Topic 5.3: The Nervous System and the Senses Flashcards
(274 cards)
1
Q
Identify the three classes of neurons and describe their relationship to each other.
A
The three classes of neurons are sensory neurons, which take messages to the CNS; interneurons, which sum up messages from sensory neurons and other interneurons and communicate with motor neurons which take messages away from the CNS to effector organs, muscles, or glands.
2
Q
Describe the three parts of a neuron.
A
Most neurons contain dendrites, a cell body, and an axon.
3
Q
Distinguish the cell types that form the melin in the PNS versus the CNS.
A
Myelin is formed by Schwann cells in the PNS, and by oligodendrocytes in the CNS.
4
Q
Review the structure of gray matter and white matter, and describe where each is found in the CNS and PNS.
A
Gray matter contains nonmyelinated nerve fibers. In white matter, the fibers are myelinated. The brain has gray matter on the surface and white matter in deeper tissue. That pattern is reverse in the spinal cord.
5
Q
Define nervous system.
A
Organ system of humans that includes the brain, spinal cord, sense organs (eyes, ears, etc.), and associated nerves. Receives, integrates, and stores sensory input; coordinates activity of other organ systems.
6
Q
Define central nervous system (CNS)
A
Portion of the nervous system consisting of the brain and spinal cord.
7
Q
Define the peripheral nervous system (PNS)
A
Nerves and ganglia that lie outside the central nervous system.
8
Q
Define neurons
A
Nerve cell that characteristically has three parts: dendrites, cell body, and an axon.
9
Q
Define neuroglia
A
Nonconducting nerve cells that are intimately associated with neurons and that function in a supportive capacity.
10
Q
Define sensory (afferent neuron)
A
Nerve cell that transmits nerve impulses to the central nervous system after a sensory receptor has been stimulated.
11
Q
Define interneuron
A
Neuron located within the central nervous system that conveys messages between parts of the central nervous system.
12
Q
Define motor (efferent neuron)
A
Nerve cell that conducts nerve impulses away from the central nervous system and innervates effectors (muscle and glands).
13
Q
Define cell body
A
Portion of a neuron that contains a nucleus and from which dendrites and an axon extend.
14
Q
Define dendrites
A
Part of a neuron that sends signals toward the cell body.
15
Q
Define axon
A
Elongated portion of a neuron that conducts nerve impulses, typically from the cell body to the synapse.
16
Q
Define myelin sheath
A
White, fatty material—derived from the membrane of neurolemmocytes—that forms a covering for nerve fibers.
17
Q
Define Schwann cell
A
Cell that surrounds a fiber of a peripheral nerve and forms the myelin sheath.
18
Q
Define nodes of Ranvier
A
Gaps in the myelin sheath around a nerve fiber.
19
Q
Define oligodendrocyte
A
Type of glial cell that forms myelin sheaths around neurons in the CNS.
20
Q
Define gray matter
A
Nonmyelinated axons and cell bodies in the central nervous system.
21
Q
Define white matter
A
Myelinated axons in the central nervous system.
22
Q
Define tracts
A
Bundle of myelinated axons in the central nervous system.
23
Q
Describe the activity of the sodium-potassium pump present in neurons.
A
The sodium-potassium pumps in neurons, are always transporting Na+ to the outside, and K= to the inside of the cell.
24
Q
Explain how the changes in Na+ and K+ ion concentrations that occur during and action potential are associated with depolarization and repolarization.
A
During an action potential, the Na+ gates open and Na+ enters the cell, causing a depolarization. Then, the Na+ gates close and the K+ gates open, causing a repolarization (even a slight hyperpolarization).
25
Explain how the nerves impulse is transmitted across a synapse.
1. After an action potential arrives at an axon terminal, Ca2+ enters, and synaptic vesicles fuse with the presynaptic membrane.
2. Neurotransmitter molecules are released and bind to receptors on the postsynaptic membrane.
3. When an excitatory neurotransmitter binds to a receptor, Na+ diffuses into the postsynaptic neuron, and an action potential begins.
26
Define refractory period, saltatory conduction, and synaptic integration.
After the action potential passes one part of an axon, the sodium gates in that part are unable to open for a period of time, called the refractory period. This prevents action potentials from moving backward. A node of Ranvier is a gap between Schwann cells that make up the myelin sheath of an axon of a PNS neuron. Saltatory conduction is the "jumping" of action potentials as they spread from node to node. Synaptic integration is the summing up of all incoming excitatory and inhibitory messages by a neuron.
27
Define nerve impulse
Electrical signal that conveys information along the length of a neuron.
28
Define resting potential
Membrane potential of an inactive neuron.
29
Define sodium-potassium pump
Carrier protein in the plasma membrane that moves sodium ions out of, and potassium ions into, cells; important in the function of nerve and muscle cells in animals.
30
Define action potential
Electrochemical changes that take place across the axon membrane; the nerve impulse.
31
Define refractory period
Time following an action potential when a neuron is unable to conduct another nerve impulse.
32
Define saltatory conduction
Movement of nerve impulses from one node to another along a myelinated axon.
33
Define synapse
Junction between neurons consisting of the presynaptic (axon) membrane, the synaptic cleft, and the postsynaptic (usually dendrite) membrane.
34
Define synaptic cleft
Small gap between presynaptic and postsynaptic cells of a synapse.
35
Define neurotransmitters
Chemical stored at the ends of axons that is responsible for transmission across a synapse.
36
Define integration
Summing up of excitatory and inhibitory signals by a neuron or by some part of the brain.
37
Describe the interaction of the CNS and PNS.
The CNS is composed of the spinal cord and the brain. The PNS, which lies outside of the SNS, is composed of nerves and ganglia. Sensory fibers send information to the NS, and motor fibers conduct information away from the CNS to tissues and organs. Ganglia are areas of nerves that are collections of cell bodies.
