Unit 3: Cranial system Pt. 3 Flashcards
1
Q
What are the five brain structures to form the brain?
A
- Telencephalon
- Diencephalon
- Mesencephalon
- Metencephalon
- Myelencephalon
2
Q
What does the telencephalon develop into?
A
It develops into the cerebrum and lateral ventricles.
3
Q
What does the diencephalon form?
A
It forms the thalamus, hypothalamus, epithalamus, and third ventricle.
4
Q
What does the metencephalon become?
A
It becomes the pons, cerebellum, and upper part of the fourth ventricle.
5
Q
what does the myelencephalon form?
A
It forms the medulla oblongata and the lower part of the fourth ventricle.
6
Q
What are the four major parts of the adult brain?
A
- Brainstem
- Cerebellum
- Diencephalon
- Cerebrum
7
Q
What is the largest part of the brain?
A
Cerebrum
8
Q
What protects the brain?
A
The cranium and the meninges
9
Q
Name the three meninges:
A
- Dura mater
- Arachnoid mater
- Pia mater
10
Q
What are the two layers of the dura mater?
A
- Periosteal layer
- Meningeal layer
11
Q
Name the three extensions of the dura mater that separates parts of the brain and what it separates:
A
- Falx cerebri: separates the two hemispheres of the
cerebrum - Falx cerebelli: separates the two hemispheres of the
cerebellum - Tentorium cerebelli: separates the cerebrum from the
cerebellum
12
Q
How does the blood flow through the brain and where does it brain into?
A
Blood flows to the brain mainly via the internal carotid and vertebral arteries, the dural venous sinuses drain in to the internal jugular veins to return blood from the head to the heart.
13
Q
How much does the brain represent the body? How much does the brain consume?
A
The brain represents only 2% of total body weight, but it consumes about 20% of total oxygen and glucose used by the body, even when you’re resting.
14
Q
What happens when there is an interruption in blood flow into the brain?
A
An interruption in blood flow for 1 to 2 minutes, impairs neuronal function, and total depravation of oxygen for about 4 minutes causes permanent damage. Because virtually no glucose is stored in the brain, the supply of glucose also must be continuous.
15
Q
Explain what the blood brain barrier is.
A
Consists mainly of tight junctions that seal together and endothelial cells of brain blood capillaries and a thick basement membrane that surrounds the capillaries. The process of many astrocytes press up against the capillaries and secrete chemicals that maintain the ‘tightness’ of the tight junctions.
16
Q
Why is the blood brain barrier important?
A
The blood brain barrier is a semi permeable substance that only allows certain things into the brain and keeping the bad stuff out.
17
Q
Explain what the cerebrospinal fluid is.
A
It is a clear, colourless liquid composed primarily of water that protects the brain and spinal cord from chemical and physical injuries. CSF continuously circulates through cavities in the brain and spinal cord and around the brain and spinal cord in the subarachnoid space.
18
Q
What does the cerebrospinal fluid contain?
A
It contains small amounts of oxygen, glucose, and other needed chemicals form the blood to neurons and neuroglia.
19
Q
Explain what the ventricles in the brain are.
A
Ventricles are cavities within the brain that are filled with cerebrospinal fluid.
20
Q
Name the ventricles in the brain and what are they?
A
There is one lateral ventricle in each hemisphere of the cerebrum. The third ventricle is a narrow, slitlike cavity along the midline superior to the hypothalamus and between the right and left halves of the thalamus. The fourth ventricle lies between the brainstem and the cerebellum.
21
Q
Explain what the septum pellucidum.
A
The lateral ventricles are separated by a thin membrane called the septum pellucidum.
22
Q
Explain the three functions of the cerebrospinal fluid.
A
- Mechanical protection: CSF serves as a shock absorbing
medium that protects the delicate tissues of the brain
and spinal cord from jolts that would otherwise cause
them to hit the bony walls of the cranial cavity and
vertebral canal. The fluid also buoys the brain so that it
floats in the cranial cavity. - Chemical protection: CSF provides an optimal chemical
environment for accurate neuronal signalling. Even slight
changes in the ionic compositions of CSF within the brain
can seriously disrupt production of action potentials and
post synaptic potentials. - Circulation: CSF is a medium for minor exchange of
nutrients and waste products between the blood and
adjacent nervous tissue.
23
Q
Explain where cerebrospinal fluid is produced form. And how its produced.
A
The majority of CSF production is from the choroid plexuses, networks of blood capillaries in the walls of ventricles.
Selected substances (mostly water) from the blood plasma, which are filtered from the capillaries, are secreted by the ependymal cells to produced the CSF. Because of the tight junctions between ependymal cells, materials entering CSF from choroid capillaries cannot leak between these cells, instead they must pass through the ependymal cells.
24
Q
Explain how the blood brain barrier and the blood cerebrospinal fluid barrier are similar.
A
They are similar in a way that they both only permit certain substances to enter the CNS. The blood cerebrospinal fluid barrier is also formed by tight junctions of ependymal cells.
25
How does the cerebrospinal fluid circulate.
The CSF flows from the choroid plexuses of each lateral ventricles flows into the third ventricles through two narrow, oval openings, the inter ventricular foramina. The fluid then flows through the aqueducts of the midbrain, which passes through the midbrain, into the fourth ventricle. CSF enters the subarachnoid space through the three openings in the roof of the fourth ventricles: a single median aperture and paired lateral aperture, one on each side.
26
How is the cerebrospinal fluid reabsorbed?
CSF is gradually reabsorbed into the blood stream through arachnoid vili, fingerlike extensions of the arachnoid mater that projects into the dural venous sinuses, especially the superior sagittal sinus. Because the rates of formation and reabsorption are the same, the pressure of CSF normally is constant. For the same reason, the volume of CSF remains constant.
27
Explain what the arachnoid granulation is.
A cluster of arachnoid vili is called an arachnoid granulation.
28
Where is the brainstem located? What does it consists of?
The brainstem is the part of the brain between the spinal cord and the diencephalon. It consists of three structures:
- Medulla oblongata
- Pons
- midbrain
Extending through the brainstem is the reticular formation, a netlike region of interspersed grey and white matter.
29
Explain what the medulla oblongata is.
Also called medulla, is continuous with the superior part of the spinal cord, it forms the inferior part of the brainstem.
The medulla begins at the foramen magnum and extends to the inferior border of the pons.
The medullas white matter contains all sensory (ascending) tracts and motor (descending) tracts that extends between the spinal cord and other parts of the brain.
30
Explain what the pyramids in the medulla is.
