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If this reaction does not occur discount citalopram generic depression of 1920, iron combines with these sub- stances and produces non- absorbable compounds order citalopram with american express anxiety triggers. Factors that decrease absorption: (1) Lack of hydrochloric acid in the stomach or adminis- tration of antacids purchase citalopram 10 mg amex anxiety medication 05 mg, which produces an alkaline environment (2) Combination of iron with phosphates purchase 20 mg citalopram visa mood disorder examples, oxalates, or phytates in the intestine. Has antioxidant properties similar Important for function of Adults (RDAs): males and Fish, meat, breads, and cereals to those of vitamin E myocardium and probably females, 19–>70 y, 55 mcg; 2. Deficiency most likely with long- other muscles pregnancy 60 mcg; lactation term IV therapy. Signs and symp- 70 mcg toms include myocardial Infants (AIs): 0-6 mo, 15 mcg; abnormalities and other muscle 7-12 mo, 20 mcg discomfort and weakness. A component of many en- Adults (RDAs): males 19–51+ y, Animal proteins, such as sis, hepatitis, nephrosis, malabsorp- zymes that are essential 15 mg; females, 19–51+ y, meat, liver, eggs, and tion syndromes, chronic infections, for normal metabolism (eg, 12 mg; pregnancy 15 mg; seafood. Wheat germ is also malignant diseases, myocardial carbonic anhydrase, lactic lactation, 16–19 mg a good source. Necessary for normal Other children: 1–10 y, 10 mg; and symptoms are most evident cell growth, synthesis males, 11–18 y, 12 mg; in growing children and include of nucleic acids (RNA and females 11–18 y, 15 mg impaired growth, hypogonadism in DNA), and synthesis boys, anorexia, and sensory impair- of carbohydrates and pro- ment (loss of taste and smell). Zinc excess is unlikely with dietary intake but may develop with exces- sive ingestion or inhalation of zinc. Ingestion may cause nausea, vom- iting, and diarrhea; inhalation may cause vomiting, headache, and fever. It also can be used prophylactically, before clini- periods of increased requirements (eg, childhood, preg- cal manifestations occur, in clients in whom this heredi- nancy). Oral ferrous salts (sulfate, gluconate, fumarate) are tary condition is likely to develop. Action starts in used to treat cystinuria, a hereditary metabolic disorder about 4 days, peaks in 7 to 10 days, and lasts 2 to 4 months. Otherwise, the iron content is recycled and severe rheumatoid arthritis that does not respond to con- its half-life is unknown. The drug is metabo- discolor feces, producing a black-green color that may be mis- lized in the liver and excreted in urine and feces, with a taken for blood in the stool. The most common adverse effects indicated in clients with peptic ulcer disease, inflammatory are anorexia, nausea, vomiting, and diarrhea. Blood loss in gastrointestinal bleeding, sufficient oxygen to body tissues 2. With gradual development of anemia, heavy or prolonged menstrual ﬂow, trau- 3. Iron deficiency increases absorption of minimal symptoms occur matic injury, and other conditions other minerals (eg, lead, cobalt, man- 3. With rapid development of anemia or ganese) and may produce signs of excess. Acute Excess State Acute iron poisoning usually occurs in small Acute toxicity Vomiting, diarrhea, melena, abdominal pain, children who take several tablets of an shock, convulsions, and metabolic acido- iron preparation. Chronic Excess State Chronic iron excess (hemochromatosis) is Excess iron is deposited in the heart, pan- Cardiac arrhythmias, heart failure, diabetes rare but may be caused by long-term inges- creas, kidney, liver, and other organs. It mellitus, bronze pigmentation of skin, liver tion of excessive iron salts (eg, ferrous sul- impairs cell function and eventually de- enlargement, arthropathy, and others fate), large numbers of blood transfusions, stroys cells. A major advantage of parenteral iron is that body • Ferrous sulfate (Feosol), which contains 20% elemen- iron stores can be replenished rapidly. Ferrous gluconate As with iron from dietary sources or supplements, iron (Fergon) may be less irritating to GI mucosa and there- dextran is minimally eliminated from the body. It contains 12% preparation is contraindicated in people with anemias elemental iron (eg, 36 mg per 325 mg tablet). Ferrous