Nerve and Muscle

Question 1

what do each of the cells do 
multipolar 
unipolar 
bipolar
neurogllia 
astrocytes 
oligodendrocytes 
microglia 
ependyma

Answer 1

motor neurones, can be pyramidal or stellate
PNS - in sensory ganglia cell body attached at the side
retinal - found in sensory structures
glial cells - considered supporting cells for neurones
involved in metabolic exchange between neurones and blood
militate the axon
less common immune defence
lining cells for ventricles have cilia on lumen

Question 2

difference between dendrites axons and neuritis

Answer 2

neuritis are dendrites and axons
dendrites are shorter and thicker giving rise to small spins
axons are long and thin usually only one axon

Question 3

difference between nerves and ganglia

Answer 3

nerves are axons and ganglia are cell bodies

Question 4

what are nerves made up of

Answer 4

bundles (fascicles) of myelinated and non-myelinated axons plus blood vessels and shwwan cells

Question 5

what are the two types of ganglia

Answer 5

sensory and autonomic (efferent neurones from ANS)

Question 6

what is the structure of a peripheral nerve

Answer 6

epineurim - covers whole nerve
perineurium - covers whole fascicle
endoneruim covers individual nerve axons

Question 7

what do satellite and schwaan cells do

Answer 7

satellite - surround nerve body and may aid in controlling chemical envirmoent of neurones
schwaan cells for myelin sheath around large nerve fibres and are phagocytic

Question 8

what is the difference between oligodendrocytes and schwaan cells

Answer 8

oligo - myelin sheath in CNS (around several axons)

Schwaan cells - myelin sheath in PNS (one single axon)

Question 9

difference between somatic and autonomic

Answer 9

somatic - voluntary

auto - involuntary - heart beat, lungs, BP etc

Question 10

autonomic is split into what

Answer 10

sympathetic and parasympathetic

Question 11

what is the difference in structure and neurotransmitter between pre ganglionic and postganlionic

Answer 11

Preganglionic fibres  long, myelinated (p.)  short, myelinated (s.)
Postganglionic fibres  short, few branches (p.)  long, many branches (s.)
Location of ganglia  near/in target tissue (p.)  close to spinal cord (s.)
Preganglionic transmitter  Ach (p.)  Ach (s.)
Postganglionic transmitter  Ach (p.)  Noradrenaline (s.)
When active  rest, sleep (p.)  stress, exercise (s.)
Physiological effect  slow things down (p.)  speed things up (s.)

Question 12

what are the classifications of nerve fibres

Answer 12

it is based on nerve fibre diameter and conductance 
1st class is A (fastest) B and C - motor fibres and some non-muscle sensory 
2nd class = I (fastest), II, III, IV

Question 13

what are non myelinated sensory fibres referred to as

Answer 13

C fibres

Question 14

what do proprioreceptors do

Answer 14

concerned with position of muscles tendons and joints

Question 15

what are the 4 receptors endings

Answer 15

free endings - connective tissues/ muscle/ skin - slow or fats adapting - pain, touch, light, pressure
Pacinian corpuscle = deep dermis/tendons/joints/genitalia, vibration/deep pressure, fast adapting
Meissner’s or krause’s bulbs = oral mucosa/lips/genitalia/fingertips, touch/vibration/light pressure, rapid adapting
Ruffini organs = deep dermis/ligaments/joint capsules, stretch/deep pressure, very slow adapting

Question 16

what is a simple spinal reflex pathway

Answer 16

1. Sensory receptor = site of stimulus action
2. Sensory neurone = transmits afferent info to the CNS
3. Integration centre = one or more synapses within CNS (may also signal up to brain)
4. Motor neurone = conducts efferent impulses to effector organ
5. Effector = muscle fibre (or gland) that responds to impulses

Question 17

what is the role of proteins on the resting potential

Answer 17

large negatively charged proteins can’t exit the cell and help maintain a -65 mV resting potential

Question 18

what is the definition of the nerviest equation and what is it used for

Answer 18

cell resting membrane potential close to but not equal to K+ equilibrium potential, also small leak for Na+, equation determining equilibrium potential for any ion, determined using conc. of ion inside/outside and cell temp.

