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Flashcards in Directed Objectives: Exam V Deck (63):

Job of the nervous system (Functions)

Pg. 366

1. Maintaining homeostasis
-Cells must work together to maintain homeostasis.
-Can stimulate or inhibit activities to help maintain this.

2. Receiving sensory input
-Monitor numerous external and internal stimulus

3. Integrating Information
-Brain and spinal cord are major organs for processing sensory input and initiating responses.
-The put may produce an immediate response, be stored as memory or ignored.

4. Controlling muscles and glands.
-Controls the secretions of many glands, including sweat glands, salivary glands, and glands of the digestive tract.

5. Establishing and maintaining mental activity.
-The brain is the center of mental activities, including consciousness, thinking, memory, and emotions.



Pg. 366

Peripheral Nervous System (PNS)- Consists of the nervous tissue outside the CNS (nerves and ganglia)
-Carries information about the different tissues of the body to the CNS and carries commands from the CNS that alter body activities.

Central Nervous System(CNS)- Consists of the brain and spinal cord.


Subdivisions of the PNS

Pg. 367

Two subdivisions:

*Sensory division
-Transmits electrical signals, called action potentials, from sensory receptors in the body to the CNS.
-Cells bodies located near the spinal cord by ganglia.
-Also known as Afferent Division

*Motor division
-Transmits action potentials from the CNS to effector organs, such as muscles and glands.
-Also known as Efferent Division



Subdivisions of the Motor Division

Pg. 368

-Voluntary (conscious)

-Involuntary (unconscious)

-Example: The somatic nervous system allows you to decide to move your skeletal muscles, as when you raise your hand.


Trigger Zone Pg. 369

The combination of the axon hillock and the initial segment.
-Where action potentials are generated.


Nissel bodies Pg. 369

-Rough Endoplasmic Reticulum
-Located primarily in the cell body and dendrites.
-Primary sites of protein synthesis in neurons.


Astrocytes Pg. 370

Glial cells that are star-shaped because cytoplasmic processes extend from the cell body.

-Support & Regulate Ions

-Exchange of materials between neurons and capillaries

-Help regulate the composition of extracellular brain fluid. They do this by releasing chemicals that promote the formation of tight junctions between the endothelial cells of the capillaries.

-Nourish neurons and provide a blood brain
barrier between nervous tissue and the blood.


Blood brain barrier Pg. 370

The endothelial cells with their tight junctions form the blood brain barrier.

-Determines what substances can pass from the blood into the nervous tissue of the brain and spinal cord.
-Protects neurons from toxic substances in the blood.
Allows the exchange of nutrients and waste products between the neurons and the blood, and prevents fluctuations in the blood composition from affecting blood functions.


Ependymal Cells Pg. 371

Line the ventricles (cavities) of the brain and the central canal of the spinal cord.

-Frequently have patches of cilia that help circulate cerebrospinal fluid through the brain cavities.


Oligodendrocytes Pg. 371

Have cytoplasmic extensions that can surround axons. If the cytoplasmic extensions wrap many times around the axons, they form an insulating material a myelin sheath.

*One oligodendrocyte can form myelin sheaths around axons of multiple neurons.
*Produce myelin in the CNS
*Often wrap around several neurons.


Neurotransmitters Pg. 369

The presynaptic terminals store many secretory vesicles that contain signal modules.


Axon Pg. 369

Main central process of a neuron that normally conducts action potentials away from the neuron cell body.


Soma Pg. 369

*Also known as the neuron cell body.
-Enlarged portion of the neuron containing the nucleus and other organelles.
-The source of information for protein synthesis.


Microglial Cells Pg. 370

The CNS-specific immune cells.
-They phagocytize necrotic tissue, microorganisms, and other foreign substances that invade the CNS.


Gray Matter VS. White Matter Pg. 374

*Gray Matter
-Consist of groups of neuron cell bodies and their dendrites, where there is little myelin, these areas are darker in appearance.
-In the CNS, the cortex consists of gray matter in the surface of the brain. Nuclei are clusters of gray matter located deeper within the brain.
-In the PNS, gray matter consists of clusters of neuron cell bodies, each of which is called ganglion (pl. ganglia: a swelling or knot).

