Nervous system Flashcards
nervous system
- receive and respond to stimuli from their internal/external environments
- composed of neurons and neuroglia
neuron
- specialized nervous tissue used to convert stimuli into electrochemical signals
- dendrites, cell body, and axons
cells in the CNS
-astrocyctes, oligodendrocytes, microglia, ependymal cells
astrocytes
-maintain the integrity of the BBB, regulate nutrient and dissolved gas concentrations, and absorb/recycle neurotransmitters
oligodendrocytes
myelinate CNS axons and provide structural framework
microglia
remove cellular debris and pathogens
ependymal cells
-line brain ventricles and aid in production of CSF
satellite cells
surround the neuron cell bodies in the ganglia
Schwann cells
enclose the axons in the PNS and myelinated some peripheral axons
Schwann cells
enclose the axons in the PNS and myelinated some peripheral axons
resting potential
-even at rest, a neuron is polarized due to unequal distribution of ions b/w the inside and outside of the cell, -70mV (inside is more negative than outside)
Na+/K+ pump
- pumps 3 Na+ out of the cell for every 2 K+ it transports in, causes negative internal environment
- cell membrane is permeable to K+ allowing some to move back out thru facilitated diffusion, making the inside even more -
action potential
-if the cell becomes sufficiently excited and depolarized (less negative) to reach the threshold potential, then voltage-gated channels open in response
an action potential begins when:
- voltage-gated Na+ channels open in response to depolarization
- Na+ rushes into the cell causing more depolarization
- action potential moves down the terminal until it reaches the synaptic terminal, where Ca2+ channel is opened and triggers the exocytosis of synaptic vesicles
after the signal has been propagated thru a segment of the axon…
- voltage-gated K+ channels open and K+ rushes out of the cell
- Na+/K+ pump begins to pump Na+ out of the cell
- repolarization occurs
hyperpolarization
voltage shoots past the resting potential and becomes even more negative inside
refectory period
- period of time after an action potential during which new action potentials are difficult to initiate immediately
- helps ensure the action potential only moves forward
impulse propagation
- occurs in one direction: dendritic to synaptic terminal
- different axons propagate at different speeds; greater the diameter, more it is myelinated, faster the impulse travels
synapse
gap b/w the axon terminal of one neuron (presynaptic neuron) and dendrites of another (postsynaptic neuron)
effector cells
neurons communicate with postsynaptic cells other than neurons, ex: muscles or glands
curare
- blocks postsynaptic nicotinic acetylcholine receptors, on muscles
- leads to muscle relaxation and paralysis
botulinum toxin
- prevents release of acetylcholine from the presynaptic membrane
- results in paralysis
anticholinesterases
- inhibit the activity of acetylcholinesterase enzyme responsible for degrading acetylcholine released in the synapse
- no coordinated muscle contraction can take place
afferent neurons
carry sensory info from environment to spinal cord
efferent neurons
carry motor commands from the brain/spinal cord to various parts of the body
interneurons
participate only in local circuits, linking sensory and motor neurons
ganglia
neuron cell bodies clustered together in the PNS
CNS includes:
brain and spinal cord
brain
-interpret sensory info, forms motor plans, and thinking
grey matter
-outer portion of cell bodies in the brain
white matter
-inner portion of myelinated axons
forebrain (prosencephalon)
-consist of telencephalon and diencephalon
cerebral cortex
- highly convoluted grey matter
- part of telencephalon
- important for memory and creative thought
diencephalon
-thalamus and hypothalamus
thalamus
-integration center for the spinal cord and cerebral cortex
hypothalamus
-controls visceral functions such as hunger, thirst, sex drive, blood pressure, temp regulation
midbrain
- relay center for visual and auditory impulses
- important in motor control
hindbrain (rhombencephalon)
-consists of cerebellum, pons, and medulla`
cerebellum
-helps modulate motor impulses initiated by cerebral cortex; balance, hand-eye coordination, and rapid movements
pons
-act as a relay center to allow the cortex to communicate with the cerebellum
medulla
-controls breathing, HR, and gastrointestinal activity
spinal cord
- acts as. conduit for sensory info to the brain and motor info from the brain
- integrates simple motor responses (reflexes)
- outer white matter (axons), inner grey matter (cell bodies)
dorsal horn
-where sensory info enters the spinal cord
ventral horn
-motor info exists the spinal cord
PNS includes:
nerves and ganglia
somatic nervous system
innervates skeletal muscles and responsible for voluntary movement
autonomic nervous system (involuntary)
- regulates body’s internal environment
- innervates cardiac and smooth muscle
- important in BP control, gastrointestinal motility, excretion, reproduction, and respiration
sympathetic nervous system
- “fight or flight”
- increase BP, HR, blood flow; decreases gut motility
- uses norepinephrine as its neurotransmitter
parasympathetic nervous system
- “rest and digest”
- lower HR, increase gut motility
- acetylcholine as its neurotransmitter
vagus nerve
-parasympathetic nerve that innervates thoracic and abdominal viscera
eye
-detects light energy and transmits info to the brain
sclera
thick, opaque layer that covers the eyeball
choroid
- beneath sclera
- supplies retina with blood
retina
innermost layer of eye, contains photoreceptors that sense light
cornea
at front of the eye, bends and focuses light rays
iris
-responds to intensity of light in the surroundings (light makes pupils contract)
lens
focuses the image onto the retina
two main type of photoreceptors:
- cones: high-intensity illumination, sensitive to color
- rods: low-intensity illumination, night vision
rhodopsin
rod pigments that only absorbs a single wavelength
bipolar cells
-photoreceptor cells synapse onto this which then synapse onto ganglion cells
blind spot
point at which the optic nerve exits the eye, no photoreceptors present
fovea
small area of the retina above the blindspot, densely packed with cones
vitreous humor
jelly-like material that helps maintain the shape and optical properties
aqueous humor
watery substance that fills the space b/w the lens and cornea
myopia (near sightedness)
occurs when the image is focused on the front of the retina
hyperopia (farsightedness)
occurs when the image is focused behind the retina
astigmatism
caused by an irregularly shaped cornea
cataracts
when lens become opaque, light cannot enter the eye
glaucoma
increase in pressure of the eye b/c of blocking of the outflow of aqueous humor
ear
tranduces sound energy (pressure waves) into impulses perceived by the brain as sound
outer ear
-consists of the auricle and the auditory canal
tympanic membrane (eardrum)
- at the end of the auditory canal
- vibrates at the same frequency as the incoming sound
ossicles
- malleus, incus, stapes
- amplify the stimulus and transmit it thru the oval window
- vibration stimulates hair cells in the basilar membrane to traduce pressure into action potentials which travel via the cochlear (auditory) nerve
inner ear consists of:
-cochlea and vestibular apparatus, involved in equilibrium
