Test 3: Muscle, Nervous, and Spinal Cord

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functions of spinal cord

integrates and processes information on its own, in addition to relaying information to and from the brain

central nervous system

spinal cord and brain

cervical enlargements

expanded regions with increased gray matter to provide innervation of the pectoral girdle and upper limbs

lumbar enlargements

expanded region of the spinal cord with increased gray matter to provide innervation of the pelvic girdle and lower limbs

conus medullaris

where the spinal cord tapers to a conical tip, which is at or inferior to the level of the first lumbar vertebrae (L1)

filum terminale

a strand of fibrous tissue, originating at the conus medullaris and extending through the vertebral canal to the second sacral vertebra, ultimately becoming part of the coccygeal ligament

dorsal root ganglia

contains sensory neuron cell bodies, each segment of the spinal cord is associated with a pair of these

dorsal root

contains the axons of the sensory neurons in the dorsal root ganglion; each segment of the spinal cord is associated with a pair of these

ventral root

contains axons of somatic motor neurons and sometimes visceral motor neurons that control peripheral effectors; each segment of the spinal cord is associated with a pair of these

spinal nerve

location where sensory and motor fibers unite, emerging from intervertebral foramina; distal to each dorsal root ganglion. is considered a mixed nerve

mixed nerve

contains both sensory and motor fibers

sciatic nerve

largest nerve in the body

cauda equina

inferior extension of the ventral and dorsal roots and the filum terminale in the vertebral canal

spinal meninges

a series of specialized membranes that provide physical stability and shock absorption for neural tissues of the spinal cord

meningeal layers

dura mater, arachnoid mater, pia mater

dural mater

tough, fibrous outermost layer of the spinal cord; caudally it forms the coccygeal ligament with the filum terminale

coccygeal ligament

formed where the spinal dura mater tapers from a sheath to a dense cord of collagen fibers that ultimately blend with components of filum terminale

epidural space

separates the dura mater from the inner walls of the vertebral canal

subdural space

internal to the inner surface of the dura mater; separates the dura from the arachnoid mater

arachnoid mater

middle meningeal layer

subarachnoid space

internal to the arachnoid mater; contains cerebrospinal fluid

cerebrospinal fluid

acts as a shock absorber and used for spinal tap

pia mater

innermost meningeal layer; bound firmly to the underlying neural tissue

denticulate ligaments

• Lateral extensions of pia mater that pass through the arachnoid layer and attach to the internal surface of the dura mater • Function to anchor the spinal cord

central gray matter

surrounds the central canal in the spinal cord and contains cell bodies of neurons and glial cells

horns

projections of gray matter toward the outer surface of the spinal cord

central canal

located on the spinal cord on the horizontal bar of the H

white matter

peripherally situated; contains large numbers of myelinated and unmyelinated axons organized into tracts and columns

nuclei

groups of neuron cell bodies in spinal cord gray matter

posterior gray horns

contain somatic and visceral sensory nuclei

anterior gray horns

contain neurons concerned with somatic motor neurons

lateral gray horns

contain visceral motor nuerons

gray commissures

posterior and anterior to the lateral canal; contain axons of interneurons that cross from one side of the cord to the other

white matter

divided into six columns (funiculi), each containing tracts (fasciculi)

vertebra sections

cervical, thoracic, lumbar, sacral

epineurium

outermost layer of connective tissue on the spinal nerve; a dense network of collagen fibers

perineurium

middle layer of connective tissue on the spinal nerve; partions the nerve into a series of bundles (fascicles) and conveys blood vessels into each individual fiber

endoneurium

inner layer of connective tissue on the spinal nerve; composed of delicate connective tissue fibers that surround individual axons

white ramus

first branch of spinal nerve in the thoracic and upper lumber region; contains myelinated axons going to an autonomic ganglion

gray ramus

exits the autonomic ganglion, carries axons that innervate glands and smooth muscles in the body wall or limbs back to the spinal nerve

autonomic nerve

nerve that carries fibers to internal organs

rami communicantes

white and gray rami, collectively

dorsal ramus

provides sensory/motor innervation to the skin and muscles of the back

ventral ramus

supplies ventrolateral body surface, body wall structures and limbs

nerve plexus

complex, interwoven network of nerves

four major nerve plexuses

cervical, brachial, lumbar and sacral plexuses

cervical plexus

consists of the ventral rami of C1-C4 and some fibers from C5; innervates the muscles of the neck, thoracic cavity and diaphragm

brachial plexus

consists of ventral rami C5-T1; innervates the pectoral girdle and upper limbs; nerves in this plexus originate from cords or trunks