*White Matter
-Consist of bundles of parallel myelinated axons, they are whitish in color.
-White matter of the CNS forms nerve tracts, or conduction pathways, which propagate action potentials from one area of the CNS to another.
In the CNS, bundles of axons and their connective tissue sheaths are called nerves.


Schwann Cell Pg. 371

-Glial cell of the PNS
-Form myelin sheaths.
-Each Schwann cell forms a portion of the myelin sheath around only one axon.

Nodes of Ranvier: Gaps in the myelin sheath.


Ganglion (Singular) Pg. 374
Ganglia (Plural)

Any groups of nerve cell bodies in the peripheral nervous system.


Voltage-Gated Ion Channels Pg. 378

Open and close in response to a specific, small voltage change across the plasma membrane.
-The movement of ions into and out of the cell changes the charge difference across the plasma membrane, which, in turn, can cause voltage-gated open channels to open and close.


Resting Membrane Potential Pg. 376

Electric charge difference inside a plasma membrane, measured relative to just outside the plasma membrane.


Depolarization Pg. 378

Occurs when the membrane potential becomes more positive and is the movement of the membrane potential closer to zero.


All Or Nothing Response Pg. 382

When a stimulus is applied to a cell, an action potential is either produced or not. In the muscle cells, the cell either contracts to the maximum extent possible, (for a given condition) or does not contract.


Synaptic Vesicle Pg. 389

Secretory vesicle in the presynaptic terminal containing neurotransmitter substances.


Acetycholinesterase Pg. 390

Enzyme found in synaptic cleft that causes the breakdown of acetylcholine to acetic acid and choline, thus limiting the stimulatory effect of acetylcholine.


EPSP- Excitatory
Postsynaptic Potential Pg. 391

Depolarization in the postsynaptic membrane that brings the membrane potential close to the threshold.


Acetycholine Pg. 390

Neurotransmitter substance releases from motor neurons of the parasympathetic and sympathetic divisions, all postganglionic neurons of the parasympathetic division, and some central nervous system neurons.


Divergent Neurons Pg. 398

A smaller number of presynaptic neurons synapse with a larger number of postsynaptic neurons to allow information transmitted in one neuronal pathway to diverge into two or more pathways.
-Allow one part of the nervous system to affect more than one other part of the nervous system.


Reverberating Neurons Pg. 398

Have a chain of neurons with synapses with previous neurons in the chain, making a positive-feedback loop.
-Allows action potentials entering the circuit to cause a neuron farther along in the circuit to produce an action potential more than once.


Convergent Neurons Pg. 398

Multiple neurons converge upon and synapse with a smaller number of neurons.
-Allows different parts of the nervous system to activate or inhibit the activity of neurons.


Spatial Summation Pg. 396

Occurs when multiple action potentials from separate neurons arrive simultaneously at the same postsynaptic neuron.


Where do neurotransmitters come from
Pg. 369

They come from secretory vesicles which are stored in the presynaptic terminals.


Chemical Synapse Pg. 389

Occurs when a chemical messenger, a neurotransmitter is used to communicate a message to an effector.


Action Potential Steps Pg. 382


Characteristics of Action Potentials:
1. Action potentials are produced when a graded potential reaches threshold.

2. Action potentials are all-or-none.

3. Depolarization is a result of increased membrane permeability to Na+ and the movement of Na+ into the cell. Activation gates of the voltage-gated Na+ channels open.

4. Repolarization is a result of decreased membrane permeability to K+, which stops Na+ movement into the cell and increases K+ movement out of the cell. The inactivation gates of the voltage-gated Na+ channels close, and the voltage-gated K+ channels open.

5. During the absolute refractory period, no action potential is produced by a stimulus, no matter how strong. During the relative refractory period, a stronger-than-threshold stimulus can produce an action potential.

6. Action potentials are propagated and, for a given axon or muscle fiber, the magnitude of the action potential is constant.

7. Stimulus strength determines the frequency of action potentials.


Presynaptic Membrane VS. Postsynaptic Membrane Pg. 389

*Presynaptic Membrane: In a chemical synapse, the presynaptic membrane is the membrane of an axon terminal that faces the receiving cell.

