A.P. and M.B. (EXAM 2)

Which sensory neurons do not have dendrites but receptors for physical stimuli in specialized regions

retinal photoreceptors and mechanism receptors

Anterograde definition

transport of macromolecules and mitochondria from neuron cell body to the axon

Retrograde definition

transport of macromolecules and mitochondria from axon to neuron body

what are the 4 major ionic species

Na+

k+

Cl-

Ca2+

Nernst equation

used to calculate potential when the membrane is permeable to only 1 ion

Chord equation for membrane potential

membrane potential will depend on the relative conductances for the major ions and the equilibrium potential for those ions

Where

E= electromotive force (in volts)

G= conductance( in siemens) found using 1/R

electromotive force equation( V or E)

I*R

where

I= ion current

R= resistance

what happens to conductance (G) when channels open? closed?

when opened= G is high

when closed =G is low

Goldman-Hodgkin-Katz voltage equation

says that when a membrane is permeable to several different ions , the resting membrane potential depends on permeability , charge , and concentrations of all of the ions, and temperature

when the membrane is more depolarized which ion channels are open

K+ channels open

Cl- channels open

Na+ channels open

when the membrane is more hyperpolarized which ion channels are open

K+ channels open

Cl- channels open

How are graded potentials generated? describe them

By the opening of ligand-gated ion channels

small, hyper polarizing or depolarizing and decrement with distance due to ion leakage

difference between action potentials and graded potentials

action potentials are all or noting while graded potentials are incremental

in the dark , what gates are opened and what flows in

cGMP-gated channels are opened and Na+ flows in producing a dark current

How would you describe the relationship between the fraction of closed cGMP-gtaed channels and sodium current

linear

Most cells in the retina elicit what type of potentials and which cells are the exception

local; retinal ganglion

the large spikes of action potential are due to the presence of

voltage gates Na+ channels

Why can't graded potentials be propagated across long distances in neurons?

because of the leakage of plasma membrane

the velocity of the propagation depends on

the time constant( τ) of the membrane which is the time to charge and to discharge

what is the significance of the Hodgkin and Huxley model

- measured current-voltage relations

- found currents are carried by Na+ and K+ ions through axon membranes

- components of membrane conductance

resting membrane potential is

-70mV

threshold potential is

-60 mV

Depolarization potential is

+30 mV

hyper polarization potential is

-90 mV

which cranial nerves are apart of the CNS

Olfactory and optic

Simple receptors

neurons with free nerve endings

complex neural receptors

have nerve endings enclosed in connective tissue capsules

special senses receptors

cells that release neurotransmitter onto sensory neurons, initiating an action potential

Where is conduction velocity the fastest?

large diameter myelinated fibers

A and B fibers are myelinated by

Schwann cells

Are C fibers myelinated?

no

retino-hypothalamic tract

non image forming visual system

from RGC to suprachiasmatic nucleus then to pineal gland and contains body clock

retinotectal tract

to the olivary pretectal nucleus , controls pupillary light reflex

vesicular release of neurotransmitter steps

1. action potential is transmitted and depolarizes the axon terminal

2. depolarization opens voltage gated Ca channels and releases neurotransmitter

3. neurotransmitte binds to post-synaptic receptors and change the conductance in the post synaptic cell and elicit an electrical signal

Acetylcholinerase

enzyme responsible for the immediate breakdown of acetylcholine when release from the nerve ending; prevents overstimulation of cholinergic receptor sites

in the CNS what is the most common EXCITATORY neurotransmitter

glutamate

in the CNS what is the most common INHIBITORY neurotransmitter

GABA

can glutamate be inhibitory

yes ; glutamate is inhibitory for the bipolar cells of the retina

How is glutamate cleared from the synaptic cleft?

by reuptake via transporter

and

by diffusion and uptake by local glial cells

How is GABA cleared from the synapse?

