Unit 3: Muscular system Pt.1

Question 1

What is the purpose of your muscular system?

Answer 1

Regulates homeostasis by stabilizing body positions, producing movements, regulating organ volume, moving substances within the body, and producing heat.

Question 2

What composes your muscular system and how does it work?

Answer 2

The voluntary controlled muscles of your body compose the muscular system.
Skeletal muscles that produce movements do so by exerting force on tendons, which in turn pull on bones or other structures.

Question 3

What are muscles attached to?

Answer 3

Muscles are attached to bones by tendons at their origins and insertions.

Question 4

What happens when skeletal muscle contracts?

Answer 4

When a skeletal muscle contracts, it moves one of the articulating bones. The two articulating bones usually do not move equally in response to contraction. One bones remains stationary or near its original position.

Question 5

Differentiate between origin and insertion in regards to muscles.

Answer 5

The attachment of a muscles tendon to the stationary bone is called the origin.
The attachment of the muscles other tendons to the moveable bone is the insertion.
The origin is usually proximal and the insertion is distal, the insertion is usually pulled towards the origin.

Question 6

Define the belly of the muscle.

Answer 6

The fleshy portion of between the tendons is called the belly.

Question 7

Define action and the relation to reverse muscle action.

Answer 7

The actions of a muscle are the main movements that occur when the muscle contracts.
Certain muscles are also capable of reverse muscle action (RMA), meaning during specific movements of the body the actions are reversed.

Question 8

Define lever in relation to muscles and joints.

Answer 8

In producing movements, bones acts as levers, and joints function as the fulcrum.
A lever is a rigid structure that can move around a fixed point called a fulcrum.

Question 9

Differentiate between effort and load.

Answer 9

A lever is acted on at two different forces, the effort, which causes movements, and the load or resistance, which opposes movement.

Question 10

How does motion occur?

Answer 10

Motion occurs when the effort applied to the bone at the insertion exceed the load.

Question 11

Differentiate between mechanical advantage and mechanical disadvantage.

Answer 11

The relative distance between the fulcrum and load and the point at which the effort is applied determine wether a given lever operates at a mechanical advantage or a mechanical disadvantage.
If the load is closer to the fulcrum and the effort farther from the fulcrum, then only a relatively small effort is required to move a large load over a small distance. This is called a mechanical advantage.
If the load is farther from the fulcrum and the effort is applied closer to the fulcrum, then a relatively large effort is require to move small load. This is called a mechanical disadvantage.

Question 12

What are the three types of levers?

Answer 12

• First class lever
• Second class lever
• Third class lever

Question 13

Define first class levers.

Answer 13

The fulcrum is between the effort and the load. A first class lever can produce either a mechanical advantage or a mechanical disadvantage.

Question 14

Define second class levers.

Answer 14

The load is between the fulcrum and the effort. They always produce a mechanical advantage because the load is always closer to the fulcrum than the effort. This type of lever produces the most force. This class of lever is uncommon in the human body.

Question 15

Define third class lever.

Answer 15

The effort is between the fulcrum and the load. These levers operates like a pair of forceps and are the most common levers in the body. Third class levers always produce a mechanical disadvantage because the effort is always closer to the fulcrum than the load.

Question 16

Define what fascicles are.

Answer 16

Within a muscle are arranged in bundles known as fascicles. Within a fascicle, all muscle fibers are parallel to one another.

Question 17

What are the five patterns of fascicles.

Answer 17

• Parallel
• Fusiform
• circular
• Triangular
• Pennate

Question 18

Define what parallels in fascicles are.

Answer 18

Fascicles parallel to longitudinal axis of muscle; terminate at either end in flat tendon.

Question 19

Define what circular patterns are in fascicles.

Answer 19

Fascicles in concentric circular arrangement form sphincter muscles that encloses an orifice.

Question 20

Define what pennate patterns are. Define the three types.

Answer 20

Short fascicles in relation to total muscle length; tendon extends nearly entire length of muscle
- Unipennate: Fascicles arranged on only one side of the tendon.
- Bipennate: Fascicles arranged on both sides of centrally positioned tendons.
- Multipennate: Fascicles attach oblique from many directions to several tendons.

Question 21

Define what fusiform in fascicles are.

Answer 21

Fascicles nearly parallel to longtitudinal axis of muscles; terminate in flat tendons; muscle tapers towards tendons, where diameter is less than at belly.

Question 22

Define what triangular fascicles are.

Answer 22

Fascicles spread over broad area converge at thick central tendon; gives muscle a triangular appearance.

Question 23

Differentiate between prime mover and antagonist.

Answer 23

Most skeletal muscles are arranged in opposing pairs at joints. Within opposing pairs, one muscle called the prime mover or agonist, contracts to cause an action while the other muscle, the antagonist stretches and yields the effects of the prime mover.
If a prime mover and its antagonist contract at the same time with equal force, there will be no movement.
The muscle primary responsible for a movement is called the primary mover.
A muscle with the opposite action of the prime mover is called an antagonist.

Question 24

Define synergists.

Answer 24

When a prime mover crosses other joints before it reaches the joint at which its primary action occurs. To prevent unwanted movements at intermediate joints or to otherwise aid the movement of the prime mover, muscles called synergists contract and stabilize the intermediate joints.
Synergists are usually located close to the prime mover.
Muscles that assist in this action are called synergist.

Question 25

Define fixators.

Answer 25

Some muscles in a group also act as fixators, stabilizing the origin of the prime mover so that the prime mover can act more efficiently. Fixators steady the proximal end of a limb while movements occur at the distal end. A synergist that makes the insertion site more stable is called a fixator.

Question 26

Define compartments in muscles.

Answer 26

In the limbs, a compartment is a group of skeletal muscles, their associated blood vessels, and associated nerves all of which have a common function.

Question 27

What are the seven characteristics used to name muscles?

Answer 27

- Direction - Size - Shape - Action - Number of origins - Location - Origin and insertion

Question 28

How are facial expressions contract?

Answer 28

Muscles of facial expression move the skin rather than a joint.

Question 29

What are the three scalp muscles that make up facial expressions? Explain them.

Answer 29

- Occiptofrontalis - Frontal belly: Draws scalp anteriorly, raises eyebrows, and wrinkles skin of the forehead horizontally as in locks of surprise. - Occipital belly: Draw scalp posteriorly.

Question 30

What are the four mouth muscles responsible for facial expression? Explain them.

Answer 30

- Orbicularis oris: Closes and protrudes lips, as in kissing: compresses lips against teeth; and shapes lips during speech. - Zygomaticus major: Draws angle of mouth superiorly and laterally, as in smiling. - Buccinator: Presses cheeks against teeth and lips

Question 31

What is the orbit and eyebrow muscle responsible for facial expression? Explain it.

Answer 31

Orbicularis oculi: closes eyes.

Question 32

Explain what muscles of mastication is. What are the two powerful closers of the jaw and account for the strength of the bite? Explain the origin, insertion, and action.

Answer 32

The muscle that move the mandible at the tempomandibular joint are known as the muscles of mastication also known as chewing. Masseter: - Origin: Maxilla and zygomatic arch - Insertion: Angle and ramus of mandible - Action: Elevates mandible, as in closing mouth Temporalis: - Origin: Temporal bone - Insertion: Coronoid process and ramus of mandible - Action: Elevates and retracts mandible

Question 33

What is the head attached to?

Answer 33

The head is attached to the vertebral column at the atlanto-occipital joints formed by the atlas and occipital bone.

Question 34

What is the muscle responsible for the movement of the head? Explain the origin, insertion, and action.

Answer 34

Sternocleidomastoid: Divided into two principle triangles (anterior and posterior) - Origin: Sternal head, manubrium of sternum, clavicular head, medial third of clavicle. - Insertion: Mastoid process of temporal bone and lateral half of superior nuchal line of occipital bone. - Action: Acting together, flex cervical portion of vertebral column, extended head at atlanto-occipital joints. Acting singly, laterally flex neck and head to same side and rotate head to side opposite contracting muscle. Laterally rotate and flex head to opposite sides of muscle. Posterior fibers of muscle can assist in extension of head. Elevates sternum during forced inhalation.

Question 35

What are the four muscles protecting the abdominal visceras and moves the vertebral column? Explain the origin, insertion, and action.

Answer 35

Rectus abdominis: - Origin: Pubic crest and pubic symphysis - Insertion: Cartilage of ribs 5 - 7 and xiphoid process. - Action: Flexes vertebral column, especially lumbar portion and compresses abdominal to aid in defecation, urination, forced exhalation, and childbirth. External oblique: - Action: Acting together, compress abdomen and flex vertebral column. Acting singly, laterally flex vertebral column, especially lumbar portion and rotate vertebral column. Internal oblique: - Action: Same as external oblique. Transversus abdominis: - Insertion: Xiphoid processes, linea alba, and pubis. - Action: Compresses abdomen.

Question 36

Describe the purpose of the anterolateral abdominal muscles.

Answer 36

The anterolateral abdominal muscles protect the abdominal viscera, move the vertebral column, and assist in forced exhalation, defecation, urination, and childbirth.

