VTMD 206 - Neuro 3

Brain

Major Area Responsible for Motor Control

•  Integrates sensory information and initiates movement

• Integrates sensory information 

• Initiates and ensures proper goal-directed movement

Brainstem

Major Area Responsible for Motor Control

• Refinement area

• Unconscious motor control

• Relay and augmentation of locomotion/voluntary movement, posture, respiration, cardiovascular output

Spinal Cord

Major Area Responsible for Motor Control

• Dorsal=sensory

• Ventral=motor output

• Simple reflexes (fully contained within the spinal cord, independent from the brain)

• Sensory input (dorsal horn) and motor output (ventral horn) 

• Where rhythmic movements reside and are generated

Muscle

Major Area Responsible for Motor Control

• Contraction and sense through proprioceptors

• Motor end plate onto muscle fibre cells and proprioceptors (sensory afferents and can sense muscle tone and send information to the spinal cord)

Brain → motor neurons in the spinal cord ventral horn → motor end plates → neuromuscular junction → ACh release → muscle contraction → feedback on relative muscle tone provided by sensory neuron innervation

How are Muscle Cells Engaged?

Reflexive

Main Type of Motor Control

• Spinal cord loops => quick responses

Voluntary

Main Type of Motor Control

• Goal-directed movement

Rhythmic

Main Type of Motor Control

• Maintenance of repetitive movements (locomotion)

Musculoskeletal proprioceptors

• __________ ____________ sense stretch, position, and force

• Present in muscles, at the junction of tendons, and joints 

  • Also often needs input from your vestibular system and eyes

• Sensory (afferent) neurons carry information from muscle to spinal cord 

  • Aα fibre 

    • Afferents that carry info from proprioceptors to ventral horn are Aα fibres

    • Very fast myelinated fibers

• Synapse into dorsal horn 

• Projections up to brain to refine movements

Golgi tendon organs

Type of Muscle Proprioceptor

• Muscle tension

• Present in skeletal muscle 

• Present at connections between muscles and tendons

• Sense tension of muscle

  • Stops muscle from receiving too much tension, preventing damage to the muscle

  • _____ _____ reflex prevents this when a high amount of tension on the muscle is sensed 

• Between muscle fibre cells and tendon 

• Significant activation leads to reflexive loss of tension

Muscle spindles

Type of Muscle Proprioceptor

• Muscle length via stretch

• Present in skeletal muscle 

• Sits in the center of every muscle

• Lie parallel to muscle fibre cells, contained within intrafusal fibres 

  • Intrafusal fibers help sense and give feedback on the amount of stretch a muscle is experiencing

  • When there is significant stretch, a message is sent from spindle to spinal cord

• Innervated by motor neurons for feedback!

• Gamma motor endings are important to gauge overall stretch of muscle, as opposed to relative/changes in stretch

Autonomic, Somatic, Upper, Lower, Alpha, Gamma

• ______ motor neurons – activate smooth and cardiac muscle 

• ______ motor neurons – activate skeletal muscle 

  • Upper vs. lower motor neurons 

    • _____ motor neurons = cell bodies in the brain

    • _____ motor neurons = cell bodies in the spinal cord/horn, receive info from upper motor neurons

    • _____ motor neurons – direct projections onto muscle fibres (motor end plate) 

      • Majority of motor neurons

    • _____ motor neurons – smaller diameter projections, projections onto intrafusal muscle fibres

      • Only regulate sensitivity of muscle spindle

Spinal cord

• Dorsal horn = sensory

• Ventral horn = motor control 

• White matter vs. grey matter 

  • White matter is more highly myelinated

• Upper motor neurons project onto lower motor neurons (which then produce their effects on muscle)

  • Excitatory MN - Glutamate

  • Inhibitory MN - GABA

    • Modulates responses

• Direct spinal loops for immediate sensory activation from dorsal horn to motor effect in ventral horn 

