Drugs
1.Molecular level
2. Behavioral level
nt in the same class share the same chemical structures
Drugs definition
substances that are taken in small amounts, effects experiences, mood, &/or health.
What is bad about this definition is is very broad and we have to be very specific.
1. Low doses drugs, usually act on particular classes of nt receptor
2. Studied at mult
Dopamine
can bind to D1 and D2 receptors. Nt can bind to different receptors that are specific to that receptor. nt and receptor lock each like lock and key
EX: Nt and receptor subtypes
nt= Acetylcholine (ACh)
Receptor= 1. Muscarinic and Nicotinic.
These receptors are where ACh can bind.
Agonist such as nicotine mimic ACh and binds to nicotinic.
When nicotine binds to Muscarinic or Nicotinic, it tricks the brain into thinking that it is
Ligand
substance that binds receptor
Type of ligand:
1. Endogenous (Ach)= occur naturally in the body ( the body makes it) (Agonist)---is produced inside the body.
2. Exogenous(nicotine) =agonist= Introduced into the body and compete with the nt binding site.---
Endogenous
occurring naturally in the body. The body makes it by itself.
ex: ACh
3. Antagonist ligand= block nt
4. Noncompetitive ligand= the bind somewhere and do not block or compete with the nt.
Exogenous
is introduced into the body. The body does not make it.
EX: Nicotine
Drug Binding
Drugs with multiple effects typically
1. bind more than one receptor.
2. bind receptors for a long time and
3. have higher affinity for that receptor= low concentration
Higher affinity drugs stay in the receptor binding site for a long time.
Low affinity
Affinity ( how sticky is the drug)
1. Need higher concentration of low affinity drug. We need a lot so that they can stay in the receptor for a long time.
2. Need low concentration of high affinity drug. We need little bit because we already have too much.
Agonist ligand
1. Unbound receptor is normally closed.
2. Exogenous ligand= is a drug or toxin that resembles the endogenous ligand and is capable of binding to the receptor nd activating it also. Is classed as Agonist
EX:
Nicotine binds to nicotinic receptor in place o
Antagonists
Some substances bind to receptors but do not activate them. Instead, they simply block agonists from binding to the receptors.
When nt anatagonists bind to receptor sites, it will prevent the nt from going to post-synaptic neuron and nothing happens in th
Noncompetitive Ligand
Drug does not compete with nt for binding site. The drug finds another site on the receptor and modulate effect of the nt.
modulate: exert a modifying or controlling influence on.
Pre-synaptic Affect
1. Action potential arrive at the axon terminal
2. Causing vesicles to rupture and release transmitter into the synaptic cleft
3. Molecules of neurotransmitter bind to postsynaptic receptors and alter functioning of the postsynaptic cell. In this example,
Routes of Administration= How the drug enter the body
1. Rate of parental
2. inhalation ( Gas)
3.Slow route (Oral)
Routes of Administration= ways the drug enter the body
Rate of parental (Needle)
Absorption:
1. Intravenous-- into vein (1 faster)
2. Intraperitoneal Abdominal-- body cavity
3. Intramuscular- muscle
4. Sub-cutaneous-- under skin ( more dense and the drug enter slower)
Absorption of drug depends on density of
Routes: Inhalation
1. Gases-lungs: A lot of surface area exposed to air & capillaries
2. Smokes different from gas b/c includes vapor & ash particles, but absorbed similarly
3. Solids- inhaled through nose. Not as efficient as lungs as gas.
Damage respiratory system. & lead
Slow Routes
Oral- absorbed mostly through intestines, then through capillaries. They have to make it through the stomach first.
Transdermal--not readily absorbed through epidermis (skin).
EX: Nicotine patch
It will take a long time for the drug to go across the skin.
Types of drugs
1. Opiates
2. Marijuana
3.Alcohol
4. Hallucinogenic Drugs Alter Sensory Perception
5. Stimulants (6. Nicotine, Amphetamine, Ecstasy, Cocaine)
Opiates
Helps relieve pain
Types of Opiates: Morphine and Heroin = are highly addictive
1. Morphine is the major active substance
analgesic properties (pena queductal gray) Queductal gray=channel in the brain
Endogenous agonist: opioid Peptides
Two types:
1. Enkephalins
2. endorphins
Both of these opioid make us feel better when we cause pain to ourselves.