Some of the white matter forms bulges on the anterior aspects of the medulla. These protrusions, called the pyramids, are formed by the large corticospinal tracts that pass from the cerebrum to the spinal cord.
31
Explain what the decussation of pyramids are.
Just superior to the junction of the medulla with the spinal cord, 90% of the axons in the left pyramid cross to the right side, and 90% of the axons in the right pyramid cross to the left side. Explains why each side of the brain controls voluntary movements on the opposite side of the body.
32
What does the corticospinal tract control?
It controls voluntary movements of the limbs and trunk.
33
Differentiate between the cardiovascular (CV) centre and the medullary respiratory centre.
The medulla also contains several nuclei (a collection of neuronal cell bodies within the CNS). Some of these nuclei control body functions.
The cardiovascular centre regulates the rate and force of the heart beat and the diameter of blood vessles.
The medullary respiratory centre adjusts the basic rhythm of breathing.
34
Explain what the vomiting centre of the medulla is.
The vomiting centre of the medulla causes vomiting, the forcible expulsion of the contents of the upper gastrointestinal tract through the mouth.
35
Explain what the deglutition centre.
The deglutition centre of the medulla promotes deglutition (swallow) of a mass of food that has moved from the oral cavity of the mouth into the pharynx.
36
What does sneezing involve?
Sneezing involves spasmodic contraction of breathing muscles that forcefully expel air through the nose and mouth.
37
Explain what coughing involves.
Coughing involves a long drawn and deep inhalation and then a strong exhalation that suddenly sends a blast of air through the upper respiratory passages.
38
What does hiccuping invovle.
Hiccuping is caused by spasmodic contractions of the diaphragm that ultimately result in the production of a sharp sound of inhalation.
39
Explain what the olive is. What is the inferior olivary nuclues?
Just lateral to each pyramid is an oval shaped swelling called an olive. Within the dive is the inferior olivary nucleus, which receives input from the cerebral cortex, red nucleus of the midbrain, and spinal cord. Neurons of the inferior olivary nucleus extend their axons into the cerebellum, where they regulate the activity of cerebellar neurons.
40
Where is the nuclei associated with sensation, pressure, vibration, and conscious proprioceptors are located?
It is located in the posterior part of the medulla.
41
Differentiate between the gracile fasciculus and cuneate fasciculus.
Ascending sensory axons of the gracile fasciculus and the cuneate fasciculus, which are two tracts in the posterior columns of the spinal cord, form synapses in these nuclei.
42
Explain what the medial lemniscus and how the posterior column medial lemniscus pathway is related.
The axons ascend to the thalamus in a band of white matter called the medial lemniscus, which extends through the medulla, pons and the midbrain. The tracts of the posterior columns and the axons of the medial lemniscus are collectively known as the posterior column medial lemniscus.
43
Explain what the gustatory nucleus is.
The gustatory nucleus (taste) of the medulla is part of the gustatory pathway from the tongue to the brain; it receives gustatory input from the taste buds of the tongue.
44
Explain what the cochlear nuclei is.
The cochlear nuclei of the medulla are part of the auditory pathway from the inner ear to the brain; they receive auditory input from the cochlea of the inner ear.
45
Explain what the vestibular nuclei is.
The vestibular nuclei of the medulla and pons are components of the equilibirum pathway from the inner ear to the brain; they receive sensory information associated with equilibrium from proprioceptors in the vestibular apparatus of the inner ear.
46
What are the five pairs of cranial nerves the medulla is associated with?
- Vestibulochochlear (VIII) nerve
- Glossopharyngeal (IX) nerve
- Vagus (X) nerve
- Accessory (XI) nerves (cranial portion)
- Hypoglossal (XIII) nerve
47
Explain what the pons is.
The pons lies directly superior to the medulla and anterior to the cerebellum. The pons consists of both nuclei and tracts. It is a bridge that connects parts of the brain with one another. These connections are provided by bundles of axons. Some axons of the pons connect the right and left sides of the cerebellum. Others are part of ascending sensory tracts and descending motor tracts.
48
Explain the two major structural components of the pons.
the central region of the pons forms a large synaptic relay station consisting of scattered grey centres called the pontine nuclei.
The dorsal region of the pons is more like the other regions of the brainstem, the medulla and midbrain.
49
Explain what the pontine respiratory group is.
Also within the pons is the pontine respiratory group. The pontine respiratory group helps control breathing,
50
What are the four cranial nerves associated with the pons.
- Trigeminal (V) nerve
- Abducens (VI) nerve
- Facial (VII) nerve
- Vestibulocochlear (VIII) nerve
51
Explain what the midbrain is.
The midbrain or mesencephalon extends form the pons to the diencephalon. The aqueducts of the midbrain passes through the midbrain, connecting the third ventricles above with the fourth ventricle below. The midbrain contains both nuclei and tracts.
52
Explain what the cerebral peduncles are.
The anterior part of the midbrain contains paired bundles of axons known as the cerebral peduncles. The cerebral peduncles consists of axons of the corticospinal, corticobulbar, and corticopontine tracts, which conduct nerve impulses from motor areas in the cerebral cortex to the spinal cord, medulla, and pons.
53
Explain what the tectum and the superior colliculi is.
The posterior part of the midbrain, called the tactum. The two superior elevations, nuclei known as the superior colliculi, serves as reflux centres for certain visual activities.
The superior colliculi are also responsible for reflexes that govern movements of the head, eyes, and trunk in response to visual stimuli.
54
Explain what the inferior colliculi is.
The two inferior elevations, the inferior colliculi, are part of the auditory pathway, relaying impulses form the receptors for hearing in the inner ear to the brain. The superior and inferior colliculi are also reflex centres for the startle reflex.
55
Explain what the substantia nigra is.
The midbrain contains several other nuclei, including the left and right substantia nigra, which are large and darkly pigmented. Neurons that release dopamine, extending from the substantia nigra to the basal nuclei, help control subconscious muscle movements. Loss of these neurons is associated with parkinsons disease.
56
Explain what the red nuclei is.
Present in the midbrain is also the left and right red nuclei, which look reddish due to their rich blood supply and an iron containing pigment in their neuronal cell bodies.
Axons from the cerebral cortex form synapses in the red nuclei, which help control muscular movements.
57
What are the two pairs of cranial nerves associated with the midbrain?
- Occulomotor (III) nerve
- Troclear (IV) nerve
58
Explain what the reticular formation is.
Much of the brainstem consists of small clusters of neuronal cell bodies interspersed among small bundles of myelinated axons. The broad region where white matter and grey matter exhibit a netlike arrangement is known as the reticular formation. It extends from the superior part of the spinal cord, throughout the brainstem, and into the inferior part of the diencephalon.
