Chapter 3.4-3.6 Flashcards
Define CNS and PNS
CNS: brain and spinal chord; a great majority of neuronal cell bodies are found in here
PNS: includes all axons dendrites and cell bodies
Nuclei versus ganglia
Nuclei: bundle of nerve cell bodies in the CNS
Ganglia: bundle of nerve cell bodies in the PNS
What are the three subdivisions of the brain?
Hindbrain ( rhomboencephalon)
Midbrain ( Mesencephalon)
Forebrain ( Prosencephalon)
CSF Cerebrospinal fluid
A clear liquid that the entire CNS floats in. Serves various functions such as shock absorption and exchange of nutrients and waste with the CNS.
Spinal chord : Location, General Function
Spinal chord is connected to the brain and protected by the CSF and the vertebral column. Pathway for info to and from brain. Most sensory data is relayed to brain for info, but the SC is also a site for info integration.
General: Simple reflexes
What is the hindbrain consisted of?
Medulla, pons and cerebellum
Medulla: Location, General Function
Location: Below the pons and is the area of the brain which connects to the spinal chord
General : Involuntary functions
Pons : Location, General Function
Location: Below midbrain and above the medulla , connection point between brain stem and the cerebellum
General: Relay centre and balance
Cerebellum : Location, General Function
Location: behind the pons and below the cerebral hemispheres
General: Movement coordination
Damage to cerebellum
Results in poor hand eye coordination and balance
Midbrain: Location, General Function
Location: Above the pons and below the hypothalamus
General: eye movement
Brainstem consists of :
Medulla, pons, midbrain
Forebrain includes:
Diencephalon and telencephalon
Diencephalon consists of:
Thalamus and hypothalamus
Thalamus : Location, General Function
Location: Near the middle of the brain below the cerebral hemispheres and above the midbrain.
General: Integrating center and relay station
Hypothalamus: General Function
General: Homeostasis and behavior
Telencephalon: what makes it special
-Consists of two separate cerebral hemispheres, which is unlike all of the other parts of the CNS up to and including the diencephalon ( which forms a single symmetrical stalk)
Left and R hemispheres and what they are responsible for
L hemi: primarily controls motor functions of the right side of the body; generally responsible for speech, dominant in most people
R hemi: controls motor functions of L side of the body; generally responsible for visual spatial reasoning and music
Corpus Callosum
A thick bundle of axons which connect the cerebral hemispheres
Cerebrum
Largest region of human brain and consists of the L paired cerebral hemispheres.
Hemispheres of cerebrum consist of:
- cerebral cortex ( outer layer of gray matter) plus an inner core of white matter connecting the cortex to the diencephalon
- gray matter: composed of trillions of somas
- white matter: composed of myelinated axons
Cerebral hemi general function
conscious thought processes and intellectual function
play a role in processing somatic sensory and motor info
The cerebral cortex is divided into 4 lobes:
Temporal, Frontal, Parietal, Occipital
Frontal lobe
initiate all voluntary movement and are involved in complex reasoning skills and problem solving
Parietal lobes
involved in general sensation ( such as touch, temp, pressure, vibration, etc) and in gustation ( taste)
Temporal lobes
-process auditory and olfactory sensation and are involved in short term memory, language comprehension, and emotion
Occipital lobes
Process visual sensation
Frontal eye field
Controls learned eye movements
Broca’s A general function
speech production
Wernicke’s A general function
language comprehension
Basal nuclei : General Function
- composed of gray matter and are located deep within the cerebral hemispheres; consists of several functioning divisions
General: Movement
Limbic system: Location, General Function
Location: between the cerebrum and diencephalon
- includes substructures such as the amygdala , cingulate gyrus and hippocampus
-works closely with parts of cerebrum, diencephalon, and midbrain
General: Emotion, memory and learning
Basal nuclei and cerebellum
process and coordinate mvmt initiated by the primary motor cortex; basal nuclei are inhibitory ( prevent excess movement) whereas cerebellum is excitatory
Cerebral cortex : General Function
General function: Perception, skeletal muscle mvmt, memory, attention, thought, language and consciousness
motor and sensory regions of the cortex are organized such that:
a particular small A of the cortex controls a particular body part, a larger A is dedicated to a body part which requires more and more sensation
All neurons entering and exiting the CNS are:
carried by 12 pairs of cranial nerves and 31 pairs of spinal nerves
Cranial vs. Spinal nerves
Cranial: convey sensory and motor info to and from the brainstem
Spinal: convey sensory and motor info to and from the spinal chord
Vagus nerve: Effects
- decreases heart rate and GI tract activity
- part of the parasympathetic division of the autonomic nervous system
- consists of a bundle of axons that end in ganglia on the surface of the heart, stomach and other visceral organs; the axons consisting of the vagus nerve are pregang and come from somas in the CNS
- on surface of heart and stomach, they synapse with posting
Somatic motor neurons
All innervate skeletal muscle cells, use ACh as neuro, cell bodies in brainstem or ventral ( front) portion of the spinal cord
Somatic sensory neurons
All have long dendrite extending from sensory receptor toward the soma, which is located just outside of the CNS in a dorsal root ganglion. All somatic sensory neurons, the first synapse is in CNS; depending on the type of sensory info conveyed, axon synapses in the cord or stretches al the way up to the brain stem before its first synapse
Dorsal root ganglion
- Bunch of somatic and autonomic sensory neuron cell does located just dorsal ( back of ) the spinal cord
- Pair of dorsal root ganglia for every segment of the spinal cord, and thus the dorsal root ganglia, form a chain along the dorsal ( back) aspect of the vertebral column
- Dorsal root ganglia are protected within vertebral column but r outside the meninges ( protective sheath of the brain and cord) and thus outside the CNS
- An axon extends from the somatic sensory neurons soma into the spinal cord
Autonomic PNS efferents
Eff.ts of sympa and para systems consists of 2 neurons: pre and post
Preganglionic neuron
Cell body in the brainstem or spinal cord
Sends axon to an autonomic ganglion , located outside the spinal column
In the ganglion, axon synapses with postganglionic neuron
Postganglionic neuron
Sends an axon to an effector ( smooth muscle or gland)
All autonomic pregang release
Acetylcholine as neuro
All parasympa postgang neurons release
Acetylcholine as neuro
Sympa postgang neurons release
norepinephrine NE as their neuro
Location of preganglionic soma for syma
Almost all have cell bodies in the thoracic (chest) or lumbar ( lower back ) regions of the spinal cord
Therefore, they are located at the thoracolumbar region
Location of pregang soma for parasympa
