Unit 3: Pt. 2

Question 1

How does the spinal cord and spinal nerves contribute to the homeostasis?

Answer 1

By providing quick, reflexive responsiveness to many stimuli.

Question 2

What are two layers of protection for our central nervous system?

Answer 2

• Vertebral column
• The meninges

Question 3

What is the space between the the meningeal membranes?

Answer 3

The cerebrospinal fluid.

Question 4

Explain what the vertebral column do for protection.

Answer 4

The spinal cord is located within the vertebral canal of the vertebral column. The surrounding vertebrae provides a sturdy shelter for the enclosed spinal cord.

Question 5

Explain what the meninges do and what are the three types?

Answer 5

They are three protective, connective tissue coverings that encircle the spinal cord and brain. The spinal meninges surround the spinal cord and are continuous with the cranial meninges, which encircles the brain.
- Dura mater
- Arachnoid mater
- Pia mater

Question 6

Explain what the epidural space is and what does it contain.

Answer 6

The spinal cord is also protected by a cushion of fat and connective tissue located in the epidural space, a space between the dura mater and the wall of the vertebral column.

Question 7

Explain what the Dura mater is.

Answer 7

The most superficial layer the three layers. It is a thick strong layer of dense irregular connective tissue. The dura mater forms a sac from the level of the foramina magnum in the occipital bone, where it is continuous with the meningeal dura matter of the brain, to the sacral second vertebrae. The dura mater is also continuous with the epinerium, the outer covering of spinal and cranial nerves.

Question 8

Explain what the Arachnoid mater is.

Answer 8

The middle layer of the meningeal membranes. It is a thin, avascular covering comprised of cells and thin, loosely arranged collagen and elastic fibers. It is deep to the Dura mater and is continuous through the foramen magnum with the Arachnoid mater is a thin subdural space, which contains the interstitial fluid.

Question 9

Explain what the Pia mater is.

Answer 9

The inner most meninges layer. It is a thin transparent connective tissue layer that adheres to the surface of the spinal cord and brain. it consists of thin squamous to cuboidal cells within interlocking bundles of collagen fibers and some fine elastic fibers. Within the Pia mater are many blood vessels that supply oxygen and nutrients to the spinal cord.

Question 10

Explain what the denticulate ligaments.

Answer 10

Triangular shaped membranous extensions of the Pia Mater suspend the spinal cord in the middle of its dural sheath. These extensions, called denticulate ligaments, are thickenings of the Pia mater. The ligaments protect the spinal cord against sudden displacement that could result in shock.

Question 11

Explain what the subarachnoid space is.

Answer 11

Located between the Arachnoid mater and Pia mater is a space called subarachnoid space, which contains shock absorbing cerebrospinal fluid.

Question 12

Explain what the spinal cord is.

Answer 12

The spinal cord is roughly oval in shape, being flattened slightly anteriorly and posteriorly. During early childhood, both the spinal cord and the vertebral column grow longer as part of the overall body growth.

Question 13

Explain the difference between the cervical enlargement and the lumbar enlargement.

Answer 13

The cervical enlargement contains nerves that control the upper limbs.
The lumbar enlargement contains nerves that control the lower limbs.

Question 14

Explain what the conus medullaris is.

Answer 14

Inferior to the lumbar enlargement, the spinal cord terminates as a tapering, conical structure called the conus medullaris, which ends at the level of the intervertebral disc between the first and second lumbar vertebrae in adults.

Question 15

Explain what the filum terminate is.

Answer 15

Arising form the conus medullaris is the filum terminate, which is an extension of the Pia mater that extends inferiorly. It fuses with the arachnoid mater, and dura mater and anchors the spinal cord to the coccyx.

Question 16

Explain what the spinal nerves are.

Answer 16

Spinal nerves are the paths of communication between the spinal cord and specific regions of the body.

Question 17

How many spinal nerves are there and where are they lcoated?

Answer 17

There are 31 pairs of spinal nerves.
- 8 pairs of cervical nerves
- 12 pairs of thoracic nerves
- 5 pairs of sacral nerves
- 1 pair of coccygeal nerve

Question 18

Explain what roots are and the two types.

Answer 18

Two bundles of axons, called roots, connect each spinal nerve to a segment of the cord by even smaller bundles of axons called rootlets.
The posterior (dorsal) root and rootlets contain only sensory axons, which conduct nerve impulses from sensory receptor in the skin, muscles, and internal organs into the CNS.
The anterior (central) root and rootlets contains axons of motor neurons, which conduct nerve impulses form the CNS to effectors.

Question 19

What are the two main component of the internal part of the spinal cord?

Answer 19

White and grey matter.

Question 20

Differentiate between white matter and grey matter.

Answer 20

The white matter consists primarily of bundles of myelinated axons of neurons.
The grey matter contains unmyelinated neurons.

Question 21

Differentiate between the anterior median fissure and posterior median suculus.

Answer 21

The anterior median fissure is a wide groove on the anterior (ventral) side.
The posterior median suculus is a narrow furrow on the posterior (dorsal) side.

Question 22

Explain what the grey commissure is. And where the central canal is.

Answer 22

The grey commissure forms the crossbar of the H. In the centre of the grey commissure is a small space called the central canal which is filled with cerebrospinal fluid.

Question 23

Explain what a nuclei is. Differentiate between sensory nuclei and motor nuclei.

Answer 23

In the grey matter of the spinal cord and brain, clusters of neuronal body form functional groups called nuclei.
Sensory nuclei receive input from receptors via sensory neurons, and motor nuclei provide output to effector tissue via motor neuron.

Question 24

Explain what horns are. Differentiate between the posterior grey horns and anterior grey horns.

Answer 24

The grey matter on each side of the spinal cord is subdivided into regions called horns.
The posterior (dorsal) grey horns contains axons of incoming sensory neurons as well as cell bodies and axons of interneurons.
the anterior (ventral) grey horns contains somatic motor nuclei, which are clusters of cell bodies of somatic motor neurons that provide nerve impulses for contracting of skeletal muscle.

Question 25

Explain what the lateral grey horns are and what is unique about them?

Answer 25

Between the posterior and anterior grey horns are the lateral grey horns, which are present only in the thoracic and upper lumbar segments of the spinal cord.
The lateral grey horns contain autonomic motor nuclei, which are clusters of cell bodies of autonomic motor neurons that regulate the activity of cardiac muscle, smooth muscle and glands.

Question 26

Explain what tracts are. Differentiate between sensory (ascending) tracts and motor (descending) tracts.

Answer 26

Columns on the white matter contains distinct bundles of axons. These bundles, which may extend long distances up or down the spinal cord, are called tracts, which are bundles of axons in the CNS, nerve are bundles of axons in the PNS.
Sensory (ascending) tracts consists of axons that conduct nerve impulses toward the brain.
Tracts consisting of axons that carry nerve impulses from the brain are called motor (descending) tracts.

