Unit 4 Test

Describe the function of each of the horns of gray matter in the spinal cord.

-Anterior horn (ventral horn) anterior wing of gray matter; gives rise to anterior motor nerve roots; neuron cell bodied in this region are involved in somatic motor functions (skeletal muscle contraction). -Posterior horn (or dorsal horn) posterior wing of gray matter gives rise to posterior sensory nerve roots; neuron cell bodies in this region are involved in processing incoming somatic sensory and visceral sensory information. -Lateral horn, only in spinal cord between first thoracic vertebra and lumbar region contains cell bodies of neurons involved in control of viscera (smooth and cardiac muscle) via autonomic nervous system (ANS).

Describe the differences between the endocrine system and the nervous system in terms of how they maintain homeostasis.

-Endocrine system secretes hormones into blood to regulate functions of other cells. -Nervous system sends action potentials to excite or inhibit target cells. -Actions of endocrine system are typically slow (take several hours or even days to have an effect) whereas actions of nervous system are generally immediate.

Spinal Cord Meninges and relative spaces that protect the spinal cord.

Brain's meninges pass through foramen magnum to provide a continuous protective covering of spinal cord and distal nerves at base. 1. Epidural space - Anesthetic site 2. Dura mater 3. Arachnoid mater 4. Subarachnoid space - Comprised of a majority of CSF 5. Pia mater- Lies next to spinal cord -Epidural space - due to absence of periosteal dura; cushions and protects spinal cord. -Subdural space - only a potential space dura and arachnoid are normally adhered to one another. -Subarachnoid space - found between arachnoid and pia mater; filled with CSF. base of spinal cord contains a large volume of CSF; useful site for withdrawing samples of CSF for clinical laboratory testing.

Graph of an action potential

Depolarization- membrane potential rises toward zero and then becomes positive briefly Repolarization- membrane potential returns to a negative value Hyperpolarization- membrane potential temporarily becomes more negative than resting membrane potential

Explain how axon diameter and myelination affect conduction velocity.

Larger diameter axons have a higher conduction velocity, which means they are able to send signals faster. This is because there is less resistance facing the ion flow.The larger the diameter of the axon, the less likely the incoming ions will run into something that could bounce them back.

structural types of neurons

Multipolar- with a single axon and multiple dendrites, make up over 99% of all neurons Bipolar- with one axon and one dendrite and a cell body between them; found in eye and olfactory epithelium in nasal cavity Pseudounipolar- have only one fused axon that extends from cell body and divides into two processes; one process carries sensory info from sensory receptors to cell body; other process carries sensory information from cell body to spinal cord; sensory neurons that carry information related to pain, touch, and pressure

Describe the types of peripheral nerves.

Peripheral nerves - main organs of PNS. ▫ consist of axons of many neurons bound together by connective tissue. a) Mixed nerves - contain both sensory and motor neurons. b) Sensory nerves-contain only sensory neurons. c) Motor nerves contain mostly motor neurons. ▫ also some sensory neurons involved in muscle stretch and tension.

Define sensory transduction. Define and describe exteroceptors, interoceptors, and proprioceptors in terms of the general location of each in the body and the origin of the stimuli that each receives.

Sensory transduction - process where a stimulus is converted into an electrical signal: 1. Exteroceptors - usually close to body's surface. detect stimuli originating from outside body. 2. Interoceptors - usually found within body's interior; detect stimuli originating from within body itself. 3. Proprioceptors - in musculoskeletal system. detect movement and position of a joint or body part.

Compare and contrast electrical and chemical synapses.

Synaptic vesicles filled with chemical messengers (neurotransmitters) that transmit signals from pre to postsynaptic neurons are found at chemical synapses. Synaptic cleft - separates presynaptic and postsynaptic neurons found in chemical synapses where gap junctions connect neurons in electrical synapses. Neurotransmitter receptors are on postsynaptic neuron.These bind to neurotransmitter secreted from presynaptic neuron that has diffused across synaptic cleft. Chemical synapses are unidirectional, unlike electrical synapses, but allow for variable signal intensities.

Sensory cranial nerves

Three cranial nerves contain axons of only sensory neurons: 1. Olfactory (I) 2. Optic (II) 3. Vestibulocochlear (VIII)

Describe the gross anatomy of the spinal nerves.