• Circuits for generation of rhythmic behaviours 

• Somatotopically arranged

  • As you move down SC, innervating different areas of the body

  • Ex. thoracic is forelimbs

  • Proximal muscles closer to the center

Patellar (Stretch) Reflex

1. Triggered by stretch of quadriceps muscles (caused by hammer knock) 

2. This activates muscle spindles and their Ia sensory afferents

3. Direct synapse onto alpha motor neuron (motor efferent fibers) 

4. Contraction of quadriceps muscle

• Also referred to as myotatic reflex 

• This reflex modulates the sensitivity of the muscle spindle 

• Reflex is there to maintain posture

Primary Motor Cortex (M1)

Part of the Cerebral Cortex

• Sits anterior to the somatosensory cortex in all animals

• Postcruciate/precruciate gyrus and rostral suprasylvian gyrus (in dogs) 

• Plans and initiates voluntary movements 

• Upper motor neurons here project to lower motor neurons in spinal cord 

• Neurons here are somatotopically organized and have different representation for different species 

• Left brain = right limb (decussation)

Premotor and supplementary motor areas (~M2)

• ~precruciate gyrus/ frontal gyrus 

• Helps to plan and sequence complex voluntary movements, along with prefrontal cortex

  • Set the stage/outline steps for movement before actual movement has even occurred

• Most projections are to M1

Basal Ganglia

• Causes action selection and sends signals to motor cortex to initiate movement

• Collection of several subcortical nuclei 

• Modulate motor output via projections to thalamus (and onto M1) and brainstem motor areas 

• Tonic inhibition of motor system => release of tonic inhibition by basal ganglia initiates a given movement 

• Regulation of motor and premotor regions to pick the right movement and facilitate smooth movement 

• Influenced heavily by the prefrontal cortex (involved in decision making)

• Role = paroxymal dyskinesia

• Paroxysmal = sudden, uncontrolled 

• Dyskinesia = uncontrollable, involuntary movements 

Pyramidal tracts

Motor and Descending (Efferent) Pathways

• Includes:

  • Lateral corticospinal tract

  • Anterior corticospinal tracts

Spinocerebellar Tracts

Tract that provides proprioceptive feedback to the brain

• Spinal cord → Cerebellum

• More unconscious perception

• Helps to fine tune unconscious movements

• Ex. maintain posture/balance

• Includes:

  • Posterior __________ tract

  • Anterior ___________ tract

Dorsal Column Medial Lemniscus

Tract that provides proprioceptive feedback to the brain

• More conscious perception

• Includes:

  • Gracile fasciculus

  • Cuneate fasciculus

Cerebellum

• Fine-tunes and ensures movements are correct, maintains posture and balance 

• Receives input from proprioceptors (spinocerebellar tract), motor cortex, and vestibular system 

• Can be divided into 3 sections

• No direct projections to lower motor neurons

  • Done through other mechanisms

• Executes commands to the spinal cord via the brainstem and motor cortex

Vestibulocerebellum

Section of the Cerebellum

• Balance and eye movements 

Spinocerebellum

Section of the Cerebellum

• Posture and limb coordination 

Cerebrocerebellum

Section of the Cerebellum

• Planning and timing of complex movements 

Pain

• An aversive sensory and emotional experience typically caused by, or resembling that caused by, actual or potential tissue injury

• Refers to both the sensory and psychological perception of nociceptive stimuli

• Subjective, it varies between individuals and varies day to day for an individual

• Usually adaptive, but times when it becomes chronic and is less adaptive

Nociception

• Refers to the physiological detection and processing of painful stimuli. Does not consider emotional/psychological aspects of the pain response

Acute Pain

• Protective 

  • Warns of existing or imminent tissue damage 

• Normal peripheral and central nervous system 

• Well defined temporal onset 

  • Can clearly define the moment when you felt that pain

• Variety of effective treatment options

Chronic Pain

• No known defensive or beneficial function 

  • Neuropathic or inflammatory 

• Aberrant peripheral and central nervous system 

• Poorly defined temporal onset 

  • Hard to tell when you started/in general felt pain

• Limited treatment options

Nociceptor

•  A sensory neuron that is activated by stimuli capable of causing tissue damage 

