SCB204 Quiz 2

Identify and describe the four spinal nerve plexuses, and give examples of nerves that emerge from each

4 major nerve plexuses are found, which - together with their peripheral nerves - are described below: 1. Cervical plexus - arises from the ventral rami of C1 - C5 - supplies muscles of the shoulder and neck - major motor branch is the phrenic nerve - arises from C3 - C5 - innervates the diaphragm "The primary danger of a 'broken neck' is that the phrenic nerve may have been severed, leading to paralysis, cessation of breathing and death ..." 2. Brachial plexus - arises from ventral rami of C5 - C8, and T1 - subdivides into 5 major peripheral nerves which are: 1. Axillary nerve - serves the muscles and skin of the shoulder, e.g. deltoid muscle - damage causes paralysis and atrophy of deltoid 2. Radial nerve - large peripheral nerve which innervates all extensor muscles of the arm, forearm and hand; and all the skin along the way; - e.g. triceps brachialis - damage causes wrist drop and inability to extend hand at wrist; 3. Median nerve - runs down anterior of the arm - supplies most of the flexor muscles in the forearm and several muscles in the lateral part of the hand; - damage causes inability to pick up small objects due to decrease ability to flex and abduct thumb and index finger; 4. Musculocutaneous nerve - innervates the arm muscles that flex the forearm and of the skin of the lateral surface of the forarm; - damage leads to decreased ability to flex the forearm; 5. Ulnar nerve - runs down along the postero-medial surface of the arm; - supplies the flexor carpi ulnaris muscle and all intrinsic muscles of the hand not served by the median nerve; - damage causes typical "clawhand" with inability to spread fingers apart; 3. Lumbar plexus - arises from the central rami of L1 - L4; embedded deep within psoas muscle, - innervates the lower abdominal region and the anteromedial thigh; the obturator nerve - another important nerve associated with this plexus is the obturator nerve; - innervates the adductor muscles of the medial thigh and small hip muscles; also serves the skin of the medial thigh and hip joint; - damage leads to inability to adduct the thigh; the femoral nerve - the largest nerve of this plexus is the femoral nerve; - innervates the anterior thigh muscles, lower abdomen, buttocks, and the skin of the anteromedial leg and thigh; - damage causes inability to extend leg and to flex the hip; 4. Sacral plexus - arises from L4 - S4 - peripheral nerves of this plexus innervate the buttock, the posterior thigh and virtually all of the leg and foot; - the major nerve of this plexus is the sciatic nerve; - it is the largest nerve of the human body! - travels through the greater sciatic notch of the hip bone down to the posterior thigh; - innervates the lower trunk and the posterior surface of thigh and leg; - damage leads to inability to extend hip and to flex the knee -> "sciatica" - divides in the popliteal region into the: 1. Common fibular nerve - innervates the lateral aspect of the leg and foot; - damage leads to inability to dorsiflex the foot -> "footdrop" and 2. Tibial nerve - innervates the posterior aspect of the leg and foot; - damage leads to inability to plantar flex and invert the foot -> "shuffling gait"; - another important nerve of this plexus is the superior and inferior gluteal nerve; - innervates the gluteal muscles of the hip;

Spinal nerve motor functions are summarized in the table below

Actions of the spinal nerves Level Motor Function C1-C6 Neck flexors C1-T1 Neck extensors C3, C4, C5 Supply diaphragm (mostly C4) C5, C6 Move shoulder, raise arm (deltoid); flex elbow (biceps) C6 Externally rotate (supinate) the arm C6, C7 Extend the elbow and wrist (triceps and wrist extensors); pronate wrist C7, C8 Flex wrist; supply small muscles of the hand T1-T6 Intercostals and trunk above the waist T7-L1 Abdominal muscles L1-L4 Flex thigh L2, L3, L4 Adduct thigh; extend leg at the knee (quadriceps femoris) L4, L5, S1 Abduct thigh; flex leg at the knee (hamstrings); dorsiflex foot (tibialis anterior); extend toes L5, S1, S2 Extend leg at the hip (gluteus maximus); plantar flex foot and flex toes

Explain how decussation occurs in sensory and motor pathways, and predict how this presents in individuals with brain and spinal cord injuries

