Unit 3: Pt. 2 Flashcards
1
Q
How does the spinal cord and spinal nerves contribute to the homeostasis?
A
By providing quick, reflexive responsiveness to many stimuli.
2
Q
What are two layers of protection for our central nervous system?
A
- Vertebral column
- The meninges
3
Q
What is the space between the the meningeal membranes?
A
The cerebrospinal fluid.
4
Q
Explain what the vertebral column do for protection.
A
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.
5
Q
Explain what the meninges do and what are the three types?
A
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
6
Q
Explain what the epidural space is and what does it contain.
A
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.
7
Q
Explain what the Dura mater is.
A
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.
8
Q
Explain what the Arachnoid mater is.
A
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.
9
Q
Explain what the Pia mater is.
A
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.
10
Q
Explain what the denticulate ligaments.
A
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.
11
Q
Explain what the subarachnoid space is.
A
Located between the Arachnoid mater and Pia mater is a space called subarachnoid space, which contains shock absorbing cerebrospinal fluid.
12
Q
Explain what the spinal cord is.
A
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.
13
Q
Explain the difference between the cervical enlargement and the lumbar enlargement.
A
The cervical enlargement contains nerves that control the upper limbs.
The lumbar enlargement contains nerves that control the lower limbs.
14
Q
Explain what the conus medullaris is.
A
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.
15
Q
Explain what the filum terminate is.
A
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.
16
Q
Explain what the spinal nerves are.
A
Spinal nerves are the paths of communication between the spinal cord and specific regions of the body.
17
Q
How many spinal nerves are there and where are they lcoated?
A
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
18
Q
Explain what roots are and the two types.
A
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.
19
Q
What are the two main component of the internal part of the spinal cord?
A
White and grey matter.
20
Q
Differentiate between white matter and grey matter.
A
The white matter consists primarily of bundles of myelinated axons of neurons.
The grey matter contains unmyelinated neurons.
21
Q
Differentiate between the anterior median fissure and posterior median suculus.
A
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.
22
Q
Explain what the grey commissure is. And where the central canal is.
A
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.
23
Q
Explain what a nuclei is. Differentiate between sensory nuclei and motor nuclei.
A
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.
24
Q
Explain what horns are. Differentiate between the posterior grey horns and anterior grey horns.
A
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.
25
Explain what the lateral grey horns are and what is unique about them?
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.
26
Explain what tracts are. Differentiate between sensory (ascending) tracts and motor (descending) tracts.
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.
27
The following is how the spinal cord allows sensory input and motor output to be processed:
- 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.
28
How much white matter are then in the spinal cord?
The amount of white matter decreases from cervical to sacral segment of the spinal cord.
29
What are the two major reasons for the decrease of the shite matter in the spinal cord?
- 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.
30
Explain what spinal nerves are.
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.
31
What does the spinal nerve connect to?
Spinal nerves connect the CNS to sensory receptors, muscles, and glands in all parts of the body.
32
Does the spinal cord segment align with the corresponding vertebrae?
Not all spinal cord segments are aligned with their corresponding vertebrae.
33
Where does the pairs of the spinal cord emerge out of?
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.
34
What does mixed nerve mean?
Because the posterior root contains sensory axons and the anterior root contains motor axons, a spinal nerve is classified as a mixed nerve.
35
What are the three coverings of spinal nerves?
- Endoneurium
- Perineurium
- Epineurium
36
Explain where and what the endoneurium is.
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.
37
Explain the middle layer of the spinal nerves.
The perineurium is the middle layer. It is a thicker layer of connective tissue.
38
What is the outermost layer of the spinal nerve coverings?
The outermost covering over the entire spinal nerve is the epineurium. It consists of fibroblast and thick collagen fibers.
39
Explain what branches and ramis are.
A short distance after passing through its intervertebral foramen, a spinal nerve divides into several branches. These branches are known as rami.
40
Explain what the posterior (dorsal) ramus is.
The posterior (dorsal) ramus serves the deep muscle and skin of the posterior and anterior rami.
