Since hormones are a form of lipid, how are hormones transported in the blood?
Dissolved (hydrophilic messengers) and Bound to carrier proteins (hydrophobic messengers)
What are the properties of receptors?
~show specificity for the messenger
~Receptor-messenger binding is brief and reversible
~A single messenger binds to more than one receptor, but different receptors have different affinities for a single messenger
~Cells have more than one receptor type
The magnitude of a target cell response depends upon what 3 things:
Number of receptors on target cell
Affinity of receptor for messenger
What is a receptor agonist? What is a receptor antagonist?
Agonist--compounds that bind to receptor and cause normal biological response
Antagonist--compounds that bind to receptor and produce no response (blockers)
What is the difference between exogenous versus endogenous?
Endogenous--produced in the body and secreted in the body
Exogenous--administered to the body externally; ex: pill or injection
What messengers are hydrophobic/lipophilic and bind to receptors inside the cell?
Steroid hormones--binds to receptors in cytoplasm
Thyroid hormones--bind to receptors in nucleus
What messengers are hydrophilic/lipophobic and bind to receptors located on the plasma membrane?
Amines (except thyroid hormones)
Steroid hormones bind to _______ receptors and thyroid hormones bind to ________ receptors
Steroid binds to cytoplasmic receptors
thyroid hormones bind to nuclear receptors
What is a channel-linked receptor and what are it's two types?
~ A ligand binds to a receptor which opens an ion channel
~Fast ligand-gated channels and Slow ligand gated channels
What is the difference between Fast-ligand gated channels vs Slow ligand-gated channels?
Fast--receptor and channel are the same protein (nicotine receptor)
Slow--receptor channel are separate proteins coupled by a G protein (Muscarinic receptor)
describe an enzyme linked receptor mechanism (tyrosine kinase)
messenger binds to receptor- changing conformation
conformation change activates tyrosine
tyrosine kinase phosphorolates a protein
the phosphorolated protein brings about a change within the cell
Calmodulin has what affects within the cell
G Protein Linked enzymes are:
adenylate cyclases- cAMP and protein kinase A
Phospholipase C- IP3 Ca++ = calmodulin; DAG, protein kinase C
Define Signal amplification
Signal amplification is one messenger binding to a cell and producing a greater magnitude of phosphorolated proteins
What 2 systems are capable of long distance communication
nervous and endocrine
Nervous system communicates over long distances by:
transmitting electrical signals along the length of an axon; followed by a chemical signal across the synapse
Endocrine system communicates over long distances by:
releasing chemical messengers into the blood; messengers are then transported throughout the body
Primary endocrine organs include:
Secondary endocrine organs include:
The hypothalamus and pituitary gland, together, regulate virtually every body system; true or false
Do hypothalamic hormones act on the pituitary or do pituitary hormones act on the hypothalamus
most hypothalamic hormones act on the pituitary
The two distinct sections of the pituitary gland are?
anterior lobe- adenohypophysis
posterior lobe- neurohypophysis
Describe the relationship between the hypothalamus and the posterior pituitary
oxytocin and ADH are synthesized and released from the hypothalamus via secretory vesicles and transported to neural endings in the posterior pituitary
describe the relationship between the hypothalamus and the anterior pituitary
hormones are secreted from the neurosecretory cells in the hypothalamus into the hypothalamic-pituitary portal system. hormones stimulate anterior pituitary to secrete hormones
What factors control blood hormone levels?
carrier protein binding
The 4 types of hormone interactions (2 hormones interacting) are
antagonistic- opposing effects
additive- 2 hormones having the same affect; sum is equal to net
synergistic- 2 hormones have the same affect; and the net is greater than the sum
permissive- one hormone is needed for another hormone to exert it's action
Neurons are classified by:
Structural classifications of neurons are, and defined as:
bipolar- (very few, primarily located in the retina of the eye, functionally sensory motor
pseudounipolar- associated with axon dendrites converge on the axon
multipolar- generally see that they have multiple dendrites associated with the cell body
Functional classifications of neurons are, and defined as:
The 5 types of glial cells are?