fu- not associated with iron deﬁciency and those with hyper- marate (Feostat) contains 33% elemental iron (eg, 33 mg sensitivity to the drug (fatal anaphylactoid reactions per 100 mg tablet). Small amounts small IV test dose should be given before a therapeutic of iron are lost daily (about 0. The drug is usually given IV but may be given and sloughing of intestinal mucosal cells. Thus, women of child-bearing potential need larger amounts of iron than children, men, and post- Magnesium Preparations menopausal women. Women who are pregnant have the greatest requirement and usually need an iron supple- Magnesium oxide or hydroxide may be given for mild hypo- ment. Although most iron products are available over magnesemia in asymptomatic clients. Magnesium sulfate is the counter, their use should be discussed with a health given parenterally for moderate to severe hypomagnesemia, care provider because of the toxicity that may occur convulsions associated with pregnancy (eclampsia), and pre- with iron accumulation in body tissues. Reasons for using iron dextran injec- may cause diarrhea; their uses as antacids and cathartics are tion include peptic ulcer or inﬂammatory bowel disease discussed in Chapters 60 and 61, respectively. Iron Preparations Ferrous gluconate (Fergon) Iron deﬁciency anemia PO 320–640 mg (40–80 mg elemen- PO 100–300 mg (12. A small test dose is re- required before therapeutic doses quired before therapeutic doses are given. Magnesium Preparations Magnesium oxide Prevent or treat hypo- Hypomagnesemia, PO magnesium Convulsions: IM, 20–40 mg/kg in a Magnesium hydroxide magnesemia oxide 250–500 mg 3–4 times 20% solution; repeat as necessary Magnesium sulfate Treat hypertension or convul- daily, milk of magnesia 5 mL sions associated with tox- 4 times daily, or a magnesium- emia of pregnancy or acute containing antacid 15 mL 3 times nephritis in children daily; IM (magnesium sulfate) 1–2 g (2–4 mL of 50% solution) 1–2 times daily based on serum magnesium levels Eclampsia, IM 1–2 g (2–4 mL of 50% solution) initially, then 1 g every 30 min until seizures stop Convulsive seizures, IM 1 g (2 mL of 50% solution) repeated PRN IV, do not exceed 150 mg/min (1. With Zinc Preparations magnesium sulfate, oral preparations act in 1 to 2 hours and last 3 to 4 hours; IM injections act in 1 hour and last 3 to 4 hours; Zinc sulfate is available in tablets containing 110 or 220 mg and IV administration produces immediate action that lasts of zinc sulfate (equivalent to 25 and 50 mg of elemental zinc, about 30 minutes. It is also an ingredient in several vitamin–mineral combination prod- ucts. Zinc sulfate is given orally as a dietary supplement to Potassium Preparations prevent or treat zinc deﬁciency. It is metabolized in the liver and excreted Potassium chloride (KCl) is the drug of choice for prevent- in feces; its half-life is unknown. It may be prescribed for clients who are receiving potassium-losing diuretics (eg, hy- Multiple Mineral–Electrolyte Preparations drochlorothiazide, furosemide), those who are receiving digoxin (hypokalemia increases risks of digoxin toxicity), There are numerous commercially prepared electrolyte solu- and those who are receiving only IV ﬂuids because of surgi- tions for IV use. One group provides maintenance amounts cal procedures, GI disease, or other conditions. KCl also may of ﬂuids and electrolytes when oral intake of food and ﬂuids be used to replace chloride in hypochloremic metabolic al- is restricted or contraindicated. It is contraindicated in clients with renal failure and in the number and amount of particular electrolytes. A sec- in those receiving potassium-saving diuretics, such as tri- ond group provides replacement amounts of electrolytes amterene, spironolactone, or amiloride. These preparations are avail- tions act slowly and peak in 1 to 2 hours; IV preparations act able from several different manufacturers; health care agen- rapidly. They are used to production of various ﬂavored powders, liquids, and efferves- supply maintenance amounts of ﬂuids and electrolytes when cent tablets (eg, Kay Ciel Elixir, K-Lor, Klorvess). They are especially useful in children containing a wax matrix (eg, Slow-K) are effective and better for treatment of diarrhea and may prevent severe ﬂuid and tolerated by most clients than liquid formulations.
