Physiology 2.4: Higher functions pt. 1

describe brain organization

• 100 billion neurons

• brain weighs 3 pounds

whare the major parts of the cerebrum

• frontal lobe

• temporal lobe

• brain stem

• cerebellum

• occipital lobe

• parietal lobe

describe the frontal lobe

• planning

• reasoning

• problem-solving

• recognizing

• regulating emotion

• social skill

describe the temporal lobe

• understanding language

• processing auditory information

• organizing information

• memory and learning

describe the brain stem

• regulates breathing, body temperature, heart

describe the parietal lobe

• recognizing sensation, body position, recognizing objects, spatial judgements, understanding time

describe the occipital lobe

• integrating and processing visual information

describe the cerebellum

• controls balance and muscle coordination

describe the organization of the cerebral cortex

• surface layer of gray matter

• neocortex

  • newest region

  • 90% of cerebral cortex

  • made by 6 cellular layers

• archicortex

• paleocortex

what is the neocortex

• newest and largest outer layer of the brain

  • forms top layer of cerebral hemispheres and surrounds deeper brain structures

what is the neocortex formed by

• archicortex

• paleocortex

what are the two types of cells in the cerebral cortex

• stellate cells

  • dendrites projecting in all directions

  • process local information, receive direct sensory information from thalamus

• pyramidal cells

  • axon that passes out of area into white matter

  • excitatory neuron sending long-distance axons to other brain regions

describe the protective layers of the central nervous system

• hair, skin, skull

• meninges

• cerebrosinal fluid

• BBB

describe the meningeal layers

• meningeal layer of the brain cushion and protect delicate neural tissue

  • dura mater

    • form the venous sinus

  • arachnoid mater

  • pia matter

describe cerebrospinal fluid

• shock absorbing

• provides stable environment for generating nerve impulses

• medium for exchanging nutrients and waste between blood and tissue

what generates cerospinal fluid

• ependymal cells

describe the blood brain barrier

• tight junctions formed by astrocytes on capillaries and sinuses

  • limits permeability

what percentage of the blood pumped by heart goes to brain

15%

what percentage of body’s glucose is used by brain

half

in the brain, what moves glucose from plasma and into the brain

membrane transporters

what does the blood brain barrier protect the brain from

• hormones and circulating chemicals

  • protects CNS from

    • chemical fluctuations

    • entry of harmful substances

    • entry of molecules that could act as neurotransmitters

what can cross the blood brain barrier

• O2

• CO2

• alcohol

• steroid

• H2O

how can consciousness be defined/assessed

• by behavior

  • from maximum attentiveness to comatose

• pattern of brain activity that can be record electrically

  • EEG

whats an EEG

• records electrical activity using electrodes attached to head

• originates in pyramidal cells of cortex

• meausred in microvolt (µV)

what does EEG measure

• state of consciousness from the electrical activity of brain

• measures summed postsynaptic potentials (PSPs)

  • measures the electrical activity of pyramidal neurons firing in cerebral cortex

    • synced from thalamus firing rhythmic, oscillatory signals

      • simultaneous PSPs reinforce each other rather than cancelling out

describe the waveform characteristics of EEG

• amplitude

  • from 0.5 to 100 microvolts (uV)

• frequency

  • from 1 to 40 hertz (Hz)

    • vary with state of consciousness (calm, alert, sleeping)

what is an alpha rhythm (consciousness state and frequency)

• awake state

• relaxed with eyes closed

  • decreased attention

• 8-13 Hz

what is a beta rhythm

• awake state and active

• prominent when paying attention or thinking hard

• more than 16 — 31 Hz

what is SMR rhythm

• physical stillness but calm and alert

• 12—15 Hz

what is Mu wave

• completely relaxed and still

• 7.5 —12 Hz

what is gamma wave

• very alert and attentive

• 32-100 Hz

what is theta rhythm

• sleeping state

• 4-7 Hz

what is delta rhythm

• sleeping state

• 0.5-4 Hz

summarize the EEG patterns from low to high frequency

• delta wave (0.1 — 3 Hz)

  • stage 3 and 4 of slow wave sleep

• theta wave (4 — 7 Hz)

  • stage 1 of slow wave sleep

• alpha wave (8 — 15 Hz)

  • drowsy, eyes closed

• mu wave (7.5 — 12.5 Hz)

  • completely relaxed

• SMR wave (12.5 — 15.5 Hz)

  • alert but still

• beta wave (16 — 31 Hz)

  • active

• gamma wave (32 — 100 Hz)