59
Explain what the reticular activation system is.
Neurons within the reticular formation have both ascending (sensory) and descending (motor) functions. The ascending portion of the reticular formation is called the reticular activation system, which consists of sensory axons that projects to the cerebral cortex, both directly and through the thalamus.
60
Explain what the functions of the reticular activation formation (RAS).
- The most important function of the RAS is
consciousness. Visual and auditory stimuli and mental
activities can stimulate the RAS to help maintain
consciousness.
- The RAS is also active during arousal, or awakening from
sleep.
- Another function of RAS is to help maintain attention and
alertness.
- The RAS also prevents sensory overload by filtering out
insignificant information so that is does not reach
consciousness. Inactivation of the RAS produces sleep.
- The RAS also prevents sensory overload by filtering out
insignificant information so that it does not reach
consciousness.
61
Explain how a coma happens.
Damage to the RAs results in coma. In the lightest stages of coma, brainstem and spinal cord reflexes persists, but in the deepest states even those reflexes are lost, and if respiratory and cardiovascular controls are lost, the patient dies.
62
What helps regulate muscle tone?
The descending portion of the reticular activation system has connections to the cerebellum and spinal cord and helps regulate muscle tone. This portion of the RAS also assists in the regulation of heart rate, blood pressure and respiratory rate.
63
What is unique about the reticular activation system in terms of senses?
Even though the RAS receives input from the eyes, ears, and other sensory receptors, there is no input from receptors for the sense of smell.
64
Explain what the cerebellum is.
The cerebellum, second only to the cerebrum in size, occupies the inferior and posterior aspects of the cranial cavity. The cerebellum has a highly folded surface that greatly increases the surface area of its outer grey matter cortex, allowing for greater number of neurons. It contains nearly half of the neurons in the brain.
65
Where is the cerebellum located?
The cerebellum is posterior to the medulla and pons and inferior to the posterior portion of the cerebrum.
66
Explain what the transverse fissure is and how the tentorium cerebelli is related.
A deep groove known as the transverse fissure, along with tentorium cerebelli, which supports the posterior part of the cerebrum, separates the cerebellum from the cerebrum.
67
Explain what the vermis hemisphere is.
The central part of the cerebellums constricted area is the vermis hemispheres. Each hemisphere consists of lobes separated by deep and distinct fissures. The anterior lobe and posterior lobe governs subconscious aspects of the skeletal muscle movements.
The flocculonodular lobe on the inferior surface contributes to the equilibrium and balance.
68
Explain what the cerebellar cortex is.
The superficial layer of the cerebellum, the cerebellar cortex, consists of grey matter in a sense of slender, parallel folds called folia.
69
Explain what is deep in the grey matter and the white matter.
Deep to the grey matter are tracts of the white matter called arbour vitae that resembles branches of a tree. Even deeper, within the white matter, are the cerebellar nuclei, regions of the grey matter, are the carrying impulses from the cerebellum to other brain centres.
70
Explain what the three paired of cerebellar peduncles are.
Three paired cerebellar peduncles attach the cerebellum to the brainstem.
- The superior cerebellar peduncles contains axons that
extends from the cerebellum to the red nuclei of the
midbrain and to several nuclei of the thalamus.
- The middle cerebellar peduncles are the largest
peduncles; their axons carry impulses for voluntary
movements form the pontine nuclei into the cerebellum.
- The inferior cerebellar peduncles
71
Explain what the inferior cerebellar peduncles consists.
- Axons of the spinocerebellar tracts that carry sensory
information into the cerebellum from proprioceptors in
the trunk and limbs.
- Axons from the vestibular apparatus of the inner ear and
from the vestibular nuclei of the medulla and pons that
carry sensory information into the cerebellum from
proprioceptors in the head.
- Axons from the inferior olivary nucleus of the medulla
that enters the cerebellum and regulate the activity of
cerebellar nueorons.
- Axons that extend from the cerebellum to the vestibular
nuclei from the medulla and pons
- Axons that extend from the cerebellum to the reticular
formation.
72
Explain what the primary function of the cerebellum is.
The primary function of the cerebellum is to evaluate how well movements initiated by motor areas in the cerebrum are actually being carried out. When movements initiated by the cerebral motor areas are not being carried out correctly, the cerebellum detects the discrepancies. It then sends a feedback signal to motor areas of the cerebral cortex, via its connections to the thalamus. The feedback signals helps correct the errors. The cerebellum is the main brain region that regulates posture and balance.
73
Explain what the diencephalon is.
The diencephalon forms a central core of the brain tissue just superior to the midbrain. It is almost completely surrounded by the cerebral hemisphere and contains numerous nuclei involved in a wide variety of sensory and motor processing between higher and lower brain centres.
The diencephalon extends form the brainstem to the cerebrum and surrounds the third ventricle; it includes the thalamus, hypothalamus, and epithalamus.
74
Explain what the thalamus is.
The thalamus makes up 80% of the diencephalon, consists of paired oval masses of grey matter organized into nuclei with interspersed tracts of white matter.
A bridge of grey matter called the inter thalamic adhesion joins the right and left halves of the thalamus in about 70% of human brains.
A vertical Y shaped sheet of white matter called the internal medullary lamina divides the grey matter of the right and left sides of the thalamus.
Axons that connects the thalamus and cerebral cortex pass through the internal capsule, a thick bend of white matter lateral to the thalamus.
75
Why is the thalamus important?
The thalamus is the major relay station for most sensory impulses that reach the primary sensory area of the cerebral cortex from the spinal cord and brainstem.
The thalamus also contributes to motor functions by transmitting information from the cerebellum and basal nuclei to the primary motor area of the cerebral cortex.
The thalamus also plays a role in the maintenance of consciousness.
76
What are the seven major groups of nuclei on each side of the thalamus?
- Anterior nucleus
- Medial nuclei
- Nuclei in the lateral group
- Five nuclei are part of the ventral group
- Intralaminar nuclei
- Midline nucleus
- Reticular nucleus
77
Explain what the anterior nucleus of the thalamus does.
The anterior nucleus receives input from the hypothalamus and sends output to the limbic system. It functions in emotions and memory.
78
Explain what the medial nuclei of the thalamus does.
The medial nuclei receives input from the limbic system and basal nuclei and send output to the cerebral cortex. They function in emotions, learning, memory, and cognition.
79
Explain what the lateral group of the thalamus does.
Nuclei in the lateral group receive input from the limbic system, superior colliculi, and cerebral cortex and send output to the cerebral cortex.
The lateral dorsal nucleus functions in the expression of emotions.