- Urethral injury
- Does any activity make the pain worse?
- Have accidents related to alcohol use
- Vomiting, may be bloody
- Amount swallowed
- Thoroughly wash your hands
- Your doctor will tell you how to take this medicine. Most people take one 0.5 mg pill a day at first. By the end of the second week, you will likely be taking a 1 mg pill twice a day.
- Ischemic cardiomyopathy
It can be given orally and flammation order citalopram 10 mg visa depression diagnosis definition, it is uncertain whether oral administration of intrathecally through an implanted generic citalopram 20mg online anxiety breathing problems, subcutaneous pump order citalopram with paypal depression definition merriam webster. Baclofen and diazepam increase the effects of gamma- the action of oral baclofen starts in 1 hour discount citalopram 10mg amex mood disorder meds for kids, peaks in aminobutyric acid, an inhibitory neurotransmitter, and tizani- 2 hours, and lasts 4 to 8 hours. It is metabolized in the liver dine inhibits motor neurons in the brain. Dantrolene is the only and excreted in urine; its half-life is 3 to 4 hours. Dosage must skeletal muscle relaxant that acts peripherally on the muscle it- be reduced in clients with impaired renal function. Common CHAPTER 13 SKELETAL MUSCLE RELAXANTS 215 Drugs at a Glance: Skeletal Muscle Relaxants Routes and Dosage Ranges Generic/Trade Name Adults Children Baclofen (Lioresal) PO 5 mg 3 times daily for 3 days; 10 mg 3 times <12 years: Safety not established daily for 3 days; 15 mg 3 times daily for 3 days; then 20 mg 3 times daily, if necessary. Carisoprodol (Soma) PO 350 mg 3 or 4 times daily, with the last dose at <12 years: Not recommended bedtime Chlorphenesin (Maolate) PO 800 mg 3 times daily until desired effect attained, Dosage not established then 400 mg 4 times daily or less for maintenance as needed Cyclobenzaprine (Flexeril) PO 10 mg 3 times daily. Maximal recommended <15 years: Safety and effectiveness have not been duration, 3 weeks; maximal recommended dose, established. Orphenadrine citrate (Norﬂex) PO 100 mg twice daily Not recommended IM, IV 60 mg twice daily Tizanidine (Zanaﬂex) PO 4 mg q6–8h initially, increased gradually if Safety and effectiveness have not been established needed. Maximum of 3 doses and 36 mg in 24 h IM, intramuscular; IV, intravenous; PO, oral. Common adverse effects include drowsi- stipation, fatigue, headache, hypotension, insomnia, nausea, ness, dizziness, and impaired motor coordination. When discontinued, dosage should be tapered Chlorphenesin (Maolate) is used to relieve discomfort and the drug withdrawn over 1 to 2 weeks. Oral drug ef- Carisoprodol (Soma) is used to relieve discomfort from fects peak in 1 to 3 hours and last 8 to 12 hours; half-life is acute, painful, musculoskeletal disorders. The drug is metabolized in the liver and excreted mended for long-term use and, if used long term or in high in urine. Common adverse effects are drowsiness, dizziness, doses, it can cause physical dependence (ie, symptoms of with- confusion, nausea. The drug is contraindicated in Cyclobenzaprine (Flexeril) has the same indication for use clients with intermittent porphyria, a rare metabolic disorder as carisoprodol and chlorphenesin, above. It is contraindicated characterized by acute abdominal pain and neurologic symp- in clients with cardiovascular disorders (eg, recent myocardial toms. Oral drug acts within 30 minutes, peaks in 1 to 2 hours infarction, dysrhythmias, heart block) or hyperthyroidism. It is metabolized in the liver and has a Oral drug acts in 1 hour, peaks in 4 to 6 hours and lasts 12 to 216 SECTION 2 DRUGS AFFECTING THE CENTRAL NERVOUS SYSTEM 24 hours; half-life is 1 to 3 days. Common adverse effects are drowsiness, Nursing Notes: Apply Your Knowledge dizziness, and anticholinergic effects (eg, dry mouth, consti- pation, urinary retention, tachycardia). Her physi- Dantrolene (Dantrium) acts directly on skeletal muscle to cian orders Valium 50 mg to be given IV stat. Discuss how you will safely neurologic disorders (eg, multiple sclerosis, spinal cord in- administer this medication. For preoperative prophylaxis in people peaks in 2 hours and lasts 4 to 6 hours. The drug has a half- with previous episodes of malignant hyperthermia, the drug is life of 14 hours, is metabolized in the liver, and is excreted in given orally