Decussation: crossing over. because of this, the right side of the brain interacts with the left side of the body and vice versa. Tracts -communicates between CNS, PNS, and peripheral organs -relay sensory and motor information between periphery and higher brain centers -Sensory (ascending) : spinal cord to brain -Motor (descending) : from brain to spinal cord or from spinal cord to more inferior region Sensory Tracts -Conduct sensory impulses upward through chains of 3 successive neurons -Decussation occurs Medial Lateral Rule -Farther down on body=more medial in spinal cord Posterior Column -Carry information about limb position (proprioception), fine touch, pressure, and vibration from skin and musculoskelatal system 1st order neurons: skin/muscles to medulla oblongata 2nd order neurons: decussate to contralateral side and ascend to thalamus 3rd order neurons: from thalamus to primary sensory cortex Anterior Spinothalamic Tract -Carry information about crude touch and pressure 1st order neuron: from periphery to dorsal horn at level of entry 2nd order neuron: decussate at level of entry and ascend to thalamus 3rd order neuron: from thalamus to primary sensory cortex Lateral Spinothalamic Tract -carry information about pain and temperature 1st order neuron: from periphery to dorsal horn at level of entry 2nd order neuron: decussate at level of entry, ascend to thalamus 3rd order neuron: from thalamus to primary sensory cortex Spinocerebellar Tract -carry information about position of muscles, tendons, and joints (proprioception) 1st order neurons: from joints/muscles to dorsal horn 2nd order neurons: -some decussate at level of entry, ascend to cerebellum and decussate again to return to ipsilateral side -some stay on ipsilateral side as they ascend to cerebellum

Identify and describe the anatomical features seen in a cross-sectional view of the spinal cord

Gray matter made of somas and dendrites of neurons, no myelin -forms the posterior horn, gray commissure, lateral horn, and anterior horn Dorsal horn section of gray matter that extends toward posterior part of the spinal cord, has sensory neurons Ventral horn section of gray matter that extends toward anterior part of the spinal cord, has motor neurons Posterior median sulcus longitudinal shallow groove on posterior side of the spinal cord Anterior median fissure deeper longitudinal groove on the anterior part of the spinal cord Gray commissure section of gray matter that connects the right and left halves of the spinal cord, gray matter around the central canal Central canal opening found in the middle of the gray commissure, lined with ependymal cells and filled with CSF White matter made of axons, myelin is present -forms the posterior, lateral, and anterior columns Columns (funiculi) bundle of axons traveling up and down the spinal cord, provide avenues of communication between different levels of the CNS Posterior funiculus column between the dorsal horn and the posterior median sulcus Lateral funiculus column between the dorsal horn and lateral horn Anterior funiculus column between the anterior horn and anterior median fissure Tracts a collection of multiple nerve fibers (axons) in the CNS that have similar origin, destination, and function Ascending tract carry sensory input up the spinal cord from receptors, towards the brain Descending tract conduct motor output down the spinal cord away from the brain, towards effector organs

Describe the functions of the limbic system and the reticular formation

Limbic system - important functional brain system. "seat of emotions" *Found within mammalian brains *Gray matter that includes limbic lobe (region of medial cerebrum), hippocampus, amygdala. * Involved in memory, learning, emotion, and behavior the reticular formation plays a central role in states of consciousness like alertness and sleep Therefore, people who have difficulties with pain, alertness, or physical coordination might have damage to their reticular formation

Distinguish between a monosynaptic and polysynaptic reflex arc

Monosynaptic reflexes: Involve only one synapse in CNS, there is minimal synaptic delay meaning fastest response, no interneurons. Polysynaptic reflexes: Involve at least one internueron, longer synaptic delay due to 2 or more synapses. Can provide more complicated responses because interneurons can activate several muscle groups simultaneously.

Distinguish between somatic and visceral reflexes and list examples

Motor division- consists of motor (efferent) neurons; carry out motor functions of nervous system; subdivisions based on organs that neurons contact: Somatic motor division -responsible for voluntary motor functions; composed of lower motor neurons (somatic motor neurons) which directly trigger skeletal muscle contractions Visceral motor division (autonomic motor nervous system, ANS) - responsible for maintaining many aspects of homeostasis by controlling involuntary motor functions in body; neurons innervate cardiac muscle cells, smooth muscle cells, and secretory cells of glands

Discuss how the structures root, nerve, ramus, plexus, tract, and ganglion relate to each other

Nerve- Collection or bunch of axons in PNS example spinal nerve and cranial nerves Tract-collection or bunch of axons in CNS. Found in columns in the spinal cord( they travel up/down the white matter thus can be ascending and descending or white matter of the brain (projection, commissural and association tracts. Distinguish between ascending (sensory) and descending (motor) tracts in the spinal cord. Ascending tracts Descending tracts Ascending tracts Are always SENSORY carry sensory information up the spinal cord towards the brain. Examples: Fasciculus Gracilis and cuneatus, spinothalamic, spinocerebellar Descending tracts Are Always MOTOR conduct motor impulses down the spinal cord towards effectors Examples: Corticospinal Rubrospinal Tectospinal Dorsal Root Ganglia thicking on the dorsal root that contains cell bodies (Somas) of sensory neurons. Part of PNS. Dorsal Root Sensory Fibers passing Posteriorly through the intervertebral foramen towards the back of the spinal cord. Ventral root Motor fibers passing anteriorly toward the front on the spinal cord from the ventral horn. Spinal Nerves are always mixed( have both sensory and motor fibers of ventral and dorsal roots) nerves formed by junction of dorsal and ventral roots that innervate the body below the head. The Anterior and posterior roots converge into the spinal nerve which exits the spinal cord through the intervertebral foramina and then branches into posterior and anterior rami. Most (but not all) anterior rami form the 5 different plexuses that further branch to innervate different parts of the body. The sensory axons in the dorsal root come from the sensory neurons somas in the dorsal root gaglion. Information from the spinal nerves is carried up in ascending tracts and down the spinal cord in descending tracts. Only the gaglion is formed of somas of neurons. Roots, nerves, rami, tracts are formed of axons.