38
Summarize the functions of the spinal cord.
The spinal cord is structured so that the brain can communicate with the peripheral nerves. The communication involves sensory and motor functions.
39
Identify the four major parts of the brain and describe the general functions of each.
Cerebrum: receives sensory information, integrates it, and commands voluntary motor responses. Diencephalon has two parts: hypothalamus serves as a link between the nervous and endocrine system, maintaining homeostasis; thalamus receives sensory inputs except for smell. Cerebellum: processes information about body position and maintains posture and balance. Brain stem: acts as a relay between the cerebrum and spinal cord or cerebellum; regulates breathing through the pons; regulates vital functions through the medulla oblongata; receives and sends signals between the higher brain centers and the spinal cord.
40
Define meninges.
Protective membranous coverings around the central nervous system.
41
Define cerebrospinal fluid
Fluid found in the ventricles of the brain, in the central canal of the spinal cord, and in association with the meninges.
42
Define ventricles
Cavity in an organ, such as a lower chamber of the heart or the ventricles of the brain.
43
Define spinal cord
In vertebrates, the nerve cord that is continuous with the base of the brain and housed within the vertebral column.
44
Define the brain
Ganglionic mass at the anterior end of the nerve cord; in vertebrates, the brain is located in the cranial cavity of the skull.
45
Define cerebrum
Largest part of the brain in mammals.
46
Define cerebral hemispheres
Either of the two lobes of the cerebrum in vertebrates.
47
Define cerebral cortex
Outer layer of cerebral hemispheres; receives sensory information and controls motor activities.
48
Define basal nuclei
Subcortical nuclei deep within the white matter that serve as relay stations for motor impulses and produce dopamine to help control skeletal muscle activities.
49
Define hypothalamus
In vertebrates, part of the brain that helps regulate the internal environment of the body—for example, heart rate, body temperature, and water balance.
50
Define thalamus
In vertebrates, the portion of the diencephalon that passes on selected sensory information to the cerebrum.
51
Define pineal gland
Gland—either at the skin surface (fish, amphibians) or in the third ventricle of the brain (mammals)—that produces melatonin.
52
Define cerebellum
In terrestrial vertebrates, portion of the brain that coordinates skeletal muscles to produce smooth, graceful motions.
53
Define brain stem
In mammals, portion of the brain consisting of the medulla oblongata, pons, and midbrain.
54
Define midbrain
In mammals, the part of the brain located below the thalamus and above the pons.
55
Define pons
Portion of the brain stem above the medulla oblongata and below the midbrain; assists the medulla oblongata in regulating the breathing rate.
56
Define medulla oblongata
In vertebrates, part of the brain stem that is continuous with the spinal cord; controls heartbeat, blood pressure, breathing, and other vital functions.
57
Define reticular activating system (RAS)
Area of the brain that contains the reticular formation; acts as a relay for information to and from the peripheral nervous system and higher processing centers of the brain.
58
Summarize the role of the major structure of the limbic system in memory.
The hippocampus within the limbic system is involved in learning and memory. It communicates with the prefrontal area o the brain in these functions.
59
Discuss why two forms of memory are needed by the body.
Short-term memory is useful in managing operations within the present by holding a thought in mind. Long-term memory involves semantic and episodic memory, as well as skill memory. It allows recall of the past and use of that information to shape future actions.
60
Summarize the evidence from the mouse study that showed the role of glutamate in memory formation.
Mice that lack a glutamate receptor in their hippocampus were unable to learn to run mazes.
61
Describe the specific functions of Broca's and Wernicke's areas.
Wernicke's area is involved in the comprehension of speech. Broca's area is involved in the actual motor function of speech.
62
1. Which of the following neuron parts receive(s) signals from sensory receptors of other neurons?
a) cell body
b) axon
c) dendrites
d) both a and c
d) both a and c
63
2. The neuroglia cells that form myelin sheaths in the CNS are called
a) oligodendrocytes
b) ganglionic cells
c) Schwann cells
d) astrocytes
e) microglia
a) oligodendrocytes
64
7. Which of the following cerebral areas is not correctly matched with its function?
a) occipital lobe- vision
b) parietal lobe- somatosensory area
c) temporal lobe- primary motor area
d) frontal lobe- Broca's motor speech area
c) temporal lobe- primary motor area
65
8. This part of the brain forms the link between the nervous system and the endocrine system
a) corpus callosum
b) amygdala
c) reticular formation
d) hypothalamus
d) hypothalamus
66
9. The cerebellum
a) coordinates skeletal muscle movements
b) receives sensory input from the joints and muscles
c) receives motor output from the cerebral cortex
d) all of the above
d) all of the above
67
10. The regulation of the information that is to be relayed to memory is the function of the
a) reticular formation
b) hippocampus
c) hypothalamus
d) cerebellum
e) pons
b) hippocampus
68
11. Memories are stored in the sensory association areas of the
a) cerebral cortex
b) spinal cord
c) brain stem
d) hypothalamus
a) cerebral cortex
69
Describe how interoceptors are often involved in homeostasis.
Interoceptors are involved in regulating critical body functions like blood pressure, blood volume, and blood pH.
70
List a specific example of each of the four types of sensory receptors.
Chemoreceptors-taste and smell
Photoreceptors- vision
Mechanoreceptors- hearing and balance
Thermoreceptors- heat and cold
71
Explain why sensory adaptation is important to an organism.
Without sensory adaptation, we would constantly be stimulated by all sorts of inputs, which could overwhelm the brain's ability to interpret.
72
Define sensory receptor
Structure that receives either external or internal environmental stimuli and is a part of a sensory neuron or transmits signals to a sensory neuron.
73
Define interoceptor
Sensory receptors of the peripheral nervous system that detect stimuli from inside the body.
74
Define exteroceptor
Sensory receptors of the peripheral nervous system that detect stimuli from outside the body.