There are things we make ourselves that help us when we cause pain to ourselves. The brain release opioids to relieve us from pain naturally.
Aqueductal
channels in the brain
All brain make their version of morphine. After someone had surgery. doctors used do not give them pain killers. However, doctors give their patients pain killers after surgery because if they do not give them pain killers they will
Marijuana
Has a wide array of effects/ multiple effects
1. Is the most widely used illegal drug
2. The active gradient for marijuana is THC
Fake or synthetic THC has been created so that it has less consequence on the patient than the real marijuana. There are THC
Endogenous equivalent is anandimide
our brain version of marijuana receptor .
All of our brain have marijuana receptors because we make our own version.
Once people take marijuana, they can take other drugs very easily.
Alcohol
Most widely used legal drug
1. Abuse indirectly leads to neuronal damage in the frontal lobe, cbllm, hippocampus
2. Acts predominantly on GABA receptors
3. Alcoholism shows a strong hereditary component (if someone grandparents or parents were alcoholic,
Some Effects of Alcohol Are
Some Effects of Alcohol are reversible with abstinence
Figure 4.11 in the book
abstinence=the fact or practice of restraining oneself from indulging in something, typically alcohol
Hallucinogenic drugs alter
sensory perception
1. Alters or distort perceptions
hallucinogenic drugs act on:
1. Amine transmitter system
2. LSD= which acts on serotonin (5-HT) receptors
4. Stimulates dopamine release
Stimulants Increase
stimulates activity in the nervous system and does not stimulate behavior
Types of stimulants
1. Nicotine
2. Amphetamine
3. Ecstasy
4. Cocaine
Nicotine
1. Activates nicotinic receptors, ACh receptor subtype
2. Nicotinic receptors found at neuromuscular junction, autonomic ganglia (parasympathetic and sympathetic ganglia) and CNS
3. Increases heart rate, blood pressure, secretion of stomach acids
Nicotine
Amphetamine
Why is it interesting in a bad way
Are bad
1. because more is released but is not recycled.
2. Blocks re-uptake and degradation of nt.
3. This causes a lot of nt to be in synaptic gap---keep on affecting post-syntactic neuron gap
Stimulant: Amphetamine
have synaptic effect and psychological effect
synaptic effects:
1. Causes the release of catecholamines from pre-synaptic terminal
2. Blocks the re-uptakes of catecholamines
4. Compete with nt for the inactivated enzyme (agonist)
psychological effect:
Inc
Stimulants: Ecstasy
Effects on brain structure
Is not whether or not neurons are working. Is just to see if they are there or not.
Normal Brain Versus exposure to Ecstasy
Affects the brain structure.
14 days after the normal brain is exposed to ecstasy, a lot of brain neurons were not there.
After 7 years of not taking ecstasy, the brain recovered.
If you stop taking ecstasy your brain structure can recover.
Stimulants:cocaine
1. Affects on brain Function= is the brain working and what is working.
2. Initially used as an anesthetic (benefit)
EX: dentists use it to put on the teeth and it name come from coca cola.
3. Cocaine blocks re-uptake of amines, especially Dopamine. This
Cocaine Abuse and Brain Activity
1. Normal brain
2. Only temporal and occipital lobes were there after 10 days of using cocaine.(this means this person can see and can hear but cannot reason well)
3. After 100 days of using cocaine, the person can still hear and have vision. Things did n
Drugs Used to Treat Psychological Disorders
1, Antipsychotic Drugs
2. Antidepressants Drugs
3. Anxiolytics combat Anxiety
Antipsychotic Drug
Used to treat schizophrenia
When the drug was first created, the first kind was
1. Typical neuroleptics
1st generation were selective D2=dopamine antagonists
2. Atypical neuroleptics (2nd generation)--less side effects. Also impacted dopamine receptors
Do
Antidepressants Drugs
Used to treat affective (mood) disorders
1. Monoamine oxidase Inhibitors (MOAIs)
MOA breaks down manoamine nt .
We do not want MOA to break monoamine neurotransmitters. So MOAI is used to prevent MOA from breaking monoamine nt.
2. Tricyclic-block reuptake
Why do we need MAO
Because it needs to break down serotonin in a Non-depressed person because they have too much of it.