Compare and contrast the two main types of neural circuits in the CNS.

Neural circuits - patterns of synaptic connection between neural pools; two basic types of neural circuits: Diverging circuits Converging circuits ***Diverging circuits begin with a single input neuron axon that branches out to make contact with multiple postsynaptic neurons that follow same pattern • Critical because they allow a single neuron to communicate with multiple parts of brain and/or body • Characteristic of those transmitting incoming sensory information sent from spinal cord to different neuronal pools in brain for processing ***Converging circuits -basically opposite configuration of diverging circuits; axon terminals from multiple input neurons converge on onto a single postsynaptic neuron • Critical for control of skeletal muscle movement • Allow nervous system to respond to sensory information that it collects and processes

Define a neuronal pool, and explain its purpose.

Neuronal pools - groups of interneurons within CNS: Composed of neuroglial cells, dendrites, and axons in one location and cell bodies in another location Type of information processed by a pool is defined by synaptic connections of pool Connections between pools allow for complex mental activity such as planned movement, cognition, and personality Input neurons initiate series of signals that starts activity of a pool

Describe the specific functions of each pair of cranial nerves, and classify each pair as sensory, motor, or mixed nerves

Olfactory Number: 1 Type: Sensory Function: Sense of Smell Optic Number: 2 Type: Sensory Function: Vision Oculomotor Number: 3 Type: Motor Function: Raise eyelids, move eyes, regulate the size of pupils, focus of lenses. Trochlear Number: 4 Type: Motor Function: Eye movements, proprioception Trigeminal Number: 5 Type: Mixed Function: Sensations of the head and face, chewing movements, and muscle sense. Abducens Number: 6 Type: Motor Function: Produce movements of the eyes Facial Number: 7 Type: Mixed Function: Facial expressions, secretion of saliva, taste. Vestibulocochlear Number: 8 Type: Sensory Function: Balance or equilibrium sense. Hearing. Glossopharyngeal Number: 9 Type: Mixed Function: Taste and other sensations of tongue, swallowing, secretion of saliva, aid in reflex control of blood pressure and respiration. Vagus Number: 10 Type: Mixed Function: Transmit impulses to muscles associated with speech, swallowing, the heart, smooth muscles of visceral organs in the thorax, and abdomen. Accessory Number:11 Type: Motor Function: Turning movements of the head, movements of the shoulder and viscera, voice production. Hypoglossal Number:12 Type: Motor Function: Tongue movements

Identify the cranial nerves by name and number

Olfactory Number: 1 Type: Sensory Function: Sense of Smell Optic Number: 2 Type: Sensory Function: Vision Oculomotor Number: 3 Type: Motor Function: Raise eyelids, move eyes, regulate the size of pupils, focus of lenses. Trochlear Number: 4 Type: Motor Function: Eye movements, proprioception Trigeminal Number: 5 Type: Mixed Function: Sensations of the head and face, chewing movements, and muscle sense. Abducens Number: 6 Type: Motor Function: Produce movements of the eyes Facial Number: 7 Type: Mixed Function: Facial expressions, secretion of saliva, taste. Vestibulocochlear Number: 8 Type: Sensory Function: Balance or equilibrium sense. Hearing. Glossopharyngeal Number: 9 Type: Mixed Function: Taste and other sensations of tongue, swallowing, secretion of saliva, aid in reflex control of blood pressure and respiration. Vagus Number: 10 Type: Mixed Function: Transmit impulses to muscles associated with speech, swallowing, the heart, smooth muscles of visceral organs in the thorax, and abdomen. Accessory Number:11 Type: Motor Function: Turning movements of the head, movements of the shoulder and viscera, voice production. Hypoglossal Number:12 Type: Motor Function: Tongue movements

Explain the roles of the cerebral cortex, basal nuclei, and cerebellum in movement