75
Define chemoreceptor
Sensory receptor that is sensitive to chemical stimulation—for example, receptors for taste and smell.
76
Define photoreceptor
Sensory receptor that responds to light stimuli.
77
Define mechanoreceptor
Sensory receptor that responds to mechanical stimuli, such as pressure, sound waves, or gravity.
78
Define thermoreceptor
Sensory receptor that detects heat.
79
Define sensation
Processing of sensory stimuli that involves detection of nerve impulses by the cerebral cortex of the brain.
80
Define perception
Processing of sensory stimuli that occurs when the brain interprets information being received from the sensory receptors.
81
Define sensory transduction
Process by which a sensory receptor converts an input to a nerve impulse.
82
Define integration
Summing up of excitatory and inhibitory signals by a neuron or by some part of the brain.
83
Define sensory adaptation
Change in the sensitivity of a receptor that usually makes the receptor less sensitive to its stimulus.
84
Explain the role, and specific location, of mechanoreceptors involved in maintain balance and equilibrium.
a) Rotational equilibrium. The ampullae of the semicircular canals contain hair cells with stereocilia embedded in a cupula. When the head rotates, the cupula is displaced, bending the stereocilia. This sends nerve impulses via the vestibular nerve to the brain.
b) Gravitational equilibrium. The utricle and the saccule contain hair cells with stereocilia embedded in an otolithic membrane. When the head bends, otoliths are displaced, causing the membrane to sag and the stereocilia to bend. The direction the stereocilia bend tells the brain in which direction the head moved.
85
Classify each of the following as being associated with either the semicircular canals or the vestibule: ampulla, cupula, otoliths, saccule, and utricle.
The ampulla and cupula are associated with the semicircular canals; the otoliths, saccule, and utricle are associated with the vestibule.
86
Explain how having two separate systems for equilibrium provided more complete information than one system could.
Having two systems for equilibrium allows the brain to receive information about rotational movement from the semicircular canals, and about the body's position at rest from the vestibule. Although it might be possible to distinguish between these with just one system, it would not be as efficient or sensitive.
87
Define rotational equilibrium
Maintenance of balance when the head and body are suddenly moved or rotated.
88
Define gravitational equilibrium
Maintenance of balance when the head and body are motionless.
89
Define utricle
Cavity in the vestibule of the vertebrate inner ear; contains sensory receptors for gravitational equilibrium.
90
Define saccule
Saclike cavity in the vestibule of the vertebrate inner ear; contains sensory receptors for gravitational equilibrium.
91
Define otolith
Calcium carbonate granule associated with sensory receptors for detecting movement of the head; in vertebrates, located in the utricle and saccule.
92
Classify which specific types of somatic sensory receptors are interoceptors and which are exteroceptors.
Somatic sensory receptors that are interoceptors include proprioceptors (such as muscle spindles and Golgi tendon organs), and pain receptors in the skin and internal organs. Somatic sensory receptors that are exteroceptors include cutaneous receptors like Meissner corpuscles, Krause end bulbs, Merkel disks, Pacinian corpuscles, Ruffini endings, and free nerve endings sensitive to temperature.
93
Classify the cutaneous receptors by their location (i.e., in the dermis or epidermis).
Free nerve endings- pain, heat, cold
Merkel disks- touch
Krause end bulbs- touch
Root hair plexus- touch
Meissner corpuscles- touch
Pacinian corpuscles- pressure
Riffini endings- pressure
94
Predicts the likely outcome if an individual lacked muscle spindles; or pain receptors.
Someone who lacks muscle spindles would be susceptible to injuring their muscles and joints due to a lack of awareness of limb position and degree of muscle contraction. A person who lacked pain receptors would be without the benefit of the protective function of pain and would be very prone to injury.
95
Define proprioceptors
Class of mechanoreceptor responsible for maintaining the body’s equilibrium and posture; involved in reflex actions.
96
Define cutaneous receptors
Sensory receptor of the dermis that is activated by touch, pain, pressure, and temperature.
97
Define pain receptors
Sensory receptors that are sensitive to chemicals released by damaged cells; also called nociceptors.
98
Compare and contrast the functions of the chemoreceptors on the tongue and in the nasal cavity.
The tongue has taste cells and the nasal cavity has olfactory cells. Both are chemoreceptors to which molecules bind and nerve impulses are sent to the brain. The tongue has five types of taste cells distributed over the tongue, while there are about 1000 different types f olfactory cells in the olfactory epithelium.
99
Predict some structural variations that could provide certain animals, such as dogs, with a sense of smell thousands o times more sensitive than that of humans.
Adaptations that allow some animals to have a more sensitive sense of smell would unclude having a greater number of olfactory receptors (and increased space in the nasal cavity for these receptors) and having more sensory nerve axons to receive signals from these receptors.
100
Describe the anatomical connections that exist in the brain between smells and memories.
The olfactory bulbs in the brain have direct connections to centers for memory in the limbic system.
101
Define taste buds.
Structure in the vertebrate mouth containing sensory receptors for taste; in humans, most taste buds are on the tongue.
102
Define olfactory cells
Modified neuron that is a sensory receptor for the sense of smell.
103
List all tissues that light passes through from when it enters the eye until it is converted into a nerve impulse.
Conjunctiva, cornea, aqueous humor in the anterior compartment, through the iris, lens, vitreous humor in the posterior compartment, retina including the ganglion cell layer, bipolar cell layer, and finally the rod cell and cone cell layer where light is converted to nerve impulses.
104
Describe how the ciliary muscle controls the shape of the lens.
When the ciliary muscle is relaxed, the suspensory ligaments that attach to the lens are taut, which causes the lens to become flatter. When the ciliary muscle contracts, the suspensory ligaments are relaxed, allowing the lens to become more round.