However, when someone is depressed, they do not have a lot of serotonin. For this reason we do not want MAO to break down serotonin in depressed people be
Downregulation
When someone is depressed they are experiencing a down regulation/ decrease serotonin. So MAOI is used to inhibit MAO
When reuptake is blocked, there will be more serotonin in the synapse
Anxiolytics Combat Anxiety
Benzodiazepines= class of anxiolytics includes diazepam (Valium)
1. Acts on GABA receptors but not nt site
2. Endogenous activator for benzodiazepine site?
3. Allopregnanolore= acts on GABA receptors which inhibits stress hormones
GABA is our main Inhibit
Neuromagilator
benzodiazepine and does not compete with GABA it binds somewhere.
Drug Abuse is Pervasive & Costly/
consequence of drug abuse
1. Medical expenses due to health effects.
2. Crimes committed
3. Costs of addiction treatment & controlling drug trafficking
4. Drug babies born W/brain impairments
If mom takes cocaine when she is pregnant it has less impact on the baby than alcohol.
Le
Different Models of Approaching Drug Abuse
1. Moral model= drugs are bad= Drugs are bad and the person who is taking them is a bad person
2. Disease Model= Addiction is a disease= How can we treat persons medically.
3. Physical dependence model= Addiction occurs b/c people develop a physical depen
Different Models of Approaching Drug Abuse continue
Positive Model= Addiction b/c the drug acts as a positive reinforce= the drug gets ride of the disease or pain.
Physical dependence not necessary= Physical competent is not necessary
Reinforcement Pathway:
Ventral tegmental area releases DA onto nucleus a
Medolimbocardical pathway
...
The rat story
Every time a rat presses the level, they get reward. The animal will keep pressing the level to get the drug. The exposure is so rewarding that you can food deprive the animal. The animal will prefer to press the bar so that they can get the drug
The rat
See figure 4.19b
The rat was looking for Acl but they got dopamine instead. Level oof Dopamine arise to 700
Treatment and Presentation
1. Agonist are drugs that produce common addiction states
2. Antagonists to addictive drug= prevent you from getting pleasure from the drug and will not let the drug bind
3. Antiuraving medications= fell anxious
4. Medications that block drug metabolism
Tobacco
A highly addictive North American plant whose leaves (usually dried and smoked) are a major source of nicotine.
fetal alcohol syndrome
a disorder, including intellectual disability and characteristic facial abnormalities, that affects children exposed to too much alcohol (through maternal ingestion) during fetal development
caffeine
a stimulant compound found in caffeine, cacao, and other
dysphoria= unpleasant feeling; opposite of euphoria
s
Nucleus accubens: receives DA from ventral tegmental area
Insula= A region of cortex lying below the surface, within the lateral sulcus, of the
enocannabinoid
An endogenous ligand of cannabinoid receptors; thus, an analog of marijuana that is produced by the brain.
Chapter 5
...
Hormones
Chemicals secreted by cells
1. Travels through bloodstream
2. Target cells are involved in producing physiological effects.
EX: Hormone is growth hormone
Examples of Hormone
1. Endocrine= release hormones within the body
2. Homocostasis= maintenance of a constant internal environment
What is the difference between hormone and nt
1. Nt travels short distances
2. Hormones travel long distances in the body
The same chemical with the same structure can act as both hormone and nt depending on how far it travels.
EX: Norepinephrine can act as both nt and hormone
You do not want to be t
Endocrine Glands
release hormone within the body
EX: Hormone Travel Through the Bloodstream
Figure 5.2
Group 1. Left undisturbed, young roosters grow up to have normal male characteristics
Group2: It testes are removed during development, roosters do not grow up to have normal male characteristics
Group3: If one of the testes is implanted cavity, young roo
Types of Chemical Communicatio
Neurocrine= neuronal communication= communication bwt neurons and is short distance
Autocrine= acts on itself
paracrine= regulation of neighboring cells ( parasympathetic and sympathetic )
Figure 5.3
Types of Chemical Communication continued
Endocrine-secretion into bloodstream
1. Pheromore= signals to conspecies=members of the same species
2. Allomore-signals to other species
Armpit study: Participants were asked to smell the Armpit of each person to see what movie they were watching.
