EXAM 4: Nervous System Flashcards
1
Q
Nervous System
A
The master controlling and communicating system of the body.
2
Q
Neurons
A
Nerve cells; key to neural communication
3
Q
Three Overlapping Functions of the Nervous System
A
Sensory input, integration, motor output
4
Q
Sensory Input
A
Information gathered by sensory receptors used to monitor changes inside and outside the body
5
Q
Integration
A
A process by which the nervous system integrates sensory information gathered and decides what to do with it at each moment
6
Q
Motor Output
A
A response that is caused by muscles or glands (effectors) that is activated by the nervous system
7
Q
Two Principal Parts of the Nervous System
A
Central Nervous System (CNS) and Peripheral Nervous System (PNS)
8
Q
Central Nervous System (CNS)
A
the brain and spinal cord;
it occupies the dorsal cavity;
it is the integrating and control center of the nervous system;
it interprets sensory input and dictates motor output based on reflexes, current conditions, and past experience.
9
Q
Peripheral Nervous System (PNS)
A
Part of the nervous system outside CNS;
cranial nerves, spinal nerves and ganglia;
mainly consists of bundled fibers (axons) that extend from the brain and the spinal cord and ganglia (neuron cell bodies)
10
Q
Cranial Nerves
A
Carry impulses to and from the brain
11
Q
Spinal Nerves
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Carry impulses to and from the spinal cord
12
Q
Sensory Division
A
Afferent division;
Nerve fibers (axons) that convey impulses to the central nervous system from sensory receptors located throughout the body
13
Q
Two Different Types of Fibers of Afferent Nervous System
A
Somatic nerve fibers and visceral nerve fibers
14
Q
Somatic Nerve Fibers
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Convey impulses from the skin, skeletal muscles, and joints
15
Q
Visceral Nervous System
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Transmit impulses from visceral organs that occupy the ventral body cavity
16
Q
Motor Division
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Efferent division of the PNS that transmits impulses from the CNS to effector organs (muscles and glands);
muscles contract and glands secrete
17
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Two Subdivisions of the Motor Division
A
Somatic nervous system and Autonomic Nervous system
18
Q
Somatic Nervous System
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Somatic nerve fibers that conduct impulses from the CNS to skeletal muscles;
Voluntary nervous system
19
Q
Autonomic Nervous System
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Visceral nerve fibers that regulate the activity of smooth muscles, cardiac muscles and glands;
Involuntary nervous system
20
Q
Sympathetic Division of Autonomic Nervous System
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mobilizes body systems during activity
21
Q
Parasympathetic Division of Autonomic Nervous System
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Promotes house-keeping functions during rest;
Conserves energy
22
Q
Neroglia
A
Glial cells that associate closely with neurons;
there are six types;
outnumber neurons in CNS
23
Q
6 Types of Neuroglia
A
CNS: astrocytes, microglial cells, oligodendrocytes, ependymal cells
PNS: satellite cells and Schwann cells (neurilemma)
24
Q
Schwann Cells
A
neurilemma
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Astrocytes
most abundant neuroglia in CNS;
found attached to blood capillaries and neurons;
support and brace neurons while anchoring them to their supply lines
26
Functions of Astrocytes
1) guide formation of young neurons
2) form synapses between them
3) control chemical environment by mopping up leaked potassium ions and recycling released neurotransmitters
27
Ependymal Cells
Simple cuboidal cells with cilia
line the central cavities of the brain and spinal cord, where they form a fairly permeable barrier between the cerebrospinal fluid and the tissue bathing the cells of the CNS;
the beating of the cilia helps propel and circulate the fluid that cushions the brain and the spinal cord
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Microglial cells
small and ovoid cells with relatively long processes;
the processes touch nearby neurons, monitoring their health;
when neurons are injured they migrate towards them phagocytizing neural debris and foreign microorganisms
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Oligodendrocytes
cells that have fewer processes that astrocytes;
line thicker CNS nerve fibers and wrap their processes tightly around fibers, producing and covering myelin sheath
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Satellite cells
cells that surround neuron cell bodies located in the peripheral nervous system; have same functions as astrocytes
31
Schwann Cells
Surround all fibers in the PNS and cover thick nerve fibers in the form of myelin sheaths;
are vital in regeneration of damaged peripheral nerve fibers
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Neurons
nerve cells;
structural unit of the nervous system
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3 special characteristics of neurons
have extreme longevity,
are amitotic,
high metabolic rate
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Cell Body
a biosynthetic center and receptive region of a neuron
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Chromatophilic Body
large clusters of ribosomes and rough endoplasmic reticulum that dye darkly
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Dendrites
branching receptive regions of a neuron
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Axon
Impulse-generating and conducting region;
