Chapter 12 CNS & Chapter 13 PNS

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<p>How is the brain protected and what are the functions of meninges, CSF, and blood brain barrier (BBB)?</p>

How is the brain protected and what are the functions of meninges, CSF, and blood brain barrier (BBB)?

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<p>How is the brain protected and what are the functions of meninges, CSF, and blood brain barrier (BBB)?</p>

How is the brain protected and what are the functions of meninges, CSF, and blood brain barrier (BBB)?

Skull

Meninges = membranes; connective tissue membranes, external to CNS organs

Functions:

  • Cover & protect CNS

  • Protect blood vessels and enclose venous sinuses

  • Contains CSF

  • Form partitions in the skull

Cerebrospinal fluid = water cushion

  • clear fluid

  • found in around the brain and spinal cord & protects from trauma and blows

  • Forms a liquid cushion around the CNS structures

    • Prevents the brain from crushing under its own weight

    • Carries nutrients

Blood-brain barrier = protects the brain from harmful substances

  • Brain is reliant on a constant internal environment

  • Consists of tight junctions between capillary endothelial cells

  • Functions:

    • Maintains homeostasis in brain

    • Selectively filters wanted & unwanted nutrients between the brain’s capillaries and the brain

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<p>What neuroglia assist the Blood Brain Barrier and how does BBB work (fig 12.26).</p>

What neuroglia assist the Blood Brain Barrier and how does BBB work (fig 12.26).

Astrocytes cling to each capillary and provide structural support for neurons.

BBB - is the protective mechanism that helps maintain the brain’s stable environment

  • Impermeable tight junctions between capillary endothelial cells are its major component

  • Pericytes - surrounding the endothelial cells are the bulbous feet of astrocytes and smooth muscle

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<p>What is white and gray brain matter?</p>

What is white and gray brain matter?

White - consists mostly of myelinated axons with some nonmyelinated axons primarily in fiber tracts. The dense coating of fatty myelin is what gives white matter its color

Gray - consists of short, nonmyelinated neurons & neuron cell bodies

  • The spinal cord exhibits this basic pattern. Charges with ascent into the brain stem

  • The brain stem has additional gray matter nuclei scattered within the white matter

  • The cerebral hemispheres and the cerebellum have an outer layer or “bark'“of gray matter called a cortex

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<p>What are five major divisions of the brain?</p>

What are five major divisions of the brain?

Telencephalon - the largest division of the brain

  • Contains the cerebrum, which constitutes 2/3 of the brain’s mass

  • Also includes the olfactory and optic cranial nerves

Diencephalon - relays sensory information and connects the endocrine system with the nervous system

  • Regulates functions such as autonomic control, endocrine signaling, and sensory perception

Mesencephalon (midbrain)

  • Sits between the forebrain & hindbrain

  • Essential for visual and auditory processing

  • Involved in reflexive movements, such as turning toward a sudden sound

Metencephalon (afterbrain)

  • Contains the pons & the cerebellum

  • Pons: Connects different brain regions & help regulate breathing

  • Cerebellum: Coordinates motor movements, balance, and posture

Myelencephalon (hindbrain) (spinal brain)

  • Includes the medulla oblongata

  • Vital for autonomic functions like heart rate, breathing, and blood pressure regulation

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<p>What are gyri, sulci and fissures?</p>

What are gyri, sulci and fissures?

Gyri (plural)

  • twisters

  • Elevated ridges of tissue

Sulci (plural)

  • furrows

  • shallow grooves

Fissures

  • Deeper grooves

  • Separate deeper regions of the brain

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<p>What are longitudinal and transverse fissures?</p>

What are longitudinal and transverse fissures?

Longitudinal fissure - separates left & right hemispheres

Transverse cerebral fissure - separates cerebral hemispheres from cerebellum

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<p>What<span>&nbsp;</span>five lobes of cerebrum and what is each major functions?</p>

What five lobes of cerebrum and what is each major functions?