Figure
Difference in Neuronal Vs. Hormonal Communication
1. Neuronal comm. goes to a Precise destination
2. Neuronal comm. is faster= they are faster because they travel long distance
3. Neuronal impulse Is all-or-none= If threshold is not met, the A.P will not be fired.
Hormonal message is graded= different am
Similarities in Neuronal Verus Hormonal Communication
1. Both produce & store chemicals for later release
2. Both stimulate target cells w/chemicals
3. Many different types of nts. hormones
4. Chemical needs to bind to specific receptors
EX: growth hormone will bind to growth hormone receptors. This will bin
Neuronal versus Hormonal Commutation
Figure 5.3
...
Hormones Stimulate
Figure 5.4
Several Types of Cells/ Targets cell Receive Several Hormones
One hormone can stimulates can stimulate several types of cells in it class. such as hormone A can stimulate A 1, A 2, A3
You can have one hormone affect 3 different types of hormones.
Hormone
Hormone can be classified by
Chemical structure
figure 5.6
Types of hormone based on their chemical structure
1. Protein hormones= strings of amino acids= different amino acids
2. Amine hormones-strings of a single type of amino acid= same amino acids over and over again
3. steroid hormones-composed of four internnected carbon rings= same amino acids over and ove
Hormone Binding can exert Different Effects
1. Protein hormones & most amine hormones bind receptors on target cell's membrane, & activate 2nd messengers. ( They are faster because the receptors are sitting on the cell membrane)
2. Steroid hormones pass through the membrane bind receptors inside th
Protein & Amine Hormones Act quickly
1. When the extracellular site is bound, shape of the receptor changes, iniating a 2nd messenger
2. Specificity is determined by the selectivity of the receptor (only some cells produce the receptor)
EX: When receptors do not work, the body thinks the hor
Steroid Hormones Act Slowly
Pass in and out of many cells
2. Hours to take effect
3. Alters protein production for slow, but long-lasting effects
4. Steroid receptor cofactors-needed for a cell to respond to steroid
Feedback Control Mechanisms
The Hormone system & Evaluates effects.
Output of the hormones feedback to inhibit the drive for more hormones.
When too much hormone are made, the body stops it.
Too little are made, the body makes it.
What happens when there is not to much hormone?
If this is not there, it will keep making hormone. When it is there, it tells the body to stop making hormones
Figure 5.8 a and b
Figure 5.8 c, d
Hormone Chain of command
Hypothalamus=Brain areas send signals to other brain areas.
Hypothalamus is divided into
1. Posterior pituitary
2. Anterior pituitary
Posterior Pituitary is divided into
Vasopressin and oxytocin
which both target organs
The target organs produce Bio response
Anterior pituitary
hormone release
Is made up of 6 tropic hormones :
1. Adrenal
2. Gonads
3. Milk Production
Multiple target organs
More hormones
multiple target organs
bio response
Relationship between hypothalamus and posterior pituitary gland
1. Hypothalamus makes vasopressin and oxytocin and then transport them along axons to posterior pituitary.
2. Posterior pituitary- receives axons and hormones (vasopressin and oxytocin) from hypothalamus
3. Posterior pituitary releases the hormones into c
Posterior Pituitary Hormones
1. vasopressin= increases blood pressure.
It main effect is : antidiuretic conserves water
2. Oxytocin- stimulates contraction of uterine muscles
Uterine muscles Triggers Milk letdown reflex and mediates sexual arousal and affectionate response
EX: Bonds
Milk Letdown Reflex
1. infant suckling produces brain activity in the mother
2. Increased brain activity results in inputs to the hypothalamus
3. Oxytocin produced and released
4. Oxytocin causes cells of mammary glands to contract; milk released
5. Baby continues sucking un
Anterior pituitary and Posterior pituitary
See book
figure 5.13
Anterior Pituitary
Figure 5.13 and figure 5.10
...