Question 27

The following is how the spinal cord allows sensory input and motor output to be processed:

Answer 27

• Sensory receptors detects a sensory stimuli
• Sensory neurons convey this sensory input in the forms
  of nerve impulses along their axons, which extends from
  sensory receptors into the spinal nerve and into the
  posterior root. From the posterior root, axons of sensory
  neurons may proceed along three possible paths.
• Axons of sensory neurons may extend into the white
  matter of the spinal cord and ascending to the brain as
  part of the sensory tract.
• Axons of sensory neurons may enter the posterior grey
  horn and synapse with interneurons whose axons extend
  into the white matter of the spinal cord and then ascend
  to the brain as part of a sensory tract.
• Axons of sensory neurons may enter the posterior grey
  horn and synapse with interneuron that in turn synapse
  with somatic motor neurons that are involved in spinal
  reflex pathways.
• Motor output from the spinal cord to skeletal muscles
  involves somatic motor neurons of the anterior grey
  horn many somatic motor neuron are regulated by the
  brain. Axons from higher brain centre form motor tract
  that descend from the brain into the white matter of the
  spinal cord. There they synapse with somatic motor
  neurons either directly or indirectly by first synapsing
  with interneurons that in turn synapse with somatic
  motor neurons.
• When activated, somatic motor neurons convey motor
  output in the form of nerve impulses along their axons,
  which sequentially pass through the anterior grey horn
  and anterior root to enter the spinal nerve. From the
  spinal nerve, axons somatic motor neurons extend to
  skeletal muscles of the body.
• Motor output from the spinal cord to cardiac muscle,
  smooth muscle, and gland involves autonomic motor
  neurons of the lateral grey horn. when activated,
  autonomic motor neurons convey motor output in the
  form of nerve impulses along their axons, which
  sequentially pass through the lateral grey horn, anterior
  grey horn , and anterior root to enter the spinal nerve.
• From the spinal nerve, axons of autonomic motor
  neurons from the spinal cord synapse with another
  group of autonomic motor neuron located in the PNS.
  The axons of this second group of autonomic motor
  neurons in turn synapse with cardiac muscle, smooth
  muscle, and glands.

Question 28

How much white matter are then in the spinal cord?

Answer 28

The amount of white matter decreases from cervical to sacral segment of the spinal cord.

Question 29

What are the two major reasons for the decrease of the shite matter in the spinal cord?

Answer 29

• As the spinal cord ascends from sacral to cervical
  segments, more ascending axons are added to spinal
  cord white matter to form more sensory tract.
• As the spinal cord descends from cervical to sacral
  segments, the motor tracts decrease in thickness as
  more descending axons leave the motor tracts to
  synapse with neurons in the grey matter of the spinal
  cord.

Question 30

Explain what spinal nerves are.

Answer 30

Spinal nerves are associated with the spinal cord and, like all nerves of the PNS, are parallel bundles of axons and their associated neuroglia cells wrapped in several layers of connective tissue.

Question 31

What does the spinal nerve connect to?

Answer 31

Spinal nerves connect the CNS to sensory receptors, muscles, and glands in all parts of the body.

Question 32

Does the spinal cord segment align with the corresponding vertebrae?

Answer 32

Not all spinal cord segments are aligned with their corresponding vertebrae.

Question 33

Where does the pairs of the spinal cord emerge out of?

Answer 33

The first cervical pair of spinal nerves emerges form the spinal cord between the occipital bone and the atlas. Most of the remaining spinal nerves emerge from the spinal cord through the intervertebral foramina between the adjoining vertebrae.

Question 34

What does mixed nerve mean?

Answer 34

Because the posterior root contains sensory axons and the anterior root contains motor axons, a spinal nerve is classified as a mixed nerve.

Question 35

What are the three coverings of spinal nerves?

Answer 35

• Endoneurium
• Perineurium
• Epineurium

Question 36

Explain where and what the endoneurium is.

Answer 36

The inner most layer of the spinal nerve coverings. It consists of a mesh of collagen fibers, fibroblasts, and macrophages. Groups of axons with their endoneurium are held together in bundles called fascicles.

Question 37

Explain the middle layer of the spinal nerves.

Answer 37

The perineurium is the middle layer. It is a thicker layer of connective tissue.

Question 38

What is the outermost layer of the spinal nerve coverings?

Answer 38

The outermost covering over the entire spinal nerve is the epineurium. It consists of fibroblast and thick collagen fibers.

Question 39

Explain what branches and ramis are.

Answer 39

A short distance after passing through its intervertebral foramen, a spinal nerve divides into several branches. These branches are known as rami.

Question 40

Explain what the posterior (dorsal) ramus is.

Answer 40

The posterior (dorsal) ramus serves the deep muscle and skin of the posterior and anterior rami.

Question 41

Explain what the meningeal branch is.

Answer 41

The spinal nerves also give off a meningeal branch. This branch reenters the vertebral cavity through the intervertebral foramen and supplies the vertebrae, vertebral ligaments, blood vessels and the meninges.

Question 42

What are plexus?

Answer 42

Axons from the anterior rami of spinal nerves, except for thoracic nerves T2-T12, do not go directly for the body structures they supply. Instead, they form networks on both of the left and right sides of the body by joining with various numbers of axons from anterior rami of adjacent nerves. Such a network of axons is called a plexus.

Question 43

What are the five named plexus’?

Answer 43

• Cervical plexus
• Brachial plexus
• Lumbar plexus
• Sacral plexus
• Coccycgeal plexus (smaller)

Question 44

Explain what the intercostal nerves are.

Answer 44

The anterior rami of spinal nerves T2-T12 do not enter into the formation of plexuses and are known as intercostal nerves or thoracic nerves. These nerves directly connect to the structures they supply in the intercostal spaces.

Question 45

Explain the three main intercostal nerves.

Answer 45

• T2: Supplies the skin of the axilla and posterio-medial
  aspects of the arm
• T3-T6: Extend along the costal grooves of the ribs and
  then to the intercostal muscles and skin of the anterior
  and lateral chest wall.
• T7-T12: Supply the intercostal muscles and abdominal
  muscles, along with the overlying skin.

Question 46

What does the posterior ramis of the intercostal nerves supply?

Answer 46

The posterior rami of the intercostal nerves supply the deep back muscles and skin of the posterior aspects of the thorax.

Question 47

Explain what dermatomes are.

Answer 47

The skin over the entire body is supplied by somatic neurons that carry nerves impulses from the skin into the spinal cord and brain. One of the cranial nerves, the trigeminal (V) nerves, serves most of the face and scalp. The area of the skin that provides sensory input to the CNS via one pair of spinal nerves or the trigeminal nerve is called a dermatome.

Question 48

Why is it important to know which spinal cord segments supply which?

Answer 48

Knowing which spinal segments supply each dermatome makes it possible to locate damaged regions of the spinal cord. If the skin in a particular region is stimulated but the sensation is not perceived, the nerves supplying that dermatome are probably damaged.

Question 49

Why is it important to apply anesthetic drug to adjacent spinal nerves?

