psb exam 2

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Pharmacokinetics

process by which drugs are absorbed, distributed within the body, metabolized, and excreted

Oral administration (by mouth)

not all drugs can pass the barriers of digestive tract contents (stomach acid, enzymes) and walls

Weak acids

from stomach to bloodstream

Weak bases

from intestines to bloodstream

Liquid more easily

absorbed than solids

Must be hydrophilic

to be carried in blood

Blood brain barrier

Non-ionized (fat soluble); Active transport system

Needs to travel from blood to extracellular fluid

Must be small enough to pass through pores of capillaries

Sublingual

drug placed beneath the tongue absorbs into blood via capillaries that supply mucous membrane of mouth

Intrarectal

suppositories inserted into rectum; Used when drug would cause stomach upset

Inhalation

vaporous substance inhaled into lungs Fast acting - short route from lungs to brain Ex: Nitrous oxide

Topical administration

drug absorbed directly though skin (e.g., topical anesthetics, nicotine patches)

Insufflation

drug makes contact with mucous membrane of nasal passage

Intravenous (IV)

injection of substance directly into vein (bloodstream) Rapid effect - travels to brain within seconds Fewest barriers to brain, but must be hydrophilic

Intraperitoneal (IP)

substance injected though abdominal wall into peritoneal cavity Slower effect than IV, but still fast

Intramuscular (IM)

substance injected into muscle Absorbed into bloodstream via muscle capillaries

Subcutaneous (SC)

substance injected into space under the skin Small quantities

Intracerebral administration

substance injected directly into brain Only requires small doses because no barriers to target Used when substance cannot cross BBB

Intracerebroventricular (ICV)

substance injected into ventricular system of brain Widely distributed throughout brain Rarely employed Used to administer antibiotics for infection

Larger people less sensitive to drugs than smaller people

Greater dilution of drug in body fluids

Females 2x as sensitive to drugs as males

Small size and hormonal differences

Elderly may be 2x as sensitive to drugs as young

Less effective barriers to drug absorption; Less effective processes for metabolism and elimination

Dose-response curve

graph depicting the magnitude of a drug's effect as a function of quantity administered

Therapeutic index

measure of drug's margin of safety which provides a ratio of dose that produces desired effect in 50% of animals and dose that produces toxic effects in 50% of animals

Effects of a drug can change

one administration to another

Tolerance

decrease in effectiveness of a substance due to increased administration

Metabolic tolerance

reduced sensitivity to a substance that results from the increased ability of cells to metabolize the substance

Learned tolerance

with increased administration, people learn to function under the influence of substance

Cellular tolerance

a change that takes place in a cell in which the activity of the cell adjusts to the excitatory or inhibitory effects of a drug Decrease in # of receptors Decrease in affinity for drug

Sensitization

Increased behavioral response to the same dose of drug More likely to develop with occasional use

Affinity

the readiness with which two molecules join together

Agonist

A drug binds to a receptor and increases the effectiveness of neurotransmission

Direct agonist

binds to receptor of NT and mimics effects (competitive)

Indirect agonist

Binds to alternative site on receptor and results in ion channel opening (non-competitive)

Antagonist

A drug that binds to a receptor and causes a decrease in the effectiveness of neurotransmission (blocks or inhibits) natural effect

(site of drug action)Interference with NT re-uptake from synapse

Drug binds to transporter to inactivate - blocks re-uptake (agonist)

(site of drug action)Interference enzymatic deactivation of NT in synapse

Drug binds with enzyme to prevent enzyme function (agonist)

Regulate quantity of NT release

Drugs that excite/ stimulate receptor-DECREASE NT release (antagonist)

Drugs that block receptor-INCREASE NT release (agonist)

Dendritic autoreceptor Neuro-regulators that affect NT release

Drugs that stimulate- DECREASE NT release (antagonist)

Drugs that block - INCREASE NT release by preventing hyper-polarization (inhibitory agonist)

Glutamate

excitatory effect in the brain; interacts with other neurotransmitter systems. o Most common excitatory NT in the CNS

Gamma-aminobutyric acid (GABA)

Inhibitory effect in the brain; interacts with other neurotransmitter systems.