for 1 to 2 days before surgery. Common adverse effects include drowsiness, malignant hyperthermia, the drug is given intravenously. After dizziness, constipation, dry mouth, nausea, tachycardia, and an occurrence during surgery, the drug is given orally for 1 to urinary retention. Tizanidine (Zanaflex) is an alpha adrenergic agonist, 2 Oral drug acts slowly, peaks in 4 to 6 hours and lasts 8 to similar to clonidine, that is used to treat spasticity in clients 10 hours. IV drug acts rapidly, peaks in about 5 hours and with multiple sclerosis, spinal cord injury, or brain trauma. Common adverse effects include drowsi- It should be used cautiously with renal or hepatic impair- ness, dizziness, diarrhea, and fatigue. It is given orally and its action starts verse effect is potentially fatal hepatitis, with jaundice and within 30 to 60 minutes, peaks in 1 to 2 hours, and lasts 3 to other symptoms that usually occur within 1 month of starting 4 hours. Liver function tests should be monitored peri- liver and excreted in urine. Common adverse effects include odically in all clients receiving dantrolene. These adverse drowsiness, dizziness, constipation, dry mouth, and hypo- effects do not occur with short-term use of IV drug for malig- tension. It may also cause psychotic symptoms, including Metaxalone (Skelaxin) is used to relieve discomfort from hallucinations. It is contraindi- cated in clients with anemias or severe renal or hepatic im- pairment. Oral drug acts within 60 minutes, peaks in 2 hours and lasts 4 to 6 hours. It has a half life of 2 to 3 hours, is me- Nursing Process tabolized in the liver, and is excreted in urine. Common ad- verse effects include drowsiness, dizziness, and nausea; hepatotoxicity and hemolytic anemia may also occur. Methocarbamol (Robaxin) is used to relieve discomfort • With muscle spasm, assess for: from acute, painful, musculoskeletal disorders; it may also be • Pain. Parenteral drug is contraindicated in is usually aggravated by movement. Try to determine the clients with renal impairment because the solution contains location as speciﬁcally as possible, as well as the inten- polyethylene glycol. Oral drug acts within 30 minutes and sity, duration, and precipitating factors (eg, traumatic in- peaks in 2 hours; parenteral drug acts rapidly but peak and du- jury, strenuous exercise). The drug has a half life of 1 to • Accompanying signs and symptoms, such as bruises 2 hours, is metabolized in the liver, and is excreted in urine (ecchymoses), edema, or signs of inﬂammation (red- and feces. Common adverse effects with oral drug include ness, heat, edema, tenderness to touch) drowsiness, dizziness, nausea, and urticaria; effects with in- • With spasticity, assess for pain and impaired functional jected drug also include fainting, incoordination, and hypo- ability in self-care (eg, eating, dressing). The drug may also discolor urine to a green, brown, or spasticity interferes with ambulation and other movement black. This is considered a harmless effect, but clients should as well as exercises to maintain joint and muscle mobility. Nursing Diagnoses Orphenadrine (Norﬂex) is used to relieve discomfort • Pain related to muscle spasm from acute, painful, musculoskeletal disorders. Because of its • Impaired Physical Mobility related to spasm and pain strong anticholinergic effects, the drug is contraindicated in • Bathing/Hygiene Self-Care Deficit related to spasm and glaucoma, duodenal obstruction, prostatic hypertrophy, blad- pain der neck obstruction, and myasthenia gravis. It should be used • Deﬁcient Knowledge: Nondrug measures to relieve mus- cautiously in clients with cardiovascular disease (eg, heart cle spasm, pain, and spasticity and safe usage of skeletal failure, coronary insufﬁciency, dysrhythmias) and renal or he- muscle relaxants patic impairment. The action of both oral and parenteral drug CHAPTER 13 SKELETAL MUSCLE RELAXANTS 217 Drug Selection • Risk for Injury: Dizziness, sedation related to CNS depression Choice of a skeletal muscle relaxant depends mainly on the Planning/Goals disorder being treated: the client will: 1. For acute muscle spasm and pain, an oral or parenteral drug may be given. The drugs cause sedation and other • Experience relief of pain and spasm adverse effects and are recommended for short-term • Experience improved motor function use.
