Exam V

Question 1

PNS vs CNS

Answer 1

PNS: Peripheral Nervous System
Consists of all the nervous tissue outside the CNS (nerves and ganglia). It links the CNS with various parts of the body, The PNS carries information about different tissues of the body to the CNS and carries command from the CNS that alter body activities.

CNS: Central Nervous System
Consists of the brain and the spinal cord, The brain is located within the skull and the spinal cord is located with the vertebral canal formed by the vertebrae. The brain and spinal cord connect with each other to create the foramen magnum of the skull.

The cells of the nervous system are called neurons. They send electrical messages from their cell body to other cells with long extensions called axons. 366

Question 2

Spatial Summation

Answer 2

Summation: Occurs when the effects produced by one graded potential combine with the effects produced by a different graded potential elsewhere on the plasma membrane, which could lead to an action potential. 380

Spatial Summation: Occurs when multiple action potentials from separate neurons arrive simultaneously at the same postsynaptic neuron. In the postsynaptic neuron, each action potential causes depolarizing graded potential that undergoes summation at the trigger zone. If the estimated depolarization reaches the threshold, an action potential is produced. 396

Question 3

Multiple sclerosis/ oligodendrocytes

Answer 3

Oligodendrocytes
Have cytoplasmic extensions that can surround axons. If the cytoplasmic extensions wrap many times around the axon., they form an insulating material called a myelin sheath. One oligodendrocyte can form myelin sheaths around axons of multiple neurons. 371

Multiple sclerosis
An autoimmune disease that results in the demyelination of the CNS neurons, which become sclerotic, or hard. 491

Question 4

EPSP-Excitatory Postsynaptic Potential

Answer 4

When depolarization of the postsynaptic cell occurs, the response it stimulatory, and the resulting graded potential is called EPSP.

They are important because the depolarization might reach a threshold, thereby producing an action potential and a response from the cell. Neurons releasing neurotransmitter substances that cause ESPS’s are excitatory neurons. In general, an ESPS occurs beacuse the membrane has become more permeable to Na+. 391

Question 5

Grey matter vs White matter

Answer 5

Grey matter- Consists of groups of neurons cell bodies and their dendrites, where very little myelin., these areas are darker in apperence. In the CNS, the cortex consists of grey matter on the surface of the brain, Nuclei are clusters of grey matter located deeper with the brain. In the PNS, grey matter consists of clusters of neuron cell bodies, each of which is called a ganglion, a swelling or a knot.

White matter- consists of bundles of parallel myelinated axons, they are whitish in color. In CNS, forms nerve tracts, or conduction pathways, which propagate action potentials from one area of the CNS to another. In the PNS, bundles of axons and their connective tissue sheaths are called nerves. 374

Question 6

Gap Junctions

Answer 6

A small,specialized contact region between cells containing protein channels that aid intercellular commincation by allowing ions and small molecules to pass from one cell to another. 113

Question 7

Trigger Zone

Answer 7

Combination of the axon hillock and the initial segment. The trigger zone is where action potentials are generated. 369

Question 8

Nissl Bodies

Answer 8

Located primarily to cell body and dendrites. They are the primary sites of proteins synthesis in neurons. 369

Question 9

Soma or Neuron Cell Body

Answer 9

The source of information for protein synthesis. 369

Question 10

Axon

Answer 10

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

Question 11

Nuerotransmitter

Answer 11

Any specific chemical agent released by a synaptic cell on excitation that crosses the synaptic cleft and stimulates or inhibits the postsynaptic cell.

