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name and describe the somatic senses
- touch - diverse receptors -free or encapsulated nerve endings. encapsulated in connective tissue
- proprioception: 3 types, generally used to sende tension and positon of muscle, tendon and joints
- temeprature: free nerve endings
- nociception: pain/ itch (a-delta: fast pain, sort and mylenated; c fibers: dull pain)
- primary sensory neurons,
- to spinal cord,
- synapse with secondary sensory neuron,
- to brain stem, cross midline in medulla
- synapse on tertiary neuron in thalamus
- then to somatosensory cortex
pain also goes to limbic system and hypothalamus
muscle spindles (perceives muscle length),
golgi tendon organs (percieve tension at muscle/ tendon junction),
joint receptor (stim by joint movement
parasympthetic and sympthetic nerutransmitter
S; post G secrete norepenephrine (adrenertic receptiors) to target tissue
P: post g (nicotinic receptor) secrete actylcholine to target tissue (muscarinis receptors
The sympathetic nervous system is a "quick response mobilising system" and the parasympathetic is a "more slowly activated dampening system",
mostly uncncs effecting organs, can inc cough, sneeze, swallow
can have referred pain/ non-localized,
sequential two-neuron efferent pathway; the preganglionic neuron onto a postganglionic neuron before innervating the target organ.
- major difference between the two ANS systems: the number of postsynaptic fibers a single preganglionic fiber synapses with.
- parasympathetic divergence factor of roughly 1:4,
- sympathetic division there can be a divergence of up to 1:20.
The site of synapse formation and thus divergence for both types of preganglionic neurons occurs within ganglia situated within the PNS
Peripheral Nerve Fiber Classifications
A. Fibers of the A group have a large diameter and high conduction velocity, and are myelinated fibers.
B Nerve fibers in this group are myelinated with a small diameter. Generally, are the preganglionic fibers of ANS and have a low conduction velocity.
C: unmyelinated, small diameter and low conduction velocity. inc Postganglionic fibers in ANS. These fibers carry somatic sensory information. Damage or injury to nerve fibers causes neuropathic pain.
Tonic receptors: adapts slowly to stim & continues to produce APs over the duration. Conveys info about duration of stim. Some are permanently active. Examples of tonic receptors are pain, joint capsule, and muscle spindle.
phasic receptor is a sensory receptor that adapts rapidly to a stimulus. The response diminishes very quickly & stops. not duration info; instead info on rapid change in intensity & rate
Free nerve endings characterize the nociceptors and thermoreceptors and are called thus because the terminal branches of the neuron are unmyelinated and spread throughout the dermis and epidermis.
Encapsulated receptors consist of the remaining types of cutaneous receptors. Encapsulation exists for specialized functioning.
Specialized like chemoreceptors in taste/ smell, photoreceptors in sight and hair cells for sound
sensory signals are converted to electrical by depolarization of the receptor.
Distinguish between somatic and special senses
Somatic Senses: touch based, free or encapsulated nerve endings. Receptors associated with the skin, muscles, joints, and viscera make up the somatic senses.
Special Senses: These include the senses of smell, taste, hearing, static equilibrium, dynamic equilibrium, and sight. have special receptors
pigments that undergo a chemical change when they absorb light. photopigment, rhodopsin, has two main parts: an opsin, which is a membrane protein and retinal, a molecule that absorbs light. When light hits a photoreceptor, it causes a shape change in the retinal activating the opsin
- A large degree of processing of visual information occurs in the retina itself.
- Photoreceptors in the retina tonic activity even when not stim. Absence of light, bipolar neurons that connect receptor to ganglion cell inhibit rs and cs. Exposure to light hyperpolarizes r&c, removing inhibition of their bipolar cells. bipolar cells in turn stimulate the ganglion cells, which send APs along their axons (which leave the eye as the optic nerve).
The cornea and the lens bend light to focus the image on the retina; the iris and pupil regulate the amount of light entering the eye. The aqueous humour maintains the convex shape of the cornea; the vitreous humour supports the lens and maintains the shape of the entire eye.
superior colliculus in midbrain, where eye movements are coordinated and integrated with auditory info. (info from retina)
suprachiasmatic nucleus (SCN) of the hypothalamus. The SCN is a cluster of cells that is considered to be the body's internal clock, which controls our circadian (day-long) cycle. (info from retina)
Explain what “antagonistic control” means
- both have 2 efferent series connected by ganglion.
- Sympathetic preg are shorter b/c ganglia located along the spine (thoracic & lumbar) & post g. longer.
- parasympathetic ganglia located in target tissue:pre-g are longer & post g are shorter from brain stem /sacrum,
- Both divisions use acetylcholine for the pre.g. nts
- symp uses norepinephrine as the post-g. nts
-parasympuses actylcholine at the target tissues.