One of the brain areas most involved in controlling these voluntary movements is the motor corte basal nuclei 1) Play a major role in the initiation and termination of movements. Two parts: Caudate nucleus and putamen- receive input from sensory, association and motor areas of cerebral cortex and from the substantia nigra. Output comes from the globes pallidus and substantia nigra, which send feedback signals to the Upper Motor cortex by way of THALAMUS. this circuit-from CORTEX->BASAL NUCLEI -> THALMUS->CORTEX-appears to function in initiating and terminating movements Neurons in putamen generate impulses just before eye movement occur. 2) Suppress unwanted movements by their inhibitory effects on the thalamus and uperior colliculus 3) Influence muscle tone. Globus pallidus sends into reticular formation that reduce muscle tone. Damage/ Destruction of some Basal Nuclei connections causes a generalize increase in muscle tone. 4) Influence many aspects of cortico functions- sensory, limbic, cognitive, and linguistic functions (cognitive- attention, memory, planning) Cerebellum 1) Monitoring intentions for movement- the cerebellum receives impulses from motor cortex and basal nuclei via pontine nuclei in the PONS regarding what movements are planned 2) Monitoring actual movements- cerebellum receives input from proprioceptors in joint and muscles that reveals what actually is happening. Nerve impulses travel down posterior spinobellar tracts. Nerve impulses from vestibular apparatus in inner ear and from eyes enter the cerebellum 3) Comparing command signals w/ sensory info- compares intentions for movement w/ actual movement performed. 4) Sending out correct feedback- If there is a discrepancy between intended and actual movements, the cerebellum sends feedback to UMNs. This info travels via THALAMUS to UMNs in the cerebral cortex but goes directly to the UMNs in BRAIN STEM motor centers. As movement occurs, the cerebellum is always correcting UMN errors, which decreases errors and smoothes the motion. Also contributes over longer periods to learning of new motor skills

Describe and identify the five lobes of the cerebral cortex, and explain how motor and sensory functions are distributed among the lobes

The cerebral cortex can be divided into four sections, which are known as lobes. The frontal lobe, parietal lobe, occipital lobe, and temporal lobe have been associated with different functions ranging from reasoning to auditory perception. The frontal lobe is located at the front of the brain and is associated with reasoning, motor skills, higher level cognition, and expressive language. At the back of the frontal lobe, near the central sulcus, lies the motor cortex. This area of the brain receives information from various lobes of the brain and utilizes this information to carry out body movements. Damage to the frontal lobe can lead to changes in sexual habits, socialization, and attention as well as increased risk-taking. The parietal lobe is located in the middle section of the brain and is associated with processing tactile sensory information such as pressure, touch, and pain. A portion of the brain known as the somatosensory cortex is located in this lobe and is essential to the processing of the body's senses. The temporal lobe is located on the bottom section of the brain. This lobe is also the location of the primary auditory cortex, which is important for interpreting sounds and the language we hear. The hippocampus is also located in the temporal lobe, which is why this portion of the brain is also heavily associated with the formation of memories. Damage to the temporal lobe can lead to problems with memory, speech perception, and language skills. The occipital lobe is located at the back portion of the brain and is associated with interpreting visual stimuli and information. The primary visual cortex, which receives and interprets information from the retinas of the eyes, is located in the occipital lobe. Damage to this lobe can cause visual problems such as difficulty recognizing objects, an inability to identify colors, and trouble recognizing words

Describe the gross anatomy and location of the spinal cord

The inferior portion of the Central Nervous System; the thick, whitish, cylindrical (slightly flattened dorso-ventrally) mass of nervous tissue that extends from the medulla oblongata down through the upper two-thirds of the spinal canal in the vertebral column to the upper lumbar region and from which the spinal nerves branch off to various parts of the body; the nervous tissue consists of nerve fibers and nerve cells, the latter being confined to the gray matter of the central portions of the cord, while the peripheral white matter is composed of nerve fibers only; the center of the cord is traversed by a slender canal connecting with the ventricles of the brain which contains cerebrospinal fluid

Describe the overall pathway from the decision to move to the execution and monitoring of a motor program

The motor pathways are pathways which originate in the brain or brainstem and descend down the spinal cord to control the a-motor neurons. These large neurons in the ventral horns of the spinal cord send their axons out via the spinal roots and directly control the muscles. The motor pathways can control posture, reflexes, and muscle tone, as well as the conscious voluntary movements that we think of when we hear "motor system". The most famous pathway is the so called "pyramidal system", which begins with the large pyramidal neurons of the motor cortex, travels through the pyramids of the brainstem, (somewhere in here there is a coincidence), and finally ends on or near the a-motor neurons. This system is extremely important clinically, as strokes often affect the motor system. Therefore it is crucial to understand the anatomy of the motor pathway..