Cell bodies in the brain stem ( head or cranium) or sacral portion ( lowest portion of the spinal cord)
Sympa Pre and Post gang length
Pre- short
Post- long
para pre and post gang length
pre - long
post - short
Ganglia sympa
only a few ganglia
sympa ganglia are quite large
far from effector, close to cord
Ganglia para
small ganglion, close to effector, far from cord
Auto afferent ( sensory ) vs Somatic afferent
Similar except auto can synapse in PNS at auto ganglia with auto efferent neurons in what is known as a short reflex whereas the first synapse of somatic aff.t neurons is in the CNS
Adrenal cortex location and hormones released
Outer portion of adrenal gland- cortex secretes glucocorticoids ( cortisol) mineralocorticoids ( aldoseterone) and some sex hormones
Adrenal medulla location, relaton to autonomic , hormone relased
Inner portion of adrenal gland - medulla
Part of sympa system
embryologically derived from sympa postgang and directly innervated by sympa pregang.c neurons
Upon activation of sympa , adrenal gland is stimulated to release epinephrine , which is also known as adrenaline
Epinephrine: derivatives, effects
Slightly modified version of norepinephrine, neuro released by sympa postgang
Epi is hormone because released into blood by ductless gland
Behaves like neuro because it elicits effects very rapidly and effects are quite short lived
Causes sudden flushing and sweating one experiences when severely startled, stimulation of heat
Sensation , sensory receptors
Sensation: process by which we received info from the world around us
Sensory receptors; detect data both internally and externaly and send it to the CNS for processing
Sensation vs. Perception
Sensation: act of receiving info
Perception: act of organizing, assimilating, interpreting sensory input into useful and meaningful info
How does the brain know the diff between stimulation of visual receptors and olfactory receptors?
Both signals are received in the brain as action potentials from sensory neurons. Brain distinguishes sensory stimuli based on which sensory neurons are signaling.
Exteroreceptors
Interoceptors
Ex: sensory receptors that detect stimuli from the outside world
In: receptors that respond to internal stimuli
Mechanoreceptors
respond to mechanical disturbances
Mechanoreceptor ex: pacinian corpuscles
pressure sensors located deep in the skin
shaped like an onion and composed of concentric layer of specialized membranes
when corpuscular membranes are distorted by firm pressure on the skin, nerve endings become depolarized and signal travels up the dendrite ( these are graded potential changes- not action potentials)
Graded potential changes vs Action potentials
Action potentials, once initiated, are all or nothing events
Graded potentials code info based on amplitude, They are initiated by a stimulus that vary in magnitude depending on strength of the stimulus
Auditory hair cell vs. vestibular cells
Mechano
Auditory: specialized cell in cochlea of the inner ear
Vestibular: in special organs called semicircular canals,, also found in th inner ear
Role is to detect acceleration and position relative to gravity
Chemoreceptors
Ex
Respond to particular chemicals
Olfactory: detect airborne chemicals and allow us to smell things
Gustatory: taste buds
Auto: in walls of carotid and aortic arteries respond to changes in arterial pH , pCO2, pO2 levels
Nocireceptors and ex
Pain receptors, stimulated by tissue injury
consist of free nerve ending that detects chemical signs of damages
can be auto or somatic
Autonomic pain receptors
Do not provide the conscious mind with clear pain info, but they frequently give sensation of dull aching pain
create illusion of pain on skin, when their nerves cross paths with somatic afferents from the skin , phenomenon known as referred skin
Thermoreceptors and 3 categories of thermo
stimulated by changes in temp
autonomic and somatic ex
cold sensitive, warm sensitive and thermal nociceptors ( detect painfully hot stimuli)
Electromagnetic receptors and ex
stimulated by electromagnetic waves
in humans, rods and cones of the retina of the eye
in other animals, electro and magneto r separate
ex: some fish detect electric fields with electroreceptors and magnetoreceptors allow animals to sense the earths magnetic field, which can help them navigate during migration
Four properties that need to be communicated to the CNS:
Stimulus modality, location, intensity, duration
Stimulus modality
Type of stimulus, CNS determines his based on the type of receptor that is firing
Stimulus intensity
Coded by frequency of action potentials
Dynamic range
Range of intensities that can be detected by sensory receptors, can be expanded by range fractionation
Range fractionation and ex
Including multiple groups of receptors with limited ranges to detect a wider range overall
ex: in human cone cells which respond to different but overlapping ranges of wavelengths to detect the full visual spectrum of light
Stimulus location
communicated by receptive field of sensory receptor sending signal
Improving localization of stimulus
Overlapping receptive fields of neighboring receptors
works like a venn diagram
allows the brain to localize a stimulus activating neighboring receptors to the A where the receptive fields overlap
Discrimination between 2 stimuli
improved by lateral inhibition of neighboring receptors
Stimulus duration
can be coded explicitly or not
Tonic receptors
fire action potentials as long as stimulus continues
however, these are subject to adaptation , and the frequency of action potentials decreases as stimulus continues at the same level
explicitly communicates the duration of stimulus
Phasic receptors
only fire action potentials when stimulus begins
do not explicitly communicate the duration of the stimulus
important for communicating changes in stimuli and essentially adapt immediately if stimulus continues at the same level
Adaptation
decrease in firing frequency when intensity of stimulus remains constant
allows the brain to tune out unimpt info from the environment
receptors do not stop being able to respond, they can still be triggered if the stimulus intensity increases
Nervous system is programmed to respond to
changing stimuli
because constant stimuli are not a threat whereas changing stimuli need to be dealt with
nociceptors do not adapt under any circumstance, because pain something that the nervous system wants us to do something about
Propioception
awareness of self and body position
also known as kinesthetic sense
Muscle spindle
important ex of a propioceptor , mechanoceptor
sensory organ specialized to detect mucle stretch
receptor that senses muscle stretch in the muscle stretch reflex
Other proprioceptors: Golgi tendon organs and joint capsule receptors
Golgi: monitors tension in the tendons
joint: detect pressure, tension and movement in the joints
Purpose of proprioceptive system
Allow us to know positions of our body parts by monitoring the activity of the musculoskeletal system
Important during activity when precise feedback needed for coordinated motion
Which portion of CNS do you expect to require input from proprioceptors?