105
Explain how the number of rod or cone cells synapsing on a single ganglion cell allows cones to produce a clearer image.
As many as 150 rod cells, but perhaps only one cone cell, synapse(s) on an individual ganglion cell, so that more information can be sent to the brain for an individual cone cell versus a rod cell.
106
Describe how the anatomy of the optic chiasma implies that the brain interprets visual information that has been "split" in half.
The optic chiasma is X-shaped, formed by the optic nerve fibers crossing over. The image sent to the brain is split because one side of the optic tract carries information about the opposite side of the visual field. The two sides of the visual field must communicate with each other in the brain for perception of the entire visual field.
107
Define sclera
White, fibrous, outer layer of the eyeball.
108
Define cornea
Transparent, anterior portion of the outer layer of the eyeball.
109
Define conjunctiva
Delicate membrane that lines the eyelid, protecting the sclera.
110
Define choroid
Vascular, pigmented middle layer of the eyeball.
111
Define iris
Muscular ring that surrounds the pupil and regulates the passage of light through this opening.
112
Define pupil
Opening in the center of the iris of the vertebrate eye.
113
Define ciliary muscle
Within the ciliary body of the vertebrate eye, the ciliary muscle controls the shape of the lens.
114
Define lens
Transparent “disk” structure found in the vertebrate eye behind the iris; brings objects into focus on the retina.
115
Define retina
Innermost layer of the vertebrate eyeball, containing the photoreceptors—rod cells and cone cells.
116
Define fovea centralis
Region of the retina consisting of densely packed cones; responsible for the greatest visual acuity.
117
Define visual accommodation
Ability of the eye to focus at different distances by changing the curvature of the lens.
118
Define rod cells
Photoreceptor in vertebrate eyes that responds to dim light.
119
Define cone cells
Photoreceptor in vertebrate eyes that responds to bright light and makes color vision possible.
120
Rhodopsin
Light-absorbing molecule in rod cells and cone cells that contains a pigment and the protein opsin.
121
Define retinal
Light-absorbing molecule found in the photoreceptors of the eye; usually combined with opsin to form rhodopsin.
122
Define color vision
Ability of the eye to detect specific wavelengths of light; involves specialized cone cells that detect blue, green, and red wavelengths.
123
Define blind spot
Region of the retina, lacking rods or cones, where the optic nerve leaves the eye.
124
Identify all structures of the ear that are involved with hearing and describe their functions.
Sound waves travel down the auditory canal to the tympanic membrane, and then to the bones of the middle ear, which are connected to the cochlea in the inner ear. It is in the cochlea that the sound waves are converted to neural impulses that are transmitted to the brain.
125
Where are the mechanoreceptors in the inner ear that transduce sound waves into nerve impulses located?
The mechanoreceptors responsible for transducing sound waves into nerve impulses are located on hair cells on the basilar membrane of the spiral organ in the cochlea of the inner ear.
126
Discuss how the distribution off stereocilia along the spiral organ allows the brain to perceive different pitches.
Sound waves transmitted via the oval window cause the basilar membrane to vibrate. Near the tip of the spiral organ, the basilar membrane vibrates more in response to higher pitched sound, and at the base it responds to lower pitches. Different sensory nerves supply each part of the basilar membrane, and take information to different part of the auditory cortex, where the pitch is interpreted.
127
Explain how the brain distinguishes the volume of a sound.
Loud sounds cause the basilar membrane to vibrate more rapidly, which is interpreted by the brain as volume.
128
Define hair cells
Cells located in the inner ear that function as mechanoreceptors for hearing.
129
Define outer ear
Portion of the ear consisting of the pinna and the auditory canal.
130
Define pinna
External flap of the ear; serves to collect and funnel sound toward the middle ear.
131
Define auditory canal
Structure that funnels sounds from the outer ear to the middle ear.
132
Define middle ear
Portion of the ear consisting of the tympanic membrane, the oval and round windows, and the ossicles, where sound is amplified.
133
Define tympanic membrane
Membranous region that receives air vibrations in an auditory organ; in humans, the eardrum.
134
Define oval window
Structure of the middle ear that conducts sound from the middle ear to the inner ear.
135
Define round window
Structure of the middle ear that assists in the transmission of sound from the middle ear to the inner ear.
136
Define ossicles
The small bones of the vertebrate middle ear—malleus, incus, and stapes.
137
Define malleus
Bone found in the middle ear that assists in the transmission of sound to the inner ear; also called the hammer.
138
Define incus
Bone found in the middle ear that assists in the transmission of sound to the inner ear; also called the anvil.
139
Define stapes
Bone found in the middle ear that assists in the transmission of sound to the inner ear; also called the stirrup.
140
Define auditory tube
Also called the eustachian tube; connects the middle ear to the nasopharynx for the equalization of pressure.
141
Define inner ear
Portion of the ear consisting of a vestibule, semicircular canals, and the cochlea where equilibrium is maintained and sound is transmitted.
142
Define semicircular canal
One of three half-circle-shaped canals of the vertebrate inner ear; contains sensory receptors for rotational equilibrium.
143
Define vestibule
Space or cavity at the entrance to a canal, such as the cavity that lies between the semicircular canals and the cochlea.
144
Define cochlea
Spiral-shaped structure of the vertebrate inner ear containing the sensory receptors for hearing.
145
Define organ of Corti
Structure in the vertebrate inner ear that contains auditory receptors (also called spiral organ).