Describe the roles of the central and peripheral nervous systems in processing sensory stimuli

The nervous system has two different major parts. The two parts are the central nervous system and the peripheral nervous. The central nervous system or the CNS contains the brain and the spinal cord. All together, the brain and the spinal cord serve the nervous system's command station. When the sensory input reaches the CNS, the spinal cord and the brain figure outs what it exactly means. After, they quickly orders out the body parts that needs to move faster. Everything else but the CNS it is known as the peripheral nervous system. The peripheral nervous system or PNS contains the nerves, which leave the brain and the spinal cord and travel to certain areas of the body. The peripheral nervous system's main job is to send information gathered by the body's sensory receptors to the CNS as quickly as possible. Once the CNS has understood the information, the PNS will relay the specific orders back out the body. These nerves which carry information in a way of nerve impulses to and from the brain are called cranial nerves. The nerves that carry impulse to and are carrying information from the spine are called spinal nerves. The PNS has two important parts. They are the motor division and the sensory division. The sensory division collects the impulses from the sensory receptors in areas like skin, muscles, and organs, and also carries those impulses through the nerves to the CNS. The motor division collects the outgoing messages from the CNS and delivers them to the appropriate body organs, telling them what to do. The motor division does the opposite from the sensory division

Identify the cranial meninges, and explain their functional relationship to the brain

There are 3 layers of protection and support between the brain and the skull: The Dura mater, the arachnoid layer, and the pia mater. The dura mater is the "toughest" layer, the pia mater is the "softest" layer. The arachnoid layer is filled with a web of collagen. **Structural arrangement from superficial to deep: epidural space, dura mater, subdural space, arachnoid mater, subarachnoid space, and pia mater. 1.Epidural space- Between bone and dura mater 2.Dura Mater- outermost meningeal layer. Thickest and most durable; double-layered composed of collagen and elastic fibers 3.Subdural space- Fluid filled space; houses veins that drain blood from brain. 4.Arachnoid mater - second meningeal layer deep to subdural space. Thin, weblike membrane with dense irregular collagenous tissue w/some degree of elasticity. 5.Subarachnoid space - found deep to arachnoid mater and superficial to pia mater; contains major blood vessels of brain. filled with CSF 6.Pia mater - deepest meningeal layer.only layer in physical contact with brain tissue. Follows contour of brain, covering delicate tissue of sulcus and fissure. Permeable to substances in brain extracellular fluid and CSF. allows for substances to move between these two fluid compartments. helps to balance concentration of different solutes found in each fluid.

What does the flexor reflex involve to illustrate another feature of the polysynaptic reflex arc?

involves contraction of more than one muscle group

The flexor reflex is what?

ipsilateral

Describe the difference between ascending and descending tracts in the spinal cord

ascending tract carry sensory information to the brain; descending tract conducts motor impulses from the brain to muscles and oil glands

Describe the functions of CSF as well as the details of its production, its circulation with the CNS, and its ultimate reabsorption into the bloodstream.

**CSF- Protects brain in following ways: -Cushions brain and maintains a constant temperature within cranial cavity. -Removes wastes. -Increases buoyancy of brain...keeps brain from collapsing under its own weight. **Choroid plexuses - where majority of CSF is made. *found in each ventricle where blood vessels come into direct contact with ependymal cells (also produce some CSF themselves). *CSF circulates through brain and spinal cord; old CSF must be removed as choroid plexuses make new CSF. Process of CSF production and removal occurs constantly. CSF is completely replaced every 5-6 hours. **Pathway for formation, circulation, and reabsorption of CSF : 1. Fluid and electrolytes leak out of capillaries of choroid plexuses into ECF of ventricles. 2. Taken up into ependymal cells and then secreted into ventricles as CSF. 3. Circulated through and around brain and spinal cord in subarachnoid space. assisted by movement of ependymal cell cilia. 4. Some CSF is reabsorbed into venous blood in dural sinuses.

Describe components of a reflex arc

1. Receptor: stimulus at distal end of neuron 2. Sensory neuron 3. Integration center in CNS 4. Motor neuron 5. Effector

Describe the locations and functions of the upper and lower motor neurons in a motor pathway

1.Cell bodies of the upper motor neurons are bigger in size than cell bodies of the lower neurons. 2.Upper motor neurons are classified according to the pathways they travel in. Lower motor neurons are classified according to the type of muscle fiber they innervate as they have only one path which is called the final common pathway. Upper motor neurons have six pathways. Lower motor neurons are divided into two groups, the alpha and gamma motor neurons. 3.Upper motor neurons carry information from brain centers that control the muscles of the body, and lower motor neurons carry information passed to them from the upper motor neurons. 4.Upper motor neurons form synapses with the lower motor neurons. On the other hand, lower motor neurons form synapses with the muscles in the body. 5.Upper motor neurons are first-order neurons whilst lower motor neurons are second-order neurons. 6.The cell bodies of the upper motor neurons are located in the cortex of the brain and the cell bodies of the lower motor neurons are located in the grey matter of the spinal cord and brain stem.