Glycine

inhibitory effect; found in spinal cord and lower brain stem.

Acetylcholine

Learning, memory, REM sleep. o PNS Functions: muscle contraction.

Dopamine

Voluntary movement, attention, learning, reinforcement, planning, problem solving. • Produces both excitatory and inhibitory effects based on receptor

Norepinephrine/ Epinephrine

Vigilence. o PNS Functions: Autonomic nervous system regulation (regulate heart rate, blood pressure, etc.)

Serotonin

Mood regulation, eating, sleep, dreaming, arousal, impulse control. o PNS Functions: involved in the enteric nervous system (digestive tract)

Histamine

wakefulness. o PNS Functions: Immune response

Opioids

Reinforcement, pain modulation. o PNS Functions: Pain modulation.

Synthesis of neurotransmitters Glutamate.

• Synthesized from glutamine (precursor) by glutaminease (enzyme) o After, they are stored in vesicles. ▪ Vesicle glutamate transporters: proteins in the vesicle membrane that pump glutamate into a vesicle.

Synthesis of neurotransmitters GABA

• Synthesized from glutamic acid (precursor) by the action of glutamic acid decarboxylase or GAD (enzyme)

Neurotransmitter clearance from synapse Glutamate

• Removed from the synapse by excitatory amino acid transporters and broken down into its building block precursor glutamine by the enzyme glutamine synthase. o Too much glutamate in synapse can cause glutamate excitotoxicity: toxic overstimulation of the postsynaptic cell by excess glutamate

Neurotransmitter clearance from synapse GABA

• Take up by the presynaptic neuron that released it and surrounding glial cells. • 3 different transporters that take up GABA: GAT1, GAT 2 (located on neuron), and GAT3 (located on glial cell) o Glial cell is primary mechanism for clearing synaptic GABA. o Inhibitors of GATs- reuptake inhibitors- nipecotic acid and tiagabine (anticonvulsant)

Dopamine 3 major systems

nigrostriatal, mesolimbic, mesocortical

Nigrostriatal- substantia nigra—> neostriatum (caudate + putaman)

▪ Movement control ▪ Parkinson's disease

Mesolimbic- VTA—> nucleus accumbens, amygdala, hippocampus

▪ Reward system

Mesocortical- VTA—> prefrontal cortex

▪ Short-term memory, planning, problem solving

Neurotransmitter Release

• Molecules of neurotransmitters are stored in small "packages" called vesicles (see the picture on the right). Neurotransmitters are released from the axon terminal when their vesicles "fuse" with the membrane of the axon terminal, spilling the neurotransmitter into the synaptic cleft.

GABAA

• Ionotropic receptor o Associated with post-synaptic Clchannel (opens) o Many binding sites ▪ Bicuculline- direct antagonist- produces seizure ▪ Picrotoxin- indirect antagonist (Channel Blocker) • Stimulant and convulsants effects • Can be used to treat barbiturate overdose. ▪ Target for sedative hypnotics and anti anxiety agents • Muscimol- direct agonist- derived from mushrooms and has sedative hypnotic effect. • Indirect agonists o Binds alcohol, barbiturates, benzodiazepines, and neurosteroids ▪ Benzodiazepines require binding of GABA to work ▪ Barbiturates do not need GABA to open channe

GABAB

Metabotropic receptor (G-protein coupled receptor- GPCR) o Presynaptic- autoreceptor that decreases Ca2+ influx therefore decreasing GABA release. ▪ Mainly found in autonomic nervous system o Post-synaptic- increases effluent of K+ o Baclofen- agonist- muscle relaxant and anti-spastics agent. ▪ Used to treat muscle issues related to multiple sclerosis and cerebral palsy Saclofen- agonist does not produce seizure and can be used as anti epileptic

GABAC [or GABA- rho]

ionotropic receptor o Slow to initiate Cl- influx o Found in retina

The ability to sense electromagnetic radiation has two important benefits:

1. As electromagnetic energy travels quickly, we receive optical information about objects and events without much delay

2. Electromagnetic radiation travels in straight lines. As a result the images produced by radiation retain the geometrical characteristics of objects.