The lateral posterior nucleus and pulvinar nucleus help integrate sensory information.
80
Explain what five nuclei of the ventral group of the thalamus.
- The ventral anterior nucleus receives input from the
basal nuclei and sends output to motor areas of the
cerebral cortex; it plays a role in movement control.
- The ventral lateral nucleus receives input from the
cerebellum and basal nuclei and sends output to motor
areas of the cerebral cortex; it also plays a role in
movement control.
- The central posterior nucleus relays impulses for somatic
sensations such as touch, pressure, vibration, itch, tickle,
temperature, pain, and proprioception from the face and
body to the cerebral cortex.
- The lateral geniculate nucleus relays visual impulses for
sight from the retina to the primary auditory area of the
cerebral cortex.
81
Explain what the intralaminar nuclei of the thalamus is.
Intralaminar nuclei lie within the internal medullary lamina and make connections with the reticular formation, cerebellum, basal nuclei, and wide areas of the cerebral cortex. They function in arousal and integration of sensory and motor information.
82
Explain what the midline nucleus is of the thalamus.
The midline nucleus forms a thin band adjacent to the third ventricle and has a presumed function in memory and olfaction.
83
Explain what the reticular nucleus of the thalamus is.
The reticular nucleus surround the lateral aspects of the thalamus, next to the internal capsule. This nucleus monitors, filters, and integrates activities of other thalamic nuclei.
84
Explain where the hypothalamus is located.
The hypothalamus is a small part of the diencephalon located in inferior to the thalamus.
85
What are the four major nuclei regions the hypothalamus is composed of.
- The mammillary region
- The tuberal region
- The supraoptic region
- The preoptic region
86
Explain what mammillary region of the hypothalamus is.
The mammillary region, adjacent to the midbrain, is the most posterior part of the hypothalamus. It includes the mammillary bodies and posterior hypothalamic nuclei. The mammillary bodies are tow small, rounded projections that serve as relay stations for reflexes related to the sense of smell.
87
Explain the tuberal region of the hypothalamus.
The tuberal region, the widest part of the hypothalamus, includes the dorsomedial region, ventromedial nucleus, and arcuate nucleus, plus the stalklike infundibulum, which connects the pituitary gland to the hypothalamus. the median eminence is a slightly raised region that encircles the infundibulum.
88
Explain the supraoptic region of the hypothalamus is.
The supraoptic region lies superior to the optic chiasm and contains the paraventricular nucleus, supraoptic nucleus, anterior hypothalamic nucleus, and suprachiasmatic nucleus. Axons from the paraventricular and supraoptic nuclei from the hypothalamohypophyseal tract, which extends through the infundibulum to the posterior love of the pituitary.
89
Explain what the preoptic region of the hypothalamus is.
The preoptic region anterior the the supraoptic regions is usually considred part of the hypothalamus because it participates with the hypothalamus in regulating certain autonomic activities. The preoptic region contains the medial and lateral preoptic nuclei.
90
Why is the hypothalamus importan?
The hypothalamus controls many body activities and is one of the major regulations of homeostasis. Sensory impulses related to both somatic and visceral senses arrive at the hypothalamus, as do impulses from receptors for vision, taste, and smell.
91
What are the 6 important functions of the hypothalamus.
- Control of the autonomic nervous system: The hypothalamus controls and integrates activities of the ANS, which regulates contraction of smooth muscles and cardiac muscles and the secretions of many glands.
- Production of hormones: The hypothalamus produces several hormones. The hypothalamic hormones known as releasing hormones and inhibiting hormones are released into capillary networks in the median eminence. The blood stream carries these hormones directly to the anterior lobe of the pituitary, where they stimulate or inhibiting secretion of anterior pituitary hormones. Second, axons extend from the paraventricular and supraoptic nuclei through the infundibulum into the posterior lobe of the pituitary. The cell bodies of these neurons make one or two hormones (oxytocin and antidiuretic hormones). Their axons transport the hormones to the posterior pituitary, where they are released.
- Regulation of emotional and behavioural patterns: together with the limbic system, and hypothalamus participates in extensions of rage, aggression, pain, and pleasure, and the behavioural patterns related to sexual arousal.
- Regulation of eating and drinking: The Hypothalamus regulates food intake. It contains a feeding centre, which promotes eating and a satiety centre, which causes a sensation of fullness and cessation of eating. The hypothalamus also contains a thirst centre. When certain cells in the hypothalamus are stimulated by rising somatic pressure of the extracellular fluid, they cause the sensation of thirst.
- Controls of body movements: The hypothalamus also functions as the bodys thermostat.
- Regulation of circadian rhythms: The suprachiasmatic nucleus of the hypothalamus serves as the bodys internal biological clock because it establishes circadian rhythms, patterns of biological activity that occurs in a circadian schedule.
92
Explain what the epithalamus is.
The epithalamus, a small region superior and posterior to the thalamus, consisting of the pineal gland and habanular nuclei.
93
Explain what the pineal gland is.
The pineal gland is about the size of a small pea and protrudes from the posterior midline of the third ventricle. The pineal gland is part of the endocrine system because it secretes the hormone melatonin. Melatonin helps regulate circadian rhythms.
94
Explain what the habenuclar nuclei is.
The habenuclar nuclei are involved in olfaction, especially emotional responses to odours.
95
Explain what the circumventricular organs are.
Parts of the diencephalon, called circumventricular organs because they lie in the wall of the third ventricle, can monitor chemical changes in the blood because they lack a blood brain barrier.
Functionally, these regions coordinate homeostatic activities of the endocrine system, and nervous systems. The circumventricular organs are also thought to be the sites of entry into the brain for HIV.
96
Explain what the cerebrum is.
The cerebrum is the 'seat of intelligence.' The cerebrum consists of an outer cerebral cortex, an internal region of cerebral white matter, and grey matter nuclei deep within the white matter.
97
Explain what the cerebral cortex is. Explain what the gyri is.
The cerebral cortex is a region of grey matter that forms the outer rim of the cerebrum. During embryonic stage, the grey matter of the cortex enlarges much faster than the deeper white matter. As a result, the cortical region rolls and folds on itself. The folds are called gyri or convolutions.
98
Differentiate between the fissures and the sulci of the cerebrum. Whats the most prominent fissure?
The deepest grooves between the folds of the cerebrum are known as fissures; the shallower grooves between folds are called sulci.
The most prominent fissure, the longitudinal fissure, separates the cerebrum into right and left halves called cerebral hemispheres.
99
Explain what the falx cerebi is.
Within the longitudinal fissure between the cerebral hemispheres is the falx cerebi.
100
What connects the cerebral callosum?