Hypothalamus and Releasing Hormones
1. Hypothalamus axons converge above pituitary stalk (as oppose to going through it)
The pituitary stalk (This region contains a bed of capillaries (hypothalamus pituitary portal system)
2. Hypothalamus secrets hormones into capillaries where blood carrie
Tropic Hormones released by Anterior Pituitary are
1. Adrenocorticotropic hormones (ACTH)
2. Thyroid stimulating hormone (TSH)
3. Luteinizing hormone (LH)
4. Follicle-stimulating hormone (FSH)
5. Prolactin promoter hormone
6. Growth Hormone (GH)
Adrebicirticotropic hormones (ACTH)
Anterior pituitary control of the Adrenal cortex and Thyroid
1. Adrebicirticotropic hormones (ACTH)---controls production and release of adrenal ctx hormones (which control release of steroid hormones)
2. Thyroid stimulating hormone (TSH)--controls releas
Anterior pituitary control of Gonads
3. Luteinizing hormone (LH)--females--stimulates release of eggs from ovaries
Males--testosterone production
4. Follicle-stimulating hormone (FSH)--females--secretions of estrogen
male--sperm production
Anterior pituitary control of Milk Production and Body Growth
5. Prolactin-promotes mammary development for lactation (females) = breast develop= 12 and 13 years old
6. Growth Hormone (GH)--influences growth of cells and tissues
produced and released during early stages of sleep
Giving someone growth hormone for the
Organs Affected by Anterior Pituitary Hormones
1. Adrenal Gland
2. Thyroid Gland
3. Gonads
The Adrenal gland: Two Parts
1. Adrenal Cortex-outer bark of the adrenal glands releases Adrenocorticoids
There are 3 classes of Adrenocorticoids:
Glucortioids. EX: cortisol ( hormone that is released when people get stressed)
Mineralocorticoids. EX. Aldosterone (function is water co
Cortex means
bark= outer layer. Andrenal cortex has two layers: ouside and inside.
When adrenal goes to ACTH, it releases hormone
While ACTH goes to Adrenal cortex, it can release one of the 3 classes of hormone
Thyroid Hormones Regulate Growth and Metabolism
Thyroid hormones
1. Amines act (bind) like steroids ( meaning for amines to bind to receptor it has to go through the cell membrane to bind to receptor)
2. Main hormone: thyroxine, triothyronine
3. Production of thyroid hormones requires iodine in order t
Gonads Produce steroid Hormones
Regulating Reproduction
1. Trigger reproductive behavior and gamete production.
Testes:
Leyodig= cells produce and secrete testosterone
Ovaries: 2 main classes of hormones
1. Progestin: EX: progesterone
2. Estrogen: EX: Estradiol
Progestines--Angrogens--Estrogen
But the sexes di
Hypothalamus produces
1. gondrotropin hormone= releasing, GnRH
2. Anterior pituitary (LH and FSH)
Produces Testes
Hypothalamus produces (GnRH)
Anterior Pituitary
LH and FSH
goes on to produce
Ovaries
Hypothalamus is always the one releasing hormone. The released hormone always
Sexual Differentiation
Process by which individuals develop either male or female bodies/ behavior
It takes multiple steps and multiple influences
Sexual Determination
event that decides whether an individual becomes male or female ( is one time event)
1. Sex is determined early in life
Mammals' sex is determined at conception ( sperm and egg meet only one time)
2. Egg contributes X Chromosomes;
Sperm contributes X or Y
Sexual differentiation of the gonads
makes a male and female different
Sex Chromosomes Direct
Sexual Differentiation of Gonads
1. Gonads are indifferent early in development (can develop into either testes or ovaries)
2. Mammals: Y chromosomes contain SRY (Sex determining region of Y chromosome)
SRY is responsible for developing testes
No Y chromo
Gonadal Hormones
Direct Sexual Differentiation of the rest of the body
Two ducts: Wolffan ducts and mullerian ducts
Wolffan ducts= male sex organs and develops epididymis, vas deferens, and seminal vesicles
Mullerian ducts= female sex organs and develops fallopians tubes,
6 weeks undifferentiated
Everybody have a wolffan duct and mullerian duct while in the womb. But once they are born, the male develop wolffan duct and female develop mullerian duct
So You've Got Testes, Now what?