has a hillock and an initial segment;
is covered in myelin sheath;
divides into terminal branches that have axon terminals
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Axon Potential
an outgoing signal called a nerve impulse
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Formation of myelin sheath in PNS
Schwann cells wrap around axons, squezing out their cytoplasm and forming layers;
outer collar of perinuclear cytoplasm is formed
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Nodes of Ranvier
gaps in myelin sheath in PNS
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Perikaryon
soma; neuron cell body;
contains abundant mitochondria;
protein - and membrane-making machinery ;
contains cytoskeletal elements; microtubules and neurofibrils;
contains pigment inclusions: pigments found inside the cell include black melanin, a red iron-containing pigment and a golden-brown pigment called lipofuscin
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Lipofuscin
harmless by-product of lysosomal activity;
the aging pigment, because it accumulates in neurons in elderly individuals
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Ganglia
A collection of neuron cell bodies in the PNS
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Neuron Processes
Armlike prominences;
axons and dendrites
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Dendrites
Short. tapering, diffusely branching extensions of a neuron cell body;
all organelles present in the cell body also occur in dendrites
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Graded Potentials
short-distance signals sent toward the cell body
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Tracts
bundles of axons in the CNS;
they have the same origin, termination, and function
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Nerves
bundles of axons in PNS
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Nucleus
a collection of neuron cell bodies in the CNS
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Axon Collaterals
occasional branches that extend at more or less right angles
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Axolemma
plasma membrane of a neuron's axon that transmits an impulse
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Neurotransmitters
Signaling chemicals;
can either excite or inhibit neurons, muscles, or gland cells
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Anterograde Movement
movement away from the cell body;
substance moved in this direction are mitochondria, cytoskeletal elements (mostly microtubules);
substances travel along the axon in both directions
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Retrograde Movement
Movement towards the cell body;
substances moved in this direction are returning to the cell body to be degraded or recycled;
an important means of intracellular communication, allowing the body to be advised of conditions at axon terminals;
delivers vesicles to cell body containing signal molecules (such as nerve growth factor)
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Nerve Growth Factor
activates certain genes in the nucleus that promote growth
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Function of Myelin Sheath
protects and electrically insulates fibers, increasing its transmission speed of nerve impulses
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Nonmyelinated Fibers
conduct nerve impulses more slowly
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Neurolemma
outer collar of perinuclear cytoplasm
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Classification of Neurons
multipolar, bipolar, unipolar
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Multipolar Neuron
Have more than two processes;
most common type of neuron in humans;
major type in the CNS
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Bipolar Neuron
have two processes (an axon and a dendrite);
rare neuron found in special sensory organs (retina and olfactory mucosa)
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Unipolar Neuron
have a single short process that emerges from the cell body and divides into T-like into proximal and distal branches;
the more distal process is associated with sensory receptors;
the central process enters into the CNS;
pseudopolar neuron
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Location of Pseudopolar Neuron
PNS; as sensory receptors
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Function of Multipolar Neurons
interneurons that conduct impulses within the CNS, integrating sensory input and motor output
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Function of Bipolar Neurons
sensory neurons located in special sensory organs
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Function of Unipolar Neurons
sensory neurons that conduct impulses along afferent pathways to CNS for interpretation
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Sensory Neurons
Afferent neurons that transmit information from sensory receptors (skin and internal organs);
virtually all are unipolar (except for those that are bipolar)
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Motor Neurons
Efferent neurons that carry impulses to the effector organs (muscles and glands) from CNS;
are multipolar;
except for some some autonomic neurons, their cell bodies are located in the PNS
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Interneurons
Association neurons;
lie between sensory and motor neurons in neural pathways;
they shuttle signals through the CNS where integration occurs;
most are confined in the CNS;
make 99% of neurons of the body;
almost all are multipolar
