Neurophysiology Flashcards
Define glycocalyx.
is a glycoprotein and glycolipid pericellular matrix that surrounds the neuron, constituting a protective barrier
How is spontaneous movement of molecules and ions across a membrane possible?
passive transport down a concentration gradient
both in regard to particulate concentration and voltage - > electrochemical
Lipid bilayer is permeable to?
small polar molecules that are not ionized,
gases O2, CO2
water molecules,
steroid hormones
Lipid bilayer is not permeable to?
ions,
hydrophilic molecules and
macromolecules
Simple diffusion happens through what or where?
lipid bilayer or protein channels
specific water channels for the rapid water movement
Aquaporins
Describe facilitated diffusion
facilitated by carrier proteins
usually when molecules are too big to diffuse through the usual channels
Name the gross division for protein channels.
leak channels and gated channels
Name the channel type that requires a signal molecule for activation.
ligand-gated channels
triggered by ligands like acetylcholine, GABA, cAMP, ATP
Name the channel type that requires a mechanical signal.
stretch-activated channels
e.g. stretch receptors in muscles, sound receptors
Name the channel type that requires a change in electric-potential to react.
voltage-gated channels
e.g. Na-/K-channels of nerve and muscle cells
The difference between primary and secondary active transport?
In primary- the energy is required directly.
In secondary- the energy is derived secondarily from energy stored in the concentration gradients of ions.
Name a primary active transporter.
Na+/K+ ATPase transporter, or „pump“
Ca 2+ pump in skeletal muscles: elimination of Ca after contraction
Name the 2 types of secondary active transport.
shared carrier proteins - counter-transport, in which the two substrates cross the membrane in opposite directions (antiport)
and cotransport, in which they cross in the same direction (symport)
Name a secondary active transporter.
sodium-glucose linked transporter, SGLT in enterocytes
What type of transport is vesicular transport?
active transport
Give 2 examples of direct intercellular communication.
gap-junctions (common in smooth- and cardiac mm.)
nanotubes
Give 6 examples of indirect intercellular communication.
Cytokines Hormones Neurohormones Neurotransmitters Paracrines Pheromones
What are paracrines?
a form of cell signaling in which a cell produces a signal to induce changes in nearby cells
What are cytokines?
regulatory peptides such as interferon, interleukin, and growth factors, which are secreted by certain cells of the immune system and have an effect on other cells.
Normal membrane resting potential?
-70- 90 mV
some sources say -50- 75 mV
Define membrane potential.
Unequal distribution of ions on the outer and inner surface of plasma membrane and the difference in electric potential caused by this
Define action potential.
the rapid and propagating change of the resting membrane potential associated with the passage of an impulse along the membrane of a muscle or nerve cell.
what, in excitatory cells, opens in response to action potential
sodium- and potassium- gated ion channels
Define depolarisation.
cell undergoes a shift in electric charge distribution, resulting in less negative charge inside the cell compared to the outside.
caused by the fast influx of sodium ions
Define repolarization.
the change in membrane potential that returns it to a negative value just after the depolarization phase of an action potential
Define refractory period.
state during which a new action potential cannot be initiated,
time when the membrane potential is not yet restored
What is absolute refractory period.
absolute- precedes relative-
in this phase, a second action potential cannot be initiated, no matter how large a stimulus is repeatedly applied.
What is relative refractory period.
relative- follows absolute-
a second action potential can be initiated, but initiation will require a greater stimulus than before
The difference between absolute and relative refractory periods?
absolute is not possible to change
refractive is possible to change conditionally
minimum threshold potential
typically -50 to -55 mV
the basis for local anaesthesia, treatment of
high blood pressure etc. lies in what concept?
blocking voltage-gated channels
Define saltatory propagation.
is the propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity
Difference between electrical and chemical synapses?
in a chemical syn-, the nerve impulse passes chemically by means of neurotransmitters whereas an electrical synapse is connected through channel proteins.