Cerebellum, which is responsible for motor coordination
Gustation
Olfaction
gust: taste
olf: smell
Gustation process
Taste bud consists of specialized epithelial cells shaped like an onion
In centre of taste bud is a taste pore, with taste hairs which detect food chemicals
Info about taste is transmitted by cranial nerves to an A of brain in temporal lobe not far from where brain receives olfactory info
Taste buds
Can only distinguish 5 different flavors sweet ( glucose) salty ( Na+) bitter ( basic) sour ( acidic) umami ( amino acids and nucleotides)
Olfaction process
Accomplished by olfactory receptors in the roof of the nasopharynx
Receptors detect airborne chemicals which dissolve in the mucus covering the nasal membrane
Olfactory nerves project directly to olfactory bulbs of the brain
Olfactory bulbs
Located in temporal lobe of the brain near the limbic system, important for memory and emotion
Might explain why certain smells can bring back vivid memories or feelings
Pheromones
chemical signals which cause a social response in members of the same species,
not well understood in humans, but have been studied extensively in insects
important means of communicating info;
ex. alarm pheromones alert rest of beehive of danger
Outer ear structures
Auricle or pinna
External auditory canal
Division of middle and outer ear
Tympanic membrane or eardrum
Middle ear structures
Consists of the ossicles Three small bones called: malleus ( hammer) incus ( anvil) stapes ( stirrup)
Division of middle and inner ear
oval window
Structures of inner ear
cochlea
semicircular canals
utricle
saccule
Semicircular canals with utricle and saccule
Important for a sense of balance
Membrane covered hole in cochlea near oval window and function
round window
releases excess pressure
Eustacian tube / auditory tube
Passageway from the back of throat to the middle ear
functions to equalize pressure on both sides of the eardrum and is the cause of ear popping 1 experiences in high altitudes or underwater
Mechanism of hearing
Sound waves enter external ear and pass into auditory canal- cause eardrum to vibrate
malleus receives vibrations and pass to incus and stapes
stapes contacts the oval window and vibration oval window creates pressure waves in perilymph and endolymph fluids in cochlea
pressure waves in endolymph cause vibration of basilar membrane
basilar membrane is covered with auditory receptor cells called hair cells
cells have cilia projecting from apicall surfaces which contact the tectorial membrane
when the basilar membrane moves , hairs dragged across tectorial mem and they bend
displacement opens ion channels in hair cells, which results in neuro release
dendrites from bipolar auditory afferent neurons are stimulated by neuro and thus the sound vibrations are converted to nerve impulses
Organ of corti
basilar membrane, hair cells and tectorial membrane
primary site at which auditory stimuli are detected
Reason why bones in middle ear arranged in such a way
They amplify the sound vibrations passing through the middle ear
Sound vibrations pass thru before being sensed
first conveyed through the air
then they are conveyed through bone
then liquid before they are sensed
outer ear and middle ear
convey sound waves to the cochlea
PItch
Frequency of sound is distinguished by which regions of the basilar mem vibrate, stimulating different auditory neurons
Basilar membrane thickness
Varies
Thick near oval window and gradually becomes thin and floppy near the apex
Low frequency
High frequency
Low: long wavelength, stimulated hair cells at the apex of the cochlear duct
High: short wavelength, stimulate hair cells at the base of the cochlea, close to oval window
Loudness of sound
distinguished by the amplitude of vibration
louder sounds cause more frequent action potentials in the auditory nerve
Stereophonic hearing
Allowed for by having 2 ears
Determining the location of the sound
by the difference detected by the 2 ears
ex. if a horn blasts to your right, right ear receives sound waves slightly sooner and slightly more intensely than the L ear
If a sensory neuron leading from ear to brain fires an action potential more rapidly, how will the brain perceive this change?
More rapid firing of cochlear neuron indicates an increase in the volume of the sound
If pitch is changed, a different set of neurons would fire action potentials
In some cases of deafness, sound can still be detected by conduction of vibration through the skull to the cochlea. If the auditory nerve is severed, can sound still be detected by conductance through bone?