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Central Nervous System
the brain and the spinal cord
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Cephalization
An elaboration toward the roastal part of the CNS along with an increase in number of neurons
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Cerebral Hemispheres
make up the superior part of the brain;
the two are divided by a longitudinal fissure;
cerebral veins and arteries lie in between and are covered by arachnoid mater
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Transverse Cerebral Fissure
divides cerebellum from temporal and occipital lobes
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Central Sulcus
frontal lobes are separated from parietal lobes by it
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Pre-central Gyrus
lies in front of central sulcus
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Post-central Gyrus
lies behind central sulcus
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Lateral Sulcus
separates frontal and parietal lobes from temporal lobe
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Cortex
gray matter
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Insula
a fifth lobe that is buried deep within the lateral sulcus and forms parts of its floor;
it is covered by portions of the frontal, parietal and temporal lobes
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Three basic regions of each hemispheres
1) external gray matter
2) internal white matter
3) basal nuclei (islands of gray matter) situated deep within the white matter
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Cerebral Cortex
the executive suite of the nervous system where our conscious mind is found;
composed of gray matter: neuron cell bodies, dendrites, associated glia, blood vessels but no nerve fibers
82
Four generalizations About the Functional Regions of the Cortex
1) cortex contains three types of functional areas: sensory, motor, and association; all are interneurons
2) each hemisphere is associated with a contralateral side of the body
3) there is lateralization (specialization) of cortical functions found to each hemisphere
4) our approach is gross oversimplication; the entire cortex is used in one way or another
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Motor areas
areas of the cortex that control voluntary movement;
they lie in the posterior part of the frontal lobe;
they are primary motor cortex, pre-motor cortex, Broca's area and frontal eye field.
84
Primary (Somatic) Motor Cortex
area of the cortex located in the pre-central gyrus of each hemisphere;
large neurons (pyramidal cells) allow voluntary movement of our skeletal muscles; their long fibers extend towards the spinal cord, forming massive voluntary tracts (pyromidal/ corticospinal tracts)
85
Somatotopy
mapping of the body in the CNS;
head is at the inferolateral and toes are at the superomedial end;
motor homunculus is a topographic representation of the body parts
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Premotor Cortex
Area of the cortex that lies in front of the primary (somatic) motor cortex;
it helps plan movements;
it selects and sequences basic motor movements into more complex tasks
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Broca's Area
Area of the cortex located anterior to inferior premotor cortex;
it is present in the left hemisphere only;
directs muscles involved in speech (special speech motor area);
it becomes active as we prepare to speak
88
Frontal Eye Field
Area of the cortex located anterior and partially in to premotor cortex;
it lies superior to Broca's area;
it controls voluntary eye movements
89
Sensory Areas of the Cortex
Areas concerned with conscious awareness of sensation;
found in parietal, insular, temporal, and occipital regions
90
Primary Somatosensory Cortex
Area of the cortex located behind central sulcus;
postcentral gyrus;
neurons in the area receive information from general (somatic) sensory receptors in the skin and proprioceptors
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Proprioceptors
Receptors located in skeletal muscles, joints, and tendons and inform the brain of its position in space
92
Spatial Discrimination
An ability of neurons to identify the body region being stimulated
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Somatosensory Homunculus
A topographic representation of somatosensory region
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Somatosensory Association Cortex
Area of cortex that lies posterior to primary somatosensory cortex;
is responsible for making sense of sensory inputs (temperature, pressure, etc)
95
Primary Visual (Striate) Cortex
An area of the cortex that is found on the posterior tip of the occipital lobe most of it is found buried deep to the calcarine sulcus in the medial aspect of the occipital lobe;
it is the largest cortical sensory area;
it receives visual information that originates on the retina of the eye
96
Visual Association Area
Area of the cortex, surrounding the primary visual cortex and occupying most of the occipital lobe;
communicating with the primary visual (striate) cortex this are uses past visual experiences to interpret visual stimuli
97
Primary Auditory Area
Area of the cortex located in the superior part of the temporal lobe;
impulses are transmitted there where they are interpreted as pitch, loudness, location
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Auditory Association Area
An area of the cortex just posterior to primary auditory cortex that interprets sound as speech, music, scream, etc.
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Where is the cortex responsible for conscious awareness of equilibrium located?