Question 37

Describe the rectus sheath. How is it related to linea alba?

Answer 37

The aponeuroses (sheathlike tendon) of the external oblique, internal oblique, and transverse abdominis muscles form the rectus sheath. It encloses the rectus abdominis muscles. The sheaths meet at the midline to form the linea alba, a tough fibrous band that extends from the xiphoid process of the sternum to the pubis symphysis. In the later stages of pregnancy, the linea alba stretchs to increase the distance between the rectus abdominis muscles.

Question 38

What are the two types of muscles most important in breathing?

Answer 38

The diaphragm and the intercostals.

Question 39

Describe what the diaphragm is. How does it work?

Answer 39

The dome shapes diaphragm is the most important muscle that powers breathing. It also separates the thoracic and abdominal cavity. It peripheral muscular portion of the diaphragm originates on the xiphoid process of the sternum, the inferior six ribs and their costal cartilages, and the lumbar vertebrae and their intervertebral discs and the twelfth ribs. Breathing in contracts the diaphragm and causes it to flatten and increase in vertical dimension. Breathing out causes the diaphragm to expand.

Question 40

Define what intercostal muscles are.

Answer 40

Also involved in breathing. They span the intercostal spaces, which are the spaces between the ribs. These muscles are arranged in three layer but two are the most important which are the external intercostal and internal intercostal muscles. The external intercostal runs diagonally on the surface of the muscle. The main purpose of these muscles is to help expand and deflate the thoracic cage when breathing. `

Question 41

Name the two anterior thoracic muscles that move the pectoral girdle. Explain the origin, insertion, and action.

Answer 41

Pectoralis minor - Action: Abducts scapula and rotates it downwards. Elevates ribs 3 - 5 during forced inhalation when scapula is fixed. Serratus anterior - Origin: Ribs 1 - 8 or 1 - 9 - Insertion: Vertebral border and inferior angle of scapula. - Action: Abducts scapula and rotates it upward. Elevates ribs when scapula is stabilized. Known as 'boxers muscle' because it is important in horizontal arm movements such as punching and pushing.

Question 42

Name the three posterior thoracic muscles that move the pectoral girdle. Explain the origin, insertion, and action.

Answer 42

Trapezius - Origin: Superior nuchal line of occipital bone, ligamentum nuchae and spine of C7 - T12. - Insertion: Clavicle and acromion and spine of scapula. - Action: Superior fibers upward rotate scapula. Middle fibers adduct scapula. Inferior fibers depress and upward rotates scapula. Superior and inferior fibers together rotate scapula upward. Superior fibers can help extend the head. Levator scapulae - Origin: Transverse processes of C1 - C4. - Insertion: Superior vertebral border of scapula. - Action: Elevates scapula and rotates it downward. Rhomboid major - Action: Elevates and adducts scapula and rotates it downward stabilizes scapula.

Question 43

Where does the muscles that move the pectoral girdle originate from?

Answer 43

Muscles that move the pectoral girdle originate on the axial skeleton and insert on the clavicle or scapula.

Question 44

Describe the two axial muscles that move the humerus. Explain the origin, insertion, and action.

Answer 44

Pectoralis major - Origin: Clavicle, sternum, and costal cartilages of the ribs 2 - 6 and sometimes the ribs 1 - 7. - Insertion: Greater tubercle and lateral lip of inter tubercular sulcus of humerus. - Action: As a whole, adducts and medially rotates arm at shoulder joint. Clavicular head flexes arm, and sternocostal head extends flexed arm to side of trunk. Latissimus dorsi - Action: Extends, adducts, and medially rotates arm at shoulder joint. Draws arm inferiorly and posteriorly. Elevates vertebral column and torso.

Question 45

What are the six scapular muscles that move the humerus? Explain the origin, insertion, and action.

Answer 45

Deltoid - Origin: Acromial extremity of clavicle, acromion of scapula, and spine of scapula. - Insertion: Deltoid tuberosity of humerus. - Action: Lateral fibers abducts arm at shoulder joint. Anterior fibers flex and medially rotate arm at shoulder. Posterior fibers extend and laterally rotate arm at shoulder joint. Subscapularis - Action: Medially rotates arm at shoulder joint. Supraspinatus - Origin: Supraspinous fossa of scapula. - Insertion: Greater tubercle of humerus. - Action: Assists deltoid muscle in abducting arm at shoulder joint. Infraspinatus - Action: Laterally rotates arm at shoulder joint. Teres major - Action: Extends arm at shoulder joint and assists in adduction and medial rotation of arm at shoulder joint. Teres minor - Action: Laterally rotates and extends arm at shoulder joint.

Question 46

How is the rotator cuff related to the shoulder joint?

Answer 46

The strength and stability of the shoulder joint are provided by the tendons that form the rotator cuff.

Question 47

Explain the three forearm flexors that moves the radius and ulna. Explain the origin, insertion, and action.

Answer 47

Biceps brachii - Origin: Long head originates from tubercle above glenoid cavity of scapula. - Insertion: Radial tuberosity of radius and bicipital aponeurosis. - Action: Flexes forearm at elbow joint, supination forearm at radioulnar joints, and flexes arm at shoulder joint. Brachialis - Action: Flexes forearm at elbow joint. Brachioradialis - Action: Flexes forearm at elbow joint, supinates and pronates forearm at radioulnar joints to neutral position.

Question 48

Explain the two forearm extension muscles that move the radius and ulna. Explain the origin, insertion, and action.

Answer 48

Tripes brachii - Origin: Long head originates from infraglenoid tubercle, a projection inferior to glenoid cavity of scapula. Lateral head originates from lateral and posterior surface of humerus. Medial head originates from entire posterior surface of humerus inferior to a groove for the radial nerve. - Insertion: Olecranon of ulna. - Action: Extends forearm at elbow joint and extends arm at shoulder joint. Anconeus - Origin: Lateral epicondyle of humerus. - Insertion: Olecranon and superior portion of shaft of ulna. - Action: Extends forearm at elbow joint.

Question 49

Explain the forearm pronator muscles that move the ulna and the radius. Explain the action.

Answer 49

Pronator teres - Action: Pronates forearm at radioulnar joints and weakly flexes forearm at elbow joint.

Question 50

Explain the forearm supinator muscles that move the ulna and the radius. Explain the action.

Answer 50

Supination - Action: Supinates forearm at radiaulnar joints.

Question 51

How does the forearm extend and flexes?

Answer 51

The anterior arm muscle flexes the forearm and the posterior arm muscles extends it.

Question 52

Explain the four superficial anterior compartment of the forearm. Explain the origin, insertion, and action.

Answer 52

Flexor carpi radialis - Origin: Medial epicondyle of humerus. - Insertion: Metacarpals 2 and 3. - Action: Flexes and abducts hand at wrist joint. Palmaris longus - Action: Weakly flexes hand at wrist joints Flexor carpi ulnaris - Origin: Medial epicondyle of humerus and superior posterior border of ulna. - Insertion: Pisiform, hamate, and base of metacarpal 4. - Action: Flexes and adducts hand at wrist joint. Flexor digitorum superficialis - Origin: Medial epicondyle of humerus, coronoid process of ulna, and ridge along lateral margin or anterior surface of radius. - Insertion: Middle phalanx of each finger. - Action: Flexes middle phalanx of each finger at proximal interphalangeal joint, proximal phalanx of each finger at metacarpophalangeal joint, and hand at wrist joint.

Question 53

Explain the three superficial posterior compartment of the forearm. Explain the origin, insertion, and action.

Answer 53

Extensor carpi radialis longus - Action: Extends and abducts hand at wrist joint. Extensor digitorum - Origin: Lateral epicondyle of humerus. - Insertion: Distal and middle phalanges of each finger. - Action: Extends distal and middle phalanges of each finger at interphalangeal joints, and hand at the wrist joint. Extensor carpi ulnaris - Origin: Lateral epicondyle of humerus and posterior border of ulna. - Insertion: Metacarpal 5. - Action: Extends and adducts hand at wrist joint.

Question 54

Whats the main difference between the anterior compartment muscles and the posterior compartment muscles?

Answer 54

The anterior compartment muscle functions as flexors, and the posterior compartment muscles function as extensors.

Question 55

What are the three erector spinae that move the neck and back that move the vertebral column? What is the action?

Answer 55

Ileocostalis cervicis, iliocostalis thoracis, and iliocostalis lumborum. - Action: Acting together, muscles of each region extend and maintain erect posture of vertebral column of their respective regions.

Question 56

Explain the three scalene muscles. Explain their actions.

Answer 56

Anterior scalene - Action: Acting together, right and left anterior scalene and middle scalene muscles elevate first ribs during deep inhalation. Middle scalene - Action: Flex cervical vertebrae. Acting singly, laterally flex and slightly rotate cervical vertebrae. Posterior scalene - Action: Acting together, right and left posterior scalene elevate second ribs during deep inhalation. Flex cervical vertebrae. Acting singly, laterally flex and slightly rotate cervical vertebrae.