example of where electrical synapses are used
heart muscle, smooth muscle
example of where chemical synapses are used
nerve cells
In peripheral neurons, which neurotransmitters dominate
acethylcholine and norepinephrine
define Agonist
a compound that binds to the receptor and activates it similarly to the corresponding neurotransmitter
e.g. opium, morphine, heroin are agonists to enkephalins and endorphins
define antagonist
a compound that binds to the receptor but does not activate it, these molecules prevent the receptors from
binding agonists and thus block their action
Define neuropeptide.
any of a group of compounds which act as neurotransmitters and are short-chain polypeptides.
neuropeptides act more slowly and for longer than neurotransmitters of non-peptide species
What is the depolarization phase of action potential caused by?
Fast influx of Na+ ions
Name the three meninges from outside in
dura mater, arachnoid mater, pia mater
Cerebrospinal fluid between which meninges
arachnoid and pia mater
What is the function of the choroid plexuses?
the main function of which is to produce cerebrospinal fluid
The capillaries are highly selective and permeable to
limited compounds – blood brain barrier
What is a choroid plexus
richly vascularized secretory pia mater tissue
CSF composition?
is cell and protein free,
low content of glucose and
amino acids,
lower K+ concentration than in blood plasma
Which part of the brain is not bound by the blood-brain-barrier?
Hypothalamus because of it’s regulatory function of homeostasis
define neuroglia
also called glial cells
a diverse class of cells that provide developmental, physiological, and metabolic support for neurons.
peripheral nervous system neuroglia
two kinds of neuroglia: schwann cells and satellite cells.
Neuroglia in the CNS
astrocytes,
ependymal cells
microglial cells
oligodendrocytes
What are microglia and their function?
glial cells of CNS
are the brain’s immune cells
play a role in the developing brain.
What are Astrocytes and their function?
glial cells of CNS
control the levels of neurotransmitter around synapses, control the concentrations of important ions
provide metabolic support
modulate how neurons communicate.
What are oligodendrocytes and their function?
glial cells of CNS
produce myelin
What are ependymal cells and their function?
glial cells of CNS
line the spinal cord and ventricles of the brain.
They are involved in creating cerebrospinal fluid
What are Schwann cells and their function?
glial cells of PNS
myelinate neurons in the peripheral nervous system.
What are Satellite cells and their function?
glial cells of PNS
surround neurons in the sensory, sympathetic
and parasympathetic ganglia
and help regulate the chemical environment.
define ganglion/ganglia
are ovoid structures containing cell bodies of neurons and glial cells supported by connective tissue in the peripheral nervous system.
Ganglia function like relay stations - one nerve enters and an other exits.
What are Motor nerves
also known as efferent nerves
send impulses from the brain and spinal cord to all of the
muscles.
What are Sensory nerves
also known as afferent nerves
Send impulses from muscles, skin and other areas of the body to the spinal cord and brain.
What are autonomic nerves
also known as a type of efferent nerve
control involuntary or semi-voluntary functions
damage can cause dysfunction of different body organs
Nerve fiber gross classification?
A, B and C groups
A-nerve fibers divided into what further subgroups?
- A-alpha fibers
- A-beta fibers
- A-delta fibers
- A-gamma fibers
Describe fibers of a-group.
have a large diameter, high conduction velocity, and are myelinated.
Describe • A-alpha fibers
are the primary receptors of the muscle spindle and golgi
tendon organ.
Describe • A-beta fibers
act as secondary receptors of the muscle spindle and
contribute to cutaneous mechanoreceptors.
Describe • A-delta fibers
are free nerve endings that conduct painful stimuli related to pressure and temperature.
Describe • A-gamma fibers
are typically motor neurons that control the intrinsic
activation of the muscle spindle.
Describe Fibers of the B group
are myelinated with a small diameter and have a low conduction velocity.
The role of B fibers is to transmit autonomic information.
Describe Fibers of the C group
are unmyelinated, have a small diameter, and low conduction velocity.
