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What is receiving sensory input?

What is receiving sensory input?

Description

School: Florida State University
Department: Physical Education Theory
Course: Functional Anatomy and Physiology I
Professor: Arturo figueroa-galvez
Term: Summer 2016
Tags:
Cost: 50
Name: Unit 2 Study Guide for Exam 2
Description: This is the study guide for Exam 2. Lots of information and explanations for understanding the concepts of muscular and nervous systems.
Uploaded: 10/13/2016
12 Pages 286 Views 8 Unlocks
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Exam II Study Guide 


What is receiving sensory input?



Functional Anatomy and Physiology 

All red font is Dr. Figueroa's outline, all black font is information from my notes  and for studying purposes. 

Make sure that you study the processes (eg. how a nerve travels from  the brain to the spine and back) very thoroughly...know what  everything is called, the hierarchy of systems and components of the  systems, as well as how they interact as a whole. Dr. Figueroa really  stresses that we understand the concepts, not just memorize them; I  would recommend using this guide as an outline, understanding the  content, and mock-teach a friend or yourself in the mirror. (: Good  luck!!

Nervous System

∙ Nervous system

o Sensory input, Integration, Motor Output


What is maintaining homeostasis?



1. Receiving sensory input. Monitor internal and external stimuli

2. Integrating information. Brain and spinal cord process sensory input and initiate responses 3. Controlling muscles and glands (skeletal muscles specifically)

1. Maintaining homeostasis. (Regulate and coordinate physiology)

o Central and Peripheral

CNS = brain and spinal cord

PNS = cranial nerves (brain, 12) and spinal nerves (nerves that are connected to the spinal column, 31) ∙ Peripheral Nervous System

o Sensory & Motor

▪ Somatic Fibers

▪ Visceral Fibers


What is integrating information?



Sensory (afferent): sensations/sensitive...pain, smell, vision, etc.; origin of these sensations are the  receptors in our bodies; transmits action potentials from receptors to CNS

▪ somatic fibers: impulses from skin, skeletal muscles, and joints to the brain

▪ visceral fibers: impulses from visceral organs to the brain If you want to learn more check out What is a satellite footprint?

Motor (efferent): means motion; stimulate contraction of the skeletal muscle; transmit action potentials  from CNS to effectors

o Motor Division

▪ Somatic Nervous System

▪ Autonomic Nervous System

o Neurons (Nerve Cells)

▪ Structure  

∙ Cell body, axon, dendrites, axon hillock, axonal terminals

o Functions

▪ Neurotransmitter

▪ Function of Neurons

▪ Myelin Sheath

∙ Structure and Function

▪ Unmyelinated Axons

∙ Neurons: functional unit of nervous system that receive stimuli and transmit action potentials;  electrical excitability; more mass in soma, less mass in axons

o cell body/soma: single nucleus with prominent nucleolus

▪ nissl substance/chromatophilic substance/ rough ER- site of protein synthesis o dendrites: input

▪ short, often highly branches

▪ receptors

▪ sendritic spines- little protuberance where axons synapse with dendrite

o axons: output Don't forget about the age old question of What happened at the boston tea party?

▪ can branch to form collaterals

▪ initial segment- beginning of axon

▪ trigger zone- site where action potentials are generated; axon hillock and part of  an axon nearest cell body

▪ synaptic vesicles

▪ presynaptic terminals- what causes the muscle contraction (if neuromuscular) ▪ axoplasm Don't forget about the age old question of What are the kinds of probabilities?

▪ axolema

∙ The Action Potential

o Resting Membrane Potential

o 1.Depolarization

o 2. Repolarization

o 3.Hyperpolarization

o Ionic Events

∙ Action potentials: (1) sensory receptors- PNS via action potentials, (2) sensory neurons- PNS on  dorsal spinal cord, (3) interneuron- axon terminals with vessicles with neurotransmitters at  presynaptic neuron, (4) postsynaptic neuron- send signal to cortex/thalamus, (5) upper motor  neuron- send signal to muscles in hand, (6) presynaptic central motor neuron- synapse in motor  neurons beforehand motion, motor because movement, central because CNS in spine, (7)  neurotransmitters will release and bind to receptors in post synaptic neuron, (8) stimulation  causes motion across skeletal muscles (neuromuscular junction) We also discuss several other topics like What are the three functions of the prefrontal cortex?