The cerebral hemisphere are connected internally by the corpus callosum, a broad band of white matter containing axons that extend between the hemisphere.
101
Explain what the central sulcus is.
- The central sulcus separates the frontal lobe from the
parietal lobe.
102
Explain what the precentral gyrus is.
A major gyrus, it is located immediately anterior of the central sulcus. It contains the primary motor area of the cerebral cortex.
103
Explain what the postcentral gyrus is.
Another major gyrus, it contains the primary somatosensory area of the cerebral cortex.
104
Explain what the lateral cerebral sulcus is.
It separates the frontal lobe from the temporal love.
105
Explain what the parieto-occipital sulcus is.
It separates the parietal lobe from the occipital lobe.
106
Explain what the insula of the cerebrum is.
A fifth part of the cerebrum, the insula, cannot be seen at the surface of the brain because it lies within the lateral cerebral sulcus, deep to the parietal, frontal, and temporal lobes.
107
Explain what the cerebral white matter is.
The cerebral white matter consists of primarily myelinated axons in three types of tracts:
- Association tracts
- Commissural tracts
- Projection tracts
108
Explain what the associated tract of the cerebral white matter is.
Contains axons that conduct nerve impulses between gyri in the same hemisphere.
109
Explain what the commissural tracts of the cerebral white matter is.
Contains axons that conduct nerve impulses from gyri in one cerebral hemisphere to corresponding gyri in the other cerebral hemisphere. Three important groups of commissural tracts are the corpus callosum, anterior commissure, and posterior commissure.
110
Explain what the projection tracts of the cerebral white matter is.
Contains axons that conduct nerve impulses from the cerebrum to lower parts of the CNS or form lower parts of the CNS to the cerebrum. An example is the internal capsule, a thick band of white matter that contains both ascending and descending axons.
111
Explain what the basal nuclei is.
Deep within each cerebral hemisphere are three nuclei that are collectively termed the basal nuclei.
Two of the basal nuclei lie side to side, just lateral to the thalamus. They are the globus pallidus, which is closer to the thalamus, and the putamen, which is closer to the cerebral cortex.
Together, they are referred to as the lentiform nucleus.
The third basal nuclei is the caudate nucleus, which has a large 'head' connected to a smaller 'tail' by along comma shaped 'body'.
Together the lentiform and caudate nuclei are known as the corpus stratum.
112
Explain what the calustrum is.
The claustrum is a thin sheet of grey matter situated lateral to the pulamen. It is considered by some to be a subdivision of the basal nuclei.
113
what are the major functions of the basal nuclei.
The basal nuclei receives input from the cerebral cortex and provide output to motor parts of the cortex via the medial and ventral groups nuclei of the thalamus.
A major function of the basal nuclei is to help regulate initiation and termination of movements. Activities of neurons in the putamen preceded or anticipates body movements. The globus pallious helps regulate the muscle tone required for specific body movements.
the basal nuclei also control subconscious contraction of skeletal muscle.
The basal nuclei also helps initiate and terminate some cognitive processes, attention, memory, and planning, and may act with the limbic system to regulate emotional behaviours.
114
Explain what the limbic system is.
Encircling the upper part of the brainstem and the corpus callosum is a ring of structures on their inner borders of the cerebrum and floor of the diencephalon that constitutes the limbic system.
The limbic system is sometimes called 'emotional brain' because it plays a primary role in a range of emotions. It is also involved in olfactory and memory. Damage to the limbic system causes memory impairment.
115
Explain what the main components of the limbic system is.
- The limbic lobe is a rim of cerebral cortex on the medial surface of each hemisphere. It include the cingulate gyrus, which lies above the corpus callosum, and the parahippocampal gyrus, which is in the temporal lobe below.
- The amygdala is composed of several groups of neurons located close to the tail of the caudate nucleus.
- The septal nuclei are located within the septal area formed by the regions under the corpus callosum and the paraterminal gyrus.
- The mammillary bodies of the hypothalamus are tow round masses close to the midline near the cerebral peduncles.
- Two nuclei of the thalamus, the anterior nucleus and the medial nucleus, participates in limbic circuits.
- The olfactory bulbs are flattened bodies of the olfactory pathways that rest on the cribiform plate.
- The fornix, stria terminals, stria medullaris, medial forebrain bundles, and mammillothalamic tract are linkers by bundles of interconnecting myelinated axons.
116
Explain what the hippocampus is.
The hippocampus is a portion of the perahippocampal gyrus that extends into the floor of the lateral ventricles.
117
Explain what the sensory areas of the cerebral cortex.
Sensory impulses arrive mainly in the posterior half of both cerebral hemispheres, in region behind the central sulci. In the cerebral cortex, primary sensory areas receive sensory information that has been relayed from peripheral sensory receptors through lower regions of the brain.
Sensory association areas often are adjacent to the primary areas. They usually receive input both form the primary areas integrate sensory experiences to generate meaningful patterns of recognition and awarness.
118
Explain what the primary somatosensory area is.
It is located directly posterior to the central sulcus of each cerebral hemisphere in the postcentral gyrus of each parietal lobe.
The primary somatosensory area receives nerve impulses for touch, pressure, vibration, itch, tickle, temperature, pain, and proprioception and is involved in the perception of these somatic sensations.
A 'map' of the entire body is present in the primary somatosensory area: each point within the area receives impulses fro ma specific part of the body. This distorted somatic sensory map of the body is known as the sensory homunculus.
The primary somatosensory area allows you to pinpoint where somatic sensations originates from.
119
Explain what the primary visual area is.
It is located at the posterior tip of the occipital lobe mainly on the medial surface, receives visual information and is involved in visual perception.
120
Explain what the primary auditory area is.
It is located in the superior part of the temporal love near the lateral cerebral sulcus, receives information for sound and is involved in auditory perception.
121
Explain what the primary gustatory area is.
It is located in the insula, receives impulses for taste and is involved in gustatory perception and taste discrimination.
122
Explain what the primary olfactory area.
It is located in the temporal lobe on the medial aspect, receives impulses for smell and is involved in olfactory perception.
123
Explain what the motor area of the cerebral cortex.
Motor output from the cerebral cortex flows mainly from the anterior part of each hemisphere.
124
Explain what the primary motor area of the motor area is.
It is located in the percentral gyrus of the frontal lobe. A 'map' of the entire body is present in the primary motor area. Each region within the area controls voluntary contractions of specific muscles or groups of muscles. Different muscles are represented unequally in the primary motor area. This distorted muscle map of the body is called the motor homunculus.
125
Explain what the brocas speech area of the motor area.