Frontal - smell, voluntary motor function, motivation, aggression, and mood

Parietal - Receive general sensory input, taste, and balance

Occipital - visual centers

Temporal - receive olfactory & auditory input, involved with memory, abstract thought, and judgement

Insula - deep to portions of the temporal, parietal, and frontal lobes

  • island - located deep within the tissue separating the temporal lobes from the others

  • Most lobes are named for the cranial ones that cover them

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<p>What/where is the cerebral cortex, and how is it organized/structured? </p>

What/where is the cerebral cortex, and how is it organized/structured?

is the executive suite of the nervous system, where our conscious mind is found

  • Composed of gray matter

  • “Higher order” functions

    • Self-awareness, communication, memory, understanding, voluntary movements

  • 3 functional areas:

    • Motor

    • Sensory

    • Association

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What does each of the three subsections of the cortex do?

White matter

*Mostly myelinated axons with some nonmyelinated axons

Basal nuclei = clusters of cell bodies

  • Neuron cell bodies

  • Short nonmyelinated neurons

Ventricles – filled with CSF, lined with ependymal cells nonmyelinated

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<p>What are Boca’s and Wernicke’s areas of brain?</p>

What are Boca’s and Wernicke’s areas of brain?

Boca’s Area

  • Usually only present in left hemisphere

  • Special “motor speech area”

Wernicke’s Area

  • Speech word bank

    • Direct muscles involved with speech production

      • Active when we prepared to speak and even as we think about (plan) many voluntary motor activities other than speech

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What is the motor somatotopy and why is this important?

Somatotopy - spatial representation & mapping of the entire body

  • Homunculus - is used to show the broad areas of the primary cortex

  • Most precise motor control - face, tongues, & hands & consequently those areas are the largest, represented by their size on the homunculus

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What is the somatosensory cortex of brain and how is it organized?

  • Integrates & creates an understanding of sensory input

    • Temperature, pressure so forth from the primary somatosensory cortex to produce an understanding of an object being felt-size texture, etc

  • Understanding is based on learned/past experiences

    • Know without seeing; know what we feel

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List and define the 12 Sensory areas of the Cortex?

1) Primary visual cortex (V1) - located in the occipital lobe, responsible for processing visual information

  • largest areas of all retinal images, focal images

2) Secondary visual cortex (V2, V3, V4, V5/MT)

  • located in the occipital lobe, responsible for higher-level visual processing

3) Primary auditory cortex - located in the temporal lobe, responsible for processing auditory information

  • pitch, loudness, location in 3D space

4) Somatosensory cortex - located in the frontal lobe

  • integrates senses of temperature, touch, pressure, size, and texture, (know without seeing; know what we feel)

5) Primary motor cortex - located in the frontal lobe, responsible for controlling voluntary movements

  • precise, skilled motions                                                                         

6) Premotor cortex - located in the frontal lobe, involved in planning and coordinating complex movements

  • learned, repetitive motor skills

7) Supplementary motor area - located in the frontal lobe, involved in the preparation and initiation of voluntary movements

8) Gustatory cortex - located in the parietal lobe, responsible for processing taste information

  • perception of taste, located in the insula

9) Olfactory cortex -

  • sense of smell

10) Vestibular cortex - Equilibrium; a position sense of where your head is in space

  • located in the parietal lobe, responsible for processing information about balance and spatial orientation

11) Insular cortex - located in the temporal lobe, involved in processing interoceptive

12) Posterior parietal cortex - located in the parietal lobe, involved in integrating sensory information and spatial awareness

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What occurs in the multimodal, anterior, posterior, limbic areas of cerebrum?

Multimodal - allows us to give meaning and content to what is experienced; where thoughts and emotions become “real” to us; and we store it in memory. It is our collective personality.

a. Anterior Association area (prefrontal cortex) – intellect, complex reasoning, ideas, judgement, planning

b. Posterior Association Area – recognizing patterns & shapes, where we are in the big “picture”

c. Limbic Association area – provides the emotional impact of events to us

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Define lateralization, contra lateralization and cerebral dominance?

Lateralization - we use both cerebral hemispheres for almost every activity, and the hemispheres appear nearly identical.

  • Nonetheless, there is a division of labor, and each hemisphere has abilities not completely shared by its partner.