• Free nerve endings 

• Three types of nociceptors 

  • Mechanical (Mechanical trauma) 

  • Thermal (noxious heat and cold) 

  • Chemical 

• Also classified according to the afferent fibre (A-delta or C-fibre)

Aδ

Axon/Fibre of Nociceptor

• Fast Pain, temperature

  • Myelination, faster

  • Second smallest in diameter

  • Fire first – sharp, jabbing pain

C

Axon/Fibre of Nociceptor

• Slow Pain, Temperature, Itch

  • No myelination, slower

  • Smallest in diameter

  • Fire after – low, throbbing pain

Lateral spinothalamic tract, spinireticular tract, spinomesencephalic tract

3 Ascending Pain Pathways (Anterolateral System)

• Along the lateral side of the spinal cord

• Carry info up spinal cord to the brain

Lateral Spinothalamic Tract 

Ascending Pain Pathway

• Projects to thalamus, then to sensory cortex 

• Intensity & location

Spinoreticular Tract

Ascending Pain Pathway

• Projects to reticular formation and then to diverse brain areas (thalamus, hypothalamus) 

• Autonomic, motor, and sensory responses to pain 

• Motivational, affective and aversive aspects of pain 

• Emotional aspects of pain

Spinomesencephalic Tract 

Ascending Pain Pathway

• Projects to midbrain 

• Activates periaqueductal gray (PAG) = produces endogenous analgesia 

• Affective & aversive behaviours of pain (i.e fear)

Gate Control Theory of Pain

• Proposed by Melzack and Wall (1965) 

  • Explains how sensory information entering the spinal cord can either increase of decrease the transmission of pain signals to the brain 

• Concept: non-painful sensory input (touch or pressure) can inhibit transmission of pain signals at the spinal cord level

• Ex.

  • Hit thumb with hammer – gates are open

  • When you put pressure on thumb – gates close more

  • Depends on pain fibers and inhibitory interneurons

• Spinal cord receive signals from the periphery and from descending axons from the brain 

• Aβ fibers: Large, myelinated sensory fibers that transmit non-painful touch and pressure

• Aδ and C fibers: Nociceptive fibers that transmit information about potentially damaging stimuli. 

• Spinal inhibitory interneurons: Neurons that can reduce activity of nociceptive projection neurons

• Connect between different neurons

• A lot of interneurons in the SC contain GABA and Glycine

  • Inhibitory NT

Periaqueductal Grey Matter, Locus Coeruleus, Rostral Ventromedial Medulla

3 Descending Inhibitory Pain Pathways

• Transmit signals from the brain to the SC to dampen pain

Periaqueductal Grey Matter (PAG)

Descending Inhibitory Pain Pathway

• Release enkephalins 

• Mediated by opioid receptors

Locus Coeruleus (LC)

Descending Inhibitory Pain Pathway

• Release norepinephrine 

  • Released into SC and acts on A1 and A2 receptors

• 2-adrenergic receptors inhibit pre- and post-synaptic pain transmission 

• 1-adrenergic receptors release GABA from interneurons

Rostral Ventromedial Medulla (RVM)

Descending Inhibitory Pain Pathway

• Release serotonin 

• 5-HT (serotonin receptor) – multiple subtypes and different coupling; not well understood

Allodynia

Type of Pain Hypersensitivity — Characteristic of Chronic Pain

• Painful response to something that is usually non-painful

• Lowered pain threshold 

• Innocuous stimulus elicits pain 

• Innocuous touch (mechanical allodynia) 

• Cooling (cold allodynia)

Hyperalgesia

Type of Pain Hypersensitivity — Characteristic of Chronic Pain

• Increased/exaggerated response to pain to something that is normally painful

• Enhanced pain response to noxious stimuli 

• Typically evoked by heat stimulation

Spontaneous Pain

Type of Pain Hypersensitivity — Characteristic of Chronic Pain

• Pain that just occurs, no clear stimulus

• Pain in the absence of an overt stimulus 

• Recurring pain 

• 100% of chronic pain patients affected

Peripheral Sensitization

• Ex. cut finger, whole bunch of responses that cause ________ _________, fires much more strongly/robustly