Neurotransmitter molecules are either enzymatically degraded or naturally dissociate and are taken back into the presynaptic terminal (reuptake).Failure of these steps prolongs the action of the neurotransmitter. the effects of failure would depend on where it is occurring, but basically it would cause there to be a continuing signal of stimulus when there shouldn’t be, causing the information passed to be incorrect/ out of proportion to what is necessary.
Increases contrast b/t activated receptor field & nearby inactive fields. If stim activates four primary neurons, each will activate their secondary neurons. The secondary closest to the stim (recieving most AP stim) suppresses the response of the others while allowing its own signal to proceed. Greater contrast b/t center & sides of the receptive field & more precise location of stim. must receive enough more stim than inhibition for signal. Like horizontal cells in the retina
type (modality), intensity, location, and duration
M: we have specific receptors & related path
Receptor send impulses in patterns about the intensity of a stimulus (eg, how loud a sound is).
loc of receptor gives loc of stim & pttn of activated & either not or lat inhibited converys borders info
duration of stim - firing patterns & length of time. constant stim can -> habituation.
- more densely packed with photoreceptors (specifically cones)
- The pupil/ iris control how much light enters the eye & light is focused mostly by the lens + cornea: on the retina, and in particular, centrally on the fovea.
- greater density of ganglion cells. elsewhere in the retina there is lots convergence, in fovea one or few cones will send information to the ganglion cell which allows it to be highly sensitive to details.
How does the stretch reflex protect a muscle?
Stretching of the muscle activates, via spindle receptors, the stretch monomynaptic reflex: causes contract & inhibits antag muscles. sensitive not only to stretch but also speed. the muscle being lengthened to a particular point causes the spindle receptors to react sending a signal to the spinal cord which reacts causing contraction of the muscle and synergistic muscles and relaxation of antagonists.
prevent over extension or tearing. protecting it from being pulled forcefully or beyond a normal range.
1. receptor at the end of sensory neuron react to a stim
2. The sensory (afferent) neuron conducts nerve impulses along afferent pathway towards CNS.
3. integration center consists of 1+ synapses in the CNS.
4. A motor (efferent) neuron conducts impulse along efferent pathway from integration center to an effector.5. An effector responds to the efferent impulses by contracting (if the effector is a muscle fiber) or secreting a product (if the effector is a gland)
Explain the events leading up to a skeletal muscle twitch, starting with the arrival of neurotransmitter in the neuromuscular junction. through Calcium entering cytoplasm
somatic motor neuron. release ACh at neuromusc junct
Net entry of Na+ through ACh receptor-channels initiates muscle action potential
Action potential propagates down t-tubule and alters the confirmation of DHP receptor
DHP receptor opens RyR Ca2+ release channels in SR. Ca2+ enters the cytoplasm
Ca2+ binds to troponin, allowing actin-myosin binding
myosin head executes powerstroke
actin filaments slide towards center of sarcomere
sarcoplasmic Ca2+-ATPase pumps Ca2+ into SR
Tropomyosin re-covers binding site. When myosin heads release, elastic elements pull filaments back to their relaxed poison
Describe the muscle condition called tetanus. Is this a normal or a pathological event? If it is normal, what is the function? If it is pathological, what is the cause? The bacterium Clostridium tetani causes a disease called tetanus or lockjaw; you may have been vaccinated against tetanus, especially if you ever had hospital treatment for a skin wound. Speculate on whether or not the name of this disease is related to the muscle condition and why can be fatal.
- tetanic contractio is normal event skeletal muscle. receive signal to contract before first completely carried out.allows summation- if enough sent muscle can remain in steady state of max contraction.
- caridac cells have long refractory period preventing this, disease unlikely to effect heart because cardiac muscle doesnt do tetany regardless of stim
- Tetanus, cause by a neurotox from bacteria. blocks the release inhib nts so muscle is stim again and again to contract. generally starts in the jaw could be fatal
- identifying features of cardiac muscle;
- connect individual heart muscle cells to work as a single functional organ.