Contra laterilization - property that the hemispheres of the cerebrum and the thalamus represent mainly the contralateral side of the body

Cerebral hemisphere - "dominates" each task and designates the hemisphere that is dominant for language.

  • In most people (about 90% ), the left hemisphere has greater control over language abilities, math, and logic

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<p>What do the ‘Fibers” of the cerebral white matter do?</p>

What do the ‘Fibers” of the cerebral white matter do?

  • Located deep to cortical gray layer

  • Responsible for communication between cortex and lower CNS centers

  • Consists of myelinated fiber tracts:

    • Commissures: connect corresponding gray areas of different hemispheres

    • Association fibers: connect different parts of the same hemisphere

    • Projection fibers: tie the cortex to the rest of the nervous system/body

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What does basal ganglia do?

Basal Ganglia

  • Located deep within white matter

  • Starting, stopping, and regulating the intensity of movements executed by the cortex

    • Act as “filters” for incorrect/inappropriate responses

    • Disorders of the basal nuclei may result in increases or decreased movement

      • i.e. Parkinson’s Disease

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What structures comprise the diencephalon and what do they govern?

  • Located between the brainstem and the cerebrum

Thalamus

  • Greek = “inner room”

  • Acts as a relay center for information between the cortex and the rest of the body

    • Edits and sorts out information

    • Mediates sensory, motor, and cognitive functions

    • “the gateway to the cortex”

Hypothalamus

  • Visceral control center

  • Regulation of homeostasis

  • Heart rate, blood pressure, digestive function, pupils (ANS)

  • Regulates emotion in conjunction with limbic system

  • Sleep wake-cycles

  • Body temperature

    • Located ‘below’ the thalamus

    • Vitally important to homeostasis

Epithalamus

  • Pineal gland

  • Secretes melatonin

    • Assists hypothalamus with sleep-wake cycle

    • Melatonin is a hormone that serves as a sleep-inducing signal and antioxidant

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What structures comprise the brain stem and what are their functions?

Midbrain

  • Conduction pathway between higher and lower brain centers

  • Cerebral peduncles

    • Major descending motor pathway

    • Lies between the diencephalon and the pons

Pons

  • Conduction pathway between higher and lower center

  • Regulates:        

    • Respiration

    • Communication/connects between cerebrum and cerebellum

Medulla oblongata

  • Sensory impulses from skin & proprioceptors

  • Heart rate

  • Vessel diameter

  • Respiratory rate

Hypothalamus and Medulla have a lot of overlap. Hypothalamus controls the functions by relaying the messages to the medulla oblongata which carry it out.

  • CV Center- adjusts the force and rate of heart contraction, vasodilation

  • Respiratory rhythm, rate, and depth

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What is function of the cerebellum?

  • Coordination between gross and fine motor tasks

  • Provide instructions to motor cortex

  • Balance

  • Capable of learning complex motor activities

    • Provides instructions to cerebral motor cortex, resulting in smooth coordinated skeletal muscle movements

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How does cerebellum processing work?

1. Cerebellum receives impulses (notifications of “intent” from cortex)

2. Proprioceptors & visual signals inform cerebellum of body’s positioning

3. Cerebellum decides proper movement and calculates the best way to coordinate the force, direction, and extent of the muscle contraction

4. Sends plan (blueprint) to cerebral motor area for execution

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What is the limbic system and what does it do?

is a group of structures located on the medial aspect of each cerebral hemisphere and diencephalon. Its cerebral structures encircle (limbus=ring) the upper part of the brain stem.

Functions:

Emotion Regulation: it helps regulate emotions and behaviors, managing how we feel and respond to certain situations or stimuli

Behaviors: They influence our behavior and motivation, often in response to emotional stimuli

Memory: It plays a key role in forming new memories, particularly those tied to emotions

Autonomic Nervous System: it interacts with the autonomic nervous system, affecting physiological responses like heart rate, blood pressure, & digestion

Higher Mental Functions: the limbic system works with other brain regions to support higher mental functions like learning, speech, and decision-making

Involved in..