  • Occurs bcs when you injure tissue, there is an inflammatory response and molecules come in, cytokines released, inflammation sensitizes neurons so they fire more readily

  • Greater output for a stimulus bcs fibers are sensitized

• Tissue injury leads to activation of immune cells, which release signaling molecules often referred to as the inflammatory soup 

• Signaling molecules activate ion channels (ASICs, purinergic receptors) and other receptors (TrkB) • Signaling molecules bind to and change gating of other channels (TRPV1, etc.)

• Net result is an amplification of nociceptor responses = more output for the same input 

• Requires input to be sustained

Central sensitization

• Within the CNS

• Pain pathways in brain and spinal cord respond way more strongly to a painful or non-painful stimulus due to changes in pathways, makes pathways function way more robustly in terms of sending pain signals

• Over the top response

• Composite measure pain scales

• Facial expression (“grimace”) scales

List 2 validated pain assessment scales

Central Pattern Generators

• a network of thoracolumbar spinal circuits that generate rhythmic motor output, do 2 things:

1. Alternating flexor-extensor activity 

2. Opposing activity on contralateral side 

• Coordinate movement between all 4 limbs as one

• Activated by excitatory drive from the brainstem 

• Brain input to the spinal cord can modulate the circuit, but is not required to maintain 

• Present in all vertebrates at birth

Ex.

• Breathing

• Mastication

• Heart pumping

• Flying

• Swimming

• Blinking

• Swallowing

Half Center Circuit

The ___________ Hypothesis

• Each side of the spinal cord contains one “__________” 

  • Bcs it drives one half of the stride (stance and swing)

• Each circuit produces alternating activity in flexor and extensor muscles in a single limb 

  • In ventral horn of the spinal cord, lower motor neurons, one sends response to flexor muscle and one sends response to extensor muscle

  • Also have interneurons that can send signals between extensor and flexor motor neurons

  • Inhibitory interneurons connect flexor and extensor interneurons, so that when one muscle is extending (extensor signals being sent), muscle cannot flex (no flexor signals being sent), and vv

1. Flexor afferent activates the excitatory flexor interneuron 

2. This activates the flexor motor neuron, and contracts the flexor muscle 

3. Activation of the excitatory flexor interneuron also activates an inhibitory (GABA) neuron 

4. This inhibits the extensor muscle

Mesencephalic locomotor region

• Part of the brainstem (midbrain) 

• Receives input from cortex motor areas and the basal ganglia 

• Projects to the reticular nuclei, which then project onto lower motor neurons in the ventral horn 

• Activation of the ___________ is sufficient to drive central pattern generators (intensity drives change from walk to trot to gallop)

Cortex Motor Areas and Basal Ganglia → MLR → Reticular Nuclei → Lower Motor Neurons

Process of initiating and maintaining gait

Descending supraspinal input

• Responsible for modulation of Central Pattern Generators

• Input, initiates, modulates, and stops locomotion action via CPGs

• Once it starts, keeps going until it receives further input from the brain

• Can be a voluntary modulation (faster or slower) 

• Can be a modulation in response to sensory input (proprioceptive, nociceptive, vestibular, visual, auditory) 

• Some modulation can occur through direct spinal reflexive circuits involving sensory input (e.g. proprioceptive)

• Reticular nuclei

• Red nucleus

• Vestibular nuclei

The cerebellum executes commands to the spinal cord via the brainstem and motor cortex

3 Important Areas:

Reticular nuclei

Part of cerebellum responsible for initiation and modulation CPGs

• Also referred to as the reticular formation 

• Communicates bidirectionally with many motor areas as an integration network 

• Also receives some direct input from proprioceptors 

• Direct projection to ventral horn (mostly to interneurons) to drive lower motor neurons (reticulospinal tract) 

  • Reticulospinal tract is very important for gait!

