Physiology chapter 4

Primary visual cortex

medial surface of occipital lobe-receives input from thalamus (lateral genticulate nuclei) concerning shape,color,mvmt

Primary auditory cortex

-superior part of temporal lobe
-interprets characteristics of sound, hearing

Primary gustatory area

-at base of post central gyrus in parietal lobe
-receives impulses for taste

Primary motor cortex

-precentral gyrus of frontal lobe
-controls voluntary contractions of specific muscles/muscle groups
-size of area and # of neurons representing each body part is proportional to precision/complexity of mvmt of that part (motor hommunculus)

Premotor cortex

-practice is recorded here
-orients body&arms toward specific targets
-deals w/ learned motor activities of complex/sequential nature
-muscle memory
-creates signal "I need this to occur"

Language areas

-comprehension and translating thought into speech involves sensory,association and motor speech areas in frontal lobe
-Broca's area-speech formation, speaking ability,attaches words to concepts
-Wernicke's area-language comprehension

Association areas

tracts that connect motor ans sensory areas and large parts of cortex

Prefrontal association cortex

planning voluntary activity
decision making
creativity, personality traits
higher thought

Parietal-temporal-occipital association cortex

-pools and integrates somatic,auditory,visual sensations for complex perceptual processing
also involved w/language

Limbic association cortex

"repitilian brain"
motivatoin and emotion
involved with memory
preservation of organism/species
sex,food,pleasure
hippocampus-short term memory

Integration of cortical regions

Sensory input->somatosensory cortex->higher sensory areas
->association areas->higher motor area->primary motor cortex->motor output

Basal ganglia (nuclei)

-group of nuclei in each cerebral hemisphere
-regulates (inhibits) muscle tone required for smooth body mvmts
-selects&maintains purposeful motor activity
-monitors/coordinates slow sustained contractions-posture/support

Diencephalon
Thalamus

-pair of oval shaped structures
-grey matter organized into nuclei
-principal relay station for all sensory input to cerebral cortex
-routes sensory impulses to appropriate areas of somatosensory cortex
-directs attention to stimuli of interest

Diencephalon
Thalamus
areas that provide sensory input

Spinal cord
brain stem
cerebellum
other parts of cerebrum

Diencephalon
Thalamus
important nuclei

medial genticulate nuclei-hearing
lateral genticulate nuclei-sight
ventral posterior-taste,somatic sensation(pain,pressure)
anterior nucleus-emotions,memory

Diencephalon
Hypothalamus

-inferior,anterior to thalamus
-major regulator of homeostasis
-controls/integrates ANS
-regulates contraction of sm.muscle,cardiac muscle,secretions of many gland
-primary regulator of visceral activities:heart rate,GI mvmt,bladder contraction
-feelings of rage/aggression
-body temp,food intake,thirst
-maintains wake/sleep patterns
-controls ant.pituitary hormone secretion
-produces/transports hormones to post.pituitary gland

Limbic system
structure

ring of structures encircling brain stem:
-portion of cortical lobe
-amygdala
-basal nuclei
-hypothalamic nuclei
-thalamic nuclei
-olfactory bulbs

Limbic system
functions

emotional aspect of behavior
memory in conjunction with hippocampus and cerebrum

Cerebellum
location

posterior to medulla and pons

cerebellum
functions

-subconscious mvmt of skeletal muscle/equilibrium
-control skeletal muscle contractions for skilled mvmt.coordination
-receives input-desired action from motor cortex
-receives feedback-actual action from proprioceptors,vestibular apparatus,eyes
-compares inputs/sends adjustments/corrective signals to motor tracts

Tracts
vestibulocerebellum

balance and control of eye mvmt
location in space

Tracts
spinocerebellum

-enhances muscle tone/coordinates skilled voluntary mvmt-synchronization/timing
-role in subconscious control of voluntary mvmt

tracts
spinocerebellum
pathway

motor cortex->command to muscles and informs spinocerebellum->mvmt->activates muscle/joint receptors->relays actual performance to spinocerebellum->comparison and adj. made

Brain stem
3 organs

Midbrain,pons,medulla

Brain stem
function

-link between spinal cord and hgher brain levels
-relays motor&sensory impulses between other higher parts of brain&spinal cord
-origin of many cranial nerves-supply head and neck

Brain stem
Midbrain
function

eye mvmt control
head mvmt in response to sight and sound

Percent of sensory info going to brain that is vision

60

Brain stem
Pons
function

-sensory and motor nuclei for 4 cranial nerves (3-6)
-nuclei that help control respiration
-nuclei and tracts linking cerebellum w/brain stem,cerebrum,spinal cord
-ascending,descending,transversetracts

Brain stem
Pons
where do respiratory nuclei go

into medulla

Brain stem
Medulla
functions

-relay station/reflex centres
-dexussation of pyramids-motor tract crossover
-olivary nuclei
-respiratory center-regulates basic breathing rhythm
-cardiovascular center-heartbeat,rate,force
-vascular diameter-vasoconstriction&dilation

Reticular formation
def/location

network of interconnected neurons begins in medulla and runs throughout brain stem into thalamus

Reticular formation
functions

-functions in consciousness and arousal (bell on alarm clock)
-receives and integrates all incoming sensory synaptic input

Reticular activating system
def/location

ascending fiber sends signals upward to arouse and activate cerebral cortex

Reticular activating system
function

Controls overall degree of cortical alertness/level of consciousness

Reticular activating system
levels of consciousness

maximum alertness->wakefulness->sleep->coma

Reticular activating system
What does level of consciousness depend on

Cyclical interplay between RAS and slow wave and paradoxical sleep centers in hypothalamus

EEG
function

records electrical activity within cerebral cortex from EPSP and IPSP

EEG
used for

-diagnose cerebral dysfunctions
-brain death
-sleep patterns

EEG
describe wave forms

alpha waves-8-13 Hz
beta waves-13 Hz
delta waves-<4Hz
theta waves 4-8 Hz

Sleep
function

time to restore biochemical and physiological process degraded: we are tired

Sleep
role of adenosine on sleep

-alternating activity in brainstem and RAS may regulate sleep cycle
-adenosine-backbone of ATP/nucleotide
-increased levels generated during wakefulness
-acts as neuromodulator to inactivate arousal center

Sleep
how does caffeine keep us awake

Caffeine blocks adenosine receptors in brain
Prevention of inhibitory action on arousal center

Why is sleep necessary to memory

consolidation of procedural memories

Memory trace

neural change responsible for retention and storage of knowledge

memory
consolidation

process of transferring and fixing short-term memory traces into long-term memory stores

working memory

temporarilyu holds and interrelates various pieces of information relevant to a current mental task (Like RAM-has logical limit to size)

short term memory
characteristics

seconds up to 72 hours
limited capacity
rapid retrieval

short term memory
mechanism

temporary modification of synaptic function
changes in ion channels in axon terminals
presynaptic facilitation (cAMP)

memory
habituation

decreased responsiveness to stimulus
Ca2+ channel closure-reduced NT release

memory
sensitization

increased responsiveness
release of serotonin from interneuron,blocks K+ channels,prolongs AP so Ca2+ channels are open longer, increasing NT output