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sphincter : band of muscle that controls movement of materials throughout the digestive tract | https://openstax.org/books/biology/pages/34-key-terms |
stomach : saclike organ containing acidic digestive juices | https://openstax.org/books/biology/pages/34-key-terms |
sucrase : enzyme that breaks down sucrose into glucose and fructose | https://openstax.org/books/biology/pages/34-key-terms |
trypsin : pancreatic protease that breaks down protein | https://openstax.org/books/biology/pages/34-key-terms |
villi : folds on the inner surface of the small intestine whose role is to increase absorption area | https://openstax.org/books/biology/pages/34-key-terms |
vitamin : organic substance necessary in small amounts to sustain life | https://openstax.org/books/biology/pages/34-key-terms |
The nervous system is made up of neurons and glia. Neurons are specialized cells that are capable of sending electrical as well as chemical signals. Most neurons contain dendrites, which receive these signals, and axons that send signals to other neurons or tissues. There are four main types of neurons: unipolar, bipol... | https://openstax.org/books/biology/pages/35-chapter-summary |
Neurons have charged membranes because there are different concentrations of ions inside and outside of the cell. Voltage-gated ion channels control the movement of ions into and out of a neuron. When a neuronal membrane is depolarized to at least the threshold of excitation, an action potential is fired. The action po... | https://openstax.org/books/biology/pages/35-chapter-summary |
The vertebrate central nervous system contains the brain and the spinal cord, which are covered and protected by three meninges. The brain contains structurally and functionally defined regions. In mammals, these include the cortex (which can be broken down into four primary functional lobes: frontal, temporal, occipit... | https://openstax.org/books/biology/pages/35-chapter-summary |
The peripheral nervous system contains both the autonomic and sensory-somatic nervous systems. The autonomic nervous system provides unconscious control over visceral functions and has two divisions: the sympathetic and parasympathetic nervous systems. The sympathetic nervous system is activated in stressful situations... | https://openstax.org/books/biology/pages/35-chapter-summary |
Some general themes emerge from the sampling of nervous system disorders presented above. The causes for most disorders are not fully understoodâat least not for all patientsâand likely involve a combination of nature (genetic mutations that become risk factors) and nurture (emotional trauma, stress, hazardous chem... | https://openstax.org/books/biology/pages/35-chapter-summary |
acetylcholine : neurotransmitter released by neurons in the central nervous system and peripheral nervous system | https://openstax.org/books/biology/pages/35-key-terms |
action potential : self-propagating momentary change in the electrical potential of a neuron (or muscle) membrane | https://openstax.org/books/biology/pages/35-key-terms |
Alzheimerâs disease : neurodegenerative disorder characterized by problems with memory and thinking | https://openstax.org/books/biology/pages/35-key-terms |
amygdala : structure within the limbic system that processes fear | https://openstax.org/books/biology/pages/35-key-terms |
arachnoid mater : spiderweb-like middle layer of the meninges that cover the central nervous system | https://openstax.org/books/biology/pages/35-key-terms |
astrocyte : glial cell in the central nervous system that provide nutrients, extracellular buffering, and structural support for neurons; also makes up the blood-brain barrier | https://openstax.org/books/biology/pages/35-key-terms |
attention deficit hyperactivity disorder (ADHD) : neurodevelopmental disorder characterized by difficulty maintaining attention and controlling impulses | https://openstax.org/books/biology/pages/35-key-terms |
autism spectrum disorder (ASD) : neurodevelopmental disorder characterized by impaired social interaction and communication abilities | https://openstax.org/books/biology/pages/35-key-terms |
autonomic nervous system : part of the peripheral nervous system that controls bodily functions | https://openstax.org/books/biology/pages/35-key-terms |
axon : tube-like structure that propagates a signal from a neuronâs cell body to axon terminals | https://openstax.org/books/biology/pages/35-key-terms |
axon hillock : electrically sensitive structure on the cell body of a neuron that integrates signals from multiple neuronal connections | https://openstax.org/books/biology/pages/35-key-terms |
axon terminal : structure on the end of an axon that can form a synapse with another neuron | https://openstax.org/books/biology/pages/35-key-terms |
basal ganglia : interconnected collections of cells in the brain that are involved in movement and motivation; also known as basal nuclei | https://openstax.org/books/biology/pages/35-key-terms |