- consist for the most part of mixed type adherens junctions,
- nervous: decline in nerve stim (esp strong contractions at upper limit of ability to gen force/ nerve sustain high frequency stim
- metabolic: decline in contraction due to chem inhibition
aerobic: conditions of high oxygen availability, involves extended periods of exercise at levels below maximal contraction strength, and uses a high percentage of Type I muscle fibers.
anarobic: or physical activity (low avail oxy), high intensity contractions for short periods, Type II muscle fibers.(more lactic acid levels)
strength is primarily anaerobic (weight lifting and sprinting - type II, fast twitch fibers),
main functions of musculoskeletal system (5)
form, support, protection, stability, body movement
Super basic movement proteins
tropomyosin (covers actin binding sites) and troponin change shape and remove tropomyosin from binding sites) prevent myosin from binding to actin while muscle is in resting state
define sarcoplasmic reticulum
smooth ER found in smooth and striated muscle - contrains lots of calcium which it sequesters and releases when muscle cell is stimulated (RyR channels in both types, IP3 in smooth only let Ca out)
large family of motor proteins found in eukaryotic tissues, allowing mobility in muscles
thick filaments. not just for muscles. diff forms set speed muscle. 2 proteins wrapped togeth. the heavy chain has 2 binding sites - i atp, 1 for binding to actin. two chains have heads, link to molecule at hinge
A globular structural protein that polymerizes in a helical fashion to form an actin filament (or microfilament). & thin fil. 2 chains wrapped - like the train tracks for myosin, myosin controls the action
Thin filaments are composed of actin, tropomyosin, and troponin. Thin flilaments, attached to a protein in the Z disc called alpha-actinin, occur across the entire length of the I band and part way into the A band.
myosin filaments central region of the A band that contains only thick filaments, called the H zone. The middle of the H zone has a vertical line called the M line, at which accessory proteins hold together thick filaments.
cylindrical organelles, found within muscle cells, that are the contractile unit of muscles
bond between the globular head of a myosin molecule and the actin filament, repeatedly formed during muscle contraction to draw it into the A band of a sarcomere
Troponin and tropomyosin base function
start and stop actin/myosin muscle contraction.
Calcium signal acts on Troponin to move tropomyosin
tropomyosin covers site on actin that myosin binds to must move to initiate muscle fiber powerstroke
ATP prepares myosin for binding with actin by moving it to a "cocked" position. ATP must bind to myosin to break the cross-bridge and enable the myosin to rebind to actin at the next muscle contraction
more cross-bridges, the more tension, amount of tension depends on the cross-sectional area of the muscle fiber and the frequency of neural stimulation. Maximal tension occurs when thick & thin overlap to the greatest degree in sarcomere; more motor neurons stim, more myofibers contract, and greater tension in muscle
- stabilize position of contractile filaments
- molecular spring responsible for passive elasticity. - helps muscle recoil after stretch
- actin-binding protein localized to thin filament of sarcomeres in skeletal muscle.
- helps align actin
smooth muscle - calcium binds to...
A contraction that generates enough force to move a load is known as ________, whereas one that generates force that equals the load is known as ________.
rapidly conduct action potentials to the interior of the muscle fiber
brief period of time between the beginning of the action potential in the muscle and the beginning of contraction is referred to as the
During heavy exercise, the ATP requirements of active muscle are likely to be met by metabolism of
_______ is the backup energy molecule that can be rapidly converted to ATP in active skeletal muscle
Most of the time, the parallel thick and thin filaments of the myofibrils are connected by ________ that span the space between myosin and actin molecules.
a slower response to a stimulus and sustained without fatigue.
dihydropyridine (DHP) or L-type calcium channel, voltage-sensing, ryanodine (RyR) or calcium release channel
stretch, contraction, tension, relaxation
Calcium, released by the sarcoplasmic reticulum, binds to ________ to move the ________, which allows actin to form of a ________ with myosin.
Types of movement and where integrated
reflex: simple, integrates in spine
voluntary: cerebral cortex integration (inc muscle memory - can improve, become involuntary)
rhythmic movement - combo reflex/ voluntary. central pattern generators maintain. started cerebellum but spinal cord continues the movement
Describe the unique features of muscle cells
- fast/ type 2 (fast contractions, short duration),
- oxidative fibers (rely on aerobic respiration, inc slow twitch, muscles with long contraction duration - endurance),- glycolytic fibers (rely on glycolysis and include fast twitch fibers, fast muscle contractions, short duration)
List the steps involved in contraction of smooth muscle
Triggered be removal of Calcium from the cytosol
myosin phosphatase removes phosphate from myosin.
- cells break down, as do release calcium stored in SR
signals contraction steps leading to tight binding and rigor state,
- need atp to stop it (atp must bind to myosin to release cross bridge to actin allowing relaxation), will run out of ATP because dead.
