Chapters 13-20 of Anatomy and Physiology
What is the role of epimysium?
Surrounds the entire muscle
What is a circular muscle?
Forms rings around body openings
What do spinal nerves innervate?
Muscles below the neck
What are somatic motor neurons?
Nerve cells serving skeletal muscles
What are muscle cells known as?
Muscle fibers (myofibers)
When does VO2 max typically peak?
Around age 20
What is a myogram?
A chart of muscle contraction timing
What are dendrites?
Branches that receive signals from other neurons
What do oligodendrocytes do?
Form myelin sheaths in CNS
What is the threshold for action potential?
About -55 mV
How many skeletal muscles does the human body have?
Over 600
What connects muscle to bone?
Tendons
What does muscle movement include?
Moving body parts and contents
What is the specialized major function of muscle tissue?
Convert chemical energy in ATP into mechanical energy
What is the significance of muscle architecture?
It relates to muscle strength and function
What percentage of body weight do muscles constitute?
About half
What are the three types of muscle tissue?
Skeletal muscle
Smooth muscle
Cardiac muscle
What is the major function of muscle tissue?
Convert chemical energy in ATP into mechanical energy
What is an example of a muscle name?
Depressor labii inferioris
How are muscles typically named?
Using Latin names based on function or location
What are the universal characteristics of muscle tissue?
Excitability (responsiveness)
Conductivity
Contractility
Extensibility
Elasticity
What does excitability in muscle tissue refer to?
Responsiveness to chemical signals and stimuli
What is the study of the muscular system called?
Myology
What are antigravity muscles responsible for?
Preventing us from falling over
What is the role of sphincters in muscle function?
Control the movement of materials within the body
What does perimysium wrap around?
Fascicles of muscle fibers
What are the functions of muscles?
Movement
Stability
Control of openings
Heat production
Glycemic control
How do muscles help with glycemic control?
By absorbing and storing glucose
How do muscles contribute to stability?
By maintaining posture and preventing unwanted movements
How much heat do muscles produce?
Up to 85% of the body's heat
What does contractility mean in muscle tissue?
Muscle fibers shorten when stimulated
What is conductivity in muscle tissue?
Local electrical excitation travels along the muscle fiber
What is extensibility in muscle tissue?
Capability of being stretched between contractions
How do muscles contribute to stability?
By maintaining posture and preventing unwanted movements
What does elasticity refer to in muscle tissue?
Returns to original length after being stretched
What are the connective tissues of muscles?
Endomysium: around each fiber
Perimysium: wraps fascicles
Epimysium: surrounds entire muscle
Fascia: separates muscle groups
What is the function of endomysium?
It allows room for capillaries and nerve fibers
Why is knowing innervation important?
It enables diagnosis of nerve injuries
How many skeletal muscles does the human body have?
Over 600
What percentage of body weight do muscles constitute?
About half
What are the common arrangements of muscle fibers?
Fusiform: thick in the middle
Parallel: uniform width
Triangular (convergent): broad to narrow
Pennate: feather-shaped
Circular (sphincters): form rings
What are the three types of muscle tissue?
Skeletal, smooth, cardiac
What happens in compartment syndrome?
Pressure builds within a muscle compartment
What is fascia in muscle structure?
Sheet of connective tissue separating muscles
What is the study of the muscular system called?
Myology
What are the types of pennate muscles?
Unipennate, bipennate, multipennate
What is a muscle compartment?
A group of functionally related muscles enclosed by fascia
How are muscles typically named?
Using Latin names based on function or location
What is one example of a muscle name?
Depressor labii inferioris
What are the functions of muscles?
Movement
Stability
Control of openings
Heat production
Glycemic control
What are the symptoms of compartment syndrome?
History of trauma, dark urine
What does muscle movement include?
Moving body parts and contents
What is the treatment for compartment syndrome?
Rest, immobilization, fasciotomy
What does innervation of a muscle refer to?
Identity of the nerve that stimulates it
How do cranial nerves differ from spinal nerves?
Cranial nerves innervate head and neck muscles
What happens to blood supply during heavy exercise?
Muscular system's share rises to over three-quarters
What are antigravity muscles?
Muscles that prevent us from falling over
What is conductivity in muscle tissue?
Local electrical excitation travels along muscle fibers
What do spinal nerves do?
Innervate muscles below the neck
How do muscles help with glycemic control?
By absorbing and storing glucose
What is the role of sphincters in muscle function?
Control the movement of materials within the body
How much heat do muscles produce?
Up to 85% of the body's heat
How much blood does the muscular system receive at rest?
24 L per minute
What are the universal characteristics of muscle tissue?
Excitability
Conductivity
Contractility
Extensibility
Elasticity
What does excitability in muscle tissue refer to?
Responsiveness to chemical signals and stimuli
How do capillaries function in muscle tissue?
They branch extensively through the endomysium
What is a fasciotomy?
Incision to relieve pressure
What does muscle breakdown release into the blood?
Myoglobin
What does contractility mean in muscle tissue?
Muscle fibers shorten when stimulated
What were the traditional terms for muscle attachments?
Origin and insertion
What is an aponeurosis?
A broad, flat sheet tendon
What does elasticity refer to in muscle tissue?
Returning to original length after being stretched
What is extensibility in muscle tissue?
Capability of being stretched between contractions
What are the common arrangements of muscle fibers?
Fusiform: thick in the middle, tapered ends
Parallel: uniform width, parallel fascicles
Triangular (convergent): broad at one end, narrow at the other
Pennate: feather-shaped
What do spinal nerves innervate?
Muscles below the neck
What is the initial treatment for muscle breakdown?
Rest and immobilization
What are the connective tissues of muscles?
Endomysium: around each fiber
Perimysium: wraps fascicles
Epimysium: surrounds entire muscle
Fascia: separates muscle groups
What is the function of endomysium?
It surrounds each muscle fiber
What do spinal nerves do after emerging from the spinal cord?
Branch into posterior and anterior rami
Where do spinal nerves arise from?
Spinal cord
What does perimysium do?
Wraps bundles of muscle fibers called fascicles
What is the role of epimysium?
Surrounds the entire muscle
What is fascia in muscle structure?
Sheet of connective tissue separating muscle groups
What characterizes parallel muscles?
Uniform width and parallel fascicles
What is a fusiform muscle?
Thick in the middle and tapered at each end
What is a plexus in relation to spinal nerves?
A web-like network of spinal nerves
Where do cranial nerves arise from?
Base of the brain
What do cranial nerves innervate?
Muscles of the head and neck
What is a triangular (convergent) muscle?
Broad at one end and narrow at the other
What are pennate muscles?
Feather-shaped muscles with angled fibers
What are the types of pennate muscles?
Unipennate: fascicles approach tendon from one side
Bipennate: fascicles approach tendon from both sides
Multipennate: bunches of feathers converge to a single point
What happens to blood flow to the muscular system during heavy exercise?