146
These receptors detect stimuli within the body.
a) interoceptors
b) exteroceptors
c) homeoreceptors
d) reflec receptors
a) interoceptors
147
A receptor that detects changes in pH, or specific molecules in the environment, would be classifies as a
a) mechanoreceptor
b) photoreceptor
c) chemoreceptor
d) thermoreceptor
e) none of the above
c) chemoreceptor
148
Where does the process of sensation occur in the body?
a) at the sensory receptor
b) in the spinal cord
c) within the synapses between neurons of the PNS
d) in the cerebral cortex
e) all of the above
d) in the cerebral cortex
149
Which type of receptor detect the chemicals released by damaged tissues?
a) nociceptors
b) proprioceptors
c) Meissner corpuscles
d) Ruffini endings
e) None of the above
a) nociceptors
150
Which of the following types of receptors assists in the maintenance of muscle tone?
a) nociceptors
b) proprioceptors
c) Pacinian corpuscles
d) Krause end bulbs
e) all of the above
b) proprioceptors
151
The sense of taste and smell rely primarily on what types of receptors?
a) mechanoreceptors
b) nociceptors
c) protoreceptors
d) proprioceptors
e) chemoreceptors
e) chemoreceptors
152
7. Olfactory bulbs are located
a) on the tongue
b) in the nasal cavity
c) in the brain stem
d) in the aorta
e) none of the above
b) in the nasal cavity
153
9. Which structure of the eye is incorrectly matched with its function
a) lens-focusing
b) cones-color vision
c) iris-regulation of amount of light
d) choroid- location of cones
e) sclera- protection
d) choroid- location of cones
154
10. Adjustment of the lens to focus on objects close to the viewer is called
a) convergence
b) focusing
c) visual accommodation
d) constriction
c) visual accommodation
155
12. Which of the following is (are) not involved in the sense of hearing
a) auditory canal
b) tympanic membrane
c) ossicles
d) semicircular canals
e) cochlea
d) semicircular canals
156
Which of these correctly describes the location of the spiral organ?
a) between the tympanic membrane and the oval window in the inner ear
b) in the utricle and saccule within the vestibule
c) between the tectorial membrane and the basilar membrane in the cochlear canal
d) between the nasal cavities and the throat
e) between the outer and inner ear within the semicircular canals
c) between the tectorial membrane and the basilar membrane in the cochlear canal
157
Which of the following structures would allow you to know that you were upside down, even if you were in total darkness?
a) utricle and saccule
b) cochlea
c) semicircular canals
d) tectorial membrane
a) utricle and saccule
158
Rotational equilibrium is established by which of the following?
a) the semicircular canals
b) the utricle and saccule
c) the cochlea
d) the auditory canal
e) none of the above
a) the semicircular canals
159
Some sensory receptors, such as those for taste, smell, and pressure, readily undergo the process of sensory adaptation, or decreased response to stimulus. In contrast, receptors for pain are less prone too adaptation. Why does this make good biological sense? What do you think happens to children who are born without the ability to feel pain normally?
Without sensory adaptation to constant everyday stimuli, we would constantly be bombarded with and distracted by a huge amount of sensory data ( about touch, temperature, pressure, etc.). In contrast, there are large risks forgo not responding to pain, as shown by the damage that occurs to people who lack pain perception.
160
Trace the path of a photon of light through all the layers of the retina discussed in this chapter. Then, trace the nerve impulse from a photoreceptor located on the right side of the left eyeball through the visual cortex.
Once it reaches the retina, light must pass through layers of axons, ganglion cells, and bipolar cells before it reaches the rod or cone cells. From the right side of the left eyeball, nerve impulses travel via the optic nerve through the optic chiasma, then through the right optic tract, until they synapse with neurons in the thalamus. Axons from thalamic neurons transmit this information to the visual area of the occipital cortex.
161
The density of taste buds on the tongue can vary. Some obese individuals have a lower density of taste buds than usual. Assume that taste perception is related to taste bud density. If so, what hypothesis would you test to see if there is a relationship between taste bud density and obesity.
The null hypothesis would be that there is no association with taste bud density and obesity. The prediction based on this hypothesis is that obese people will have the same density as normal weight people.
162
List 6 major human endocrine organs
Hypothalamus, pituitary gland, thyroid gland, adrenal glands, thymus, and pancreas.
163
Explain what it means to say that secretion o a hormone is regulated by negative feedback.
When an endocrine gland is controlled by negative feedback, it is sensitive to the condition it is regulating or the blood level of the hormone it is producing.
164
Explain why second messengers are needed for peptide hormones.
Peptide hormones bind to receptors in the plasma membrane and do not enter the cell. A second messenger inside the cell is needed to initiate an enzyme cascade.
165
Provide a specific example that suggests human behavior may be influenced by pheromones.
It has been found that women prefer axillary odors from men with different MHC than themselves.
166
Define endocrine system
Organ system involved in the coordination of body activities; uses hormones as chemical signals secreted into the bloodstream.
167
Define hormones
Chemical messenger, produced in one part of the organism, that controls the activity of other tissues or organs in that organism.
168
Define growth factors
A hormone or chemical, secreted by one cell, that may stimulate or inhibit growth of another cell or cells.
169
Define endocrine glands
Ductless organ that secretes hormone(s) into the bloodstream.
170
Define negative feedback
Mechanism of homeostatic response by which the output of a system suppresses or inhibits activity of the system.
171
Peptide hormone
Type of hormone that is a protein, a peptide, a glycoprotein, or is derived from an amino acid.
172
Define steroid hormone
Type of hormone that has a complex of 4-carbon rings, but each one has different side chains.
173
Define first messenger
Chemical signal, such as a peptide hormone, that binds to a plasma membrane receptor protein and alters the metabolism of a cell because a second messenger is activated.
174
Define second messenger
Chemical signal, such as cyclic AMP, that causes the cell to respond to the first messenger—a hormone bound to a plasma membrane receptor protein.
175
Define pheromones
Chemical messenger that works at a distance and alters the behavior of another member of the same species.
176
Explain how the posterior and anterior pituitary glands differ in the way they are controlled by the hypothalamus.
Neurons in the hypothalamus produce hormones that pass through axons into the posterior pituitary where they are stored. The hypothalamus controls the anterior pituitary by producing hormones that travel to the anterior pituitary through a portal system.
