a&p exam #3

Question 1

Describe the anatomical &functional divisions of the nervous system

Answer 1

ANATOMICAL: The central nervous system is made up of the brain and spinal cord.
The peripheral nervous system is made up of nerves that branch off from the spinal cord and extend to all parts of the body.

FUNCTIONAL: Sensory and Motor nervous system

Question 2

Identify the structure of a typical neuron and functions of each component

Answer 2

DENDRITES: receive communications from other cells

AXON: conducts electrical impulses away from the neuron’s cell body

CELL BODY: holds all of the general parts of the cell and controls all functions of cell

Question 3

functions of skeletal muscle tissue

Answer 3

PRODUCING MOVEMENT

MAINTAINING POSTURE

SUPPORTING SOFT TISSUES

GUARDING BODY ENTRANCES/EXITS

MAINTAINING BODY TEMP.

STORING NUTRIENTS

Question 4

identify the molecular components of thick & thin filaments

Answer 4

THIN FILAMENT: single thin filaments contain 4 main proteins:
F-ACTIN, NEBULIN, TROPOMYOSIN, TROPONIN

THICK FILAMENT: Each thick filament has a cone of titin and it recoils after stretching.
CONTAINS 300 MYOSIN MOLECULES MADE OF A PAIR OF MYOSIN SUBUNITS TWISTED AROUND EACHOTHER

the long tail in thick filament is bound to other myosin molecules

Question 5

identify the structural components of a sarcomere

Answer 5

A BUNDLE OF MYOSIN THAT CONTAINS THICK FILAMENTS COMBINED WITH BUNDLES OF ACTIN- CONTAINING THIN FILAMENTS

a sarcomere is a basic contractile unit of a myofibril(muscle fiber)

a myofibril consists of approx. 10,000 sarcomeres

A SARCOMERE CONTAINS PROTEINS THAT STABILIZE THE THIN AND THICK FILAMENTS. THE PROTEINS ALSO REGULATE INTERACTIONS BETWEEN THIN AND THICK FILAMENTS

Question 6

describe the organization of muscle at a tissue level

(CT SHEATHS)

Answer 6

EPIMYSIUM: a CT sheath made of collagen fibers that surrounds each each muscle.

PERIMYSIUM: surrounds each bundle of muscle fibers and divided muscle into series of compartments

FASCICLE: each compartment containing muscle fiber bundles

ENDOMYSIUM: surrounds each individual muscle cell.

MYOSATELLITE CELL: stem cells that repair damaged muscle tissue

TENDON: attaches skeletal muscle to bone

Question 7

describe what happens to the various regions of a sarcomere during muscle contraction

Answer 7

SARCOMERES SHORTEN AS THIN/THICK FILAMENTS OVERLAP
this pulls the muscle fiber closer together

interactions between thin/thick filaments are responsible for contraction

WHEN A SARCOMERE CONTRACTS, 2 LINES MOVE CLOSER TOGETHER & THE I BAND GETS SMALLER. THE A BAND STAYS THE SAME WIDTH & AT FULL CONTRACTION THE THIN FILAMENTS OVERLAP

lots of overlap

Question 8

describe what is involved with excitation contraction coupling

Answer 8

the link between the generation of an action potential in the sarcolemma & start of a muscle contraction

the action potential causes the release of ACh into the synaptic cleft which leads to excitation

the action potential travels along the sarcolemma and down the t tubules to the triads. this triggers the release of Ca2+ from the terminal cristernae of the sarcoplasmic reticulum

Question 9

summarize the events involved in the neural control of skeletal muscle

Answer 9

A SKELETAL MUSCLE FIBER CONTRACTS WHEN STIMULATED BY A MOTOR NEURON AT A NEUROMUSCULAR JUNCTION.