lumbar plexus

contains fibers from spinal segments T12-L4; originates from the posterior abdominal wall and ventral rami of nerves supplying the pelvic girdle and lower limbs

sacral plexus

contains fibers from spinal segments L4-S4; originates from the posterior abdominal wall and ventral rami of nerves supplying the pelvic girdle and lower limbs

neural reflex

rapid, autonomic, involuntary motor response to stimuli

reflex

helps preserve homeostasis by rapidly adjusting the functions of organs or organ sytems

receptor

specialized cell that monitors conditions in the body or external environment; has a characteristic range of sensitivity

innate refelx

genetically determined reflex

acquired reflex

reflex that is learned following repeated exposure to a stimulus

spinal reflex

reflex in which important interconnections and processing occur inside the spinal cord; range from monosynaptic to polysynaptic

somatic reflex

reflex which controls skeletal muscle contractions

visceral (autonomic) reflex

controls the activities of smooth and cardiac muscles and glands

quadriplegia

loss of sensation and motor control of the upper and lower limbs

myosin

thick filaments of a muscle

actin

thin filaments of a muscle

sarcoplasmic reticulum

releases calcium

Z line

boundary of a sarcomere, point of anchor for thin actin filaments

H zone

The region at the center of an A band of a sarcomere that is made up of myosin only and gets shorter during muscle contraction.

I band

contains only thin filaments

fascicle

bundle of muscle fibers

perimysium

connective tissue covering surrounding each muscular fascicle

endomysium

connective tissue that enclose a single muscle cell

tendon

attaches muscle to bone

sarcomere

contractile unit of muscle

sarcolemma

plasma membrane of a muscle fiber

myofibril

long organelle found within muscle cell

Epimysium

connective tissue that covers the entire muscle

A band

where myosin is; dark band

Axon terminal

The endpoint of a neuron where neurotransmitters are stored.

neurotransmitter

chemical used by a neuron to transmit an impulse across a synapse to another cell

T Tubule

narrow tubes that are continuous with the sarcolemma and extend into the sarcoplasm

motor end plate

The portion of the cell membrane at the neuromusclar junction; essentially the postsynaptic membrane at the synapse.

synaptic cleft

synaptic gap or synaptic space; tiny gap between the terminal of one neuron and the dendrites of another neuron (almost never touch); location of the transfer of an impulse from one neuron to the next

synaptic vesicles

release neurotransmitters which then bind with a dendrite receptor site

acetylcholin

vesicles dump this so that the axon terminal has a way to communicate with the motor end plate.

action potential

causes a voltage charge which occurs in the plasma membrane of the neuron

motor neuron

this carries information from the brain to the muscles; also called "efferent"

acetylcholinesterase

An enzyme that breaks down the neurotransmitter acetylcholine.

terminal cisternae

enlarged areas of the sarcoplasmic reticulum surrounding the transverse tubules, which store calcium for release at the start of muscle contraction

neuromuscular junction

the junction between a nerve fiber and the muscle it supplies

aponeurosis

a sheet of fibrous tissue binding muscles together or muscle to bone

sodium potassium pump

A special transport protein in the plasma membrane of animal cells that transports sodium out of the cell and potassium into the cell against their concentration gradients.

calcium pump

Active transport protein; pumps calcium ions across a cell membrane against their concentration gradient.

tropomyosin

A helical protein that winds around actin helices in skeletal and cardiac muscle cells to form the thin filament of the sarcomere.

troponin

a smaller calcium-binding protein attached to the tropomyosin

cross bridge

The connection of a myosin head group to an actin filament during muscle contraction (the sliding filament theory).

power stroke

The step in the sliding filament theory during which myosin undergoes a conformational change to its low energy state, in the process dragging the thin filaments (and the attached Z lines) toward the center fo the sarcomere.

release/reactivate energy in myosin and active transport for calcium into terminal cisternae

ATP is used to what during muscle contractions?

latent period, contraction phase, and relaxation phase

3 phases of a muscle twitch

latent period

begins at stimulation and typically lasts 2msec and continues until calcium is released from the terminal cisternae

contraction phase

begins as Calcium bind to troponin and myosin "cross bridge" bind to actin and power strokes are occurring; lasts about 15msec

relaxation phase

Calcium is being actively transported back into the terminal cisternae causing calcium levels to fall, active sites on Actin are being re-covered by tropomyosin, and tension falls to resting levels: lasts about 25msec

treppe

repeated stimulation after relaxation phase has completed in a muscle. Can occur over the next 30-50 stimulations.

