Lecture 2: Communication & Endocrine System Flashcards
neurons
eukaryote cells (contrain a clearly defined nucleus) that communicate with each other using electrochemical signals
cell membrane
consists of 2 lipids (fat molecules) and phosphor heads
- separates the internal components of the cell from the immediate external environment of the cell
phospholipid layers
contain protein channels (e.g. ion channels, recognition molecules, or receptors) that allow certain molecules to pass from inside the cell (intracellular) to the outside of the cell (extracellular), or vice versa
ligand
binds to a receptor allowing an action to be formed, like an ion gate
neuron structure
consists of 3 components: the soma (cell body), axon, and dendrites
soma
contains the nucleus and mitochondria
atom
contains a nucleus that contains neutrons, protons, and electrons
- neutrons: neutral (either negative or positive)
- protrons: positively charged particles
- electrons: negatively charged particles
ion
when an atom is negatively or positively charged
ionotropic receptors
proteins in the cell membrane
- influences the flow of ions, to allow for depolarization and repolarization
depolarization
ionotropic receptors allow more positive ions into the cell, making the cell charge more positive
repolarization
the process of which a neuron restores its negative internal charge after being depolarized
metabotropic receptors
have a binding site for neurotransmitters, but no pore of their own through which ions can flow
- activate G proteins
G proteins
direct the signal to an enzyme that adjusts the activity of an ion channel
- bind to guanosine diphosphate (GDP) and guanosine triphosphate (GTP)
3 ways cells can be connected
- desmosome
- tight junction
- gap junction
desmosome
a structure in the cell membrane that allows cells to attach to each other, such as skin tissue
tight junction
in this case, the cells are seated against each other. at this junction, no passive substance can cross the membrane, like in the intestines
gap junction
small channels that run between cells to promote transport, as in the heart
endoplasmic reticulum (ER)
a network of membranes located in the cytoplasm
- consists of 2 membranes close to each other, between which cavities and channels are formed
- main function: to collect proteins to be sent to the golgi apparatus
rough ER
ribosomes attach to the rough ER
smooth ER
no ribosomes are attached but calcium is stored
golgi apparatus
the function of the golgi apparatus is to convert and store proteins, which are then transported to other destinations
mitochondria
produce energy that the cell needs, which they develop by generating large amounts of energy within the molecule adenosine triphosphate (ATP)
adenosine triphosphate (ATP)
energy-displacing molecules that store chemical energy (obtained from breaking down food molecules), which can then be used for such things as moving molecules
lysosomes
structures in the cytoplasm containing enzymes that can break down waste molecules in the cell
cytoskeleton
consists of microfilaments that provide movement, intermediate filaments, which provide the strength of a cell, and microtubules, through which substances are transported
radial glial cells
precursor cells that show the way to migrating nerve cells during central nervous system development and indicate the direction in which axons should grow
astrocyte
a star-shaped, branched glial cell in the CNS with long or short spurs
- support cells in the nerve pathway that lie between a blood vessel and a neuron
- remove some neurotransmitters, regulate ion concentration, and play a role in the development of the CNS by forming conductive branches through which neurons can grow
- can maintain neuronal homeostasis
- part of the blood-brain barrier
- involved in repair of the nervous system
microglia
small glial cells that occur in the mesoderm and are very important during injury
- active in monitoring their immediate environment for injury
- release inflammatory agents and help clear away dead material
ependymal cells
produce and secrete CSF
- form the epithelial layer of the fluid-filled cerebral ventricles
- have hair-like structures called cilia
- influence the direction of CSF flow
oligodendrocytes
cells positioned in the CNS and provide myelination to axons
- can lie around several axons
schwann cells
located in the peripheral nervous system and also myelinate sensory and motor neurons
- only lie around one axon
- repair myelin when damaged
myelin sheath
reduces the loss of electrical current to the extracellular fluid
white matter
refers to areas with many myelinated neurons
gray matter
consists of cell bodies and dendrites where there is no myelin
nodes of ranvier
allow neural flow to move along the axon much faster
multiple sclerosis
an autoimmune inflammatory neurological disease
- symptoms: “FATIGUE”
- Fatigue
- Altered vision
- Tinglish/numbness
- Incoordination
- Gait problems
- Urinary issues
- Extreme temperature sensitivity
multipolar neurons
contain many dendrites
bipolar neurons
have a single dendrite and a single axon
unipolar neurons
have a single axon and a dendrite that grows into an axon-like structure
afferent
when neural information runs into the central nervous system
efferent
when neural information leaves the CNS
motor neurons
send information from the brain to the muscles
- efferent
sensory neurons
send sensory information to the brain
- afferent
a potential
the difference between the positively and negatively charged area
cations
positively charged ions
anions
negatively charged ions
diffusion
the process by which ions move from a site of high concentration of the same ions to a site of low concentration through the random movement of the particles
concentration gradient
differences in concentration close to the cell membrane
- allows diffusion to occur
resting potential
the electrical charge in the cell membrane when there is no stimulation
action potential
is created when the potential difference exceeds the firing threshold (-50 mV)
depolarization
Na+ gates, which are closed at rest, open, allowing Na+ to flow into the cell and create a positive intracellular charge (+30 mV)
repolarization
K+ gates open, but are much slower and only open when the Na+ channels are deactivated