Answer 49

Because dermatomes overlap, deliberate production of a region of complete anesthesia may require that at least adjacent spinal nerves be cut or blocked by an anesthetic drug.

Question 50

Explain what the cervical plexus is.

Answer 50

It is formed by the rots of the first four cervical nerves, with contributions from the 5th cervical nerve. There is one on each side of the neck alongside the first cervical vertebrae. the cervical plexus supplies the skin and muscles of the head, neck, and superior part of the shoulder and chest.

Question 51

Explain what the brachial plexus is.

Answer 51

The roots of spinal nerves C5-C8 and T1 form the brachial plexus, which extends inferiorly and laterally on either side of the last four cervical and first thoracic vertebrae. It passes above the first rib posterior to the clavicle and then enters the axilla.
The brachial plexus provides almost the entire nerve supply of the shoulders and upper limbs.

Question 52

Explain what the lumbar plexus is.

Answer 52

The roots of spinal of L1-L4 form the lumbar plexus. Unlike the brachial plexus, there is minimal intermingling of fibers in the lumbar plexus. The lumbar plexus supplies the anterolateral abdominal wall, external genitals, and part of the lower limbs.

Question 53

Explain what the sacral and coccygeal plexus are.

Answer 53

The roots of spinal nerves L4-L5 form the sacral plexus. this plexus is situated largely anterior to the sacrum. The sacral plexus supplies the buttocks, perineum, and lower limbs. The largest nerve in the body, the sciatic nerve, arises from the sacral plexus.

Question 54

What are the two principal functions of the spinal cord to maintain homeostasis?

Answer 54

• Nerve impulse propagation
• Integration of information

Question 55

What are the white and grey matter tracts jobs?

Answer 55

The white matter tracts in the spinal cord are highways for nerve impulse propagation. Sensory input travels along these tracts towards the brain, and motor output travels from the brain along these tracts towards skeletal muscle and other effector tissues.
They grey matter of the spinal cord receives and integrates incoming and outgoing information.

Question 56

The following are the functions of the spinal cord and the spinal nerves:

Answer 56

• The white matter of the spinal cord contains sensory and
  motor tracts, the ‘highways’ for conduction of sensory
  nerve impulses toward the brain and motor nerve
  impulses from the brain toward effector tissues.
• The spinal cord grey matter is a site for integration
  (summing) of excitatory postsynaptic potentials (ESPS)
  and inhibitory postsynaptic potentials (IPSP).
• Spinal nerves and the nerves that branch from them
  connect the CNS to the sensory receptors, muscles, and
  glands.

Question 57

What are the two main routes the nerve impulse propagates up the spinal cord to the brain?

Answer 57

• The spinothalamic tract
• The posterior column

Question 58

Explain what the spinothalamic tract is.

Answer 58

The spinothalamic tract conveys nerve impulses for sensing pain, temperature, itch, and tickle.

Question 59

Explain what the posterior column is.

Answer 59

The posterior column consists of two tracts:
- The gracile fasciculus
- The cuneate fasciculus
The posterior column tracts conveys nerve impulses for touch, pressure, vibration, and conscious proprioceptions.

Question 60

What is the sensory information integrated by?

Answer 60

The sensory system keeps the CNS informed of changes in the external and internal environment. The sensory information is integrated (processed) by interneurons in the spinal cord and brain.

Question 61

How do motor output travel down the spinal cord?

Answer 61

Motor output to skeletal muscles travel down the spinal cord in two types of descending pathways: Direct and indirect.

Question 62

Differentiate between direct motor pathways and indirect motor pathways.

Answer 62

The direct motor pathways, also called pyramidal pathways, include the lateral corticospinal, anterior corticospinal, and corticobular tract. They convey nerve impulses that originates in the cerebral cortex and are destined to cause voluntary movements of skeletal muscles.
Indirect motor pathways, also called extramyramidal pathways, include the rubrospinal, tectospinal, vestibulospinals, lateral reticulospinal, and medial reticulospinal tracts. These tracts conveys nerve impulses form the brainstem to cause automatic movements and help coordinate body movements with visual stimuli.

Question 63

Define what reflex is.

Answer 63

A second way the spinal cord promotes homeostasis is by serving as an integrating centre for some reflexes. A reflex is a fast, involuntary, unplanned sequence of actions that occurs in response to a particular stimuli.

Question 64

Differentiate between:
- Spinal reflex
- Cranial reflex
- Somatic reflex
- Autonomic reflec

Answer 64

• When integration takes place in the spinal cord grey
  matter, the reflex is a spinal reflex.
• It integration occurs in the brainstem rather than the
  spinal cord, the reflex is called a cranial reflex.
• Somatic reflex involves contraction of skeletal muscles.
• Autonomic (visceral) reflexes generally are not
  consciously perceived. They involve responses of smooth
  muscle, cardiac muscle, and glands.

Question 65

Define what a reflex arc is.

Answer 65

The pathway followed by nerve impulses that produce a reflex is a reflex arc (reflex circuit).

Question 66

What are the five functional components of a reflex arc?

Answer 66

• Sensory receptor
• Sensory neuron
• Integrating centres
• Motor neuron
• Effector

Question 67

Define what the sensory receptor is in relation to the reflex arc.

Answer 67

The distal end of the sensory neuron or an associated sensory structure serves as a sensory receptors. It responds to a specific stimulus – A change in the internal or external environment – by producing a graded potential called a generator (or receptor) potential. If a generator potentials reaches the threshold level of depolarization, it will trigger one or more nerve impulses in the sensory neuron.

Question 68

Define what the sensory neuron is in relation to the reflex arc.

Answer 68

The nerve impulses propagate from the sensory receptor along the axon of the sensory neuron to the axon terminals, which are located in the grey matter of the spinal cord or brainstem. From here, relay neurons send nerve impulses to the area of the brain that allows conscious awareness that the reflex has occurred.

Question 69

Explain what the integrating centre is in relation to the reflex arc.

Answer 69

One or more regions of grey matter within the CNS acts as an integrating centre. In the simplest type of reflex, the integrating centre is a single synapse between a sensory neuron and a motor neuron.

Question 70

Differentiate between monosynaptic reflex arc and polysynaptic reflex arc.

Answer 70

A reflex pathway having only one synapse in the CNS is termed as monosynaptic reflex arc.
A polysynaptic reflex arc involves more than two types of neurons and more than one CNS synapse.

Question 71

Explain what motor neurons are in relation to the reflex arc.

Answer 71

Impulses triggered by the integrating centre propagate out of the CNS along a motor neuron to the part of the body that will respond.

Question 72

Explain what the effector is in relation to the reflex arc. Differentiate between the somatic reflex and the autonomic reflex.

Answer 72

The part of the body that responds to the motor nerve impulse, such as a muscle or gland, is the effector. Its action is called a reflex. If the effector is a skeletal muscle, the reflex is a somatic reflex. If the effector is smooth muscle, cardiac muscle, or a gland, the reflex is an autonomic (visceral) reflex.