MOTOR NEURONS CARRY INSTRUCTIONS IN FORM OF ACTION POTENTIALS AT THE AXON TERMINAL

CONTRACTION BEGINS WHEN SARCOPLASMIC RETICULUM RELEASES STORED CALCIUM IONS INTO THE CYTOSOL OF THE MUSCLE FIBER(that release is under control of the nervous system)

AS INTRACELLULAR CALCIUM IONS ARE REABSORBED, CONTRACTION ENDS & MUSCLE RELAXATION OCCURS

Question 10

identify components of the neuromuscular junction

Answer 10

NMJ IS MADE UP OF AN AXON TERMINAL OF A NEURON, A SPECIALIZED REGION OF TGE SARCOLEMMA CALLED THE MOTOR END PLATE, AND IN BETWEEN A NARROW SPACE CALLED THE SYNAPTIC CLEFT

Question 11

outline the steps that are involved during the contraction cycle

Answer 11

calcium ions (CA2+) bind to troponin, resulting in the exposure of the active sites on the thin filaments

this allows cross-bridge formation & will continue as long as ATP is available

CONTRACTION CYCLE IS SERIES OF MOLECULAR EVENTS THAT ENABLE MUSCLE CONTRACTION

Question 12

explain the mechanisms involved in muscle fiber relaxation

Answer 12

ACh is broken down:
ACh broken down by AChE, ends action potential generation

Sarcoplasmic reticulum reabsorbs Ca2+:
As calcium ions are reabsorbed, their concentration in cytosol decreases

Active site covered, cross bridge formation ends:
without calcium ions, the tropomyosin res turns to its normal position & the active sites are covered again

Contraction ends:
* without cross bridge formation, contraction ends*

Muscle relaxation occurs:
* muscled return passively to resting length*

Question 13

discuss the factors that determine the peak tension developed during a contraction of a muscle fiber

Answer 13

FACTORS:
- number of muscle fibers activated
-frequency of neural stimulation to muscle fibers

as tension increases, calcium ions are binding to troponin active sites on thin filaments are being exposed & cross bridging interactions are occurring
^ CONTRACTION PHASE ^

Question 14

discuss the factors that affect peak tension production during the contraction of an entire skeletal muscle

Answer 14

depends on the cross sectional area of the muscle fiber & frequency of neural stimulation

Question 15

explain the significance of motor units to whole muscle contraction

Answer 15

motor units provide electrical input to a muscle in order to generate muscle contraction

a motor unit consists of a neuron & muscle cell that it supplies

the size of a motor unit indicates how precise a movement can be

Question 16

define muscle tone and it’s relationship to normal everyday activities

Answer 16

the resting tension in a skeletal muscle

muscle tone helps to hold body upright when sitting/standing

also contributes to control, speed, and amount of movement we achieve

Question 17

isotonic vs isometric contractions

Answer 17

ISOTONIC: tension increases & skeletal muscle length changes

ISOMETRIC: muscle as a whole doesn’t change length and tension produced never exceeds the load

Question 18

concentric vs. essentric in isotonic contractions

Answer 18

CONCENTRIC: muscle tension exceeds load and muscle shortens

ESSENTRIC: peak tension developed is less than the load & muscle elongates due to the contraction of another muscle or pull of gravity

Question 19

describe the mechanisms by which muscle fibers obtain the energy to power contractions

Answer 19

when muscle fiber is actively contracting, each thick filament breaks down about 2500 ATP molecules per second.

the demand for ATP in a contracting muscle fiber is so high that it would be impossible to have all the necessary energy available as ATP before the contraction begins.

Instead, a resting muscle fiber contains only
enough ATP and other high-energy compounds to sustain acontraction until additional ATP can be generated.

Throughout the rest of the contraction, the muscle fiber will generate ATP at roughly the same rate as it is used.

Question 20

describe the factors that contribute to muscle fatigue

Answer 20

muscle fatigue means muscle can’t preform required level of activity

• DEPLETION OF METABOLIC RESERVES WITHIN MUSCLE FIBER
• DAMAGE TO SARCOLEMMA AND SARCOPLASMIC RETICULUM

-DECLINE IN pH WITHIN MUSCLE FIBERS

-SENSE OF REDUCTION IN DESIRE TO CONTINUE ACTIVITY

Question 21

discuss the stages of mechanisms involved in muscle recovery

Answer 21

after moderate activity, muscles need several hours to recover.

