to impulse conduction over reflex (2 neuron) arc
- withdrawal reflex over 3 neuron arc, pull away from stim.
Components of Reflex Arc
1) Receptor
- beg. of dendrites of sensory
- impulse starts
2) Synapse
- space between neurons
3) Effector
- organ putting nerve signal into effect
Nerve Impulses
- self-propagating wave of electrical disturbance that travels along surface of neuron membrane
- initiated by stim. (temp., pressure, chemical change)
- Resting membrane is polarized (+outside, -inside)
- temporarily depolarized
- quickly repolarized
- moves along surface (action potential)
- saltatory conduction
- jumps gaps in myelin sheath
- faster than nonmyelinated
Synapse
- presynaptic neuron
- first neuron (transmits from)
- postsynaptic neuron
- second neuron (transmits to)
Structures:
1) Synaptic Knob
2) Synaptic Cleft
3) Plasma Membrane of Postsynaptic Neuron
Synaptic knob
- tiny bulge at end of terminal branch of presynaptic neuron’s axon
- each vesicle has neurotransmitter
- released when impulse reaches
Synaptic Cleft
- space between knob and plasma membrane of postsynaptic neuron
- narrow
- receives neurotransmitter
Plasma Membrane of Postsynaptic Neuron
- has protein molecules (receptors for neurotransmitter)
- binding initiates impulse to continue
Neurotransmitters
- assist, stim. or inhibit postsynaptic neurons
- released by synaptic knob, received by synaptic cleft, bind to protein receptors
- acetylcholine
- spinal cord and neuromuscular junctions
- catecholamines
- norepi, epi, serotonin
- sleep, motor function, mood, pleasure
- endorphins, enkephalins
- spinal cord and brain
- natural pain killers
Brainstem
Medulla oblongata
- enlarged, upward extension of spinal cord
- inside cranial cavity, white and grey matter
- two-way conduction
- cardiac, resp., vasomotor control
Pons
- white and bits of grey matter, mostly fiber tracts
- two-way conduction
- control of resp.
Midbrain
- consists of white and bits of grey matter
- two-way conduction
- visual and auditory impulses
Cerebellum
- under occipital lobe
- thin outer layer (grey matter)
- large surface area of nervous connections
- interior mostly white matter tracts
- branch in tree-like pattern
- produce smooth, coordinated movement, maintain equilibrium, sustain normal posture
Diencephalon
- small
- located between midbrain and cerebrum
- hypothalamus, thalamus, pineal body
Hypothalamus
- posterior pituitary and 3rd ventricle are extensions
- control over internal organs
- regulation of water balance, sleep cycles, appetite, temp., pleasure, fear, anger, arousal, pain
Thalamus
- dumbbell-shaped section of grey matter
- associate sensations with emotions
- arousal/alerting mechanisms
Pineal Body
- posterior to thalamus
- adjust melatonin, keep internal clock on time
Cerebrum
- largest and uppermost part of brain
- many ridges (gyri) and grooves (sulci) (fissure)
- longitudinal fissure divides into R&L hemispheres
- connected by corpus collosum - each hemisphere divided into 4 lobes
- cerebral cortex
- thin layer of grey matter
- forms surface of cerebrum
- basal nuclei
- islands of grey matter, within white matter
- produce automatic movements and postures
- sensory perception, emotions, willed movements, consciousness, memory
Brain Hemispheres
1) Parietal
- primary somatic, sensory area
- voluntary, conscious
- recognize pain, cold, touch, NOT special senses
2) Occipital
- visual
3) Temporal
- auditory and olfactory
4) Frontal
- primary motor area
- consciously move skeletal muscles
Spinal Cord-Structure
- enclosed within vertebral column
- continuation of brain stem that allows communication to/from brain
- 17 inches long, width of thumb
- grey matter and mostly dendrites and cell bodies
- spinal tracts provide two-way conduction path
Spinal Cord-Function
- centers for 1000s of reflex arcs
- switches/transfers incoming sensory impulses to outgoing motor impulses
- carry impulse to(sensory)/from (motor) brain
Cranial Nerves
- 12 pairs, attached to undersurface of brain
- extend from brain stem
- conduct impulses between brain and head/neck, thoracic and ab. cavities
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I Olfactory-sense of smell (nose to brain)
II Optic-vision (eye to brain)
III Oculomotor-eye movement (brain to eye muscles)
IV Trochlear-eye movement (brain to ext. eye muscles)
V Trigeminal-sensation in face, and chewing (skin/teeth to brain)
VI Aducens-eye movement (brain to ext. eye muscles)
VII Facial-taste, facial exp. (tongue to brain, brain to face)
VIII Vestibulcochlear-hearing, balance (ear to brain)
IX Glossopharyngeal-throat, taste, swallowing (throat to brain)
X Vagus-voice, heartbeat, peristalsis, swallowing
XI Accessory-shoulder and head movement (brain to shoulder/neck)
XII Hypoglossal-tongue movement (brain to tongue muscles)
Spinal Nerves
- 31 pairs, attached to spinal cord
- 8 cervical, 12 thoracic, 5 lumbar, 5 sacrospinal, 1 coccygeal
- Id’d by letter and number (ex. C1)
- branch to form peripheral nerves of trunk and limbs
- conduct impulses b/w spinal cord and body parts not supplied by cranial nerves
- make possible sensations and movements
- dermatones
- skin surface areas supplied by single spinal nerve
Autonomic NS
- autonomic neurons
- motor neurons of ANS
- ganglia
- peripheral “junction boxes” where axons of autonomic neurons terminate
- preganglionic neurons
- impulses b/w spinal cord and a ganglion
- postganglionic neurons
- impulses from ganglion to cardiac, smooth muscle or glandular epithelial tissue
- autonomic/visceral effectors
- tissues to which autonomic neurons conduct impulses
Sympathetic NS-Structure
Sympathetic Preganglionic axons synapse with postganglionic neurons
- frequently in widespread neurons
- leaves spinal cord, enters spinal nerve, leaves
- then through sympathetic ganglion
- terminate in collateral ganglion
- synapses with several postganglionic neurons terminating in visceral effectors
Sympathetic postganglionic neurons
- look like 2 chains of beads
- travel in spinal nerves to blood vessels, sweat glands, arrector pili, hair muscles
Sympathetic NS-Function
- emergency system, when we cope with stress of any kind
- fight or flight response
- rapidly produce widespread changes
- increased heart rate, constricts and dilates blood vessels, decreased peristalsis, pupil dilates, goose bumps, increased epi, sweat
Parasympathetic NS-Structure
- dendrites in grey matter of brainstem
- axons terminate in parasympathetic ganglia in head and thoracic/ab cavities
- response by only one organ-each parasymp preganglionic neuron synapses only with post ganglionic neurons to a single effector
Parasympathetic NS-Function
- control many visceral effectors under normal conditions
- counterbalance sympathetic function and returns to normal