Question 73

Explain what the stretch reflex is.

Answer 73

The stretch reflex causes contraction of a skeletal muscle (the effector) in response to stretching of the muscle. This type of reflex occurs via a monosynaptic reflex arc. Stretch reflexes can be elicited by tapping on tendons attached to muscles at the elbow, wrist, knee, and ankle joints. The stretch reflex can also help maintain postures.

Question 74

A stretch reflex operates as follow:

Answer 74

• Slight stretching of a muscle stimulates sensory
  receptors in the muscle called muscle spindle. The
  spindle monitors changes in the length of the muscle
• In response to being stretched, a muscle spindle
  generates one or more nerve impulses that propagate
  along a somatic sensory through the posterior root of
  the spinal nerve and into the spinal cord.
• In the spinal cord (integrating centre), the sensory
  neuron makes an excitatory synapse with, and thereby
  activates a motor neuron in the anterior grey horn.
• If the excitation is strong enough, one or more nerve
  impulses arises in the motor neuron and propagates
  along its axon, which extends from the spinal cord into
  the anterior root and through peripheral nerves to the
  stimulated muscles. The axon terminals of the motor
  neuron from neuromuscular junctions with skeletal
  muscle fibers of the stretch muscle.
• Acetylcholine released by nerve impulses at the
  neuromuscular junction triggers one or more muscle
  action potentials in the stretched muscle (effector), and
  the muscle contracts.Thus, muscle stretch is followed by
  muscle contraction, which relieves the stretching.

Question 75

Explain what ipsilateral reflex is.

Answer 75

In the reflex arc, sensory nerve impulses enter the spinal cord on the same side from which motor nerve impulses leave it. This arrangement is called an ipsilateral reflex. All monosynaptic reflexes are ipsilateral.

Question 76

Explain what muscle tone is.

Answer 76

By adjusting how vigorously a muscle spindle responds to stretching, the brain sets an overall level of muscle tone, which is the small degree of contraction present while the muscle is at rest.

Question 77

How does reflex help avert injury?

Answer 77

Because the stimulus for the stretch reflex is stretching of muscle, this reflex helps avert injury by preventing over stretching of muscles.

Question 78

How does the antagonistic muscle operates at the stretch reflex?

Answer 78

A polysynaptic reflex arc to the antagonistic muscles operates at the same time with the stretch reflex.

Question 79

Explain what the reciprocal innervation is.

Answer 79

The components of a neural circuit simultaneously causes contraction of one muscle and relaxation of its antagonists, it is termed reciprocal innervation. They prevent conflict between opposing muscles and is vital in coordinating body movements.

Question 80

Explain what the tendon reflex is.

Answer 80

The tendon reflex operates as a feedback mechanism to control muscle tension by causing muscle relaxation before muscle force becomes so great to tendons might be torn. Tendon reflex can override the stretch reflex when tension is great. The tendon reflex is ipsilateral.

Question 81

Explain what the tendon organs are.

Answer 81

The sensory receptor for the tendon reflex are called tendon (golgi tendon) organs, which lie within a tendon near its junction with a muscle. Tendon organs detect and respond to changes in muscle tension that are caused by passive stretch or muscular contraction.

Question 82

The tendon reflex operates as follow:

Answer 82

• As the tension applied to a tendon increases, the tendon
  organ (sensory receptor) is stimulated.
• Nerve impulses arise and propagate into the spinal cord
  along a sensory neuron.
• Within the spinal cord (integrating centre), the sensory
  neuron activates an inhibitory interneuron that synapses
  with a motor neuron.
• The inhibitory neurotransmitter inhibits the motor
  neuron, which then generates fewer nerve impulse.
• The muscle relaxes and relies excess tension.

Question 83

How does the tendon reflex protect the tendon and muscle from damage?

Answer 83

As tension on the tendon organ increases, the frequency of inhibitory impulses increases; inhibition of the motor neurons to the muscle developing excess tension causes relaxation of the muscle. In this way, the tendon reflex protects the tendon and muscle from damage due to excessive tension.

Question 84

How does the excitatory interneuron work with the sensory neurons of the tendon organs?

Answer 84

The sensory neuron from the tendon organ also synapses with an excitatory interneurons in the spinal cord. The excitatory interneurons in turn synapses with motor neurons controlling antagonistic muscles. Thus, while the tendon reflex brings about relaxation of the muscle attached to the tendon organ, it also triggers contraction of antagonists.

Question 85

Explain what the flexor reflex is.

Answer 85

Another reflex involving a polysynaptic reflex arc results when, for instance, you step on a tact. In response to painful stimuli, you immediately withdraw your leg. This reflex is called a flexor reflex or withdrawal reflex. The flexor reflex is ipsilateral.

Question 86

The flexor reflex operates as follow.:

Answer 86

• Stepping on a tack stimulates the dendrites (sensory)
  receptor of a pain sensitive neuron.
• This sensory neuron then generates nerve impulses,
  which propagate into the spinal cord.
• Within the spinal (integrating centre), the sensory neuron
  activates interneurons that extend to several spinal cord
  segments.
• The interneurons activate motor neurons in several
  spinal cord segments. As a result, a motor neuron
  generates nerve impulses, which propagates toward the
  axon terminals.
• Acetylcholine released by the motor neuron causes the
  flexor muscles in the thigh (effectors) to contract,
  producing withdrawal of the leg. This reflex is protective
  because contraction of flexor muscles moves a limb away
  from the source of a possibly damaging stimulus.

Question 87

How does the flexor reflex use polysynaptic reflex arc?

Answer 87

The flexor reflex also illustrates another feature of polysynaptic reflex arcs. Moving your entire lower and upper limb away from a painful stimuli involves contraction of more than one muscle groups. Several motor neurons must simultaneously convey impulses to several limb muscles.

Question 88

Explain what an intersegmental reflex arc is.

Answer 88

Because nerve impulses from one sensory neuron ascend and descend in the spinal cord and activate interneurons in several segments of the spinal cord, this type of reflex is called an intersegmental reflex arc. Through intersegmental reflex arcs, a single sensory neuron can activate several motor neurons.

Question 89

Pain impulses may also initiate a crossed extensor reflex to help you maintain your balance; it operates as follow:

Answer 89

• Stepping on a tack stimulates the sensory receptor of a
  pain sensitive neuron in the right foot.
• This sensory neuron then generates nerve impulse,
  which propagates into the spinal cord.
• Within the spinal cord, the sensory neuron activates
  several inteneurons that synapse with motor neurons on
  the left side of the spinal cord in several spinal cord
  segments. Thus, incoming pain signals cross to the
  opposite side through interneurons at that level, and at
  several levels above and below the point of entry into the
  spinal cord.
• The interneuron excite motor neurons in several spinal
  cord segments that innervate extensor muscles. The
  motor neurons generate more nerve impulse, which
  propagate toward the axon terminals.
• Acetylcholine released by the motor neurons causes
  extensor muscles in the thigh (effector) of the
  unstimulated left limb to contract, producing extension
  of the left leg. In this way, weight can be placed on the
  foot that must now support the entire body.

