Chapter 13- Nervous System: The Brain & Cranial Nerves
What are the differences between the right & left cerebral hemispheres with respect to their general functions?
Both receive sensory information from & project motor commands to, the opposite side of the body The left hemisphere functions in logic, mathematics, & language--the Categorical Hemisphere The right functions in art & emotion, spatial awareness & creativity--the Representative Hemisphere
Describe the location & actions of the different parts of the limbic system.
Cingulate Gyrus: internal mass of cerebral cortex, adjacent to longitudinal fissure & superior to corpus callosum; receives input from other components Parahippocampal Gyrus: Inferior to hippocampus within temporal lobe; function associated with the hippocampus Hippocampus: within temporal lobe, connects to the diencephalon via the fornix; essential in storing memories & forming long-term memories Amygdaloid Body: connects to the hippocampus; involved in several aspects of emotion, especially fear, also helps store & code memories based on how one emotionally perceives them Olfactory bulbs, tracts & cortex: within temporal lobe; involved in relating odors to particular memories & emotions
What is the function of the Hypoglossal Nerve (CN XII)?
Constricts intrinsic & extrinsic tongue muscles for tongue movement
What is the function of the Trochlear Nerve (CN IV)?
Contracts 1/6 extrinsic eye muscles to move the eye inferiorly & laterally
What is the function of the Oculomotor Nerve (CN III)?
Contracts 4/6 extrinsic eye muscles to move the eye
What is the function of the Abducens Nerve (CN VI)?
Contracts lateral rectus for eye abduction (lateral movement)
Describe in detail the functions associated with the cerebellum.
Coordinates & fine-tunes skeletal muscle movements that have already been initiated by the cerebrum, does this to ensure that skeletal muscle contractions follow the correct pattern for smooth, coordinated movement; adjusts skeletal muscle activity to maintain equilibrium & posture; receives proprioceptive information from the muscle & joints to help regulate body position; also involved in storing memories of movement patterns
What is the function of the Accessory Nerve (CN XI)?
Cranial root travels with CN X to assist in innervation of pharynx; spinal root contracts trapezius & sternocleidomastoid
Define Motor Homunculus.
Diagrams distribution of the primary motor cortex innervation in the body Proportions of diagram reflect how much area of the cortex is dedicated to motor activity within each area of the body
Locate & list the functions of the Somatosensory Association Area.
Found posterior to the somatosensory cortex within the parietal lobe Integrates sensory information & interprets sensations
Locate & list the functions of the Auditory Association Area.
Found posteroinferior to the auditory cortex within the temporal lobe Integrates & interprets the characteristics of sound & compares them to memories of sounds heard in the past
Locate & list the functions of the Prefrontal Cortex.
Found within the anterior portion of the frontal lobe Associated with many higher intellectual functions like complex thought, judgement, expressing personality, planning future behavior, & decision making Retrieves & coordinates information from multiple areas
Locate & list the functions of the Wernicke Area.
Found within the temporal lobe of the left hemisphere Involved in recognizing, understanding, & comprehending spoken/written language
Describe in detail the components of the cerebrum & their function.
Frontal lobe: forms anterior portion of cerebral hemisphere; ends posteriorly at the central sulcus & inferiorly at the lateral sulcus; location of the precentral gyrus; primarily concerned with voluntary motor functions, concentration, verbal communication, decision making, planning, & personality. Parietal lobe: forms the superoposterior part of the cerebral hemispheres; ends anteriorly at the central sulcus, posteriorly at the parieto-occipital sulcus, & laterally at the lateral sulcus; location of the postcentral gyrus; primarily involved with general sensory input from both the skin & proprioceptors. Temporal lobe: internal to the temporal bone & inferior to the lateral sulcus; primarily involved in hearing & smell. Occipital lobe: forms the posterior region of the cerebral hemispheres; primarily involved in processing & storing visual information. Insula: found deep to the lateral sulcus, only visible when the temporal lobe is pushed aside; primarily believed to be involved in memory & processing taste information
What is the function of the Glossopharyngeal Nerve (CN IX)?