177
List the hormones produced or released by the pituitary gland, and provide a function for each.
Antidiuretic (ADH)- Stimulates water reabsorption by kidneys
Oxytocin- Stimulates uterine muscle contraction, release of milk by mammary glands
Thyroid-Stimulating (TSH)- Stimulates thyroid
Adrenocorticotropic (ACTH)- Stimulates adrenal cortex
Gonadotropic (FSH,LH)- Egg and sperm production; sex hormone production
Prolactin (PRL)- Milk production
Growth (GH)- Cell division, protein synthesis, and bone growth
Melanocyte-stimulating (MSH)- Unknown function in humans; regulates skin color in lower vertebrates
178
Describe how hormone secretion can be regulated by positive feedback, and provide an example.
The release of oxytocin from the posterior pituitary is controlled by positive feedback in which the amount of oxytocin released increases as the stimulus continues.
179
Explain why cancer of the pituitary gland, which may affect any of its normal functions, might be difficult to diagnose.
Diagnosis is difficult because of the many hormones controlled by the pituitary and the many organs and tissues affected.
180
Define hypothalamus
In vertebrates, part of the brain that helps regulate the internal environment of the body—for example, heart rate, body temperature, and water balance.
181
Define pituitary gland
Small gland that lies just inferior to the hypothalamus; consists of the anterior and posterior pituitary, both of which produce hormones.
182
Define antidiuretic hormone (ADH)
Hormone, secreted by the posterior pituitary, that increases the permeability of the collecting ducts in a kidney.
183
Define posterior pituitary
Portion of the pituitary gland that stores and secretes oxytocin and antidiuretic hormone produced by the hypothalamus.
184
Define oxytocin
Hormone, released by the posterior pituitary, that causes contraction of the uterus and milk letdown.
185
Define positive feedback
Mechanism of homeostatic response in which the output of the system intensifies and increases the activity of the system.
186
Define hypothalamic-releasing hormone
One of many hormones, produced by the hypothalamus, that stimulates the secretion of an anterior pituitary hormone.
187
Define hypothalamic-inhibiting hormone
One of many hormones, produced by the hypothalamus, that inhibits the secretion of an anterior pituitary hormone.
188
Define anterior pituitary
Portion of the pituitary gland that is controlled by the hypothalamus and produces six types of hormones, some of which control other endocrine glands.
189
Define thyroid-stimulating hormone (TSH)
Substance produced by the anterior pituitary that causes the thyroid to secrete thyroxine and triiodothyronine.
190
Define adrenocorticotropic hormone (ACTH)
Hormone secreted by the anterior lobe of the pituitary gland that stimulates activity in the adrenal cortex.
191
Define follicle-stimulating hormone (FSH)
Hormone released by the anterior pituitary; in males, it promotes the production of sperm; in females, it promotes the development of the follicle in the ovary.
192
Define luteinizing hormone (LH)
Hormone released by the anterior pituitary; in males, it regulates the production of testosterone by the interstitial cells; in females, it promotes the development of the corpus luteum in the ovary; also called interstitial cell-stimulating hormone (ICSH) in males.
193
Define gonadotropic hormone
Substance, secreted by the anterior pituitary, that regulates the activity of the ovaries and testes; principally, follicle-stimulating hormone (FSH) and luteinizing hormone (LH).
194
Define prolactin
Hormone secreted by the anterior pituitary that stimulates the production of milk from the mammary glands.
195
Define melanocyte-stimulating hormone (MSH)
Substance that causes melanocytes to secrete melanin in most vertebrates.
196
Define growth hormone (GH)
Substance secreted by the anterior pituitary; controls size of an individual by promoting cell division, protein synthesis, and bone growth.
197
Explain how the amount of T3 and T4 secreted by the thyroid gland is controlled.
Levels of T3 and T4 are controlled by negative feedback. When levels of T3 and T4 rise, the anterior pituitary stops producing thyroid-stimulating hormone.
198
Describe the symptoms that might be expected in a person with a thyroid tumor that was producing excess calcitonin.
Calcitonin decreases blood calcium by increasing calcium deposition in bones. A person with a calcitonin-producing thyroid tumor would be expected to have low calcium levels, leading to disrupted nerve conduction, muscle contraction, and blood clotting, as well as increased bone density.
199
Predict the expected effect(s) of removal of the parathyroid glands.
Parathyroid hormone increases the activity of osteoclasts, promotes reabsorption of calcium by the kidneys, causes blood phosphate to decrease, and activates vitamin D, so removal of the parathyroid glands would tend to cause decreased blood calcium and increased blood phosphate.
200
Define thyroid gland
Large gland in the neck that produces several important hormones, including thyroxine, triiodothyronine, and calcitonin.
201
Define parathyroid gland
Gland embedded in the posterior surface of the thyroid gland; it produces parathyroid hormone.
202
Define thyroxine (T4)
Hormone secreted from the thyroid gland that promotes growth and development; in general, it increases the metabolic rate in cells.
203
Define calcitonin
Hormone secreted by the thyroid gland that increases the blood calcium level.
204
Define parathyroid hormone (PTH)
Hormone secreted by the four parathyroid glands that increases the blood calcium level and decreases the phosphate level.
205
Explain how the secretion of hormones by the adrenal medulla and cortex is controlled.
Secretion of hormones by the adrenal medulla is under direct nervous control. Secretions of the adrenal cortex are controlled either by the release of ACTH from the anterior pituitary (for glucocorticoids) or by the renin-angiotensin system (for mineralcorticoids).
206
Summarize how the hormones produced by the adrenal glands help the body respond to stress.
Epinephrine from the adrenal medulla helps the body deal with stress by activating the fight-or-flight response (increased heart rate, blood pressure, and energy level). Glucocorticoids from the adrenal cortex raise blood glucose levels and inhibit the body's inflammatory response.