Question 90

Explain what contralateral reflex arc mean.

Answer 90

The crossed extensor reflex involves a contralateral reflex arc, meaning sensory impulses enter one side of the spinal cord and motor impulses exit on the opposite side. If both sets of muscles contracted at the same time, the two sets of muscles would pull on the bones in opposite directions, which might immobilize the limb. Because of the reciprocal innervation, one set of muscles contracts while the other relaxes.

Question 91

What does your somatic nervous system consists of?

Answer 91

It consists of somatic motor neurons that innervate the skeletal muscles of the body.

Question 92

Differentiate between excitation and paralysis in somatic nervous system.

Answer 92

When a somatic motor neuron stimulates a skeletal muscle, it contracts; the effect is always excitation.
If somatic motor neurons cease to stimulate a skeletal muscle, the result is a paralyzed, limp muscle that has no muscle tone.

Question 93

How does your somatic motor neuron respond? What does it involve when moving?

Answer 93

The somatic nervous system usually operates under voluntary control. Voluntary control of movement involves motor areas of the cerebral cortex that activate somatic motor neurons whenever you have a desire to move.

Question 94

When is a situation when the somatic nervous system is not voluntary?

Answer 94

The somatic nervous system is not always voluntary. The somatic motor neurons that innervate skeletal muscles involve in postures, balance, breathing, and somatic reflex are involuntarily controlled by integrating centres in the brainstem and spinal cord.

Question 95

What does the autonomic nervous system regulate? What are they called?

Answer 95

It regulates cardiac muscle, smooth muscle, and glands. These tissues are often referred to as visceral effectors because they are usually associated wit hthe viscera of the body.

Question 96

What does the autonomic nervous system consists of?

Answer 96

The autonomic nervous system consists of autonomic motor neurons that regulate visceral activity in their effector tissues.

Question 97

What happens when the nerves in the autonomic nervous system is damaged?

Answer 97

Tissues innervated by the ANS often function to some extent even if their nerve supply is damaged.

Question 98

How does the autonomic nervous system controlled?

Answer 98

The ANS usually operates without conscious control.

Question 99

Explain what a biofeedback is.

Answer 99

Biofeedback is when monitoring devices display information about a body function such as heart rate or blood pressure, it enhances the ability to learn such conscious control.

Question 100

Explain what the interoceptors are in the autonomic nervous system.

Answer 100

The ANS can also receive sensory input from sensory neurons associated with interoceptors, sensory receptors located in blood vessels, visceral organs, muscles, and the nervous system that monitor conditions in the internal environment.

Question 101

What happens when an interoceptor is intensely activated? What would it feel like?

Answer 101

Intense activation of interoceptor may produce conscious sensations. Two examples of perceived visceral sensations are pain sensations form damaged visceral and angina pectoris (chest pains).

Question 102

How is the autonomic motor neurons related to limbic system?

Answer 102

Signals from the somatic senses and special senses acting via the limbic system, also influences responses of autonomic motor neurons. For example, seeing a car about to hit you will increase your heart rate.

Question 103

What are the two division of the autonomic nervous system?

Answer 103

• The sympathetic nervous system
• The parasympathetic nervous system

Question 104

Explain what a dual innervation is.

Answer 104

Most organs receive nerves from both the sympathetic and parasympathetic nervous system division, an arrangement known as dual innervation. In general, one division stimulates the organ to increase its activity (excitation), and the other division decreases the organs activity (inhibition).

Question 105

Differentiate the sympathetic and the parasympathetic nervous system in terms of what their known for the most.

Answer 105

The sympathetic nervous system promotes the fight or flight response, which prepares the body for emergency situation.
The parasympathetic nervous system enhances rest and digest activities, which conserve and restore body energy during times of rest and restore body energy during times of rest or digesting a meal.

Question 106

Explain what the enteric nervous system (ENS) is.

Answer 106

Its operation is involuntary. The ENS contains sensory neurons, inteneurons, and motor neurons. ENS monitor chemical changes within the GI tract as well as the stretching of its walls.
ENS govern contraction of GI tract smooth muscle an secretion of GI tract glands.

Question 107

What does the autonomic motor pathway consists of?

Answer 107

Most autonomic motor pathways consists of two motor neurons in series; one following the other.

Question 108

How does the motor neuron in the autonomic motor pathway work?

Answer 108

The first neuron has its cell body in the CNS; its myelinated axon extends from the CNS to an autonomic ganglion. The cell body of the second neuron is also in the same autonomic ganglion; its unmyelinated axon extends directly from the ganglion to the effector.

Question 109

Explain what the chromaffin cells are.

Answer 109

In some autonomic pathways, the first motor neuron extends to specialized cells called chromaffin cells in the adrenal medullae rather than an autonomic ganglion.
Chromaffin cells secrete the neurotrnasmitters epinephrine and norepinephrine.

Question 110

Explain what the chromaffin cells are.

Answer 110

In some autonomic pathways, the first motor neuron extends to specialized cells called chromaffin cells in the adrenal medullae rather than an autonomic ganglion.
Chromaffin cells secrete the neurotrnasmitters epinephrine and norepinephrine.

Question 111

Differentiate between what the somatic motor neuron and autonomic motor neuron release.

Answer 111

All somatic motor neurons release only acetylcholine as their neurotransmitter, but autonomic motor neurons release either acetylcholine or norepinephrine.

Question 112

Differentiate between the preganglionic neuron and the postganglionic neuron.

Answer 112

The first of the two motor neuron in any autonomic motor pathway is called a preganglionic neuron. Its cell body is in the brain or spinal cord; its axons exits the CNS as part of a cranial or spinal nerve. The axon of a preganglionic neuron is a small diameter, myelinated type B fibers that usually extends to an autonomic ganglion, where it synapses with a postganglionic neurons, the second neuron in the autonomic motor pathway.
The post ganglionic neuron lies entirely outside of the CNS in the PNS. Its cell body and dendrites are located in an autonomic ganglion, where it forms synapse with one or more preganglionic axons.
The axons of a postganglionic neuron is a small diameter, unmyelinated type C fibers that terminates in a visceral effector.

Question 113

Where does the preganglionic neuron and the autonomic ganglia convey to and from?

Answer 113

Preganglionic neurons convey nerve impulses from the CNS to autonomic ganglia, and postganglionic neurons relay the impulses from autonomic ganglia to visceral effectors.

Question 114

Explain what the thoracolumbar division is and how the thoracolumbar outflow relate.

Answer 114

In the sympathetic division, the preganglionic neurons have their cell bodies in the lateral horns of they grey matter in the 12 thoracic segments and the first two (sometimes three) lumbar segments of the spinal cord. For this reason, the sympathetic is also called the thoracolumbar division, and the axons of the sympathetic preganglionic neurons are known as the thoracolumbar outflow.

Question 115

Explain what the craniosacral division is and how the craniosacral outflow relate.