Question 57

Explain what the erector spinae muscle groups are.

Answer 57

The erector spinae group is the largest muscular mass of the back and is the chief extensor of the vertebral column.

Question 58

Explain the six muscles included in moving the gluteal region that move the femur.

Answer 58

Iliopsoas psoas major - Origin: Transverse processes and bodies of lumbar vertebrae. - Insertion: With iliacus into lesser trochanter of femur. - Action: Psoas major and iliacus muscles acting together flex thighs at hip joints, rotate thigh laterally, and flex trunk on hip as in sitting up from supine position. Iliacus Gluteus maximus - Origin: Iliac crest, sacrum, coccyx, and aponeurosis of sacrospinalis. - Insertion: Iliotibial tract of fascia lata and superior lateral part of the linea aspera under greater trochanter of femur. Gluteus medius - Action: Abducts thigh at hip joint and medially rotates thigh. Adductor longus - Action: Adducts and flexes thigh at hip joint and rotates thigh. Extends thigh.

Question 59

Where does the muscles that move the femur originate from?

Answer 59

Most muscles that move the femur originate on the pelvic girdle and insert on the femur.

Question 60

Explain the five anterior compartment quadriceps femoris muscles that move the femur, tibia, and fibula. Explain the origin, insertion, and action.

Answer 60

Rectus femoris - Origin: Anterior inferior iliac spine. - Insertion: Patella via quadriceps tendon and then tibial tuberosity via patellar ligaments. - Action: All four heads extend leg at knee joint. Rectus femoris muscle acting along also flexes thigh at hip joints. Vastus lateralis - Origin: Greater trochanter and linea aspera of femur - Insertion: Same as Rectus femoris - Action: Same as Rectus femoris Vastus medialis - Origin: Linea aspera of femur - Insertion: Same as Rectus femoris - Action: Same as Rectus femoris Vastus intermedius - Origin: Anterior and lateral surfaces of femur - Insertion: Same as Rectus femoris - Action: Same as Rectus femoris Sartorius - Action: Weakly flexes leg at knee joint. Weakly flexes, abducts, and laterally rotates thigh at hip joint.

Question 61

Define what hamstrings are.

Answer 61

A collective designation for three separate muscles.

Question 62

Define the three hamstring muscles. Explain the origin, insertion, and action.

Answer 62

Biceps femoris - Origin: Long head arises from ischial tuberosity - Insertion: Head of fibula and lateral condyle of tibia - Action: Flexes leg at knee joint and extends thigh at hip joint. Semitendinosus - Action: Same as Biceps femoris Semimembranous - Action: Same as Biceps femoris

Question 63

Name the two anterior muscle compartments of the legs that move the foot and toes.

Answer 63

Tibialis anterior - Origin: Lateral condyle and body of tibia and interosseous membrane. - Insertion: Metatarsal 1 and first cuneiform. - Action: Dorsiflexes foot at ankle joint and inverts foot at intertarsal joint. Extensor digitorum longus - Origin: Lateral condyle of tibia, anterior surface of fibula, and interosseous membrane. - Insertion: Middle and distal phalanges of toes - Action: Dorsiflexes foot at ankle joint and extends distal and middle phalanges of each toe at interphalangeal joints and proximal phalanx of each toe at metatarsophalangeal joint.

Question 64

Name the lateral muscle compartment of the leg. Explain its action.

Answer 64

Fibularis - Action: plantar flexes foot at ankle joint and erects foot at intertarsal joint.

Question 65

Name the two superficial posterior compartment of the leg that move the toes. Explain the origin, insertion, and action.

Answer 65

Gastrocnemius - Origin: Lateral and medial condyles of femur and capsule of knee - Insertion: Calcaneus by way of calcaneal (achilles) tendon - Action: Plantar flexes foot at ankle joint and flexes leg at knee joint. Soleus - Action: Plantar flexes foot at ankle joint

Question 66

What characteristics allow nerve impulse to generate?

Answer 66

The excitable characteristics of nervous tissue allows for the generation of nerve impulse (action potential) that provide communication with and regulation of most body organs.

Question 67

Define what nervous system is.

Answer 67

The nervous system is one of the smallest and yet the most complex of the 11 body system.

Question 68

Differentiate between a neurologist and neurology.

Answer 68

Neurologist is a physician who diagnosis and treats disorders of the nervous system. Neurology deals with normal functioning and disorders of the nervous system.

Question 69

Define what the central nervous system is.

Answer 69

Consists of the brain and the spinal cord. The brain is located in the skull, and the spinal cord is connected to the brain through the foramen magnum. The CNS processes sensory information. It is also the source of thoughts, emotions, and memories.

Question 70

Define what the peripheral nervous system is.

Answer 70

Consists of all nervous tissue outside the CNS. Components of the PNS includes nerves and sensory receptors.

Question 71

Define what a nerve is.

Answer 71

A nerve is a bundle of hundreds to thousands of axons plus associated connective tissue and blood vessels that lies outside the brain and spinal cord.

Question 72

Differentiate between cranial nerve and spinal nerve.

Answer 72

Twelve pairs of cranial nerves emerge from the brain and thirty one pairs of spinal nerve emerge from the spinal cord.

Question 73

Define what the sensory receptor is.

Answer 73

The term sensory receptor refers to a structure of the nervous system that monitors changes in the external or internal environment.

Question 74

What is the PNS divided into?

Answer 74

The sensory and motor division.

Question 75

Differentiate between the sensory and motor division.

Answer 75

The sensory division also called afferent of the PNS conveys input into the CNS from sensory receptors in the body. This division provides the CNS with sensory information about the somatic senses and special senses. The motor division also called efferent of the PNS conveys output from the CNS to effectors.

Question 76

Differentiate between the somatic senses and special senses.

Answer 76

Somatic senses is tactile, thermal, pain, and proprioceptive sensations. Special senses are smell, taste, vision, hearing, and equilibrium.

Question 77

What two subdivision is motor division split into?

Answer 77

The somatic nervous system and the autonomic nervous system.

Question 78

Define the somatic nervous system.

Answer 78

The somatic nervous system conveys output from the CNS to skeletal muscles only. It is voluntary.

Question 79

Define the autonomic nervous system.

Answer 79

The autonomic nervous system conveys output from the CNS to smooth muscles, cardiac muscles, and glands. It is involuntary.

Question 80

What are the two main branches of the autonomic nervous system.

Answer 80

The two branches are the sympathetic and the parasympathetic nervous system.

Question 81

Differentiate between the sympathetic and the parasympathetic nervous system.

Answer 81

The parasympathetic nervous system takes care of the 'rest and digest' activities. The sympathetic nervous system helps support exercise or emergent actions, also called your fight or flight.

Question 82

Define what the enteric nervous system is.

Answer 82

A network of neurons confined in the walls of the gastrointestinal tract. It helps regulate the activity of the smooth muscle tissue and glands of the GI tract and it also functions independently.

Question 83

Define the three basic functions of the nervous system.

Answer 83

Sensory function: Detects internal stimuli, or external stimuli. This sensory information is then carried into the brain and spinal cord through cranial and spinal nerve. Integrative function: The nervous system process sensory information by analyzing it and making decisions for appropriate responses. An activity known as integration. Motor function: Once sensory information is integrated, the nervous system may elicit an appropriate motor response by activating effectors through cranial and spinal nerves.

Question 84

What type of cells is the nervous tissue comprised of?

Answer 84

Neurons and Neuroglia.

Question 85

Differentiate between neurons and neuroglia.

Answer 85

As a result of their specialization, most neurons have lost the ability to undergo mitotic division. Neuroglia are smaller cells, but they greatly outnumber neurons. Neuroglia continues to divide throughouts a persons lifetime.

Question 86

What is the function of neuroglia?

Answer 86

They nourish, support, and protect neurons and maintain the interstitial fluid that bathes them.

Question 87

What does it mean when neurons possess electrical excitability?

Answer 87

Like muscle cells, neurons possess electrical excitability, which is the ability to respond to a stimulus and convert it into action potential.

Question 88

Define what is meant by stimulus.

Answer 88

A stimulus is any change in the environment that is strong enough to initiate an action potential.

Question 89

What is an action potential?

Answer 89

An action potential is an electrical signal that propagates along the surface of the membrane of a neuron. It begins and travels due to the movement of ions between the interstitial fluid and the inside of a neuron through specific ion channels in its plasma membrane.

Question 90

What are the three parts of a neuron?

Answer 90

- Cell body - Dendrites - An axon

Question 91

Define what the cell body is in a neuron?

Answer 91

A cell body, also called soma, contains a nucleus surrounded by cytoplasm that includes typical cellular organelles. The cell body also contains free ribosomes and prominent clusters of rough ER called nissl bodies.

Question 92

What are the function of the nissl bodies?

Answer 92

Newly synthesized proteins produced by the nissl bodies are used to replace cellular components, as material for growth of neurons, and to regenerate damaged axons in the PNS.

Question 93

Differentiate between neurofibrils and microtubules.

