Chapter 1 Flashcards
Santiagio Raman Cajal
- demonstrated that the nervous system is composed of separate cells.
- neuron theory.
the nervous system
the network of nerve cells and fibers.
- body’s communication system.
central nervous system
the brain and the spinal cord.
peripheral nervous system
sensory and motor fibers that connect the CNS to the rest of the body.
Neurons
receive information and transmit it to other cells.
Processes
axon and dendrites.
Dendrites
branching fibers that get narrower near their ends.
Dendritic spines
increase surface are available for synapses.
Nucleus
structure that contains the chromosomes.
Mitochondria
- powerhouse of cell
- creates more than 90% of cellular activity.
- produces ATP (main energy of cell).
overactive mitochondria vs under-active
overactive = burn fuel rapidly, overheat.
under-active = predisposed to depression.
Ribosomes
sites within a cell that synthesize new protein molecules.
What do proteins do?
- act as enzymes (catalyses chemical reactions).
- cell signalling and binding.
endoplasmic reticulum
a network of thin tubes that trans- port newly synthesized proteins to other locations.
Types of neurons
- ) motor
- ) sensory
- ) pyramidal
Motor neuron
- soma in the spinal cord.
- receives excitation through its dendrites and conducts impulses along its axon to a muscle.
Sensory neuron
- soma located in PNS.
- detects changes in the external and internal environment and sends info to CNS.
Interneurons
- located in CNS within neuronal structures.
- connect somatic and motor information.
Cell body/soma
contains the nucleus, ribosomes, and mitochondria.
Axon
conveys an impulse toward other neurons, an organ, or a muscle.
Myelin sheath
insulating material that covers axons.
afferent axons
brings information into a structure.
ex: sensory neurons
efferent axons
carries information away from a structure.
ex: motor neurons.
Interneuron
cell with dendrites and axon entirely contained within a single structure.
3 types of neurons based on structure
- ) bipolar
- ) mutlipolar
- ) pseudo-unipolar
Bipolar neurons
- usually sensory
- retinal cells
- olfactory epithelium
Multipolar neurons
- most common
- spinal cord
- pyramidal and purkinje cells
Pseudo-unipolar
- sensory neurons.
functions of cell membrane
- protects the inner cell.
- regulates molecules that enter and exit.
Cell membrane is selectively permeable to
non charges, small molecules.
what do proteins along the cell membrane do?
they transport sodium, potassium, calcium and chloride from one side of membrane to the other.
cytoplasm
- place of chemical reactions.
- moving material from one part of cell to other.
- 80% water.
Cystoskeleton
important for shape of the cell.
Nucleus
- located in soma
- control center
- contains DNA/genes/choromosoms
- directs cells activities
DNA
contains genes that each cell uses to make thousands of proteins, enabling it to survive.
mitochondrial failure causes ________
cell injury that leads to cell death.
misfolding of proteins leads to
protein aggregation and disease.
microtubules
Part of the cytoskeleton and involved in transporting
substances from place to place within the cell and
along the axon.
Axoplasmic transport
Anterograde –> soma to periphery
Retrograde –> periphery towards soma
Glia cells
- glue of the nervous system
- support neurons, modulate neuron communication, maintains homoestatis of the nervous system.
Ependymal cells
- lining of ventricles
- production of CSF
Oliodendrocytes
- myelin sheath in CNS
Micro glia
- smallest of glia
- phagocytes
- immune function
Radial glia
scaffolding during neurodevelopment and neurogenesis.
Astrocytes
- physical support to cell
- repair damage to tissue and maintains BBB
- nourishment of cells
- control chemical environment and foster neural communication
Schwann cells
- provide myelin sheath to axons in the PNS
- each myelin segment is made up of a single Schwann cell
- chemical compositon of the myelin protein
Satellite cells
- surround neurons in sensory, sympathetic and parasympathetic ganglia
- regulate extracellular space
- activated in response to tissue damage
- implicated in chronic pain
Blood brain barrier is made up of ______
endothilial cells (blood vessel cells) that form tight junctions.
Blood brain barrier - Passive diffusion
oxygen, carbon dioxide, small uncharged and lipid soluble molecules.
Chemicals that are actively transported into the brain include
glucose, amino acids, choline, iron, hormones.
Function of BBB
- ) protection
- ) homeostasis
- ) nutrition
BBB is compromised by
- hypertension
- radiation
- infection
- trauma
- inflammation
active transport
a protein-mediated process that expends energy to pump chemicals from the blood into the brain.
Glucose
nutrition for vertebrate neurons.
thiamine
- vitamin B
- body needs this to use glucose.
Prolonged thiamine deficiency
Leads to
- death of neurons
- Korsakoff’s syndrome –> marked by severe memory impairments.
Ions
- charged molecules.
- cations and anions
electrical gradient/polarization
when at rest, the difference in electrical charge between the inside and outside of the cell.
The electrical potential inside the membrane is slightly _____ with respect to the outside
negative
cations
K+, Na+, Ca+
anions
Cl-
What is the resting membrane potential of a neuron?
Voltage negative inside relative to outside; -70mV
voltage-dependent ion channel
an ion channel that opens or closes according to the value of the membrane potential.
Na+ channel _____
is closed; concentration greater outside cell than inside cell.
K+ channel _______
not entirely closed; concentration greater inside cell than outside
cell.
Diffusion
movement of molecules from regions of high concentration to region of low concentration.
sodium potassium pump
a protein complex, repeatedly transports three sodium ions out of the cell while drawing two potassium ions into it.
selective permeability
Oxygen, carbon dioxide, urea, and water cross freely through channels that are always open.
how does sodium potassium pump work?
- Pushes 3 Na+ ions out of the cell and pulls 2 K+ into cell.
- Required energy (ATP).
- Na+ is 10x more concentrated outside cell.
concentration gradient
the difference in distribution of ions across the membrane.
withdrawal reflex
sensory neurons detect stimulus.
interneuron relays info to motor neuron.
motor neuron creates behavioural response.
electrostatic pressure
opposites attract; similarity repulse.
why resting potential?
remains stable until the neuron is stimulated.
what forces act on K+?
- diffusion forces K+ out.
- electrostatic pressure forces K+ in.
- K+ leakage out of cell.
Action potential
the brief electrical signal that provides the basis for conduction of information along an axon.
Threshold of excitation
+30 mV; the value of the membrane potential that must be reached to produce an action potential.
sodium ions flow into cell.
hyperpolarization
increased negative charge inside neuron.
depolarization
resulting in less negative charge inside the cell.
subthreshold stimulation
produces a small response that quickly decays.
chemical events behind the action potential;
- At the start, sodium ions are mostly outside the neuron, and potassium ions are mostly inside.
- When the membrane is depolarized, sodium and potassium channels in the membrane open.
- At the peak of the action potential, the sodium channels close.
repolarization
an increase in the membrane potential of a cell toward resting state.
all or none law
The principle that once an action potential is triggered in an axon, it is propagated without growing or diminishing to the end of the fiber.
rate law
The principle that variations in the intensity of a stimulus or other information being transmitted in an axon are represented by variations in the rate at which that axon fires.
saltatory conduction
- conduction of action potentials by myelinated axons.
- AP appears to jump from one node of Ranvier to the next.
- faster and more efficient.
refractory period
cell resists the production of further action potentials.
absolute refractory period
the membrane cannot produce another action potential, regardless of the stimulation.
relative refractory period
a stronger- than-usual stimulus is necessary to initiate an action potential.