Answer 115

Cell bodies of preganglionic neurons of the parasympathetic division are located in the nuclei of four cranial nerves in the brainstem (III, VII, IX, and X) and in the lateral grey matter of the second through fourth sacral segments of the spinal cord. Hence, the parasympathetic division is also known as the craniosacral division, and the axons of the parasympathetic preganglionic neurons are referred to as the craniosacral outflow.

Question 116

Explain what two major groups of the autonomic ganglia is.

Answer 116

The two major groups of autonomic ganglia are: sympathetic ganglia, which are components of the sympathetic divisions of the ANS, and parasympathetic ganglia, which are components components of the parasympathetic division of the ANS.

Question 117

Explain what the sympathetic ganglia is and what are the two types of sympathetic ganglia are.

Answer 117

They are the sites of synapses between sympathetic preganglionic and postganglionic neurons. The two types of sympathetic ganglia are:
- Sympathetic trunk
- Prevertebral (collateral) ganglia

Question 118

Explain what the sympathetic trunk is.

Answer 118

Also called vertebral chain ganglia or paravertebral ganglia. They lie in a vertical row on either side of the vertebral column. These ganglia extend fro mthe base of the skull to the coccyx. Post ganglionic axons from sympathetic trunk ganglia primarily innervate organs above the diaphragm, such as head, neck, and shoulders, and heart.

Question 119

Explain what the prevertebral (collateral) ganglia is.

Answer 119

It lies anterior to the vertebral column and close to the large abdominal arteries. In general, postganglionic axons from prevertebral ganglia innervate organs below the diaphragm.

Question 120

Explain what the parasympathetic ganglia is. How is the terminal (intramural) ganglia related?

Answer 120

Preganglionic axons of the parasympathetic division synapse with postganglionic neurons in terminal (intramural) ganglia. Most of these ganglia are located close to or actually within the wall of the visceral organ. Terminal ganglia in the head have specific names.

Question 121

Explain what the postganglionic neuron is. Where does it connect to?

Answer 121

Once axons of sympathetic preganglionic neurons pass to sympathetic trunk ganglia, they may connect with postganglionic neurons in one of the following:
- An axons may synapse with postganglionic neurons in
the ganglion it first reaches.
- An axon may ascend or descend to a higher or lower
ganglion before synapsing with post ganglionic neurons.
The axons of incoming sympathetic preganglionic
neurons pass up or down the sympathetic trunk from
ganglion to ganglion.
- An axon may continue, without synapsing, through the
sympathetic trunk ganglion to end at a prevertebral
ganglion and synapse with postganglionic neurons there.
- An axons may also pass, without synapsing, through the
sympathetic trunk ganglion and a prevertebral ganglion
and then extend to chromaffin cells of the adrenal
medullae that are functionally similar to sympathetic
postganglionic neurons.

Question 122

Explain what the autonomic plexuses.

Answer 122

In the thorax, abdomen, and pelvis, axons of both sympathetic and parasympathetic neurons form tangled networks called autonomic plexuses, many at which lie along major arteries. The autonomic plexuses also may contain sympathetic ganglia and axons of the autonomic neurons.

Question 123

What are the two major plexuses in the thorax are?

Answer 123

The major plexuses in the thorax are the cardiac plexus, which supplies the heart, and the pulmonary plexus, which supplies the bronchial tree.

Question 124

Explain what the celiac (solar) plexus is.

Answer 124

The celiac plexus is the largest autonomic plexus and surrounds the celiac trunk. It contains two large celiac ganglia, two aorticorenal ganglia, and a dense network of autonomic axons and is distributed to the stomach, spleen, pancreas, liver, gallbladder, kidneys, adrenal medullae, testes, and ovaries.

Question 125

Explain what the superior mesenteric plexus is.

Answer 125

The superior mesenteric plexus contains the superior mesenteric ganglion and supplies the small and large intestines.

Question 126

Explain what the inferior mesenteric plexus is.

Answer 126

The inferior mesenteric plexus contains the inferior mesenteric ganglion, which innervates the large intestines.

Question 127

Explain what the hypogastric plexus.

Answer 127

Axons of some sympathetic postganglionic neurons from the inferior mesenteric ganglion also extends through the hypogastric plexus, which is anterior to the fifth lumbar vertebrae, to supply the pelvic viscera.

Question 128

Explain what the renal plexus is.

Answer 128

The renal plexus contains the renal ganglion and supplies the renal arteries within the kidneys and ureters.

Question 129

Explain what the white rami is?

Answer 129

Cell bodies of the sympathetic preganglionic neurons are part of the lateral grey horns of all thoracic segments and of the lateral grey horns of all thoracic segments and of the first two lumbar segments of the spinal cord. The preganglionic axons leave the spinal cord along with the somatic motor neurons at the same segment level. After exiting through the intervertebral foramina, the myelinated preganglionic sympathetic pathway called a white ramus before passing the nearest sympathetic trunk ganglion on the same side.

Question 130

Explain what a white rami communicates are.

Answer 130

A collective group of white rami are called the white rami communicantes. They are structures containing sympathetic preganglionic axons that connect the anterior ramus of the spinal nerve with the ganglia of the sympathetic trunk.
Only the thoracic and first two or three lumbar nerves have white rami communicantes.

Question 131

Explain what the sympathetic trunk ganglia is.

Answer 131

The paired sympathetic trunk ganglia are arranged anterior and lateral of the vertebral column, one on either side. Typically, there are 3 cervical, 11 or 12 thoracic, 4 or 5 lumbar, 4 or 5 sacral sympathetic trunk ganglia, and 1 coccygeal ganglion.
The sympathetic trunk ganglion receive preganglionic axons only from the thoracic and lumbar segments of the spinal cord.

Question 132

Differentiate between the superior cervical ganglion, the middle cervical ganglion, and inferior cervical ganglion.

Answer 132

Post ganglionic neurons leaving the superior cervical ganglion serve the head and heart. Post ganglionic neurons leaving the middle cervical ganglion and the inferior cervical ganglion innervate the heart and blood vessels of the neck, shoulder, and upper limbs.

Question 133

What are the four way the axons leave the sympathetic trunk?

Answer 133

• They enter spinal nerves
• They can form cephalic periarterial nerve
• They can form sympathetic nerves
• They can form splanchnic nerves

Question 134

Explain what the grey ramus is.

Answer 134

Some of the sympathetic preganglionic neurons synapse with postganglionic neurons in the sympathetic trunk, either in the ganglion at the level of entry or in a ganglion farther up and down the sympathetic trunk. The axons of some of these postganglionic neurons leave the sympathetic trunk by entering a short pathway called a grey ramus and then mere with the anterior ramus of a spinal nerve.

Question 135

Explain what the grey rami communicantes is.

Answer 135

Grey rami communicantes are structures containing sympathetic postganglionic axons that connect the ganglia of the sympathetic trunk to spinal nerves.
Grey rami communicantes outnumber the white rami because there is a grey ramus leading to each of the 31 pairs of spinal nerves.