Answer 93

The cytoskeleton includes both neurofibrils and microtubules. Neurofibrils are composed of bundles of intermediate filaments that provide the cell shape and support. Microtubules assists in moving materials between the cell body and axon.

Question 94

Define what lipofuscin is.

Answer 94

Aging neuron also contains lipofuscin, it is a pigment that occurs as clumps of yellowish-brown granules in the cytoplasm. Lipofuscin is a product of neuronal lysosomes that accumulates as the neuron ages, but does not seem to harm the neuron.

Question 95

Define what ganglion is.

Answer 95

A collection of neuron cell bodies outside the CNS is called a ganglion.

Question 96

Define what nerve fibers are.

Answer 96

A nerve fiber is a general term for any neuronal process that emerges from the cell body of a neuron.

Question 97

Define the function of dendrites.

Answer 97

Dendrites are the receiving or input portions of the neuron. The plasma membrane of dendrites contain numerous receptor sites for binding chemical messages from other cells.

Question 98

Define what the axon is.

Answer 98

A single axon of a neuron propagates nerve impulses towards another neuron, a muscle fiber, or a gland cell. An axon is a long, thin, cylindrical projection that often joints to the cell body at a cone shaped elevation called the axon hillock.

Question 99

Define what the axon hillock is.

Answer 99

The part of the axon closes to the axon hillock is the initial segment. Nerve impulse arise at the junction of the axon hillock and the initial segment, an area called the trigger zone, from which they travel along the axon to their destination.

Question 100

Why does protein synthesis not occur in the axon?

Answer 100

Rough ER is not present on the axon.

Question 101

What is the cytoplasm of a neuron called? What is it surrounded by?

Answer 101

The cytoplasm of an axon is called axoplasm, and it is surrounded by a plasma membrane called axolemma.

Question 102

Define what axon collaterals are.

Answer 102

Along the length of an axon, side branches called axon collaterals may branch off, typically at a right angle to the axon.

Question 103

Define what axon terminals are.

Answer 103

The axon and its collaterals end by dividing into many fine processed called axon terminals. (the end of the axon)

Question 104

Differentiate between synapse, synaptic end bulbs, and varicosities.

Answer 104

The site of communication between two neurons is called a synapse. The tips of some axon terminals swell into bulb shaped structures called synaptic end bulbs, other exhibits a string a swollen bumps called varicosities.

Question 105

Define what the synaptic vesicles are and what does it contain?

Answer 105

Both synaptic end bulbs and varicosities contain many tiny membranes enclosed in sacs called synaptic vesicles that store a chemical called a neurotransmitter.

Question 106

What is a neurotransmitter?

Answer 106

A neurotransmitter is a molecule released fro ma synaptic vesicles that excites or inhibits another neuron, muscle fibers, or gland cells.

Question 107

Differentiate between slow axonal transport and fast axonal transport.

Answer 107

The slow axonal transport is a slower transport system, it conveys axoplasm in one direction only. From the cell body towards the axon terminal. Slow axonal transport supplies new axoplasm to developing or regenerating axons and replenishes axoplasm in growing and mature axons. Fast axonal transport uses proteins to function as 'motors' to move materials along the surfaces of microtubules of the neurons cytoskeleton. Fast axonal transport moves materials in both directions, and from and towards the cell body.

Question 108

How does fast axonal terminal transport work?

Answer 108

Fast axonal transport that occurs in an anterograde (forward) direction moves organelles and synaptic vesicles form the cell body to the axon terminals. Fast axonal transport that occurs in a retrograde (back) directions moves membrane vesicles and other cellular materials from the axon terminals to the cell body to be degraded and recycled.

Question 109

Define the three structural classifications of neurons.

Answer 109

Multipolar neurons: Usually have several dendrites and one axon. Most neurons in the brain and spinal cord are of this type, as well as all motor neurons. Bipolar neurons: Have one main dendrite and one axon. They are found in the retina of the eyes, the inner ear, and the olfactory area of the brain. Unipolar neurons: Have dendrites and one axon that are fused together to form a continuous process that emerges from the cell body. These neurons are sometimes called pseudounipolar neurons because they begin in the embryo as bipolar neurons. The dendrites of most unipolar neurons function as sensory receptors that detect a sensory stimulus.

Question 110

Where are Purkinje cells and Pyramidal cells found?

Answer 110

Purkinje cells are found in the cerebellum, and the Pyramidal cells are found in the cerebral cortex of the brain

Question 111

What are the three functional classifications of neurons?

Answer 111

Sensory neurons: Also called an afferent neuron. They contain sensory receptors at their distal ends or are located just after sensory receptors that are seperated cells. Once a stimulus activates the receptor, it forms into an action potential which conveys into the CNS through cranial or spinal nerves. Most sensory neurons are unipolar in structures. Motor neurons: Also called an efferent neuron. It conveys action potentials away from the CNS to effectors in the periphery through cranial or spinal nerves. Motor neurons are multipolar in structure. Interneurons: Also called associated neurons. They are mainly located within the CNS between sensory and motor neurons. Interneurons integrate incoming sensory information from sensory neurons and then elicit a motor response by activating the appropriate motor neurons. Most interneurons are multipolar in structure.

Question 112

What is unique about neuroglia compared to neurons? What is a Gliomas?

Answer 112

Neurons cannot divide, but neuroglias can multiply and divide in the mature nervous system. Neuroglias do not generate or propagate action potentials. Brain tumours derives form glia, called gliomas, tend to be highly malignant and to grow rapidly.

Question 113

What are the four neuroglia of the CNS?

Answer 113

- Astrocytes - Oligodendrocytes - Microglial cells or microglia - Ependymal cells

Question 114

What are astrocytes? What are the two types?

Answer 114

These star shaped cells have many processes and are the largest and most numerous of the neuroglia. There are two types: Protoplasmic, found in the grey matter, and fibrous astrocytes, found in the white matter. The processes of astrocytes make contact with blood capillaries, neurons, and the pia matter of the brain.

Question 115

What are the functions of astrocytes?

Answer 115

They contain microfilaments that give them considerable strength, which enables them to support neurons. Processes of astrocytes wrapped around blood capillaries isolate nurons of the CNS from various potentially harmful substances in the blood by secreting chemicals that maintain the unique selective permeability characteristics of the endothelial cells of the capillaries. The endothelial cells create a blood-brain barrier, which restricts the movements of substances between the blood and interstitial fluid of the CNS In the embryo, astrocytes secrete chemicals that regulates the growth, migration, and interconnection among neurons in the brain. Astrocytes help to maintain the appropriate chemical environment for the generation of nerve impulses. Astrocytes may also play a role in learning and memory by influencing the formation of neural synapse.

Question 116

Define what Oligodendrocytes are.

Answer 116

These resemble astrocytes but are smaller and contain fewer processes. The processes are responsible for forming and maintaining the myelin sheath around CNS axons.

Question 117

Define what myelin sheaths are.

Answer 117

Its a multilayered lipid and protein covering around some axons that insulates them and increases the speed of nerve impulse conduction.

Question 118

Define what microglial cells are.

Answer 118

Also called microglia. These neuroglia are small cells with slender processes that give off numerous spine like processes. They function as phagocytes. They remove cellular debris formed during normal development of the neurons system and phagocytize microbes and damaged nervous tissue.

Question 119

Define what ependymal cells are.

Answer 119

They are cuboidal to columnar cells arranged in a single layer that possess microvilli and cilia. These cells line the ventricles of the brain and central canal of the spinal cord. They produce, possibly monitor, and assist in the circulation of cerebrospinal fluid. They also form the blood cerebrospinal fluid barrier.

Question 120

What are the two types of glial cells in the PNS?

Answer 120

- Schwann cells - Satellite cells

Question 121

Define what Schwann cells are.

Answer 121

These cells encircle PNS axons. They also form the myelin sheaths but each Schwann cells myelinated a single axon. A single Schwann cell can also enclose as many as 20 or more unmyelinated axons. These cells participate in axon regeneration, which is easily accomplished in the PNS than in the CNS. Schwann cells begin to form myelin sheaths around axons during fetal development.

Question 122

Define what Satellite cells are.

Answer 122

These flat cells surround the cell body of neurons of PNS ganglia. They provide structural support, regulate the exchange of materials between neuronal cell bodies and interstitial fluids.

Question 123

Describe what it means to have a myelinated axon. Unmyelinated?

Answer 123

Axons surrounded by a multilayered lipid and protein covering called the myelin sheaths, are said to be myelinated. The sheaths electrically insulates the axon of a neuron and increases the speed of nerve impulse conduction. Axons without such covering are said to be unmyelinated.

Question 124

What are the two types of neuroglia cells produce myelin sheaths?

Answer 124

- Schwann cells - Oligodendrocytes

Question 125

Define what neurolemma is.

Answer 125

The outer nucleated cytoplasmic layer of the Schwann cell, which encloses the myelin sheath is the neurolemma. They are found only around axons in the PNW. When an axon is damaged, the neurolemma aids regeneration by forming a regeneration tube that guide and stimulates growth of the axon.

Question 126

Define what Nodes of Ranvier are.