Two collections of axons connect PNS with spinal cord's gray matter: 1. anterior root consists of motor neurons from anterior horn. 2. posterior root consists of sensory neurons from posterior horn .• Posterior root features a swollen area that houses cell bodies of sensory neurons called posterior root ganglion (or dorsal root ganglion). • Posterior and anterior roots fuse to form spinal nerve just lateral to posterior root ganglion. ▫ All 31 pairs of spinal nerves are mixed nerves.

leak channels

always open; continuously allow ions to flow down concentration gradients between cytosol and ECF

Myelin Sheath

composed of repeating layers of plasma membrane of Schwann cell or oligodendrocyte in PNS and CNS respectively

ependymal cells

ciliated cells that line hollow spaces found within CNS; function to manufacture and circulate cerebrospinal fluid

Major Functions of the Nervous System

controls our perception and experiences of the world;Directs voluntary movement;Seat of consciousness, personality, learning, and memory; Regulates many aspects of homeostasis along with endocrine system: respiratory rate, blood pressure, body temperature, sleep/wake cycle, blood pH

Schwann cells

encircle axons found in PNS to provide them with myelination

Neurons

excitable cell type responsible for sending and receiving signals in form of action potentials

Oligodendrocytes

found in CNS; have radiating processes with flattened sacs that wrap around axons of nearby neurons to form myelin

Microglia

found in CNS; small and scarce cells; activated by injury into wandering phagocytic cells within CNS; ingest disease-causing microorganisms, dead neurons, and cellular debris

Satellite cells

found surrounding cell bodies of neurons in PNS to provide supportive functions

Nodes of Ranvier

gap between adjacent neuroglia; where myelin sheath is absent

ion channels

ions cannot diffuse through lipid component of plasma membrane; must rely on specific protein channels

Describe the location and general function of the cerebellum.

makes up posterior and inferior portion of brain; Heavily involved in planning and coordination of voluntary movement. -Divided into two cerebellar hemispheres connected by vermis. -Ridges called folia cover exterior cerebellar surface. -Separated by shallow sulci

Define excitatory postsynaptic potential (EPSP) and inhibitory postsynaptic potential (IPSP).

membrane potential of postsynaptic neuron moves closer to threshold; caused by a small local depolarization (sodium or calcium channels open) membrane potential of postsynaptic neuron moves farther away from threshold; caused by a small local hyperpolarization ( potassium or chloride ion channels open)

ligand-gated channels

open in response to binding of specific chemical or ligand to a specific receptor

voltage-gated channels

open in response to changes in voltage across membrane

mechanically gated channels

open or close in response to mechanical stimulation (pressure, stretch, or vibration)

Discuss the concept of cerebral lateralization.

phenomenon in which many cognitive functions are unequally represented in right and left hemispheres. Represents a division of labor between hemispheres to maximize a limited amount of brain space.

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

protective safeguard that separates CSF and brain ECF from chemicals and disease-causing organisms sometimes found in blood plasma Consists mainly of simple squamous epithelial cells (endothelial cells) of blood capillaries, their basal laminae, and astrocytes.

Local and Action potentials compared

small local changes in potential of a neuron's plasma membrane; serve as vital triggers for long-distance action potentials; may cause one of two effects:Depolarization-positive charges enter cytosol and make membrane potential less negative( a change from -70 to -60 mV); Hyperpolarization- either positive charges exit or negative charges enter cytosol; makes membrane potential more negative( a change from -70 to -80 mV) uniform, rapid depolarization and repolarization of membrane potential; only generated in trigger zones (incl. axolemma, axon hillock, and initial segment of axon)

Further discuss the anatomy of a spinal nerve to include the relationships between the root, nerve, ramus, and plexus.

• These two mixed nerves carry both somatic motor and sensory information: 1. Posterior ramus - travels to posterior side of body. 2. Anterior ramus - travels to anterior side of body and/or to an upper or lower limb. 3. Anterior root - Carries somatic and visceral motor signals from the CNS to muscles and gland cells 4. Posterior root- carries sensory signals from PNS to spinal cord 5. Spinal nerve- carries visceral/somatic motor, and sensory signals from spinal cord.

Describe the functions of cerebrospinal fluid as well as the details of its production

**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.

circulation of CSF within the CNS, and its ultimate reabsorption into the bloodstream.

**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.

Define each of the two types of memory and provide examples.