Conductance through bone allows some hearing by causing the cochlea to vibrate, which stimulates action potentials that pass through the auditory nerve to the brain.
However, if the auditory nerve is severed, no hearing of any kind is possible
If the bones of the middle ear are unable to move, would this impair detection of sound by conductance through bone?
Bones of the middle ear serve to conduct vibration from outer ear to liquid within the cochlea but are not involved in detecting sound. Bone conductance can still stimulate the cochlea and result in hearing if the middle ear is non-functional.
Vestibular complex
Made up of 3 semicircular canals:
utricle, saccule and ampullae
Monitors static equilibrium and linear acceleration, which contributes to your sense of balance
Semicircular canals
Tubes filled with endolymph, like cochlea, contain hair cells that detect motion
Function is to detect rotational acceleration of the head
Innervated by afferent neurons which send balance info to pons, cerebellum, and other areas
Cornea
Clear portion at the front of the eye
Bends and refracts light as it passes through because the cornea is highly curved and acts like a lens , its refractive index is higher than that of air
Sclera
white layer that the cornea is continuous with at the borders
Choroid
Layer beneath the sclera
contains darkly pigmented cells which help absorb excess light within the eye
Retina
Layer beneath the choroid
Surface where light is focused
Detects light and converts stimuli to action potentials to send to the brain
located at the back of the eye
contains electromagnetic receptor cells ( photoreceptors) called rods and cones
Anteriror chamber
Just inside the cornea
Contains fluid called the aqueous humour
Iris
Membrane at the back of the ant chamber
coloured part of the eye
Muscles of the iris regulate the diameter of the pupil
¨Pupil
Opening in the iris
Posterior chamber
Behind the iris
Also contains aqueous humor
Lens
In the back part of the posterior chamber
Fine tune the angle of the incoming light so that beams are perfectly focused upon the retina
Ciliary muscle
varies the curvature and refractive power of the lens
Vitreous chamber
Where light passes thru on route to the retina from the lens
Passage of light in the eye
Cornea- anterior chamber- pupil - posterior chamber- lens-vitreous chamber- retina
When passing through retina, pass through ganglion cells- bipolar cells before reaching cone and rod cells
Rods and cones
responsible for detecting light
Transmission of visual info
rods and cones synapse with nerve cells called bipolar cells （ 1 dendrite and 1 axon)
bipolar cells synapse with ganglion cells, whose axons make u the optic nerve, which travels from each eye to occipital lobe of the brain for complex analysis of visual image
Optic disk
point on retina where many axons from ganglion cells converge to form the optic nerve
also known as blind spot because it has no photoreceptors
Macula
oval shaped pigmented area near the center of the retina
fovea centralis
at the center of the macula
contains only cones and is responsible for extreme visual acuity
also called the focal point
visual acuity
sharpness of vision
Rods and cones are made up of:
special pigment proteins that change tertiary structure upon absorption of light
Opsin
Pigment protein in rods and cones
Each one is bound to 1 molecule of retinal and contains 1 molecule of retinal , which is derived from vit A
Dark rods and cones and retinal, bipolar cells
Dark: rods and cones are resting and retinal has several trans double bonds and 1 cis double bond
retinal and opsin keep the Na channel open
cell remains depolarized
both rods and cones release Glu onto bipolar cells, preventing them from firing
Light rods and cones and retinal , bipolar cells
absorb light , retinal converted to all trans form
series of reactions which closes Na channel, causing cell hyperpolarization
rods and cones stop releasing Glu , bipolar cell depolarizes, causes depolarization of ganglion cells and an action potential along axon of ganglion cell
NIght vision
accomplished by rods, which are more sensitive to dim light and motion and more concentrated at periphery of the retina
Colour vision
require cones, which require abundant light and are also responsible for high acuity vision
more concentrated at the fovea as a result
three cones consist of colour vision, absorb blue, green and red light
What physical difference allows functional difference of cones?