reuptake using transporters on glia and

diffusion and uptake

can GABA be excitatory

yes

GABA-A receptor activation triggers membrane depolarization when there is Cl- efflux

ionotropic receptor definition and examples

receptors that are coupled to ion channels and affect the neuron by causing those channels to open

examples:

GABAR-A/C,

GLUR AMPA/KA, Nicotinic AChR(NMJ)

metabotropic receptors

receptors that are associated with signal proteins and G proteins

Examples :

GABA-B, mGLUR, MusAChR (brain only)

the ionotropic muscle type receptors are also called__________receptors and are composed of how many subunits

nicotinic receptors; composed of 5 subunits

the metabotropic muscle type receptors are also called ____________receptors and are composed of how many subunits

muscarinic receptors; composed of 1 subunit

all receptors are classified by

their agonist

receptor agonist definition

substances that mimic the action of the neurotransmitter

Exp:

Nicotine and muscarine that Mimic Ach

receptor antagonists definition

substances that block the action of the neurotransmitter

Exp:

Atropine and Curare

Receptor inverse agonists

binds to the same receptor- binding site as an agonist

, antagonizes the effects of an agonist and exerts the opposite effect by suppressing spontaneous receptor signaling (when present).

NMDA, AMPA, and Kainate are what type of glutamate receptors and are classified as?

ionotropic receptors and are fast excitatory

mGluR6 is what type of receptor and what is it responsible for

Metabotropic Group III receptor that is slow inhibitory

responsible for the ON pathway in the retina

how is glutamate release sustained in photoreceptors

a ribbon synapse that acts as a conveyor belt for the synaptic vesicles

what neurotransmitter is released by photoreceptors when put in the dark

glutamate

what are all the factors that influence post-synaptic response

1.strength, number and dendritic location

2.temporal and spatial summation between EPSP and IPSP

3.interactions between excitatory and inhibitory synapses

4. location and density of post synaptic ion channels

neuromodulator definition

substance other than a neurotransmitter, released by a neuron at a synapse and conveys information to adjacent or distant neurons, either enhancing or damping their activities.

neurohormones

produced and released by neurons in the brain, rather than by the endocrine glands, and delivered to organs and tissues through the bloodstream

Exp: pituitary gland hormones

G- Proteins

bind GTP in the active conformation and GDP in the inactive conformation

-catalyzes the hydrolysis of GTP to GDP +P

what is the difference between heterotrimeric G proteins and Monomeric G proteins

heterotrimeric G proteins have 3 subunits while monomeric have 1

what are the four families of heterotrimeric G proteins

Gαs

Gαi/Gαo/(GT*)

Gαq/Gα1

Gα12/Gα13

Gα12/Gα13 function

interacts with small (monomeric G proteins) to regulate cytoskeleton

Gαq/Gα11 function

activates beta-type phospholipase C (PLC-β) enzymes.

which hydrolyzes PIP2 => DAG and IP3 which activates protein kinase C and release stored calcium into cytoplasm respectively

Gαi/Gαo/(GT*) function

inhibits adenylate cyclase (AC)

Gαs function

stimulates adenylate cyclase (AC) and thereby decreases the production of cAMP

what is the main superfamily of the Small (monomeric) G proteins

Ras family

Activation cycle of G-protein by a G-protein- coupled receptor receiving ligand steps

1.Ligand binding to GPCRs (2) induces a conformation change

2.conformation change facilitates the exchange of GDP for GTP on the α subunit of the heterotrimeric complex

3.Both GTP-bound Gα in the active form and the released Gβγ dimer can then go on to stimulate a number of downstream effectors

4.When the GTP on Gα is hydrolyzed to GDP the original receptor is restored .