Answer 126

They are gaps in the myelin sheaths, they appear at intervals along the axons. Each Schwann cell wraps one axon segment between two nodes.

Question 127

How are the axons in the CNS myelinated?

Answer 127

An oligodendrocyte myelinates parts of several axons in CNS. They are flat, broad processes that spiral around CNS axons, forming a myelin sheaths. A neurolemma is not present. Nodes of Ranvier are present, but they are fewer in numbers.

Question 128

Why are axons in CNS hard to recover and regrow?

Answer 128

Axons in the CNS display little regrowth after injury. Thought to be due to the absence of a neurolemma, and an inhibitory influence exerted by the oligodendrocytes on axon regrowth.

Question 129

What are clusters of neuronal cell bodies?

Answer 129

A ganglion refers to a cluster of neuronal cell bodies located in the PNS. Ganglia are closely associated with cranial and spinal nerves. A nucleus is a cluster of neuronal cell bodies located in the CNS.

Question 130

What are bundles of axons?

Answer 130

A nerve is a bundle of axons that is located in the PNS. A tract is a bundle of axons that is located in the CNS. Tract interconnect neurons in the spinal cord and brain.

Question 131

Differentiate between grey and white matter.

Answer 131

White matter is composed of primarily myelinated axons. The grey matter of the nervous system contains neuronal cell bodies, dendrites, unmyelinated axons, axon terminals, and neuroglia. Blood vessels are present in both In the spinal cord, the white matter surrounds an inner core of grey matter. In the brain, a thin shell of grey matter covers the surface.

Question 132

What kind of signals neurons use to communicate with each other?

Answer 132

Neurons are electrically excitable. They communicate with one another using two types of electrical signals - Graded potential - Action potentials

Question 133

Differentiate between graded and action potential.

Answer 133

Graded potential are used for short distance communication only. Action potentials allow communication over long distances within the body.

Question 134

Define what muscle action potential means.

Answer 134

An action potential in a muscle fiber is called a muscle action potential.

Question 135

The following is how graded and action potential works.

Answer 135

- As you touch a pen, a graded potential develops in a sensory receptor in the skin of the fingers. - The graded potential triggers the axon of the sensory neuron to forma nerve action potential, which travels along the axon into the CNS and ultimately causes the release of neurotransmitter at a synapse with an interneuron. - The neurotransmitter stimulates the interneuron to form a graded potential in its dendrites and cell body. - In response to the graded potential, the axon of the interneuron forms a nerve action potential. The nerve action potential travels along the axon, which results in neurotransmitters release at the next synapse. - This process of neurotransmitter release at a synapse followed by the formation of a graded potential and then a nerve action potential occurs over and over as interneurons in higher parts of the brain are activated. Once interneurons in the cerebral cortex, the outer part of the brain, are activated, perception occurs and are able to feel the smooth surface of the pen touch your fingers.

Question 136

Supposed you want to writer a letter. The nervous system would respond in the following way:

Answer 136

- A stimulus in the brain causes a grade potential to form in the dendrites and cell body of an upper motor neuron. A type of motor neuron that synapses with a lower motor neuron farther down in the CNS to contract a muscle. The graded potential causes a nerve action potential to occur in the axon of the upper motor neuron, followed by neurotransmitter release. - The neurotransmitter generates a graded potential in a lower motor neuron, a type of neuron that directly supplies skeletal fibers. The grade potential triggers the formation of a nerve action potential and then release of the neurotransmitter at neuromuscular junctions formed with skeletal muscle fibers that control the movement of the fingers. - The neurotransmitter stimulates the muscle fibers that control the finger movement to form a muscle control finger movement to form a muscle action potential. The muscle action potentials causes these muscle fibers to contract, which allows you to write.

Question 137

The production of graded potentials and action potentials depend on two basic features of the plasma membrane of excitable cells, what are the two?

Answer 137

- The existence of a resting membrane potential - The presence of specific types of ion channels.

Question 138

What does membrane potential mean and how does it relate to resting membrane potential? How does the current relate to it?

Answer 138

The plasma membrane of excitable cells exhibits a membrane potential, an electrical potential difference (voltage) across the membrane. In excitable cells, this voltage is termed the resting membrane potential. The flow of charged particles is called current. In living cells, the flow of ions constitutes the electrical current.

Question 139

How does ions move down the electrical gradient

Answer 139

Ions move from areas of higher concentration to areas of lower concentration. Positively charges cations move towards a positively charged area, and vise versa. As ions move, they create a flow of electrical current that can change the membrane potential.

Question 140

What are the four types of ion channels electrical signals produced by neurons and muscle fibers rely on?

Answer 140

- Leak channels - Ligand - gated channels - Mechanical - gated channels - Voltage - gated channel

Question 141

Describe what the leak channels do and how they work.

Answer 141

The gates of leak channels randomly alternate between open and closed positions. Typically, plasma membranes have many more potassium ions leak channels than sodium ion leak channels, and the potassium ion leak channels are leaker than the sodium. Thus, the membranes permeability to potassium ions is much higher than its permeability to sodium ions. Leak channels are found in nearly all cells, including dendrites, cell bodies, and axons of all types of neurons.

Question 142

Define what ligand gated channels do and how they work.

Answer 142

A ligand gated channel opens and closes in response to the binding of a ligand stimulus. A wide variety of chemicals ligands (neurotransmitters, hormones, and particle ions) can open or close ligand channels. Ligand gated channels are located in the dendrites of some sensory neurons, such as pain receptors, and in dendrites and cell bodies of interneurons and motor neuron.

Question 143

Define what mechanical gated channels do and how they work.

Answer 143

A mechanical gated channels opens or closes in response to mechanical stimulation in the form of vibration, touch, pressure, or tissue stretching. A force distorts the channels from its resting position, opening the gate.

Question 144

Define what voltage gated channels and how they work.

Answer 144

A voltage gated channels open in response to change in membrane potential. Voltage gated channels participates in the generation and conduction of action potentials in the axons of all types of neurons.

Question 145

Why does resting membrane potential exists and what does it look like?

Answer 145

A resting membrane potential exists because of a small build up of negative ions in the cytosol along the inside of the membrane, and an equal buildup of positive ions in the extracellular fluid along the outside surface of the membrane.

Question 146

What is the typical voltage in a resting neuron?

Answer 146

The resting membrane potential ranges form -40 to -90mV. A typical value is -70mV.

Question 147

Define what polarized mean.

Answer 147

A cell that exhibits a membrane potential is said to be polarized. Most body cells are polarized.

Question 148

What are the three major factors a resting membrane potential arise from?

Answer 148

- Unequal distribution of ions in the ECF and cytosol. - Inability of most anions to leave the cell - Electrogenic nature of the sodium - potassium ATPhase.

Question 149

What does it man to have an unequal distribution of ions in the ECF and cytosol?

Answer 149

A major factor that contributes to resting membrane potential. Extracellular fluid is rich in sodium and chloride channels. In cytocol, the main cation is potassium, also anions. The number of potassium ions that diffuse down their concentration gradient from the ECF is greater than the number of sodium ions that diffuse from the ECF into the cell. Due to the plasma having more potassium leak channels than sodium leak channels. Asm ore positive potassium ions exit, the inside of the membrane becomes increasingly more negative than the outside.

Question 150

Why cant anions leave the cell?

Answer 150

Most anions inside the cells are not free to leave. They cannot follow the potassium out of the cell because they are attached to nondiffusible molecules such as ATP and large particles.

Question 151

Why is the sodium potassium pump important?

Answer 151

Sodium leak channels are not as present as potassium leak channels, but sodium still slowly leak out down the concentration gradient. Left unchecked, such inward leakage of sodium would eventually destroy the resting membrane potential. This is preventable by the sodium potassium pump. These pumps help maintain the resting membrane potential by pumping out sodium as fast as it leaks in. For every three sodium out, is 2 potassium in.

Question 152

Define what electrogenic mean.

Answer 152

The sodium potassium pump remove more positive charges form the cell than they bring into the cell, they are electrogenic, meaning they contribute to the negativity of the resting membrane potential.

Question 153

Define what graded potential is.

Answer 153

A graded potential is a small deviation from the resting membrane potential that makes the membrane either more polarized (inside more negative) or less polarized (inside less negative).

Question 154

Differentiate between hyper polarizing graded potential and depolarizing grade potential.

Answer 154

When the response makes the membrane more polarized, it is termed as a hyper polarizing graded potential. When the response makes the membrane less polarized, it is termed as depolarizing graded potential.

Question 155

When the graded potential occurs?

Answer 155

A graded potential occurs when a stimulus causes mechanically graded or ligand gated channels to open or close in an excitable cell plasma membrane.

Question 156

Where does graded potential mainly occur in?

Answer 156

Graded potential occurs mainly in the dendrites and cell body of a neuron.

Question 157

Sometimes the place you are used to is not the place you belong.

Question 158

What does localized current mean?

Answer 158

The opening or closing of the ion channels alters the flow of specific ions across the membrane, producing a flow of current that is localized, meaning that it spreads to adjacent regions along the plasma membrane in either direction from the stimulus source for a short distance and then gradually dies out as the charges are lost across the membrane through leak channels.