- A (BMI) of 40 or more. This usually means that men are 100 pounds overweight and women are 80 pounds over their ideal weight.
- Excessive bleeding
- What other symptoms do you have?
- Your knee is deformed or misshapen
- Take a stool softener to avoid constipation.
The most became clearer at 2–3 × MT at a latency of 31 ms cogentargumentsaredrawnfromexperimentsusing ((d )–(g )) citalopram 10mg on-line anxiety 24 hours, and increased further at 4–5 × MT buy citalopram 40 mg without a prescription mood disorder episodes, associ- bidirectional connections where the conclusions do ated with a decrease in latency to 30 generic 10mg citalopram otc definition of depression by psychologist. Similar results were found with the femoral-induced Notwithstanding this cheap citalopram 20mg online postpartum depression symptoms quiz, strong evidence is also pro- excitation of tibialis anterior units and the superﬁ- videdbyexperimentsshowingthatthedifferencesin cial peroneal excitation of soleus units. Given a threshold for Ia afferents of mous excitation is supported by (i) a low electrical ∼0. The mean decrease in latency of the monosynaptic peak relative to the latency at 1 × MThis plotted against the stimu- Range of electrical thresholds of lus intensity in M. Ia afferents when stimulating the decrease in latency is probably due to two using surface electrodes phenomena: stimulation of the afferents at more proximal nodes as stimulus intensity increased, so When stimulating peripheral nerves directly, as in producing an effectively shorter afferent path, and cat experiments, the stimulus strength has to be a more rapidly rising EPSP as more group I affer- increasedtotwicethethresholdofthemostexcitable ents were recruited. The latter has been shown in afferents to set up a maximal group I volley (Brock, the cat to produce a decrease in the latency of the Eccles & Rall, 1951). Given a threshold for human Ia corresponding peak in the PSTH of up to 0. However, ingwouldbeexpectedinhumansbecausetheextent in many muscles other than the soleus, the H reﬂex of shortening will depend on the dispersion of the appears and continues to increase at stimulus inten- excitatory input and on the EPSP rise-time, both of sities well above 1 × MT provided that the reﬂex dis- which are greater in human subjects. Modiﬁed from Gracies, Pierrot-Deseilligny & Robain (1994), with permission. Difference between the full recruitment Conclusions of Ia afferents in cat and human experiments Whatever the mechanism responsible for the wide This difference (at 2 and 8 × Ia threshold, respec- range of electrical thresholds of Ia afferents, this tively) is probably due to the fact that in human factor needs to be taken into account for two rea- experiments afferents are stimulated through elec- sons. As a result, the thresh- tion may be underestimated in human experiments, old for a ﬁbre will be determined as much by its which are generally performed with much lower distance from the stimulating electrodes as by its stimulus intensities (≤1 × MT) in an attempt to acti- size. Organisation and pattern of connections 79 Katz, 1989), ﬂexor carpi radialis (FCR) and ﬂexor Organisation and pattern of carpiulnaris(FCU)(Malmgren&Pierrot-Deseilligny, connections 1988), deltoid, triceps brachii, extensor carpi radi- alis (ECR), ﬂexor digitorum superﬁcialis (FDS) and the efﬁcacy of a given Ia input in discharging a extensor digitorum (ED) (Gracies et al. It must be emphasised that these investiga- inhibition and the level of post-activation depres- tions were performed during weak voluntary con- sion at Ia terminals; (iii) any limitation produced by tractions(below5%MVC),andthemotorunitsstud- inhibitory circuits activated by the test volley, and ied were all in the low-threshold range. Differences in the efﬁcacy of homonymous Homonymous monosynaptic Ia excitation Ia excitation in ﬁring motoneurones Estimate of the efﬁcacy of the Ia input in ﬁring Evidence for homonymous Ia excitation in all homonymous motoneurones motoneurone pools This efﬁcacy may be assessed by the ease with which Hreﬂex the H reﬂex can be elicited at rest