Exam 2

physiological signals in cell-cell communication

electrical (changes in Vm); chemical (mccs secreted into ECF)

local communication

communication between adjacent cells

long-distance communication

a combination of electrical and chemical signals that are sent throughout the body

types of local communication

* gap junction - direct cytoplasmic transfer
* contact-dependent - CAMs
* autocrine/paracrine

paracrine signals

chemical that acts on cells in the immediate vicinity of the cell that secreted the signal

autocrine signals

a chemical signal that acts on the cell that secreted it

hormone

chemical signals that are secreted into the blood and distributed by circulation

neurotransmitter

a chemical signal secreted by a neuron that acts on ionotropic receptors

neuromodulator

a chemical signal secreted by the nervous system that acts on metabotropic receptors

target cell

a cell that received a chemical/electrical signal

types of cell membrane receptors

1. channel
2. g-protein
3. enzyme
4. integrin

function of channels

opens/closes with binding

function of GPCRs

opens an ion channels, alters enzyme activity

function of enzyme receptors

activates an intracellular enzyme

function of anchor protein receptors

alters enzymes/cytoskeleton

transducer

converts a signal from one form to another

location of intracellular receptors

in the cytosol or nucleus

function of intracellular receptors

turns on a gene that acts on the nucleus to make mRNA

signal transduction

process in which an extracellular signal mcc activates a membrane receptor to create a response

function of Ca2+ as a signaling molecule

* w/ calmodulin - alters enzyme, gates ion channels
* other regulatory proteins - alters movement of contractile proteins, triggers exocytosis
* ion channels - initiates development of embryo

function of NO as a signaling molecule

causes vasodilation

function of CO as a signaling molecule

targets smooth muscle and neural tissue

function of H2S as a signaling molecule

relaxes blood vessels

function of lipids as a signaling molecule

* leukotrienes - constricts airways
* prostanoids - regulate sleep, inflammation, pain, fevers
* sphingolipids - regulate inflammation, cell growth, and death

function of cyclooxygenase (COX 1 + 2)

receptor for prostanoid lipids; can be inhibited by non-inflammatory drugs

desensitization

decreased cell response; drug tolerance

up-regulation

target cell inserts more receptors into its membrane

function of central receptors

receive information and send it to the brain quickly due to nearness

function of peripheral receptors

proprioceptors, chemoreceptors, thermoreceptors, etc.; located outside the brain

example of neuronal reflex

knee-jerk (patellar tendon) reflex

example of endocrine reflex

blood glucose increasing after a meal

example of neuroendocrine reflex

release of thyroid hormone

a pathology associated with signal pathways

vasopressin receptor’s half-life is shortened, which leads to congenital diabetes insipidus

a pathology associated with abnormal signaling mechanisms

the cholera toxin blocks G-protein activity, which promotes release of cAMP; ion channels stay open in the intestinal lumen, which causes massive diarrhea

function of CNS

controls intelligence, memory, personality, emotion, speech, and ability to feel and move

function of glial cells

protect and nourish neurons

function of dendrites

receive incoming signals in the nervous system

function of afferent division of CNS

receive sensory information

function of efferent division of CNS

send out commands to motor neurons

morphology of dendrite spines + pathology

have many processes to increase the surface area of the neuron; changes can indicated diseases such as Alzheimer’s, mental retardation

function of axons

transmits chemical and electrical signals from the CNS to target cells/tissues

axonal transport

moves materials up and down the axon

slow axonal transport

moves material by axoplasmic flow at 0.2-0.25mm/day

fast axonal transport

moves organelles at rates up to 400mm/day

functional categories of neurons

sensory, interconnected, efferent

sensory neurons

send info about temp, pressure, and light from sensory receptors to the CNS

interconnecting neurons

send and receive info withint the CNS

efferent neurons

send info from the CNS to target areas

function of myelin

prevent leakage of ions out of axons to perpetuate electrical signals and maintain the signal’s strength