Posterior part of insula adjacent to parietal cortex
100
Primary Olfactory Cortex
Area of cortex located in the medial aspect of the temporal lobe in small region called piriform lobe which is dominated by hooklike uncus
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Gustatory (Taste) Cortex
Area of the cortex responsible for processing taste stimuli located in insula deep to the temporal lobe
102
Visceral Sensory Area
Area of the cortex located posterior to gustatory cortex;
responsible for conscious awareness of visceral sensations
103
General Sensations of the Somatic Sensory Division
touch, pain, pressure, vibration, texture and proprioception in skin, body walls, and limbs
104
Special Sensations of the Somatic Sensory Division
hearing, equilibrium, vision
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General Sensations of the Visceral Sensory Division
stretch, pain, temperature, chemical changes, irritation in viscera, nausea, and hunger
106
Special Sensation of the Visceral Sensory Division
taste, smell
107
Neurolemma
outermost cytoplasmic layer pf the Schwann cell that contains nucleus
108
Location of Cell bodies of Motor Neurons
CNS
109
Synapse
meeting point between a neuron and any other cell where the nerve impulses are transmitted from one cell to another
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Presynaptic Neuron
conducts signal toward synapse
111
Postsynaptic cell
transmits electrical activity away from a synapse
112
Electrical Synapse
Synchronization and flow of information in both directions at the synapse
113
Chemical Synapse
Electrical signal is converted to a chemical signal by presynaptic neuron that must diffuse across the synaptic cleft to the postsynaptic neuron;
can be either excitatory or inhibitory
114
Functions of the Brain
Intelligence, consciousness, memory, sensory-motor integration, innervation of the head
115
Organization of the Brain
Gray matter and white matter
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Parts of the Brain
1. Cerebrum
2. Diencephalon
3. Brainstem
4. Cerebellum
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Cerebrum Surface
Neural cortex that forms gyri and sulci
118
Wernicke's Area
Understanding of the written and spoken language; located in the left hemisphere only along the border between temporal and parietal lobes
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Prefrontal Cortex
Anterior association area;
Multimodal association are that coordinates information from all brain association areas and integrates ongoing events to make predictions;
highest order processing center in the brain and the site of our personality
120
Cerebral White Matter
White matter that allows various areas of cortex to communicate with each other
121
Commissural Fibers
interconnect gray matter of the right and left brain hemispheres (largest is corpus collosum)
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Association Fibers
interconnect gray matter of the same hemisphere (ex: fornix)
123
Projection Fibers
Project information from or to lower regions of CNS (such as internal capsule)
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Basal nuclei
basal ganglia;
masses of gray matter deep within the white matter of the cerebrum involved in subconscious movement of skeletal muscles (such as those involved in posture)
125
White Matter
Myelinated fibers located externally
126
Gray Matter
composed of neuron cell bodies, unmyelinated fibers, interneurons located centrally with an additional layer (cerebrum) located externally to the white matter
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Cerebral Cortex
contains functional regions called cortexes
128
Diencephalon
forms central core of the brain covered by cerebral hemispheres composed of gray matter;
composed of thalamus, hypothalamus and epithalamus
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Thalamus
forms walls of diencephalon;
forms two nuclei on right and left;
it is the relay station and processing center for sensory impulses and outgoing motor information from cerebrum
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Hypothalamus
forms the floor of diencephalon between the mammillary bodies and optic chiasm;
responsible for maintaining homeostasis (visceral control center)
pituitary glands extend from it
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Epithalamus
forms the roof of diencephalon includes pineal gland (endocrine gland)
132
Brain Stem
consists of thre parts: midbrain, pons, and medulla oblongata;
10 out of 12 cranial nerves connect to it
133
Midbrain
Mesencephalon;
processes visual and auditory information and produces involuntary somatic motor responses;
lies between the diencephalon and the pons
134
Cerebral Peduncles