Each type of cone makes a particular protein which is specialized to change conformation when light of appropriate frequency strikes it
Emmetropia
normal vision
Myopia
Nearsightedness
too much curvature causes light to be bent too much and to be focused in front of the retina
can be corrected by concave ( diverging) lens, which causes light to diverge slightly before they reach the cornea
too much refraction at the lens or an abnormally long eyeball results in a focal length that is too short
Hyperopia
farsightedness
focusing light behind retina caused by too little curvature
can be corrected by convex (converging) lens , cauing light rays to converge before cornea
too little refraction at the lens or an abnormally short eyeball results in a focal length that is too long
Presbyopia
inability to accommodate ( focus)
results from loss of flexibility of the lens, which occurs with aging
Neurons in visual cortex
fire in response to very specific info
Feature detecting neurons
specific neurons in the brain that fire in response to particular visual features, such as lines, edges, angles and movement
info is passed along to other neurons that begin to assimilate these distinct feature into ore complex objects and so on
Feature detection theory
explains why a certain area of the brain is activated when looking at a face versus when looking at letters on a page
Parallel processing
many aspects of a visual stimulus ( such as form, motion, color and depth) are processed simultaneously instead of in a step by step fashion different stimuli
used in order to vast amounts of information
Occipital lobe constructs
holistic image by integrating all of the separate elements of an object, in addition to accessing stored information
ex. brain is simultaneously processing the individual features of an image, while also accessing stored info
Amount of the cortex dedicated to processing:
visual info
touch info
auditory info
visual info: 30%
touch info: 8%
auditory: 3%
Depth perception
describes ability to see objects in 3D despite the fact that images are imposed on the retina in only 2D
allows us to judge distance
Depth perception experiments
Visual cliff
demonstrates that depth perception appears to be largely innate
babies placed on clear glass surface above a steep drop off
most babies not venture out over the visual cliff, indicating that their depth perception was developed enough to understand that the drop was dangerous
Binocular cues (BC)
depth cues that depend on info received from both eyes and are most important for perceiving depth when objects are close to us in our visual field
Retinal disparity
binocular cue
brain compares the images projected onto 2 retinas in order to perceive distance
greater difference or disparity between the 2 images on each retina, shorter the distance to the observer
farther images have less disparity ( images on each retina are quite similar)
Convergence
binocular cue
describes the extent to which eyes turn inward when looking at an object
greater the angle of convergence or inward strain, the closer the object
Monocular cues
depth cues that depend on info available from either eye alone
important for judging distances of objects that are far from us since the retinal disparity is only slight
cannot rely on binocular cues for objects that are farther distances
relative size
if objects are assumed to be the same size, the one with smaller image on retina appears more distant
MC
interposition
if one object blocks the view of another, we perceive it as closer
MC
relative clarity
perceive hazy objects as more distant than sharp clear objects
MC
texture gradient
change from coarse distinct texture to a fine indistinct texture indicates increasing distance
MC
relative height
perceive objects higher on the visual field as farther away
MC
relative motion
MC
objects which are near to us appear to move faster than objects that are farther away
linear perspective
parallel lines appear to converge as distance increases
greater convergence, greater distance
MC
light and shadow
dimmer of two identical objects seems farther away
MC
closer objects reflect more light than distant objects
receptor , receptor type, organ , stimulus for interoception
receptor: aortic arch baroreceptors
pH receptors
receptor type: baroreceptor
chemo receptor
organ: aortic arch
aortic arch or medulla oblongata
Stimulus : blood pressure
pHAbsolute threshold
minimum stimulus intensity required to activate a sensory receptor 50% of the time ( and thus detect the sensation)
can vary between individuals and different organisms
varies with age
ex. as we get older, we gradually lose our ability to detect higher pitched sounds
important for detecting the presence or absence of stimuli
What is the anatomical reason for the loss of our ability to detect higher pitched sounds as we age?
Loud sounds mechanically harm the hair cells , causing them to die
When this occurs, hair cell can no longer send sound signals to the brain
once hair cell dies in a human, it never regrows
hair cells detecting higher frequency sounds are the smallest and most easily damaged, therefore as people age and more hair cells are damaged and lost, hearing loss occurs
since the smallest hair cells are the ones most likely lost, loss of sensitivity to high pitched sounds is common in older people
Difference threshold
just noticeable difference or JND
minimum noticeable diff between any 2 stimuli 50% of the time
magnitude of initial stimulus influences the difference threshold
Webers law
states that two stimuli must differ by a constant proportion in order for their difference to be perceptible
Proportion 2 stim differ by in order to detect in humans for:
weight
light intensity
tone frequency
weight: 2%
light: 8%
tone: 0.3%
Signal detection theory
attempt to predict how and when someone will detect presence of a given sensory stimulus ( signal) in presence of other sensory stimuli in the background ( the noise)
4 possible outcomes
hit: signal present and detected
miss: signal present but not detected
false alarm: signal not present but person thought it was
correct rejection: signal not present and person did not think it was
Gesalt
organized whole perceived as more than the sum of its individual parts
when humans perceive an object, rather than seeing lines, angles, colors and shadows, they perceive the whole- a face, a table or dog
gesalt principles can be applied to any sensory modality
Emergence
Gesalt principle
when attempting to identify an object, we first identify its outline, which then allows us to figure out what the object is
only after the whole emerges do we start to identify the parts that make it up
Figure or ground
Gesalt principle
describes perpetual tendency to separate the figure or object from everything else ( background) based on a number of variables like size, shadow, contrast, color, etc
everything that is not figure is ground
Multistability
gesalt principle of multistable perception
tendency of ambiguous images to pop back and forth between alternative interpretations in our brains
Law of proximity
gesalt law of grouping
things that are near each other seem to be grouped together
nearby objects tend to be perceived as unit or group
Law of similarity
gesalt law of grouping
things that are similar tend to appear grouped together
we perceive similar objects as a group or unit
law of continuity
gesalt law of grouping
law of good continuation
we perceive smooth continuous line forms rather than disjoined one
when their is an intersection between two objects, people tend to perceive each object as a single uninterrupted object
Law of closure
gesalt law of grouping
we perceive things as a complete logical entity because our brain fills in gaps in the information
minds tendency to see complete figures or forms even if the picture is incomplete
law of common fate
gesalt law of grouping
objects moving in same direction or moving in synchrony are perceived as a group or unit
law of connectedness
things that are joined or linked or grouped together are perceived as connected
bottom up processing
begins with sensory receptors and works up to the complex integration of info occurring in the brain
also known as data driven processing
use bottom up processing when we have no little prior experience with the stimulus
Top down processing
occurs when brain applies experience and expectations to interepret sensory info
instead of focusing on sensory input, we use our prior experience and knowledge to impose our expectations on the stimulus, which tends to occur with stimuli we are more familiar with
Nervous system vs. Endocrine system :
time taken to act
length of the effects
NS is fast acting with relatively short term effects
endocrine system is slower at communicating signals but have generally longer lasting effects
connection between nervous and endocrine
neurons can signal the release of hormones from endocrine glans
What is one connection between the nervous and endocrine systems in the sympathetic nervous system?