Question 12

Ependymal cells

Answer 12

Line the ventricles (cavities) of the brain and the central canal of the spinal cord. Specialized ependymal cells and blood vessels form structured called choroid plexuses, which are located in certain regions of the ventricles. The choroid plexuses secrete cerebrospinal fluid through the brain cavities. Ependymal cells also have long processes at their basal surfaces that extend deep into the spinal cord and seem, in some cases, to have astrocyte-like functions 371

Question 13

Astrocytes

Answer 13

Are glial cells that are star-shaped because cytoplasmic processes extends from the cell body. These extensions widen and spread out to form foot processes, which cover the surfaces of blood vessels, neurons, and pia mater. Astrocytes have an extensive cytoskeleton of microfilaments, which enables them to form supporting framework for blood vessels and neurons,

They 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 capillaries. (Blood-brain barrier)

Astrocytes aid both beneficial and detrimental responses to tissue damage in the CNS, Almost all injuries to CNS induce reactive astrocytosis, in which astrocytes wall of the injury site and help limit the spread of inflammation to the surrounding healthy tissue. Reactive scaring astrocytes also limit the regeneration of axons of injured neurons.

They release chemicals that promote the development of synapses and help regulate synaptic activity by synthesizing, absorbing and recycling neurotransmitters. 370

Question 14

Microglial cells

Answer 14

CNS-specific immune cells. The become mobile and phagocytic in response to inflammation. They phagocytize necrotic tissue, microorganisms, and other foreign substances and that invade the CNS. Aras of the brain or spinal cord that have been damaged by infection, trauma, or stroke have mire microglia than healthy areas. There the microglia performs phagocytosis of dead cells and pathogens. 371

Question 15

Job of the Nervous System

Answer 15

Maintaining homeostasis- The trillions of cells in the body do not function independently of each other but must work together to maintain homeostasis.

Receiving sensory input- Sensory receptors monitor numerous external and internal stimuli. We are aware of sensations from some stimuli, such as sight, hearing, taste, smell, touch, pain, body position, and temperature. Other stimuli such as blood pH, blood gases, and blood pressure, are processed on an unconscious level.

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

Controlling muscles and glands- Skeletal muscles normally contract only when stimulated by the nervous system; thus the nervous system controls the major movements of the body controlling skeletal muscles. The NS control cardiac and some smooth muscles and at what rate to contact.

Establishing and maintaining mental activity- The brain is the center of mental activites, including consciousness, thinking, memory, and emotions. 366

Question 16

Action Potential Steps

Answer 16

380

Question 17

Local Potential

Answer 17

A graded potential is a relatively small change in the membrane potential in that is localized to one area of the plasma membrane. Often, graded potentials lead to the development of action proteinases. These local disturbances in the membrane potential are called graded potentials (or local potential) because of the potential change can vary from small to large.

Result from:

• Chemical signals binding to their receptors
• Changes in the voltage across the plasma membrane
• Mechanical stimulation
• Temperature changes
• Spontaneous opening of ion channels.

Occur in dendrites or cell body of a neuron. 380

Question 18

Diagram of synapse

Answer 18

Google

Question 19

Pre/postsynaptic membrane

Answer 19

Presynaptic membrane- The part of the cell membrane of an axon terminal that faces the cell membrane of the neuron or muscle fiber with which the axon terminal establishes a synapse.

Postsynaptic membrane- The membrane-associated with the postsynaptic cell associated with the postsynaptic terminal. Postsynaptic cells are typically other neurons, muscle cells, or glands. 389

Question 20

Synaptic Vesicles

Answer 20

Sereatory vesicle in the the presynaptic terminal containing nuerotransmitters, such as acetylcholine. 389

Question 21

Voltage-gated calcium

Answer 21

Voltage-gated ion channels open and close in response to specific, small voltage change across the plasma membrane.

Closed voltage-gated Na+ channels are stabilized by Ca2+ and thus are sensitive to changes in the extracellular concentration of Ca2+. Positively charged Ca2+ in the extracellular fluid is attracted to the negatively charged groups of proteins within the voltage-gated Na+ channels. If the extracellular concentration of Ca2+ decreases, these ions diffuse away from the volatge-gated NA+ channel, causing the channels to open. If the concentration of Ca2+ increases then the, it binds to voltage-gated Na+ channels., causing them to close.