basal nuclei : see basal ganglia | https://openstax.org/books/biology/pages/35-key-terms |
brainstem : portion of the brain that connects with the spinal cord; controls basic nervous system functions like breathing, heart rate, and swallowing | https://openstax.org/books/biology/pages/35-key-terms |
cerebellum : brain structure involved in posture, motor coordination, and learning new motor actions | https://openstax.org/books/biology/pages/35-key-terms |
cerebral cortex : outermost sheet of brain tissue; involved in many higher-order functions | https://openstax.org/books/biology/pages/35-key-terms |
cerebrospinal fluid (CSF) : clear liquid that surrounds the brain and spinal cord and fills the ventricles and central canal; acts as a shock absorber and circulates material throughout the brain and spinal cord. | https://openstax.org/books/biology/pages/35-key-terms |
choroid plexus : spongy tissue within ventricles that produces cerebrospinal fluid | https://openstax.org/books/biology/pages/35-key-terms |
cingulate gyrus : helps regulate emotions and pain; thought to directly drive the bodyâs conscious response to unpleasant experiences | https://openstax.org/books/biology/pages/35-key-terms |
corpus callosum : thick fiber bundle that connects the cerebral hemispheres | https://openstax.org/books/biology/pages/35-key-terms |
cranial nerve : sensory and/or motor nerve that emanates from the brain | https://openstax.org/books/biology/pages/35-key-terms |
dendrite : structure that extends away from the cell body to receive messages from other neurons | https://openstax.org/books/biology/pages/35-key-terms |
depolarization : change in the membrane potential to a less negative value | https://openstax.org/books/biology/pages/35-key-terms |
dura mater : tough outermost layer that covers the central nervous system | https://openstax.org/books/biology/pages/35-key-terms |
ependymal : cell that lines fluid-filled ventricles of the brain and the central canal of the spinal cord; involved in production of cerebrospinal fluid | https://openstax.org/books/biology/pages/35-key-terms |
epilepsy : neurological disorder characterized by recurrent seizures | https://openstax.org/books/biology/pages/35-key-terms |
excitatory postsynaptic potential (EPSP) : depolarization of a postsynaptic membrane caused by neurotransmitter molecules released from a presynaptic cell | https://openstax.org/books/biology/pages/35-key-terms |
frontal lobe : part of the cerebral cortex that contains the motor cortex and areas involved in planning, attention, and language | https://openstax.org/books/biology/pages/35-key-terms |
glia : (also, glial cells) cells that provide support functions for neurons | https://openstax.org/books/biology/pages/35-key-terms |
gyrus : (plural: gyri) ridged protrusions in the cortex | https://openstax.org/books/biology/pages/35-key-terms |
hippocampus : brain structure in the temporal lobe involved in processing memories | https://openstax.org/books/biology/pages/35-key-terms |
hyperpolarization : change in the membrane potential to a more negative value | https://openstax.org/books/biology/pages/35-key-terms |
hypothalamus : brain structure that controls hormone release and body homeostasis | https://openstax.org/books/biology/pages/35-key-terms |
inhibitory postsynaptic potential (IPSP) : hyperpolarization of a postsynaptic membrane caused by neurotransmitter molecules released from a presynaptic cell | https://openstax.org/books/biology/pages/35-key-terms |
limbic system : connected brain areas that process emotion and motivation | https://openstax.org/books/biology/pages/35-key-terms |
long-term depression (LTD) : prolonged decrease in synaptic coupling between a pre- and postsynaptic cell | https://openstax.org/books/biology/pages/35-key-terms |
long-term potentiation (LTP) : prolonged increase in synaptic coupling between a pre-and postsynaptic cell | https://openstax.org/books/biology/pages/35-key-terms |
major depression : mental illness characterized by prolonged periods of sadness | https://openstax.org/books/biology/pages/35-key-terms |
membrane potential : difference in electrical potential between the inside and outside of a cell | https://openstax.org/books/biology/pages/35-key-terms |
meninge : membrane that covers and protects the central nervous system | https://openstax.org/books/biology/pages/35-key-terms |
microglia : glia that scavenge and degrade dead cells and protect the brain from invading microorganisms | https://openstax.org/books/biology/pages/35-key-terms |
myelin : fatty substance produced by glia that insulates axons | https://openstax.org/books/biology/pages/35-key-terms |
neurodegenerative disorder : nervous system disorder characterized by the progressive loss of neurological functioning, usually caused by neuron death | https://openstax.org/books/biology/pages/35-key-terms |