motor unit

a motor neuron and all the muscle cells it stimulates

multiple motor unit summation

The strength of a muscle contration is determinded not only by the frequency of stimulation, but also by the number and size of motor units recruited, The number of motor units that are recruited is determined by the number of motor neurons that are stimulated by the central nervous system

wave summation

increased tension resulting from increasing frequency of stimulation

Incomplete Tetanus

______is repeated stimulation of the muscle so that the muscle is never allowed to completely relax. will yield increased tension is produced

Complete Tetanus

if stimulation frequency is high enough, muscles never BEGIN to relax and is continuous contraction

isotonic or isometric

Contractions can be classified as...

isotonic contraction

involving muscular contraction in which tension increases and the muscle length changes

concentric or eccentric

isotonic contractions can be either...

concentric

contraction in which the tension exceeds the load and the muscle shortens

eccentric contraction

contraction in which tension is less than the load and the muscle lengthens

isometric contraction

tension never exceeds the load and the muscle length never changes

creatine

A substance, stored in the muscles, that helps supply energy for muscle contraction and can be taken as a supplement or created by your own body. this is a way to store ATP in the muscle.

fast fibers

white fibers; large in diameter, contain densely packed myofibrils and large glycogen reserves and relatively few mitochondria

slow fibers

red fibers; half the diameter of fast fibers and take about 3x as long to contract after stimulation; surrounded by extensive capillaries; therefore higher supply of oxygen; contain myoglobin (reserve of oxygen)

fast, slow, and intermediate fibers

Skeletal muscle contain 3 types of fibers. What are they?

intermediate fibers

combination of fast and slow fibers.

Red muscles

muscle primarly made up of slow fibers, which have endurance.

White muscles

muscle primarily made up of fast fibers, which have no endurance.

Atrophy

any weakening or degeneration (especially through lack of use)

"All or none principle"

applies to muscle fibers and motor units either it contracts or it doesn't, Either the action potential occurs or it doesn't, this is called the?

triad

2 terminal cisternae and one T-Tubule.

Astrocytes

Abundant star shaped cells found throughout the CNS, cleaning up debris in the extracellular space and removing neurotransmitters from the synaptic cleft, connects neurons to nearby cappilaries, components of the blood-brain barrier

Microglia

Spider-like phagocytes; dispose of debris, smallest neuroglial cells; phagocytic cells that enculf cellular debris, waste products and pathogens. increase in number as a result of infection or injury

Ependymal cells

Type of neuroglial cell found in the ventricles, circulate cerebrospinal fluid

Ogliodendrocytes

Produce myelin sheath around nerve fibers in the central nervous system (CNS)

Satellite cells

Protect neuron cell bodies and provide nutrition to the cell bodies

Schwann cells

Supporting cells of the peripheral nervous system responsible for the formation of myelin. Wrap around one neuron at a time

Nissl substance

specialized rough endoplasmic reticulum for the nerve

Neurofibrils

intermediate cytoskeleton that maintains cell shape, bundles of intermediate filaments (neurofilaments); maintain shape

Dendrites

conduct impulses toward the cell body

Axons

conduct impulses away from the cell body

Synaptic Cleft

gap between adjacent neurons

Synapse

junction between nerves

Nodes of Ranvier

gaps in myelin sheath along the axon

Gray Matter

cell bodies and unmylenated fibers

Nuclei

clusters of cell bodies within the white matter of central nervous system

Ganglia

collections of the cell bodies outside the central nervous system

Sensory neurons

carry impulses from the sensory receptors

Motor neurons

carry impulses from the central nervous system

Interneurons

Found in neural pathways in the central nervous system; connect sensory and motor neurons

Depolarization

a stimulus depolarizes the neurons membrane

Autonomic reflexes

smooth muscle regulation, heart and blood pressure regulation, regulation of glands, digestive system regulation

Somatic Reflexes

activaiton of skeletal muscles

Somatic sensory area

recieves impulses from the body's sensory receptors

Primary motor area

sends impulses to skeletal muscles

Protection of the CNS

Scalp and Skin, SKull and vertebral column, Meninges

Meninges

Dura mater - double-layered external covering (Periosteum and Meningeal Layer)

Periosteum

attached to the surface of the skull

Meningeal layer

outer covering of the brain

Cerebrospinal Fluid

Similar to blood plasma composition, formed by the choroids plexus, forms a watery cushion to protect the brain, circulated in the arachnoid space, ventricles, and central canal of the spinal cord

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