biology chapter 7 Flashcards
nervous system
enables organisms to receive and respond to stimuli from their external and internal environments
neurons
are the functional units of the nervous system
dendrites
are cytoplasmic extensions that receive information and transmit it toward the cell body
cell body (soma)
contains the nucleus and controls the metabolic activity of the neuron
axon
is a long cellular process that transmits impulses away from the cell body
myelin
insulating substance that cover axons, which allow axons to conduct impulses faster
oligodendrocytes
produce myelin in the central nervous system
schwann cells
produce myelin in ther peripheral nervous sytem
nodes of Ranvier
the gaps between segments of myelin
synapse
or synaptic cleft, which is the fap between the axon terminals of one cell and the dendrites of the next cell
action potentials
impulses that travel the length of the axon and invade the nerve terminal, thereby causing the release of neurotransmitter into the synapse
resting potential
when a neuron is at rest, the potential difference between the extracellular space and the intracellular space
typical resting membrane potential
is -70 millivolts (mV) which means that the inside of the neuron is more negative than the outside
minimum threshold membrane potential
(usually around -50 mV) is the level at which an action potential is initiated
repolarization
returns the cell to a more negative potential
refractory period
immediately following an action potential, it may be very difficult or impossible to initiate another action potential
synapse
the gap between the axon terminal of one neuron and the dendrites of another neuron
neurotransmitters
the nerve terminal contains thousands of membrane bound vesicles full of chemical messengers
curare
blocks the post synaptic acetylcholine receptors so that acetylcholine is unable to interact with the receptor. This leads to paralysis by blocking nerve impulses to muscles
botulism toxin
prevents the release of acetylcholine from the presynaptic membrane and also results in paralysis
anti-cholinesterases
are used as nerve gases and in the insecticide Parathion. As the name implies, these substances inhibit the activity of the acetylcholinesterase enzyme. As a result the acetylcholine is not degraded in the synapse and continues to affect the post-synaptic membrane. therefore, no coordinated muscular contractions can take place
afferent neurons
neurons that carry sensory information about the external or internal environment to the brain or spinal cord
efferent neurons
neurons that carry motor commands from the brain or spinal cord to various parts of the body
plexus
a network of nerve fibers
ganglia
clusters of neuronal cell bodies
central nervous system
consists of the brain and spinal cord
brain
the brain is a mass of neurons that resides in the skull. Its functions include interpreting sensory information, forming motor plans, and cognitive function (thinking). The brain consists of an outer portion called the gray matter (cell bodies) and an inner white matter (myelinated axons). the brain can be divided into the forebrain, midbrain, and hindbrain)
forebrain (prosencephalon)
the forebrain consists of the telencephalon and the diencephalon
cerebral cortex
which is the highly convoluted gray matter that can be seen on the surface of the brain
olfactory bulb
is the center for reception and integration of olfactory input
diencephalon
contains the thalamus and hypothalamus
thalamus
is a relay and integration center for the spinal cord and cerebral cortex
hypothalamus
controls visceral functions such as hunger, thirst, sex drive, water balance, blood pressure, and temperature regulation
midbrain
is a relay center for visual and auditory impulses. It also plays an important role in motor control
hindbrain
is the posterior part of the brain and consists of the cerebellum, the pons and the medulla
cerebellum
helps to modulate motor impulses initiated by the cerebral cortex, and is important in the maintenance of balance, hand-eye coordination, and the timing of rapid movements
pons
is to act as a relay center to allow the cortex to communicate with the cerebellum
medulla
controls many vital functions such as breathing, heart rate, and gastrointestinal activity
brainstem
constituted by the midbrain, pons, and medulla
spinal cord
is an elongated extension of the brain which acts as the conduit for sensory information to the brain and motor information from the brain
peripheral nervous system
consists of nerves and ganglia
somatic nervous system
innervates skeletal muscles and is responsible for voluntary movement
autonomic nervous system
also called the involuntary nervous system because it regulates the body’s internal environment without the aid of conscious control
sympathetic nervous system
is responsible for the “flight or fight” responses that ready the body for action in an emergency situation. It increases blood pressure and heart rate, it increases blood flow to skeletal muscles and it decreases gut motility. It also dilates the bronchioles to increase gas exchange. it uses norepinephrine as its primary neurotransmitter
parasympathetic nervous system
acts to conserve energy and restore the body to resting activity levels following exertion (“rest and digest”). It acts to lower heart rate and to increase gut motility. It uses acetylcholine as its primary neurotransmitter
the eye
detects light energy (as photons) and transmits information about intensity, color, and shape to the brain
sclera
thick, opaque layer that covers the eyeball. It is also known as the white of the eye
choroid layer
which helps to suppy the retina with blood. It is a dark, pigmented area that reduces reflection in the eye
retina
innermost layer of the eye, which contains the photoreceptors that sense light
cornea
transparent at the front of the eye, bends and focuses light rays
iris
responds to the intensity of light in the surroundings
lens
suspended behind the pupil and focuses the image onto the retina
photoreceptors
that transduce light into action potentials
cones
respond to high intensity illumination and are sensitive to color
rods
detect low intensity illumination and are important in night vision
rhodopsin
absorbs a single wavelength
blind spot
the point at which the optic nerve exits the eye because photoreceptors are not present there
aqueous humor
is the thick watery liquid between the lense and cornea formed by the eye and exits through ducts to join the venous blood
myopia (nearsightedness)
occurs when the image is focused in front of the retina
hyperopia (farsightedness)
occurs when the image is focused behind the retina
astigmatism
is caused by an irregularly shaped cornea
cataracts
develop when the lens becomes opaque; light cannot enter the eye and blindness results
glaucoma
is an increase of pressure in the eye due to the blocking of the outflow of the aqueous humor
the ear
transduces sound energy (pressure waves) into impulses perceived by the brain as sound
outer ear
which consists of the auricle (external ear) and the auditory canal
tympanic membrane
(eardrum) of the middle ear, which vibrates at the same frequency as the incoming sound
ossicles
(malleus, incus, and stapes) amplify the stimulus, and transmit it through the oval window
inner ear
consists of the cochlea and the vestibular apparatus
vestibular apparatus
is involved in maintaining equilibrium