Question 19

what are the 4 phases of an action potential

Answer 19

Phase 1 = Na+ channels open, Na+ enters nerve cell, membrane potential rises towards 0
Phase 2 = if threshold potential reached, voltage gated Na+ channels open, cell depolarises, Na+ ions flow into cell, action potential spike results
Phase 3 = Na+ channels close when Na+ equilibrium potential reached, voltage gated K+ channels open and K+ ions flow out of cell, membrane potential reverses
Phase 4 = K+ ions continue to flow out of cell while Na+ channels closed, hyperpolarisation results for brief period before normal resting potential restored, during this period (refractory period) another action potential cannot be generated, so action potentials only travel one way

Question 20

what are the benefits of the refectory period

Answer 20

no further action potentials can be elicited, ensures action potential propagation is unidirectional, action potential can only travel along axon from cell body to terminal, during relative refractory period, larger stimulus can result in action potential

Question 21

what is sensory transduction

Answer 21

conversion of environmental or internal signals into electrochemical energy

Question 22

receptors in muscles are varied what are they

Answer 22

sensory, proprioceptors and mechanoreceptors

Question 23

how and where are muscle spindle fibres stimulated

Answer 23

located within muscle and stimulated when muscle passively stretched, bundle of modified skeletal muscle fibres enclosed in connective tissue capsule

Question 24

what is the golgi tendon organ

Answer 24

located in tendon and responds to tension (stimulated when associated muscle contracts), small bundles of tendon (collagen) fibres enclosed in layered capsule with terminal branches of large diameter afferent fibre intertwined with collagen bundles, active during passive stretch and active contraction, tension director that protects muscle against excess load

Question 25

how does the spindle protect the muscle

Answer 25

When muscle is stretched passively the spindle is activated and initiates a reflex, when muscle contracts and shortens it is switched off, protects muscle being overstretched

Question 26

describe the knee jerk pathway

Answer 26

monosynaptic stretch reflex, stretching of muscle stretches spindle resulting in increased discharge of sensory nerves, results in increased firing of motoneuron, muscle contracts, no spinal interneuron is involved, effect is to dampen stretch of the muscle, specific for muscle stretched

Question 27

what are the differences in chemical vs electrical transmission

Answer 27

``` Electrical = more common in invertebrate nervous system, do occur in human brain and involved in epileptiform activity, formed by interlocking connexon channels of adjacent neurones, connexons comprise connexin proteins, present at points of contact between neurones with no synaptic cleft, only very narrow gap, direct, very fast electrical transmission, unidirectional in mammalian CNS but bidirectional in invertebrates Chemical = interface for chemical communication between neurones, release of transmitter from synaptic vesicles on arrival of an action potential in the terminal bouton of neuronal axon ```

Question 28

what are the structural differences between ionotrophic and metabotrophic

Answer 28

ionotrophic receptor = cluster of similar subunits forming ion channels, that depolarise or hyperpolarise the postsynaptic cell (fast responses), metabotrophic receptors = 7-transmembrane molecule coupled to intracellular proteins that transduce a signal to cell interior (slow responses)

Question 29

what is a neuromuscular junction

Answer 29

synapse between a motor neurone and skeletal muscle fibres

Question 30

where are neurotransmitter receptors concentrated

Answer 30

in post junctional folds

Question 31

what neurotransmitter is released at NMJ

Answer 31

ACh

Question 32

in a NMJ which receptors does ACh bind to

Answer 32

nicotinic receptors

Question 33

where is AChE found

Answer 33

in the cleft and attached to the basal lamina

Question 34

what happens to ACh after it is broken down

Answer 34

into acetate and choline choline reabsorbed to pre synapse acetate binds with CoA to for acetyl c A which then reacts with choline to make more ACh

Question 35

what causes the concentrated vesicles full of ACh in the cell

Answer 35

Antiporter H+ / ACh - into vesicle

Question 36

how are vesicles reserved and blocked

Answer 36

Reserve vesicles anchored near active zone by synapsin that tethers them to actin filaments Docking of vesicles, v-snare protein on vesicle binds to t-snare on membrane at active zone

Question 37

how is choline taken up

Answer 37

Na + co transporter

Question 38

what are synaptic vesicle pools

Answer 38

multiple, readily releasable, undergo exocytosis in response to single action potential as have been primed by docking at active zone, recycled synaptic vesicle pool, reserve pool ensures neurotransmitter is available even for highest physiological demands

Question 39

what does Curare do

Answer 39

comes from plants found in s. America, tribes used it to hunt and kill animals, causes muscle paralysis, so animals die from asphyxiation, If create artificial respiration for around 2 hours can recover

Question 40

what does tubocurarine do

Answer 40

non-depolarising competitive nAChR antagonist, competes with ACh for nicotinic receptor binding sites, muscle paralysis occurs gradually, reversed by AChE inhibitors, as ACh is around for longer so eventually outcompetes, hydrolysed by circulating esterases, therapeutic use in surgery, adverse effects are decreased DP and bronchospasm

Question 41

what does succinylcholine do

Answer 41

depolarising nAChR agonist, persistent depolarisation of NMJ, phase 1 = membrane depolarised causing brief period of muscle twitching as fibres firing off all of a sudden, phase 2 = end plate eventually repolarises, but as drug not metabolised as rapidly as ACh it continues to occupy receptor, causes flaccid paralysis, hydrolysed by circulating esterases, therapeutic use in surgery given continuously, adverse effects in halothane susceptible people experience malignant hyperthermia

Question 42

what does neostigtme/edrophonium do

Answer 42

cholinesterase inhibitors, therapeutic use as antidote for non-polarising blockers e.g. tubocurarine, treatment for and diagnosis of myasthenia gravis, adverse effects are generalised cholinergic activation (muscarinic and nicotinic), abdominal cramping, diarrhoea, salivation, incontinence, other uses nerve gas as weapon of war

Question 43

what does sarin do

Answer 43

liquid and gas, inhibits AChE, highly toxic and volatile agent, can linger on clothes so spread easily, causes muscle convulsive contractions, nose and eyes watering, drooling, nausea, vomiting, constriction of pupils to pinpoints, loss of control of bladder and bowel, chest pain, shortness of breath, collapse, seizures, death end result due to asphyxia

Question 44

what are tetanus and botulin toxins

Answer 44

reduce probability of neurotransmitter release by preventing vesicles binding to pre-synaptic membrane

Question 45

what does tetrodoxin do

Answer 45

binds to Na+ channel to block activation

Question 46

what is lambert-eaton syndrome

Answer 46

Reduced ACh release as autoantibodies stop Ca influx associated with lung cancer cancer symptoms, abnormal reflexes, lack of saliva doesn't usually affect respiratory/face/eyes diagnosed with electromyography and test for antibodies treatment - immunosuppressants or amifampridine - blocks K so action potential duration is bigger

Question 47