41
Explain what the meningeal branch is.
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.
42
What are plexus?
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.
43
What are the five named plexus'?
- Cervical plexus
- Brachial plexus
- Lumbar plexus
- Sacral plexus
- Coccycgeal plexus (smaller)
44
Explain what the intercostal nerves are.
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.
45
Explain the three main intercostal nerves.
- 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.
46
What does the posterior ramis of the intercostal nerves supply?
The posterior rami of the intercostal nerves supply the deep back muscles and skin of the posterior aspects of the thorax.
47
Explain what dermatomes are.
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.
48
Why is it important to know which spinal cord segments supply which?
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.
49
Why is it important to apply anesthetic drug to adjacent spinal nerves?
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.
50
Explain what the cervical plexus is.
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.
51
Explain what the brachial plexus is.
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.
52
Explain what the lumbar plexus is.
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.
53
Explain what the sacral and coccygeal plexus are.
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.
54
What are the two principal functions of the spinal cord to maintain homeostasis?
- Nerve impulse propagation
- Integration of information
55
What are the white and grey matter tracts jobs?
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.
56
The following are the functions of the spinal cord and the spinal nerves:
- 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.
57
What are the two main routes the nerve impulse propagates up the spinal cord to the brain?
- The spinothalamic tract
- The posterior column
58
Explain what the spinothalamic tract is.
The spinothalamic tract conveys nerve impulses for sensing pain, temperature, itch, and tickle.
59
Explain what the posterior column is.
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.
60
What is the sensory information integrated by?
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.
61
How do motor output travel down the spinal cord?
Motor output to skeletal muscles travel down the spinal cord in two types of descending pathways: Direct and indirect.
62
Differentiate between direct motor pathways and indirect motor pathways.
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.
63
Define what reflex is.
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.
64
Differentiate between:
- Spinal reflex
- Cranial reflex
- Somatic reflex
- Autonomic reflec
- 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.
65
Define what a reflex arc is.
The pathway followed by nerve impulses that produce a reflex is a reflex arc (reflex circuit).
66
What are the five functional components of a reflex arc?
- Sensory receptor
- Sensory neuron
- Integrating centres
- Motor neuron
- Effector
67
Define what the sensory receptor is in relation to the reflex arc.
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.
68
Define what the sensory neuron is in relation to the reflex arc.
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.
69
Explain what the integrating centre is in relation to the reflex arc.
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.
70
Differentiate between monosynaptic reflex arc and polysynaptic reflex arc.
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.
71
Explain what motor neurons are in relation to the reflex arc.
Impulses triggered by the integrating centre propagate out of the CNS along a motor neuron to the part of the body that will respond.
72
Explain what the effector is in relation to the reflex arc. Differentiate between the somatic reflex and the autonomic reflex.
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.
73
Explain what the stretch reflex is.
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.
74
A stretch reflex operates as follow:
- 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.
75
Explain what ipsilateral reflex is.
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.
76
Explain what muscle tone is.
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.
77
How does reflex help avert injury?
Because the stimulus for the stretch reflex is stretching of muscle, this reflex helps avert injury by preventing over stretching of muscles.
78
How does the antagonistic muscle operates at the stretch reflex?
A polysynaptic reflex arc to the antagonistic muscles operates at the same time with the stretch reflex.
79
Explain what the reciprocal innervation is.
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.
80
Explain what the tendon reflex is.
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.
81
Explain what the tendon organs are.
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.
82
The tendon reflex operates as follow:
- 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.
83
How does the tendon reflex protect the tendon and muscle from damage?
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.
84
How does the excitatory interneuron work with the sensory neurons of the tendon organs?
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.
85
Explain what the flexor reflex is.
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.
86
The flexor reflex operates as follow.:
- 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.
87
How does the flexor reflex use polysynaptic reflex arc?
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.
88
Explain what an intersegmental reflex arc is.
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.
89
Pain impulses may also initiate a crossed extensor reflex to help you maintain your balance; it operates as follow:
- 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.