∙ Resting membrane potentials (electrical charge):

o Gated ion channels- for facilitated diffusion of sodium

▪ charge inside resting cell is negative caused by the proteins in the cytoplasm ▪ charge of membrane outside the cell is positive produced by a high  

concentration of sodium

▪ resting membrane potentials for each cell varies

o Voltage gated channels- for potassium

o polarization- electrical charge becomes either positive or negative; usually caused by  sodium...moving from high to low = facilitated diffusion by using gated-channel proteins  after Ach (comes from axon terminal) opens the gate

o depolarization- potential difference becomes smaller/less polar; more positive

▪ Depolarization- If extracellular concentration of K+increases: less gradient  between inside and outside.  

o hyperpolarization- potential difference becomes greater/more polar; more negative ▪ Hyperpolarization- If extracellular ion concentration decreases: steeper  gradient between inside and outside.  We also discuss several other topics like What is table d’hôte menus?

∙ Resting potential exists because:

1. concentration of ions different inside & outside

▪ extracellular fluid rich in Na+and Cl– We also discuss several other topics like Who is amerigo vespucci?

▪ cytosol full of K+, organic phosphate & amino acids

2. membrane permeability differs for Na+and K+ 

▪ 50-100 greater permeability for K+ 

▪ inward flow of Na+can’t keep up with outward flow of K+ 

▪ Na+/K+pump removes Na+ as fast as it leaks in

∙ The movement of the action potential is called propagation

∙ Number of potentials produced per unit of time to a stimulus (simply memorize these...) o Threshold stimulus: causes a graded potential that is great enough to initiate an action  potential.

o Subthreshold stimulus: does not cause a graded potential that is great enough to  initiate an action potential.

∙ Myelinated sheaths increase the speed of some neurons. It is a phospholipid that allows for a  faster propagation for the action potential.  

∙ Un-myelinated axons are just regularly transmitted propagations of action potentials o Peripheral = soma of that neuron is in the spinal cord (even this is in the CNS...spinal  cord and brain...the soma are outside of the spinal cord, so it's still peripheral) o Neuromuscular junction = communication between muscles and the neurons ∙ Rate of impulse propagation is determined by:

o Axon diameter – the larger the diameter, the faster the impulse

o Presence of a myelin sheath – myelination dramatically increases impulse speed ∙ Axons of the Central Nervous System

o Tracts

∙ somatosensory cortex- most external area in the brain; "somato" = body ▪ Know how to identify the origin and insertion of the spinal tracts

▪ "spinothalamic tract" ---> from the spine to the thalamus in the CNS (know the  identification of the meaning of the names (lateral corticospinal tract...cortex to  spinal cord in CNS) not their function or any details like that)

∙ Synapses

o Presynaptic and Postsynaptic Neurons

o Synaptic Cleft

o Ca2+ at axon terminal

o Neurotransmitter binding to postsynaptic neuron

o Removal of neurotransmitter

∙ Types of cells in synapse:

o presynaptic releases neurotransmitters

o postsynaptic elicits the response

∙ neurotransmitters produced in soma and stored in the presynaptic terminals to cause action  potentials

∙ ACh is really the only neurotransmitter needed for the test (norepinephrine will be on exam 3) o Enzymatic degradation:

▪ ACh: acetylcholinesterase splits ACh into acetic acid and choline. Choline  recycled within presynaptic neuron.

▪ 2 components: (1) acetate & (2) choline

▪ together they stimulate the receptor

▪ if they are separated, there would be no effect (see step 3)

▪ if ACh is inactive, the response is also inactivated in the cell

▪ ACh produced in the soma

∙ Neurotransmitters are excitatory in some cells and inhibitory in others

o a depolarizing postsynaptic potential is called an EPSP

▪ it results from the opening of ligand-gated Na+channels

o an inhibitory postsynaptic potential is called an IPSP

▪ it results from the opening of ligand-gated Cl–or K+channels

▪ it causes the postsynaptic cell to become more negative or hyperpolarized o the postsynaptic cell is less likely to reach threshold

∙ Inhibitory Synapses  

o Its effect (K+, Cl-, and hyperpolarization as the only electrical event).

