BISC 101 Lecture Notes - Lecture 8: Cell Membrane, Neuroplasticity, Autoimmune Disease

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Terms:
Afferent: Transmit sensory info to CNS
Internal (sensors that monitor) and external (receptors for pressure, light,
smell)
Efferent: Carries commands from CNS to body (splits into somatic/autonomic)
Somatic: Controls voluntary movement (efferent) responds to external stimuli
Autonomic: Internal processes (digestion/heart rate) glands/organs
Parasympathetic: “Rest/digest” functions that conserve/restore energy
Constrict pupils/airways
Energy and blood flow to digestive system
Sympathetic: Fight or flight situations
Dilate pupils/relax airways/inhibition of stomach activity/release glucose
Energy and blood flow to skeletal and cardiac muscle
Central Nervous System: Information processing/Integration of electrical signals from
sensory receptors/Coordination of muscle activity
Brain and Spinal Cord
Not all nerve response involve brain
Four Structures of Human Brain:
Cerebrum: Conscious thought/memory (left/right hem.) (Controls voluntary actions
(memory, language, speech)
Cerebellum: Complex motor patterns
Diencephalon: Relays sensory info to cerebellum/control homeostasis
(Hypothalamus/thalamus) Endocrine function
Brain Stem: Connects brain to spinal cord and automatic centre for
heart/lungs/digestive system (relays info between regions of brain, spinal cord, rest of
body) Connecting point for most major nerves
Sensory processing/communication/info storage/homeostasis
Spinal Cord: Conductor of information between the PNS and the brain
Most nerves in PNS are here
Reflex Arc: SImple coordination of afferent/efferent neurons
Nerve Cell: Long strands of nervous tissue that contains thousands of neurons (Conduct
info by transmitting electrical signals) and carry info to and from brain/spinal cord
Release neurotransmitters
Sensory Neurons: Sensory receptors in skin/eyes/etc transmit data to sensory cells
inside the body to maintain homeostasis (blood ph/oxygen levels)
Interneurons: Make connections (Integration) between motor/sensory neurons
Motor Neurons: Send signals to effector cells in glands/muscles
PNS to CNS (brain/spinal cord)
From dendrites to axon terminals in the form a positive electrical current
Neuron Parts:
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Cell Body: Contains nucleus (incoming signals are integrated/out-going signal to
axon)
Dendrites: Collects electrical signals
Axon: Passes electrical signals to dendrites of another cell or efferent
Membrane Potential:
Membrane impermeable to charged ions
Membranes creates a barrier between two different environments
(extracellular and intracellular)
Membrane potential is a result of differences in extracellular and
intracellular ionic environment
Membrane potential is measured as the relative difference between these
two environments
Electrical Potential/Voltage (Volt (V)): Difference of electrical charge between two
points
Measured in millivolt (mV)
If membrane removed: Ions would from area of like charge to unlike
charge causing flow of charge (electrical current)
Includes energy stored as concentr. gradient of charged ions on two
sides of membrane (ELECTROCHEMICAL GRADIENT)
Resting Potential: Neuron not transmitting electrical signal and is sitting in extracellular fluid
at rest (Energy stored as concentration/electrical gradients in ions)
State of dynamic equilibrium in which the diffusion of potassium out of the cell via
the leak channels is balanced with the action of the sodium-potassium pump
Sodium/Potassium Pumps
K+ is actively pumped against its concentration gradient and diffuses
against its electrical gradient
Sodium loaded: Three Na+ enter the protein from within the cell
Sodium released: ATP phosphorylates the pump and changes
shape/releases 3 Na+ to outside of cell
Potassium loaded: 2 K+ enter protein from outside of cell
Potassium released: Phosphate group from ATP (gives energy) drops off
pump. Protein changes shape and released 2 K+ into the cell
Result:
Each ion is pumped against its own concentration gradient
Two positively charged particles are entering the cell for each
three positively charged particles that exit (more negative inside)
K+ Leak Channels
Potassium diffuses down its concentration gradient out of the cell via a protein
channel
Na+ Leak Channels (there but doesn’t really matter)
Reason Behind this:
Interior side of membrane has low concentration of Na+/Cl- AND large
concentration of K+/organic anions (amino acids) that drop a proton and carry
negative charge
Membrane selectively permeable to K+ along it’s concentr. gradient
(inside of membrane is negatively charged relative to outside)
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