90
Explain what contralateral reflex arc mean.
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.
91
What does your somatic nervous system consists of?
It consists of somatic motor neurons that innervate the skeletal muscles of the body.
92
Differentiate between excitation and paralysis in somatic nervous system.
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.
93
How does your somatic motor neuron respond? What does it involve when moving?
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.
94
When is a situation when the somatic nervous system is not voluntary?
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.
95
What does the autonomic nervous system regulate? What are they called?
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.
96
What does the autonomic nervous system consists of?
The autonomic nervous system consists of autonomic motor neurons that regulate visceral activity in their effector tissues.
97
What happens when the nerves in the autonomic nervous system is damaged?
Tissues innervated by the ANS often function to some extent even if their nerve supply is damaged.
98
How does the autonomic nervous system controlled?
The ANS usually operates without conscious control.
99
Explain what a biofeedback is.
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.
100
Explain what the interoceptors are in the autonomic nervous system.
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.
101
What happens when an interoceptor is intensely activated? What would it feel like?
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).
102
How is the autonomic motor neurons related to limbic system?
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.
103
What are the two division of the autonomic nervous system?
- The sympathetic nervous system
- The parasympathetic nervous system
104
Explain what a dual innervation is.
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).
105
Differentiate the sympathetic and the parasympathetic nervous system in terms of what their known for the most.
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.
106
Explain what the enteric nervous system (ENS) is.
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.
107
What does the autonomic motor pathway consists of?
Most autonomic motor pathways consists of two motor neurons in series; one following the other.
108
How does the motor neuron in the autonomic motor pathway work?
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.
109
Explain what the chromaffin cells are.
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.
110
Explain what the chromaffin cells are.
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.
111
Differentiate between what the somatic motor neuron and autonomic motor neuron release.
All somatic motor neurons release only acetylcholine as their neurotransmitter, but autonomic motor neurons release either acetylcholine or norepinephrine.
112
Differentiate between the preganglionic neuron and the postganglionic neuron.
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.
113
Where does the preganglionic neuron and the autonomic ganglia convey to and from?
Preganglionic neurons convey nerve impulses from the CNS to autonomic ganglia, and postganglionic neurons relay the impulses from autonomic ganglia to visceral effectors.
114
Explain what the thoracolumbar division is and how the thoracolumbar outflow relate.
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.
115
Explain what the craniosacral division is and how the craniosacral outflow relate.
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.
116
Explain what two major groups of the autonomic ganglia is.
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.
117
Explain what the sympathetic ganglia is and what are the two types of sympathetic ganglia are.
They are the sites of synapses between sympathetic preganglionic and postganglionic neurons. The two types of sympathetic ganglia are:
- Sympathetic trunk
- Prevertebral (collateral) ganglia
118
Explain what the sympathetic trunk is.
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.
119
Explain what the prevertebral (collateral) ganglia is.
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.
120
Explain what the parasympathetic ganglia is. How is the terminal (intramural) ganglia related?
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.
121
Explain what the postganglionic neuron is. Where does it connect to?
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.
122
Explain what the autonomic plexuses.
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.
123
What are the two major plexuses in the thorax are?
The major plexuses in the thorax are the cardiac plexus, which supplies the heart, and the pulmonary plexus, which supplies the bronchial tree.
124
Explain what the celiac (solar) plexus is.
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.
125
Explain what the superior mesenteric plexus is.
The superior mesenteric plexus contains the superior mesenteric ganglion and supplies the small and large intestines.
126
Explain what the inferior mesenteric plexus is.
The inferior mesenteric plexus contains the inferior mesenteric ganglion, which innervates the large intestines.
127
Explain what the hypogastric plexus.
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.
128
Explain what the renal plexus is.
The renal plexus contains the renal ganglion and supplies the renal arteries within the kidneys and ureters.
129
Explain what the white rami is?
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.
130
Explain what a white rami communicates are.
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.
131
Explain what the sympathetic trunk ganglia is.
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.
