Nervous System: Brain and Cranial Nerves

Question 1

What are the 4 main regions of the brain?

Answer 1

• Cerebrum, diencephalon, brainstem and cerebellum

Question 2

What is gyri and sulci? (brain)

Answer 2

• Gyri: folds in the outer surface of the brain

- Sulci: shallow depressions between folds

Question 3

What is gray matter?

Answer 3

• Houses motor neurons and interneuron cell bodies, dendrites, terminal arborizations and unmyelinated axons

Question 4

What is white matter?

Answer 4

• Derives its colour from the myelin on the myelinated axons
• Association tracts connect different regions of the cerebral cortex within the same hemisphere (made of central white matter)
• Commissural tracts extend between cerebral hemispheres through axonal bridges called comminsures (made of central white matter)
• Projection tracts link the cerebral cortex into inferior brain regions and the spinal cord (made of central white matter)

Question 5

White and gray matter in the brain?

Answer 5

• Cerebral cortex: the external layer of gray matter that covers the surface of most of the adult brain
• White matter lies deep to the gray matter of the cortex
• Within the inner masses of white matter, there are discrete, internal clusters of. gray matter called cerebral nuclei (irregularly shaped clusters of neuron cell bodies)

Question 6

What voluntary control centers are in the CNS?

Answer 6

• Cerebral cortex, cerebral nuclei, cerebellum, brainstem, spinal cord

Question 7

What is the cerebrum?

Answer 7

• Location of conscious thought processes and the origin of all complex intellectual functions
• Identified as the 2 large hemispheres on the superior aspect of the brain
• Allows you to read and comprehend words, ect.
• Formed from the gray matter of the telencephalon (cerebral cortex)
• Composed into 2 halves called left and right cerebral hemispheres
• Each hemisphere is separated by a deep longitudinal fissure that extends along the midsagittal plane

Question 8

What is the corpus callosum?

Answer 8

• Largest white matter tract that connects the cerebral hemispheres
• Provides the main communication links between the hemispheres

Question 9

What are the lobes of the cerebrum?

Answer 9

• Each cerebral hemisphere is divided into 5 anatomically and functionally distinct lobes
• Frontal, parietal, temporal, occipital and insula

Question 10

What is the frontal lobe?

Answer 10

• Lies deep to the frontal bone and forms the anterior part of the cerebral hemisphere
• Ends posteriorly at a deep groove called the central sulcus that marks the boundary with the parietal lobe
• The inferior border of the frontal lobe is marked by the lateral sulcus, a deep groove that separates the frontal and parietal lobes from the temporal lobe
• Primarily concerned with voluntary motor functions, concentration, verbal communication, decision making, planning and personality

Question 11

What is the precentral gyrus? (frontal lobe)

Answer 11

• A mass of nervous tissue immediately anterior to the central sulcus

Question 12

What is the parietal lobe?

Answer 12

• Lies internal to the parietal bone and forms the superoposterior part of each cerebral hemisphere
• It terminates anteriorly at the central sulcus and posteriorly at a relatively indistinct parieto-occipital sulcus and laterally at the lateral sulcus
• Involved with general sensory functions such as evaluating shape and texture of objects being touched

Question 13

What is the postcentral gyrus? (parietal)

Answer 13

• Mass of nervous tissue immediately posterior to the central sulcus

Question 14

What is the temporal lobe?

Answer 14

• Lies inferior to the lateral sulcus and underlies the temporal bone
• Involved with hearing and smell

Question 15

What is the occipital lobe?

Answer 15

• Forms the posterior region of each hemisphere and immediately underlies the occipital bone
• Responsible for processing incoming visual information and storing visual memories

Question 16

What is the insula lobe?

Answer 16

• A small lobe deep to the lateral sulcus
• It can be viewed by laterally reflecting the temporal lobe
• It’s lack of accessibility has prevented aggressive studies of its function
• Supposedly involved in interoceptive awareness, emotional response, empathy and the interpretation of taste

Question 17

What is the cerebral nuclei?

Answer 17

• Control maintenance of posture and equilibrium
• Control learned movements such as driving a car
• Control sensory integration for balance and rhythmic activities
• Caudate nucleus (coordinate walking), amygdaloid body (expression of emotions and behaviour activities), lentiform nucleus (made of putamen and globus pallidus which control muscular movements at a subconscious level and excite an anterior group of nuclei), claustrum (consciousness and integration of info from multiple senses)

Question 18

What are the functional motor areas of the cerebrum?

Answer 18

• Primary motor cortex (voluntary skeletal activity)
• Motor homunculus (on the precentral gyrus and is the primary motor cortex innervation to various body parts
• Motor speech area (within the inferolateral portion of left frontal lobe for controlling muscular movements necessary for speaking)
• Frontal eye field (on superior surface of the middle frontal gyrus to control and regulate eye movements)

Question 19

What are the functional sensory areas of the cerebrum?

Answer 19

• Primary somatosensory cortex (housed in post-central gyrus of the parietal lobes where they recieve general somatic sensory info like touch)
• Sensory homunculus (similar to motor homunculus)
• Primary visual cortex (in occipital lobe and recieves and processes visual information)
• Primary auditory cortex (in temporal lobe, recieves and processes auditory info)
• Primary gustatory cortex (in the insula lobe and involved in processing taste info)
• Primary olfactory cortex (located in the temporal lobe for conscious awareness of smells)

Question 20

What are the functional association areas of the cerebrum?