It is located in the frontal lobe close to the lateral cerebral sulcus. Speaking and understanding languages are complex activities that involve several sensory, association, and motor areas of the cortex. In about 97% of the population, these language areas are localized in the left frontal lobe in most people.
126
Explain what the association areas of the cerebral cortex.
Association areas are connected with one another by association tracts.
127
Explain the somatosensory association area of the association areas of the cerebral cortex.
It is just posterior to and receives input from the primary somatosensory area, as well as form the thalamus and other parts of the brain. This area permits you to determine the exact shape and texture of an object by feeling it, to determine the orientation of one object with respect to another as they are felt, and to sense the relationship of one body part to another.
Another role of the somatosensory association area is the storage of memories of past somatic experiences, enabling you to compare current sensations with previous experiences.
128
Explain what the visual association area is.
It is located in the occipital lobe, it receives sensory impulses from the primary visual area and the thalamus. It relates present and past visual experiences and is essential for recognizing and evaluating what is seen.
129
Explain what the facial recognition area is.
In the inferior temporal lobe, it receives nerve impulses from the visual association area. This area stores information about faces and it allows you to recognize people by their faces. the facial recognition area in the right hemisphere is usually more dominant than the corresponding region in the left hemisphere.
130
Explain what the auditory association area is.
It is located inferior and posterior to the primary auditory area in the temporal cortex, allows you to recognize a particular sounds as speech, music, or noise.
131
Explain what the orbitofrontal cortex is.
Along the lateral part of the frontal lobe, receives sensory impulses form the primary olfactory area. This area allows you to identify odours and to discriminate among different odours. during olfactory processing, the orbito frontal cortex of the right hemisphere exhibits greater activity than the corresponding region in the left hemisphere.
132
Explain what the Wernicke's area is.
Posterior language area, a broad region in the left temporal and parietal lobes, interprets the meaning of speech by recognizing spoken words. it is active as you translate words into thoughts.
133
Explain what the common integrative area.
It is bordered by somatosensory, visual, and auditory association area. It receives nerve impulses from these areas and form the primary gustatory area, the primary ofactory area, the thalamus, and parts of the brainstem.
This area integrates sensory interpretation from the association areas and impulses from other areas, allowing the formation of thought based on a variety of sensory inputs. It then transmits signals to other parts of the brain for the appropriate response to the sensory signals it has interpreted.
134
Explain what the prefrontal cortex is. (frontal association area)
It is an extensive area in the anterior part of the frontal lobe that is well developed in primates, especially in humans. The prefrontal cortex is concerned with the make up of a persons personality, intellect, complex learning abilities, recall of information, initiative, judgement, foresights, reasoning, conscience, intuition, mood, planning the future, and development of abstract idea.
A person with bilateral damage to the prefrontal cortices typically becomes a rude, inconsiderate, incapable of accepting advice, moody, inattentive, less creative, unable to plan for the future, and incapable of anticipating the consequences of rash and reckless words or behaviour.
135
Explain what the premotor area is.
It is a motor association area that is immediately anterior to the primary motor area. The premotor area deals with learned motor activities of a complex and sequential nature. The premotor area also serves as a memory bank for such movements.
136
Explain what the frontal eye field area is.
It is in the frontal cortex is sometimes included in the premotor area. It controls voluntary scanning of movements of the eyes.
137
Explain what the hemispheric lateralization is.
Although the brain is almost symmetrical on its right and left sides, subtle anatomical differences between the twi hemispheres exist. Physiological differences also exist, although the two hemispheres share performances of many functions each hemisphere also specializes in performance of many functions, each hemisphere also specializes in performing certain unique functions. This functional asymmetry is termed hemisphere lateralization.
Lateralization seems less pronounced in females than in males, both of language and are visual and spatial skills.
138
Explain what brain waves are.
At any instant, brain neurons are generating millions of nerve impulses (action potential). Taken together, these electrical signals are called brain waves.
139
Explain what an electroencephalogram is.
Brain waves generated by neurons close to the brain surface, mainly neurons in the cerebral cortex, can be detected by sensors called electrodes. A record of such waves is called an electroencephalogram (EEG).
140
Explain the four types of brain waves.
- Alpha waves: they are present in the EEGs of nearly all
normal individuals when they are awake and resting with
their eyes closed. These waves disappear entirely during
sleep.
- Beta waves: They generally appear when the nervous
system is active -- that is during periods of sensory input
and mental activity.
- Theta waves: These waves normally occur in children and
adults experiencing emotion stress.
- Delta waves: They occur during sleep in adults, but they
are normally awake in infants. when produced by an
awake adult, they indicate brain damage.
141
Why is doing an EEG important?
EEGs are useful both in studying normal brain functions, such as changes that occur during sleep and in diagnosing a variety of brain disorders. The EEG is also utilized to determine if 'life' is present, to establish or confirm that brain death has occurred.
142
Explain what cranial nerves are.
They are named cranial nerves because they pass through various foramina in the bones of the cranium and arise from the brain inside the cranial cavity. Each cranial nerve has both a number, designated by a roman numeral and a name.
143
How many cranial nerves do we have.
12 pairs
144
Explain what special senosry axons are.
Three cranial nerves (I, II, VIII) carry axons of sensory neurons and thus are called special sneosry axons. These nerves are unique to the head and are associated with the special senses of smelling, seeing, and hearing. The cell bodies of most sensory neurons are located in the ganglia outside the brain.
145
Explain the five cranial nerves classified as motor nerves.
Five cranial nerves (III, IV, VI, XI, XII) are classified as motor nerves because they contain only axons of motor neurons as they leave the brainstem. The cell bodies of motor neurons lie in nuclei within the brain.
146
Explain the two motor axons that innervate skeletal muscles.
- Brachial motor axons innervate skeletal muscles that
develop from the pharyngeal (branchial) arches. These
neurons leave the brain through the mixed cranial
nerves and the accessory nerves.
- Somatic motor axons innervate skeletal muscles that develop from head somites (eye and tongue muscles). These neurons exit the brain through five motor cranial nerves (III, IV, VI, XI, XII). Motor axons that innervate smooth muscles, cardiac muscles, and glands are called autonomic motor axons and are part of the parasymptathetic division.
147
Explain what mixed nerves are.
Four nerves (V, VII, IX, X) are termed mixed nerves, they contain axons both of sensory neurons entering the brain stem and motor neurons leaving the brainstem.
148
Explain what the olfactory (I) nerve is.
It is entirely sensory; it contains axons that conduct nerve impulses for olfaction, the sense of smell. The olfactory epithelium is located on the inferior surface of the cribriform place and superior conchae. The olfactory receptors within the olfactory epithelium are bipolar neurons. Each has a single odour sensitive knob shaped dendrite projecting from one side of the cell body and an unmyelinated axon extending from the other side.