Describe the locations and functions of first-, second-, and third-order neurons in a sensory pathway

A sensory neuron that delivers sensations to the CNS is a first-order neuron. Within the CNS, the axon of the first-order neuron synapses on a second-order neuron, which is an interneuron located in the spinal cord or brain stem. The second-order neuron synapses on a third-order neuron in the thalamus. The axons of the third-order neurons synapse on neurons of the primary sensory cortex of the cerbral hemispheres

Describe the structure and function of each major area of the brain

Brain Structures and their Functions Cerebrum Cerebellum Limbic System Brain Stem The nervous system is your body's decision and communication center. The central nervous system (CNS) is made of the brain and the spinal cord and the peripheral nervous system (PNS) is made of nerves. Together they control every part of your daily life, from breathing and blinking to helping you memorize facts for a test. Nerves reach from your brain to your face, ears, eyes, nose, and spinal cord... and from the spinal cord to the rest of your body. Sensory nerves gather information from the environment, send that info to the spinal cord, which then speed the message to the brain. The brain then makes sense of that message and fires off a response. Motor neurons deliver the instructions from the brain to the rest of your body. The spinal cord, made of a bundle of nerves running up and down the spine, is similar to a superhighway, speeding messages to and from the brain at every second. The brain is made of three main parts: the forebrain, midbrain, and hindbrain. The forebrain consists of the cerebrum, thalamus, and hypothalamus (part of the limbic system). The midbrain consists of the tectum and tegmentum. The hindbrain is made of the cerebellum, pons and medulla. Often the midbrain, pons, and medulla are referred to together as the brainstem. The Cerebrum: The cerebrum or cortex is the largest part of the human brain, associated with higher brain function such as thought and action. The cerebral cortex is divided into four sections, called "lobes": the frontal lobe, parietal lobe, occipital lobe, and temporal lobe. Here is a visual representation of the cortex: Image of Cerebral Cortex What do each of these lobes do? Frontal Lobe- associated with reasoning, planning, parts of speech, movement, emotions, and problem solving Parietal Lobe- associated with movement, orientation, recognition, perception of stimuli Occipital Lobe- associated with visual processing Temporal Lobe- associated with perception and recognition of auditory stimuli, memory, and speech Note that the cerebral cortex is highly wrinkled. Essentially this makes the brain more efficient, because it can increase the surface area of the brain and the amount of neurons within it. We will discuss the relevance of the degree of cortical folding (or gyrencephalization) later. (Go here for more information about cortical folding) A deep furrow divides the cerebrum into two halves, known as the left and right hemispheres. The two hemispheres look mostly symmetrical yet it has been shown that each side functions slightly different than the other. Sometimes the right hemisphere is associated with creativity and the left hemispheres is associated with logic abilities. The corpus callosum is a bundle of axons which connects these two hemispheres. Nerve cells make up the gray surface of the cerebrum which is a little thicker than your thumb. White nerve fibers underneath carry signals between the nerve cells and other parts of the brain and body. The neocortex occupies the bulk of the cerebrum. This is a six-layered structure of the cerebral cortex which is only found in mammals. It is thought that the neocortex is a recently evolved structure, and is associated with "higher" information processing by more fully evolved animals (such as humans, primates, dolphins, etc). The Cerebellum: The cerebellum, or "little brain", is similar to the cerebrum in that it has two hemispheres and has a highly folded surface or cortex. This structure is associated with regulation and coordination of movement, posture, and balance. The cerebellum is assumed to be much older than the cerebrum, evolutionarily. What do I mean by this? In other words, animals which scientists assume to have evolved prior to humans, for example reptiles, do have developed cerebellums. However, reptiles do not have neocortex. Go here for more discussion of the neocortex or go to the following web site for a more detailed look at evolution of brain structures and intelligence: "Ask the Experts": Evolution and Intelligence Limbic System: The limbic system, often referred to as the "emotional brain", is found buried within the cerebrum. Like the cerebellum, evolutionarily the structure is rather old. This system contains the thalamus, hypothalamus, amygdala, and hippocampus. Image of the Limbic System Thalamus Hypothalamus Amygdala Hippocampus Brain Stem: Underneath the limbic system is the brain stem. This structure is responsible for basic vital life functions such as breathing, heartbeat, and blood pressure. Scientists say that this is the "simplest" part of human brains because animals' entire brains, such as reptiles (who appear early on the evolutionary scale) resemble our brain stem. Look at a good example of this here. The brain stem is made of the midbrain, pons, and medulla. Click on the words to learn what these structures do: Midbrain Pons Medulla