What is the significant advantage of g-protein signaling

amplification of the desired molecules

second messengers

components of molecular "circuits" inside cells that regulate metabolism, synthetic activity, ion channels, and other behavior of the cell

Main second messengers in the body are

Cyclic adenosine monophosphate (cAMP)

Cyclic guanosine triphosphate (cGMP)

Calcium (Ca2+)

Diacylglycerol (DAG)

cAMP/PKA signaling pathway allows for what and used what type of G proteins

mRNA transcription

uses Gs + Gi

PIP2/DAG/IP3 signaling pathway

ligand binds to G-protein receptor=> PIP2 is hydrolyzed => Ca2+ is released => Ca 2+ binding proteins are activates => produces DAG which activates protein kinase C

Catecholamines

dopamine, norepinephrine, epinephrine

Pupil constriction via sphincter pupil smooth muscle constriction is governed by which receptors and what pathway is the receptor a part of

governed by Cholinergic muscarinic M3 receptors

(M3 are GPCR to PIP2/DAG/IP3 pathway)

Pupil dilation via dilator muscle constriction is governed by which receptors and what pathway is the receptor a part of

governed by Adrenergic alpha1 receptors

(Alpha 1 are GPCR to PIP2/DAG/IP3 pathway)

Activation of rhodopsin by absorption of a photon leads to what and what does it cause

closure of cation channels in the plasma membrane of the rod outer segment.

This interrupts the dark current and hyperpolarizes the rod photoreceptor.

Activation of cone opsins leads to

lose cation channels in cone outer segments and hyperpolarize the cones.

Termination of the phototransduction cascade steps

(1) Inactivation of rhodopsin

(2) Inactivation of transducin

(3) Inactivation of phosphodiesterase (PDE)

(4) Activation of guanylate cyclase

spectral sensitivity

the degree to which a photopigment molecule absorbs light of different wavelengths

photoreceptors are color blind

First line of immune defense

skin and mucous membranes

second line of immune defense

phagocytic WBC

antimicrobial proteins

inflammatory response

third line of immune defense

lymphocytes and antibodies

the physical barriers of the innate immune response refers to

tightly packed epithelial cells

waterproof in skin

epithelial shedding

the physiological barriers of the innate immune response refers to

fevers

low pH

coughing/sneezing

antimicrobial molecules

interferons

interferon general mechanism

1. released from infected cell

2. after being released, it binds to surface receptors on neighbor cells

3. neighboring uninfected cell synthesized antiviral proteins that interfere with viral replication

cytokines

protein secreted by a cell that influences the cell itself or neighboring cells for the immune/inflammatory response

lysozyme

enzyme that degrades peptidoglycan cell wall of bacteria

most abundant protein found in tearfilm

Opsonins description

receptors that recognize molecules that are found on pathogens and bind to them allowing for immune cells to phagocytose the pathogen

examples are C3B and antibodies

Pathogen-associated molecular patterns (PAMPs)

Molecules (like LPS or Flagellin) associated with groups of pathogens that are recognized by cells of the innate immune system.

toll-like receptors

recognize molecular patterns unique to pathogens then stimulates the production of cytokines, chemokine, and antimicrobial peptides

when does the acquired immune response improve

after each subsequent exposure

epitope

3D molecular arrangement on antigen recognized by immune system

Cells of the acquired immune system

memory cells , B lymphocytes, T lymphocytes

B lymphocytes

produce antibody and humoral immunity

T lymphocytes

help B lymphocytes produce antibody and help destroy organism

cell mediated immunity

all cells of the immune response derive from where and as what originally

derive from the bone marrow and differentiate into CLP and CMP

most to least common WBCs

"Never Let Monkeys Eat Bananas"

Neutrophils [most]

Lymphocytes

Monocytes

Eosinophils

Basophils [least]

common myeloid progenitor differentiates into

granulocytes

mast cells

monocytes

megakaryocytes

common lymphoid progenitor (CLP) differentiates into

TC

TH

B cell

Natural killer cell

Haematopoietic stem cells differentiate into

Common myeloid progenitor and common lymphoid progenitor

granulocytes consists of

neutrophils, eosinophils, basophils

neutrophils description

most commonn

first to arrive when infection is induced

phagocytize and destroy foreign organisms