1. Males: wolffian ducts develop b/c of testosterone produced by testes
2. Mullerian ducts shrink b/c anti-mullerian (AMH), a protein hormone flourishes
3. Non-wolffian structures are masculinized b/c 5 alpha reductase (an enzyme) locally converts testost
What happens when XY chromosome/ SRY is expressed
1. Genetic Sex: Gene Expression
Gonadal Sex= (sex hormone secretion):
2. Anti-mullerian hormone (AMH) occurs and testosterone (T) is produced
3. Phenotypic Sex:
1. AMH causes mullerian duct to shrink
2. Testosterone induces Wolffian ducts to form epididym
What happens when SRY does not develop
1. Genetic Sex: Gene expression
2. No SRY expressed
3. Ovaries produce, no AMH, no T
4. in absence of AMH, mullerian ducts form fallopian tubes, uterus, and inner vagina
5. In absence of testosterone, wolffan ducts regress, and no prostate or bulbo-urethr
Turner's syndrome (single X) chromosome
Individual develops into female w/ poorly developed ovaries
this person cannot have children because they have one ovary
Departures
1. Congesnital Adrenal Hyperplasia (ACH) created by genetic mutation, adrenal glands produce excess androgens (ex: of testosterone)
XX: appearance of genital organs is btw male and female
This male has a lot of androgens but not AMH
This male has both the
3. Androgens in sensitivity
XY: gene for androgen receptor is defensive=
Not able to respond to androgens
Testes produce AMH and testosterone
No wolffian structures
Externally: Labia & Clitons
Internally: No mullerian structures
This person has a problem with the Gonads. The SRY gen
Gonads hormones direct sexual
Differentiation of the Brain and behavior
Organizational hypothesis
hormones affect the developing brain and permanently alter behavior
This happens only during a sensitive period
(EX: researchers give a female rat male hormone, and she develops like a male)
receptors on a sex organs and in the brain
Early Testosterone
Secretions Result in masculine Behavior in Adulthood
------------------ infiltrate the entire body, affecting all tissues that develop differently in males and females
Estrogen
Is a male hormone
and It masculinizes the developing brain of rodents
1. Small doses of estrogen after birth masculinizes behavior
2. Aromatase ( an enzyme) converts testosterone to estradiol= which then masculinize the brain
3. Males: testosterone enters
Why isn't female brain masculinized?
females: alpha fetoprotein binds estrogen and prevents them from entering the brain
Females have estradiol flowing around in their brain
Testosterone is converted in two ways
1. alpha reeductase convert testosterone to DHT=male
2. Aromatase converts testosterone to estradiol= female
One goes in male direction (DHT) and one goes in female direction (estradiol)
See your book
1. Genetic sex: Gene expression
2. Gonadal Sex: Week 7 of gestation
3. Hormone secretion: After week 7
4. Phenotypic sex: Week 10 of gestation
5. Sex assignment: occurs at birth
6. Early gender identity: age 3-4 years
7. Pubertal gender identity
8. Adult
Sexual Dimorphic Areas
1. song control regions in male songbirds
2. The ------- of the hypothalamus (SDN-POA)
3. Spinal nucleus of the ------------------------(SNB)
Look in the book
The condition in which males and females of the same species show pronounced sex differences in
sadnaksl look in the book
...
Social influences affect
Sex differentiation of the N.S
1. Mother rat licks males more, leading to greater survival of the NSB nucleus ( the rat mom has to link the child so that they can pie)
NSB nucleus is important for male sexual behavior in rat
2. Humans treat babies differe
Chapter 6
...
Basic ideas Underlying Perception
1. Receptor cells= detect a specific type of environment stimulation and transform it into electrical signals (transduction)
2. Receptor receptors: detects a specific type of environmental stimulation.
There are different receptor for hearing, touching, a
Transduction
conversion of environmental or chemical signal into electrical signals.
This happens because the brain does not understand chemical signals.
Messages from different sense
are kept separate by separate nerve tracts
This is how the brain know the different signals that enter in the brain because they are kept separated.
Sensory Systems for a Particular Animal Are Selective
3 different species: Elephant, cat, and Human
1. Elephants hear low frequencies that humans don't
2. Cats hear high frequencies that humans don't ( cats can hear really loud frequencies that are outside of our range of hearing.