neuron : specialized cell that can receive and transmit electrical and chemical signals | https://openstax.org/books/biology/pages/35-key-terms |
nodes of Ranvier : gaps in the myelin sheath where the signal is recharged | https://openstax.org/books/biology/pages/35-key-terms |
norepinephrine : neurotransmitter and hormone released by activation of the sympathetic nervous system | https://openstax.org/books/biology/pages/35-key-terms |
occipital lobe : part of the cerebral cortex that contains visual cortex and processes visual stimuli | https://openstax.org/books/biology/pages/35-key-terms |
oligodendrocyte : glial cell that myelinates central nervous system neuron axons | https://openstax.org/books/biology/pages/35-key-terms |
parasympathetic nervous system : division of autonomic nervous system that regulates visceral functions during rest and digestion | https://openstax.org/books/biology/pages/35-key-terms |
parietal lobe : part of the cerebral cortex involved in processing touch and the sense of the body in space | https://openstax.org/books/biology/pages/35-key-terms |
Parkinsonâs disease : neurodegenerative disorder that affects the control of movement | https://openstax.org/books/biology/pages/35-key-terms |
pia mater : thin membrane layer directly covering the brain and spinal cord | https://openstax.org/books/biology/pages/35-key-terms |
proprioception : sense about how parts of the body are oriented in space | https://openstax.org/books/biology/pages/35-key-terms |
radial glia : glia that serve as scaffolds for developing neurons as they migrate to their final destinations | https://openstax.org/books/biology/pages/35-key-terms |
refractory period : period after an action potential when it is more difficult or impossible for an action potential to be fired; caused by inactivation of sodium channels and activation of additional potassium channels of the membrane | https://openstax.org/books/biology/pages/35-key-terms |
saltatory conduction : âjumpingâ of an action potential along an axon from one node of Ranvier to the next | https://openstax.org/books/biology/pages/35-key-terms |
satellite glia : glial cell that provides nutrients and structural support for neurons in the peripheral nervous system | https://openstax.org/books/biology/pages/35-key-terms |
schizophrenia : mental disorder characterized by the inability to accurately perceive reality; patients often have difficulty thinking clearly and can suffer from delusions | https://openstax.org/books/biology/pages/35-key-terms |
Schwann cell : glial cell that creates myelin sheath around a peripheral nervous system neuron axon | https://openstax.org/books/biology/pages/35-key-terms |
sensory-somatic nervous system : system of sensory and motor nerves | https://openstax.org/books/biology/pages/35-key-terms |
somatosensation : sense of touch | https://openstax.org/books/biology/pages/35-key-terms |
spinal cord : thick fiber bundle that connects the brain with peripheral nerves; transmits sensory and motor information; contains neurons that control motor reflexes | https://openstax.org/books/biology/pages/35-key-terms |
spinal nerve : nerve projecting between skin or muscle and spinal cord | https://openstax.org/books/biology/pages/35-key-terms |
sulcus : (plural: sulci) indents or âvalleysâ in the cortex | https://openstax.org/books/biology/pages/35-key-terms |
summation : process of multiple presynaptic inputs creating EPSPs around the same time for the postsynaptic neuron to be sufficiently depolarized to fire an action potential | https://openstax.org/books/biology/pages/35-key-terms |
sympathetic nervous system : division of autonomic nervous system activated during stressful âfight or flightâ situations | https://openstax.org/books/biology/pages/35-key-terms |
synapse : junction between two neurons where neuronal signals are communicated | https://openstax.org/books/biology/pages/35-key-terms |
synaptic cleft : space between the presynaptic and postsynaptic membranes | https://openstax.org/books/biology/pages/35-key-terms |
synaptic vesicle : spherical structure that contains a neurotransmitter | https://openstax.org/books/biology/pages/35-key-terms |
temporal lobe : part of the cerebral cortex that processes auditory input; parts of the temporal lobe are involved in speech, memory, and emotion processing | https://openstax.org/books/biology/pages/35-key-terms |
thalamus : brain area that relays sensory information to the cortex | https://openstax.org/books/biology/pages/35-key-terms |
threshold of excitation : level of depolarization needed for an action potential to fire | https://openstax.org/books/biology/pages/35-key-terms |
ventricle : cavity within brain that contains cerebrospinal fluid | https://openstax.org/books/biology/pages/35-key-terms |