It rises to more than 11.6 L/min
What happens in compartment syndrome?
Blood and fluid accumulate within a compartment
How are cranial nerves numbered?
CN I to CN XII
How much blood does the muscular system receive at rest?
24 L per minute
What is a muscle compartment?
Group of functionally related muscles
Enclosed by fascia
Separated by intermuscular septa
How do capillaries reach every muscle fiber?
They branch extensively through the endomysium
What is the treatment for compartment syndrome?
Rest, immobilization, and fasciotomy
What is a retinaculum?
A connective tissue band for tendons
What are the symptoms of compartment syndrome?
History of trauma, dark urine, muscle breakdown
What is the difference between direct and indirect muscle attachment?
Direct has little separation from bone
Where do spinal nerves arise from?
From the spinal cord
What is muscle innervation?
Identity of the nerve that stimulates a muscle
Enables diagnosis of nerve injuries
What are the four categories of muscle action?
Prime mover (agonists)
Synergist
Antagonist
Fixator
What is a plexus?
A web-like network of spinal nerves
What do some muscles attach to instead of bone?
Fascia or tendon of another muscle
How much blood does the muscular system receive during heavy exercise?
More than three-quarters (11.6 L/min)
What are intrinsic muscles?
Contained entirely within a region
How many cranial nerves are there?
Twelve (CN I to CN XII)
What is the blood supply to the muscular system at rest?
About 1.24 L per minute
Give an example of intrinsic muscles.
The muscles of the hand
What are extrinsic muscles?
Act on a designated region with attachment elsewhere
What do capillaries do in muscle tissue?
Branch extensively through the endomysium
Give an example of extrinsic muscles.
Muscles of the forearm moving fingers
What does innervation of a muscle refer to?
Identity of the nerve that stimulates it
What are antagonist pairs?
Muscles acting on opposite sides of a joint
What is the role of a prime mover (agonist)?
Produces most of the force during action
What is the function of synergists?
Aids the prime mover in its action
What substance is released into the blood during muscle breakdown?
Myoglobin
What does an antagonist do?
Opposes the prime mover's action
What is the primary treatment for muscle breakdown?
Rest and immobilization
What is protraction in muscle movement?
An anterior movement in the transverse plane
How much blood does the muscular system receive at rest?
24 L per minute
What is medial (internal) rotation?
Bone spins to face medially
What connects muscle to bone?
Tendons
What are some specialized functions and characteristics of muscle?
Specialized function: contraction
Other functions: movement, stability, heat production
Universal characteristics: excitability, contractility, extensibility, elasticity
What is myology?
Study of muscles
Includes muscle structure, function, and disorders
What is elevation in muscle movement?
Movement of a body part vertically
What are antagonist pairs?
Muscles acting on opposite sides of a joint
What is lateral (external) rotation?
Bone spins to face laterally
Give an example of extrinsic muscles.
Muscles of the forearm moving fingers
What is a fasciotomy?
Incision to relieve pressure
What is the role of a fixator muscle?
Prevents movement of bone during contraction
What is extension in muscle movement?
Increases a joint angle
Where do cranial nerves arise from?
Base of the brain
What is a retinaculum?
A connective tissue band for tendons
What is adduction?
Movement toward the midline
What is inversion?
Foot movement that tips soles medially
What is the role of an antagonist?
Opposes the prime mover's action
What is the function of a fixator?
Prevents movement of a bone
What is extension in terms of muscle movement?
Increases a joint angle
What is circumduction?
One end of an appendage remains stationary
What is an aponeurosis?
A broad, flat sheet tendon
What is abduction?
Movement away from the midline
What is depression in muscle movement?
Movement that lowers a body part
What are extrinsic muscles?
Act on a region but attach elsewhere
What do synergists do?
Aid the prime mover in muscle action
What is protraction?
An anterior movement in the transverse plane
What is retraction in muscle movement?
A posterior movement in the transverse plane
What is compartment syndrome and its causes?
Compartment syndrome: increased pressure in muscle compartments
Causes: trauma, swelling, bleeding
Treatment: fasciotomy, rest, immobilization
What is medial (internal) rotation?
Bone spins to face medially
What is abduction?
Movement away from the midline
What is dorsiflexion?
Movement that elevates the toes
How are cranial nerves numbered?
From CN I to CN XII
Give an example of intrinsic muscles.
The muscles of the hand
What are the four categories of muscle action?
Prime mover (agonists)
Synergist
Antagonist
Fixator
What is depression in muscle movement?
Movement that lowers a body part
What do spinal nerves do after emerging from the spinal cord?
Branch into posterior and anterior rami
What is plantar flexion?
Movement that points the toes downward
What is dorsiflexion?
Movement that elevates the toes
What is the difference between direct and indirect attachment to bone?
Direct has little separation; indirect uses tendons
How do muscles act as movers?
Prime mover: main force producer
Synergist: aids prime mover
Antagonist: opposes prime mover
Fixator: stabilizes muscle attachment
What terms describe muscle movements with their associated joints?
Flexion and extension
Abduction and adduction
Medial and lateral rotation
Elevation and depression
Protraction and retraction
What is inversion?
Foot movement that tips soles medially
How are muscles named?
Location
Size
Shape
Direction of fibers
Number of origins
Action
Why is knowing innervation important?
It helps diagnose nerve and spinal injuries
What is flexion in muscle movement?
Decreases a joint angle
Where do spinal nerves arise from?
Spinal cord
What is supination?
Turns the palm to face upward
What is flexion in terms of muscle movement?
Decreases a joint angle
What is elevation in muscle movement?
Movement of a body part vertically
What do some muscles attach to instead of bone?
Fascia or tendon of another muscle
What is adduction?
Movement toward the midline
What is eversion?
Foot movement that tips soles laterally
What is circumduction?
One end of an appendage remains stationary
What is eversion?
Foot movement that tips soles laterally
Name three examples of fixator muscles.
Rhomboids, levator scapulae, trapezius
What is retraction?
A posterior movement in the transverse plane
What are the traditional terms for muscle attachments?
Origin and insertion
What is the role of a prime mover (agonist)?
Produces most of the force in an action
What are some specialized functions of muscle?
Movement
Posture maintenance
Heat production
Joint stabilization
What are the differences between intrinsic and extrinsic muscles?
Intrinsic: contained within a region
Extrinsic: acts on a region but attaches elsewhere
What is pronation?
Causes the palm to face downward
What are intrinsic muscles?
Contained entirely within a region
What is supination?
Turns the palm to face upward
What is pronation?
Causes the palm to face downward
Name three examples of fixator muscles.
Rhomboids, levator scapulae, trapezius
What happens to blood supply during heavy exercise?
Muscular system's share exceeds 11.6 L/min
What is plantar flexion?
Movement that points the toes downward
What are the universal characteristics of muscles?
Excitability
Contractility
Extensibility
Elasticity
How do muscles act as movers?