*Postsynaptic Membrane: Relating to the membrane of a nerve, muscle, or gland that is in close association with a presynaptic terminal. The postsynaptic membrane has receptor molecules within it that bind to neurotransmitter molecules.


Diagram of Synapse Pg. 389

Review Picture on Page 389


Synapse G-23

Functional membrane-to-membrane contact of a nerve cell with another nerve cell, muscle cell, gland cell, or sensory receptor; functions in the transmission of action potentials from one cell to another; also called neuromuscular junction.


Cerebrum *Google for more information*

Largest part of the brain as a whole.
-Associated with higher brain function thought and action.
-Sometimes the right hemisphere is associated with creativity
-Sometimes the left hemisphere is associated with logic abilities


Cerebral Cortex *Google for more information*

The outer layer of the cerebrum.
-Highly wrinkled
-Essentially this makes the brain more efficient, because it can increase the surface area of the brain and the amount of neurons within it.


Thelac Sac Pg. 405

The dura mater forms a sac which surrounds the spinal cord.
-Attaches to the rim of the foramen magnum and ends at the level of the second sacral vertebra.


Filum Terminale Pg. 406

A connective tissue strand that anchors the conus medellaris and the thecal sac to the first coccygeal vertebra, limiting their superior movement.


Spinal Enlargements Pg. 405

*Cervical Enlargement
-In the inferior cervical region corresponds to the location where nerve fibers that supply the upper limbs enter and leave the spinal cord.

*Lumbosacral Enlargement
-In the inferior thoracic, lumbar and sacral regions is the site where the nerve fibers supplying the lower limbs enter and leave the spinal cord.


Reflex (Function) Pg. 409

Reflex: An autonomic response to a stimulus produced by a reflex arc.

Function: They have homeostatic. They protect us from danger, they help us move our body and help us see. Regulation.

-Autonomic Reflexes: Responsible for maintaining relatively constant blood pressure, blood carbon dioxide levels, and water intake.

-Somatic Reflexes: Remove the body from painful stimuli that would cause tissue damage or keep the body from suddenly falling or moving because of external forces.


Golgi Tendon Reflex Pg. 411

Encapsulated nerve endings that have at their ends numerous branches with small swellings adjacent to bundles of collagen fibers in tendons.
-Located near the muscle-tendon junction.
-Have a high threshold and are sensitive only to intense stretch.

*As a muscle contracts, the attached tendons stretch, resulting in increased tension in the tendon. The increased tension stimulated action potentials in the sensory organs from the Golgi tendon organs.


Epidural Space Pg. 405

The dura mater around the spinal cord is separated from the periosteum of the vertebral canal by this.


Subdural Space Pg. 406

The space between the membrane and the dura mater.
-It contains only a very small amount of serous fluid.


Numbers of Spinal Nerves For Each Section Pg. 411

Cervical 8
Thoracic 12
Lumbar 5
Sacral 5
Coccygeal 1


Endoneurium Pg. 414

Each axon, or nerve fiber, and its Schwann cell sheath are surrounded by a delicate connective tissue layer.


Epineurium Pg. 414

Dense connective tissue binds the nerve fascicles together to form a nerve.


Conus Medullaris Pg. 405

The spinal cord tapers to form a conelike region.
-Its tip is the inferior end of the spinal cord and extends to the level of the second lumbar vertebra.
-The nerves supplying the lower limbs and other inferior structures of the body arise from the lumbar and sacral regions. They exit the lumbosacral enlargement and conus medullaris, course inferiorly through the vertebral canal, and exit through the intervertebral and sacral formina from the second lumbar to the fifth sacral vertebrae.


Dura Mater Pg. 405

The most superficial and thickest membrane.
-"Tough Mother"


Arachnoid Mater Pg. 406

The next deepest meningeal membrane is very thin, wispy.


Pia Mater Pg. 406

The third, deepest meningeal layer, is bound very tightly to the surface of the spinal cord.


Subarachnoid Space Pg. 406

Between the arachnoid mater and the pia mater is this space which contains weblike strands of the arachnoid mater, blood vessels and cerebrospinal fluid (CSF).


Arachnoid Projections

Transfer cerebrospinal fluid from the ventricles back into the blood stream.