Hippocampus - involved in memory

formation and spatial navigation

Amygdala - responsible for emotional responses, fear, and aggression

Thalamus - relays sensory information from the top down to the correct brain regions

Hypothalamus - regulates hunger, thirst, body temperature, and other autonomic functions

Cingulate gyrus - associated with emotional processing & decision-making

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What is reticular formation and what does it do?

is a neuron network in the brainstem that enables communication, sensory, & motor function, and endocrine & neurotransmitter regulation

Includes 2 main systems:

(ARAS) - Ascending Reticular Activating System - This system sends sensory signals to the cortex, affecting alertness and wakefulness.

(DRS) - Descending Reticular System - this sytem sends signals to the motor neurons of the spinal cord & can influence muscle tone & reflexes

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What are declarative memory, procedural memory, emotional memory and motor memory?

Declarative memory - (fact) (explicit memory) names faces, words, and dates

Procedural memory - (skills) (piano playing)

Motor memory - riding a bike (motor skills)

Emotional memory - pounding heart/emotional memories are closely tied to our feelings & emotions

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What influences our ability to move topics from short term to long term memory?

Short-term memory (STM) - working memory is the preliminary step of looking at a phone number and never thinking about it again

Long-term memory (LTM) - seems to have limitless capacity. Long-term can be forgotten, and so our memory bank continually changes over time.

What influences our ability is…

  • Emotional state: We learn best when we are alert, motivated, surprised, or aroused

  • Rehearsal - rehearsing or repeating the material enhances memory

  • Association- tying “new” info to “old” information already stored in LTM appears to be important in remembering formed

  • Automatic memory - not all impressions that become part of LTM are consciously formed

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What is consciousness? How is EEG related to consciousness in terms of alpha, beta, theta, delta waves?

encompasses perception of sensations, voluntary initiation and control of movement, and capabilities associated with higher mental processing (memory, logic, judgement, and so on).

  • Brainwaves are electrical oscillations produced by the synchronized activity of neurons in the brain.

  • EEG measures the frequency (cycles per second or hertz) and amplitude (strength) or brainwaves.

    • Alpha - awake & resting (8-13 Hz)

    • Beta - mental activity (14-30 Hz)

    • Theta - emotional stress (4-7 Hz)

    • Delta - deep sleep (4 Hz or less)

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How is sleep regulated? What is the importance of sleep?

2 major types of sleep:

non-REM (NREM) - NREM sleep is essential for physical restoration, tissue repair, and immune system function.

REM (rapid eye movement) - REM sleep is crucial for cognitive processes, memory consolidation, and emotional regulation.

Circadian Rhythm: Sleep is regulated by our circadian rhythm, which is like an internal clock that influences when we feel sleepy or alert.

The importance of sleep is …

  • During sleep, we may consolidate new memories and discard memories that are no longer accessed (in other words, we forget).

  • Sleep is presumed to be a restorative time when most neural activity can wind down to basal levels.

  • When deprived of sleep, we spend more time than usual in both REM and slow-wave sleep during the next sleep episode in an attempt to catch up.

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Define the cross-sectional anatomy of the spinal cord and its anterior/posterior spinal horns?

The spinal cord is somewhat flattened from front to back & two grooves mark its surface: the wide ventral (anterior) median fissure and the narrower dorsal (posterior) median sulcus

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Where does CNS end and PNS begin within the spinal column?

CNS and the PNS within the spinal column is at the point where the spinal nerves exit the spinal cord.

  • The spinal cord itself ends at about the first or second lumbar vertebra (L1-L2) in adults, but the nerves continue to extend down the vertebral column forming the cauda equina.

  • The CNS ends and the PNS begins at the intervertebral foramina, where the nerve roots exit the spinal cord and extend out to the body

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How is gray matter in spinal cord organized?

  • Connects brain and peripheral nervous system (PNS)

  • Enclosed in the vertebral column

  • Two-way conduction pathway to and from the brain

Gray matter

  • “H” or “butterfly” shape

  • Dorsal projections = dorsal (posterior) horns

  • Ventral projections = ventral (anterior) horns

  • Forms columns; running the entire length of the cord

  • Generally

    • Dorsal horns = sensory function

    • Ventral horns = motor function

  • Dorsal root & dorsal ganglion (enlarged area)

    • Serve as sensory afferent

  • Ventral root and ventral ganglion

    • Serve as motor efferent

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What is paraplegia, quadriplegia? 