Question 159

Define what decremental conduction is.

Answer 159

Graded potential die out as they spread along the membrane is known as decremental conduction.

Question 160

Define what summation means.

Answer 160

Graded potential can become stronger and last longer by summating with other graded potential. Summation is the process by which graded potentials add together. If two equal but opposite graded potentials summate, then they cancel each other out and the graded potential disappears.

Question 161

Define what action potential is.

Answer 161

Also called an impulse. Is a sequence of rapidly occurring events that decrease and reverse the membrane potential and then eventually restore it to the resting state.

Question 162

What are the two main phases of an action potential?

Answer 162

- Depolarizing phase - Repolarizing phase

Question 163

Define what depolarizing phase in an action potential.

Answer 163

The negative membrane potential becomes less negative reaches zero, and then becomes positive.

Question 164

Define what repolarizing phase in an action potential.

Answer 164

The membrane potential is restored to the resting state of -70mV

Question 165

What can happen following a repolarizing phase? What does it mean?

Answer 165

After hyperpolarizing phase. The membrane potential temporarily becomes more negative than the resting level.

Question 166

How does an action potential work?

Answer 166

There are two types of voltage gated channels that open and close during an action potential. These channels are present mainly in the axon plasma membrane and axon terminals. The first channels that open, the voltage gated sodium channels, allow sodium to rush into the cell, which causes the depolarizing phase. Then voltage gated potassium channels open, allowing potassium to flow out, which produces the repolarizing phase. The after-hyperpolarizing phase occurs when the voltage gated potassium channels remain open after the repolarizing phase.

Question 167

How does an action potential occur?

Answer 167

An action potential occurs in the membrane of an axon of a neuron when depolarization reaches a certain level termed the threshold. The threshold in a particular neuron is usually constant.

Question 168

When will action potential not occur?

Answer 168

An action potential will not occur in response to a sub threshold stimulus, a weak depolarization that cannot bring the membrane potential to threshold.

Question 169

Define what supra threshold mean.

Answer 169

Several action potential will form in response to a supra threshold stimulus, a stimulus that is strong enough to depolarize the membrane above threshold. Action potentials caused by a supra threshold stimulus has the same size as an action potential caused by a threshold stimulus.

Question 170

Does an action potential generate in response to threshold stimuli or sub threshold stimuli?

Answer 170

An action potential is generated in response to a threshold stimulus but does not form when there is sub threshold stimulus.

Question 171

Explain what all or none response mean.

Answer 171

An action potential occurs completely or it does not occur at all. This characteristics of an action potential is known as the all or none response.

Question 172

Define the depolarizing phase. Define what the two gates involved.

Answer 172

When depolarizing grade potential or some other stimulus causes the membrane of the axon to depolarize to threshold, voltage gated sodium channels open rapidly. Each gated sodium channel has two separate gates, an activation gate and an inactivation gate. In the resting state of a voltage gated sodium channel, the inactivation gate is open, but the activation gate is closed. In the activation state of a voltage gated sodium channel, both the inactivation and activation gates in the channel are opened and sodium inflow begins.

Question 173

Explain the repolarizing phase is.

Answer 173

Shortly after the activation gates of the voltage gated sodium channels open, the inactivation gates close. Now the voltage gated sodium channel is in an inactivated state.

Question 174

Explain what the after hyperpolarizing state.

Answer 174

While the voltage gated sodium channels are open, outflow of potassium may be large enough to cause an after hyperpolarizing phase of the action potential. During this phase, the voltage gated potassium channels remain open and the membrane potential becomes even more negative. Most voltage gated potassium channels do not exhibit an inactivated state. Instead, they alternate between closed and open state.

Question 175

Explain what the refractory period is.

Answer 175

The period of time after an action potential begins during which an excitable cell cannot generate another action potential in response to a normal threshold stimulus is called the refractory period.

Question 176

Explain what an absolute refractory period is.

Answer 176

During the absolute refractory period, even a very strong stimulus cannot initiate a second action potential. Inactive sodium channels cannot re open; they first must return to the resting state.

Question 177

Does graded potentials exhibit a refractory period?

Answer 177

No.

Question 178

Explain what the relative refractory period is.

Answer 178

The relative refractory period is the period of time during which a second action potential can be initiated, but only by a larger than normal stimulus.

Question 179

What causes the depolarization phase?

Answer 179

Inflow of sodium ions causes the depolarization phase, and outflow of potassium ions causes the repolarizing phase of an ation potential.

Question 180

The following is how the phases work together:

Answer 180

- Resting phase: All voltage gated sodium and potassium channels are closed. The axon plasma membrane is at resting membrane potential small build up of negative charges along inside the surface of membrane and an equal build up of positive charges along outside surface of membrane. - Depolarizing phase: When membrane potential of axons reached threshold, the sodium channel activation gates open. As sodium ions move through these channels into the neuron, a build up of positive charges form a long the inside surface of membrane and the membrane becomes depolarized. - Repolarizing phase begins: Sodium channel inactivation gates close and potassium channels opens as some potassium ions leave the neuron and a few negative charges begin to build up along the inside surface of the membrane. - Repolarizing phase continues: Potassium outflow continues. As more potassium ions leave the neuron, more negative charges build up along inside surface of the membrane. Potassium outflow eventually restores resting membrane potential. Sodium channel activation gates close and inactivation gates open. Return to resting state when potassium gates close.

Question 181

Explain what propagation of action potential means.

Answer 181

To communicate information from one part of the body to another, action potentials in a neuron must travel from where they arise at the trigger zone of the axon to the axon terminal. An action potential keeps it strength as it spreads along the membrane. This mode of conduction is called propagation, and it depends on positive feedback.

Question 182

What does decremental mean in an action potential?

Answer 182

An action potential is not decremental, meaning it does not die out.

Question 183

Why can action potential not propagate from the axon terminal to the cell body?

Answer 183

Because any region of membrane that just underwent an action potential cannot regenerate another action. Because they can travel along a membrane without dying out, action potentials function in communication over long distances.

Question 184

What are the two types of propagation?

Answer 184

- Continues conduction - Saltatory conduction

Question 185

Explain what continuous conduction propagation mean.

Answer 185

Involves step by step depolarization and repolarization of each adjacent segment of the plasma membrane. In continuous conduction, ions flow through their voltage gated channels in each adjacent segment of the membrane. Continuous conduction occurs in unmyelinated axons and in muscle fibers.

Question 186

Explain what saltatory conduction propagation mean.

Answer 186

Action potentials propagate more rapidly along myelinated axons than along unmyelinated axons. Saltatory conduction is the special mode of action potential propagation that occurs along myelinated axons, occurs because of the uneven distribution of voltage gated channels. Few voltage gated channels are present in regions where a myelin sheath covers the axolemma.

Question 187

What is unique about the nodes of ranvier?

Answer 187

They do not contain myelin sheaths. There are many voltage gated channels on the axolemma. Current carried by sodium and potassium flows across the membrane mainly at the nodes.

Question 188

What are the two consequences when current flows through the nodes of ranvier?

Answer 188

- The action potential appears to 'leap' from node to node as each nodal area depolarizes to threshold. Because an action potential leaps across long segments of the myelinated axolemma as current flows form one note to the next, it travels much faster than it would in an unmyelinated axon of the same diameter. - Opening a small number of channels only at the nodes, rather than many channels in each adjacent segment of membrane, represents a more energy efficient mode of conduction. Because only small regions of the membrane depolarize and repolarize, less ATP is used by sodium-potassium pumps to maintain a low intracellular concentration of sodium ions and the low extracellular concentration of potassium ions.

Question 189

What are the three factors that affect the speed of propagation?

Answer 189

- Amount of myelination - Axon diameter - Temperature

Question 190

What are the three classification of nerve fibers?

Answer 190

- A Fibers - B fibers - C fibers

Question 191

Explain what A fibers are.

Answer 191

A fibers are the largest diameter axons and are myelinated. A fibers have a brief absolute refractory period and conduct nerve impulses at speeds of 12 to 130 m/sec. The axons of sensory neurons that propagate impulses associated with touch, pressure, positions of joints, and some thermal and pain sensations are A fibers.

Question 192

Explain what B fibers are.

Answer 192

B fibers are also myelinated and exhibit saltatory conduction at speeds up to 15 m/sec. B fibers have a somewhat longer absolute refractory period than A fibers. B fibers conduct sensory nerve impulses from the viscera to the brain and spinal cord. They also constitutes all of the axons of the autonomic motor neurons that extend from the brain and spinal cord to the ANS replay stations called autonomic ganglia.

Question 193

Explain what C fibers are.

Answer 193

The smallest diameter axons and all are unmyelinated. C fibers exhibit the longest absolute refractory periods. These unmyelinated axons conduct some sensory impulses for pain, touch, pressure, heat and cold form the skin, and pain impulses form the viscera. Autonomic motor fibers that extends from autonomic ganglia to stimulate the heat, smooth muscles, and glands are C fibers.