*Declarative (fact) memory of things that are readily available to consciousness. Examples - phone number, a literary quote, or pathway of muscle contractions, etc. *Nondeclarative (procedural or skills memory) memory includes skills and associations that are largely unconscious. Examples - how to enter phone number on a phone, how to move your mouth to speak, how to read this chapter, how to tie your shoelaces, etc.

Describe the ventricles of the brain.

*Four ventricles are linked cavities that are continuous with central canal of spinal cord; Lined with ependymal cells; Filled with cerebrospinal fluid *Right and left lateral ventricles (first and second ventricles) Resemble ram's horns when observed in anterior view and horseshoe-shaped appearance in lateral view. *Third ventricle - narrow cavity found between two lobes of diencephalon. connected to lateral ventricles by interventricular foramen. *Fourth ventricle - between pons and cerebellum. connected to third ventricle by cerebral aqueduct (small passageway through midbrain). Continuous with central canal of spinal cord. Contains several posterior openings that allow CSF in ventricles to flow into subarachnoid space.

Briefly describe the three classes of memory (classified by length of time they are stored).

*Immediate memory - stored only for a few seconds. critical for carrying out normal conversation, reading, and daily tasks. *Short-term (working) memory - stored for several minutes. allows you to remember and manipulate information with a general behavioral goal in mind. *Long-term memory - permanent form of storage for days, weeks, or even a lifetime

Identify the areas of the cortex responsible for cognition and language.

*Parietal association cortex - responsible for spatial awareness and attention. - allows us to focus on distinct aspects of a specific object and recognize position of object in space. *Temporal association cortex - primarily responsible for recognizing stimuli, especially complex stimuli such as faces. *Prefrontal cortex - largest and most complex of association cortices.; make up a person's "character" or "personality". Gathers information to create an awareness of "self". Allows for planning and execution of behaviors appropriate for given circumstances.

Describe reflex responses in terms of the major structural and functional components of a reflex arc.

*Reflexes - programmed, automatic responses to stimuli. 1. The PNS detects and delivers a stimulus to the CNS. 2. The CNS integrates the stimulus (makes a decision). 3. The PNS delivers a motor response from the CNS to effectors out in the body.

Explain the differences between the sensory and motor divisions of the peripheral nervous system.

*Sensory division - consists of sensory (afferent) neurons that detect and transmit sensory stimuli to CNS. • It has 2 anatomical subdivisions. *Motor division - consists of motor (efferent) neurons. They carry out motor functions of nervous system. Subdivisions based on organs that neurons contact.

Explain the differences between spinal nerves and cranial nerves.

*Spinal nerves - originate from spinal cord and innervate structures below head and neck. *Cranial nerves - attach to brain and mostly innervate structures in head and neck. • not formed by fusion of sensory and motor roots (like spinal nerves). ▫ allows for purely sensory, mixed, and mostly motor nerves.

Describe the location and general function of the diencephalon. Describe the four components that make up the diencephalon.

- at physical center of brain. • Responsible for processing, integrating, and relaying information to different parts of brain, homeostatic functions, regulation of movement, and biological rhythms. Four Components: *Thalamus - main entry route of sensory data into cerebral cortex. Makes up 80% of diencephalon. -Thalamic nuclei receive afferent fiber froy other regions of nervous system excluding info about the sense of smell. -Regulates cortical activity by controlling which input should continue to cerebral cortex. *Hypothalamus - collection of nuclei anterior and inferior to larger thalamus. -Neurons perform several vital functions critical to survival. -regulation of autonomic nervous system, sleep/wake cycle, thirst and hunger, and body temperature. *Epithalamus - superior to thalamus. -most of its bulk is an endocrine gland called pineal gland that secretes melatonin- a hormone involved in sleep/wake cycle. *Subthalamus - inferior to thalamus. functionally connected with basal nuclei. together, they control movement.

Describe the role of the hypothalamus and the reticular formation of the medulla in maintaining homeostasis of vital functions.

-Reticular formation - controls functions of many internal organs and aspects of behavior. -Hypothalamus - maintains homeostasis largely by relaying instructions to nuclei in reticular formation of medulla; Hypothalamus receives sensory input from viscera, components of the limbic system, and the cerebral cortex. Allows to respond to both normal physiological changes and emotional changes and to adjust ANS output to maintain homeostasis. **regulates body temp, blood pressure, feeding

Describe the concept of dermatomes, and explain why they are clinically significant in terms of referred pain.