General sensation & taste from posterior 1/3 of tongue; general sensation of pharynx; innervates muscles for swallowing
Describe in detail the functional differences of gray matter & white matter of the CNS.
Gray Matter: derives its color from cell bodies & dendrites of neurons that compose it; often designates as a "cortex," usually indicating superficial areas, or "nucleus/center," indicating deep areas; the general function of gray matter is to serve as an integrating & processing area. White Matter: derives its color from the bundles of myelinated axons that compose it; these areas are called "tracts" and are located on or close to the surface or deep; the general function of white matter is to relay nerve signals, it provides the means for information to be transmitted between different regions of the brain & spinal cord & between the brain & the body.
What are the functions of the Temporal Lobe?
Hearing & smell
Locate & list the functions of the Primary Gustatory Cortex.
Located within the insula Receives, processes, & stores taste information
What are the functions of the Insula?
Memory & taste
How does the substantia nigra relate to Parkinson's Disease?
Parkinson's is a disease that involves the degeneration of dopamine producing cells of the substantia nigra; it is a slow-progressing neurologic condition that affects muscle movement & balance; its caused by deficiency of dopamine, results from decrease dopamine production of degenerating neurons in the substantia nigra; the dopamine deficiency prevents the brain cells of the substantia nigra from inhibiting cerebral nuclei
Identify the respiratory center located in the pons
Pontine Respiratory Center regulates the skeletal muscles of breathing Primary function is to regulate a smooth transition between breathing in & out
What are the important regions of the frontal lobe?
Prefrontal cortex Precentral gyrus Primary Motor Cortex Motor Speech Area (Broca Area) Frontal Eye Field Ends posteriorly at the central sulcus & inferiorly at the lateral sulcus
What are the important regions within the temporal lobe?
Primary Auditory Cortex Primary Olfactory Cortex Wernicke Area
What are the important regions within the insula?
Primary Gustatory Cortex
What are the important regions within the occipital lobe?
Primary Visual Cortex
Compare & contrast short-term & long-term memories, and describe the parts of the brain involved with each.
Short-term memory: generally characterized by limited capacity & brief duration (less than or equal to 1 min) Long-term memory: may exist for limitless periods of time; needs to be retrieved occasionally or it can be lost Complex information is organized into STM before being stored as LTM (Process called encoding) LTM are stored in association areas within the cerebral lobes, depend on what type of information Hippocampus is involved with forming STM
What is the function of the Olfactory Nerve (CN I)?
Smell
Locate & list the functions of the Visual Association Area.
Surrounds the primary visual cortex within the occipital lobe Integrates & interprets all incoming visual information by analyzing color, movement, & form
Name the 2 speech areas, their location in the brain, & explain in detail how they function.
The 2 speech areas within the brain are known as the Broca area & the Wernicke area; the Broca area is the motor speech area within the inferolateral portion of the left frontal lobe, it is responsible for controlling the muscular movements involved in vocalization; the Wernicke area is typically located within the temporal lobe of the left hemisphere, it is responsible for recognizing, understanding, & comprehending spoken or written language; both areas work together for fluent communication to occur; Wernicke area helps us comprehend words while Broca area helps us speak them.
What is the Reticular Activating System (RAS)? How is it related to the reticular formation?
The RAS Consists of sensory neurons that that project into the cerebral cortex. It maintains your consciousness when its activated. When its deactivated, it puts you to sleep. The RAS is controlled by the sensory component of the reticular formation
Describe the basic functions of the Hypothalamus.
The anteroinferior region of the diencephalon It's the master control of the autonomic nervous system & the endocrine system Regulates body temperature Controls food intake--hunger sensation Controls water intake--sensation of thirst Regulates sleep-wake cycle (circadian rhythm) Controls emotional behavior (the limbic system)
List the autonomic centers of the medulla & the actions they control.