Sensory Processing Begins in Receptor Cells
All pathways starts with receptors
1. Receptor cells-- specialized to respond to a particular type of stimulus and perform sensory transduction
2. If enough stimulation is reached, A. P will be initiated
3. Stimulation below threshold elicits generator po
Specialized receptors in the Skin
1. Free nerve endings pain temperature
2. Merkel s disc (touch)
3. Meissner s corpuscle (touch)
4. hair follicle receptor
5. Pacinian corpuscle (vibration)
6. Ruffini s ending (stretch)
We have different receptors, some pain, touch, and vibration
Example of a Sensory Receptor at Work:
The Pacinian corpuscle
1. Vibration deforms the corpuscle
2. Leading to mechanical stretch of the axon tip.
3. stretching enlarges membrane pores, allowing Na+ ions to enter
4. If the generator potentials reaches threshold, an action potential is produced
The bipolar Pacinian Corpuscle
see book
A close-up of the Pacinian Corpuscle's Nerve Ending
see book
Generator and Action Potentials
see book
Only the important signals will meet threshold. The unimportant one do not meet threshold. this means we only pay attention to important signals
Sensory information
...
Ways od Coding Information
Problem:
With so many possible differences in stimuli, how can electrical and chemical signaling account for them all??
1. Coding Stimulus Instensity
As the intensity of the stimulus increases, more neurons are recruited to fire. More neurons have to be probe to be fired.
Low threshold neuron do not need a lot of stimulation to be fired. High threshold neuron need a lot of stimulation to fire. More neu
Neuronal Recruitment Encodes
Stimulus Intensity
See graph
As the intensity of the stimulus increases, more neurons are probe to fire. Low threshold neuron do not need a lot of stimulation to be fired. High threshold neuron need a lot of stimulation to be fire. More neurons are fired
2. Coding stimulus type
W/in a stimulus modality, stimuli can be distinguished by labeled lines
---different categories process different type of stimuli line
Different pathways process different types of stimuli
3. Coding stimulus
Location
Location of a stimulus is determined by the location of the receptor stimulated
---for several sensory systems, cells are arranged in an orderly map-line manner
4. Coding Stimulus Identity=
(know what something is)
Brain perceives patterns of stimulation and compares them w/ previous patterns
More properties of Sensory information Processing
...
1. Receptor response can decline
with maintained stimuli.
Adaptation= a progressive decrease in receptor response due to maintain stimulus. We do not pay attention to umimportant things.
We do not notice the clothes touching our body or the sound of ticking clock because our sensory syst
Plastic Receptors Show a Rapid decline
Electrical recording
-------stimulus
b) Moderate stimulus
a) Strong stimulus
Somatosensory receptor touch stimulate finger number 5. Once it does this, neurons quickly fire --does not care if the stimulus is weak, moderate or strong. It quicly adapt and l
2. Sensory Inputs can be suppressed
Accessory structures can reduce the level of input.
EX: Muscle that makes sound to protect our hear
The brain can sendd projection to lower levels which can influence receptor output.
3. Successive Levels of the CNS process
sensory information
EX: involved in hearing and vision
1. Information is processed along pathways leading from sensory perceptions to the highest levels of the brain
2. --------sensory systems has it own distinctive----------
3. Different levels and regio
Successive Levels of CNS sensory Information processing
...
3a Receptive fields of Sensory Neurons
Is the part of the environment that a receptor responds to.
EX: somatosensory receptive field in the cat
EX: Skin
The receptive field for ears= sound, eyes, what you see
Receptive field for sensation= touch
Stimulating Somatosensory
Receptive Fields for touch
1. Touch outside receptive field has no effect
2. Touch in center of receptive field excite
3. Touch in surround inhibits
(1, 2, 3 are receptive field for cortical neuron A)
4. Touch outside receptive field has no effect
5. touc
Somatosensory Receptive Fields
have Excitatory center/ inhibitory surround= the center of is excitatory, while the surrounding area is inhibitory
Inhibitory center/excitatory surround---the center is inhibitory, while the surrounding area is excitatory
Info goes from skin to thalamus.
3b. Regions of Cerebral Cortex
1. Primary sensory cortex--Main source of input to other fields for the same modality
2. Secondary sensory cortex--receives input from thalamus and primary sensory cortex
Primary and Secondary Areas of the Cortex
...
3c. Plasticity in Cortical Maps
1. Researchers used to think that adult brains could not undergo significant change
----they can undergo reorganization due to experience or learning. (
Brain can change)
We have a map of our environment in our mind. The map in our head can change.