C fibers often respond to combinations of thermal, mechanical, and chemical stimuli.
what is cauda equina
a thick bundle of long nerve roots in lumbar and sacral regions
Grey matter of the spinal cord consists of?
neuron bodies,
dendrites and glial cells,
dorsal ventral and lateral horns in each half
White matter of the spinal cord consists of?
consists of bundles of myelinated nerve fibers located peripherially
A nerve is what exactly
a bundle of peripheral neuronal axons.
Bundles of nerves are called tracts.
How many cervical nerves
Cervical nerves -8 pairs
How many thoracic nerves
Thoracic nerves – 13-18 pairs
How many lumbar nerves
Lumbar nerves – 5-7 pairs
How many sacral nerves
Sacral nerves – 3-5 pairs
How many coccygeal nerves
Coccygeal nerves - 4-9 pairs (1 in human)
Cerebral motor cortex gives rise to what three descending motor tracts:
the corticonuclear,
corticopontine, and
corticospinal.
The corticonuclear tract descends to its target nuclei in the brainstem, mediating what type of actions?
voluntary actions as eye movements,
mastication, facial expression, swallowing, neck movement, and tongue movement.
The corticopontine tract terminates in the
pons and synapses with neurons that send their axons to the contralateral cerebellum.
Two types of reflex arcs:
autonomic reflex arc (affecting inner organs) and
somatic reflex arc (affecting muscles)
what is the Golgi tendon organ
is a proprioceptive sensory receptor organ that is located at the insertion of skeletal muscle fibers onto the tendons of skeletal muscle. It provides the sensory component of the Golgi tendon reflex.
what are muscle spindles
are stretch receptors within the body of a skeletal muscle that primarily detect changes in the length of the muscle.
proprioception
give 3 examples of polysynaptic reflexes
scratching reflex
postural
withdrawal
when is the Sympathetic nervous system active
during stress and physical activity
when is the Parasympathetic active
active during rest
Feedback control principle
the variable being controlled is measured and compared with a reference
which nervous system is always in tonus.
ANS
where are the Sympathetic NS centers
in thoracic and lumbar regions
The first neuron body in CNS and the second – in
sympathetic trunk or three ganglia.
where are the Parasympathetic NS centers
in midbrain, medulla and
sacral region of spinal cord.
The second neuron is located in the ganglion near the
effector.
in which NS
Preganglionic fibers are short and postganglionic fibers are long
Sympathetic NS
in which NS
Preganglionic fibers are long and postganglionic fibers are short
Parasympathetic NS
sympathetic NS Neurotransmitter of preganglionic axons is
acetylcholine
(cholinergic axons, nicotinic or muscarinic cholinergic
receptors)
sympathetic NS Postganglionic axons release
norepinephrine (binding to α- or β- adrenergic receptors)
Parasympathetic nervous system both fiber types release?
acetylcholine
What are nicotinic receptors?
are receptor polypeptides that respond to acetylcholine.
What are muscarinic receptors?
are acetylcholine receptors that form G protein-coupled receptor complexes in the cell membranes of certain neurons and other cells.
Five subtypes
Where can nicotinic receptors be found?
On postganglionic cell bodies in all autonomic
ganglia
Where can muscarinic receptors be found?
On effector cells of parasympathetic system
Receptor types in sympathetic system
Adrenergic receptors
α1 receptors
α2 receptors
β1 receptors
β2 receptors
On what type of cells are adrenergic receptors found
On effector cells of sympathetic system
bind to what and what type of response - α1 receptors
bind to norepinephrine, excitatory response
bind to what and what type of response - α2
receptors
bind to norepinephrine, inhibitory response
bind to what and what type of response • β1
receptors
bind equally to epinephrine and to
norepinephrine, excitatory response
bind to what and what type of response • β2 receptors
bind to epinephrine, inhibitory response
What do Muscarine and nicotine have in common
agonists of ACh receptors
what type of receptor found primarily in heart
β1 –adrenergic receptors found primarily in the heart
where are the Regulatory centers of the autonomic nervous system
in hypothalamus and medulla oblongata