∙ Is hyperpolarization the only electrical event in the cell?

∙ No. This is part of the re-polarization which is part of the stimulation; when we re-polarize, we  stimulate and activate the cell. Hyperpolarization is the consequence of trying to restore the  negative charge to the cell, and is part of the process.

o Hyperpolarization = more negative than the resting membrane potential ∙ Neurotransmitters are excitatory in some cells and inhibitory in others

o a depolarizing postsynaptic potential is called an EPSP

▪ it results from the opening of ligand-gated Na+channels

o an inhibitory postsynaptic potential is called an IPSP

▪ it results from the opening of ligand-gated Cl–or K+channels

▪ it causes the postsynaptic cell to become more negative or hyperpolarized o the postsynaptic cell is less likely to reach threshold

∙ In the heart muscle, ACh is inhibitory

o When we excite the cell, the resting membrane becomes less negative/ more positive  until an action potential is stimulated after the threshold is passed (depolarization -->  repolarization (hyperpolarization) )

o in the heart, hyperpolarization occurs, but this is different!

▪ this is the ONLY electrical event, causing inhibition of the cell...in this case the  cell is the heart, and if the heart is inhibited, then it will contract with less force,  the heart rate will decrease

o potassium leaves, chlorine enters

∙ In skeletal muscle, ACh is inhibitory, but the receptor is different

o depends on the receptor

Central Nervous System

∙ Central Nervous System Components

o Brain and Spinal Cord

∙ brain stem- beginning of the spinal cord that contains the cranial nerves

o three areas: mid-brain at top, pons in between, and medulla on the bottom ∙ Cerebral Cortex

o Motor Areas, Sensory Areas

o Primary Motor Cortex

▪ Voluntary Movement

▪ Motor Homunculus

∙ Understand Proportion Concept

▪ Somatic Motor Pathway

o Motor Tracts

▪ Pyramids

▪ Decussation of pyramids

∙ There are areas in our body that are more sensitive than others; most sensitive areas are the  hands (mainly fingers) and the lips because they have more receptors in the brain ∙ your face has more control over contraction than the muscles of the legs because of the amount  of neurons in the brain of the respective areas

o the face has small motor units that allow for more precise movements

∙ stimulation of motor neurons in CNS will bring action potentials to the spinal cord ∙ 80% of left brain refers to the right side of the body, and 20% remains referred to the left side  (opposite is true of the right brain); the crossing over sections of the left and right axons is called  decussation of pyramids in the brain stem, medulla oblongata

∙ cervical spinal cord = muscles of the arm

∙ lumbar area = muscles of the legs

∙ Motor homunculus refers to the diagram of the cross-section of the brain that explains which  parts of the somatosensory cortex are responsible for motor function in various parts of the  body; more of the brain controls facial expression than leg movements

∙ Skeletal muscles are innervated by lower motor neurons, located in either the spinal cord or the  brainstem (somatic)

∙ Axons of lower motor neurons travel via either spinal nerves or cranial nerves to reach the  muscles they innervate (somatic)

o Cranial reflexes are integrated in the brainstem

o Spinal reflexes are integrated in the spinal cord

o Somatic reflexes have responses involving skeletal muscles

o Autonomic reflexes involve internal processes, and are usually not consciously perceived ∙ Corticospinal Pathway

o Function

o Pathway

∙ Peripheral Distribution of Spinal Nerves

o How signals are sent and received to and from the spinal cord

∙ Crossing Over

o Axon in anterior corticospinal tract pathway

∙ The Direct (Pyramidal) System

∙ Direct motor pathways descend from the cerebral cortex to lower motor neurons o Lateral corticospinal tract

o Anterior corticospinal tract- This pathway carries information for pain, temperature,  itch, and tickle sensations

▪ First-order neurons travel to the spinal cord and synapse in the posterior gray  horn

▪ Second-order neurons cross to the opposite side of the spinal cord, then ascend  in the spinothalamic tract to the thalamus