• The MLR projects here to initiate, maintain, modulate, and terminate CPGs in the spinal cord

Red nucleus

Part of cerebellum responsible for coordination and modification of gait

• Much more active in non-primate mammals (especially in cats) 

• Receives input from cerebellum and motor cortex 

• Direct projection to ventral horn (mostly to interneurons) to influence lower motor neurons (rubrospinal tract) 

  • Helps coordinate limb movements, including swing-phase movements by the flexor muscle and skilled forelimb actions (cat dodging obstacle)

  • Projecting directly to lower motor neurons and receives input from cerebellum

Vestibular nuclei

Part of cerebellum responsible for control of balance and equilibrium

• Receive info from vestibular system, control balance while walking

• Direct projection to LMN

• Communicates bidirectionally with cerebellum to take in vestibular information from world and process it 

• Receives input from proprioceptors, vestibular organs in ears, visual system, skin receptors, etc. 

• Direct projection to ventral horn (mostly to interneurons) to influence lower motor neurons (vestibulospinal tract) 

  • Corrects balance and muscle tone, stabilizes eye movements 

  • Directs many postural reflexes

• Rubrospinal tract

• Reticulospinal tract

• Vestibulospinal tract

Extrapyramidal tracts

• Controlled by parts of the cerebellum

Cervical and lumbar intumescence

• Spinal cord is thicker where the brachial plexus and the lumbar plexus are located, associated with spinal nerves that are going to innervate the appendicular skeleton

Cauda equina

Collection of segmental nerves that are collected into the spinal column before they emerge

Lumbosacral interarcuate space

• Area where CSF can be collected just above the sacrum

• More caudal epidural space can also be used for epidural injections

Filum terminale

Connective tissue coming off the surface of the spinal cord and coming back caudally where it will fuse with the dura in that space, terminates on the caudal vertebra

Dorsal Funiculus

Funiculus of the White Matter of the Spinal Cord

• Mostly ascending tracts

• On top

• Funiculi are composed of ascending and descending nerve fibers that are grouped within bundles to form tracts

Lateral Funiculus

Funiculus of the White Matter of the Spinal Cord

• Space between ventral and dorsal root

• Ascending tracts laterally

• Ascending and descending tracts located medially

• Funiculi are composed of ascending and descending nerve fibers that are grouped within bundles to form tracts

Ventral Funiculus

Funiculus of the White Matter of the Spinal Cord

• Contain ascending and descending tracts

• Located on the bottom

• Funiculi are composed of ascending and descending nerve fibers that are grouped within bundles to form tracts

Intervertebral foramen

• Where spinal nerves exit

Suprascapular nerve

Nerve of the Brachial Plexus

• from spinal nerves C6-C7, enters between the supraspinatus and subscapularis muscles near the neck of the scapula, crosses over to the lateral side via the scapular notch 

• Innervates supraspinatus and infraspinatus muscles

Subscapular nerve

Nerve of the Brachial Plexus

• From spinal nerves C6-C7, very short, enters the subscapularis muscle, sometimes two nerves 

• Innervates subscapularis muscle

Musculocutaneous nerve

Nerve of the Brachial Plexus

• from spinal nerves C6-C8, travels down the brachium between the biceps muscle cranially and brachial vessels caudally, provides a communicating branch to the median nerve in the dog, then it courses deep to the insertion of the biceps

• Innervates coracobrachialis, biceps and brachialis muscles, also provides a branch that innervates the skin of medial antebrachium 

Axillary nerve

Nerve of the Brachial Plexus

• from spinal nerves C7-C8, enters the leg between the subscapularis and the teres major level with the neck of the scapula 

• Innervates teres major, teres minor, deltoideus and part of subscapularis muscles 

Radial nerve

Nerve of the Brachial Plexus

• from spinal nerves C7-C8, T1-T2, enters the triceps distal to the teres major, spirals around the humerus on the caudal aspect 

