A&P 2 Exam 1

brain waves

reflect the pattern of electrical activity (neuronal firing) in cerebral post-synaptic neurons upon which higher mental functions are based.

Electroencephalogram (EEG)

recording of brain waves as they spread through the cerebral cortical areas

What are EEGs used to diagnose?

brain and sleep disorders and to determine occurrence of brain death.

Frequency

number of peaks in 1 second (Hz)

Amplitude

size of wave; reflects synchronization of many neurons, not amount of electrical activity of individual neurons.

Beta waves

mentally alert (highest frequency)

Alpha waves

relaxed or meditative (2nd highest frequency) (low amplitude)

Theta waves

deeply relaxed (zoned out) (3rd highest frequency) (higher amplitude)

Delta waves

deep sleep (or brain damage) (slowest frequency) (highest amplitude)

Changes on an EEG monitor occur with:

• sensory stimuli

• emotional state

• chemical state of the body

• brain disease

Abnormalities in EEG could indicate:

• Delta waves in awake adults = brain damage

• epilepsy

• tumors

• encephalopathies

What are the characteristics of Non-REM (NREM) sleep?

• non- dreaming

• decreased brain energy metabolism

• muscles relaxed

• decreased blood flow to brain

• decreased ventilation rate

• regular (stable) rate of ventilation

• regular heart rate

What are the characteristics of REM sleep?

• dreaming (limbic system)

• increased brain energy metabolism

• eye muscles, face muscles, limb muscles twitch (rapid eye movement)

• increased blood flow to brain

• increased ventilation rate

• irregular (unstable) rate of ventilation

• irregular heart rate

NREM Stage 1

eyes closed, relaxed, easily awakened, lasts 1-7 min

NREM Stage 2

light sleep, harder to awaken

• K-complexes and sleep spindles

• important for memory consolidation (converting short term memory to long term memory)

sleep spindles

help keep you asleep by lowering arousal stimuli

NREM Stage 3

moderately deep sleep, HR and body temperature fall

NREM Stage 4

deep sleep, body temperature and heart rate low

• delta waves

• neural activity at basal levels

• metabolic rate drops

• important for body repair and tissue respiration, strengthening immune system

What is REM sleep important for?

processing day’s events and emotional problems.

What are some symptoms of REM sleep deprivation?

• Confusion

• Paranoia

• Irritability

• Mood swings

• Impaired cognition and problem solving

• Decrease in motor performance

• Loss of balance

Why is it hard to wake up during Stage 4 NREM sleep?

Thalamic neurons hyperpolarized during sleep

Orexins

chemicals released from the hypothalamus that wake us up

What are sleep patterns with age?

Infants get the most REM sleep, REM sleep declines until age 10 when it stabilizes at 25% of sleep.

Stage 4 sleep declines steadily throughout life.

What makes us sleepy?

Adenosine levels in the basal forebrain rise as sleep debt builds up.

How does coffee increase wakefulness?

Adenosine binds to A1R and A2R receptors, caffeine blocks these receptors to prevent adenosine effect.

What serves as the sleep/wake switch?

the hypothalamus

What is the SCN?

suprachiasmatic nucleus (our circadian clock)

What is circadian rhythm?

• 24 hour “internal central clock.”24-hour

• regulates:

  • sleep-wake cycle

  • hormone release

  • hunger

  • digestion

  • heartrate

  • blood pressure

  • neurological function

Melatonin

• Produced by the pineal gland in the SCN in response to darkness

• helps regulate circadian rhythm

• promotes drowsiness and deeper sleep at night

What happens with increased blue light?

• Decreased plasma melatonin levels

• Increased alertness

• Fewer delta waves, more alpha waves

What are the 4 important functions of muscle?