Prime movers produce force
Synergists assist
Antagonists oppose
Fixators stabilize
What is a plexus in relation to spinal nerves?
A web-like network of spinal nerves
What are the differences between intrinsic and extrinsic muscles?
Intrinsic: contained within a region
Extrinsic: acts on a region but attaches elsewhere
How do capillaries reach every muscle fiber?
They branch extensively through the endomysium
What is myology?
Study of muscles
What are some terms used to describe muscle movements with their associated joints?
Flexion
Extension
Abduction
Adduction
Rotation
Elevation
Depression
What is lateral (external) rotation?
Bone spins to face laterally
Describe the gross structural organization of muscle.
Muscle fibers
Fascicles
Connective tissue layers (endomysium, perimysium, epimysium)
What is compartment syndrome and its causes?
Increased pressure within a muscle compartment
Causes: trauma, swelling, bleeding
How many nuclei do muscle fibers have?
Multiple nuclei
What are myoblasts?
Stem cells that fuse to form muscle fibers
What is myoglobin?
Red pigment providing oxygen for muscles
What type of control do skeletal muscles have?
Voluntary control
Why do skeletal muscles appear striated?
Due to arrangements of contractile proteins
How long can skeletal muscle fibers be?
Up to 30 cm
How are connective tissue wrappings related to tendons?
They are continuous with tendon collagen fibers
What is the sarcolemma?
Plasma membrane of a muscle fiber
What are the connective tissue wrappings of skeletal muscle?
Endomysium: around muscle fiber
Perimysium: around muscle fascicle
Epimysium: surrounding entire muscle
Tendons: attach muscle to bone
What is the function of collagen in connective tissue?
It provides extensibility and elasticity
How does collagen behave under tension?
Stretches slightly and recoils when released
What role does connective tissue play in muscle function?
Resists excessive stretching and protects muscle
What are myofibrils?
Long protein cords in muscle fibers
What is the sarcoplasm?
Cytoplasm of a muscle fiber
What is glycogen's role in muscle fibers?
Stored energy for exercise
What role do satellite cells play?
Regeneration of damaged muscle tissue
What is the sarcoplasmic reticulum (SR)?
Smooth ER around each myofibril
What are terminal cisterns?
Dilated end-sacs of the SR
What is the function of T tubules?
Penetrate muscle fiber and transmit signals
What are thick filaments made of?
Myosin molecules
What is a triad in muscle fibers?
A T tubule and two terminal cisterns
What are thin filaments composed of?
Fibrous (F) actin and tropomyosin
How are myosin molecules structured?
Shaped like a golf club with tails
What is the role of tropomyosin?
Blocks active sites on G actin subunits
What are contractile proteins?
Myosin and actin that perform contraction
What does troponin do?
Binds calcium and moves tropomyosin
What is titin's function?
Stabilizes thick filaments and provides recoil
What are regulatory proteins?
Tropomyosin and troponin that control contraction
How is contraction activated in muscle fibers?
By calcium binding to troponin
What causes striations in muscle cells?
Organization of myosin and actin
What is dystrophin's role?
Links actin to membrane proteins
What disease is associated with dystrophin defects?
Muscular dystrophy
What are A-bands in muscle striations?
Dark bands where thick filaments overlap
What is a sarcomere?
Segment from Z disc to Z disc
What are I-bands in muscle striations?
Light bands with only thin filaments
How do muscle cells shorten during contraction?
Sarcomeres shorten as filaments slide past
What happens to filament lengths during contraction?
Filaments do not change length
What is denervation atrophy?
Shrinkage of paralyzed muscle without nerve
What is the structural hierarchy of skeletal muscle?
Muscle, fascicle, muscle fiber, myofibril, sarcomere, myofilaments
What happens if nerve connections to muscle are severed?
Muscle becomes paralyzed
What is the role of nerves in skeletal muscle contraction?
Nerves stimulate muscle contraction
What are somatic motor fibers?
Axons leading to skeletal muscle
How many muscle fibers does one motor neuron supply?
One muscle fiber
What is a motor unit?
One nerve fiber and its muscle fibers
How do muscle fibers in a motor unit behave?
Contract in unison
What is the average number of muscle fibers in a motor unit?
About 200 muscle fibers
What characterizes small motor units?
Fine degree of control
What characterizes large motor units?
More strength than control
Which muscle has a large motor unit?
Gastrocnemius of the calf
What are the key components of the muscular system covered in this material?
Properties of skeletal muscle
Structural components of a muscle fiber
Characteristics of skeletal muscle
Elastic functions of connective tissue
Structural hierarchy of skeletal muscle
Striations and protein filaments
Major proteins of muscle fibers
Motor units and muscle contraction
What is the relationship between nerve and muscle?
Nerves stimulate muscle contraction
Severed nerves lead to paralysis
Denervation atrophy occurs without nerve
What are the defining characteristics of skeletal muscle?
Voluntary control
Striated appearance
Long cylindrical fibers
Multiple nuclei
Connective tissue wrappings
What is the structural hierarchy of skeletal muscle?
Muscle
Fascicle
Muscle fiber
Myofibril
Sarcomere
Myofilaments
What are the major proteins of a muscle fiber?
Myosin: thick filament, contraction
Actin: thin filament, contraction
Tropomyosin: blocks active sites
Troponin: binds calcium
Titin: stabilizes thick filaments
Dystrophin: links actin to membrane
What is the appearance of skeletal muscle?
Striated
What is the resting membrane potential in skeletal muscle cells?
About -90 mV
What is the neuromuscular junction (NMJ)?
Point where a nerve fiber meets a muscle fiber
What is the role of the axon terminal in the NMJ?
It contains synaptic vesicles with acetylcholine
What is the synaptic cleft?
Gap between axon terminal and sarcolemma
What happens when a nerve impulse reaches the NMJ?
Synaptic vesicles release acetylcholine into the cleft
What condition is caused by a lack of acetylcholine receptors?
Myasthenia gravis
What is the function of acetylcholinesterase (AChE)?
Breaks down acetylcholine for muscle relaxation
How do cholinesterase inhibitors affect muscle function?
They prevent degradation of acetylcholine, causing paralysis
What causes tetanus (lockjaw)?
Toxin from Clostridium tetani blocks glycine release
What is spastic paralysis?
Continual contraction of muscles
What is flaccid paralysis?
State where muscles are limp and cannot contract
How does curare affect muscle function?
Competes with ACh for receptor sites without stimulation
What is botulism?
Food poisoning caused by a neuromuscular toxin
What is an action potential?
Quick up-and-down voltage shift in a cell
What maintains the resting membrane potential?
Sodium-potassium pump
What happens in an unstimulated muscle cell?
More anions inside than outside the membrane
What occurs during depolarization?
Sodium ions flow into the cell, making it positive
How does an action potential propagate along a muscle fiber?
It triggers another action potential down the membrane
What is the role of calcium in muscle contraction?