The function of oligodendrocytes is to:
to form myelin sheaths on CNS axons
The function of schwann cells is to:
form myelin sheaths on PNS axon
The function of astrocytes is to:
contain processes covering capillaries in brain contributing to the blood-brain barrier
The function of microglia is to
phaocytic ameoboid cells within the CNS
the function of ependyma is to:
form epithelial lining form CNS structures
Common structures within the nervous system include:
nerve fiber: long process that conducts action potential; axon
Nerve: cable like collection of nerve fibers
Nucleus: collection of cell bodies in CNS
Ganglion: collection of cell bodies outside CNS
Tract: collection of nerve fibers connecting CNS regions
What is the nervous system's secretary cell?
What is the nervous system's target cell?
What is the nervous system's mode messenger
What is the nervous system's pathway for communication
across the synapse
What is the nervous system's time to onset of effect
What is the nervous system's duration of effect
What is the Endocrine system's secretory cell
What is the Endocrine system's target cell
most cells in the body
What is the Endocrine system's messenger
What is the Endocrine system's pathway for communication
What is the Endocrine system's time to onset of effect
What is the Endocrine system's duration of effect
Define potential difference, Em
electrical charge difference between two points (measured in voltage)
Define membrane potential, Vm
potential difference across a cell membrane (inside relative to outside)
Define equilibrium potential, Ex
the membrane potential that produces an electrical force that is equal in magnitude and opposed direction to the chemical force (concentration gradient) or a given ion across the membrane, net ion movement across the membrane is zero
define resting membrane potential, Resting Vm
the membrane potential of a cell when the cell is not being stiumlated
define graded potetial
a relatively small change in Vm produced by a stimulus that opens ligand gated ion channels; strength of graded potential is related to the strength of the stimulus
Define action potential
a large change in Vm produced by the opening of voltage-gated channels as a result of a graded potential that depolarizes the membrane to threshold
Ion flow across a cell membrane occurs via what three things?
flow through leak channels (non-gated)
flow through open gated ion channels
If the permeability of a membrane to an ion increases, then the net electrochemical force on that ion will move it across the membrane in the direction that will move the membrane potential towards that ion's equilibrium potential
If Ex < Vm, what direction will an ion flow
if Ex > Vm, what direct will an ion flow
The action of Na/K pumps determine the equilibrium potentials for NA+ and K+..... why?
What is the resting membrane potential of a neuron?
What is the threshold potential required after a graded potential to stimulate an action potential
What is the equilibrium potential of sodium?
What is the equilibrium potential of potassium?
What determines the permeability of a membrane to an ion?
the number of ion channels open
In a resting state is there are a greater number of Na+ current or K+ current across a neuron membrane? explain your answer?
What types of stimuli will affect neurons
Graded potentials are...?
small, localized changes in membrane potential that result from a stimulus opening ligand gated ion channels
Define Summation of graded potentials?
A single stimulus resulting in small graded potential that dies out in a short time
Summation of graded potentials can be two types; what are they?
Define temporal summation
multiple stimuli from the same source delivered over short time period
Define spatial summation
stimuli delivered from multiple sources
Action potential is defined as?
a sequence of rapidly occurring events that increase and eventually reverse the membrane potential (depolarization) and then restore it to the resting state (depolarization)
When a neuron depolarizes, what is happening
Na+ moves inward through voltage gated ion channels
Voltage gated Na+ channels consist of two types of gates
activation gates- open Na+ channels during depolarization
Inactivation gates- closed Na+ channels during depolarization
when a neuron repolarizes, what is happening?
Outward movement of potassium through voltage gated channels; the movement through these channels have a single gate that opens more slowly than Na+ channels during depolarization
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