Paraplegia - transection of the spinal cord between T1 and L1 (Thoracic vertebra)
- paralysis of the legs and lower body, typically caused by spinal injury or disease.

Quadriplegia - transection of spinal cord in the cervical region

  • paralysis of all four limbs

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What is decussation, relay, somatotopy?

Decussation - Most pathways cross from one side of the CNS to the other (decussate) at some point along their journey

Relay - most pathways consist of a chain of two or three neurons (a relay) that contribute to successive tracts of the pathway

Somatotopy - most pathways exhibit somatotopy, a precise spatial relationship among the tract fibers that reflects the orderly mapping of the body

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What do 1st, 2nd and 3rd order neurons do in the ascending pathway?

First-order neurons

  • Impulses from cutaneous receptors and proprioceptors

    • dorsal root ganglion

Second-order neurons

  • Form dorsal horn —> thalamus

Third-order neurons

  • Relay impulses from thalamus to somatosensory cortex

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In general what do the “tracks” in the spinal cord represent (12.3 table)?

These tracts carry sensory information & motor stimuli from the periphery (body) to the brain.

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CHP 13


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Know the classification of receptors by stimulus type and location; this includes mechanoreceptors, thermoreceptors, photoreceptors, chemoreceptors, nociceptors, exteroceptors, interoceptors., proprioceptors

Mechanoreceptors - respond to touch, pressure, vibration, stretch, tension, and itch

Thermoreceptors - temperature

Photoreceptors - photo

Chemoreceptors - chemicals

Nociceptors - pain

Exteroceptors - sensitive to stimuli arising outside the body

  • touch, pressure, pain, temperature receptors of skin & most receptors of sense organs

Interceptors - respond to stimuli arising within the body

  • chemical changes, stretching of tissues & temperature

Proprioceptors - Respond to internal stimuli expect their location is restricted to musculoskeletal organs

  • Provide the brain information to location of body in space (kinesthetic awareness)

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Know the location and functions of: tactile receptors, muscle spindles, tendon organs,  joint kinesthesia receptors

Tactile receptors -

  • Functions: mechanoreceptors

  • Location: exteroceptors; fingertips, feet, and eyelids

Muscle spindles -

  • Functions: mechanoreceptors; muscle stretch, and length

  • Location: proprioceptors; skeletal muscles

Tendon organs

  • Functions: Mechanoreceptors (tendon, stretch, tension

  • Location: proprioceptors, tendons

Joint kinesthesia receptors -

  • Functions: Mechanoreceptors & nociceptors

  • Location: joint capsules of synovial joints

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What is the somatosensory system and its functions?

A part of the sensory system serving the body wall and limbs — receives inputs from exteroceptors, proprioceptors and interceptors

Functions:

Touch - this include the perception of pressure, vibration, and texture

Temperature - the system detects variations in temperature (thermoception)

Pain - it processes nociceptive signals which are essential for avoiding injury

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What are the three main levels of the somatosensory system and how does each work.

Receptor level: sensory receptors

  • For sensation to occur, a stimulus must excite a receptor, and action potential must reach the CNS

Circuit level: processing in ascending pathways

  • the task is to deliver impulses to the appropriate region of the cerebral cortex for localization and perception of the stimulus

Perceptual level: processing in cortical sensory areas

  • the ability to identify and appreciate sensations depends on the location of the target neurons in the sensory cortex, not on the nature of the message

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What is encoding/transduction?

Encoding - refers to the initial step in creating a memory. It involves transforming sensory input from the environment into a form that can be stored in the memory system

Transduction - describes the conversion of physical signals from the environment into neural signals that are sent to the CNS

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What is neuronal adaptation?

Gradual decrease over time in the responsiveness of the sensory system to a constant stimulus

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What is perceptual detection?

Perceptual detection - is the ability to detect that a stimulus has occurred. This is the simplest level of perception. As a general rule, inputs from several receptors must be summed for perceptual detection to occur.