Describe the structural basis for and the importance of the blood-brain barrier

Blood Brain Barrier (BBB) is a barrier with selective permeability to protect and maintain a constant environment for neurons Consists of endothelium of capillaries (with tight junctions), basal lamina (basement membrane), and the astrocytes Allows H2O, glucose, CO2, caffeine, and nicotine to freely Substances that easily pass through plasma membranes are able to pass through blood-brain barrier; include water, oxygen, carbon dioxide, and nonpolar, lipid- based molecules •Protein channels or carriers allow for passage of other essential molecules across blood-brain barrier; include glucose, amino acids, and ions •Most large, polar molecules are effectively prevented from crossing blood-brain barrier in any significant amount; while barrier is protective, it can hinder access of medications into brain

Describe the five developmental regions of the brain and identify the major areas of the adult brain that arise from each region

Cerebrum Telencephalon Metencephalon= Cerebellum + pons Diencephalon= Hypothalamus + Thalamus Mesencephalon= Mid brain Myelencephalon=Medulla Oblongata Cerebral hemispheres Diencephalon brain stem (midbrain, pons, and medulla oblongata) Cerebellum Central cavity, surrounded by a gray matter core, external to which is white matter. The cerebrum and cerebellum have an outer gray matter layer, which is reduced to scattered gray matter nuclei in the spinal cord.

does the crossed extensor reflex involve the contralateral side, ipsilateral side or both?

Contralateral side

Describe the gross anatomy of the spinal nerves.

Gross Anatomy Spinal nerves are formed from fusion of anterior root (motor neurons) from anterior horn of spinal cord AND a posterior root (sensory neurons) to posterior horn of spinal cord So spinal nerves are mixed nerves (both motor and sensory neurons) There are 31 pairs of spinal nerves • 8 cervical nerves • 12 thoracic nerves • 5 lumbar nerves • 5 sacral nerves • 1 coccygeal nerve Spinal nerve- short and divides into following 2 mixed nerves; both carry both somatic motor and sensory information: • Both rami are mixed nerves @ Posterior ramus - travels to posterior side of body @ Anterior ramus - travels to anterior side of body and/or to an upper or lower limb - Ramus communicans (Rami communicantes, plural) Small branch of anterior ramus Contains autonomic fibers of the sympathetic nervous system, so only contains visceral motor neurons mixed nerves Anterior rami of thoracic spinal nerves travel between the ribs as intercostal nerves. •These nerves innervate the intercostal muscles, ab muscles, and the skin of the chest and abdomen. Anterior rami of cervical, lumbar, and sacral spinal nerves each merge to form complicated networks of nerves called nerve plexuses • 4 nerve plexuses: Cervical Brachial Lumbar Sacral

Compare and contrast the position of gray and white matter in the spinal cord and brain

In the spinal cord, the outer layer is the white matter and the inner layer is the grey matter.

Describe the crossed extensor reflex.

Involves stimulation of the extensor muscles on the contralateral side of the stimulus

Describe the "stretch reflex".

Involves the reflex contraction of a muscle in response to stretch.

Explain the ways in which special sensory stimuli are processed by the CNS

Info(Smell, vision, taste, balance, hearing )provided by these receptors is distributed to specific locations in the CNS. Receptor specificity or selectivity Each receptor is responsive to a specific type of stimulus while being insensitive to other types. (Exp. May respond to pressure but not chemicals.) What determines the specificity of a receptor? Structure determines the specificity of a receptor. This can result from structure of receptor or specialized structures of accessory cells found around receptive structures All sensory processes begin with stimuli, and all stimuli represent forms of energy. A sensory receptor converts stimulus energy to a change in membrane potential. Therby regulating the output of action potentials to the central nervous system. Decoding of this info with the CNS results in sensation SENSORY RECEPTION & TRANDUCTION: A sensory pathway begins with sensory reception, the detection of a stimulus by sensory cells. Some sensory cells are neurons, some are not but they regulate neurons. Some exist singly.. Others are collected in a sensory organ. Sensory receptor: a sensory cell or organ or a subcellular structure that detects stimuli. Many sensory receptor detect stimuli from outside the body, such as heat, light, pressure, or chemicals. Activating a sensory receptor doesn't require a large amount of stimulus energy, Also, although animals use a range of sensory receptors to detect widely varying stimuli, the effect in all cases is to open or close ion channels. Ion channels either open or close when a substance outside the cells binds to a chemical receptor in the plasma membrane. Thus, letting ions flow in changing the membrane potential. The conservation of a physical or chemical stimulus to a change in the membrane potential of a sensory receptor is sensory transduction. The change in the membrane potential is the receptor potential. The potentials are graded potential. Thus their magnitude varies with the stimulus. TRANSMISSION: Sensory information travels through the nervous system as nerve impulses or action potentials. In sensory neurons, transducing the energy in a stimulus into a receptor potential initiate's action poteials that are transmitted to the CNS. Neurons that act directly sensory receptors produce action potentials and have an axon that extends into the CNS. Non-neuronal sensory receptors cell from chemical synapse with sensory (afferent) neurons and respond to stimuli by increasing the rate at which the afferent neurons produce action potentials. The size of a receptor potential increases with the intensity of the stimulus. In a sensory neuron, a larger receptor potential result in more frequent action potentials. For non-neural receptors, it resuts in more neurotransmitter to be releases. Processing of sensory information can occur before, during and after transmission of action potentials to the CNS. o Thus, the intergration of sensory information begins as soon as the information is received. PERCEPTION When action potentials reach the brain via sensory neurons, circuit of neurons process this imput, generating the perception. Preceptions such be colors, smells, sounds and taste are constructions formed in the brain and do not exist outside of it. Action potentials from sensory receptors travel along neurons that are dedicated to a particular stimulus. These dedicated neurons synapse with particular neurons in the brain or spinal cord. As a result, the brain distinguishes stimuli such as light or sound solely by the path along which the action potentials have arrived.

