2 - Communication Systems and Control Flashcards
Nervous System Functions (introduction)
Gathers information from outside and inside (sensory function)
Transmits information to processing area of brain and spinal cord
Process information to determine response (intergrative function)
Sends information to effectors so they can respond (motor function)
Central Nervous System (CNS)
Brain and spinal cord
Autonomic Nervous System (ANS)
Controls involuntary functions
Sensory-Somatic Nervous System (SNS)
Controls voluntary movements
General structure of a Neurone (image on OneNote)
Dendrites – receive incoming signals from other neurones
Cell body (Soma) – contains the nucleus and organelles, integrating signals
Axon – transmits electrical impulses to the next neurone or target cell
Myelin sheath – insulates the axon, speeding up signal transmission
Axon terminals – release neurotransmitters to communicate with other neurones
Functional Classification of Neurones
Sensory (afferent) neurones
Interneurones
Motor (Efferent) neurones
Sensory (afferent) neurones
carry signals from sensory receptors to the CNS
Interneurones
process information within the CNS
Motor (efferent) neurones
carry signals from the CNS to muscles and glands
Resting membrane potential
- The electrical charge difference across a neurone’s membrane at rest (-70mV)
What’s the equilibrium potential for K+
-90mV
Ion distribution across neural membrane
K+ is higher inside the cell
Na+ is higher outside the cell
Maintenance of Resting Potential
- Selective permeability – K+ leaks out more than Na+ leaks in
- Sodium-potassium pump (Na+/K+ ATPase) – Pumps 3 Na+ out and 2 K+ in using ATP
- Negatively charged proteins – Inside the cell, contribute to a negative charge
Equation Used to Calculate Resting Potential (2)
Nernst Equation – Calculates equilibrium potential for individual ions
Goldman Equation – Considers all permeable ions to calculate resting potential
Action potential definition
A rapid electrical change in the membrane potential when a neurone is stimulated
Action potential - types of channels (3)
Chemically gated channels (receptor mediated)
Voltage gated channels
Leak channels (passive)
Action potential (Na+ voltage gated channels)
At rest Na+ voltage gated channels
If there’s a voltage change that reaches threshold, the voltage gated Na+ channel will open and Na+ flows in
Then it locks
Phases of action potential
- Resting state (-70mV) – Na+/K+ pump maintains ion distribution
- Depolarisation (+30mV) – voltage-gated Na+ channels open, Na+ enters
- Depolarisation – Na+ channels close, K+ channels open, K+ exits
- Hyperpolarization – K+ channels remain open briefly, making the membrane more negative
- Return to resting Potential – Na+/K+ pump restores original ion balance
What are the 2 refractory periods
Absolute
Relative
All or nothing principle
If the threshold is reached, an action potential always occurs
Weak stimulus can cause small local depolarisation of membrane, but no action potential
What’s conduction velocity (whats it dependant on)
Speed of action potential
Axon thickness (thicker - AP travels faster)
Temperature
Myelination
Electrical Synapse
Direct contact between cells
Ion flow through gap junctions (fast but rare)
CNS and PNS
Chemical Synapses
cells aren’t directly coupled
Use neurotransmitters to transmit signals across a synaptic cleft
M
Most abundant
Steps of Chemical Synaptic Transmission
- Action Potential Arrives at the axon terminal
- Voltage-Gated Ca²⁺ Channels Open, allowing Ca²⁺ influx
- Neurotransmitter Release – Synaptic vesicles release neurotransmitters into the synaptic cleft
- Binding to Postsynaptic Receptors – Excitatory (depolarisation) or Inhibitory (Hyperpolarisation)
- Signal Transmission Continues or is terminated by neurotransmitter breakdown or re-uptake
