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Chapter 04: Neurons, Hormones, and the Brain


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Central Nervous System
CENTRAL NERVOUS SYSTEM (CNS): the brain and spinal cord.
Spinal Cord
Part of the central nervous system extending from the base of the skull through the vertebrae of the spinal column. It is continuous with the brain stem, and like the brain it is encased in a triple sheath of membranes. Thirty-one pairs of spinal nerves arise from the sides of the spinal cord. The spinal cord carries information from the body's nerves to the brain and signals from the brain to the body.
spinal reflexes
The spinal cord provides a major pathway for ascending and descending neural tracts. In addition to this function, the spinal cord functions as the integration center for many reflexes. These are called spinal reflexes because their arcs pass through the spinal cord.
peripheral nervous system
The part of the nervous system consisting of everything but the brain and spinal cord. The PNS includes spinal and cranial nerves, ganglia, and plexuses.
Sensory nerve
a nerve that leads from receptors toward or to the central nervous system
Motor Nerves
Motor nerves enable the brain to stimulate muscle contraction. A motor nerve is an efferent nerve that exclusively contains the axons of motoneurons, which innervate skeletal muscle.
somatic nervous system
The somatic nervous system is that part of the peripheral nervous system associated with the voluntary control of body movements through the action of skeletal muscles. The somatic nervous system consists of afferent fibers which receive information from external sources, and efferent fibers which are responsible for muscle contraction.
autonomic nervous system
the part of the nervous system that is concerned with the control of involuntary bodily functions. It regulates the function of glands, especially the salivary, gastric, and sweat glands, and the adrenal medulla; smooth muscle tissue, and the heart. The autonomic nervous system may act on these tissues to reduce or slow activity or to initiate their function.
A technique in which patients are trained to gain some voluntary control over certain physiological conditions, such as blood pressure and muscle tension, to promote relaxation.
sympathetic nervous system
This part of the nervous system regulates involuntary reactions to stress such as increased heart and breathing rates, and other physiological reactions. Ever felt an 'adrenalin rush?' That was your sympathetic nervous system at its finest. Many asthma drugs, such as albuterol, mimic this system in attempting to relieve an asthma flare.
parasympathetic nervous system
The part of the nervous system which sends messages to the motor cells of smooth muscle, cardiac muscle, and gland cells has two physiologically and anatomically distinct parts. There is and 'upper' and a 'downer' division: the sympathetic and parasympathetic parts. The sympathetic division prepares you for stress and the parasympathetic nervous is dominant in between stressful events. The sympathetic division would increase heart rate and contractility and increase the likelihood of arrhythmias while the parasympathetic division does the opposite.
a cell which conducts electric neural impulses from one part of the body to another. Neurons are made up of dendrites (branch-like fibers which receive impulses) and axons (fibers which transmit impulses), and communicate with other neurons and effector organs at junctures called synapses
also called neuroglia; supportive cells of the nervous system that make up the blood-brain barrier, provide nutrients and oxygen to the vital neurons, and protect the neurons from infection, toxicity, and trauma. Some examples of glia are oligodendroglia, astrocytes, and microglia.
The branching portion of a neuron that receives synapses from the axons of other neurons.
cell body
The central structure of a neuron, which contains all of the molecular parts that keep the cell alive, generate new parts, and repair or destroy existing parts.
The extended part of a neuron that carries an impulse towards the synapse and transmits the message to other neurons.
axon terminals
axons commonly divide at the end into branches called what?
myeline sheath
a layer of myelin encasing (and insulating) the axons of medullated nerve fibers
a cordlike structure composed of fibers that conduct impulses between the central nervous system and other part of the body. A nerve cell is a neuron, or cell that conducts neural impulses.
stem cell
a precursor cell from which blood cells are derived. As they mature, stem cells evolve into various types of red and white blood cells and platelets. Stem cells are located in the bone marrow, the site of blood cell production. Stem cells divide rapidly and are vulnerable to chemotherapy and radiation
The capacity of the brain to change its structure and function within certain limits. Plasticity underlies brain functions such as learning and allows the brain to generate normal, healthy responses to long-lasting environmental changes.
action potential
The sudden change in electrical potential that travels down the axon of a neuron
synaptic vesicles
Membrane-bound compartments which contain transmitter molecules. Synaptic vesicles are concentrated at presynaptic terminals. They actively sequester transmitter molecules from the cytoplasm. In at least some synapses, transmitter release occurs by fusion of these vesicles with the presynaptic membrane, followed by exocytosis of their contents.
chemicals that are used to relay, amplify and modulate electrical signals between a presynaptic and a postsynaptic neuron.
receptor sites
A location in the cell where molecules of a certain nature, such as hormones can take effect on the cell to alter its biochemical processes.
These are endogenous biomechanical substances implicated in the alleviation of pain, produced as a result of body stress.
Chemical substances produced by glands which circulate in the blood and help control growth, reproduction and other functions.
endocrine gland
A gland that releases a chemical messenger, known as a hormone, directly into the bloodstream, that will affect other parts of the body. The thyroid is an endocrine gland.
A hormone produced by the pineal gland that regulates the level of activity in the brain.
adrenal hormones
hormones that are produced by the adrenal glands and that are involved in emotion and stress.
Cortisol (hydrocortisone) is a steroid hormone synthesized and released by the adrenal cortex of the adrenal glands; it is important for normal carbohydrate metabolism and response to stress.
one of two chemicals (the other is norepinephrine) released by the adrenal gland that increases the speed and force of heart beats. It dilates the airways to improve breathing and narrows blood vessels in the skin and intestine so that an increased flow of blood reaches the muscles and allows them to cope with the demands of exercise.