149
Explain what the olfactory bulbs are.
Olfactory nerves end in the brain in paired masses of grey matter called the olfactory bulbs, two extensions of the brain that rest on the cribriform plate. Within the olfactory bulb, the axon terminals of olfactory receptors form synapses with the dendrites and cell bodies of the next neurons in the olfactory pathways.
150
What are olfactory tracts.
The axons of the olfactory nerve make up the olfactory tract, which extends posteriorly from the olfactory bulbs. Axons in the olfactory tracts and in the primary olfactory area in the temporal love of the cerebral cortex.
151
Explain what the optic (II) nerve.
It is entirely sensory and is technically a tract of the brain and not a nerve; it contains axons that conduct nerve impulses for vision. In the retina, rods and cones initiate visual signals and relay them to bipolar cells, which transmit the signals to ganglion cells. Axons of all ganglion cells in the retina of each eye join to form an optic nerve, which passes through the optic foramen.
152
Explain what the optic chiasm is.
About 10mm posterior to the eyeball, the two optic nerves merge to form the optic chaism. Within the chiasm, axons from the medial half of each eye cross to the opposite side; axons from the lateral half remain on the same side.
153
Explain what optics tracts are.
Posterior to the chiasm, the regrouped axons, some from each eye form the optic tract. Most axons in the optic tracts ends in the lateral geniculate nucleus of the thalamus. There they synapse with neurons whose axons extend to the primary visual area in the occipital lobe of the cerebral cortex.
154
Explain what the occulomotor (III), trochlear (IV), and abducens (VI) nerves are.
The occulomotor, trochlear, and abducens nerves are the cranial nerves that control the muscles that move the eyeballs. They are all motor nerves that contain only motor axons as they exit the brainstem. Sensory axons from the extrinsic eyeball muscles begin their course toward the brain in each of these nerves, but eventually these sensory axons leave the nerves to join the ophthalmic branch of the trigeminal nerves. The sensory axons do not return to the brain in the occulomotor, trochlear, or abducens nerves. The cell bodies of the unipolar sensory neurons reside in the mesencephalic nucleus and they enter the midbrain via the trigeminal (V) nerves.
155
Explain what the occulomotor (III) nerve is.
It has its motor nucleus in the anterior part of the midbrain. Axons in the superior branch innervate the superior rectus (an extrinsic eyebal muscle) and the levator palpabrae superioris (the muscle of the upper eyelid). Somatic motor neurons controls movements of the eyeballs and upper eyelids.
The inferior branch of the occulomotor nerve also supplies parasympathetic motor axons to intrinsic eyeball muscles, which consists of smooth muscle. They include the ciliary muscles of the eyeball and the circular muscles of the iris.
156
Explain what the ciliary ganglion is.
Parasympathetic impulses propagate fro ma nucleus in the midbrain to the ciliary ganglion, a synaptic relay centre for the two motor neurons of the parasympathetic nervous system.
From the ciliary ganglion, parasympathetic motor axons extend to the ciliary muscles, which adjusts the lens for near vision (accommodation).
Other parasympathetic motor axons stimulate the circular muscles of the iris to contract when bright light stimulates the eye, causing a decrease in the size of the pupil (constriction).
157
Explain what the trochlear (IV) nerves.
It is the smallest of the 12 cranial nerves and is only one that arises from the posterior aspect of the brainstem. The somatic motor neurons originates in a nucleus in the midbrain, and axons from the nucleus cross to the opposite side as they exit the brain on its posterior aspects.
The nerve then wraps around the pons and exits through the superior orbital fissure into the orbits. These somatic motor axons innervate the superior oblique muscles of the eyeballs.
158
Explain what the abducens (VI) nerves are.
Neurons of the abducens nerve originate form a nucleus in the pons. Somatic motor axons extend from the nucleus to the lateral rectus muscle of the eyeball, through the superior orbital fissure of the orbit. The abducens nerve is so named because nerve impulses causes abduction of the eyeball.
159
Explain what the Trigeminal (V) nerve is.
It is a mixed cranial nerves and the longest of the cranial nerves. It emerges from the two roots on the anterolateral surface of the pons.
160
Explain what a trigeminal (semilunar) ganglion is.
The largest sensory root has a swelling called the trigeminal ganglion, which is located in a fossa on the inner surface of the petrous portion of the temporal bone.
The ganglion contains cell bodies of most of the primary sensory neuron. Neurons of the smaller motor root originate in a nucleus in the pons.
161
Explain the three branches of the trigeminal nerve.
- Ophthalmic nerve: The smallest branch, passes into the
orbit via the superior orbit fissure.
- Maxillary nerve: Is intermediate in size between the
ophthalmic and mandibular nerves and passes through
the foramen rotundum.
- Mandibular nerve: The largest branch, passes through
the foramen ovale.
162
What does the sensory axons in the trigeminal nerve carry?
Sensory axons in the trgieminal nerve carry nerve impulses for touch, pain, and thermal sensations. The ophthalmic nerve contains sensory axons from the skin over the upper eyelid, cornea, lacrimal gland, upper part of the nasal cavity, side of the nose, forehead, and anterior half of the scalp.
The maxillary nerve includes sneosry axons from the mucosa of the nose, palate, part of the pharynx, upper teeth, upper lip, and lower eyelids.
163
Where does the sensory axon of the trigeminal nerve enter?
The sensory axons from the three branches enter the trigeminal ganglion where their cell bodies are located, and terminate in nuclei in the pons.
164
Explain what the branchial motor neuron is.
Brachial motor neurons of the trigeminal nerves are part of the mandibular nerve and supply muscles of mastication. These motor neurons mainly control chewing movement.
165
Explain what the facial (VII) nerve is.
It is a mixed cranial nerve. Its sensory axon extend from the taste buds of the anterior two thirds of the tongue, which enter the temporal bone to join the facial nerve.
The facial nerve innervates more named muscles than any other nerve in the body.
166
Explain what the geniculate ganglion is.
The sensory axons pass to the geniculate ganglion, a cluster of cell bodies of sensory neurons of the facial nerve within the temporal bone, and ends in the pons. From the pons, axons extend to the thalamus, and then to the gustatory across of the cerebral cortex. The sensory portion of the facial nerve also contain axons from the skin in the ear canal that relay touch, pain, and thermal sensations.
167
Explain where the brachial motor neurons of the facial nerves arise from.
Axons of the branchial motor neurons arise from a nucleus in the pons and exit the stylomastoid foramen to innervate middle ear, facial, scalp, and neck muscles.