Question 136

Explain what the cephalic periarterial nerves are.

Answer 136

Some sympathetic preganglionic neurons that enter the sympathetic trunk ascend to the superior cervical ganglion, where they synapse with post ganglionic neurons leave the sympathetic trunk by forming cephalic periarterial nerves, nerves that extend to the head by wrapping around and following the course of carious arteries that pass from the neck to the head.

Question 137

Where does the cephalic periarterial nerve innervate with?

Answer 137

Cephalic periarterial nerves provide sympathetic innervation to visceral effectors in the skin of the face, as well as other visceral effectors of the head.

Question 138

Explain what the sympathetic nerves are.

Answer 138

Some of the incoming sympathetic preganglionic neurons synapse with postganglionic neurons in one or more ganglia of the sympathetic trunk. Then the axons of the postganglionic neurons leave the trunk by forming sympathetic nerves that extend to visceral effectors in the thoracic cavity.

Question 139

Explain what the sympathetic nerves to the heart are.

Answer 139

They consists of axons of preganglionic neurons that enter the sympathetic trunk and then form synapses with postganglionic neurons in the superior, middle, and inferior cervical ganglia and first through fourth thoracic ganglia.
From these ganglia, axons of the postganglionic neurons exit the sympathetic trunk by forming sympathetic nerves that enter the cardiac plexus to supply the heart.

Question 140

Explain what the sympathetic nerves of the lungs are.

Answer 140

Sympathetic innervation of the lungs consist of axons of preganglionic neurons that enter the sympathetic trunk and then form synapses with postganglionic neurons in the second through fourth thoracic ganglia. From these ganglia axons of the sympathetic postganglionic neurons exit the trunk by forming sympathetic nerves that enter the pulmonary plexus to supply the smooth muscle of the bronchi and bronchioles of the lungs.

Question 141

Explain what splanchnic nerves are.

Answer 141

Some sympathetic preganglionic axons pass through the sympathetic trunk without terminating in it. Beyond the trunk, they form nerves known as splanchnic nerves, which extends to outlying prevertebral ganglia.

Question 142

Explain the splanchnic nerves to the abdominopelvic organs are.

Answer 142

Most sympathetic preganglionic axons that enter splanchnic nerves are destined to synapse with sympathetic post ganglionic neurons in the prevertebral ganglia that supply the organs of the abdominopelvic cavity.

Question 143

Explain what the splanchnic nerves to the adrenal medullae are.

Answer 143

Some sympathetic preganglionic axons pass, without synapsing, through the sympathetic trunk, greater splanchnic nerve, and celiac ganglion, and then extend to chromaffin cells in the adrenal medullae of the adrenal gland.

Question 144

Differentiate between the adrenal medullae and chromaffin cells to the sympathetic postganglionic neurons.

Answer 144

The adrenal medullae are modified sympathetic ganglia, and the chromaffin cells are similar to sympathetic postganglionic neurons, except they lack dendrites and axons. Rather than extending to another organ, these cells release hormones into the blood on stimulation by sympathetic preganglionic neurons, the chromaffin cells of the adrenal medullae release a mixture of catecholamine hormones.

Question 145

How much catecholamine hormones does the chromaffin and adrenal medullae release?

Answer 145

About 80% epinephrine, 20% norepinephrine, and a trace amount of dopamine.
These hormones circulate throughout the body and intensify responses elicited by sympathetic post ganglionic neurons.

Question 146

Where are the cell bodies of the parasympathtic preganglionic neurons are found?

Answer 146

They are found in nuclei in the brainstem and in the lateral grey matter of the second through fourth sacral segments of the spinal cord.
Their axons emerge as part of a cranial nerve or as part of the anterior root of a spinal nerve.

Question 147

Explain what the cranial parasympathetic outflow.

Answer 147

The cranial parasympathetic outflow consists of preganglionic axons that extends from the brainstem in four cranial nerves.

Question 148

Explain what the sacral parasympathetic outflow.

Answer 148

The sacral parasympathetic outflow consists of preganglionic axons in anterior root of the second through fourth sacral spinal nerves.

Question 149

What are the four pairs of cranial outflow ganglias?

Answer 149

The cranial outflow has four parts of ganglia and the ganglia associated with the vagus (x) nerves:
- Ciliary ganglia lie lateral to each optic (II) nerve near the
posterior aspects of the orbit. Postganglionic axons from
the ganglia innervate smooth muscle fibers in the
eyeball.
- Pterygopalatine ganglia are located lateral to the
sphenopalatine foramen, between the sphenoid and
palatine bones. They receive preganglionic axons from
the facial (VII) nerve and send postganglionic axons to the
nasal mucosa, palate, pharynx, and lacrimal glands.
- Submandibular ganglia are found near the ducts of the
submandibular salivary glands. They receive
preganglionic axons from the facial nerves and send
postganglionic axons to the submandibular and
sublingual salivary glands.
- Oric ganglia are situated just inferior to each foramen
ovale. They receive preganglionic axons form the
glossopharyngeal (IX) nerves and send postganglionic
axons to the parotid salivary glands.

Question 150

What does the sacral parasympathetic outflow consists of? Where do they branch out to?

Answer 150

The sacral parasympathetic outflow consists of preganglionic axons from the anterior roots of the second through fourth sacral spinal nerves.
As the preganglionic axons course through the sacral nerves, they branch off those nerves to form pelvic splanchnic nerves.

Question 151

What neurons does cholinergic receptor involve?

Answer 151

In the ANS, the cholinergic neurons include:
- All sympathetic and parasympathetic preganglion
neurons
- Sympathetic postganglionic neurons that innervate most
sweat glands
- All parasympathetic postganglionic neuron

Question 152

Where are acetylcholine (ACh) stored? How is it released?

Answer 152

They are stored in synaptic vesicles and released by exocytosis. It then diffuses across the synaptic cleft and binds with specific cholinergic receptors.

Question 153

Explain what cholinergic receptors are, what are the two types?

Answer 153

Cholinergic receptors are integral membrane proteins in the postsynaptic plasma membrane. The two types of cholinergic receptors, both of which bind ACh, are nicotine receptors and muscarinic receptors.

Question 154

Differentiate between nicotine receptors and muscarinic receptors.

Answer 154

Nicotine receptors are present in the plasma membrane of dendrites and cell bodies of both sympathetic and parasympathetic postganglionic neurons, the plasma membranes of chromaffin cells of the adrenal medullae, and in the motor end plate at the neuromuscular junction.
Muscarinic receptors are present in the plasma membranes of the effectors innervated by parasympathetic post ganglionic axons.

Question 155

What does acetylcholine (ACh) activate?

Answer 155

ACh activates both types of cholinergic receptors, nicotine and muscarinic receptors.

Question 156

Explain what adrenergic neurons are.

Answer 156

In the autonomic nervous system, adrenergic neurons release norepinephrine, also known as noradrenaline. Most sympathetic postganglionic neurons are adrenergic.

Question 157

Where is norepinephrine stored? How is it diffused?