-Skin can be divided into different segments based on spinal nerve that supplies region with somatic sensation. ▫ Dermatomes can be combined to assemble a dermatome map. ▫ It represents all (except first cervical spinal nerve) of sensory pathways to different parts of body. ▫ Dermatome maps can be used clinically to test integrity of sensory pathway to different parts of body -Referred pain is generally located along a dermatome for a particular nerve.

Describe the four major categories of neurotransmitters.

1. Acetylcholine (ACh) - small molecule neurotransmitter used by nervous system. ◦ Cholinergic synapses bind to Ach. ◦ found in neuromuscular junction, within brain, spinal cord and autonomic nervous system. ◦ Largely excitatory ◦ Synthesized from choline and acetyl-CoA; packed into synaptic vesicles. ◦ Quickly degraded by acetylcholinesterase (AChE) 2. Biogenic amines (monoamines) are a class of fiveneurotransmitters synthesized from amino acids. • used throughout CNS and PNS for functions likeregulation of homeostasis and cognition. • Three form catecholamine subgroup, all are made from amino acid tyrosine (mostly excitatory). a) Norepinephrine is found in ANS where it influences heart rate, blood pressure, and digestion; in CNS it regulates sleep/wake cycle, attention, and feeding behaviors. b) Epinephrine (catecholamine, adrenalin) used in ANS and similar functions as norepinephrine.◦ widely used as a hormone by endocrine system. c) Dopamine (catecholamine) - used by CNS to help coordinate movement. ◦ involved in emotion and motivation. d) Serotonin - synthesized from tryptophan where most serotonin-secreting neurons found in brainstem and axons project into areas of brain. ◦ mood regulation, emotions, attention, feeding behaviors, and daily rhythms. e) Histamine - synthesized from histidine. *regulation of arousal and attention. 3. Amino acid neurotransmitters: ◦ Glutamate - important excitatory neurotransmitter in CNS. ◦ binds to ionotropic postsynaptic receptors and opens channels that allow for flow of sodium and calcium ions which generate EPSPs in postsynaptic neuron. ◦ Glycine and GABA - major inhibitory neurotransmitters. ◦ induce IPSPs on postsynaptic neurons by opening chloride ion channels that hyperpolarize the axolemma. 4. Neuropeptides - group of neurotransmitters with variety of functions in nervous system. ◦ must be synthesized in cell body and transported to axon. ◦ Substance P - released from type C sensory afferents that carry information about pain and temperature. * released by other neurons in brain, spinal cord, and gut. ◦ Opioids - group of more than 20 neuropeptides that include endorphins, enkephalins, and dynorphins, all elicit pain relief and are nervous system depressants. ◦ Neuropeptide Y - neuropeptide involved in feeding behaviors

Describe the events of chemical synaptic transmission in chronological order.

1. An action potential in presynaptic neuron triggers voltage-gated calcium ion channels in axon terminal to open. 2. Influx of calcium ions causes synaptic vesicles to release neurotransmitter into synaptic cleft by exocytosis. 3. Neurotransmitters bind to receptors on postsynaptic neuron. 4. Ion channels open, leading to a local potential and possibly an action potential, if threshold is reached.

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

1. Frontal lobes - most anterior lobes. Neurons responsible for planning/executing movement and complex mental functions such as behavior, conscience, and personality. 2. Parietal lobes - just posterior to frontal lobes. Neurons responsible for processing/integrating sensory information and function in attention. 3. Temporal lobes - form lateral surfaces of each cerebral hemisphere.Neurons involved in hearing, language, memory, and emotions. 4. Occipital lobes - make up posterior aspect of each cerebral hemisphere. Neurons process all information related to vision. 5. Insulas - deep underneath lateral fissures. Neurons currently thought to be involved in functions related to taste and viscera (internal organs).

Describe each of the following types of receptors, indicating what sensation it detects and giving an example of where it can be found in the body: mechanoreceptors, thermoreceptors, chemoreceptors, photoreceptors and nociceptors.

1. Mechanoreceptors - encapsulated interoceptors or exteroceptors found in musculoskeletal system, skin, and in many other organs; mechanically gated ion channels allow for sensory transduction from vibration, light touch, stretch, and pressure. 2. Thermoreceptors - exteroceptors that depolarize in response to temperature changes; separate receptors detect hot and cold 3. Chemoreceptors - can be either interoceptors or exteroceptors that depolarize in response to binding to specific chemicals (in body fluids or in air). They generate a receptor potential as sodium ion channels open. 4. Photoreceptors - special sensory exteroceptors found only in eye; depolarize in response to light. 5. Nociceptors - usually slowly adapting exteroceptors that depolarize in response to noxious (harmful, poisonous, or very unpleasant) stimuli that damage the body's integrity. aka- pain receptors.