1. Produce movement

2. Maintain posture and body position

3. Stabilize joints

4. Generate heat as they contract

Muscle

bundle of fascicles connected to bone with a tendon

Fascicle

bundle of fibers

Fiber (aka muscle cell)

bundle of myofibrils

Myofibril

bundle of sarcomeres connected end-to-end

Sarcomere

functional unit of contraction (smallest contractile unit)

• distance from one Z-disk to the next

• stacked end-to-end throughout length of myofibril

myofilaments

actin and myosin

epimysium

outer connective tissue that surrounds an entire muscle

• dense collagen

perimysium

surrounds each muscle fasciculus

• moderately dense collagen

endomysium

surrounds each muscle fiber; coordinates smooth motion

• fine collagen

sarcolemma

muscle fiber plasma membrane

• barrier between the extracellular and intracellular compartments

• selectively permeable

• conductor of electrical activity

mitochondria

primary site of cellular energy production (ATP)

sarcoplasm

fluid part of the fiber, fills spaces within and between myofibrils

• contains proteins, minerals, glycogen, fats, cellular organelles, myoglobin

transverse tubules (t-tubules)

infoldings of the sarcolemma that surround each myofibril; conduct electrical impulses from the surface of the cell to the terminal cisternae

sarcoplasmic reticulum

storage deposit for Ca²⁺

• regulates intracellular Ca²⁺ levels

• voltage-gates channels in t-tubules initiates Ca²⁺ release

• Ca²⁺ pumps throughout the SR reabsorb Ca²⁺ to stop muscle contraction

Myosin

thick filament; binding sites for actin

• anchored at the M-line

Actin

thin filaments; binding sites for myosin, troponin, and tropomyosin

• attached to z-disk by titin

tropomyosin

twists around actin to cover up myosin binding site

troponin

regulates movement of tropomyosin

Titin

hold myosin in place (anchors it to the Z-disk)

• unfolds when muscle is stretched

• recoils when tension is released

• stiffens as it uncoils → helps the muscle resist excessive stretching which may pull sarcomeres apart

Desmin

extends from the Z disc and connects each actin filament to the next throughout the length of the muscle

What is the ratio of actin to myosin in a myofibril?

2:1

I band

contains actin only

H zone

thick filaments only

M line

thick filaments linked by accessory proteins

outer edge of A band

myosin and actin

during a muscle contraction, which bands shorten?

H-zone and I-band

motor unit

a single alpha-motor neuron and all of the muscle fibers it innervates

• each muscle fiber is innervated by only one alpha-motor neuron

neuromuscular junction

the point where the alpha-motor neuron terminates on the muscle fiber

• penetrates the sarcolemma

• allows for communication between the neuron and the muscle fiber

• ~ halfway along the length of the muscle fiber

excitation-contraction coupling

process of pairing of electrical events (motor neuron action potential) to mechanical events (muscle contraction)

Action potential propagation (initiation)

• never impulse initiated by the brain, synapses and travels through spinal cord

• spinal cord synapses with alpha-motor neuron, action potential spreads down the neuron

• synaptic vesicle delivers acetylcholine (ACh) to the axon terminal

• acetycholine is released into synaptic cleft

Action potential propagation (ACh receptor)

• ACh binds to ACh receptor

• opens chemically gates ion channel

  • Na+ influx, K+ efflux

• cell potential increases

• wave of depolarization across synaptic cleft

End plate potential

local change in membrane potential

Action potential propagation (Sarcolemma depolarization)

• many voltage gates Na+ channels throughout the sarcolemma (good conductor)

• voltage-gated Na+ channels open in response to change in membrane potential

• Na+ influx, membrane potential rises further

Action potential propagation (Sarcolemma repolarization)

• Voltage gated Na+ channel closes

• K+ efflux

• restores resting membrane potential (resting voltage)

• allows for propagation for the next action potential

• Na+, K+ pump eventually restores cellular ion balance

Excitation portion of EC coupling

• AP reaches t-tubule

• T-tubule activates voltage-sensitive Ca2+ channel on t-tubule, causes a change in shape

• shape change knocks open Ca2+ release channel on the terminal cistern of the SR; releases Ca2+ into myofibril

In a rested state, myosin binding site on actin is ____ by ____ and ______.

blocked; tropomyosin; troponin I

Explain what happens when calcium binds to troponin

• Ca2+ binds to binding sites on TnC,