and by the size of At rest, H reﬂexes can be recorded from the the peak of excitation elicited in the PSTHs of sin- soleus, quadriceps and FCR in most healthy subjects gle motor units by stimulation subthreshold for the. Generally, these subjects )), and rarely from other muscles ((c ),(f ), two measures are closely linked: e. However,anHreﬂexcanbeobtainedinvirtually with the ease with which the H reﬂex is obtained all limb muscles during a weak voluntary contrac- at rest in the soleus and FCR, the peak of homony- tion of the test muscle (see p. The difﬁculty in activating some motoneurone pools reﬂexly can- Homonymous monosynaptic Ia excitation not be attributed to low excitability of the motoneu- in single motor units rone pool: tibialis anterior is more excitable to corti- Stimulation of the parent nerve evokes an early peak cospinal inputs than soleus, while the reverse is true ofincreasedprobabilityofdischargeinPSTHsofsin- for Ia afferent inputs. The size of the (Bayoumi & Ashby, 1989), intrinsic foot muscles monosynaptic Ia peak should then decrease as (Marque et al. Given this preferential distribution of Ia exci- cles in which the different motor unit types have tatory inputs to motoneurones innervating slow- beeninvestigated:seconddorsalinterosseus(Buller, twitch units, it is not surprising that the soleus H Garnett & Stephens, 1980), soleus (Awiszus & Feist- reﬂex may be obtained in all healthy subjects at ner,1993),ECR-MACROS-. Hilton-Brown & Stalberg,˚ 1986;Semmler & Turker,¨ 1994) and in abductor digiti minimi (Mazzocchio, Heteronymous monosynaptic Ia Rothwell & Rossi, 1995), the largest responses to Ia excitation in the lower limb input have not been found in low-threshold units. Pattern and strength of distribution Inhibitory mechanisms limiting the efﬁcacy of the monosynaptic Ia input In striking contrast with data for the cat and baboon hindlimb (see pp. The constraints raised above, the conclusions advanced larger the maximal soleus H reﬂex at rest, the smaller below have generally been conﬁrmed using more the tonic on-going presynaptic inhibition of Ia ter- than one method. Grey cells represent Contamination by oligosynaptic IPSPs muscle–nerve combinations with a statistically sig- niﬁcantconnectioninhumans. This limitation could also based on the average size of the heteronymous peak contribute to the absence of a recordable H reﬂex relative to that of the homonymous peak, both in at rest in muscles, such as tibialis anterior, abduc- response to stimulation at 1 × MT. As expected, the tor pollicis brevis and ECR, though this would imply stronger the connection, the more frequently was it that the Ia/Ib balance was then shifted in favour of observed: e. In these muscles, the appearance of an trocnemius medialis to biceps femoris, ﬁve aster- Hreﬂex during a tonic voluntary contraction could isks) was observed in 21/21 (100%) units and was, involve depression of non-reciprocal group I inhibi- on average, 54% of the homonymous peak, whereas tion to the active motoneurone pool (see Chapter 6, the weakest connection (from the intrinsic plantar pp. Thresholds for α motor axons and Ia afferents Connections between close synergists operating Alternatively, if the threshold for motor axons was at the same joint closer to that of Ia afferents, the maximal H reﬂex would probably be smaller and the reﬂex more difﬁ- At knee level, strong connections exist between the cult to obtain and, with single motor units, the peak two heads of the quadriceps (vastus lateralis and 82 Monosynaptic Ia excitation Table 2. Monosynaptic heteronymous Ia excitation in the lower limb Columns: nerve stimulated: Sol (inferior soleus), GM (nerve to the gastrocnemius medialis), SP (superﬁcial pero- neal), DP (deep peroneal), FN (femoral nerve), TN (tibial nerve at the ankle). Lines: motoneurone pools (MN) investigated with the PSTH method: Sol (soleus), GM (gastrocnemius medialis), Per Brev (peroneus brevis), TA (tibialis anterior), Q (quadriceps), Bi (biceps femoris), ST (semitendinosus). Grey cells indicate the existence of signiﬁcantIaexcitationinhumans(crossedcellscorrespondtohomonymouspathways). Thenumberofasterisks