sympa nervous system directly innervates the adrenal medulla to stimulate the release of epinephrine
Hormone
signal of endo system
molecule which is secreted into he bloodstream by endocrine gland and which has effects on distant target cells with the appropriate receptor
Endocrine gland
ductless gland whose secretory products are picked up by capillaries supplying blood to the region
Exocrine gland
secrete products into external environment by the way of ducts, which empty into the intestinal lumen or external world
Hormone receptor
polypep that possesses a ligand-specific binding site
binding of ligand ( hormone) causes the receptor to modify target cell activity
tissue specificity of hormone action is determined by whether the cells of a tissue have the appropriate receptor
Autocrine activity
when signalling molecules modify the activity of the cell that secreted them
ex. T cells secrete interleukin 2, which binds to receptors on the same T cell to stimulate increased activity
Hormone classes
2 classes
Hydrophillic such as peptides and aa derivatives, bind to receptors on cell surface
hydrophobic such as steroid hormones bind to receptors in the cellular surface
Peptide hormones
synthesized in rough ER and modified in the Golgi
stored in vesicles until they are needed and released by exocytosis
dissolve in blood plasma in the blood stream because they are hydrophilic
communicate with interior of target cell by the way of a second messenger cascade
Mechanism of peptide hormone on receptor cell
peptide hormone first messenger which must bind to a cell surface receptor
receptor is a polypeptide with a domain on the inner surface of the plasma membrane that contains the ability to catalytically activate a second messenger
end result of second messenger activation is that the function of proteins in the cytoplasm is changed
key feature of second messenger cascades is signal amplification, which allows a few activated receptors to change the activity of many enzymes in the cytoplasm
overall effect of peptide hormones
modify activity of existing enzymes in the cytoplasm, effects are exerted rapidly, minutes to hours from time of secretion
duration of effects is brief
Two subgroups within the peptide hormone category
polypeptides and amino acid derivatives
Polypeptide hormone examples
Insulin, complex tertiary structure with disulphide bridges
secreted by beta cells of the pancreatic islets of Langerhans in response to elevated blood glucose and binds to cell surface receptor with cytoplasmic domain processing protein kinase activity
Amino acid derivatives and example
derived from single amino acids and contain no peptide bonds
ex. Tyr is parent molecule for catecholamines ( including epinephrine) and thyroid hormones
Catcholamines
act like peptide hormones
Epinephrine is an example
small cyclic molecule secreted by adrenal medulla upon activation of the sympathetic nervous system
binds to cell surface receptors to trigger a cascade of events that produces the second messenger cyclic AMP cAMP and activates protein kinases in the cytoplasm
Thyroid hormones
act like steroid hormones
incorporate I into their structure
enter cells, bind to DNA and activate transcription of the genes involved in E mobilization
Steroid hormones
hydrophobic molecules synthesized from cholesterol in smooth ER
diffuse freely thru biological membranes
not stored but diffuse into blood soon after they are made
if not needed, then it is not made
because of the hydrophobicity, they cannot be dissolved in the plasma
what holds the steroid bound to a plasma protein?
no bond- just hydrophobic interactions
mechanism of steroid hormones
small hydrophobic steroid hormone exerts its effects upon target cells by diffusing thru plasma membrane to bind with a receptor in the cytoplasm
once it has bound its ligand, the steroid hormone-receptor complex is transported into nucleus, where it acts as a sequence-specific regulator of transcription
because steroid hormones must modify transcription to change the amount and type of proteins in the cell, effects are exerted slowly , over a period of days and persist for days to weeks
endocrine glands that secrete steroids and peptides
steroids regulating sexuality, reproduction and development are secreted by the testes , ovaries and placenta
steroids regulating water balance and other processes are secreted by adrenal cortex
all other endocrine glands secrete peptide hormones
structure of peptides vs steroids
pep: hydrophilic , large ( polypeptides) or small ( aa derivs)
st: hydrophobic, small
site of synthesis for peptides vs steroids
pep: rough ER
st: smooth ER
Regulation of release for peptides vs steroids
pep: stored in vesicles until a signal for secretion is received
st: synthesized only when needed and then used immediately, not stored
transport in bloodstream for peptides vs. steroids
pep: free
st: stuck to protein carrier
specificity for peptides vs steroids
pep: only target cells have appropriate surface receptors (exception: thyroxine =cytoplasmic)
st: only target cells have appropriate cytoplasmic receptors
mechanism of effect for peptides vs steroids
pep: bind to receptors that generate second messengers which result in modification of enzyme activity
st: bind to receptors that alter gene expression by regulating DNA transcription
timing of effect for peptides vs. steroids
pep: rapid, short-lived
st: slow, long-lasting
Feedback regulation example with calcitonin
function of calcitonin is to prevent concentration of calcium in the serum from peaking above normal levels, and amount of calcitonin secreted is directly proportional to increase in concentration of calcium in serum above normal