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What is magnitude estimation?

Magnitude estimation - is the ability to detect how intense the stimulus is. Perceived intensity increases as stimulus intensity increases because of frequency coding

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What is spatial discrimination?

Spatial discrimination - allows us to identify the site or pattern of stimulation

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What is feature abstraction?

Feature abstraction - is the mechanism by which a neuron or circuit is tuned to one feature, or property of a stimulus in preference to others

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What is quality discrimination?

is the ability to differentiate the sub modalities of a particular sensation

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What is pattern recognition?

is the ability to take in the scene around us & recognize a familiar pattern, an unfamiliar one, or one that has special significance for us

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What roles do substances p, histamine, glutamate, endorphins, and enkephalins have in pain sensations?

Substance p - is a neuropeptide involved in regulating nociception (pain sensation) in the body

  • it acts as a sensory neurotransmitter in the spinal cord interneurons, resulting in the suppression of pain

Histamine - is a chemical mediator released during allergic reactions & inflammation

  • it plays a role in pain by sensitizing nerve endings and increasing their responsiveness to other pain signals

Glutamate - is a major excitatory neurotransmitter in the CNS

Endorphins - are endogenous opioids produced by the body

  • they act as natural painkillers by binding to opioid receptors in the brain and spinal cord

Enkephalins - are another group of endogenous opioids

  • bind to opioid receptors & modulate pain signals

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What are the 12 cranial nerves, their common name, their roman numeral and their major functions?

Olfactory (I) nerve

  • Smell

    • Surely sensory

Optic (II) nerve

  • Vision

    • Purely sensory, carry afferent impulses for vision

Oculomotor (III) nerve

  • Innervates four of six eye muscles and the upper eyelid

    • Eye movement & pupillary reflex

      • Mostly motor - movement of the eye

      • Parasympathetic - ANS motor fibers to pupils which caus pupls to constrict

      • Test of this nerve shine penlight into eye pupils shouldd constrict when illuminated

Trochlear (IV) nerve

  • Eye movement

    • Primary motor nerves; one extrinsic eye muscle

Trigeminal (V) nerve

  • Muscles of mastication

  • Has greatest cutaneous sensory distrubution of any cranial nerve

    • Sensory impulses of anterior scalp, eyelids, nose, cheek, teeth

  • 3 branches, 2 of which innervate the teeth

    • Motor - chewing muscles

    • Novocain - largest cranial nerve; used to block pain transmitting fibers of the teeth. Surrounding tissues becomes numb

Abducens (VI)

  • Extrinsic eye muscle

  • Turns the eyeball laterally (abducts)

  • Abduction of the eye

Facial (VII) nerve

  • Supplies muscles of facial expression

  • Involved in sense of taste

  • Salivary glands and lacrimal glands

  • Taste, facial expression, tearing

    • Tearing is controlled by the ANS

    • Bell’s palsy - sudden onset characterized by inflamed or swollen faciial nerve

    • Symptoms - paralysis or facial muscles on affected side

Vestibulocohelar (VIII) nerve

  • Involved in hearing & balance

    • Mostly sensory

    • Vestiular branch transmits afferent impulses for sense of equilbrium

    • Cochlear branch transmits afferent impulses for sense of hearing

    • Small motor component adjusts the sensitivity of the senroy receptors

Glossopharyngeal (IX) nerve

  • Swallowing, gag reflex

  • Sensory info from the:

    • Posterior tongue (taste)

    • Pharnyx = muscular tue extending from nasal cavity to esophagus

Vagas (X) nerve

  • Innervates muscles of the pharnyx and larnyx (voice box)

    • Swalloing and speech

  • Fibers supply heart, lungs, abdominal viscera- only cranial nerve wih visceral connections

    • ANS regulation of HR, breathing, digestion

Accessory (XI) nerve
Thought to have cranial that helped (accessory) the Vagas nerve

  • Not the case

  • Trapezius - shoulder elevation (shoulder shrug test is often used to test the health of the accessory nerve)

Hypoglossal (XII) nerve

  • Motor function - tongue muscles

    • Allow tongue movements that mix and manipulate food during chewing

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What is the role of nerve plexus in the body?

the ganglia interconnected by unmyelinated fiber tracts sorted and travels to anatomical structures to communicate signals to and from your brain

  • receives more than 1 spinal nerve

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What are dermatomes?

is an area of skin innervated by the cutaneous branches of a single spinal nerve

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What are the components of a reflex arc and what does each do?