- K+ now flows out of the cell, causing the intracellular charge to become negative again to the resting potential (-70 mV)
hyperpolarization
eventually the K+ channels close, but because they are slow, they only close when the charge becomes more negative than -70 mV
absolute refractory period
period when the cell cannot fire at all
- during the repolarization and depolarization period
relative refractory period
the cell can fire, but it is more difficult because of the hyperpolarization of the membrane
saltatory conduction
an action potential can jump from node to node via the nodes of Ranvier
pulmonary conduction
occurs with unmyelinated axons activating adjacent gates
excitatory postsynaptic potential (EPSP)
associated with the opening of Na+ channels, allowing sodium ions to enter
- increases the likelihood of an action potential
inhibitory postsynaptic potential (IPSP)
associated with the opening of K+ channels, allowing potassium ions to exit
- reduces the likelihood of an action potential
temporal summation
the summation of potentials that come shortly after each other
spatial summation
the summation of potentials that are close in location
synapse
consists of a presynaptic membrane, a synaptic gap, and a postsynaptic membrane
microtubules
provide material for making neurotransmitters
presynaptic terminal
axonal mitochondria provide energy to convert precursors into neurotransmitters
vesicles
package neurotransmitters before they are transported to the synapse
heteroreceptors
receive input from other neurons that use other neurotransmitters as messengers
exocytosis
when vesicles release the neurotransmitter into the synaptic cleft
full fusion
a type of exocytosis
- the membrane of the vesicle fuses with the cell and the contents of the vesicles enter the synaptic cleft (requires calcium)
kiss-and-run fusion
a type of exocytosis
- the vesicle releases a transmitter through a pore in the cell membrane
- there is no full integration, so part of the neurotransmitter remains in the vesicle
- myosin determines how long the vesicle is open
autoreceptors
help regulate the synaptic environment by providing feedback to the presynaptic neuron
endocytosis
the process for the absorption of neurotransmitters
three forms of endocytosis
- pinocytosis: small particles, namely liquids, are brought in the cell via invagination
- phagocytosis: solids are internalized into the cell
- receptor-mediated endocytosis: the ingestion of a specific molecule by the cell
requirements for a chemical to be called a neurotransmitter
- must be a mechanism that can retrieve the chemical from the action area (reuptake)
- the chemical must be released and cause a functional change in another cell
- the chemical must be synthesized or present in the neuron
- the same reaction should only occur when the chemical is placed directly on another cell in experiments
acetylcholine (ACh)
a small neurotransmitter that gets its components from food
- plays an important role in signalling to the muscles
neuropeptides
such as endorphins and enkephalins
soluble gases
can also be neurotransmitters, such as carbon monoxide and nitric oxide
dendro-dendritic synapses
dendrites send messages to each other
axo-somatic synapses
the presynaptic terminal synapse communicates with a cell body of another neuron
axo-dendritic synapses
the axon synapses on the postsynaptic dendrites of another neuron
axo-synaptic synapses
the presynaptic terminal of an axon synapse with a presynaptic terminal of another neuron
axo-axonal synapses
the presynaptic terminal synapse communicates with an axon of another neuron
retrograde signalling
synaptic communication is reversed
gap junction
the gap between the pre- and postsynaptic membrane is very small
- communication in a gap junction is similar to that of an action potential
- faster than that of a chemical synapse
hormones
chemical substances that are produced in specialized glands or cells
- can be lipids, peptides, or monoamines
adrenal medulla
is the “inside” and secretes amine hormones
- epinephrine and norepinephrine are produced in the medulla in response to the activation of the sympathetic nervous system
adrenal cortex
the “outside” and produces steroids, with cortisol as the most important substance
pineal gland
produces melatonin whose levels decrease and increase throughout the day
hypothalamus
synthesizes and releases corticotrophin-releasing hormone (CRH) through the paraventricular neucles (PVN)
- gonadotropin-releasing hormone is made in the anterior hypothalamus and controls the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH)
pituitary gland
closely linked with the hypothalamus
- divided into anterior and posterior
- thyrotrophin-releasing hormone comes from the PVN, stimulating the anterior pituitary, releasing thyroid-stimulating hormone
anterior pituitary
secretes the hormones FSH, LH, TSH, ACTH, prolactin (PRL) and GH (growth hormone)
posterior pituitary
secretes oxytocin and vasopressin/ADH (antidiuretic hormone)
thyroid
releases thyroid hormones
- main function is to regulate metabolism and support brain and nervous system development
hypothyroidism
caused by an inadequate amount of iodine
- leads to slowed metabolism
pancreas
an important gland in feeding and drinking because it secretes glucagon and insulin
gonads
estradiol, testosterone, and progesterone are the main steroid hormones of the ovaries and testes
monoamines
derived from a single amino acid, such as dopamine and adrenaline
peptides and proteins
multiple amino acids linked together
- majority of hormones are peptide hormones
steroids
fats made in the adrenal cortex and gonads, such as cortisol and testosterone
catecholamines
monoamines derived from tyrosine
cytokines
involved in the communication of immune cells
local growth factors
released for cell division and differentiation in the case of injuries
nitric oxide (NO)
causes local relaxation of muscles in order to dilate blood vessels and thus increase oxygen transport in case of an oxygen shortage
prostaglandins
fatty substances made up of omega-3 and omega-6 fatty acids, involved in the concentration of the uterus during childbirth and in immune reactions such as fever and inflammation