located on the ventral part of the midbrain, contain pyramidal (corticospinal) tracts
135
Corpora Quadrigemina
this portion of the midbrain represents the largest nuclei and is divided into superior and inferior colliculi
136
Inferior Colliculi
Nuclei that act in reflexive response to sound
137
Superior Colliculi
Nuclei that act in visual reflexes
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Pons
"Bridge" between midbrain and medulla oblongata;
pons contains the nuclei of cranial nerves V, VI, VII and motor tracts;
motor information travels to cerebellum via middle cerebellar peduncle;
pontine nuclei to help to help regulate breathing
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Medulla Oblongata
Part of the brainstem that extends into the spinal cord;
most inferior level of the brainstem;
manages heart, circulation and breathing
140
Pyramids
two ridges along ventral midline of medulla that are motor tracts
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Cerebellum
smooths and coordinates body movements and helps to maintain equilibrium;
dorsal to pons and medulla oblongata;
consists of two lateral hemispheres, a medial vermis, an outer cortex of gray matter, and inner white matter called the arbor vitae
142
Ventricles
expanded cavities within the brain that are filled with cerebrospinal fluid and are lined by ependymal cells
143
CSF Flow
CSF is produced by a choroid plexus of each ventricle;
CSF flows through the ventricles into subarachnoid space via the median and lateral apentures (some of the CSF flows through the central canal of the spinal cord);
CSF flows through the subarachnoid space;
CSF is absorbed into the dural venous sinuses via the arachnoid vili
144
Brain Protection
skull, meninges, liquid cushion, and blood-brain barrier
145
Meninges
Pia mater, (subarachnoid mater), arachnoid mater, dura mater, epidural mater;
cover and protect the CNS;
enclose and protect the vessels that supply the CNS; contain cerebrospinal fluid (subarachnoid mater)
146
Dura Mater
Outermost covering of the CNS consisting of dense collagen layers;
composed of two fibrous layers: periosteal (skull) and meningeal (external covering of the brain);
composed of only one layer in spinal cord: meningeal layer;
deep to vertebrae is epidural space
147
Arachnoid
A layer of delicate epithelial tissue and projections that project into the subarachnoid space and connect it to pia mater
148
Cerebrospinal fluid
produced by choroid plexus of ventricles ;
it is a network of permeable capillaries and specialized ependymal cells (located in the ventricles);
produced at 500ml/ day from blood;
fluid moves through subarachnoid space back to the body through arachnoid villi;
its functions are carrying chemical signals, providing liquid cushion, removing wastes, and nourishing
149
Blood-brain barrier
Impermeable capillaries and sinuses that protect the brain from hormones and circulating chemicals and prevent most toxins from entering the brain;
composed of endothelial cells, pericytes, and astrocytes
150
Spinal Cord
A long, thin, tubular structure made up of nervous tissue;
it attaches to spinal nerves and provides two-way conduction pathway;
major center for reflexes;
extends from foramen magnum to L1 and L2 vertebrae;
is divided left and right dorsally by posterior median sulcus and an anterior median fissure
151
White Matter of the Spinal Cord
organized into tracts that are ascending and descending to allow for communication between the brain and the spinal cord (myelinated axons);
superficial to gray matter
152
Dorsal Funiculus
Posterior white column
153
Gray matter of the spinal cord
interneurons and cell bodies of motor neurons
154
Posterior gray horn
gray matter;
sensory component receiving somatic (ventral) and visceral (dorsal) sensory information and composed of interneurons
155
Anterior gray horn
somatic motor nuclei
156
Lateral gray horn
visceral motor nuclei
157
Gray Commissures
axons cross to other side of the spinal cord before reaching their destination
158
retina
lining of photoreceptors and neurons in the eye
159
Rod
type of photoreceptor that responds best to dim light
160
cone
type of photoreceptor that enables color vision
161
Optic nerve
runs from the back of each eye to the brain
162
cochlea
aids in hearing
163
semicircular canal
helps maintain equilibrium
164
Structures of the Nervous System
nerves, ganglia, sensory receptors
165
functions of the PNS
sends sensory information towards the CNS for integration;
receives motor commands from the CNS
166
nerve fibers of the PNS
collections of nerve axons (can either be myelinated or non-myelinated)
167
ganglia
bundles of cell bodies in the PNS
168
nerve anatomy
epineurium, perineurium, endoneurium
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Epineurium
composed of dense collagen fibers that enclose the entire nerve