``` what does these types of muscle mean pennate fusiform parallel convergent circular skeletal cardiac smooth ```

Answer 47

feather like arrangement, unipennate (hands), bipennate (legs/thighs), multipennate (shoulders) spindle shaped fascicles lie parallel to axis of muscle, flat muscles (often have aponeuroses) broad attachment from which fascicles converge to a single tendon surround body opening/orifice, constricting when contracted striated, multinucleated, voluntary, non-branching, attached to skeleton striated, single nucleus, involuntary, branched, heart muscle non-striated, single nucleus, involuntary (stimulus), tapered, forms walls of organs

Question 48

what is the basic muscle structure

Answer 48

sarcolemma inside of is sarcoplasm, which surrounds myofibril, which contains filaments made up of actin and myosin

Question 49

what is the difference between actin and myosin

Answer 49

``` Actin = major component of I-band, extend into A-band Myosin = bipolar, extend throughout A-band, major component of H-zone, crosslinked at centre by M-band ```

Question 50

``` what do these refer to Z line I band A band H zone M line Titin ```

Answer 50

disc between I-bands appears as series of dark lines Surrounds Z line zone of thin filaments not superimposed bu thick filaments - ie only actin present a band - section contain whole of myosin H zone - within A band, paler region, zone of thick filaments (myosin only) M line - inside H zone middle of sarcomere - formed of cross connecting elements connecting protein extends from Z line which binds to actin and M band which interacts with myosin

Question 51

what is the mechanism of muscle contraction

Answer 51

Troponin complex moves tropomyosin This exposes myosin-binding sites on actin Unblocking the binding sites 1. Action potential arrives at NMJ 2. ACh is released, binds to receptors, opens Na+ channels leading to action potential in sarcolemma 3. Action potential travels along T-tubule 4. Ca2+ released from sarcoplasmic reticulum 5. Ca2+ binds to TnC region of troponin 6. Troponin changes shape, moves tropomyosin, exposing binding site on actin filament 7. Myosin head with ADP + Pi binds actin and attaches 8. Myosin head bends, pulling along actin filament, ADP + Pi released during power stroke