A sensory activation occurs when a physical or chemical stimulus is processed into a neural signal (sensory transduction) by a sensory receptor. Perception is an individual interpretation of a sensation and is a brain function. Humans have special senses: olfaction, gustation, equilibrium, and hearing, plus the general... | https://openstax.org/books/biology/pages/36-chapter-summary |
Sensory receptors are either specialized cells associated with sensory neurons or the specialized ends of sensory neurons that are a part of the peripheral nervous system, and they are used to receive information about the environment (internal or external). Each sensory receptor is modified for the type of stimulus it... | https://openstax.org/books/biology/pages/36-chapter-summary |
All sensory signals, except those from the olfactory system, enter the central nervous system and are routed to the thalamus. When the sensory signal exits the thalamus, it is conducted to the specific area of the cortex dedicated to processing that particular sense. | https://openstax.org/books/biology/pages/36-chapter-summary |
Somatosensation includes all sensation received from the skin and mucous membranes, as well as from the limbs and joints. Somatosensation occurs all over the exterior of the body and at some interior locations as well, and a variety of receptor types, embedded in the skin and mucous membranes, play a role. | https://openstax.org/books/biology/pages/36-chapter-summary |
There are several types of specialized sensory receptors. Rapidly adapting free nerve endings detect nociception, hot and cold, and light touch. Slowly adapting, encapsulated Merkelâs disks are found in fingertips and lips, and respond to light touch. Meissnerâs corpuscles, found in glabrous skin, are rapidly adapt... | https://openstax.org/books/biology/pages/36-chapter-summary |
There are five primary tastes in humans: sweet, sour, bitter, salty, and umami. Each taste has its own receptor type that responds only to that taste. Tastants enter the body and are dissolved in saliva. Taste cells are located within taste buds, which are found on three of the four types of papillae in the mouth. | https://openstax.org/books/biology/pages/36-chapter-summary |
Regarding olfaction, there are many thousands of odorants, but humans detect only about 10,000. Like taste receptors, olfactory receptors are each responsive to only one odorant. Odorants dissolve in nasal mucosa, where they excite their corresponding olfactory sensory cells. When these cells detect an odorant, they se... | https://openstax.org/books/biology/pages/36-chapter-summary |
Audition is important for territory defense, predation, predator defense, and communal exchanges. The vestibular system, which is not auditory, detects linear acceleration and angular acceleration and deceleration. Both the auditory system and vestibular system use hair cells as their receptors. | https://openstax.org/books/biology/pages/36-chapter-summary |
Auditory stimuli are sound waves. The sound wave energy reaches the outer ear (pinna, canal, tympanum), and vibrations of the tympanum send the energy to the middle ear. The middle ear bones shift and the stapes transfers mechanical energy to the oval window of the fluid-filled inner ear cochlea. Once in the cochlea, t... | https://openstax.org/books/biology/pages/36-chapter-summary |
The vestibular system has five parts that work together to provide the sense of direction, thus helping to maintain balance. The utricle and saccule measure head orientation: their calcium carbonate crystals shift when the head is tilted, thereby activating hair cells. The semicircular canals work similarly, such that ... | https://openstax.org/books/biology/pages/36-chapter-summary |
Vision is the only photo responsive sense. Visible light travels in waves and is a very small slice of the electromagnetic radiation spectrum. Light waves differ based on their frequency (wavelength = hue) and amplitude (intensity = brightness). | https://openstax.org/books/biology/pages/36-chapter-summary |
In the vertebrate retina, there are two types of light receptors (photoreceptors): cones and rods. Cones, which are the source of color vision, exist in three formsâL, M, and Sâand they are differentially sensitive to different wavelengths. Cones are located in the retina, along with the dim-light, achromatic recep... | https://openstax.org/books/biology/pages/36-chapter-summary |
Visual signals travel from the eye over the axons of retinal ganglion cells, which make up the optic nerves. Ganglion cells come in several versions. Some ganglion cell axons carry information on form, movement, depth, and brightness, while other axons carry information on color and fine detail. Visual information is s... | https://openstax.org/books/biology/pages/36-chapter-summary |
audition : sense of hearing | https://openstax.org/books/biology/pages/36-key-terms |
basilar membrane : stiff structure in the cochlea that indirectly anchors auditory receptors | https://openstax.org/books/biology/pages/36-key-terms |
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