170
Perineurium
extends inward from the epineurium and separates nerve into bundles of axons (fascicles);
this is the layer through which blood vessels run
171
Endoneurium
delicate loose connective tissue that extends inward from perineurium and surrounds individual axons;
this is the site of capillary beds
172
Functional classification of nerves
sensory, motor, mixed
173
sensory nerves
carry information towards the CNS
174
motor nerves
carry information away from the CNS
175
mixed nerves
carry information both towards and away from the CNS
176
structural classification of nerves
cranial and spinal
177
cranial nerves
attach to brain;
12 in total
178
spinal nerve
attaches to spine
179
I (Cranial Nerve)
Olfactory nerve;
from nasal mucosa to synapse with olfactory bulbs (cerebrum);
smell;
sensory nerve
180
II (Cranial Nerve)
Optic nerve;
thalamus;
sight;
sensory nerve
181
Spinal nerves
31 pairs of nerves grouped according to the area of vertebral column they originate from (all mixed);
8 pairs of cervical nerves;
12 pairs of thoracic nerves;
5 pairs of sacral nerves;
1 pair of coccygeal nerves
182
Structure of a spinal nerve
dorsal root, ventral root, spinal nerve, rami communicates, dorsal ramus, ventral ramus
183
Dorsal root
brings sensory information into the spinal cord
184
Dorsal Root Ganglion
every spinal segment has two ganglia that contain sensory neuron cell bodies
185
ventral root
axons from anterior and lateral gray horns travel out to control sensory somatic and visceral muscles and glands;
most cell bodies sit in the anterior gray horn
186
spinal nerve
portion after ventral and dorsal roots join together
187
rami communicates
sensory and sympathetic motor to viscera
188
dorsal ramus
sensory and motor information to/ from the back
189
Dorsal ramus
sensory and motor information to/ from the back
innervation follows a simple segmental arrangement with each branch innervating a horizontal strip of back muscles and skin
190
ventral ramus
sensory and motor information to/ from the body wall and limbs;
it wraps around to the front of the body and is arranged into nerve plexuses (except in the thoracic regions)
191
cervical plexus (C1-4 or 5)
innervates muscles of neck and diaphragm
192
phrenic nerve
motor and sensory nerve supply to diaphragm
193
brachial plexus
C5-8 & T1;
innervates pectoral girdle and upper limbs;
most important nerves: axillary, radial, median, ulnar
194
lumbar plexus (L1-L4)
innervates pelvic girdle and some parts of the upper legs
194
femoral nerve
motor and sensory nerve supply to anterior muscles and skin of the thigh
194
sciatic nerve
motor and sensory nerve supply to the back of the leg
194
sacral nerves
5 pairs
195
sacral plexus
S1-S4; innervates the leg
195
dermatomes
area of skin innervated by the cutaneous branches of a single spinal nerve;
usually there is a single overlap between dermatomes
196
visceral motor division
autonomic nervous system;
sympathetic and parasympathetic
197
general functions of the ANS
heart rate, blood pressure, digestion, and urination
197
sympathetic autonomic division
involved in fight/ flight responses to stressful situations
198
parasympathetic autonomic division
involved in rest/ digest responses to non-stressful situations
199
somatic nervous system
1. motor neuron from spinal cord to skeletal muscle
2. axon is myelinated; impulse is rapid
3. skeletal muscle movement
200
autonomic nervous system
chains of two neurons
1. 2 motor neuron chain from brain stem or spinal cord
2. axons have little myelination
3. smooth/ cardiac movement or gland secretion
201
preganglionic fiber
cell body of this neuron will be in the CNS and extends out into the PNS where it synapses at an autonomic ganglion (bundle of cell bodies in PNS)
202
postganglionic fiber
cell body of this neuron resides in the ganglion and extends out to the effector organ
203
Sympathetic nervous system
2 neuron chain;
preganglionic fiber releases ACh;
postganglionic fiber releases NE (highly branched axon)
204
Parasympathetic nervous system
2 neuron chain;
preganglionic fiber releases ACh;
postganglionic fiber releases ACh
205
adrenal medulla
innervated by preganglionic sympathetic neurons;
when stimulated by preganglionic neuron they release epinephrine (E) and norepinephrine (NE) into the fluid around around cells (it then diffuses into blood)
206
paravertebral ganglia
sympathetic chain ganglia
207
prevertebral ganglia
parasympathetic chain ganglia
208
dual innervation
most organs have both sympathetic and parasympathetic innervation
209
monosynaptic reflexes
only one synapse in the pathway, between sensory and motor neurons;
fastest reflexes
210
polysynaptic reflexes
at least two synapses in the pathway, so these will always involve at least one interneuron between sensory and motor neuron;
much more common
211