▪ Third-order neurons project from the thalamus to the cerebral cortex

o Posterior Column Pathway- This pathway carries information from touch, vibration, and  proprioceptors  

▪ First-order neurons travel via the posterior column of the spinal cord to the  medulla oblongata

▪ Second-order neurons cross to the opposite side of the medulla, then ascend via  the medial lemniscus to the thalamus

▪ Third-order neurons project from the thalamus to the cerebral cortex

o Somatic Sensory Pathways- carry information from the body to the somatosensory  cortex, and to the cerebellum

o Sets of three neurons carry information along the pathways

▪ First-order neurons carry signals as far as the spinal cord or brainstem

▪ Second-order neurons carry signals on to the thalamus

▪ Third-order neurons travel from the thalamus to the cerebral cortex  

o CNS regions where the three neurons synapse with each other are known as relay  stations - these include the spinal cord, regions of the brainstem, and the thalamus o Corticobulbar tract

o The pyramidal tracts include both the corticospinal and corticobulbar tracts. These are  aggregations of upper motor neuron nerve fibers that travel from the cerebral  

cortex and terminate either in the brainstem (corticobulbar) or spinal  

cord (corticospinal) and are involved in control of motor functions of the body.

o The corticobulbar tract conducts impulses from the brain to the cranial nerves. These  nerves control the muscles of the face and neck and are involved in facial expression,  mastication, swallowing, and other functions.

o The corticospinal tract conducts impulses from the brain to the spinal cord. It is made up  of a lateral and anterior tract. The corticospinal tract is involved in voluntary movement.  The majority of fibers of the corticospinal tract cross over in the medulla, resulting in  muscles being controlled by the opposite side of the brain. The corticospinal tract also  contains Betz cells (the largest pyramidal cells), which are not found in any other region  of the body.

o The pyramidal tracts are named because they pass through the pyramids of the  medulla. The corticospinal fibers when descending from the internal capsule to the  brain stem, converge to a point from multiple directions giving the impression of  inverted pyramid.

Skeletal Muscle

∙ Structure of Skeletal Muscle

o Sarcolemma, sarcoplasm, tendon, epimysium, endomysium, perimysium, fascicle,  muscle fiber, myofibril

∙ Connective tissue membranes: (prefixes are the same as neurons...-mysium = muscle) o epimysium- connective tissue that covers and surrounds the whole muscle o perimysium- denser; surrounds a group of muscle fibers (fasciculus)

o endomysium- loose connective tissue with reticular fibers

▪ myocytes = muscle cells...more usually called "muscle fiber"

∙ sarcolemma: membrane of skeletal muscle

∙ sarcoplasmic reticulum: a network of membranous sacs around the myofibrils; the SR stores  calcium ions.

∙ myofibril- muscles can be broken down to this level; it is made of myofilaments: o actin or thin filaments (smaller); 2 of them; attached to the z-disk; allows the muscle to  contract and become stronger

o myosin (bigger); 1 of them; located in the center of the sacomere when muscle is  relaxed

∙ Calcium in the stored in the skeletal muscle- sarcoplasmic reticulum (thin and porous and  thicker at the ends) in the cisterna

∙ transverse tubule: where the sarcomere enters into the membrane so that the action potential  can propagate itself to release Ca from the SR to the sarcoplasm so it can bind to troponin-C,  move tropomyosin, allowing myosin to bind to the active sites, producing a muscle contraction ∙ Sarcomere

o Structure

▪ Z-disc, I band, A-band (what myofilaments are in the bands?)

▪ How it changes during contraction

∙ striated = banded; appearance of muscle (under microscope) due to light and dark banding;  smooth muscle doesn't have striations

∙ function of the sarcomere (between the z-disks that together make up striations of myofibrils) is  to contract the muscle and become shorter (move actin to the center of the muscle, taking  along with it the z-disk) and its length is shortened