Receptor - site of stimulus

Sensory neuron - transmits the afferent neurons to the CNS

Integration center - either monosynaptic of polysynaptic region without the CNS

Motor neuron - conducts efferent impulses from the integration center to an effector

Effector - muscle fiber or gland that responds to the efferent impulses

  • Monosynaptic - single synapse between sensory and motor neuron

  • Polysynaptic - multiple synpases, with chains of interneurons

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List the functions of the following reflexes: stretch reflex, tendon reflex, crossed extensor reflex

Stretch Reflex - muscle spindles

  • Proprioceptors that communicate info about length of a muscle

  • Rapid forceful stretching activates the spindle

  • Causes contraction when resists the stretching

Tendon Reflex - muscle relax and lengthen Golgi tendon organs

  • provide information about the amount of tension in muscle

  • Contracting the muscle activates the Golgi tendon organs

    • Afferent Golgi: tendon neurons are stimulated, neurons inhibit the contracting muscle

    • As a result, the contracting muscle relaxes and the antagonist contracts

Crossed Extensor Reflex - two parts

  • The stimulated side is withdrawn (away) Flexor Reflex

  • The opposite side is extended

    • Flexor Reflex - can be overridden by higher brain centers, such as when you are expecting a painful stimulus (finger stick) for example to draw blood)

      • Includes initial flexor reflex followed by crossed extensor on the opposite of the body

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CH 14

__________________________

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Draw the structural organization of the CNS and PNS and its subdivisions. Know how these subdivisions control behaviors.

The picture >

<p>The picture &gt;</p>
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Figure 14.2 represents a summary of the parasympathetic and sympathetic system and shows how the nerves are organized, their connections and their neurotransmitter; know how and why these connections occur and how this benefits each system as compared to the somatic system.

The picture

<p>The picture </p>
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What is the role of the sympathetic system?

ganglion located close to CNS and away from target organs = short preganglionic fibers & long post-ganglionic fibers

  • Mobilizes the body activity

    • E division

      • Exercise, embarrassment, excitement, emergency

  • Vigorous physical activity

    • Blood is directed towards active skeletal muscles

  • Visceral blood vessels are constricted

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What is role of parasympathetic system?

ganglion located away from CNS and near target organ = long preganglionic fibers

  • Promotes maintenance functions and conserves body energy

    • Reason its important to rest and not exercise after a big meal

    • D division

      • Digestion, Defecation, Diuresis (urination)

        • Directs general “housekeeping” activities

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For each ANS system, know the following: (table 14.1 and fig 14.3, 14.4, 14.5): What are the sites of origin of the fibers , relative length of fibers, location of ganglia

SITES OF ORGANS

PARASYMPATHETIC

  • Emerge from the brain (cranial nerves)

    • Ganglion located away from CNS and near target organ = long preganglionic fibers, and short pre-ganglionic fibers

SYMPATHETIC

Originate in the thoroculumbar region of the spinal cord

  • Ganglion located close to CNS and away from target organs = short pre-ganglionic fibers and long post-ganglionic fibers

This functional arrangements means -sympathetic system can take a signal and initiate a “all hands-on deck” command and gets a very rapid, collective response.

  • Preganglinoic cell bodies arise from thorasic and first 2 lumbar segments of spinal cord (T1-T2)

RELATIVE LENGTHS OF FIBERS

PARASYMPATHETIC

  • Long pre-ganglionic and sort post-ganglionic fibers

SYMPATHETIC

  • The opposite

  • Short preganglinoic fiber and long post ganglionic fibers

LOCATION OF GANGLIA

PARASYMPATHETIC

  • Located in the visceral

    • Preganglinoic neuron long synapses with post ganglinoic neuron near effector

SYMPATHETIC

  • Lie close to the spinal cord

    • Preganglinoic neurons are short. Synapses with post ganglinoic neuron near spinal cord

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60

What are the two types of Cholinergic receptors; what happens when ACh binds to each one of these?

