Lecture 2 Flashcards
Resting membrane potential
Difference in charge across a cell membrane inside and outside the cell at rest.
(Leakage channels are constantly diffusing ions creating homeostatic balance)
Aspects effecting membrane potential
- Fixed ions
- Cellular proteins
- Phosphate groups
- Other organic compounds
Intercellular space is K+ abundant and gives resting membrane potential.
Graded potentials
Small changes in membrane potential below the action potential threshold.
Types of graded potentials
Leakage - constantly open and passive
Ligand - gated- open via chemical stimulation (ex. Hormone or Neuro T binds)
Voltage gated Channels
Once voltage threshold is reached, voltage gated channels open.
Two main types:
Sodium
Potassium
Action Potential Stages
- Resting stage
- Depolarization
- Repolarization
- Hyperpolarization
Sodium floods into the cell depolarizing until the peak which then closes the sodium voltage gates. More slowly potassium floods out of the cell to repolarize until re-reaching the membrane potential at which point the potassium voltage gated channels close and remain at resting potential.
Physiological application of Action potentials
- Nerve traffic
- Muscle contraction
- Hormone release
- G.I. Secretions
- Cognition
- Senses
- Input zone - incoming signals come in
- Trigger zone- (hillock) Action Potentials are initiated
- Conducting zone- area that sends the actions potential information
- Output zone- (terminal) releases neuro T that influences other cells .
Factors that effect Action Potentials
- Strength of stimulus
- Distance synapse is traveling
*APs are essential for our senses
Golgi Type 1
Neurons with long axons that begin in the grey matter in the CNS, and extends to remote peripheral organs. (Projection neurons- can also be found in motor cells of the spinal cord)
Golgi Type II
Have shorter axons and are primarily in the CNS in the cerebral and cerebellar cortexes.
Electrical synapses
Bidirectional signals sent via gap junctions.
Neurochemical synapses
Begin as an electrical impulse, releases chemical substance ( neuro T) and then re-becomes an electoral impulse.
Neurotransmission stages
- Neuro T is synthesized and packaged
- Action potential arrives at presynaptic terminal
- As depolarization happens Ca2+ channels open
- Ca2+ influx tiggers transmitter vesicles to fuse with the presynaptic membrane
- Neuro T molecules diffuse across the synaptic cleft and bind to their accompanying receptors on the post synaptic cell.
Ionotropic receptors
Transmembrane group of ion channels that open or close in response to a ligand (chemical messenger like a Nero T - acetylcholine)
Metabotropic receptors
Membrane receptors that use signal transduction mechanisms (G proteins) activate intracellular events like second messenger chemicals.
(Post synaptic responses- which introduces more Ca2+ into the system).
ex. Glutamate receptors, GABA b receptors, serotonin receptors).
EPSPs mechanism
Typically influx of Na+
IPSP mechanism
Typically influx of Cl-
Excitatory Amino Acid Neurotransmitters
- Glutamate
- Aspartate
Inhibatory Amino Acid Neurotransmitters
- GABA
- Glycine
** serotonin can be both inhibatory and excitatory
Amine Neurotransmitters
- Dopamine
- Acetylcholine
- Norepinephrine
- Epinephrine
- Histamine
Peptide Neurotransmitters
- Substance P
- Enkephalin
- Dynorphin
Actions after synaptic response is complete
- Enzymatic degradation
- Diffusion away from post synaptic receptors
- Reuptake into presynaptic nerve terminal
- Desensitization of postsynaptic receptor to ligand.
Neuromuscular Junction Ionotropic Channel (neuro t and receptor)
Acetylcholine is the Neuro T —-
Nicotinic is the receptor