132
Differentiate between the superior cervical ganglion, the middle cervical ganglion, and inferior cervical ganglion.
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.
133
What are the four way the axons leave the sympathetic trunk?
- They enter spinal nerves
- They can form cephalic periarterial nerve
- They can form sympathetic nerves
- They can form splanchnic nerves
134
Explain what the grey ramus is.
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.
135
Explain what the grey rami communicantes is.
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.
136
Explain what the cephalic periarterial nerves are.
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.
137
Where does the cephalic periarterial nerve innervate with?
Cephalic periarterial nerves provide sympathetic innervation to visceral effectors in the skin of the face, as well as other visceral effectors of the head.
138
Explain what the sympathetic nerves are.
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.
139
Explain what the sympathetic nerves to the heart are.
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.
140
Explain what the sympathetic nerves of the lungs are.
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.
141
Explain what splanchnic nerves are.
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.
142
Explain the splanchnic nerves to the abdominopelvic organs are.
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.
143
Explain what the splanchnic nerves to the adrenal medullae are.
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.
144
Differentiate between the adrenal medullae and chromaffin cells to the sympathetic postganglionic neurons.
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.
145
How much catecholamine hormones does the chromaffin and adrenal medullae release?
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.
146
Where are the cell bodies of the parasympathtic preganglionic neurons are found?
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.
147
Explain what the cranial parasympathetic outflow.
The cranial parasympathetic outflow consists of preganglionic axons that extends from the brainstem in four cranial nerves.
148
Explain what the sacral parasympathetic outflow.
The sacral parasympathetic outflow consists of preganglionic axons in anterior root of the second through fourth sacral spinal nerves.
149
What are the four pairs of cranial outflow ganglias?
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.
150
What does the sacral parasympathetic outflow consists of? Where do they branch out to?
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.
151
What neurons does cholinergic receptor involve?
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
152
Where are acetylcholine (ACh) stored? How is it released?
They are stored in synaptic vesicles and released by exocytosis. It then diffuses across the synaptic cleft and binds with specific cholinergic receptors.
153
Explain what cholinergic receptors are, what are the two types?
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.
154
Differentiate between nicotine receptors and muscarinic receptors.
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.
155
What does acetylcholine (ACh) activate?
ACh activates both types of cholinergic receptors, nicotine and muscarinic receptors.
156
Explain what adrenergic neurons are.
In the autonomic nervous system, adrenergic neurons release norepinephrine, also known as noradrenaline. Most sympathetic postganglionic neurons are adrenergic.
157
Where is norepinephrine stored? How is it diffused?
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.
158
Explain what adrenergic receptors are.
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.
159
Explain what alpha receptors and beta receptors.
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.
160
What hormones stimulate alpha receptors and beta receptors?
Norepinephrine stimulates alpha receptors more strongly than beta receptors. Epinephrine is a potent stimulator of both alpha and beta receptors.
161
When does the activity of norepinephrine terminated?
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.
162
What happens when norepinephrine lingers in the synaptic cleft?
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.
163
Differentiate between agonists and antagonists.
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.
164
Explain what the autonomic tone.
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.
165
What happens during physical and emotional stress?
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.
166
What does the activation of sympathetic division set in motion?
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.
167
What are the three reasons why the sympathetic stimulation longer lasting and more widespread than parasympathetic stimulation?
- 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.
168
How are norepinephrine and epinephrine destroyed?
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.
169
Explain what the parasympathetic response means.
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.
170
What are the five parasympathetic responses?
- Salivation
- Lacrimation
- Urination
- Digestion
- Defecation
171
What are the three decrease response of parasympathetic divsion?
- Decreased heart rate
- Decreased diameter of airway
- Decreased diameter of the pupils
172
Define what the autonomic (visceral) reflex is.
They are responses that occurs when nerve impulses pass through an autonomic reflex arc.
173
Explain what components of an autonomic reflex arc.
- 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.
174
How is the hypothalamus related to the ANS?
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.
175
How does the hypothalamus is related anatomically to both the sympathetic and parasympathetic division?
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.