function of mixed nerves

both send and receive info to/from the CNS

function of motor nerves

send efferent signals to targets tissues/cells

function of brain

center for registering and storing info, intellect, emotions, behavior, and memory

function of spinal cord

major pathway for info flowing back and forth between the brain and skin/joints/muscles

function of GABA

main inhibitory NT in the brain; amino acid NT

function of acetylcholine

depolarizes the post-synaptic cell

function of aspartate

excitatory amino acid NT in selected brain regions

function of glutamate

excitatory amino acid NT in the CNS

function of glycine

inhibitory in the spinal cord, but excitatory in the brain; amino acid NT

function of substance P

excitatory in the pain pathway

function of NO, CO as a neurocrine

excitatory gas NTs

function of eicosanoids

cannabinoid receptors; lipid NTs

function of enkephalins, endorphins

opioid peptide; inhibitory to mediate pain

synapse

region where an axon terminal meets its target cell

function of presynaptic cell

neuron sending info to another neuron

function of postsynaptic cell

receives info from another neuron

action potential

a brief and rapid change in cell membrane potential that results in an electrical signal

membrane potential

the separation of electrical charge across the membrane

average membrane potential

\-70 mV

factors that affect membrane potential

uneven distribution of ions, membrane permeability of ions

causes depolarization of the membrane

Ca2+, Na+ influx

causes hyperpolarization of the membrane

influx of Cl-

causes repolarization of the membrane

influx of K+

what changes occur in the membrane during an action potential

depolarization (Vm increases), repolarization (Vm decreases), hyperpolarization (Vm increases)

factors that influence the speed of an action potential

diameter of an axon, resistance to ion leakage

hyperkalemia and its effect on cell electrical activity

increased \[K+\] brings Vm closer to the threshold

hypokalemia and its effect of cell electrical activity

decreased \[K+\] makes it more difficult to create an action potential

ionotropic receptors

chemical-gated ion channels

metabotropic receptor

GPCR

IPSP

inhibitory postsynaptic potential; hyperpolarizing

EPSP

excitatory postsynaptic potential; depolarizing

how do electrical signals received by a neuron modify the release of NTs

a stronger electrical signals will result in a higher concentration of NTs released

axoaxonic synapse

a synapse created by an axon with another axon

components of chemical synapses

presynaptic cell, postsynaptic cell, NT, Ca2+ gated ion channel, postsynaptic receptors

release of NTs in synaptic transmission

1. action potential arrives at axon terminal
2. Ca2+ channels open
3. Ca2+ triggers exocytosis

effect of drugs on synaptic mechanisms

block undesirable effect or enhance a desirable effect

effect of cocaine on synaptic mechanisms

blocks the reuptake of dopamine, which also leads to the desensitization of the receptors

chemical vs. electrical synapse

use of NTs vs. electrical signals

how are NTs recycled/inactivated

astrocytes break down leftover NTs and they undergo endocytosis to reenter the axon terminal

function of cranium

provide support and protection for the brain

function of meninges

stabilize the neural tissue and protect it from bruising against the bones of the skeleton; dura mater, arachnoid membrane, pia mater

function of blood-brain barrier

protects brain cells from harmful substance and pathogens by sealing enodthelial cells of brain capillaries

function of cerebrospinal fluid

shock-absorbing fluid to prevent the brain from bumping against the interior of the hard skull

function of corpus callosum

connects the two hemispheres of the cerebrum and transmits signals between them

function of ascending/descending tracts of white matter in the spinal cord

carry sensory info to the CNS vs. carry commands to motor neurons

three specialization areas of the cerebral cortex

sensory, motor, association

cerebral lateralization

each lobe has special functions not shared by the matching lobe in the opposite side

function of cerebellum

processes sensory info and coordinate movement

function of thalamus

processes sensory info from the optic tract, ears, and spinal cord → cerebral cortex

function of hypothalamus

center of homeostasis and behavioral drives e.g., hunger, thirst

function of midbrain

controls the eye movement, relays signals for auditory and visual reflexes