The autonomic centers within the medulla are the Cardiovascular Center & the Medullary Respiratory Center. Cardiovascular Center is composed of both a cardiac center & vasomotor center; the cardiac center regulates both the heart rate & its force of contraction to alter cardiac output; the vasomotor center controls the contraction & relaxation of smooth muscles within walls of arterioles to alter vessel diameter--both centers influence blood pressure Medullary Respiratory Center regulates the respiratory rate; it is composed of a ventral respiratory group & dorsal respiratory group; it is influenced by the pontine respiratory center; function is to rhythmically initiate nerve signals that cause contraction of the muscles for breathing
Locate & list the functions of the Motor Speech Area.
AKA Broca Area Located within the inferolateral portion of the frontal lobe Controls muscular movements necessary for vocalization
Name the two regions of the limbic system involved in the conversion of short-term memories to long-term memories.
Amygdala & Hippocampus
Identify the brain areas in which cognition occurs.
Association areas of the cerebrum are responsible for cognition
Describe in detail the key structures of the brainstem & their function.
The brainstem connects the cerebrum, diencephalon, & cerebellum to the spinal cord; it is composed of the midbrain, pons, & medulla oblongata. Midbrain: superior portion of brainstem, composed of many different components that contribute to its numerous functions, responsible for relaying voluntary motor commands from the primary motor cortex, produces the neurotransmitter dopamine, houses nuclei of the oculomotor nerve & trochlear nerve which gives rise to its role in processing visual sensory information & relaying visual motor output. The pons: bulging region on the anterior portion of brainstem, houses the pontine respiratory center which regulates skeletal muscles of breathing, functions in coordinating facial movements as it houses many cranial nerves involved in movement of facial muscles. Medulla Oblongata: makes up the inferior portion of the brainstem that is continuous with the spinal cord, contains several autonomic nuclei that form centers which regulate many functions vital for life, these include the cardiovascular center, composed of both the cardiac & vasomotor center, & the medullary respiratory center, these centers give the medulla its role in helping to regulate breathing, HR, BP, & swallowing
Describe in detail the function of the limbic system & highlight at least 2 component parts.
The limbic system is composed of many structures within the cerebrum & diencephalon; these structures collectively process & express emotions; the components of the limbic system include the cingulate gyrus, parahippocampal gyrus, hippocampus, amygdaloid body, olfactory bulbs, tracts, & cortex, & the fornix; all of these structures are involved in either processing & expressing emotions or storing & forming memories; the Hippocampus is one of the structures within the cerebrum that is a part of the limbic system, it is essential in both storing & forming long-term memories; the amygdaloid body is found attached to the hippocampus, it is involved in several aspects of emotion, especially fear; the amygdaloid body also helps store & code memories based on how an individual emotionally perceived the memory
What are the functions of the Occipital Lobe?
Vision
What is the function of the Optic Nerve (CN II)?
Vision
What are the functions of the Frontal Lobe?
Voluntary function, concentration, communication, decision making, planning, & personality
What are the functions of the Cerebellum?
Coordinates & fine tunes skeletal muscle movements that are initiated by the cerebrum; ensures muscle contractions follow the correct pattern, leading to smooth, coordinated movements; stores memories of previously learned movement patterns; skeletal muscle activity is adjusted to maintain equilibrium & posture; receives proprioceptive information from muscles & joints to use for regulating body position; helps regulate behavioral expression & cognitive skills, as well as language processing & retrieval
Explain the phenomenon of cerebral lateralization
Explains how the two hemispheres aren't exactly alike; each hemisphere has functional specializations; higher order centers within both hemispheres tend to have different by complementary functions
Locate & list the functions of the Frontal Eye Field.
Located within the frontal lobe, superior to the motor speech area Controls & regulates eye movements needed for reading & coordinating binocular vision
Describe the functions of the pineal gland & how it relates to the circadian rhythm.
Secretes melatonin, regulates day-night cycles (circadian rhythm) Regulates the sensations of sleepiness & wakefulness by secreting or not secreting melatonin
Explain the involuntary actions produced by the superior & inferior colliculi
The superior & Inferior colliculi are relay stations in processing pathway of visual & auditory sensory input Superior Colliculi is called the visual reflex center; it helps visually track moving objects & control reflexes such as turning the eyes & head in response to visual stimuli Inferior Colliculi is called the auditory reflex center; it controls reflexive turning of the head & eyes in the direction of a sound
Describe in detail the functional differences found between the spinal cord & brain.