• Innervates triceps, tensor fasciae antebrachii, anconeus, extensor carpi radialis, supinator, common digital extensor, lateral digital extensor, ulnaris lateralis muscles 

Median nerve

Nerve of the Brachial Plexus

• from spinal nerves C8, T1-T2, runs with the ulnar nerve, this common trunk lies on the medial head of the triceps, median is the cranial division and passes just cranial to the epicondyle of the humerus to enter the forearm 

• Innervates pronator teres, flexor carpi radialis, pronator quadratus, superficial digital flexor, deep digital flexor muscles 

Ulnar nerve

Nerve of the Brachial Plexus

• from spinal nerves C8, T1-T2, runs with the median nerve, this common trunk lies on the medial head of the triceps, ulnar is the caudal division and crosses the elbow caudal to the medial epicondyle of the humerus 

• Innervates flexor carpi ulnaris, deep digital flexor, interossei muscles, as well as skin of caudal antebrachium/palmar paw/fifth digit

Horse

In the _____, it is the median and musculocutaneous nerves that run together down the forelimb

Cattle

The musculocutaneous nerve in ______ loops under the axillary artery to join the roots of the median and ulnar nerves. All three nerves run a short distance down the forelimb before the ulnar branches off caudally and then smaller musculocutaneous branches leave variously as the nerve travels down the limb. Also, the axillary and radial nerves run together proximally before becoming separated to innervate their respective muscles.

Obturator nerve

Nerve of the Lumbosacral Plexus

• from spinal nerves L4-L6, it is formed within the caudomedial portion of the iliopsoas muscle and leaves the muscle dorsomedially, runs along the body of the ilium and leaves the pelvis by passing through the obturator foramen

• Innervates adductor, external obturator, pectineus and gracilis muscles 

Femoral nerve

Nerve of the Lumbosacral Plexus

• from spinal nerves L4- L6, pursues a course through the psoas muscles to reach the dorsocaudal corner of the flank and the iliopsoas muscle, on entering the thigh it runs between the sartorius and pectineus muscles 

• Innervates iliopsoas and quadriceps group (rectus femoris, rectus lateralis, rectus medialis, rectus intermedius) muscles 

Saphenous nerve

Nerve of the Lumbosacral Plexus

• branch of the femoral nerve that dives between the rectus femoris and vastus medialis to branch within 

• Innervates the sartorius muscles group

Caudal gluteal nerve

Nerve of the Lumbosacral Plexus

• variably from spinal nerves L7 and/or S1-2, passes over the ischiatic notch medial to the middle gluteal muscle and enter the medial surface of the superficial gluteal 

• Innervates superficial gluteal muscle 

Cranial gluteal nerve

Nerve of the Lumbosacral Plexus

• from spinal nerves L7 and S1, passes over the greater ischiatic notch, crosses the lateral surface of the ilium at the origin of the deep gluteal muscle 

• Innervates middle and deep gluteal muscles 

Sciatic nerve

Nerve of the Lumbosacral Plexus

• from spinal nerves L6-L7 and S1-S2, passes over the greater ischiatic notch, caudally over the hip medial to the greater trochanter and travels distally, caudal to the femur on the lateral side of the adductor muscle (most you exposed this when you lifted the biceps femoris muscle up), sciatic nerve terminates in the thigh as the tibial and common fibular nerve 

• Innervates gemelli, internal obturator, quadratus femoris, biceps femoris, semimembranosus and semitendinosus muscles 

Tibial nerve

Nerve of the Lumbosacral Plexus

• Larger of the two sciatic branches, heads caudally and at the stifle it passes between the two heads of the gastrocnemius muscles 

• Innervates gastrocnemius, superficial digital flexors, popliteus, deep digital flexor muscles 

Common (peroneal) fibular nerve

Nerve of the Lumbosacral Plexus

• smaller of the two sciatic branches, heads craniolaterally deep to the thin part of the biceps femoris muscle, it crosses the lateral head of the gastrocnemius muscle and then passes between the lateral digital flexor and fibularis longus, divides into smaller branches 

• Innervates cranial tibial, long digital extensor muscles, lateral digital extensor, fibularis longus muscles

Lumbosacral trunk

Name for Cranial gluteal nerve and Caudal gluteal nerve together

Horse and Cow (horse earlier than cow)

 In the _____, the sciatic splits into its tibial and peroneal branches much earlier than in the dog.