Motor cranial nerves

Five cranial nerves contain primarily axons of motor neurons with their associated sensory axons responsible for proprioception: 1. Oculomotor (III) 2. Trochlear (IV) 3. Abducens (VI) 4. Accessory (XI) 5. Hypoglossal (XII)

Briefly describe the six classes of mechanoreceptors

1. Merkel cell fibers- slowly adapting nerve ending surrounded by a capsule of Merkel cells. ▫ Found in epidermal ridges, primarily in skin of hands (especially fingertips). 2. Tactile corpuscles) - in dermal papillae. rapidly adapting tactile exteroceptors; transmit discriminative touch stimuli. (objects form and texture) 3. Ruffini endings (bulbous corpuscles) - spindle shaped receptors found in dermis, hypodermic, and ligaments. slowly adapting receptors respond to stretch and movement. 4. Lamellate corpuscles (Pacinian corpuscles) - layered onion-shaped appearance; rapidly adapting receptors found deep within dermis. detect high-frequency vibratory and deep pressure stimuli. 5. Hair follicle receptors - free nerve endings surrounding base of hair follicles found in thin skin. respond to stimuli that cause hair to bend. 6. Proprioceptors - in musculoskeletal system. detect movement and position of a joint or body part.

Identify the cranial nerves by name and number, classify each as sensory, motor, or mixed and describe the specific functions of each pair of cranial nerves.

1. Olfactory- sense of smell 2. Optic- Nerve for vision 3.Vestibulocochlear- hearing, balance,equilibrium 4. Oculomotor- pupil, eye movement around, 5. Trochlear- Move eye medially, inferiorly 6. Abducens- moves eye laterally 7. Accessory- Muscles 4 speech, head shoulder movement 8. Hypoglossal nerve- innervates muscle of tongue, no role in taste 9. Trigeminal- facial sensation, mastication and swallowing, 10. Facial- Taste sensation, somatic sensation from eye, palate, nasal cavity; fascial expression 11. Glossopharyngeal- Detect changes in blood pressure, swallowing movements 12. Vagus- detect blood CO2, taste sensation from the pharynx, speaking and swallowing.

Describe a simple stretch reflex, a golgi tendon reflex, a flexion reflex, a crossed-extension reflex, and the two cranial nerve reflexes (gag and corneal blink).

1. Simple stretch reflex ▫ Body's reflexive response to stretching of muscle to shorten it back to within its "set" optimal length. ex: Patellar (knee-jerk) reflex and jaw-jerk reflex 2. Golgi tendon reflexes - polysynaptic reflexes. ▫ protect muscles and tendons from damaging forces. ▫ Causes muscle relaxation; 3. Flexion (withdrawal) • Involves rapidly conducting nociceptive afferents and multiple synapses in spinal cord. • act to withdraw limb from painful stimuli. 4. Crossed-extension spinal reflex • Occurs simultaneously on opposite side of body for balance and postural support while other limb is withdrawn from a painful stimulus. 5. Gag reflex-triggered when visceral sensory nerve endings of glossopharyngeal nerve in posterior throat are stimulated. 6. Corneal blink reflex - triggered when a stimulus reaches somatic sensory receptors of trigeminal nerve in thin outer covering of eye (cornea). something contacts eye leading to a blink response.

Subdivisions of the visceral motor division.

1. Sympathetic nervous system (fight or flight division) - involved in homeostasis activities surrounding physical work and visceral responses of emotions and stress. 2. Parasympathetic system (rest and digest division) - involved in digestion and maintaining body's homeostasis at rest.

List the number of spinal nerves detailing how many pairs are in each category. List the four spinal nerve plexuses.