when concentration of calcium becomes elevated, calcitonin is secreted
thus when concentration of calcium in serum levels fall, calcitonin secretion stops
falling serum Ca level ( which is regulated) feeds back to the cells which secrete calcitonin ( regulators)
the serum Ca level is a physiological endpoint which must be maintained at constant levels
demonstrates the role of endocrine system in maintaining homeostasis
homeostasis
physiological consistency
tropic hormones
hormones that regulate hormones
meta regulators
role of ACTH
stimulate increased activity of portion of adrenal gland called the cortex, which is responsible for secreting cortisol and other steroid hormones
tropic hormone
does not directly affect physiological endpoints
regulates another regulator ( cortisol)
cortisol
regulates physiological endpoints including cellular responses to stress and serum glucose
feedback regulation for ACTH
level of ACTH is influenced by the cortisol
when cortisol is needed, ACTH is secreted, and when the serum cortisol increases sufficiently, ACTH secretion slows
inhibitory secretion
negative feedback or feedback inhibition
when the secretion of hormone inhibits further secretion
most feedback in endo is negative
Portion of brain which controls much of endocrine system
hypothalamus, located at the center of the brain
hypothalamus role in endocrine system
controls endo by releasing tropic hormones that regulate other tropic hormones called releasing and inhibiting factors or hormones
Ex of hypo regulation of endocrine system
hypo secretes corticotrophin releasing hormone ( CRH or CRF) F stands for factor
role of CRH is to cause increased secretion of ACTH
inhibited by cortisol like ACTH secretion
damage to connection between hypo and pituitary
is fatal, unless daily hormonal replacement therapy is given
hypothalamic-pituitary control axis
endocrine control center
hypothalamus and pituitary
hypo controls pituitary by secreting hormones into bloodstream
unique mini circulatory system is provided for efficient transport of hypothalamic releasing and inhibitory factors to the anterior pituitary
hypothalamic pituitary portal system
hypothalamic hypophysial portal system
blood supply which links the hypothalamus to the pituitary gland
pituitary gland
hypophysis
has 2 halves: front ( anterior) and back ( posterior)
general rule for blood leaving the heart
moves through a capilliary bed before returning to the heart, since pressure drops substantially in capiliaries
portal system blood flow
portal system consist of 2 capilliary beds in sequence, allowing for direct communication between near by structures
2 portal systems you need to understand
hypothalamic pituitary portal
hepatic portal system ( from GI to liver)
Anterior pituitary
adenohypophysis
normal endocrine gland
controlled by hypothalamic releasing and inhibiting factors ( essentially tropic hormones)
posterior pituitary
neurohypophysis
composed of axons which descend from the hypothalamus
consist of neuroendocrine cells from the hypo
neuroendocrine cells
neurons that secrete hormones into the bloodstream
hypothalamic neurons that send axons down to post.r pit.y are an examples
hormones of posterior pituitary
ADH ( antidiuretic hormone or vasopressin)
causes kidney to retain water during times of thirst
oxytocin : causes milk let-down for nursing as well as uterine contractions during labor
Are the hormones of the posterior pituitary created by the axon termini in the posterior pituitary or somas in the hypothalamus ?
All hypothalamic and pituitary hormones are peptides, no protein synthesis at axon termini. Therefore, ADH and oxytocin must be made in nerve cell bodies in the hypothalamus and transported down the axons to the posterior pituitary .
Is epinephrine secreted by duct into the bloodstream?
No. Endocrine hormones are not secreted through ducts.
Hormones which have broad effects on metabolism and energy usage
Thryoid hormone and cortisol
Thyroid hormone
produced from Tyr in the thyroid gland and comes in 2 forms, with 3 or 4 I atoms per molecule
production increased by thyroid stimulating hormone (TSH) by the anterior pituitary , which is regulated by the hypo and the CNS
Mechanism of action of thyroid hormone
bind to a receptor in the cytoplasm of cells that regulates transcription in the nucleus
effect of regulation: increase overall metabolic rate and body temperature and to stimulate growth in children
exposure to cold increases the production of thyroid hormone
Cortisol
Secreted in response to ACTH from the pituitary by the adrenal cortex
Effects of cortisol
help body deal with stress
helps to mobilize glycogen fat stores to provide energy during stress and increase consumption of proteins for energy
effects are essential, removal of adrenal cortex can result in death of animals exposed to even a little stress
Long term effects of cortisol
negative
including suppression of the immune system
Would an inhibitor of protein synthesis block the action of thyroid hormone?
Yes. Thyroid hormone binds to a receptor that regulates transcription. The mRNA stimulated by thyroid hormone receptor in the nucleus must be processed and translated before effects of thyroid hormone can become evident.
Would the production of ATP by mitochondria be stimulated or repressed by thyroid hormone?
Thyroid hormone stimulates basal metabolic rate throughout the body. More ATP is consumed so mito is stimulated to make more ATP
Would thyroid hormone affect isolated mitochondria directly?