Wavelength

how far radiation travels between oscillations.

Sensory transduction

conversion of a sensory stimulus from one form to another • A receptor cell converts the energy in a stimulus into a change in the electrical potential across its membrane

Short wavelength

HIGH frequency High rates mean that radiation travels a short distance between oscillations

Long wavelength

LOW frequency

Photon

smallest unit of light energy

Color of light determined by hue, saturation and brightness.

o Wavelength determines hue o Intensity of light corresponds to brightness o Saturation refers to purity of light (mixtures of wavelengths that make up light)

If light made of all wavelengths

white

Pupil

an opening or gap in the iris that regulates amount of light coming in.

Iris

pigmented ring of muscles located behind the cornea. Gives eye its characteristic color.

Cornea

transparent structure located at the front of the eye. Responsible for 80% of eyes focusing ability.

Lens

transparent structure composed of layers located behind the iris. Provides 20% of eye's focusing power.

Retina

interior lining of the back of the eye.

Photoreceptors

rods and cones

Rods

o Low light illumination, contrast. o Located at the periphery.

Cones

o Responsible for our color vision, daytime vision, and information regarding fine details in the environment. o Fovea- central region of retina and contains only cones. o Located at the back of the eye.

Bipolar layer

contains bipolar and horizontal cells

Ganglion layer

contains ganglion and amacrine cells

Opsin

large protein (several forms) o Rhodopsin- opsin in human rods.

Components of Visual Photopigments

enzyme cascade, isomerization, opsin, retinal

Retinal

Small light sensitive lipid molecule. o Synthesized from vitamin A o Reacts to light triggering visual transduction

Isomerization

process whereby a photopigment changes its shape in response to the absorption of light. o Breaking photopigment —> hyperpolarization of photoreceptor. o Isomerizing a single visual pigment —> thousands of chemical reactions.

Enzyme cascade

sequence of reactions generated by the activation of a visual pigment molecule whereby

Accommodation

• process whereby the lens changes its shape in order to bend light ray so that images are focused more sharply on the retina. o Near point- distance at which one can no longer adjust lens to bring objects into focus.

Rods resting potential

-40 (baseline= dark) currently releasing glutamate o Response to light (stimulus)- hyperpolarized (-90)—> reduce amount of glutamate its releasing to the bipolar cell

BIPOLAR resting potential

(At baseline dark—> hyperpolarized (-90), not releasing NT ▪ Response to light: depolarize; release glutamate

GANGLION resting potential

(at baseline-dark- hyperpolarized, no AP, no NT ▪ Response to light: fire AP, transmits it signal to brain

Receptive field

region of the environment that is detected by a particular neuron in retina or other area of visual system.

Fixation point

visual field of receptors that receive input from photoreceptors in fovea. ▪ One receptor provides info to one ganglion cell

Acute vision

detects fine detail.

Peripheral region/ on one side

visual field of receptors that receive input from photoreceptors in the periphery. (Outside the fovea) ▪ Many receptors converge on single ganglion cell. • Less acute; detects illumination

Round receptive fields

On Cells, Off Cells, On/ Off Cells

On Cells

Respond to light with increased firing rate.

Off Cells

Respond to lack of light with increased firing rate.

On/ Off Cells

respond briefly to light with increased firing rate and respond again briefly when light turned off

round receptive cells are involved

in visual reflexes ▪ Not directly involved in form perception

Daltonism

color deficiency; named for John Dalton.

Monochromat

person who needs only one wavelength to match any color. ▪ Very rare hereditary condition. ▪ Only rods and no functioning cones ▪ Ability to perceive only in white, grey, and black tones. ▪ True color-blindness ▪ Poor visual acuity. ▪ Very sensitive eyes to bright light. ▪ Less drastic form has one functioning cone • Still lack ability to discriminate color • Wavelengths perceived as gradations in intensity

Dichromat

person who needs only two wavelengths to match any color.

3 types of dichromat

protanopia, deuteranopia, tritanopia