31 pairs of spinal nerves: ▫ 8 pairs of cervical nerves ▫ 12 pairs of thoracic nerves ▫ 5 pairs of lumbar and sacral nerves ▫ 1 pair of coccygeal nerves 1. Cervical Plexus 2. Brachial Plexus 3. Lumbar Plexus 4. Sacral Plexus

structures of the central nervous system

Brain- made up of billions of nerve cells or neurons; protected by bones of skull Spinal Cord- begins at foramen magnum and continues through vertebral foramina of first cervical to first or second lumbar vertebra; made up of millions of neurons; enables brain to communicate with most of body below head and neck

Structure of a neuron

Cell body (soma)- most metabolically active region of neuron; manufactures all proteins needed for whole neuron; the following organelles support this high level of biosynthetic activity; both free ribosomes and rough endoplasmic reticulum for protein synthesis; Nissl bodies are RER that can be seen with microscope; Golgi apparatus and large or multiple nucleoli; mitochondria supply energy required for high metabolic Cytoskeleton- contains microtubules; provide structural support and a means for chemical transportation between cell body and axon Neurofibrils- composed of intermediate filaments of cytoskeleton; provide structural support that extends into neuron processes Processes- cytoplasmic extensions that originate at cell body and include dendrites and axons; allow neurons to communicate with other cells Dendrites- short, branched processes; receive input from other neurons, which they transmit to toward cell body in form of electrical impulses; each neuron may have multiple dendrites Each neuron has only one axon or nerve fiber that can generate and conduct action potentials; axon may have following distinct regions Axon hillock- region where axon originates from cell body Axon collaterals- branches that extend from main axon Telodendria- small branches that arise from axon and axon collaterals near where these extensions end Axon terminals or synaptic bulbs- arise from telodendria; components that communicate with a target cell Axolemma- plasma membrane that surrounded axon and its cytoplasm or axoplasm

Mixed Cranial nerves

Four cranial nerves contain axons of both sensory and motor neurons: 1. Trigeminal (V) 2. Facial (VII) 3. Glossopharyngeal (IX) 4. Vagus (X)

sensory function of nervous system

Gather information about internal and external environments of body; input is gathered by sensory or afferent division of PNS; further divided into somatic and visceral divisions; sensory input from both divisions is carried from sensory receptors to spinal cord and/or brain by spinal and cranial nerves Somatic- consists of neurons that carry signals from skeletal muscles, bones, joints, and skin; also transmits signals from organs of vision, hearing, taste, smell, and balance; sometimes called special sensory division Visceral- consists of neurons that transmits signals form viscera (organs) such as heart, lungs, stomach, kidneys, and urinary bladder

Identify and describe the cranial meninges and explain their functional relationship to the brain.

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.

Differentiate between the somatic and visceral divisions of the nervous system

a) Somatic sensory division detects both internal and external stimuli. -general sense receptors detect stimuli from skin. -special sensory receptors detect stimuli from special sense organs. b) Visceral sensory division relays internal information (like blood pressure) from organs (viscera) of abdominopelvic and thoracic cavities. a) Somatic motor division - responsible for voluntary motor functions; composed of lower motor neurons (somatic motor neurons) which directly trigger skeletal muscle contractions. b) 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.

motor function of nervous system

actions performed in response to integration; performed by motor or efferent division of PNS; can be further subdivided into somatic and autonomic divisions, based on organs that neurons contact Motor/efferent- consists of motor neurons that carry out motor functions; travel from brain and spinal cord via cranial and spinal nerves; organs that carry out effects of nervous system are commonly called effectors Somatic- consists of neurons that transmit signals to skeletal muscle, under voluntary control( aka voluntary motor division) Autonomic nervous system (ANS) or visceral- consists of neurons that carry signals to thoracic and abdominal viscera; critical for maintaining homeostasis of body's internal environment; regulates secretion of certain glands, contraction of smooth muscle, and contraction of cardiac muscle in heart; involuntary( aka involuntary motor division)

Integrative function of the nervous system

analyze and interpret incoming sensory information and determine an appropriate response; 99% of integrated sensory information is subconsciously disregarded as unimportant; remaining sensory stimuli that CNS does respond to generally leads to a motor response

Describe the composition and function of the spinal cord.

composed primarily of nervous tissue. Responsible for both relaying and processing information. -Serves as a relay station and as an intermediate point between body and brain; only means by which brain can interact with body below head and neck. -Processing station for some less complex activities such as spinal reflexes.