∙ the dark and light band colors are caused by density of proteins/ filaments o since myosin is bigger, it is more dense; in the region of the sarcomere where we have  more myosin, it will look darker

o the opposite is true- actin is smaller and therefore less dense, so it appears lighter; 1/2  of the light band belongs to one sarcomere, and the other half belong to the band  adjacent to it

o only focus on the A band for the exam- it looks dark because of the myosin density  (more protein)- and the I band- it looks light because of the actin density (less protein) ∙ Striated appearance

o I bands: from Z disks to ends of thick filaments

o A bands: length of thick filaments

o H zone: region in A band where actin and myosin do not overlap

∙ Length of the A-band is not changing because this is the myosin...the I-bond shortens because  this is the actin moving over the myosin

o Myofilaments

▪ Actin  

∙ G-actin, tropomyosin, ,troponin, troponin regulatory subunits

∙ Actin filaments: has three components...

o most important is called G or F-actin (looks like blueberries on the slide) because it has  active sites (yellow dots on slide) which are a kind of receptor for the heads of the myosin  filaments

o tropomyosin- another stranded protein that covers the active site of the G-actin during a  relaxed state; to uncover the active sites and remove the tropomyosin we need troponin o troponin- only globular/ bulbous protein; has 3 subunits- one is attached to the G-actin, one  is attached to the tropomyosin, and one free one on the top that is the receptor for Ca+ ▪ TnI: attached to the G-actin

▪ TnC: receptor for Calcium

∙ TnT: attached to tropomyosin

▪ Myosin

∙ Tails, Heads, ATPase enzyme

∙ Myosin filaments

o myosin heads are the most important because there is an enzyme (ATPase) that helps to  release the energy from ATP that is important for muscle contraction during exercise ∙ What is important in the myosin head? An enzyme called myosin-ATPase; the ATPase takes ATP  (3 phosphates) and cuts the last phosphate, releasing the energy to complete the power stroke ∙ Contraction of Skeletal Muscle

o Sarcollema, Sarcoplasmic Reticulum, T-Tubules, terminal cisternae, triads, stimulation  via motor neurons

o Neuromuscular junction

▪ Axon terminal, ACH, Synaptic Cleft, ACH receptors, Na+/K+ pump,  

acetylcholinesterase

∙ ACh is the only neurotransmitter in the neuromuscular junction; in the sarcolemma there is an  enzyme that will deactivate ACh...acetylcholinesterase

o Steps:

1. Acetylcholine (ACh) is released from axon terminals into the synaptic cleft  

2. ACh binds to ACh receptors in the sarcolemma  

3. A muscle action potential is generated

4. ACh is broken down by acetylcholinesterase  

o if acetylcholinesterase doesn't work then the muscle is contracted for a longer time and  cramps ensue...ACh will stay bound to receptors and the sodium channel will remain  open and stimulated...this is why the enzyme is so important

o most of the ACh is produced in the soma

∙ the sarcolemma continues in the t-tube...the muscle fiber is made of myofibrils...action potentials  propagate through the t-tubule and start polarizing myofibrils in the t-tubule, which are made of  sarcomeres

∙ we store calcium in the cisternae

∙ the sarcomere had two filaments, actin and myosin; actin has 3 components: G-actin, troponin, and  tropomyosin...troponin has 3 subunits, the top is proponent C...the muscle is relaxed when the Ca+  levels in the sarcoplasm is low...high Ca+ levels in the sarcoplasm bind to troponin-C and the  muscles contract...to relax, the cisternae Ca+ is stimulated to move from high to low concentration  by facilitated diffusion (because it needs a channel)

o Excitation-Contraction Coupling

▪ Propagation of signal through muscle fiber, Ca2+ release, Troponin and  

tropomyosin interaction, myosin cross bridge, Hydrolysis of ATP, Removal of  

Ca2+, Blocking of binding site on actin

1. Myosin cross bridge

2. Working Stroke

3. ATP detaches cross-bridge

4. ATP Split to cock head  

∙ Generating an action potential:

1. An action potential (orange arrow) arrives at the presynaptic terminal and causes voltage gated Ca2+ channels in the presynaptic membrane to open.

2. Calcium ions enter the presynaptic terminal and initiate the release of the neurotransmitter  acetylcholine (ACh) from synaptic vesicles.

3. ACh is released into the synaptic cleft by exocytosis.

4. ACh diffuses across the synaptic cleft and binds to ligand-gated Na+channels on the  postsynaptic membrane.

5. Ligand-gated Na+channels open and Na+enters the postsynaptic cell, causing the  postsynaptic membrane to depolarize. If depolarization passes threshold, an action potential is  generated along the postsynaptic membrane.