Therefore, normal levels of Ca2+ in the extracellular fluid are critical to helping keep the Na+ channels called until the neuron fires an action potential.
376/382/379

Question 22

Ganglia

Answer 22

A collection of neuron cell bodies outside the CNS. 366

Question 23

Schwann Cell

Answer 23

They form myelin sheaths. However, unlike oligodendrocytes, each Schwann cell forms a portion of the myelin sheath around only one axon.

Question 24

Resting membrane potential*

Answer 24

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

Approximately -70 mV in neurons, and -90m V in skeletal muscle fibers. 376

Question 25

Depolarization*

Answer 25

Change in the electric cahrge differnce across the plasma membrane that causes the differnce to be smaller than 0 mV. Phase where action potenial move towards 0 or postive. 378

Question 26

Voltage-gated Sodium Ion Channels

Answer 26

In a resting cell, the membrane is not very permeable to Na+ because of there a few Na+ leak ion channels; therefore, changes in the concentration of Na+ on either side of the plasma membrane do not influence the resting membrane potential very much.

There are gated Na+ channels in the plasma membrane; if they open, membrane permeability to Na+ increases.The sodium diffuses into the cell and moves down the concentration gradient. The inside of the membrane because of more positivity, resulting in depolarization.
379/382

Question 27

Acetylcholine

Answer 27

A neurotransmitter—a chemical messenger that helps carry signals across a nerve synapse.

Acetylcholine serves both excitatory and inhibitory functions, which means it can both speed up and slow down nerve signals. In the central nervous system, its role is primarily excitatory. It plays a role in arousal, memory, learning, and neuroplasticity. It also helps to engage sensory functions upon waking, helps people sustain focus, and acts as part of the brain’s reward system. Acetylcholine helps maintain rapid eye movement (REM) sleep, the part of sleep during which people dream. In the peripheral nervous system, it helps with the contraction of cardiac, skeletal, and smooth muscles. Imbalances in acetylcholine can contribute to the development of myasthenia gravis, an autoimmune disorder that causes muscle weakness and fatigue.390

Question 28

All or Nothing Response

Answer 28

When a stimulus is applied to a cell, an action potential is either produced or not. 388

Question 29

Synapse

Answer 29

Functional membrane to membrane contact of a nerve cell with another nerve cell, muscle cell, gland cell, or sensory receptors,

Question 30

Where do neurotransmitters come from?

Answer 30

In the presynaptic terminal in secretory vesicles. 369

Question 31

Acetylcholinesterase

Answer 31

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

Question 32

Potassium ions (function)

Answer 32

Influences resting membrane potential:
Under normal action potential conditions, K ions diffuses out of the cell. Changes in the K ion concentration gradient and permeability could change the resting membrane potential. An increase in the extracellular concentration of K ions decreases its concentration gradient because the concentration of K ions is normally lower in the extracellular environment than inside the cell. Thus, K ions tends to stay inside the cell

Question 33

Divergent neurons/pathways

Answer 33

A smaller number of presynaptic neurons synapse with a larger number of postsynaptic neurons to into two or more pathways. Diverging pathways allow one part of the nervous system to affect more than one other part of the nervous system

Question 34

Reverberating neurons/pathways

Answer 34

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

Question 35

Convergent neurons/pathways

Answer 35

Multiple neurons converge upon and synapse with a smaller number of neurons. Convergence allows different parts of the nervous systems to activate or inhibit the activity of neurons

Question 36

Cerebrum

Answer 36

The principal and most anterior part of the brain in vertebrates, located in the front area of the skull and consisting of two hemispheres, left and right, separated by a fissure. It is responsible for the integration of complex sensory and neural functions and the initiation and coordination of voluntary activity in the body

Question 37

Cortex

Answer 37

The outer layer of the cerebrum (the cerebral cortex ), composed of folded gray matter and playing an important role in consciousness