Brain: controls all of the activities within the human body; it is responsible for controlling thought, memory, emotion, touch, motor function, breathing, temperature, and many other crucial functions. Spinal cord: acts as the pathway from the brain and the rest of the body; relays information from the brain to the body & vice versa.
Describe the basic function of the features within the midbrain
Cerebral Peduncles: motor tracts that relay voluntary motor commands from primary motor cortex Superior Cerebellar Peduncles: connect midbrain to the cerebellum Medial Lemniscus: extend from medulla oblongata to thalamus Tegmentum: contains red nuclei & reticular formation, integrates information from cerebrum & cerebellum Tectum: most posterior region, contains sensory nuclei pairs that are collectively called the tectal plate Substantia Nigra: Bilaterally symmetric nuclei, houses clusters of neurons that produce the neurotransmitter dopamine which affects the brain processes to control movement, emotional response, & ability to experience pleasure & pain
Explain the interactions of the prefrontal cortex & limbic system in expression of emotions
Expression of emotions is interpreted by the limbic system but ultimately controlled by the prefrontal cortex
Define Sensory Homunculus.
Functional diagram of the primary somatosensory cortex; surface area of the somatosensory cortex devoted to a specific body region indicates the amount of sensory information collected there.
What are the 12 Cranial Nerves?
I: Olfactory Nerve II: Optic Nerve III: Oculomotor Nerve IV: Trochlear Nerve V: Trigeminal Nerve VI: Abducens Nerve VII: Facial Nerve VIII: Vestibulocochlear Nerve IX: Glossopharyngeal Nerve X: Vagus Nerve XI: Accessory Nerve XII: Hypoglossal Nerve
Identify the functions of the left & right hemispheres in most individuals
Left hemisphere is referred to as the Categorical hemisphere; it's specialized for language abilities & important in performing sequential & analytical reasoning tasks; directs or partitions information into smaller fragments for analysis; functions in categorization & identification Right hemisphere is referred to as the Representational Hemisphere; it's concerned with visuospatial relationships & analyses; it's the seat of imagination & insight, musical & artistic skills, perception of patterns & spatial relationships; also comparison of sights, sounds, smells, & tastes
Describe in detail the functions associated with each cerebral hemisphere.
Left hemisphere: Categorical hemisphere; typically the location of the Wernicke & Broca areas; specialized for language abilities & is important in performing sequential & analytical reasoning tasks; functions in categorization & identification. Right hemisphere: Representational hemisphere; concerned with visuospatial relationships & analyses; location of imagination & insight, musical & artistic skills, perception of patterns & spatial relationships, & comparison of sights, sounds, smells, & tastes
Locate & list the functions of the Gnostic Area.
Located among the sensory, visual, & auditory association areas Receives nerve impulses from these areas in order for a common thought to be formed from various sensory inputs
Locate & list the functions of the Primary Visual Cortex.
Located within the occipital lobe Receives, processes, & stores incoming visual information
Locate & list the functions of the Primary Somatosensory Cortex.
Located within the postcentral gyrus in the parietal lobe Responsible for receiving, processing, & storing somatic sensory information; information comes from receptors of the skin and sensory input from proprioceptors
Locate & list the functions of the Primary Motor Cortex.
Located within the precentral gyrus in the frontal lobe Controls voluntary skeletal muscle function; left primary motor cortex controls skeletal muscle of the right side of the body & right primary motor cortex controls skeletal muscle of the left side of the body
Locate & list the functions of the Primary Auditory Cortex.
Located within the temporal lobe Receives, processes, & stores auditory information
Locate & list the functions of the Primary Olfactory Cortex.
Located within the temporal lobe Receives, processes, & stores odor information
What are the important regions within the parietal lobe?
Primary Somatosensory Cortex Postcentral gyrus Ends anteriorly at the central sulcus, posteriorly at parieto-occipital sulcus, & laterally at the lateral sulcus
What is the main function of the limbic system?
