Biology Nervous System Flashcards
The nervous system is composed of both ___ (specialized nervous tissue) and neuroglia (cells that support and protect the neurons)
neurons
___ are the functional units of the nervous system
neurons
Neurons primary function is to convert stimuli into electrochemical signals and conduct these ___ throughout the body
signals
Each neuron is generally an elongated cell consisting of ___, a cell body and an axon
dendrites
___ are cytoplasmic extensions that receive information and transmit it toward the cell body
dendrites
The cell body (soma) contains the nucleus and controls the ___ activity of the neuron
metabolic
The axon is a long cellular process that transmits ___, also known as action potentials, away from the cell body
impulses
The axon is a long cellular process that ___ impulses, also known as action potentials, away from the cell body
transmits
Between the cell body and axon is the ___ hillock, where the incoming signals (from the dendrites) are summed and, if great enough, trigger an action potential down the axon.
axon
The axons terminate in swellings known as ___ terminals (also called boutons or knobs)
synaptic
When an action potential arrives at the synaptic terminal, ___ are released from these terminals into the synapse (or synaptic cleft), which is the gap between the axon terminals of one cell and the dendrites of the next cell
neurotransmitters
Most mammalian axons area sheathed by an insulating substance known as ___, which prevents leakage of signal from the axons and allows for faster conduction of impulses
myelin
The gaps between segments of myelin, the ___ of Ranvier, are where the action potential actually propagates
nodes
Action potential propagation via the nodes of Ranvier occurs through a process known as ___ (“hopping”) conduction
saltatory
___ is produced by glial cells known as oligodendrocytes in the central nervous system and by Schwann cells in the peripheral nervous system
myelin
Neurons receive information at the dendrites, process information at the ___ hillock, and transmit information through the axon
axon
The processing of the information is relatively straightforward: if sufficient ___ occurs at the axon hillock, then an action potential is triggered down the axon
depolarization
There are no partial ___ potentials and therefore no variation in the strength of an action potential
action
The potential difference at rest between the extracellular space and the intracellular space is called the resting ___
potential
A typical resting membrane potential is -70 millivolts (mV), which means the inside of the ___ is more negative than the outside
neuron
The uneven ion exchange of the sodium potassium pump (3 NA out 2 K in) results in one more positive charge leaving the ___ than entering it, creating a negative internal environment
cell
Cell membrane is more permeable to K than Na allowing some of the K that was pumped into the cell to move back out through ___ diffusion, making the internal environment even more negative
facilitated
If the membrane potential reaches the ___ potential of -55 mV, then voltage-gated Na channels open triggering the action potential
threshold
In actuality, the membrane potential after ___ is 35 mV
depolarization
During ___ the membrane potential can range between -70 and -75 mV
hyperpolarization
Depolarization occurs when a cell reaches threshold ___ and voltage-gated Na channels open allowing the influx of Na into the neuron
potential
The result of this influx is that the cell membrane potential reaches 35 mV and the cell is said to be ___
depolarized
During ___, at the peak potential of 35 mV, voltage gated K channels open
depolarization
During depolarization, since there is a high intracellular concentration K, the opening of K channels allows for the efflux (leaving) of K down its ___ gradient
concentration
During depolarization, the efflux of positive charges is termed ___ and results in the membrane potential decreasing to a negative value thus repolarizing the membrane
repolarization
When the cell membrane decreases to below resting potential this is known as the ___ period
refractory
The refractory period: a period of time after the action potential in which new action potentials are very ___ to initiate
difficult
___operate only in one direction and because refractory periods make the backward travel of action potentials
synapses
The greater the diameter of the axon and the greater its ___, the faster the impulses travel
myelination
Myelin increases the conduction velocity by insulating segments of the axon such that the membrane is permeable to ions only in the ___ of Ranvier
nodes
The synapse is the gap between the axon terminal of one neuron (the ___ neuron) and the dendrites of the next neuron (the postsynaptic neuron)
presynaptic
Neurons may also communicate with postsynaptic cells other than neurons, such as cells in muscles or glands, these are called ___ cells
effector
The axon terminal contains thousands of membrane-bound vesicles full of chemical messengers known as ___
neurotransmitters
When the action potential arrives at the axon terminal and depolarizes it, the synaptic vesicles fuse with the presynaptic membrane and release ___ into the synapse
neurotransmitter
The released neurotransmitter will lead to depolarization of the postsynaptic cell and consequent firing of an ___ potential
action
Neurotransmitter is removed from the synapse in a variety of ways: it may be taken back up into the nerve terminal (via a protein known as an uptake carrier) where it may be reused or degraded; it may be ___ by enzymes located in the synapse (e.g., acetylcholinesterase inactivates the neurotransmitter acetylcholine); or it may simply diffuse out of the synapse
degraded
Neurons that carry sensory information about the external or internal environment to the ___ or spinal cord are called afferent neurons
brain
Neurons that carry motor commands from the ___ or spinal cord to various parts of the body (e.g., muscles or glands) are called efferent neurons
brain