Calcium binds to troponin, exposing active sites
What initiates the excitation phase of muscle contraction?
Nerve signal arrives at the axon terminal
What are the four major phases of muscle contraction and relaxation?
Excitation: Nerve action potentials lead to muscle action potentials.
Excitation-Contraction Coupling: Links action potentials to myofilament activation.
Contraction: Muscle fiber develops tension and may shorten.
Relaxation: Muscle fiber relaxes and returns to resting length.
What happens during the excitation phase after calcium enters the axon terminal?
Calcium stimulates synaptic vesicles to release ACh
How does ACh affect the sarcolemma?
ACh binds to receptors, opening ligand-gated channels
What is the end-plate potential?
Rapid voltage change at the motor end plate
What happens when the action potential reaches the T-tubules?
It continues down into the cell interior
What occurs during excitation-contraction coupling?
Action potentials link to activation of myofilaments
What happens when a new ATP binds to myosin?
It breaks the cross-bridge with actin
What is the power stroke in muscle contraction?
Myosin head pulls thin filament during contraction
Why do muscles contract after death?
Deteriorating SR releases calcium, activating contraction
What is rigor mortis?
Hardening of muscles after death
What happens to calcium concentration during relaxation?
Calcium concentration in cytosol falls
What role does tropomyosin play during relaxation?
Blocks active sites on actin filaments
What happens to muscle fibers when stimulation ends?
They relax and return to resting length
What are the steps of muscle contraction?
Excitation: Nerve action potentials lead to muscle action potentials.
Excitation-Contraction Coupling: Links action potentials to myofilament activation.
Contraction: Myosin heads pull actin filaments.
Relaxation: Muscle fibers return to resting length.
What are the differences between smooth muscle and skeletal muscle?
Smooth muscle lacks striations; skeletal muscle is striated
Smooth muscle has one nucleus; skeletal muscle has multiple
Smooth muscle contracts slowly; skeletal muscle contracts quickly
What does the force of a muscle contraction depend on?
The muscle's length prior to stimulation
What happens if a muscle is overly shortened before stimulation?
A weak contraction results
What produces the greatest force when a muscle contracts?
Optimum resting length
What occurs if a muscle is too stretched before stimulation?
A weak contraction results
What does the nervous system maintain to ensure resting muscles are near optimum length?
Muscle tone
What is the threshold in muscle physiology?
Minimum voltage for muscle contraction
What is the latent period in muscle contraction?
Brief delay between stimulus and contraction
What is a twitch in muscle physiology?
A quick cycle of contraction and relaxation
What happens during the relaxation phase of a muscle twitch?
Tension declines to baseline
What occurs during the contraction phase of a muscle twitch?
Muscle generates external tension
How long does the entire twitch duration vary?
Between 7 and 100 ms
What happens with subthreshold stimuli?
No contraction occurs
What principle governs the recruitment of motor units?
The size principle
What influences the strength of muscle twitches?
The muscle's starting length
How do warmer muscles affect contraction strength?
Enzymes work more quickly
What does increasing the frequency of stimulus delivery do?
Increases tension output
At what point does the rate of oxygen consumption plateau?
At maximum oxygen uptake (max)
What is recruitment in muscle physiology?
Bringing more motor units into play
What happens with low frequency stimuli?
Produce identical twitches
What affects ATP supply for muscle contraction?
Oxygen and organic energy sources
What occurs with higher frequency stimuli?
Produces temporal summation
What is essential for all muscle contractions?
ATP
What is complete tetanus?
Steady contraction from high stimulus frequency
What contributes to fatigue in low-intensity exercise?
Fuel depletion and electrolyte loss
What does aerobic respiration produce?
Far more ATP than anaerobic fermentation
What two factors influence the speed of conduction in nerve fibers?
Myelin and diameter of the fiber
What is muscle fatigue?
Progressive weakness from prolonged use
How does excess ADP affect muscle function during fatigue?
It inhibits calcium release and decreases force production
What is maximum oxygen uptake?
Major determinant of exercise endurance
What are the shared characteristics of cardiac and smooth muscle?
Both are myocytes with one nucleus
What is the maximum oxygen uptake (max) a determinant of?
Ability to maintain high-intensity exercise
What is a primary cause of fatigue in low-intensity exercise?
Fuel depletion as glycogen and glucose levels decline
What is the function of the SA node in cardiac muscle?
It sets off a wave of electrical excitation
How does the autonomic nervous system affect heart rate?
It can increase or decrease heart rate
What type of respiration does cardiac muscle primarily use?
Aerobic respiration
What is the shape of smooth muscle myocytes?
Fusiform shape
What stimulates contraction in smooth muscle?
Variety of stimuli including autonomic activity
What is the relationship between muscle fiber types and contraction speed?
Fast-twitch fibers contract quickly
What is plasticity in smooth muscle?
Ability to adjust tension to stretch
What characterizes slow-twitch fibers?
Well adapted for endurance and resist fatigue
What is a characteristic of fast-twitch fibers?
Adapted for quick responses and powerful movements
What color are slow-twitch fibers typically?
Deep red
What are the unique properties of smooth muscle related to its functions?
Capable of mitosis and hyperplasia
Slower contraction but can sustain for long periods
Regenerates well after injury
Controls organ contents and modifies pressure
What are the types of smooth muscle and their characteristics?
Multiunit smooth muscle: contracts independently, found in large arteries and air passages
Single-unit smooth muscle: contracts as a unit, found in most hollow organs
What is the role of calcium in smooth muscle contraction?
Calcium enters from extracellular fluid
Triggers contraction via calmodulin
Different channels gated by various stimuli
What is anaerobic fermentation?
ATP production without oxygen
How long can the phosphagen system provide energy?
For about 6 seconds of sprinting
What is a key property of cardiac muscle?
Contracts with regular rhythm
What is the anaerobic threshold?
Point at which lactate becomes detectable
What role does electrolyte loss play in muscle fatigue?
It decreases muscle excitability
How do damaged cardiac muscle cells repair?
By fibrosis, not regeneration
What is the phosphagen system?
Combination of ATP and creatine phosphate
Why are cardiac muscle cells called cardiomyocytes?
They are specialized muscle cells of the heart
Why is it important for muscle cells of a given chamber to contract in unison?
To effectively expel blood from the heart
What happens as the phosphagen system is exhausted?
Muscles shift to anaerobic fermentation
What is the structural characteristic of cardiomyocytes?
They are shorter and thicker than skeletal muscle
What is the role of intercalated discs in cardiac muscle?
They allow direct stimulation between cardiomyocytes
At what age does maximum oxygen uptake peak?
Around age 20
What distinguishes smooth muscle from skeletal muscle?
It lacks striations
How do cardiac and smooth muscle cells receive innervation?
From the autonomic nervous system
How does smooth muscle regenerate after injury?
It regenerates well through mitosis
How does maximum oxygen uptake vary between genders?