Cholinergic receptors - release acetylcholine from preganglionic neurons & parasympathetic post-ganglionic neurons

Nicotinic - receptors response to ACh binding is always stimulatory

Muscarinic - receptors response to ACh binding is either stimulatory or inhibitory depending on the subclass of muscarinic receptors on the target organ

  • Nicotinic & Musacarnic are named for drugs that bind to them and mimic acetylcholine’s effects

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61

What are Adrenergic receptors? What happens when NE binds to these receptors?

Adrenergic neurons release norepinephrine (NE)

  • From postganglionic sympathetic neurons only

  • Excites or inhibits organs depending on receptors

  • Organs that respond to NE have one or more of the following receptors:

    • Alpha I and Beta I receptors produce excitation

    • Alpha 2 and Beta 2 receptors cause inhibition

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62

What does Parasympathetic and Sympathetic divisions have on the following: eye iris, sweat glands, arrector pilli muscles, heart muscles, lungs, digestive system, blood vessels, cell metabolism, adipose tissues.

Eyes (Iris)

PARASYMPATHETIC

  • Stimulates sphincter pupillae muscles; constricts pupils

SYMPATHETIC

  • Stimulates dilator pupillae muscles; dilates pupils

Sweat Glands

PARASYMETHETIC

  • No effect (no innervation)

SYMPATHETIC

  • Stimulates copious sweating (cholinergic fibers)

Arrector pilli muscles attached to hair follicles

PARASYMPATHETIC

  • No effect (no innervation)

SYMPATHETIC

  • Stimulates contraction (erects hairs and produces “goosebumps”

Heart Muscles

PARASYMPATHETIC

  • Decreases rate (slow heart)

SYMPATHETIC

  • Increases rate and force of heartbeat

Lungs

PARASYMPATHETIC

  • Constricts bronchioles

SYMPATHETIC

  • Dilates bronchioles

Digestive System

PARASYMPATHETIC

  • Increases motlity (perstalsis) and amount of secretion by digestive organs; relaxes sphincters to allow food to move through tracts

SYMPATHETIC

  • Decreases activity of glands & muscles of the digestive system; constricts sphincters; anal sphincters

Blood Vessels

PARASYMPATHETIC

  • Little or no effect (expect blood vessels to external genitalia)

SYMPATHETIC

  • Constricts most vessels & increases blood pressure; constricts vessels of abdominal viscera and skin to divert blood to muscles, brain, and heart when neccesary

Cell Metabolism

PARASYMPATHETIC

  • No effect (no innervation)

SYMPATHETIC

  • Increases metabolic rate

Adipose tissue

PARASYMPATHETIC

  • No effect (no inntervation)

SYMPATHETIC

  • Stimulates lipolysis (fat breakdown)

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63

What is vasomotor tone; what is parasympathetic tone and how do these work together with regard to heart and blood flow.

Vasomotor Tone - the baseline level of constriction or dilation in blood vessels

  • Function: It helps maintain vascular resistance and blood pressure

  • The vasomotor raises your heart rate (sympathetic) when scared, and your parasympathetic calms you down.

Parasympathetic Tone - is often called “rest & digest” system

  • Function: Maintains basic functions of the body nervous system

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64

What ANS system regulates body temperature?

hypothalamus (main integration center of the ANS)

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65

Why does sympathetic system last longer when activated?

it lasts longer because it immediately rises up (ex heart rate) by dumping epinephrine in the bloodstream, takes awhile for body to clear out the epinephrine out of the blood stream

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66

What controls the balance between ANS subsystems?

Hypothalamus - regulates balance (tone) between sympathetic and parasympathetic activity levels

Mediation and getting excited (cortex) can influence it.

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67

What is hypertension and its cause?

Hypertension

  • High BP

  • Can be promoted by overactive sympathetic response to chronic stress

  • Risk factor for CV disease

  • Sometimes treated with adrenergic —receptor blockers (Beta-blockers)

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