Answer 157

Norepinephrine is stored in synaptic vesicles and released by exocytosis. Molecules of norepinephrine diffuse across the synaptic cleft and bind to specific adrenergic receptors on the postsynaptic membrane, causing either excitation or inhibition of the effector cells.

Question 158

Explain what adrenergic receptors are.

Answer 158

They bind both to norepinephrine and epinephrine. The norepinephrine can either be released as an neurotransmitter by sympathetic postganglionic neurons or released as a hormone into the blood by chromaffin cells of the adrenal medullae, epinephrine is released as a hormone.

Question 159

Explain what alpha receptors and beta receptors.

Answer 159

The two main types of adrenergic receptors are alpha receptors and beta receptors, which are found on visceral effectors innervated by most synaptic post ganglionic axons.
Cells of most effectors contain either alpha or beta receptors; some visceral effectors cells contain both.

Question 160

What hormones stimulate alpha receptors and beta receptors?

Answer 160

Norepinephrine stimulates alpha receptors more strongly than beta receptors. Epinephrine is a potent stimulator of both alpha and beta receptors.

Question 161

When does the activity of norepinephrine terminated?

Answer 161

The activity of norepinephrine at a synapse is terminated either when the norepinephrine is taken up by the axons that released it or when the norepinephrine is enzymatically inactivated by either catechol-O-methyltransferase or monoamien oxidase.

Question 162

What happens when norepinephrine lingers in the synaptic cleft?

Answer 162

Norepinephrine lingers in the synaptic cleft for a longer time. Thus, effectors triggered by adrenergic neurons typically are longer lasting than those triggered by cholinergic neurons.

Question 163

Differentiate between agonists and antagonists.

Answer 163

An agonist is a substance that binds to and activates a receptor, in the process mimicking the effects of a natural neurotransmitter or hormone.
An antagonist is a substance that binds to and blocks a receptor, thereby preventing a natural neurotransmitter or hormone from exerting its effects.

Question 164

Explain what the autonomic tone.

Answer 164

Most body organs receive innervation form both divisions of the ANS, which typically work in opposition to one another. The balance between sympathetic and parasympathetic activity called autonomic tone, it is regulated by the hypothalamus.
An increase in sympathetic tone has one effect and a decreased in sympathetic tone produces the opposite effect.

Question 165

What happens during physical and emotional stress?

Answer 165

During physical and emotional stress, the sympathetic division dominates the parasympathetic division. High sympathetic tone favours body functions than can support vigorous physical activity and rapid production of ATP. At the same time, the sympathetic division reduces body functions that favour the storage of energy.

Question 166

What does the activation of sympathetic division set in motion?

Answer 166

Activation of the sympathetic division and release of hormones by the adrenal medullae set in motion a series of physiological responses collectively called the fight-or-flight, which includes the following effects:
- The pupils of the eyes dilate
- Heart rate, forces of heart contraction, and BP increases
- The airway dilate, allowing faster movement of air into
and out of the lungs
- The blood vessels that supply the kidneys and
gastrointestinal tract and constricts, which decreases
blood flow through these tissues. The results is a
showing of urine formation and digestive activities, which
are not essential during exercise.
- Blood vessels that supply organs involved in exercise or
fighting off danger dilate, allowing greater blood flow
through the tissues.
- Liver cells perform glycogenolysis (breakdown of
glycogen to glucose), and adipose tissue cells perform
lipolysis (breakdown of triglycerides to fatty acids and
glycerol)
- Release of glucose by the liver increases blood glucose
level
- Processes that are not essential for meeting the stressful
situation are inhibited.

Question 167

What are the three reasons why the sympathetic stimulation longer lasting and more widespread than parasympathetic stimulation?

Answer 167

• Sympathetic postganglionic axons diverge more
  extensively as a result, many tissues are activated
  simultaneously.
• Acetylcholinesterase quickly inactivates acetylcholine, but
  norepinephrine lingers in the synaptic cleft for longer
  periods.
• Epinephrine and norepinephrine secreted into the blood
  from the adrenal medullae intensifying and prolong the
  responses caused by norepinephrine liberated from
  sympathetic postganglionic axons.

Question 168

How are norepinephrine and epinephrine destroyed?

Answer 168

These blood-borne hormones circulate throughout the body, affecting all tissues that have alpha and beta receptors. In time, blood borne norepinephrine and epinephrine are destroyed by enzymes in their liver.

Question 169

Explain what the parasympathetic response means.

Answer 169

The parasympathetic division enhances rest and digest activities. Parasympathetic responses support body functions than conserve and restore body energy during times of rest and recovery. In the quiet intervals between periods of exercise allows energy supplying food to be digested and absorbed. At the same time, parasympathetic responses reduce body functions that support physical activities.

Question 170

What are the five parasympathetic responses?

Answer 170

• Salivation
• Lacrimation
• Urination
• Digestion
• Defecation

Question 171

What are the three decrease response of parasympathetic divsion?

Answer 171

• Decreased heart rate
• Decreased diameter of airway
• Decreased diameter of the pupils

Question 172

Define what the autonomic (visceral) reflex is.

Answer 172

They are responses that occurs when nerve impulses pass through an autonomic reflex arc.

Question 173

Explain what components of an autonomic reflex arc.

Answer 173

• Sensory receptor: The sensory receptor in the autonomic
  reflex arc is the distal end of a sensory neuron, which
  responds to a stimulus and produces a change that will
  ultimately trigger nerve impulses. These sensory
  receptors are mostly associated with interoceptors.
• Sensory neurons: Conducts nerve impulses from
  receptors to the CNS.
• Integrating centre: Interneurons within the CNS relay
  signals from sensory neurons to motor neurons. The
  main integrating centres for most autonomic reflexes are
  located in the hypothalamus and brain stem. Some
  autonomic reflexed, such as those for urinating and
  defacation, have integrating centres in the spinal cord.
• Motor neurons: Nerve impulses triggered by the
  integrating centre propagates out of the CNS along
  motor neurons to an effector. In an autonomic reflex arc,
  two motor neurons connects the CNS.
• Effector: In an autonomic reflex arc, the effectors are
  smooth muscle, cardiac muscle, and glands, and the
  reflex is called an autonomic reflex.

Question 174

How is the hypothalamus related to the ANS?

Answer 174

The hypothalamus is the major control and integration centre of the ANS. The hypothalamus receives sensory input related to visceral functions, olfactory, and gustation, as well as changes in temperature, osmolarity, and levels of various substances in blood. It also receives input relating to emotions from the limbic system.

Question 175

How does the hypothalamus is related anatomically to both the sympathetic and parasympathetic division?

Answer 175

Anatomically, the hypothalamus is connected to both the sympathetic and parasympathetic divisions of the ANS by axons of neurons and dendrites and cell bodies in various hypothalamic nuclei.
The posterior and lateral parts of the hypothalamus controls the sympathetic divisions. The anterior and medial parts of the hypothalamus control the parasympathetic division.