Question 52

what happens to the bands in contraction of muscle

Answer 52

ATP and Ca2+, A-band remains unchanged, H-zone gets shorter, distance between Z-lines gets shorter

Question 53

what are isotonic contractions

Answer 53

causes muscle to change length as it contracts

Question 54

what is the differences between concentric eccentric isometric

Answer 54

muscle shortens muscle lengthens as it contracts such as a slow relation rep at the end of a set no change in length as the muscle contracts

Question 55

what are the stages of a muscle twitch

Answer 55

``` 1 = latent period, delay of a few milliseconds between action potential and start of contraction, reflects time for excitation-contraction coupling 2 = contraction phase, starts at end of latent period and ends when muscle tension peaks, cytosolic calcium levels increasing as released calcium exceeds uptake 3 = relaxation phase, time between peak tension and end of contraction, when tension returns to 0, cytosolic calcium is decreasing as reuptake exceeds release ```

Question 56

what is the difference between fast twitch and slow twitch

Answer 56

fast twitch - type II fibres, white, lots of mitochondria, myoglobin less dense, contract quickly and powerfully, fatigues easily slow twitch red as lots of myoglobin, dense capillaries, contract slowly but little force, very resistant to fatigue, large amounts mitochondria, produces low amount of power, used in aerobic activities e.g. long distance running

Question 57

difference between type IIb and IIa

Answer 57

Type IIa = red as lots of myoglobin, resistant to fatigue, contains large amounts mitochondria, contracts relatively quickly, produces moderate amount of power when contracted, used in long-term anaerobic activities e.g. swimming, fast twitch A fibres Type IIb = white as low myoglobin, fatigue very easily, contains low amounts mitochondria, contracts very quickly, produces high amount of power when contracted, used in short-term anaerobic activities e.g. sprinting and heavy lifting, fast twitch B fibres

Question 58

what does the force of muscle contraction rely on

Answer 58

the number of action potentials per second

Question 59

what happens when the muscle is stretched beyond the amount normal

Answer 59

number of cross bridges decreases as overlap between filaments decreases

Question 60

what are some examples of injury or oversuse of muscles

Answer 60

sprain/cramps/strain/tendinitis

Question 61

what is a genetic muscular disease

Answer 61

muscular dystrophy, more difficult to treat and diagnose, testing will happen and family history taken

Question 62

what are some neurological muscular disorders

Answer 62

multiple sclerosis/myasthenia gravis/Parkinson’s disease, as muscles require action potentials, can cause many issues

Question 63

what is myositis/polymyalgia rheumatica

Answer 63

short/long term condition, consequence of autoimmune condition (myositis), self-limiting treated with medication

Question 64

describe the structure of cardiac muscle

Answer 64

Striated with characteristic A and I bands, contains actin and myosin filaments in myofibrils Branched, interconnected, small Rich in myoglobin and mitochondria Forms thick layer in the heart called myocardium Each cell contains 1-2 centrally located nuclei Mitochondria comprise 30% of volume of cell, require lots of energy

Question 65

what do intercalated discs do

Answer 65

specialised cell-cell contacts, cell membranes interlock, function for mechanical coupling (desmosomes – macula adherens – which hold cells together to stop separation during contraction) (and fascia adherens – actin anchoring sites connect to closest sarcomere) and electrical coupling (gap junctions allow action potentials to spread quickly to adjoining cells, permit passage of ions between cells allowing depolarisation

Question 66

what are the phases of ventricular action potential

Answer 66

Phase 0 = cell depolarisation, greatly increased membrane permeability to Na+ ions, rush in through fast channels, down conc. gradient reversing cell polarity Phase 1 = partial repolarisation, loss of Na+ conductance and decrease in K+ conductance Phase 2 = plateau, due to slow inward flow of Ca2+ ions through slow channels, also some inward movement of Na+ through slow channels and a decrease in membrane K+ conductance Phase 3 = repolarisation, decreased Ca2+ conductance and increased K+ conductance, inside of cell again becomes negative relative to outside, Na+/K+ pump re-establishes distribution of ions Phase 4 = interval between action potentials when the ventricular muscles are at their stable resting membrane potential Long refractory period, no summation as refractory period lasts as long as twitch, so prevents tetanus

Question 67

what happens during complete heart block

Answer 67

no transmission through AV node, Purkinje fibres take over pacemaker, slower pacemaker activity in distal parts of conducting system allow heart to continue breating if SA node fails, patients have bradycardia and reduced cardiac output

Question 68

what is wolf parkinson white

Answer 68

disorder of conduction of the heart, pre-excitation syndrome, caused by presence of abnormal accessory electrical conduction pathway between atria and ventricles, electrical signals travel down abnormal pathway (bundle of Kent) may stimulate ventricles to contract prematurely, resulting in unique type of supraventricular tachycardia referred to as AV reciprocating tachycardia

Question 69

what are the 4 classes of anti arrhythmic agents and give examples

Answer 69

Class 1 = sodium channel blockers, treat ventricular ectopics Class 2 = beta blockers (block effects of catecholamines in beta1-adrenergic receptors, decreasing sympathetic activity on the heart), slow conduction in the SA and AV nodes Class 3 = potassium channel blockers, treat ventricular tachycardia and atrial fibrillation Class 4 = calcium channel blockers, slow conduction in the SA and AV nodes, shorten plateau of action potential but allow body to retain adrenergic control of heart rate and contractility

Question 70

what does digoxin do

Answer 70

foxglove plant digitalis, inhibits Na+/K+ ATPase pump, increases intracellular Na+ causing less Ca2+ to be secreted, so intracellular Ca2+ conc. remains high, used to treat heart failure, causes decrease in heart rate, increased force of contraction as there is more release of Ca2+ from the SR so another increase in release of Ca2+ during each action potential

Question 71

describe the process of excitation contraction curling in the heart

Answer 71

Ca2+ enters through voltage-gated L-type Ca2+ channels in T-tubule membrane Triggers further Ca2+ release from adjacent sarcoplasmic reticulum Each L-type channel controls only one SR release channel, so tight local control Ca2+ binds to troponin-C and contraction proceeds After contraction, relaxation occurs when Ca2+ unbinds from troponin Ca2+ pumped back into SR for storage Ca2+ exchanged with Na+ at the membrane Na+ gradient maintained by Na+/K+ ATPase

Question 72

how does noradrenaline affect excitation contraction coupling in the heart

Answer 72

Noradrenaline increases contractile force of the heart, acts through beta-type adrenergic receptor to increase cAMP, to activate PKA which phosphorylates L-type channel increasing passive Ca2+ influx Amplifies Ca2+ (calcium-induced calcium release)

Question 73

what regulates heart and force of contraction

Answer 73

ACh from parasympathetic acts on SA from vagus nerve and decreases HR NA from symp nerves increases rate of pacemaker cells

Question 74

what is the structure of smooth muscle

Answer 74