207
Describe the specific effect of aldosterone on the kidney.
Aldosterone causes the kidneys to absorb sodium and excrete potassium, which generally raises blood pressure.
208
Define adrenal gland
Gland that lies atop a kidney; the adrenal medulla produces the hormones epinephrine and norepinephrine, and the adrenal cortex produces the glucocorticoid and mineralocorticoid hormones.
209
Define adrenal medulla
Inner portion of the adrenal gland; secretes the hormones epinephrine and norepinephrine.
210
Define adrenal cortex
Outer portion of the adrenal gland; secretes mineralocorticoids, such as aldosterone, and glucocorticoids, such as cortisol.
211
Define epinephrine
Hormone secreted by the adrenal medulla in times of stress; also referred to as adrenaline.
212
Define norepinephrine
Neurotransmitter of the postganglionic fibers in the sympathetic division of the autonomic system; also, a hormone produced by the adrenal medulla. Sometimes referred to as noradrenaline.
213
Define mineralocorticoid
Hormone secreted by the adrenal cortex that regulates salt and water balance, leading to increases in blood volume and blood pressure.
214
Define gluccorticoid
Type of hormone secreted by the adrenal cortex that influences carbohydrate, fat, and protein metabolism; see also cortisol.
215
Define cortisol
Glucocorticoid secreted by the adrenal cortex that responds to stress on a long-term basis; reduces inflammation and promotes protein and fat metabolism.
216
Define aldosterone
Hormone secreted by the adrenal cortex that regulates the sodium and potassium ion balance of the blood.
217
Define renin
Enzyme released by the kidneys that leads to the secretion of aldosterone and a rise in blood pressure.
218
Define atrial natriuretic hormone (ANH)
Hormone secreted by the heart that increases sodium excretion by inhibiting the secretion of aldosterone.
219
Distinguish between the endocrine and exocrine functions of the pancreas.
The exocrine tissue of the pancreas produces and secretes juices that help in digestion in the small intestine. The endocrine cells of the pancreas produce the hormones glucagon, insulin, and somatostatin.
220
Describe how pancreatic hormones interact to regulate blood glucose levels.
When the blood glucose level is high, the pancreas secretes insulin. Insulin promotes the storage of glucose as glycogen and the synthesis of proteins and fats (as opposed to their use as energy sources). Therefore, insulin lower the blood glucose level to normal.
When the blood glucose level is low, the pancreas secretes glucagon. Glucagon acts opposite to insulin. Therefore, glucagon raises the blood glucose level to normal.
221
Review the effect of somatostatin on other hormones, such as insulin and glucagon.
Somatostatin inhibits the release of growth hormone and suppresses glucagon and insulin secretion by negative feedback mechanism.
222
Define pancreas
Internal organ that produces digestive enzymes and the hormones insulin and glucagon.
223
Define pancreatic islet
Masses of cells that constitute the endocrine portion of the pancreas.
224
Define insulin
Hormone, released by the pancreas, that serves to lower blood glucose levels by stimulating the uptake of glucose by cells, especially muscle and liver cells.
225
Define glucagon
Hormone, produced by the pancreas, that stimulates the liver to break down glycogen, thus raising blood glucose levels.
226
Define somatostatin
Hormone, produced by the pancreas, stomach, and small intestine, that inhibits the effects of growth hormones; also suppresses activity of hormones such as insulin and glucagon.
227
Summarize the role of testosterone and estrogen in the body.
Testosterone and estrogen stimulate the development of male and female sex characteristics and the production of gametes.
228
List some of the undesirable side effects of anabolic steroid use.
Some of the worst side effects from taking anabolic steroids are liver disfunction and cancer, kidney disease, heart damage, stunted growth, infertility, and impotency.
229
Describe the normal function of leptin.
Leptin signals satiety, a sense of not being hungry.
230
Explain why prostaglandins are considered to be local hormones.
Prostaglandins are not distributed in the blood, but instead act close to where they are produced within cells.
231
Define gonads
Organ that produces gametes; the ovary produces eggs, and the testis produces sperm.
232
Define testes
Male gonads that produce sperm and the male sex hormones.
233
Define androgens
Male sex hormone (e.g., testosterone).
234
Define ovaries
In flowering plants, the enlarged, ovule-bearing portion of the carpel that develops into a fruit; female gonad in animals that produces an egg and female sex hormones.
235
Define anabolic steroid
Synthetic steroid that mimics the effect of testosterone.
236
Define estrogen
Female sex hormone that helps maintain sexual organs and secondary sex characteristics.
237
Define progesterone
Female sex hormone that helps maintain sexual organs and secondary sex characteristics.
238
Define thymus
Lymphoid organ involved in the development and functioning of the immune system; T lymphocytes mature in the thymus.
239
Define pineal gland
Gland—either at the skin surface (fish, amphibians) or in the third ventricle of the brain (mammals)—that produces melatonin.
240
Define melatonin
Hormone, secreted by the pineal gland, that is involved in biorhythms.
241
Define circadian rhythm
Biological rhythm with a 24-hour cycle.
242
Define leptin
Hormone produced by adipose tissue that acts on the hypothalamus to signal satiety (fullness).
243
Define growth factor
A hormone or chemical, secreted by one cell, that may stimulate or inhibit growth of another cell or cells.
244
Define prostaglandin
Hormone that has various and powerful local effects.
245
Explain how ADH is related to an increased urge to urinate when one drinks alcohol.
ADH causes more water to be reabsorbed in the kidneys, decreasing urine volume. Inhibition of ADH secretion by alcohol results in increased amounts of urine and frequency of urination.
246
Describe why a goiter forms in iodine deficiency.
In iodine deficiency, the thyroid gland cannot synthesize enough T3 and T4. The anterior pituitary responds by releasing large amounts of TSH, which stimulates the thyroid gland to enlarge.