Describe the general functions of the regions of the diencephalon, cerebellum, and brainstem

Key Points The diencephalon is made up of four main components: the thalamus, the subthalamus, the hypothalamus, and the epithalamus. The hypothalamus is an integral part of the endocrine system, with the key function of linking the nervous system to the endocrine system via the pituitary gland. The thalamus is critically involved in a number of functions including relaying sensory and motor signals to the cerebral cortex and regulating consciousness, sleep, and alertness. The epithalamus functions as a connection between the limbic system to other parts of the brain. Some functions of its components include the secretion of melatonin by the pineal gland (involved in circadian rhythms) and regulation of motor pathways and emotions. Key Terms subthalamus: Receives afferent connections from the substantia nigra and striatum and regulates skeletal muscle movements. thalamus: Either of two large, ovoid structures of gray matter within the forebrain that relay sensory impulses to the cerebral cortex. hypothalamus: A region of the forebrain located below the thalamus, forming the basal portion of the diencephalon, and functioning to regulate body temperature, some metabolic processes, and the autonomic nervous system. epithalamus: The dorsal posterior segment of the diencephalon, involved in the maintenance of circadian rhythms and regulation of motor pathways and emotions. limbic system: A set of brain structures located on both sides of the thalamus, right under the cerebrum. Supports a variety of functions including emotion, behavior, motivation, long-term memory, and olfaction. The cerebellum processes inputs from several structures and coordinates skeletal muscle contraction to produce smooth movement. There are two cerebellar hemispheres consisting of three lobes each. Anterior and posterior lobes coordinate body movements and the flocculonodular lobes adjust posture to maintain balance. Three paired fiber tracts, the cerebellar peduncles, communicate between the cerebellum and the brain stem. Cerebellar processing follows a functional scheme in which the frontal cortex communicates the intent to initiate voluntary movement to the cerebellum, the cerebellum collects input concerning balance and tension in muscles and ligaments, and the best way to coordinate muscle activity is relayed back to the cerebral cortex. the brain stem and function of each > Produces rigidly programmed, automatic behaivors necessary for survival. Brain stem consists of the 1) Midbrain: > Contains cerebral peducles (motor tracts, substantia nigra (produces dopamine), tegmentum (houses red nuclei, helps maintain posture), Tectum (Also called quadrigemina) 2) Pons: >Contains fiber tracts that complete conducting pathways between the brain and spinal cord. > The pontine nuclei relay information from the cerebrum to the cerebellum. > Also houses nuclei for cranial nerves V, VI, VII, VIII, and IX. > Pontine sleep center, which initiates rapid eye movement sleep > Pontine respiratory center, which works with the respiratory centers in the medulla to help control respiratory movements. 3) Medulla oblongata: >Pyramids: houses motor projection tracts (corticospinal or pyramidal tracts) most of which cross to the opposite side (decussation) > Cranial nerve nuclei > Part of the reticular formation > Cardiac center: regulates heart rate and force of contraction > Vasomotor center: controls blood pressure > Medullary respiratory center: regulates respiratory rate > Nuclei that are involved in coughing, sneezing, salivation, swallowing, gagging and vomiting

Define dermatome. Describe the clinical significance of them

an area of skin that receives most of its sensory innervation from one spinal nerve ***C1 is the only spinal nerve without a corresponding dermatome Practical because knowing which spinal cord segments supply each dermatome makes it possible to locate damaged regions of the spinal cord. -ie. If the skin in a particular region is stimulated but the sensation is not perceived, the nerves supplying that dermatome are probably damaged