6. ACh unbinds from the ligand-gated Na+channels, which then close.

7. The enzyme acetylcholinesterase, which is attached to the postsynaptic membrane, removes  acetylcholine from the synaptic cleft by breaking it down into acetic acid and choline. 8. Choline is symported with Na+into the presynaptic terminal, where it can be recycled to make  ACh. Acetic acid diffuses away from the synaptic cleft.

9. ACh is reformed within the presynaptic terminal using acetic acid generated from metabolism  and from choline recycled from the synaptic cleft. Ach is then taken up by synaptic vesicles. ∙ Action potentials and muscle contraction:

1. An action potential that was produced at the neuromuscular junction is propagated along the  sarcolemma of the skeletal muscle. The depolarization also spreads along the membrane of the T  tubules.

2. The depolarization of the T tubule causes gated Ca2+ channels in the sarcoplasmic reticulum to  open, resulting in an increase in the permeability of the sarcoplasmic reticulum to Ca2+, especially in  the terminal cisternae. Calcium ions then diffuse from the sarcoplasmic reticulum into the  sarcoplasm.

3. Calcium ions released from the sarcoplasmic reticulum bind to troponin molecules. The troponin  molecules bound to G actin molecules are released, causing tropomyosin to move, and to expose  the active sites on G actin.

4. Once active sites on G actin molecules are exposed, the heads of the myosin myofilaments bind  to them to form cross-bridges.

∙ Cross Bridge Movement

1. Exposure of active sites. Before cross-bridges cycle, Ca2+ bind to the troponins and the  tropomyosins move, exposing active sites on actin myofilaments.

2. Cross-bridge formation. The myosin heads bind to the exposed active sites on the actin  myofilaments to form cross-bridges, and phosphates are released from the myosin heads. 3. Power stroke. Energy stored in the myosin heads is used to move the myosin heads causing the  actin myofilaments to slide past the myosin myofilaments, and ADP molecules are released from the  myosin heads.

4. Cross-bridge release. An ATP molecule binds to each of the myosin heads, causing them to detach  from the actin.

5. Hydrolysis of ATP. The myosin ATPase portion of the myosin heads split ATP into ADP and  phosphate (P), which remain attached to the myosin heads.

6. Recovery stroke. The heads of the myosin molecules return to their resting position, and energy is stored in the heads of the myosin molecules. If Ca2+ is still attached to troponin, cross bridge formation and movement are repeated (return to step 2). This cycle occurs many times during a muscle contraction. Not all cross-bridges form and release simultaneously.

∙ Excitation contraction coupling- where does the excitation come from? The nerve in the axon  terminal excited by the neurotransmitter (ACh)

o first step of contraction is the binding of ACh to the receptor where sodium binds to the  gate

o then we produce the action potential and it propagates into the t-tubule

o the Ca+ moves from the cisternae into the sarcoplasm

o contraction starts at step 4 (picture on next page)

o relaxation starts with the binding of ACh to the receptor, depolarization, and inactivate  ACh via acetylcholinesterase, then Ca+ diffuses to the sarcoplasm and binds to troponin-C  so we need to remove Ca+ and send it back to cisternae of sarcoplasmic reticulum to  relax...but we always have more Ca+ in the sarcoplasmic reticulum, so to move from low  to high concentration we need primary active transport via ATP as energy (similar to  sodium-potassium pump)...if there is no ATP left (out of energy) then Ca+ will stay in the  sarcoplasm and we will suffer a cramp

o Sliding Filament Model of Contraction

o Motor Units

▪ Large and small

∙ Sliding Filament Model/Theory- myosin moves the actins because the z-disk is attached and the  length of the sacomere decreases as does the length of the muscle fiber & the whole muscle o actin slides over the myosin to create movement

∙ In a relaxed muscle, the actin and myosin myofilaments overlap slightly, and the H zone is  visible. The sarcomere length is at its normal resting length. As a muscle contraction is initiated,  actin myofilaments slide past the myosin myofilaments, the z disks are brought closer together,  and the sarcomere begins to shorten.