``` 2 sheets - one circular and one longitudinal more actin than myosin no troponin no sarcomeres no striations no t tubules or SR have caveolae - act like T tubules actin attached to dense bodies ```

Question 75

what is the mechanism of action of contraction of smooth muscle

Answer 75

Ca2+ binds to calmodulin, interacts with enzyme myosin kinase to phosphorylate myosin Once phosphorylated generates tension Cytoplasmic Ca2+ falls, Ca2+ calmodulin complex dissociates, inactivating myosin kinase Cross bridges dephosphorylated by enzyme myosin phosphatase

Question 76

which type of muscle can stay contracted for longer

Answer 76

smooth muscle Reduced ATP consumption, so takes long time for each cross bridge to detach from actin Rate of Ca2+ removal from cytoplasm is slow, so prolonging duration of contraction

Question 77

what is the difference between single unit and multi unit smooth muscle

Answer 77

Single unit = most common, gap junctions, located in GI, respiratory, urinary and reproductive tracts, in walls of small arteries, electrical activity may arise spontaneously due to presence of pacemaker cells, action potentials developed, nervous regulation via ANS, contract in response to stretch lack gap junctions so cells innervated individually, allows fine control, examples include ciliary muscle of the eye, controlling size of pupil and piloerector muscles of hair follicles, not spontaneously active, innervation autonomic, no inherent response to stretch, contractions slow and sustained

Question 78

what is dilated cardiomyopathy

Answer 78

enlarged heart - sudden death poor function weak muscles, short breath, heart failure can be due to viral infection, autoimmune, exposure t toxic compound

Question 79

what is hypertrophic cardiomyopathy

Answer 79

thickening of muscle due to athetoid performance myocardial disarray can have genetic causes common in young adults

Question 80

what is leiomyoma

Answer 80

fibroids of smooth muscle heavy uterine bleeding unknown genetic cause more common in afro-carribean race