Question 194

The following is a summary of what graded potential is:

Answer 194

- Arise mainly in dendrites and cel body - Ligand gated or mechanically gated ion channels - Decremental (not propagated); permit communications over short distances - Typically longer - May be hyperpolarizing (inhibitory to generation of action potential) or depolarizing (excitatory to generation of action potential) Refractory period is not present. Summation can occur

Question 195

The following is a summary of what graded potential is:

Answer 195

- Arise at trigger zones and propagate along axons. Voltage gated channels for sodium and potassium - Propagates and thus permit communication over longer distances - Duration is shorter - Always consists of depolarizing phase followed by repolarizing phase and return to resting membrane potential - Refractory period is present. Summation cannot occur

Question 196

What is one obvious difference between graded potential and action potential?

Answer 196

Propagation of action potential is that the propagation of action potentials permits communication over long distances, but graded potentials can function only in short distance communication because they are not propagated.

Question 197

Define what synapse is.

Answer 197

A synapse is a region where communication occurs between two neurons or between a neuron and an effector cell.

Question 198

Differentiate between presynaptic neuron and post synaptic neuron.

Answer 198

The term presynaptic neuron refers to a nerve cell that carries a nerve impulse towards a synapse. It is the cell that sends a signal. The cell that receives a signal is the postsynaptic neuron, also called postsynaptic cell. It carries a nerve impulse away from a synapse or an effector cell. the responds to the impulse at the synapse.

Question 199

Explain what electrical synapse is.

Answer 199

At an electrical synapse, action potentials conduct directly between the plasma membranes of adjacent neurons through structures called gap junctions. Each gap junction contains a hundred or so tubular connexons.

Question 200

Explain what connexons are.

Answer 200

They act like tunnels to connect the cytosol of the two cells directly. As ions flow form one cell to the next through the connexins, the action potential spreads from cell to cell.

Question 201

What are the two main advantage of electrical synapse?

Answer 201

- Faster communication: Because action potential conducts directly through gap junctions, electrical synapses are faster. - Synchronization: electrical synapses can synchronize the activity of a group of neurons or muscle fibers. A large number of neurons or muscle fibers. A large number of neurons or muscle fibers can produce action potentials in unison if they are connected by gap junctions.

Question 202

Explain what chemical synapses are.

Answer 202

The plasma membranes of presynaptic and postsynaptic neurons in a chemical synapse are close, and they do not touch. They are separated by the synaptic cleft.

Question 203

Explain what a synaptic cleft is and how does it work?

Answer 203

A synaptic cleft is a space filled with interstitial fluid. Nerve impulses cannot conduct across the synaptic cleft, so an alternative, indirect form of communication occurs. The presynaptic neuron releases a neurotransmitter that diffuse through the fluid in the synaptic cleft and binds to receptors in the plasma membrane of the post synaptic neuron.

Question 204

Explain what postsynaptic potential is.

Answer 204

Postsynaptic neurons receives the chemical signals from the presynaptic neuron and in turn produces a postsynaptic potential, a type of graded potential.

Question 205

Explain what synaptic delay is.

Answer 205

The presynaptic neuron converts an electrical signals into a chemical signal. The postsynaptic neuron receives the chemical signal and in turn generates an electrical signal. The time required for these processes at a chemical synapse, a synaptic delay is the reason that chemical synapses relay signals slower than electrical synapses.

Question 206

The following is how a typical chemical synapse transmits a signal:

Answer 206

- A nerve impulse arrives at a synaptic end bulb of a presynaptic axon - The depolarizing phase of the nerve impulse opens voltage gated calcium channels, which are present in the membrane of synaptic end bulbs. Because calcium ions are more concentrated in the extracellular fluid, calcium flows inward through the opened channels. - An increase in the concentration of calcium inside the presynaptic neurons serves as a signal that triggers exocytosis of the synaptic vessel. As vesicle membranes merge with the plasma membrane, neurotransmitters molecules within the vesicles released in other synaptic cleft. Each synaptic vesicles contains several thousand molecules of neurotransmitter. - The neurotransmitter molecules diffuse across the synaptic cleft and bind to neurotransmitter receptors in the postsynaptic neurons plasma membrane. - Binding of neurotransmitter molecules ot their receptors on ligand gated channels opens the channels and allows particular ions to flow across the membrane - As ions flow through the opened channels, the voltage across the membrane changes. This change in membrane voltage is a postsynaptic potential. The postsynaptic potential may be a depolarization or a hyperpolarization. - When a depolarizing postsynaptic potential reaches threshold, it triggers an action potential in the axon of the postsynaptic neuron. At most chemical synapses, only one way information transfer can occur such as a muscle fiber or a gland cell. Only synaptic end bulbs of presynaptic neurons can release neurotransmitters, and only the postsynaptic neurons can release neurotransmitter. As a result, action potentials move in one direction.

Question 207

What does it mean when a graded potential is excitatory?

Answer 207

A neurotransmitter that causes depolarization of the postsynaptic membrane is excitatory because it brings the membrane closer to threshold.

Question 208

Explain what excitatory postsynaptic potential is (EPSP).

Answer 208

A depolarizing postsynaptic potential is called excitatory postsynaptic potential (EPSP). A single EPSP normally does not initiate a nerve impulse, the postsynaptic cell does become more excitable. Because it is partially depolarized, it is more likely to reach threshold when the next EPSP occurs.

Question 209

What does it mean when a graded potential is inhibitory?

Answer 209

A neurotransmitter that causes hyperpolarization of the postsynaptic membrane is inhibitory. During hyperpolarization, generating an action potential is more difficult than usual because the membrane potential becomes more negative inside and thus even farther away from threshold.

Question 210

Explain what inhibitory post synaptic potential (IPSP) is.

Answer 210

A hyperpolarizing postsynaptic potential.

Question 211

Whats the difference between excitatory in inhibitory?

Answer 211

Excitatory is more positive, and depolarized. Its to reach to threshold. Inhibitory is more negative, and hyperpolarization. It takes away from threshold.

Question 212

Define what neurotransmitter receptors.

Answer 212

Neurotransmitters released from a presynaptic neuron to bind to neurotransmitter receptors in the plasma membrane of a postsynaptic cell. Each type of neurotransmitter receptor has one or more neurotransmitter binding sites where its specific neurotransmitter binding sites where its specific neurotransmitter receptor binds when a neurotransmitter binds to the correct neurotransmitter receptor, an ion channel opens and a postsynaptic potential forms in the membrane of the postsynaptic cell.

Question 213

Neurotransmitters are classified into which categories?

Answer 213

- Ionotropic receptors - Metabotropic receptors

Question 214

Explain what ionotropic receptors are.

Answer 214

A type of neurotransmitter receptor that contains a neurotransmitter binding site and an ion channel. Both the binding site and ion channels are components of the same protein. An ionotropic receptor is a type of ligand gated channels. Without the neurotransmitter, the ion channel is closed. When the correct neurotransmitter binds to the ionotropic receptor, the ion channel opens, and an EPSP or PSP occurs in the cell. Many excitatory neurotransmitters bind to ionotropic receptors that contain cation channels. EPSPs result from opening these cation channels. Many inhibitory neurotransmitters bind to ionotropic receptors that contain chloride channels. IPSPs result from opening these chloride channels.

Question 215

Explain what metabotropic receptors are.

Answer 215

A type of neurotransmitter that contains a neurotransmitter binding site but lacks an ion channel. This receptor is coupled to a separate ion channel. This receptor is coupled to a separate ion channel by a type of membrane protein called a G protein. When a neurotransmitter binds to a metabotropic receptor, the G protein either directly opens the ion channel or it may act indirectly by activating another molecule, a 'secondary messenger' in the cytosol, which opens the ion channels.

Question 216

What are the three ways neurotransmitters are removed form the synaptic cleft?

Answer 216

- Diffusion: molecules diffuse away from the synaptic cleft. Once the neurotransmitter is out of reach of its receptor, it can no longer exert on effect. - Enzymatic degradation: certain neurotransmitters are inactivated through enzymatic degradation - Uptake by cells: many neurotransmitters are actively transported back into the neuron that released them. Others are transported into neighbouring neuroglia. The membrane proteins that accomplish such uptake are called neurotransmitter transporters.

Question 217

What are the two types of summations?

Answer 217

The greater the summation of EPSPs, the greater the chances that threshold will be reached. - Spatial summation - Temporal summation

Question 218

Explain what spatial summation is.

Answer 218

Summation of postsynaptic potentials in response to stimuli that occur at different locations in the membrane of a postsynaptic cell at the same time.

Question 219

Explain what temporal summation is.

Answer 219

Summation of postsynaptic potentials in response to stimuli that occur at the same location in the membrane of the postsynaptic cell but at different times.

Question 220

The sum of all excitatory and inhibitory effects at any given time determines the effects on the postsynaptic neuron.