Answer 20

• The primary motor and sensory cortical regions are connected to adjacent association areas that either process and interpret incoming data or coordinate a motor response
• Premotor cortex, somatosensory association area, auditory association area, visual association area and wernicke area (recognizing or comprehending verbal or written language)

Question 21

What are the functional high-order processing centers of the cerebrum?

Answer 21

• These centers process incoming info from several different association areas and ultimately direct either extremely complex motor activity or complicated analytical functions in response
• Both hemispheres house high-order processing centers involving speech, cognition, understanding spatial relationships and general interpretation

Question 22

What is the diencephalon?

Answer 22

• A part of the prosencephalon sandwiched between the inferior regions of the cerebral hemispheres
• Referred to as the “in-between brain)
• Includes the epithalamus, thalamus and hypothalamus
• Provides the relay and switching centers for some sensory and motor pathways and for control of visceral activities

Question 23

What is the epithalamus?

Answer 23

• Partially forms the posterior roof of the diencephalon and covers the 3rd ventricle
• The posterior portion of the epithalamus houses the pineal gland and the habenular nuclei
• Pineal gland: endocrine gland that secretes melatonin that regulates day and night cycles of the body (circadian rhythm)
• Habenular nuclei: helps relay signals from the limbic system to the midbrain and are involved in visceral and emotional responses to odors

Question 24

What is the thalamus?

Answer 24

• Refers to pair oval masses of gray matter that lie on each side of the 3rd ventricle
• Forms the superolateral walls of the 3rd ventricle
• Located between the anterior commissure and the pineal gland
• interthalamic adhesion: is a midline mass of gray matter that connects the right and left thalamic bodies
• Each part of the thalamus is a grey matter mass composed of about a dozen major thalamic nuclei (axons of this nuclei project to specific regions of the cerebral cortex)
• Sensory impulses from all the conscious senses except olfaction converge on the thalamus and synapse in at least one of its nuclei
• Is the principal and final relay point for sensory info that will be processed and projected to the primary somatosensory cortex
• Acts as an information filter (takes out sounds and light in a busy room when your trying to study)

Question 25

What is the hypothalamus?

Answer 25

• The anteroinferior region of the diencephalon
• A thin, stalklike infundibulum extends inferiorly from the hypothalamus to attach to the pituitary gland
• Functions: master control of the autonomic nervous system, master control of the endocrine system, regulation of body temperature, control of emotional behaviour, control of food intake, control of water intake, regulation of sleep-wake rhythms

Question 26

What is the brainstem?

Answer 26

• Connects the prosencephalon and cerebellum to the spinal cord
• Made up of the superiorly placed midbrain, the pons and the inferiorly placed medulla oblongata
• It’s a bidirectional passageway for all tracts extending between the cerebrum and the spinal cord
• Contains many autonomic centers and reflex centers required for our survival
• Also houses nuclei of many cranial nerves

Question 27

What is the midbrain? (brainstem)

Answer 27

• The superior portion of the brainstem
• Extending through it is the cerebral aqueduct connecting the 3rd and 4th ventricles
• Surrounded by a region of periaqueductal gray matter

Question 28

What is the pons? (brainstem)

Answer 28

• A bulging region on the anterior part of the brainstem that forms from part of the metencephalon
• Housed within the pons are sensory and motor tracts that connect to the brain and spinal cord

Question 29

What is the medulla oblongata? (brainstem)

Answer 29

• Formed from the myelencephalon
• Most inferior part of the brainstem and is continuous with the spinal cord inferiorly
• Autonomic centers: cardiac, vasomotor, medullary respiratory and coughing/sneezing

Question 30

What is the cerebellum?

Answer 30

• The second largest part of the brain and it develops the metencephalon
• Has a complex, highly convoluted surface covered by a layer of cerebellar cortex
• Composed of left and right cerebellar hemispheres (each consist of 2 lobes that are separated by a primary fissure)
• The vermis separates the left and right hemispheres
• Flocculonodular lobes lie anterior and inferior to each hemisphere
• 3 layers: outer gray matter from cerebral cortex, internal white matter region and deepest gray matter composed of cerebellar nuclei
• Coordinates the fine tuned skeletal muscle movements and ensures that skeletal muscle contraction follows the correct pattern leading to smooth, coordinated movements
• Stores memories of previously learned movement patterns
• Adjusts skeletal muscle activity to maintain equilibrium and posture

Question 31

What are cranial nerves?

Answer 31

• Part of the peripheral nervous system and originate on the inferior surface of the brain
• 12 pairs of cranial nerves
• Numbered according to their position, beginning with the most anteriorly placed nerve and using roman numerals
• Olfactory (CN I), optic (CN II), oculomotor (CN III), trochlear (CN IV), trigeminal (CN V), abducens (CN VI), facial (CN VII), vestibulocochlear (CN VIII), glossopharyngeal (CN IX), vagus (CN X), accessory (CN XI), and hypoglossal (CN XII)
• Each is composed of many axons, some only motor, some only sensory and some only cranial, and some a mix