- rigor mortis stops when muscles break down more and fibers no longer work
no sarcomeres (a & m aligned by dense bodies)
more plentiful actin, less myosin but larger & entire has heads, no troponin
extensive cytoskeleton (intermediate filaments- connect dbs, dense bodies - align actin & myosin)
sarcoplasmic reticulum less organized and diff
no t-tubules (smaller, dont need have caveoli)
calcium binds to calmodulin (not tropoinin)
calmodulin plus ca - complex activate myosin light chain kinase
myosin light chain kinase phosphorolates myosin - stim atpase action to initate power stroke
can adjust sensitivity -myosin light chain phosphotase removes phosphate (opposite kinase - makes less likely to power stroke)
calcium from SR but also extracellular CA
autonomic control, not somatic motor neurons
variable amts of Ca can enter -> graded contraction
more types of calcium channels: in sr: ryr channels but also IP3 receptor channels
cell surface Ca channels can be voltage, ligand or stretch/ mechanically activated so any of these signals can initate contraction
Slow twitch muscles fibers are designed for endurance as well as strength.
The fast twitch muscles are for explosive power. - stronger contraction but faster fatigue
- Fast twitch fiber persons tend to have large muscles, sprinters virus a marathoner.
- Fast twitch fibers are anerobic while slow twitch are mainly aerobic.
- Slow twitch are classified as type I.
Slow-twitch fibers have a very good blood supply- red fibers- ensures that slow-twitch fibers receive a large amount of oxygen, which allows them to work for a long time before becoming fatigued.
Fast Twitch -white fibers- less blood results in relative oxygen restriction, so fast-twitch fibers tend to fatigue much faster than the better oxygenated slow-twitch fibers.
motor neuron action potential
muscle action potential
muscle contraction mediated by calcium release
Together are a twitch - (fast or slow twitch - determined by length of time takes to get from step 2 to step 3)
latent period between muscle action potential and muscle contraction - mediated by time it takes for ca to be released from SR and initiate contraction
one motor neuron and all associated muscle fibers (one neuron can control a bunch of muscle fibers but not other way) (fine motor: fewer fibers per neuron)
- all fibers in motor unit will be same type (fast or slow twitch)
CNS intrgration of sensory info into involuntary response ( many involve negative feedback, some have feedforward - anticipation)
ALL integrated at spinal cord
monosynaptic - efferent activated (response to stim), synapse directly onto somatic motor neuron to effect skeletal muscle
polysynaptic LIKE efferent by stim, synapse onto interneuron which synapses onto motor neuron to control skeletal muscle
most stim by proprioceptors (skeletal muscle, joint and ligaments),
also nociceptors (pain) - integrate at spinal cord (cns),
stim efferent, travel to spine, (possible interneuron/s) Somatic motor neuron carry output signal to contractile muscle(s) aka extrafusile muscle fiber
muscle spindle - non contractile muscle fiber - propriceptor about degree of stretch of muscle.
have myofibrils at ends, middle more like sensory cell percieving amt ends are stretched- more stretch more action potentials
*muscle stretch -> increased afferent signals to -> spinal cord -> increased efferent output through motor neurons -> muscle contracts -> firing rate of spindles decreases
Glycogen, through conversion to glucose-1-phosphate via the process of glycolysis, produces a minimal amount of ATP. The end product of the pathway, particularly in the absence of oxygen, is lactic acid. This pool of ATP is used in the absence of oxygen, and thus the ability to produce ATP by way of cellular respiration.
(in mitochondria) provides ATP, requires oxygen
following anaerobic respiration, cellular respiration converts lactic acid to glycogen, thus restoring the pool for short-term muscle contraction.
Carbohydrates and glycogen contribute significantly more to reactions producing ATP. (opposite lots of exercise effects)
drawback being byproduct of lactic acid!
- Breakdown/ use of glycogen is decreased, (decreasing lactic acid)
- muscles conditioned by chronic loading preferentially use creatine phosphate stores first, and at a faster rate,
- cellular respiration shifts from sugars to fatty acids,
increases the expression of the enzymes involved in fatty acid activation, translocation, and oxidation leading to an increased rate of fatty acid oxidation.
Slow-twitch fibers have a high number of mitochondria, which provide them with an almost limitless amount of energy. Combined with their high blood supply, slow-twitch muscle fibers are ideally suited to long, endurance-type activities.
On the other hand, fast-twitch fibers have considerably fewer mitochondria and, as a result, fatigue far quicker than their slow-twitch counterparts.
Fast-twitch muscle fibers have a larger diameter and have greater growth potential. greater force Fast-twitch fibers are best suited to high-intensity but short-duration.
Slow-twitch fibers smaller in diameter and are far less powerful. While they cannot generate large amounts of force, they can generate low amounts of force for long periods of time. best suited to endurance activities
Fast-twitch fibers: existing ATP (maybe 10secs) and glycogen - results in the production of the fatiguing waste product lactic acid.
slow-twitch fibers use mixture of glycogen and fats for energy. The lower the intensity of the activity, the greater the amount of fat used. As intensity levels rise, fat metabolism decreases while carbohydrate metabolism increases.
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