Some neurons (interneurons) participate only in local circuits, linking ___ and motor neurons in the brain and spinal cord; their cell bodies and their nerve terminals are in the same location
sensory
Nerves are essentially ___ of axons covered with connective tissue
bundles
A network of nerve fibers is called a ___
plexus
Neuronal cell bodies often cluster together: such clusters are called ___ in the periphery; in the central nervous system, they are called nuclei
ganglia
CNS
Astrocytes: maintain the integrity of the blood-brain barrier, regulate nutrient and dissolved gas concentrations, an absorb and recycle neurotransmitters
Oligodendrocytes: myelinate CNS axons as well as provide structural framework for the CNS
Microglia: remove cellular debris and pathogens
Ependymal cells: line the brain ventricles and aid in the production, circulation, and monitoring of cerebral spinal fluid
PNS
Satellite cells: surround the neuron cell bodies of the ganglia
Schwann cells: enclose the axons in the PNS and aid in the ___ of some peripheral axons
myelination
The forebrain consists of the telencephalon and the ___
diencephalon
A major component of the telencephalon is the cerebral cortex, which is the highly convoluted gray matter that can be seen on the ___ of the brain
surface
The cortex processes and integrates sensory input and motor ___ and is important for memory and creative thought
responses
The telencephalon also includes the olfactory bulb, the center for reception and ___ of olfactory (smell-related input)
integration
The diencephalon contains the ___ and hypothalamus
thalamus
The thalamus is a relay and integration center for the spinal cord and cerebral ___
cortex
The midbrain (mesencephalon) is a relay center for visual and ___ impulses
auditory
The hindbrain is the posterior part of the brain and consists of the ___, the pons and the medulla
cerebellum
One function of the ___ is to act as a relay center to allow the cortex to communicate with the cerebellum
pons
Together, the midbrain, pons, and ___ constitute the brainstem
medulla
Sensory information enters the spinal cord through the ___ horn
dorsal
All motor information exits the spinal cord through the ___ horn
ventral
The sensory nerves that enter the CNS and motor nerves that leave the CNS are ___ of the peripheral nervous system
part
Peripheral nervous system has the ___ and the autonomic
somatic
The somatic nervous system (SNS) innervates skeletal muscles and is responsible for voluntary movement as well as reflex arcs(pathways that control ___ reflexes)
motor
The autonomic nervous system (ANS) is sometimes also called the involuntary nervous system because it regulates the body’s internal environment without the aid of ___ control
conscious
The ANS innervates ___ and smooth muscle
cardiac
The sympathetic division is responsible for the flight or fight responses that ready the body for action in an ___ situation
emergency
Sympathetic nervous system uses norepinephrine as its primary ___
neurotransmitter
The parasympathetic nervous system uses ___ as its primary neurotransmitter
acetylcholine
The eyeball is covered by a thick, opaque layer known as the sclera, which is also known as the ___ of the eye
white
Beneath the sclera is the ___ layer, which helps to supply the retina with blood
choroid
The innermost layer of the eye is the ___, which contains the photoreceptors that sense light
retina
The transparent ___ at the front of the eye bends and focuses light rays
cornea
After the front of the eye bends and focuses light rays the rays then travel through an opening called the pupil, whose ___ is controlled by the pigmented, muscular iris
diameter
After the ___, the light continues through the lens, which is suspended behind the pupil
pupil
The lens, the shape and focal length of which is controlled by ___ muscles, focuses the image onto the retina
ciliary
The eye also contains a jelly like material called the ___ humor that helps maintain its shape and optical properties
vitreous
The ___ humor is a more watery substance that fills the space between the lens and the cornea
aqueous
Cones respond to high intensity ___ are sensitive to color whereas rods detect low intensity illumination and are important in night vision
illumination
While there are many more rods than cones in the human eye, the central section of the retina, called the ___, has a high concentration of cones
macula
A sound wave first reaches the cartilaginous ___ (sometimes called auricle), the visible part of the ear
pinna
After the auricle, sound is then channeled into the external auditory canal, which focuses the sound wave toward the ___ membrane (eardrum) located at the end of the external auditory canal
tympanic
After the eardrum, the tympanic membrane vibrates with the frequency and magnitude of the incoming soundwave , thereby transferring the vibrational energy from the ___ to itself
air
The tympanic membrane is the boundary between the ___ and middle ear
outer
The middle ear contains three bones: the malleus (hammer), incus (anvil), and ___ (stirrup)
stapes
The ___, incus and stapes are collectively called ossicles
malleus
The ossicles vibrate with the same frequency as the ___ membrane and transfer the energy to another membrane, the oval window
tympanic
The oval window is much smaller than the tympanic membrane; thus the transfer of energy between the two membranes ___ the vibrations
amplifies
The inner ear which begins after the oval window contains the ___ and vestibule
cochlea
The vibration of the oval window pushes against fluid (___), resulting in pressure waves that travel through the fluid-filled cochlea
perilymph
The pressure waves of the perilymph are detected by hair cells, which transform mechanical stimuli into action potentials that travel down the ___ nerve
auditory
The auditory nerve follows the auditory pathway until it reaches the auditory ___, which is responsible for the processing of auditory information
cortex
The inner ear also contains the ___, which is a fluid filled structure responsible for balance and acceleration detection of the organism
vestibule