LACTATE REMOVAL & RECYCLING

OXYGEN DEBT:
* happens when the body can no longer distribute oxygen to muscle cells to aid the processes that make them function, resulting in muscular fatigue*

HEAT PRODUCTION & LOSS:

Question 22

relate the type of muscle fibers to muscle muscle performance

Answer 22

FAST FIBERS: reach peak twitch tension in 0.01 seconds and is prevalent in quick and powerful movement such as sprinting/ weight lifting

SLOW FIBERS: takes 3 times as long to reach peak tension after stimulation but is prevalent in long distance running

INTERMEDIATE FIBERS: BETWEEN FAST AND SLOW FIBERS

Question 23

distinguish between aerobic vs anaerobic endurance and implications for muscle performance

Answer 23

AEROBIC: length of time & muscle can continue to contract with while supported by mitochondrial activities. -does not promote hypertrophy

ANAEROBIC: length of time & muscular contraction can continue to be supported by existing energy reserves of ATP & CP & by glycolysis

Question 24

classify neurons based on structure

Answer 24

MULTIPOLAR: more than 2 processes, single axon, and multiple dendrites

UNIPOLAR: single elongated process, cell body off to the side

BIPOLAR: 2 processes separated by cell body

Question 25

describe how peripheral neurons can respond to injury

Answer 25

more repair is possible for PNS than CNS

1) fragment of axon& myelin occurs in distal stump

2) schwann cells form cord, grow into cut & unite stumps. macrophages engulf degenerating axon & myelin

3) axon sends buds into network of schwann cells that starts growing along cord of schwann cells

4) axon continues to grow distal stump and is enclosed by shwann cells

Question 26

explain how resting potential is created and maintained

Answer 26

potassium that leaks from inside of the cell to the outside via leak potassium channels & generates a negative charge in the inside of membrane vs. outside.

MAINTAINED: sodium potassium pumps move 2 potassium ions inside the cell as 3 sodium ions are pumped out to maintain negatively charged membrane inside the cell

Question 27

identify various types of gated channels found in neuron plasma membranes & where they can be found

Answer 27

CHEMICALLY GATED ION CHANNEL: found on densities and cell body of neuron. open/close when they bind specific chemicals

VOLTAGE GATED ION CHANNEL: found in axons. open/close in response to changes in membrane potential

MECHANICALLY GATED ION CHANNEL: found in sensory receptors. open/close in response to physical distortion of membranes/surfaces

Question 28

describe how graded potential is generated & describe factors which can keep it from beginning an action potential

Answer 28

GRADED POTENTIAL: changes in the membrane potential that can not spread far from the site of stimulation

any stimulus that opens a gated channel produces a graded potential

if a graded potential causes hyperpolarization an action potential becomes less likely

Question 29

differentiate between the absolute refractory period and the relative refractory period

Answer 29

ABSOLUTE: 1st part of refractory period. period of time during which no amount of external stimulus will generate an action potential

RELATIVE: begins when sodium ion channels regain their normal resting conditions. only a large stimulus will generate an action potential

Question 30

duchess the events that occur at a chemical synapse

Answer 30

action potential triggers the pre synaptic neuron to release neurotransmitters

where 1 neuron finds chemical signals to another cell, often a second neuron. every chemical synapse involves 2 cells

Question 31

discuss the factors involved in synaptic delays and synaptic fatigue

Answer 31

DELAY:
occurs between arrival of action potential at the axon terminal and the effect on the postsynaptic membrane.

due to time necessary for transmitter to be released. diffuse across the cleft and bind with receptors on postsynaptic membrane

FATIGUE: occurs often, response of the synaptic weakens until ACh has been replenished. temp. depletion of synaptic vesicles that house neurotransmitters in the synapse

Question 32

structural vs. functional differences between skeletal muscle fibers & smooth muscle cells

Answer 32

SMOOTH MUSCLE CELLS
structure: relatively long, slender, spindle shaped cell, centrally located nucleus, no t tubules

function: contracts 4x greater than skeletal muscle fibers. triggers 4 contractions appearance free calcium ions in cystoplasm

SKELETAL MUSCLE FIBERS:

structure: thousands of muscle fibers wrapped in sheath, fascicle

function:allows muscles to move bones to preform lots of movements

Question 33

classify neurons based on function

Answer 33

motor neurons

sensory neurons

interneurons

Question 34

discuss the role that smooth muscle tissue plays in systems throughout the body

Answer 34

coordinates movement of substances through internal passageways

Integumentary System: helps regulate the flow of blood to the superficial dermis

• Cardiovascular System: control blood flow through vital organs and help regulate blood pressure.