  • full capacity

as you fall asleep, you go from alpha to ___ amplitudes and ____ frequency

• higher amplitude

• lower frequency

stage 3 and 4 sleep, characterized by __ rhythm, is considered…

• delta wave

• slow wave sleep

describe non-REM state

• 4 stages with increasing amounts of theta to delta

• then reverse from stage 4 back to stage 1

describe REM sleep

• rapid eye movement

  • higher frequency

  • lower amplitude

REM sleep is similar to what rhythm?

beta rhythm

as the night goes on… REM sleep gets ___

• longer

  • non-REM sleep stages drop out

how many cycles of REM sleep do healthy adults get

4 to 6

what happens during REM sleep

• increased sympathetic activity

  • increased HR, BP, and respiration

• decrease in muscle control

  • except eyes

    • if we played out our dreams its dangerous

• a lot of dreaming

during REM sleep, it is harder to ___ but more likely to___

• harder to arouse

• more likely to awake spontaneously

whats the purpose of hypotonia

• protect the dream from acting out his dreams and harming himself/others

what are the brain areas that control consciousness

• reticular activating system

• hypothalamus

describe the reticular activating system and its role in controlling consciousness

• network of neurons spanning the midbrain, pons, and medulla

  • primary control for wakefulness and consciousness

describe the hypothalamus and its role in controlling consciousness

• preoptic area

  • promotes NREM and slow-wave sleep (SWS)

    • releases GABA that suppresses arousal

• posterior hypothalamus

  • promotes wakefulness

    • produces orexin (on-switch for consciousness)

• suprachiasmatic nucleus

  • regulator of circadian rhythm

    • light data to synchronize internal biological clock

describe the preoptic area in the hypothalamus

• promotes NREM and slow-wave sleep (SWS)

  • releases GABA that suppresses arousal

describe the posterior hypothalamus in the hypothalamus

• promotes wakefulness

  • produces orexin (on-switch for consciousness)

describe the suprachiasmatic nuclus in the hypothalamus

• regulator of circadian rhythm

  • uses light data to synchronize internal biological clock

what is the purpose of sleep

• repair time

• consolidation of learned information

• conservation of energy (were not hunting this hour)

what are some sleep-wake cycle disorders

• insomnia, bedwetting, sleepwalking, sleep apnea, and narcolepsy

describe epilepsy

• abnormal synchronization of cortical neurons

• complete loss of control of brain

• can spike up to 1000 uV

describe coma

• severe or total decrease of mental function

  • little EEG activity

describe brain death

• absolute no brain activity

describe fMRI

• assesses brain activity in specific areas

describe CT

• X-ray of brain structure, not very detailed and doesn’t show activity

describe PET scan

• injection of radioactive glucose

  • assess glucose activity in brain regions

  • metabolic changes

what are the pros and cons of an EEG

pros

• easy to be installed

• not invasive

• accessible

cons

• low spatial resolution

• cannot identify specific locations

• cannot measure activity below cortex

what is the hypothesized cause of EEG activity

• synchronized postsynaptic potentials from millions of pyramidal neurons in cerebral cortex

what are the 4 basic frequency patterns of an EEG

• Beta

• Alpha

• Theta

• Delta

what are the differences between NREM and REM sleep

• NREM

  • makes up most of total sleep

  • consists of 3 distinct stages N1, N2, and N3

    • from light drowsiness to slow-wave sleep

  • physical restoration, tissue repair, immune system support

  • HR and BP decrease

• REM

  • dream sleep

  • resembles beta waves

  • eye movement and muscle paralysis

  • cogntive and emotional processing, memory consolidation

  • HR and BP increase

the number of cycles in a sleeping period

• 4 to 6

  • each cycle lasts 70 to 120 minutes

    • switches from non-REM to REM sleep

      • early cycles features more deep non-REM sleep while later cycles feature longer periods ot REM

What is slow wave sleep?

• N3 sleep

  • the deepest stage of NREM sleep

    • high-amplitude delta brain waves

  • HR, BP, temperature drop and muscles relax

• functions: physical restoration, immune support, memory consolidation

when do sleep spindles and k complexes occur

• stage 2 of non-REM sleep

what areas of the brain influence sleep

• hypothalamus

• brainstem

• basal forebrain

• thalamus and cerebral cortex

describe lateral hypothalamus role in wakefulness

• releases orexin

  • on-switch

what are the main wake-promoting transmitters

• norepinephrine

• orexin

• serotonin

• acetylcholine

• dopamine

what are the man sleep-promoting transmitters

• GABA

• Glycine