Usually greater in males than females
How long can EPOC last after exercise?
Can last an hour
What is the latch-bridge mechanism in smooth muscle?
It maintains contraction without consuming ATP
How does smooth muscle respond to stretch?
It can contract and then relax
What does EPOC stand for?
Excess Postexercise Oxygen Consumption
What happens after about 40 seconds of exercise?
Aerobic respiration meets ATP demand
When does maximum oxygen uptake typically peak?
Around age 20
How does the structure of smooth muscle facilitate contraction?
Thick filaments have myosin heads along their length
What is the primary energy source for slow-twitch fibers?
Oxidative (aerobic) ATP production
What factors can stimulate smooth muscle contraction?
Autonomic nervous system activity
Hormones and chemical signals
Mechanical stretch
Temperature changes
What substance released by exercising muscles inhibits brain cells?
Ammonia
What is one purpose of EPOC?
To replenish ATP and regenerate CP stores
What causes fatigue in high-intensity exercise?
Potassium accumulation in T tubules
How does multiunit smooth muscle differ from single-unit smooth muscle?
Multiunit contracts independently; single-unit contracts as one
What is the function of smooth muscle in hollow organs?
It propels contents and modifies pressure
What are the differences between cardiac muscle and skeletal muscle?
Cardiac muscle is involuntary; skeletal is voluntary
Cardiac muscle has intercalated discs; skeletal does not
Cardiac muscle contracts rhythmically; skeletal can contract quickly
What is peristalsis?
Waves of contraction in hollow organs
How can maximum oxygen uptake differ in trained individuals?
Can be twice as great in trained endurance athletes
What is oxygen debt in relation to EPOC?
Difference between elevated and usual resting oxygen consumption
What is the appearance of fast-twitch fibers?
Pale (white)
Why can smooth muscle contract forcefully when stretched?
It has no Z discs limiting contraction
What is the psychological factor related to fatigue?
Will to persevere, not well understood
What are the two types of smooth muscle?
Multiunit and single-unit smooth muscle
What is central fatigue in the context of exercise?
Less motor signals issued from the brain
What are the characteristics of cardiomyocytes?
Striated but shorter and thicker
Joined by intercalated discs
Autorhythmic and can contract without nervous stimulation
Highly resistant to fatigue
What is the significance of the stress-relaxation response in smooth muscle?
Allows hollow organs to fill gradually
Prevents emptying while filling
Helps maintain organ function under varying conditions
How does smooth muscle maintain contraction without fatigue?
Latch-bridge mechanism allows prolonged contraction
Myosin heads do not detach immediately
Reduces ATP consumption during sustained contraction
How does maximum oxygen uptake differ between genders?
Usually greater in males than females
Why is cardiac muscle highly resistant to fatigue?
It has large mitochondria and myoglobin
How does training affect maximum oxygen uptake?
Can be twice as great in trained athletes
How does VO2 max typically differ between males and females?
VO2 max is usually greater in males than females
What is the main cause of fatigue in high-intensity exercise?
Potassium accumulation in the T tubules reduces excitability
How does excess ADP and slow cross-bridge movements affect muscle force production?
They inhibit calcium release and decrease force production in myofibrils
What is the major determinant of one's ability to maintain high-intensity exercise for more than 4 to 5 minutes?
Maximum oxygen uptake (VO2 max)
Why is VO2 max proportional to body size?
Larger bodies have more muscle mass and thus higher oxygen demands
What is the purpose of EPOC?
To aerobically replenish ATP, replace oxygen reserves, dispose of lactate, and provide oxygen to cells with elevated metabolic rates
How can VO2 max differ between a trained endurance athlete and an untrained person?
VO2 max can be twice as great in a trained endurance athlete as in an untrained person
What is EPOC?
Excess postexercise oxygen consumption
How much higher can EPOC be compared to basal consumption?
EPOC can be six times basal consumption
What are the physiological classes of muscle fibers?
Slow-twitch, slow oxidative (SO), red or type I fibers
Fast-twitch, fast glycolytic (FG), white, or type II fibers
Fast-twitch, intermediate, or type IIA fibers
What are the characteristics of slow-twitch, type I muscle fibers?
They are well adapted for endurance, resist fatigue through aerobic ATP production, have abundant mitochondria and myoglobin, and are grouped in small motor units
What happens if a stimulus is subthreshold?
If a stimulus is subthreshold, it will not elicit a muscle twitch response
What are the characteristics of fast-twitch, type II muscle fibers?
They are well adapted for quick responses, utilize glycolysis and anaerobic fermentation for energy, lack myoglobin, and are grouped in large motor units
How do the fiber types within a muscle differ across individuals?
Some individuals are genetically predisposed to have more fast-twitch fibers and be better suited for sprinting, while others have more slow-twitch fibers and are better suited for endurance
How does resistance training impact muscle growth?
Resistance training leads to muscle fiber enlargement through the synthesis of more myofilaments and myofibrils
How does endurance training impact muscle fibers and the cardiovascular system?
Endurance training increases the number of mitochondria, glycogen stores, and blood capillaries in slow-twitch fibers, and also enhances the function of the cardiovascular, respiratory, and nervous systems
What is a myogram and what are its key phases?
A myogram is a recording of a muscle twitch, with key phases including the latent period, contraction phase, and relaxation phase
What are the two main pathways for ATP production in muscles?
Aerobic (oxidative) and anaerobic (glycolytic) pathways
What is the relationship between a muscle's length prior to stimulation and the strength of its contraction?
A muscle resting at its optimal length is prepared to contract more forcefully than a muscle that is excessively contracted or stretched
Which ATP production pathway is the most efficient?
The aerobic (oxidative) pathway is the most efficient for ATP production
How can the frequency of stimuli influence muscle tension?
The greater the frequency of stimulation, the more strongly a muscle will contract due to temporal summation
How does muscular strength depend on different factors?
Primarily muscle size: Thicker muscle forms more cross-bridges
Fascicle arrangement: Pennate are stronger than parallel, and parallel stronger than circular
Size of active motor units: Larger motor units produce stronger contractions
Multiple motor unit summation: Simultaneous activation of more units increases tension
Temporal summation: Higher frequency of stimulation leads to stronger contractions
Length-tension relationship: Muscle at optimal resting length contracts more forcefully
Fatigue: Fatigued muscles contract more weakly than rested muscles
What provides a muscle with immediate, short-term, and long-term energy?
Immediate energy from creatine phosphate, short-term energy from glycolysis, and long-term energy from aerobic metabolism
What are the major subdivisions of the nervous system?
Central and peripheral nervous systems
How do neurons transport materials between the cell body and axon tips?
Through axonal transport mechanisms
How many types of cells aid neurons, and what are they called?
Six types of neuroglia
What is the overall function of the nervous system?
To coordinate and control body functions
What are the three basic functional categories of neurons?
Sensory, interneurons, motor neurons
What is a nerve?