-Respiratory System: contract or relax to alter
the diameters of the respiratory passageways and change their resistance to airflow.

Question 35

structural vs functional differences of skeletal muscle fibers and cardiac muscle cells

Answer 35

CARDIAC MUSCLE CELLS:
Structure: found only in heart, relatively small, single nucleus, typically branched

Function: contractions last 10 times longer than skeletal, longer refractory periods and do not readily fatigue

SKELETAL MUSCLE FIBERS:

structure: unbranched

function: action potential triggers release of calcium from SR& contraction of sarcomeres

Question 36

discuss the factors involved in synaptic delay & synaptic fatigue

Answer 36

SYNAPTIC DELAY: occurred between arrival of action potential at the axon terminal & the effect on the postsynaptic membrane. Delay is due to time necessary for transmitter to be released, diffuse across the cleft & bind w/ receptors in post synaptic membrane

SYNAPTIC FATIGUE: occurs after, response of the synapse weakens until ACh has been replenished temp. depletion of synaptic vesicles that house neurotransmitters in the synapse

Question 37

factors that affect the speed w/ which action potentials propagated

Answer 37

• Because myelin limits the movement of ions
  across the axon membrane, the action
  potential must “jump” from node to node
  during propagation. This results in much
  faster propagation along the axon.*

A local current
produces a graded
depolarization
that brings the
axon membrane
(axolemma) at the
next node to
threshold.

An action potential
develops at
node (2).

A local current
produces a graded
depolarization
that brings the
axolemma at
node (3 to
threshold.

Question 38

discuss the factors that affect the speed w which action potentials are propagated

Answer 38

• In an unmyelinated axon, an action potential
  moves along by continuous propagation. The
  action potential spreads by depolarizing the adjacent region of the axon membrane. This process continues to spread as a chain reaction down the axon.*

As an action potential develops at the
initial segment 1, the membrane polential
at this site depolarizes to +30 mV.

A local current then develops as the
sodium lons entering at 1 spread away
from the open voltage-gated channels.
A graded depolarization quickly brings
the axon membrane (axolemma) in
segment (2) to threshold.

An action potential now occurs in
segment I while segment 2 begins
repolarization.

as the sodium ions entering at
segment (2) spread laterally, a graded
depolarization quickly brings the
membrane in segment (3 to threshold,
and the cycle is repeated.

Question 39

describe the events involved in the generation and propagation of an action potential

Answer 39

if graded potential causes depolarization, action potential becomes more likely to occur

Depolarization to Threshold

The stimulus that initiates an action
potential is a graded depolarization large
enough to open voltage-gated sodium
channels. The opening of the channels
occurs at a membrane potential known
as the threshold.

Activation of Sodium lon channels and Rapid
Depolarization

When the sodium channel activation gates
open, the plasma membrane becomes
much more permeable to Na*. Driven by
the large electrochemical gradient,
sodium ions rush into the cytosol, and
rapid depolarization occurs. The inner
membrane surface now has more positive
ions than negative ones, and the
membrane potential has changed from
-60 mV to a positive value.

inactivation of Sodium lon channels and Activation of potassium Ion Channels starts repolarization

as the membrane potential approaches
+30 mV, the inactivation gates of the
voltage-gated sodium channels close.
This step is known as sodium channel
inactivation, and it coincides with the
opening of voltage-gated potassium
channels. Positively charged potassium
lons move out of the cytosol, shifting the
membrane potential back toward the
resting level. Repolarization now begins.

Time Lag in Closing All Potassium Ion Channels Leads to Temporary Hyperpolarization

The voltage-gated sodium channels
remain inactivated until the membrane
has repolarized to near threshold level.
At this time, they regain their normal
status: closed but capable at opening.
The voltage-gated potassium channels
begin closing as the membrane reaches
the normal resting membrane potential
(about -70 mV). Until all of these
potassium channels nave closed,
potassium ions continue to leave the cell.
This produces a briet hyperpolarization.