No Thyroid hor affects mito indirectly, thru regulation of nuclear genes
releasing and inhibiting factors : class and gland which releases it
peptides
hypothalamus
releasing and inhibiting factors:
target
effect
target: anterior pituitary
effect: modify activity
growth hormone: class and gland which releases it
peptides
anterior pituitary
growth hormone:
target
effect
target: throughout the body, but primary one is the liver
effect: increase bone and muscle growth, increase cell turnover rate
prolactin: class and gland which releases it
peptide
anterior pituitary
prolactin:
target
effect
target: mammary gland
effect: milk production
thyroid stimulating hormone : class and gland which releases it
tropic hormone
peptide
anterior pituitary
TSH:
target
effect
target: thyroid
effect: increase synthesis and release of TH
adrenocorticotrophic releasing hormone (ACTH) : class and gland which releases it
peptide
tropic hormone
anterior pituitary
ACTH:
target
effect
target: adrenal cortex
effect: increase growth and secretory activity in adrenal cortex
lutenizing hormone (LH) : class and gland which releases it
gonadotropic hormone
peptide
anterior pituitary
LH:
target
effect
target: ovary, testes
effect: ovulation, testosterone synthesis
follicle stimulating hormone (FSH) : class and gland which releases it
gonadotropic hormone
peptide
anterior pituitary
FSH:
target
effect
target: ovary, testes
effect: follicle development, spermatogenesis
antidiuretic hormone (ADH) : class and gland which releases it
aka vasopressin
peptide
posterior pituitary
ADH:
target
effect
target: kidney
effect : water retention
oxytocin : class and gland which releases it
posterior pituitary
peptide
oxytocin:
target
effect
target: breast, uterus
effect: milk letdown, contraction
thyroid hormone : (TH) class and gland which releases it
aka thyroxine
modified amino acid
thyroid
TH:
target
effect
child: necessary for physical and mental development
adult: increase metabolic rate and temperature
calcitonin: class and gland which releases it
thyroid C cells
peptide
calcitonin:
target
effect
target: bone , kidney
effect: lowers serum calcium ion concentration
parathyroid hormone ( PTH): class and gland which releases it
parathyroids
peptide
PTH:
target
effect
target: bone, kidney small intestine
effect: raises serum calcium ion concentration
thymosin: class and gland which releases it
found in children only
peptide
thymus
thymosin:
target
effect
T cell development during childhood
target: white blood cells
epinephrine : class and gland which releases it
modified amino acid
adrenal medulla
epi :
target
effect
sympathetic stress response, rapid
target: muscles and blood vessels
cortisol : class and gland which releases it
glucocorticoid
steroid
adrenal cortex
cortisol:
target
effect
longer term stress response, increase in blood glucose concentration, increase protein catabolism, decrease inflammation and immunity
target: liver, fat, muscles
aldosterone : class and gland which releases it
mineralcorticoid
steroid
adrenal cortex
aldosterone:
target
effect
target: kidney
increase sodium ion reabsorption to increase blood pressure
sex steroids : class and gland which releases it
steroids
adrenal cortex
sex steroids:
target
effect
not normally important, but an adrenal tumour can over produce these, leading masculinization or femininization
insulin: class and gland which releases it
absent or ineffective in diabetes mellitus
secreted by beta cells
peptide
endocrine pancreas ( islets of Langerhans)
insulin:
target
effect
decrease blood glucose and increase glycogen and fat storage
glucagon: class and gland which releases
alpha cells secrete
peptide
endocrine pancreas ( islets of Langerhans)
glucagon:
target
effect
increase blood glucose and decrease glycogen and fat storage
somatostatin: class and gland which releases
peptide delta cells secrete endocrine pancreas ( islets of Langerhans)
somatostatin:
target
effect
inhibits many digestive processes
testosterone: class and gland which releases
steroid
testes
testosterone:
target
effect
male characteristics, spermatogenesis
estrogen: class and gland which releases
steroid
ovaries or placenta
estrogen:
target
effect
female characteristics, endometrial growth
target: female reproductive system
progesterone: class and gland which releases
steroid,
ovaries or placenta
progesterone:
target
effect
endometrial secretion, pregnancy
target: mammary glands, uterus
atrial natriuretic factor (ANF) class and gland which releases
peptide
heart secretes this
ANF:
target
effect
target: kidney
increase urination to decrease blood pressure
erythropoietin class and gland which releases
peptide
kidney
erythropoietin:
target
effect
target: bone marrow
increase RBC synthesis
SC:
specific functions
Specific: controls simple stretch and tendon reflexes
controls primitive processes such as walking, urination and sex organ function
Medulla:
specific functions
Specific: - controls autonomic processes such as blood pressure, blood flow , heart rate, respiratory rate, swallowing and vomiting
- controls reflex reactions such as coughing and sneezing
- relays sensory info to the cerebellum and thalamus
- rhythymicity centers found here
Pons: specific functions
Specific:
- controls antigravity posture and balance
- connects spinal chord and medulla with upper regions of brain
- relays info to cerebellum and thalamus
- receives info from vestibular apparatus in the inner ear, which monitors acceleration and position relative to gravity
Cerebellum: specific functions
Specific:
- Integrating center for complex movements
- coordination of complex movement, balance and posture , muscle tone, spatial equilibrium
- receives info from vestibular apparatus in the inner ear, which monitors acceleration and position relative to gravity
Midbrain: specific functions
Specific:
- integration of visual and auditory info
- visual and auditory reflexes
- wakefulness and consciousness
- coordinates info on posture and muscle tone
- contains much of reticular activating system (RAS) , which is responsible for arousal or wakefulness.
Thalamus: specific functions
Specific:
- relay and processing centers for somatic ( conscious) sensation
- relay info between the spinal cord and cerebral cortex
Hypo: specific functions
Specific:
- controls homeostatic functions ( such as temp regulation, fluid balance, appetite) through both neural and hormonal regulation
- controls primitive emotions such as anger, rage , sex drive
- controls pituitary gland
- contains centers for controlling emotions and autonomic functions, has a major role in hormone system especially since it has a primary link between nervous and endocrine systems and by controlling pituitary gland, is fundamental control center for endocrine system
Basal nuclei: specific functions
Specific:
- regulate body mvmt and muscle tone
- coordination of learned mvmt patterns
- general pattern of rhythm mvmts ( such as controlling the cycle of arm and leg movements during walking)
- subconscious adjustments of conscious mvmts
- voluntary motor control
Limbic system: specific functions
Specific:
- controls emotional states
- links conscious and unconscious portions of the brain
- helps with memory storage and retrieval
Cerebral cortex: Specific functions
Specific:
- divided into 4 lobes ( parietal, temporal, occipital , frontal) with specialized subfunctions
- conscious though processes and planning, awareness and sensation
- perception and processing of special senses ( vision, hearing, smell, taste, touch)
- intellectual function ( intelligence, learning, reading, communication)
- abstract thought and reasoning
- memory storage and retrieval
- initiation and coordination of voluntary mvmt
- complex motor patterns
- language ( speech production and understanding)
- personality