A bundle of nerve fibers wrapped in tissue
What is a ganglion?
A knot-like swelling of neuron cell bodies
What are the parts of a neuron?
Neurosoma, dendrites, axon
What does the central nervous system (CNS) consist of?
Brain and spinal cord
What are the two subdivisions of the sensory division?
Somatic and visceral sensory divisions
What are the steps the nervous system uses to carry out its tasks?
Sense organs receive information and transmit messages to CNS.
CNS processes information and determines response.
CNS issues commands to muscles and glands.
What do interneurons do?
Connect motor and sensory pathways in CNS
What are the three functional properties found in all neurons?
Excitability, conductivity, secretion
What does the motor (efferent) division of the PNS do?
Carries signals from CNS to effectors
What do motor (efferent) neurons do?
Send signals to muscles and gland cells
What is the neurosoma?
The control center of a neuron
What does the parasympathetic division do?
Calms the body and slows functions
What are the universal properties of neurons?
Excitability, conductivity, secretion
What does excitability in neurons refer to?
Response to environmental changes called stimuli
What is the peripheral nervous system (PNS)?
All nervous system parts except CNS
What does the sympathetic division do?
Arouses body for action
What does conductivity in neurons refer to?
Producing electrical signals quickly conducted
What does secretion in neurons refer to?
Releasing neurotransmitters at the end of nerve fibers
What are the subdivisions of the motor division?
Somatic and visceral motor divisions
What is the function of the somatic motor division?
Carries signals to skeletal muscles
What does the sensory (afferent) division of the PNS do?
Carries signals from receptors to CNS
What is the function of the visceral motor division?
Carries signals to glands and smooth muscle
What are sensory (afferent) neurons responsible for?
Detecting stimuli and transmitting information
What does the cytoplasm of a neuron contain?
Mitochondria, lysosomes, Golgi complex
What is the function of the cytoskeleton in a neuron?
Provides structure and compartmentalizes rough ER
What are inclusions in the cytoplasm of a neuron?
Glycogen, lipid droplets, melanin, lipofuscin
What is the myelin sheath?
Insulating layer around the axon
What is axonal transport?
Two-way passage of materials along an axon
What are axon collaterals?
Branches that extend from the axon
What is the axon terminal?
Swelling that forms a junction with the next cell
What is the axon hillock?
The mound from which the axon originates
What is the function of the axon?
Conducts signals to distant points
What is retrograde transport?
Movement up the axon toward the neurosoma
What are kinesin and dynein?
Motor proteins for axonal transport
What guides materials along the axon?
Microtubules
What does fast retrograde transport move?
Recycled materials and pathogens
How do neuroglia outnumber neurons?
By at least 10 to 1
What do microglia do?
Wander looking for debris and damage
What is the role of neuroglia?
Protect neurons and help them function
What is Broca's area responsible for?
Language production
What is the role of the thalamus?
Directs incoming sensory messages to the cerebrum
What do ependymal cells do?
Line brain cavities and secrete CSF
When is myelination completed?
In late adolescence
Why is dietary fat important for the CNS?
It is important for CNS development
What is the trigger zone in a neuron?
Axon hillock and initial segment combined
Which ion has the greatest influence on resting membrane potential?
Potassium
How does potassium influence resting membrane potential?
Leaks out until equilibrium is reached
How does sodium influence resting membrane potential?
It slightly influences RMP but is less permeable
What happens when a chemical stimulant binds to a receptor?
Opens sodium gates and allows sodium to enter
What happens during depolarization of an action potential?
Sodium enters and depolarizes the cell
How is meningitis diagnosed?
By examining CSF obtained via lumbar puncture
What are the three layers of the meninges?
Dura mater, arachnoid mater, pia mater
What initiates the depolarization of the membrane at the axon hillock?
Arrival of current at axon hillock
What can cause swelling of the brain in meningitis?
Bacterial or viral invasion of the CNS
What is the weight of the human brain in men?
1600 g or 3.5 lbs
What is the result of the rapid positive feedback cycle during an action potential?
More channels open as voltage rises
What does the medulla oblongata regulate?
Heart rate, respiratory rate, blood vessel diameter
What is the function of the hypothalamus?
Maintains homeostasis and regulates various functions
What is the function of the pons?
Connects sensory and motor pathways in the brainstem
What are nodes of Ranvier?
Gaps between segments of myelin sheath
What is the blood-brain barrier?
Protective barrier between blood and brain
Regulates substance entry
Maintains brain homeostasis
What is the function of the cranial dura mater?
Protects the brain and forms dural sheath
What is the advantage of electrical synapses?
Quick transmission with no delay
What causes the resting membrane potential?
Unequal electrolyte distribution between fluids
What is an action potential?
Rapid change in membrane polarity
What is anterograde transport?
Movement down the axon away from neurosoma
What are the properties of local potentials?
Graded, decremental, reversible, excitatory or inhibitory
What does fast anterograde transport move?
Organelles, enzymes, synaptic vesicles
What characterizes the relative refractory period?
Only a strong stimulus can trigger a new action potential
What is the conduction speed of small unmyelinated fibers?
0.5 to 2.0 m/s
What is depolarization?
Change in membrane potential toward zero mV
What is electrophysiology?
Study of electrical potentials and currents
What is the role of the sodium-potassium pump?
Moves 3 sodium out for every 2 potassium in
How can neurons be stimulated?
By chemicals, light, heat, or mechanical disturbance
What do astrocytes do?
Support neurons and regulate blood flow
What is the initial segment of a nerve fiber?
Short section between axon hillock and first glial cell
What is the function of the cerebrum?
Largest subdivision of the brain, responsible for higher functions
What is the role of the falx cerebri?
Separates the two cerebral hemispheres
Which cells produce myelin in the CNS?
Oligodendrocytes
What is the conduction speed of large myelinated fibers?
Up to 120 m/s
What is the resting membrane potential of neurons?
About -70 mV
What is the concentration of potassium in the ICF compared to the ECF?
About 40 times more concentrated in ICF
What does the brainstem include?
Diencephalon, midbrain, pons, medulla oblongata
How do Schwann cells myelinate nerve fibers in the PNS?
By spiraling around a single nerve fiber
How much ATP does the sodium-potassium pump require?
1 ATP per exchange
What is an action potential?
A rapid up-and-down shift in membrane voltage
What happens if the threshold is not reached during an action potential?
The neuron does not fire
What do Schwann cells do?
Envelope nerve fibers in PNS
What is the neurilemma?
Thick, outermost coil of myelin sheath
How do oligodendrocytes myelinate nerve fibers in the CNS?
By anchoring to multiple nerve fibers
What does the temporal lobe control?
Sense of hearing and language comprehension
What is the role of the presynaptic neuron in a synapse?
Releases neurotransmitter to stimulate the next cell
What are the functions of the two types of neuroglia found in the PNS?
Schwann cells: Form myelin sheaths and assist in regeneration.