Question 221

The following is how summation works:

Answer 221

- EPSP: If the total excitatory effects are greater than the total inhibitory effects but less than the threshold level of stimulation, the rest is an EPSP does not reach threshold. Following an EPSP, subsequent stimuli can more easily generate a nerve impulse through summation because the neuron is partially depolarized. - Nerve impulses: If the total excitatory effects are greater than the total inhibitory effects are greater than the total inhibitory effects and threshold is reached, one or more nerve impulses will be triggered. Impulses continue to be generated as long as the EPSP os at or above the threshold level. - IPSP: If the total inhibitory effects are greater than the excitatory effects, the membrane hyperpolarizes. The result is inhibition of the postsynaptic neuron and an inability to generate a nerve impulse.

Question 222

Explain what neurotransmitters are.

Answer 222

Many neurotransmitters are hormones that are released into the blood stream by endocrine cells in organs throughout the body.

Question 223

Explain what neurosecretory cells are.

Answer 223

Within the brain, certain neurons called neurosecretory cells secrete hormones.

Question 224

What are the two classes neurotransmitters are divided into?

Answer 224

- Small molecule neurotransmitters: Includes acetylcholine, amino acids, biogenic amines, ATP and other purines, nitric oxide, and carbon monoxide. - Neuropeptides

Question 225

Explain what acetylcholine (ACh) does.

Answer 225

The best studied neurotransmitter, which is released by many PNS neurons and some CNS neurons. ACh is an excitatory neurotransmitter at some synapses, such as the neuromuscular junction, where the binding of ACh to ionotropic receptors opens cations channels. It is also an inhibitory neurotransmitter at other synapses, where it binds to meabotropic receptors coupled to G proteins that open potassium channels.

Question 226

What is acetylcholinesterase?

Answer 226

It is an enzyme that inactivates ACh by splitting it into acetate and choline fragments.

Question 227

Explain what amino acids do.

Answer 227

Glutamate and aspartate have powerful excitatory effects. Most excitatory neurons in the CNS and perhaps half of the synapses in the brain communicate via glutamate Gamma amniobutyric acid (GABA) and Glycine are important inhibitory neurotransmitter. About half of the inhibitory synapses in the spinal cord use the amino acid glycine; the rest uses GABA.

Question 228

Explain what biogenic amines do.

Answer 228

Most biogenic amines binds to metabotropic receptors; biogenic amines may cause either excitatory or inhibitory, depending on the type of metabotropic receptor at the synapse.

Question 229

What are the most prevalent biogenic amines?

Answer 229

- Norepinephrine: Plays a role in arousal, dreaming, and regulating mood - Epinephrine: Smaller numbers in the brain uses epinephrine Both of these serve as hormones. They get released into the blood stream by the adrenal gland. - Dopamine: Are active during emotional response, addictive behaviour, and pleasurable experiences. Dopamine releasing neurons help regulate skeletal muscle tone and some aspects of movements due to contraction of muscles. - Serotonin: Concentrated in the neurons in a part of the brain called the raphe nucleus. it is thought to be involved in sensory perception, temperature regulation, control of mood, appetite, and the induction of sleep.

Question 230

Explain what catecholamines are.

Answer 230

Norepinephrine, dopamine, and epinephrine are classified chemically as catecholamines. They all have an amino group and a catechol ring composed of six carbons and two adjacent hydroxyl groups. The two enzymes that breakdown catecholamines are catechol-O-methyltransferase and monoamine oxidase.

Question 231

Explain what ATP and other purines are.

Answer 231

The adenosine part of ATP is an excitatory neurotransmitter in both the CNS and the PNS.

Question 232

Explain what nitric oxide is.

Answer 232

This simple gas is an important excitatory neurotransmitter secreted in the brain, spinal cord, adrenal glands, and nerves to the penis, and has a widespread effects throughout the body. Nitric oxide is not synthesized in advance, and packaged into synaptic vesicles. Instead, it is formed on demand and acts immediately. It is a highly radical reactive, before it mixes with water then it turns inactive. In larger quantities, nitric oxide is highly oxide. Phagocytic cells produce nitric oxide to kill microbes and tumour cells.

Question 233

Explain what the nitric oxide synthase do.

Answer 233

The enzyme nitric oxide synthase catalyzes formation of nitric oxide form the amino acids arginine.

Question 234

Explain what carbon monoxide do.

Answer 234

It is also not produced in advance and packaged into synaptic vesicles. It is formed as needed and diffuse out of cells that produce it into adjacent cells. Carbon monoxide is an excitatory neurotransmitter produced in the brain, and in response to some neuromuscular and neuroglandular functions. Carbon monoxide might protect against excess neuronal activity and might be released to dilation of blood vessel, memory, olfactory, vision, thermoregulation, insulin release and ant inflammatory activity.

Question 235

Explain what neuropeptides are.

Answer 235

Neurotransmitters consisting of 3-40 amino acids linked by peptide bonds called neuropeptides are numerous and widespread. They bind to metabotropic receptors and have excitatory or inhibitory actions, depending on the type of metabotropic receptor at the synapse. Neuropeptides are formed in the neuron cell body, packaged into vesicles, and transported to axon terminals.

Question 236

What are enkephalins, endorphins, and dynorphins?

Answer 236

Certain brain neurons have receptors for opiate drugs such as morphine and heroin. These are the molecules that use these receptors.

Question 237

Explain what substance P is.

Answer 237

A type of neuropeptide that is released by neurons that transmit pain related input from peripheral pain receptors into the CNS, enhancing the perception of pain. Enkephalin and endorphine suppress the release of substance P.

Question 238

Explain what neural circuit is.

Answer 238

The CNS contains billions of neurons organized into complicated networks called neural circuits, functional groups of neurons that process specific types of information.

Question 239

Explain what a simple series circuit is.

Answer 239

In a simple series circuit, a presynaptic neuron stimulates a single postsynaptic neuron. A single presynaptic neuron may synapse with several postsynaptic neuron.

Question 240

Explain with divergence is and what diverging circuit means.

Answer 240

Divergence permits one presynaptic neuron to influence several postsynaptic neurons at the same time. In a diverging circuit, the nerve impulse from a single presynaptic neuron causes the stimulation of increasing numbers of cells along the circuit. Sensory signals are also arranged in diverging circuits, allowing a sensory impulse to be relayed to several regions of the brain. This arrangement amplifies the signal.

Question 241

Explain what convergence is and what converging circuit mean.

Answer 241

In convergence, several presynaptic neurons synapse with a single postsynaptic. This arrangement permits more effective stimulation or inhibition of the postsynaptic neuron. In a converging circuit, the postsynaptic neuron receives nerve impulses from several different sources.

Question 242

Explain what reverberating circuit is.

Answer 242

Some circuits are organized so that stimulation of the presynaptic cell causes the postsynaptic cell to transmit a series of nerve impulses. One such circuit is called a reverberating circuit. In this pattern, the incoming impulse stimulates the first neuron, which stimulates the second, and so on. This arrangement sends impulses back through the circuit again and again. Inhibitory neurons may turn off a reverberating circuit after a period of time.

Question 243

Explain what parallel after discharge circuit is.

Answer 243

In this circuit, a single presynaptic cell stimulates a group of neurons, each of which synapses with a common postsynaptic cell. If the input is excitatory, the postsynaptic neuron then can send out a stream of impulses in quick succession.

Question 244

What are the four neural circuits?

Answer 244

- Diverging circuit - Converging circuit - Discharge circuit - Reverberating circuit

Question 245

Explain what plasticity mean.

Answer 245

Throughout your life, your nervous system exhibits plasticity, which is the capability to change based on experience. At the level of individual neurons, the changes that can occur include the sprouting of new dendrites, synthesis of new proteins, and changes in synaptic contacts with other neurons.

Question 246

Explain what regeneration capabilities in the nervous system.

Answer 246

Mammalian neurons have very limited power of regeneration, the capability to replicate or repair themselves. In the PNS, damage to dendrites and myelinated axons maybe repaired if the cell body remains intact and if the schwann cell remains active.

Question 247

Explain what neurogenesis mean in the CNS.

Answer 247

Neurogenesis is the birth of new neurons from undifferentiated stem cells, it occurs regularly in some animals.

Question 248

Explain what epidermal growth factor (EGF) is.

Answer 248

Stimulates cell growth.

Question 249

What are the two factors that contribute to the lack of neurogenesis in other regions of the brain and spinal cord?

Answer 249

- Inhibitory influences from neuroglia, particularly oligodendrocytes. - Absence of growth stimulating cues that were present during fetal development.

Question 250

When does axon and dendrites undergo repairs?

Answer 250

Axons and dendrites that are associated with a neurolemma may undergo repair if the cell body is intact, if the schwann cells are functional, and if the scar tissue formation does not occur too rapidly.

Question 251

Explain what chromotolysis is. And wallerian degeneration. And regeneration tube.

Answer 251

About 24 to 48hrs after injury to a process of a normal peripheral neuron, the nissl body breaks up into fine granular mass. This alteration is called chromatolysis. Degeneration of the distal portion of the axon and myelin sheath is called wellerian degeneration. The schwann cells on either side of the injured site multiply by mitosis, growing toward each other, and may form a regeneration tube across the injured area.