indicates the average size of the heteronymous peak relative to the homonymous peak (both recorded using sti- mulationat1×MT):*<10%;**between10and20%;***between20and30%,****between30and40%;*****>40% (from Meunier, Pierrot-Deseilligny & Simonetta, 1993;Marque et al. Connections are compared to those described in the cat (cells with horizontal lines, Eccles, Eccles & Lundberg, 1957)andthebaboon(cellswithverticallines,Hongoetal. Withtheanimalexperiments,onlyconnections with a heteronymous EPSP >5% of the homonymous EPSP are shown. There is no Ia excitation from gastrocnemius medialis to soleus, There are bidirectional connections between soleus a ﬁnding conﬁrmed using different techniques: the andperoneusbrevis-MACROS-. Organisation and pattern of connections 83 Transjoint connections exist between all Phylogenetic adaptations muscle–nerve combinations tested In Table 2. However, it should be emphasised that cat(cellswithhorizontallines,Eccles,Eccles&Lund- conclusions based on stimuli at 1 × MT underesti- berg, 1957) and the baboon (cells with vertical lines, matethestrengthoftheconnectionsbecause,asdis- Hongo et al. These connections are not conﬁned to Connections between close synergists units in the low-threshold range investigated with Theabsenceofconnectionsbetweensomeclosesyn- the PSTH method. Many of the connections have ergists operating at the same joint in humans is pre- alsobeenobservedwithmethodsthatexplorealarge dictable because of their weakness in the baboon. Proximal-to- distal transjoint connections can be explored safely Themoststrikingdifferencesinvolvethepresenceof only from the femoral nerve, because it does not heteronymous connections that do not exist in the contain afferents from distal muscles. Because of cat or the baboon or, when they exist, are <5% of the the difﬁculty in stimulating the nerves to hamstrings homonymous Ia EPSP. Ia connections from tri- without encroaching upon afferents from foot and ceps surae onto quadriceps motoneurones, Edgley, leg muscles in the sciatic nerve (or of stimulating Jankowska&McCrea,1986;Hongoetal. Thus, the posterior tibial nerve without encroaching upon in human subjects, there are transjoint connections afferents from plantar foot muscles), it has not been between all muscle–nerve combinations tested. The possibletodeterminewhethertheconnectionsfrom functionalimplicationsofthesedifferencesinorgan- legmusclestohamstrings(andfromfoottoproximal isation of Ia connections are considered on pp. Projections to antagonists acting at another joint Aremarkable feature of these transjoint connections Heteronymous monosynaptic isthattheyoftenlinkamuscleorgroupofmusclesto Ia excitation in the upper limb a pair of antagonistic muscles operating at another joint, e. There is bidirectional, 84 Monosynaptic Ia excitation though asymmetrical, heteronymous Ia excitation Table 2. Electri- excitation in the upper limb cal stimuli at 1 × MT applied to the median nerve at elbow level often evoke monosynaptic Ia excitation ofFCUunits,whereassimilarstimulationoftheulnar nerve rarely evokes signiﬁcant excitation of FCR units (Malmgren & Pierrot-Deseilligny, 1988). An asymmetry has also been demonstrated using per- cussion of the tendons of FCR and FCU (Chalmers & Bawa, 1997), but this was less marked, possibly due to spread of the mechanical stimulus. Weak ECU facilitation by ED Ia afferents has been observed consistently but, in contrast with forearm ﬂexors, there is no evidence for heteronymous Ia excitation at a latency consistent with a monosynaptic linkage between ECR and ECU (Chalmers & Bawa, 1997). Columns: nerve stimulated: MC (musculo-cutaneous), Tri (nerve of the triceps brachii), Med (median), Rad (radial at the elbow), Uln (ulnar), Med & Uln (wrist) (median and ulnar at Absence of proximal-to-distal projections thewrist). Lines:motoneuronepools(MN)investigatedwiththe PSTH method: Deltoid, Bi (biceps brachii), Tri (triceps brachii), Again, there are striking differences from data in the FCR (ﬂexor carpi radialis), ECR (extensor carpi radialis), FCU cat(cellswithhorizontallines,Fritzetal.