Plasticity in Cortical Maps
If you cut finger 1, 2, 3, they will stop receiving sensory and the bran will expand.
If you cut the middle finger, the brain will also erase the middle finger sensory because it is not there.
Cortical Reorganization After Amputation of a Hand
The region formerly stimulated by receptors in the hand now responds to touch on face or arm.
EX: people who are born blind do not need occipital cortex. For this reason other brain area will take over (frontal, parietal, temporal)
Touch and Pain
Skin Has a Variety of Receptors for touch
1. Pacinian Corpuscle- vibration
2. Ruffini's ending-stretch
----slow--adapting
---They are tonic because hey will keep on firing
Skin has a variety of Receptors for Touch
3. Meissner's corpuscle--touch
----fast---adapting
---texture=scaly
4. Meerkel's disk--touch--sensitive to different stimulation
--slow--adapting
--good spatial resolution
---responsive to edges, isolated points
Sensory Receptors
...
Sensory Receptors continue
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Touch Receptors Responding to Braille
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Two Pathways Cary Sensory information from
Skin to Brain
Location w/in CNS is different
--carry different types of somatosensory information
1. Dorsal column system--touch
2. Anterolatoral system-- pain and temperature
More to the front and back
Dermatome
strip of skin innervated by a particular spinal root.
Bands of skin send sensory info to different dorsal roots of spinal cord.
EX: Shingles:
infection that causes a painful rash. Although shingles can occur anywhere on your body, it most often appears as
Brain cells are arrnaged according to
body plan
Topographic==there is a map in the brain. Some of the maps are easy to understand. Areas that are more important get a bigger representation in the brain then areas that are less important.
EX: Shoulder is less important because we do not use it
Cortical Columns
Show specific modality and Location
1. Each cortical cell has a precise receptive field and responds to only one submodality
2. W/in a column, all cells responds to same location and kind of stimulation
3. Column extends from layer 1 to layer VI
Modality=
Organization of the SS Ctx
Primary somatosensory cortex (SI) and Secondary somatosensory cortex (S2) all responds to touch
Columnar Organixation of the SS Ctx
One strip can be fast adapting and another one slow adpating
Pain
discomfort associated with tissue damage.
Serves adaptive purpose
Congenital insensitivity to pain (CIP),
person cannot feel (and has never felt) physical pain.
This is not good because the person will not know if something is painful. The people die early because they might hurt themselves and do not feel any pain.
Peripheral Origins of pain Info
1. A Delta fibers-large diamter, myelinated and high threshold
-----Sharp pain. (Pain occur very fast because they are myelinated and has to be strong in order to meet threshold)
2. C fibers--thin, unmyelinated
----longer lasting, dull ache.
(has low thre
Peripheral Medication Of Pain
(Special Mediate painl CNS Pathways )
1. Damaged cells release substances that excite nerve endings
2. Action potentials excite blood vessels and other cells to produce inflammatation
3. Information is relayed to brain
4. Pain fivers release glutamate as a transmitter and substance P as neuro
How does special CNS Pathways Mediate Pain?
--Use glutamate as a nt ( glutamate is our main extatory nt)
and--substance as a neuromodulator: Result
1. May affect later perception of pain
2. may mediate intense pain
EX; Science create models of mice to see how animals react to pain.
Neuropathic pain
--due to inappropriate signaling of pain by neurons.
-Nerve dmaage rather than tissue damage
-Pharitomlim pain--continued perception of chronic pain despite missing limb ( Ex: people looking themselves in the mirror by hiding their limb and think that the
Anterolateral System Carries pain Info
Just read it in PowerPoint, but do not have to know for exam
Pain Can be Controlled
1. Opiates drugs
--mimic endogenous opiods (enkephalin and endorphins)
--act in periaqueductal gray (brainstem)
--can inject locally
periaqueductal gray= Where receptors for Morphins and herioi are.
2. Skin stimulation--eletrical stimulation of nerves aro
Descending Pain pathway
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Gate Theory
To explain why thoughts and emotions influence pain perception
Gate theory--You cannot have signals from the cortex. Any Kind of distractiobns does not allow the pain signals to go up.
EX; Something coming from the cortex.