Satellite cells: Provide insulation and regulate chemical environment.
What percentage of the nervous system's energy requirement does the sodium-potassium pump use?
70%
What does it mean for an action potential to be nondecremental?
It does not get weaker with distance
What is presynaptic facilitation and inhibition?
Facilitation: enhances neurotransmitter release
Inhibition: reduces neurotransmitter release
What is slow axonal transport?
Rate of 0.5 to 10 mm/day
Which cells produce myelin in the PNS?
Schwann cells
Why do slow signals go to the gastrointestinal tract?
Speed is less of an issue there
What is a local potential?
Short-range change in voltage toward trigger zone
What is meningitis?
Inflammation of the meninges
What does it mean for an action potential to be nondecremental?
It does not weaken with distance
What is the composition of myelin?
20% protein and 80% lipid
What are local potentials?
Changes in membrane potential at stimulated areas
What are the lobes of the cerebrum?
Frontal, parietal, temporal, occipital, insula
What occurs as the membrane potential rises above 0 mV?
Channels inactivate and close
What are the functions of cerebrospinal fluid (CSF)?
Cushions the brain
Provides buoyancy
Removes waste products
Maintains stable chemical environment
What is fast axonal transport?
Rate of 20 to 400 mm/day
Where does an action potential occur?
Where there is a high density of voltage-regulated gates
What is the role of the basal lamina in the PNS?
It is external to the neurilemma
Why is an action potential considered irreversible?
Once started, it goes to completion
What do satellite cells do?
Surround neurosomas in PNS ganglia
What is the primary function of myelin in the nervous system?
Insulation around a nerve fiber
When does myelination begin during fetal development?
At week 14
What is the function of the occipital lobe?
Responsible for vision
What is the threshold voltage required to open voltage-regulated gates?
About -55 mV
What is the function of the parietal lobe?
Responsible for general senses like touch
What does slow axonal transport move?
Enzymes, cytoskeletal components, new axoplasm
What is hyperpolarization?
Membrane becomes more negative than resting potential
What occurs at the peak of an action potential?
Sodium channels close and potassium channels open
What is the primary function of the meninges?
Protecting the brain and providing structural support
What are the colliculi in the midbrain responsible for?
Visual and auditory reflexes
What is the role of the tentorium cerebelli?
Separates cerebrum from cerebellum
Why can't cytoplasmic anions escape the cell?
Due to size or charge
What happens when voltage-gated channels open during an action potential?
Sodium enters and depolarizes the cell
What is the all-or-none law in action potentials?
If threshold is reached, neuron fires maximally
What does it mean for an action potential to be irreversible?
Once started, it goes to completion
What is neural integration?
Process of combining multiple signals
Determines whether a neuron will fire an action potential
What are the types of synapses in the nervous system?
Electrical synapses
Chemical synapses
What happens during the repolarization phase of an action potential?
Slow channels open and potassium exits
What is the weight of the human brain in women?
1450 g or 3.2 lbs
What is the refractory period in relation to action potentials?
Period of resistance to stimulation
What are the steps in the action potential shift in membrane voltage?
Arrival of current at axon hillock depolarizes membrane
Depolarization reaches threshold (-55 mV)
Voltage-gated sodium channels open, sodium enters
Membrane potential rises, sodium channels close
Slow potassium channels open, potassium exits
Membrane briefly hyperpolarizes, then returns to resting potential
What are the major parts of the brain?
Cerebrum, cerebellum, brainstem
What are postsynaptic potentials?
Changes in membrane potential in response to neurotransmitters
Can be excitatory or inhibitory
What is the role of the frontal lobe?
Motor control, motivation, judgment, aggression
What does the insula lobe play a role in?
Taste, pain, consciousness, and cardiovascular homeostasis
What is the peak voltage of an action potential?
About +35 mV
What is hyperpolarization in the context of an action potential?
Membrane becomes more negative than resting membrane potential
What are common symptoms of meningitis?
High fever, stiff neck, drowsiness, headache
What are the characteristics of action potentials compared to local potentials?
Follows an all-or-none law
Nondecremental: do not weaken with distance
Irreversible: once started, cannot be stopped
How is resting membrane potential restored after an action potential?
Sodium leaks in and extracellular potassium is removed
What is the role of the falx cerebelli?
Separates right and left halves of cerebellum
What age group is most affected by meningitis?
Infants and children between 3 months and 2 years
What is the characteristic of an action potential compared to local potentials?
Follows an all-or-none law
What are the two phases of the refractory period?
Absolute and relative refractory periods
What is the term for the neuron that responds to neurotransmitters?
Postsynaptic neuron
What structures are included in the limbic system?
Hippocampus and amygdala
What occurs during the absolute refractory period?
No stimulus can trigger an action potential
What can happen if meningitis is untreated?
Progression to coma and death
What is the role of the lumbar puncture in diagnosing meningitis?
Obtains CSF for examination
How many axon terminals can a spinal motor neuron have?
About 10,000 axon terminals
What is the subarachnoid space?
Space between arachnoid and pia mater
What is the significance of the brain's weight?
Indicates complexity and function of the brain
What does the midbrain appear as in a sagittal section?
A hook at the superior end
What is the role of the arachnoid mater?
Transparent membrane over the brain surface
What types of synapses can a presynaptic neuron form?
Axodendritic, axosomatic, or axoaxonic synapses
What is a disadvantage of electrical synapses?
Cannot integrate information and make decisions
What is the trade-off of chemical transmission in neural integration?
Synaptic delay slows information travel
What is the significance of the pia mater?
Follows contours of the brain, very thin
What do chemical synapses use to communicate?
Neurotransmitters
What separates the layers of the cranial dura mater?
Dural sinuses collect blood circulating through the brain
What do synaptic vesicles contain?
Neurotransmitter
What is the primary role of the cerebellum?
Coordination and balance
What is neural integration?
The ability to process and recall information
What is the function of the subdural space?
Separates arachnoid mater from dura mater
What is an excitatory postsynaptic potential (EPSP)?
A voltage change toward threshold
What causes an inhibitory postsynaptic potential (IPSP)?
Hyperpolarization of the cell
What is the significance of the transparent nature of the arachnoid mater?
Allows for the passage of cerebrospinal fluid
What neurotransmitters produce EPSPs in brain cells?
Glutamate and aspartate
What is the function of the emetic center in the medulla oblongata?
Regulates vomiting
What is the role of the pyramids in the medulla oblongata?
Crossing of motor messages to opposite sides
What neurotransmitters produce IPSPs?
Glycine and GABA
What are the key functions of the brainstem?
Controls basic life functions
Connects cerebrum and spinal cord
Regulates heart rate and breathing
What is the role of the ascending tracts in the pons?
Carries sensory messages to the thalamus
What is the pathway of cerebrospinal fluid (CSF) in the brain?
Produced in the ventricles
Flows through the subarachnoid space
Absorbed into the bloodstream
What is the significance of the colliculi in the midbrain?