247
Differentiate the role of antibodies in causing Graves disease versus Addison disease.
In Addison disease, antibodies play a role in destruction of the adrenal cortex by the immune system. In Graves disease, antibodies bind to the TSH receptor, stimulating production of T3 and T4 rather than destroying the gland.
248
Describe the causes and treatment of type 1 and type 2 diabetes.
Type 1 diabetes is due to an insulin shortage and is treated by the administration of insulin. Type 2 results from an insensitivity to insulin, often specifically due to insufficient numbers of insulin receptors on cells. It is treated with medications, weight loss, and increased exercise.
249
Define diabetes insipidus
Condition caused by a lack of antidiuretic hormone (ADH); characterized by excessive thirst and overproduction of urine.
250
Define pituitary dwarfism
Condition caused when too little growth hormone is produced during childhood. Individuals with this condition have a small stature, but have body parts in normal proportions.
251
Define gigantism
Condition caused by the overproduction of growth hormone during childhood; individuals often also have diabetes mellitus and other health problems.
252
Define acromegaly
Condition caused by an overproduction of growth hormones as an adult.
253
Define Cushing syndrome
Condition caused by the overproduction of ACTH, resulting in too much cortisol in the body.
254
Define hypothyroidism
Caused by the under-secretion of hormones from the thyroid gland; symptoms include weight gain, lethargic behavior, and depression.
255
Define hypothyroidism
Caused by the oversecretion of hormones from the thyroid gland; symptoms include hyperactivity, nervousness, and insomnia.
256
Define Graves disease
Disease associated with the overproduction of T3 and T4 by the thyroid; caused by antibodies that interact with TSH receptors in the thyroid.
257
Define Addison disease
Condition caused by an insufficient production of cortisol by the adrenal glands.
258
Define diabetes mellitus
Condition caused by an insulin imbalance in the body; type 1 diabetes results from not enough insulin being produced; type 2 diabetes is caused by the body (specifically adipose tissue) not responding to insulin in the blood.
259
2. Peptide hormones interact with which structures on the surface of a cell?
a) receptor proteins
b) second messenger systems
c) pheromones
d) neurotransmitters
e) digestive enzymes
a) receptor proteins
260
3. A _________ requires the use of a second messenger system to enter a cell.
a) steroid hormone
b) peptide hormone
c) pheromone
d) all of the above
b) peptide hormone
261
4. Which of the following acts as the link between the nervous system and the endocrine system?
a) posterior pituitary gland
b) hypothalamus
c) anterior pituitary gland
d) parathyroid
b) hypothalamus
262
5. Growth hormone (GH) is released by which endocrine gland?
a) posterior pituitary gland
b) hypothalamus
c) anterior pituitary gland
d) adrenal gland
c) anterior pituitary gland
263
Which of the following hormones is regulated by positive feedback mechanisms?
a) thyroid-stimulating hormone (TSH)
b) gonadotropic hormone
c) oxytocin
d) growth hormone
e) none of the above
c) oxytocin
264
7. Thyroid hormones directly regulate which aspect of human physiology?
a) circadian rhythm
b) stress response
c) sex hormone production
d) metabolic rate
e) none of the above
d) metabolic rate
265
8. Which of the following hormones increases blood calcium levels?
a) calcitonin
b) thyroxine (T4)
c) parathyroid hormone
d) mineralocorticoid
c) parathyroid hormone
266
9. Which of the following hormones is (are) not produced by the adrenal cortex?
a) glucocorticoids
b) mineralocorticoids
c) gonadocorticoids
d) norepinephrine
d) norepinephrine
267
10. Which of the following is not correct regarding aldosterone?
a) It is produced by the adrenal cortex
b) It is inhibited by the action of epinephrine
c) Its release is regulated by renin from the kidneys
d) It causes the kidneys to reabsorb sodium (Na+) ions.
e) all of the above
b) It is inhibited by the action of epinephrine
268
11. Which of the following correctly describes the hormone insulin?
a) It is produced by B cells in the pancreas
b) It increases glucose uptake by liver and muscle cells
c) It is a peptide hormone
d) It lowers blood glucose levels
e) all of the above
e) all of the above
269
12. The hormone antagonistic to insulin is
a) epinephrine
b) parathyroid hormone
c) glucagon
d) cortisol
e) progesterone
c) glucagon
270
13. The hormone produced by the pineal gland to regulate the circadian rhythm is called
a) estradiol
b) melatonin
c) renin
d) aldosterone
e) none of the above
b) melatonin
271
14. The disease that is believed to be caused by an autoimmune response that destroys the pancreatic islets is called
a) Addison disease
b) diabetes insipidus
c) type 1 diabetes mellitus
d) types 2 diabetes mellitus
e) gestational diabetes
c) type 1 diabetes mellitus
272
15. Which hormone and condition are mismatched?
a) growth hormone-acromegaly
b) thyroxine- goiter
c) parathyroid hormone-tetany
d) cortisol- myxedema
e) insulin-diabetes
d) cortisol- myxedema
273
Because some of their functions overlap, why is it necessary to have both a nervous system and an endocrine system?
The nervous system allows for quick, almost immediate responses to stress or danger, and fine-tuning of all other bodily function (plus all the other benefits of higher bran functions), while the endocrine system provides longer-lasting responses.
274
Certain endocrine disorders, such as Cushing syndrome, can be caused by excessive secretion of a hormone ( in this case, ACTH) by the pituitary gland, or by a problem with the adrenal gland itself. I you were able to measure the ACTH levels of a Cushing patient, how could you tell the difference between a pituitary problem and a primary adrenal gland problem?
If Cushing syndrome is caused by a problem (such as cancer) of the adrenal gland itself, ACTH levels would be very low, because of negative feedback action of cortisol on the hypothalamus/pituitary.