Describe the location and general function of the brainstem. Briefly describe the three subdivisions of the brainstem. Describe the reticular formation.

connects brain to spinal cord. -Vitat survival as its nuclei control many basic homeostatic functions such as heart rate and breathing rhythms. -Controls many reflexes (programmed, automatic responses to stimuli);functions in movement, sensation, and maintaining alertness. *Three subdivisions: 1. Midbrain -Inferior to diencephalon. surrounds cerebral aqueduct; Process and routes stimuli to thalamus; Carries motor fibers from cerebral cortex; Monitors movement with basal nuclei. 2. Pons -Inferior to midbrain. Regulates breathing, reflexes and the sleep/wake cycle. 3. Medulla oblongata - most inferior structure of brainstem and is continuous with spinal cord at foramen magnum. Contains tracts of white matter involved in movement and sensation; Regulates many homeostatic functions.

structures of the peripheral nervous system

consists of all nerves in body outside protection of skull and vertebral column; nerves consist of axons of neurons bundled together with blood vessels and connective tissue; carry signals to and from CNS; classified based on origin or destination 12 pairs of nerves traveling back to or from brain-cranial nerves 31 pairs of nerves traveling back to or from spinal cord-spinal nerves

Astrocytes

found in CNS;large, star-shaped glial cells, whose many processes terminate in structures called end-feet; function to: Anchor neurons and blood vessels in place; help define and maintain 3-D structure of brain; facilitate transport of nutrients and gases between blood vessels and neurons; regulate extracellular environment of brain; assist in formation of blood-brain barrier; protective structure that surrounds capillary endothelial cells and makes them impenetrable to most polar compounds and proteins; repair damaged brain tissue by rapid cell division

Describe the location and functions of the 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.

Differentiate between gray matter and white matter in the brain and spinal cord.

in brain and spinal cord; consists of neuron cell bodies, dendrites, and unmyelinated axons. -Outer millimeters (cortex) of cerebrum is gray matter. deeper portions of brain are mostly white matter with some gray matter scattered throughout. -Spinal cord is mostly gray matter that processes information (butterfly in cord center) and surrounded by tracts of white matter (outside). Relays information to and from brain found in brain and spinal cord; consists of myelinated axons. - Spinal white matter is superficial in the spinal cord while it is deep in brain.

continuous and saltatory conduction

in unmyelinated axons where every section of axolemma from trigger zone to axon terminal must propagate an action potential.◦ slows conduction speed as each successive section of axon must depolarize. occur in myelinated axons where insulating properties of myelin sheath increase efficiency and speed of signal conduction.◦ action potentials only depolarize nodes of Ranvier and "jump over" internodes.

Neurotransmitters and its receptors

made in cell body or axon terminal and packaged into synaptic vesicles; released from axon terminals of presynaptic neurons; cross synaptic cleft; bind to specific receptors on postsynaptic membrane; effects are often rapidly terminated through removal and/or degradation binding leads to either an EPSP or an IPSP; most can have both effects depending on which postsynaptic neuron receptors they bind; single one may have several receptor types

Myelination

process that forms myelin sheath from plasma membrane of neuroglial cells; wrap themselves around axon forming multiple layers of membrane; electric current-generated by movement of ions in body fluids; lipid content of myelin sheath insulates axon like rubber around copper wire; increases speed of action potential conduction; myelinated axons conduct action potentials about 15-20 times faster than unmyelinated axons Neurolemma- found on outer surface of a myelinated axon in PNS; composed of Schwann cells nucleus, organelles, and cytoplasm; not present in CNS Number of axons myelinated- oligodendrocytes have multiple processes that can provide myelination for multiple axons in CNS while a schwann cell only provides myelination for one axon in PNS Timing of myelination- begins early in fetal development in PNS and much later in the CNS; very little myelin present in brain of newborn

list three ways synaptic transmission is terminated

some neurotransmitters diffuse away from synaptic cleft in ECF; can be reabsorbed into a neuron or an astrocyte Neurotransmitter can be broken down in synaptic cleft by enzymes; by-products of reaction can be reabsorbed by presynaptic membrane for reassembly of original neurotransmitter some neurotransmitters are reabsorbed into presynaptic neuron by a process called reuptake

Describe the function of the cerebrum and its overall structure.

structure responsible for higher mental functions, interpretation of sensory stimuli and initiates movement. Gross anatomical features of cerebrum include: -Sulci - shallow grooves on surface of cerebrum. -Gyri - elevated ridges found between sulci They increase surface area of brain yet, maximizing limited space within confines of skull.

resting membrane potential

voltage present when a cell is at rest Voltage- electrical gradient established by separation of charge between two locations, in this case across plasma membrane Membrane Potential- electrical potential across cell membrane; source of potential energy for cell Cell is polarized when voltage difference across plasma membrane does not equal 0 mV; typical neuron has a resting potential of -70 mV