168
What are the two ganglia that runs through the parasympathetic motor neuron the facial nerve?
- Pterygopaatine gangion
- Submandibular ganglion
169
Explain what the vestibulocochlear (VIII) nerve is.
It was formerly known as thee acoustic or auditory nerve. It is a sensory cranial nerve and has two branches, the vestibular branch and the cochlear branch.
170
Differentiate between the vestibular branch and the cochlear branch.
The vestibular branch carries impulses for equilibrium and the cochlear branch carries impulses for hear.
171
Explain what the vestibular ganglia is.
Sensory axons in the vestibular branch extend fro mthe semicircular canals, the saccule, and the utricle of the inner ear to the vestibular ganglia, where the cell bodies of the neurons are located, and end in vestibular nuclei in the pons and cerebellum.
172
Where does the sensory axon of the vestibulocochlear nerve enter?
Some sensory axons enter the cerebellum via the inferior cerebellar peduncles.
173
Where does the sensory axons of the vestibulocochlear nerve arise from?
Sensory axons in the cochlear branch arise in the spinal organ in the cochlear of the internal ear.
174
Explain what the spiral ganglion are.
The cell bodies of cochlear branch sensory neurons are located in the spinal ganglion of the cochlea. From there, axons extend to nuclei in the medulla oblongata and end in the thalamus.
175
Explain what the glossopharyngeal (IX) nerve is.
It is a mixed cranial nerve. Sensory axons of the glossopharyngeal nerve arise from:
- Taste buds on the posterior one third of the tongue
- Proprioceptors from some swallowing muscles supplied
by the motor portion
- Baroreceptors (pressure monitoring receptors) in the
carotid sinus that monitor blood pressure.
- Chemoreceptors (receptors that monitor blood levels of
oxygen and carbon dioxide) in the carotid bodies near
the carotid arteries and aortic bodies near the arch of the
aorta
- The external ear to convey touch, pain, and thermal
sensations
176
Explain what the superior and inferior ganglia is.
The cell bodies of the glossopharyngeal nerves sensory neurons are located in the superior and inferior ganglia.
From the ganglia, sensory axons pass through the jugular foramen and end in the medulla.
177
Where does the motor neurons in the glossopharyngeal nerve arise and exit from?
Axons of the motor neurons arise in nuclei of the medulla and exit the skull through the jugular foramen.
Branchial motor neuron innervate the stylopharyngeus muscle, which assists in swallowing, and axons of parasympathetic motor neurons stimulate the parotid gland to secrete saliva.
178
Explain what the otic ganglion is.
The post ganglionic cell bodies of parasympathetic motor neurons of the glossopharyngeal nerve are located in the otic ganglion.
179
Explain what the vagus (X) nerve is.
It is a mixed cranial nerve that is distributed form the head and neck into the thorax and abdomen. In the neck, it lies medial and posterior to the internal jugular vein and common carotid artery.
180
Where dose the sensory axons in the vagus nerve arise from?
It arises from the skin of the external ear for touch, pain, and thermal sensations.
181
Where does the sensory neurons on the vagus nerve come from?
The majority of sensory neurons come from visceral sensory receptors in most organs of the thoracic and abdominal cavities that convey sensations from these abdominal cavities that convey sensations from these organs.
The sensory neurons have cell bodies in the superior and inferior ganglia and then pass through the jugular foramen to end in the medulla and pons.
182
Where does the axons of parasympathetic motor neurons in the vagus nerve originate form?
It originates in nuclei of the medulla and supply the lungs, heart, glands of the GI tracts and smooth muscles of the respiratory passageway, esophagus, stomach, gallbladder, small intestines and most of the large intestines.
183
Explain what the accessory (XI) nerve is.
It is a branchial motor cranial nerve. Its motor axon arise in the anterior grey horn of the first five segments of the cervical portion of the spinal cord. The axons from the segments exit the spinal cord laterally and come together, ascend through the foramen magnum, and then exit through the jugular foramen along with the vagus and glossopharyngeal nerve.
The accessory nerve conveys motor impulses to the sternoclediomastoid and trapezius muscles to coordinate head movements.
From the cervical plexus they enter the spinal cord via the posterior roots of cervical spiral nerves, their cell bodies are located in the posterior root ganglia of those nerves. In the spinal cord the axons ascend to nuclei in the medulla oblongata.
184
Explain what the hypoglossal (XII) nerve.
It is a motor cranial nerve. The somatic motor axons originate in a nucleus in the medulla oblongata, exit the medulla on its anterior surface, and pass through the hypoglossal canal to supply the muscles of the tongue.
These axons conduct nerve impulses for speech and swallowing. The sensory axons do not return to the brain in the hypoglossal nerve. Instead, sensory axons that originate from proprioceptors in the tongue muscles begin their course towards the brain in the hypoglossal nerve but leave the nerve to joint cervical spine nerves and end in the medulla oblongata, again entering the CNS via posterior roots of cervical spinal nerves.
185
What are the two ways motor pathways that control movements?
Pyramidal tract and extrapyramidal tracts
186
Pyramidal tract
Corticospinal pathway. Controls learned motor actions
187
How does the CNs develop in utero?
As an embryonic neural tube. Neural folds fuse along the dorsal midline to form a hollow tube
188
Ancencephaly
Failure to fuse at the rostral end of the neural tube. Brain and skull do not develop infant does not survive
189
Spina bifida
Failure of vertebral arches to fuse over the caudal end of the spine and cord
190
Hydrocephalus
Accumulation of CSF in the brain when the rate of CSF secretion is greater than the rate of CSF reabsorption
191
Nociceptors
Pain receptors that responds to noxious stimuli. Protect body by creating appropriate response to injury. Found in spinal and cranial nerves.
192
Two types of cutaneous nociceptors
- A delta fibers (fast pain)
- C fibers (Slow pain)
193
Veins
Carries oxygenated blood
194
Arteries
Carries deoxygenated blood
195
Valve between right and atrium and right ventricle
Tricuspid valve
196
Valve between left atrium and left ventricle
Bicuspid valve or mitral valve
197
When does the tricuspid valve of the heart open?
When the pressure in the right atrium is higher than the pressure in the right ventricle
198
When does the tricuspid valve of the heart close?
When the pressure in the right atrium is less than the pressure in the right ventricle
199
Structures of vein
Thinner walls and thinner layers of muscle and elastic fibers. One way valve to prevent blood from flowing in the wrong direction
200
Structure of artery
Thick walls and thick layers of muscle and elastic fibers
201
SA node
Natural pacemaker.
202
Frank starling