Direct sensory messages to the thalamus
What is the function of the superior colliculi?
Important for visual reflexes
What is the function of the inferior colliculi?
Important for auditory reflexes
What is summation in the context of neural integration?
Adding up postsynaptic potentials
What is temporal summation?
EPSPs generated quickly at a single synapse
What are the key functions of the cerebellum?
Coordination of voluntary movements
Balance and posture
Motor learning
What is spatial summation?
EPSPs from several synapses add up
What are the two anterior raised areas on the medulla oblongata called?
Pyramids
What is presynaptic facilitation?
One presynaptic neuron enhances another
What neurotransmitter is released during presynaptic facilitation?
Serotonin
What happens to motor messages at the pyramids?
They cross sides
What is presynaptic inhibition?
One presynaptic neuron suppresses another
How does acetylcholine (Ach) affect different muscles?
Excites skeletal muscle but inhibits cardiac muscle
Where do messages from the right frontal lobe go?
To muscles on the left side
What neurotransmitter is released during presynaptic inhibition?
GABA
What centers does the medulla oblongata regulate?
Heart rate, respiratory rate, blood vessel diameter
What criteria must be met for nerve regeneration to occur?
Alignment of nerve fibers and minimal damage
What is the function of myelin?
Insulates nerve fibers to speed conduction
Where is the pons located?
Between the medulla oblongata and midbrain
What is the function of the emetic center in the medulla oblongata?
Regulates vomiting
What generates resting membrane potential?
Distribution of ions across the membrane
What do ascending tracts in the pons carry?
Sensory messages to the thalamus
What are the bulges on the posterior surface of the midbrain called?
Corpora quadrigemina
What do descending motor tracts in the pons do?
Carry messages to the cerebellum
Describe the events of an action potential.
Depolarization, repolarization, hyperpolarization
What is the function of synapses?
Transmit signals between neurons
What is the difference between a local potential and an action potential?
Local potentials are graded; action potentials are all-or-none
What is the function of the superior colliculi?
Important for visual reflexes
What is the function of the inferior colliculi?
Important for auditory reflexes
What are the two major types of synapses?
Electrical and chemical synapses
Where is the cerebellum located?
Posterior and inferior to the occipital lobes
What does the cerebellum receive sensory messages about?
Position of limbs, muscles, and joints
What are the disadvantages of chemical synapses?
Involve synaptic delay in transmission
How many ventricles are in the brain?
Four internal chambers
What two factors influence the speed of conduction in nerve fibers?
Myelin and diameter of the fiber
What is the arbor vitae in the cerebellum?
Tracts of white matter
What are the advantages of chemical synapses?
Allow for decision making and integration
How does the cerebellum use sensory information?
To fine-tune skeletal muscle messages
What does the term neural integration mean?
The ability to process and recall information
What connects the two lateral ventricles to the third ventricle?
Interventricular foramen
What percentage of blood does the brain receive?
15%
What does the term summation mean?
The process of adding up postsynaptic potentials
Where is the third ventricle located?
Beneath the corpus callosum
Where is the fourth ventricle located?
Between the pons and cerebellum
What runs through the midbrain connecting the third and fourth ventricles?
Cerebral aqueduct
What structures can a presynaptic neuron synapse with?
Dendrite, neurosoma, or axon of postsynaptic neuron
How much CSF does the brain produce daily?
500 mL/day
What is cerebrospinal fluid (CSF)?
Clear, colorless liquid in CNS
What is the choroid plexus?
Spongy mass of blood capillaries
How do temporal and spatial summation differ?
Temporal is time-based; spatial is location-based
What does the ependyma do?
Lines ventricles and covers choroid plexus
What is presynaptic facilitation?
One presynaptic neuron enhances another
What is presynaptic inhibition?
One presynaptic neuron suppresses another
How do ependymal cells modify CSF?
They alter its ion composition
What is the normal volume of CSF present at one time?
100 to 160 mL
What begins the production of CSF?
Filtration of blood plasma through capillaries
What are the three major functions of CSF?
Buoyancy, protection, chemical stability
What criteria must be met for nerve regeneration to occur?
Alignment of nerve fibers and minimal damage
What neurotransmitter is released during presynaptic facilitation?
Serotonin
What generates resting membrane potential?
Distribution of ions across the membrane
How does CSF provide buoyancy?
Reduces pressure on nervous tissue
What neurotransmitter is released during presynaptic inhibition?
GABA
What is the function of myelin?
Insulates nerve fibers to speed conduction
Where is most CSF formed?
Subarachnoid space external to brain
What percentage of body weight does the brain represent?
2%
How does CSF protect the brain?
Absorbs shocks from jolting
How does CSF contribute to chemical stability?
Rinses away metabolic wastes
What is the blood supply to the brain in mL/min?
750 mL/min
What happens after a 10-second interruption of blood flow?
Loss of consciousness may occur
What can a 1 to 2 minute interruption of blood flow cause?
Significant impairment of neural function
What happens after 4 minutes without blood?
Irreversible brain damage occurs
What does the brain barrier system regulate?
Substances entering brain tissue fluid
What are the two points of entry that must be guarded by the blood barrier system?
Blood capillaries and choroid plexus
What does the blood-brain barrier protect?
Blood capillaries throughout brain tissue
What forms the blood-brain barrier?
Tight junctions between endothelial cells
How do astrocytes contribute to the blood-brain barrier?
Induce endothelial cells to form tight junctions
What must anything leaving the blood pass through?
Endothelial cells
What can the brain barrier system obstruct?
Delivery of medications like antibiotics
What can damage the blood-brain barrier?
Trauma and inflammation
Why are CVOs important?
Allow monitoring of blood variables
What are circumventricular organs (CVOs)?
Places where the barrier is absent
Describe the flow of cerebrospinal fluid.
Produced in choroid plexus
Flows through ventricles
Circulates around the brain and spinal cord
Absorbed into bloodstream
What can CVOs allow access to the brain?
Pathogens like HIV
What are the functions of the meninges?
Protect the brain and spinal cord
Contain cerebrospinal fluid
Provide structural support
What are the three major functions of cerebrospinal fluid?
Buoyancy: reduces pressure on the brain
Protection: absorbs shocks
Chemical stability: regulates environment
What is the functional significance of the blood-brain barrier?
Protects brain from harmful substances
Regulates entry of nutrients
Maintains stable environment for neurons
What are the structures of the brainstem and their functions?
Medulla oblongata: regulates autonomic functions
Pons: relays signals between cerebellum and cerebrum
Midbrain: processes visual and auditory information
What are the lobes of the cerebrum and their functions?
Frontal lobe: decision making, problem solving
Parietal lobe: sensory perception
Temporal lobe: auditory processing
Occipital lobe: visual processing
Where in the brain is the blood-brain barrier absent?
Circumventricular organs (CVOs)
Important for monitoring blood variables