∙ In a contracted muscle, the A bands, which are equal to the length of the myosin myofilaments,  do not narrow because the length of the myosin myofilaments does not change, nor does the  length of the actin myofilaments. In addition, the ends of the actin myofilaments are pulled to and overlap in the center of the sarcomere, shortening it and the H zone disappears. ∙ Skeletal Muscle Twitch

o tension

∙ Muscle Twitch- muscle contraction in response to a stimulus that causes action potential in one  or more muscle fibers; some tension in the muscle will increase

o stimulus applied (electrical in the lab, action potential in the body) take time to start  increasing the tension (not immediate because we need time to stimulate the receptor,  open the gate, etc.)

o the lag phase is this time (not important for the exam)

o as the tension starts to increase and peak, it is called the contraction phase o as the tension relaxes, it is called the relaxation phase

o the whole thing is called a twitch...there is more control on a muscle contraction o this is important because of the different types of muscle fibers (T1, T2) ∙ Skeletal Muscle Contractions

o Isometric Contraction

o Isotonic Contractions

▪ Concentric and eccentric

∙ isometric- no change in length but tension increases (postural muscles of body) ∙ isotonic- change in length but constant tension; includes concentric and eccentric motions; tension will increase for all types of contractions...the tension changes a little bit but is the  same during the contraction; dynamic contractions involve movement and the length of the  sarcomere and muscle is going to change

o Energy for Contraction

▪ ATP, creatine phosphate, anaerobic glycolysis, aerobic glycolysis

▪ Sources of ATP

∙ Sources of ATP in muscles:

1. Creatine Phosphate : Creatine Phosphate --> Creatine, yields 1 ATP per creatine phosphate energy = creatine phosphate

oxygen not required

duration of energy ≤10 seconds

moderate and extreme exercise supported

2. Anaerobic Respiration- Glycolysis: Glucose --> 2 pyruvic acid (yields 2 ATP per glucose  molecule)--> 2 lactic acid

energy = glucose

no oxygen required

duration of energy ≤ 3 minutes

extreme exercise supported

3. Aerobic Respiration- Glycolysis: Glucose --> 2 pyruvic acid (yields 2 ATP) --> citric acid cycle  and electron transport chain (yields 34 ATP)

energy = glucose, fatty acids, and amino acids

36 ATP produced

supports hours of energy, resting and all exercise

∙ Muscle Fiber Types

o Type 1, Type 2b

o Speed of Contraction

o Oxidative and Glycolytic Fibers

o Be able to differentiate them by their characteristics

∙ We have to analyze time and tension when looking at different types of muscle fibers: o Slow-twitch oxidative

▪ Contract more slowly, smaller in diameter, better blood supply, more  

mitochondria, more fatigue-resistant than fast-twitch, large amount of  

myoglobin.

▪ Postural muscles, more in lower than upper limbs. Dark meat of chicken. ▪ slow increase in tension and long time to respond/ maintain tension

▪ weaker contraction, but don't fatigue easily

▪ marathon runners and other long distances

o Fast-twitch

▪ Respond rapidly to nervous stimulation, contain myosin that can break down  ATP more rapidly than that in Type I, less blood supply, fewer and smaller  

mitochondria than slow-twitch

▪ Lower limbs in sprinter, upper limbs of most people. White meat in chicken. ▪ Comes in oxidative and glycolytic forms

▪ large and fast increase in tension and short time to respond/ maintain tension ▪ stronger contraction, but fatigue easily

▪ sprinters

∙ hypertrophy- increase in muscle size/ mass

o 2 mechanisms to increase muscle mass, and only one in humans: we don't produce  more muscle fibers, we just make them grow in size

∙ atrophy- reduction in the size of muscle cells

∙ oxidative- ATP production in the cytoplasm, and in the sarcoplasm in the muscle via aerobic glycolysis

∙ yielding acetyl CoA to make 36 ATPs using oxygen from the blood (oxidative)- this happens in  the mitochondria...oxidative metabolism; anaerobic glycolysis is a net production of 2 ATPs that  yields lactic acid from glucose in the cytoplasm

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