Question 38

Thecal sac

Answer 38

A sac formed by the dura mater which attaches to the rim of the foramen magnum and ends at the level of the second sacral vertebra

Question 39

Filum terminale

Answer 39

Connective tissue strand that anchors the conus medullar is and the thecal sac to the first coccygeal vertebra, limiting their superior movement

Question 40

Spinal Enlargements

Answer 40

Cervical enlargement: inferior cervical region corresponds to the location where nerve fibers that supply the upper limbs enter and leave the spinal cord
Lumbosacral enlargement: inferior thoracic, lumbar, and superior sacral regions is the site where the nerve fibers that supply the lower limbs enter or leave the spinal cord

Question 41

Reflex (function)

Answer 41

An automatic response to stimulus produced by a reflex arc. They are homeostatic, remove the body from painful stimuli, and keeps the body from suddenly falling/moving from external forces

Question 42

Golgi tendon reflex

Answer 42

Prevents contracting muscles from applying excessive tension to tendons

Question 43

Epidural space

Answer 43

The dura mater around the spinal cord is separated from the periosteum of the vertebral column by the epidural space. This is a true space between the walls of the vertebral canal and the dura mater of the spinal cord that contains spinal nerve roots, blood vessels, areolar connective tissue, and adipose tissue

Question 44

Subdural space

Answer 44

The space between the arachnoid mater and the dura mater. Contains small amount of serous fluid

Question 45

Number of spinal nerves for each section

Answer 45

8 cervical
12 thoracic
5 sacral
5 lumbar
1 coccygeal

Question 46

Endoneurium

Answer 46

A delicate connective tissue layer that surrounds each axon, nerve fiber, and its Schwann cell sheath

Question 47

Epineurium

Answer 47

Dense connective tissue layer that binds the nerve fascicles together to form a nerve

Question 48

Perineurium

Answer 48

Heavier connective tissue layer that surrounds groups of axons to form nerve fascicles

Question 49

Conus medullaris

Answer 49

A bonelike region where the spinal cord tapers (immediately inferior to the lumbosacral enlargment)

Question 50

Dura mater

Answer 50

Most superficial and thicket membrane. “Tough mother”

Question 51

Arachnoid mater

Answer 51

Next deepest meningeal membrane. Very thin & wispy

Question 52

Pia mater

Answer 52

Third, deepest meningeal layer. Bound very tightly to the surface of the spinal cord

Question 53

Arachnoid projections/granulations

Answer 53

Projections of the arachnoid membrane into the dural sinuses that allow CSF entrance from the subarachnoid space into the venous system

Question 54

Spinal fluid position

Answer 54

Within the subarachnoid space

Question 55

Gray mater vs white mater

Answer 55

White mater: Superficial white portion that consists of myelinated axons which form nerve tracts
Gray mater: Deep, gray portion that consists of cell bodies, dendrites, axons

Question 56

Dorsal root (ganglia)

Answer 56

Swelling/knot where sensory neuron bodies are contained

Question 57

Brachial plexus (location & function)

Answer 57

Originates from spinal nerves C5-T1. The first 5 ventral rami that constitute the brachial plexus join to form 3 trunks which separate into 6 divisions & join again to form 3 cords from which 5 branches, or nerves of the upper limb, emerge. The 5 major nerves emerging from the brachial plexus to supply the upper limb are the axillary, radial, musculocutaneous, ulnar, and median nerves

Question 58

Dermatome

Answer 58

The area of skin supplied with sensory innervation by a pair of spinal nerves. Each of the spinal nerves except C1 has a specific cutaneous sensory distribution

Question 59

Another name for the ulnar nerve

Answer 59

“funny bone”

Question 60

Blood brain barrier

Answer 60

A filtering mechanism of the capillaries that carry blood to the brain and spinal cord tissue, blocking the passage of certain substances. Astrocytes