Norepinephrine (Noradrenalin) is the primary neurotransmitter in the sympathetic nervous system. Nervous of this system provides signals to the skin, heart, eyes, lungs, and GI system. Additionally, norepinephrine plays a role in hypertension and insulin resistance.
male sex hormones
A female hormone produced by the ovaries and other adrenal glands
Progesterone is the hormone made by the ovaries that is responsible for the monthly shedding of the uterine lining, which a woman experiences as a menstrual period.
An electrical lead or wire attached to any electronic device or circuit through which current may flow in or out. Produce images of brain
recording through the scalp of electrical potentials from the brain and the changes in these potentials. The EEG is one of the three basic variables (along with the EOG & EMG) used to score sleep stages and waking. Surface electrodes are used to record sleep in humans, recording potential differences between brain regions and a neutral reference point, or between brain regions.
Positron Emission Tomography
A technique used for imaging the brain activity by measuring the flow of blood containing radioactive atoms that emit positrons
(magnetic resonance imaging) (n.) A medical imaging technique used for image capture. Tissue area is simultaneously subjected to electromagnetic radiation and a magnetic field. Sample data slices are gathered and later reconstructed into a composite image for further processing and analysis.
Localization of function
(physiology) the principle that specific functions have relatively circumscribed locations in some particular part or organ of the body
brain stem
The portion of the brain closest to the spinal cord. It consists of the medulla, pons, and midbrain and controls many of the involuntary functions that keep us alive.
Region of the brain that acts as a relay station between the cerebellum and the cerebrum. The pons is part of the brain stem, and it also aids the medulla in the control of breathing.
Also known as the medulla oblongata, this region of the brain is concerned with vital functions like breathing, blood circulation, vomiting, and swallowing.
reticular activating system
a complex network of neurons essential to the regulation of consciousness and to such vital functions as heartbeat and breathing
the lower back part of the brain responsible for functions such as maintaining balance, and coordinating and controlling voluntary muscle movement.
A brain structure that lies between the brain stem and the cortex and acts as a relay to the cortex for almost all sensory inputs and other kinds of information.
olfactory bulb
The olfactory bulb receives and processes smells. It is located very close to the limbic region, which is thought to be the reason that certain smells can activate vivid memories and emotions.
The hypothalamus is the region of the brain which contains several important centers which control body temperature, thirst, hunger, water balance, and sexual function. It is also closely connected with emotional activity and sleep, and functions as a center for the integration of hormonal and autonomic nervous activity through its control of pituitary secretions.
pituitary gland
An endocrine gland in the small, bony cavity at the base of the brain. Often called "the master gland," the pituitary serves the body in many ways-in growth, in food use, and in reproduction.
limbic system
A group of brain structures and their connections with each other as well as their connections with the hypothalamus and other areas. This system is largely associated with emotions.
an almond-shaped group of cells in the temporal lobes of the brain, which is a major part of the limbic system that controls the emotions.
A part of the brain that plays a role in the establishment of new memories.
stabalization before something solidifies
The major part of the brain, occupying the upper part of the cranium, comprised of the two cerebral hemispheres connected by the corpus callosum.
cerebral hemisphere
either half of the cerebrum
corpus callosum
The bundle of neurons that connects the left and right cerebral hemispheres.
asymmetry of brain function; in right-handers, for instance, the left hemisphere is primarily responsible for language, with the right hemisphere doing the visual and spatial tasks.
cerebral cortex
The part of the brain that is visible from the outside. The cerebral cortex is the outermost layer and consists of a collection of nerve cell bodies.
occipital lobes
The rear section of the cortex associated with the visual system
visual cortex
the sensory area of the occipital lobe of the brain’s cerebral cortex receiving afferent projection fibers and concerned with the sense of sight
parietal lobes
Can be divided into two regions. These regions are involved with cognition, information processing, spatial orientation, and the perception of stimuli related to touch, pressure, temperature and pain.
somatosensory cortex
area of the cerebral cortex of the brain to which the sensory signals are sent. The somatic senses include vision, hearing, taste, smell and equilibrium.
temporal lobes
one on each side of the brain located at about the level of the ears. These lobes allow a person to tell one smell from another and one sound from another. They also help in sorting new information and are believed to be responsible for short-term memory. Right Lobe--Mainly involved in visual memory (i.e., memory for pictures and faces). Left Lobe--Mainly involved in verbal memory (i.e., memory for words and names).
auditory cortex
Region of the cortex devoted to the analysis of sound information
Wernick's area
named for Carl Wernicke who first discovered it in 1874, is crucial for language comprehension.
frontal lobes
The part of the cerebrum at the front of the head, responsible for higher thought processes.
motor cortex
The region of the cortex close to the parietal lobes concerned with voluntary muscle movement.
Broca's area
located in the left frontal lobe near the primary motor cortex, is responsible for producing speech that follows the rules of grammar and for understanding complex grammatical structures.
association cortex
one of several areas in the frontal region of the brain, occupying the temporal, occipital and parietal lobes which receives information from sensory cortical areas as well as other association areas.
prefrontal cortex
The part of the cerebral cortex at the very front of the brain. It is involved with higher cognitive and emotional functions including short-term memory, learning, and setting priorities for future actions.
split-brain surgery
cutting the connection between two halves of the brain to reduce epilepsy/seisures.
hemispheric dominance
deals with one brain hemisphere being more dominant over another.

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