Spinal Fluid Position

Cerebrospinal Fluid (CSF) occupies the subarachnoid space (between the arachnoid mater and the pia mater) and the ventricular system around and inside the brain and spinal cord. It fills the ventricles of the brain, cisterns, and sulci, as well as the central canal of the spinal cord.


Gray Mater VS. White Mater In Spinal Cord Pg. 407-408

*Gray Matter
-Consist of neuron cell bodies, dendrites and axons.
-Organized into horns. (Anterior, Posterior & Lateral)

*White Matter
-Consist of myelinated axons, which form nerve tracts.
-Organized into three columns. (Ventral, Dorsal & Lateral)


Dorsal Root (Ganglia) Pg. 408

Dorsal Root:
-Sensory (Afferent) root of a spinal nerve.

Dorsal Root Ganglia:
-Collection of sensory neuron cell bodies within the dorsal root of spinal nerve; also called spinal ganglion.


Brachial Plexus (Where, Job) Pg. 418

Brachial Plexus: Originates from spinal nerves C5-T1. Brachial plexus is the network of nerves that send signals from your spine to your shoulder, arm, and hand.

-Located in the neck extending into the axilla posterior to the clavicle.

-Job: Responsible for controlling the muscles of the shoulder, elbow, wrist and hand, as well as feeling in the arm.

-Job:Responsibe for cutaneous and muscular innervation of the entire upper limb with two exceptions: the trapezius muscle innervated by the spinal accessory nerve and an area of skin near the axilla innervated by the intercostobrachial nerve.


Dermatome Pg. 415

Area of skin supplied by a spinal nerve.



Groups of muscles supplied by a single nerve root.
-Most muscles in the upper and lower limbs receive
innervation from more than one spinal nerve root.
-For example, the biceps brachii muscle performs flexion at the elbow. It is innervated by the musculocutaneous nerve, which is derived from C5, C6 and C7 nerve roots. All three of these spinal nerve roots can be said to be associated with elbow flexion.


Another Name (Common) For Ulnar Nerve Pg. 419

Also known as the "Funny Bone"
-Innervated two forearm muscles plus most of the intrinsic hand muscles, expect some associated with the thumb.
-Its sensory is to the ulnar side of the hand.
-At the funny bone, the nerve closer to the skin, bumping it causes a shock-like feeling.


Gap Junctions

Gap junctions are clusters of intercellular channels that allow direct diffusion of ions and small molecules between adjacent cells.

-The main function of gap junctions is to connect cells together so that molecules may pass from one cell to the other. This allows for cell-to-cell communication, and makes it so that molecules can directly enter neighboring cells without having to go through the extracellular fluid surrounding the cells.
-This means that the cells are linked together and can transfer molecules to each other for use in reactions.


Graded Potential (Local Potential)

A graded potential is produced when a ligand opens a ligand-gated channel in the dendrites, allowing ions to enter (or exit) the cell.

-May be a positive (depolarizing) or negative (hyperpolarizing) voltage change.

-Travel passively, uniformly in all directions
don't require voltage-gated channels.

-Graded potentials[1] occur in dendrites, cell bodies or axon terminals and refer to postsynaptic electrical impulses.

-They are called ‘graded’ because their size or amplitude is directly proportional to the strength of the triggering event. This means that a large stimulus leads to the generation of a strong graded response, and a small stimulus leads to the generation of a weak graded response (they have variable strength signals). Graded potentials lose their strength as they move down the cell body


Voltage Gated Calcium Channels

Causative Factor of Voltage Gate Openings: More sodium ions diffuse into the cell than potassium ions diffuse out of it. The inactivation gates of the voltage-gated sodium ion channels begin to open and the diffusion of sodium ions decreases. After the passage of the action potential, the sodium-potassium pump reestablishes the resting membrane potential.

-Play a crucial role in returning the depolarized cell to a resting state.

-Regulate the entry of calcium ions into excitable cells.

-Play crucial roles in many bodily functions including: cardiac action potentials, neurotransmitter release, muscle contraction.

-Channels initiate the release of neurotransmitters at synapses, and have a powerful influence on synaptic strength. The nervous system requires different levels of calcium concentration, so when transmitter release occurs, high levels of calcium are needed