a&p exam #3 Flashcards
Describe the anatomical &functional divisions of the nervous system
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
Identify the structure of a typical neuron and functions of each component
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
functions of skeletal muscle tissue
PRODUCING MOVEMENT
MAINTAINING POSTURE
SUPPORTING SOFT TISSUES
GUARDING BODY ENTRANCES/EXITS
MAINTAINING BODY TEMP.
STORING NUTRIENTS
identify the molecular components of thick & thin filaments
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
identify the structural components of a sarcomere
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
describe the organization of muscle at a tissue level
(CT SHEATHS)
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
describe what happens to the various regions of a sarcomere during muscle contraction
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
describe what is involved with excitation contraction coupling
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
summarize the events involved in the neural control of skeletal muscle
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
identify components of the neuromuscular junction
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
outline the steps that are involved during the contraction cycle
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
explain the mechanisms involved in muscle fiber relaxation
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*
discuss the factors that determine the peak tension developed during a contraction of a muscle fiber
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 ^
discuss the factors that affect peak tension production during the contraction of an entire skeletal muscle
depends on the cross sectional area of the muscle fiber & frequency of neural stimulation
explain the significance of motor units to whole muscle contraction
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