Brain or brainstem

Neuroanatomical Localization

Abnormal mentation = lesion in the __________

Brainstem (multiple) or Peripheral Cranial Nerve (single)

Neuroanatomical Localization

Cranial Nerve Deficits = lesion in the __________

Cerebellum, Vestibular, Proprioceptive

Neuroanatomical Localization

Ataxia = lesion in the __________

Spinal cord — Lower motor neuron

Neuroanatomical Localization

Reduced/Absent Reflexes = lesion in the __________

Spinal Cord — Upper Motor neuron

Neuroanatomical Localization

Normal/Increased Reflexes = lesion in the __________

Mentation

• Refers to a patient’s mental activity 

  • Originates mainly at the level of the Cerebrum and brainstem (to a lesser extent)

• Alterations leads to various levels of alertness 

  • I.e. Dull, stuporous, comatose

• Dogs with altered ______ do strange things 

  • Head pressing, stargazing, wandering, ignoring owners etc

C6-T2 or L4-S3

If reduced reflexes (LMN issue), the spinal lesion is either between _____ or _____

Sedation

• CNS depression with drowsiness and some degree of centrally induced relaxation 

• Still rousable, will respond to noxious stimuli but generally unaware of surroundings 

  • Very relaxed, but rousable and respond to noxious stimuli

• Tends to preserve autonomic reflexes 

• Can have tranquilizing effects 

  • Anxialistic – reduces anxiety

• Are part of anesthesia protocol

• “Twilight Anesthesia” in humans

  • Misnomer, actually ______

Premedication

• Given prior to induction of anesthesia 

  • Get things started before putting them under anesthesia

• Usually 2 or more agents 

• Goals 

  • Relieve anxiety, apprehension, fear 

  • Counteract unwanted side effects of anesthetic agents 

  • Shorten procedure overall (amount of time they are under anesthesia)

  • Anesthetic sparing (use less of it)

  • Increased safety 

  • Perioperative analgesia (pain control)

General anesthesia

• From Greek meaning ‘insensibility’ or ‘without feeling’ 

• Reversible unconsciousness that is characterized by controlled depression of the CNS 

  • Not rousable by noxious stimuli 

  • Reflexes attenuated (sensory, motor, autonomic) 

  • Amnesia 

• General vs dissociative 

  • Levels of consciousness 

  • Dissociative state = do not respond, but look awake

    • More helpful for short procedures

• Administered through various routes

  • Inhalational, IV, IM

Analgesia

• Absence of pain in response to stimulation that would normally be painful 

• Varying degrees of efficacy 

  • Agent 

  • Timing of administration matters 

  • Hypoalgesia - lowering of pain

• Part of anesthesia and sedation protocols

• Can be sedative themselves 

• Not always related to drug administration, other routes

  • Electroacupuncture

  • Laser therapy

  • Can be combined

Local anesthesia

• Reversible block of the generation and propagation of electrical impulse through nerves 

• Only way to achieve 100% analgesia, if they work

• Non-specific 

  • Affect on sensory and motor

• Successful block results in 

  • Decreased anesthetic requirements 

  • Sustained analgesia 

  • Reduced mortality

Neuroleptanalgesia

• Gave sedation and a potent pain medication/analgesic with it

Multimodal Analgesia

• Doing more than one thing to keep your patient comfortable

• Using multiple ways to block many parts of the pathways to prevent pain in patient

Balanced anesthesia

• Induces:

  • Unconsciousness 

  • Analgesia 

  • Reflex suppression 

  • Muscle relaxation 

  • Amnesia 

• Produced by combination of 2-3+ drugs 

  • Use less of each drug = increased safety