Process & initiate emotions
Describe the components & function of the reticular formation
Reticular formation has both a motor & sensory component Motor Component: communicates with spinal cord & is responsible for regulating skeletal muscle tone; also assists in reflexive motor functions, such as respiration, BP, & HR by working with autonomic centers in the medulla & pons Sensory Component: responsible for alerting cerebrum to incoming sensory information--this is the reticular activating system; it keeps us in a state of mental alertness & arouses us from sleep
What is the function of the Vagus Nerve (CN X)?
Sensory: Lower pharynx & larynx, thoracic/abdominal viscera, aortic arch and body Motor: Speech, swallowing, thoracic and abdominal viscera PSNS: Glands of pharynx, larynx, thoracic and abdominal viscera
Describe in detail the key structures of the diencephalon & their function.
The components of the diencephalon include the epithalamus, thalamus, & hypothalamus. Epithalamus: forms part of the posterior roof of the diencephalon & covers the third ventricle, houses the pineal gland & habenular nuclei, functions in regulating individuals circadian rhythm through the pineal gland & relaying signals from the limbic system to the midbrain through the habenular nuclei. Thalamus: forms the superolateral walls of the third ventricle within the diencephalon, sensory nerve signals from all the conscious senses (except olfaction) converge here, it's the principal & final relay point for the incoming sensory information that is processed & then transmitted to the appropriate region of the cerebral cortex. Hypothalamus: anteroinferior portion of the diencephalon, attached to the pituitary gland via the infundibulum, functions as the master control of both the autonomic nervous system & endocrine system, responsible for regulating body temperature & circadian rhythms, controls food & water intake, & controls emotional behavior.
Describe in detail the function of the hypothalamus.
The hypothalamus is responsible for numerous functions within the body; it is the mater control of both the autonomic nervous system & endocrine system; It's a major autonomic integration center, it projects descending axons to autonomic nuclei in the brainstem that influence activities such as HR, BP, digestion, & respiration; its also secretes hormones that control secretory activities in many areas of the endocrine system; its also responsible for temperature regulation; functions in controlling food & water intake as its neurons are responsible for producing both the sensation of hunger & thirst; regulates the circadian rhythm because an area within the structure directs the pineal gland to secrete melatonin at certain times of the day; controls emotional behavior as its located at the center of the limbic system
Describe in detail how a stroke at the precentral gyrus of the right cerebral hemisphere would affect the individual.
The primary motor cortex is located within the precentral gyrus. Neurons within this region control voluntary skeletal muscle activity. The axons here project contralaterally, meaning that the right primary motor cortex controls the skeletal muscle of the left side of the body & vice versa. So if an individual were to have a stroke within the precentral gyrus of the right hemisphere, they would experience deficits in the voluntary skeletal muscle movement on the left side of the body.
Describe the action of the thalamus on sensory information
The thalamus acts as an information filter It is the principle & final relay point for incoming sensory information that is processed & projected to the appropriate lobe of the brain It is responsible for filtering out sounds & sights in busy areas, clues in the cerebrum about where sensory information is coming from
Describe in detail the functions of the thalamus.
The thalamus is the principal & final relay point for incoming sensory information; the information is processed & then sent to the appropriate region of the cerebral cortex; it also helps the cerebrum determine where specific sensory information is coming from.
What is the function of the Trigeminal Nerve (CN V)?
Three divisions: V1 (ophthalmic), V2 (maxillary), & V3 (mandibular); receives sensory input from face, oral cavity, nasal cavity, meninges, & anterior scalp; sends motor output to muscles for mastication
What is the role of the Corpus Callosum?
To connect the two hemispheres; the main method of communication between the two hemispheres
What are the functions of the Parietal Lobe?
Tough & proprioception
What is the function of the Facial Nerve (CN VII)?
Transmits taste sensation from anterior 2/3 of tongue; innervates muscles of facial expression
What is the function of the Vestibulocochlear Nerve (CN VIII)?
Two branches: Vestibular & Cochlear Branch Vestibular branch transmits nerve signals for equilibrium Cochlear branch transmits nerve signals for hearing