Week 2 -The nervous system: 2.2 Chemical events at the synapse Flashcards
(32 cards)
The blood brain barrier
The purpose of the blood–brain barrier is to protect against circulating toxins or pathogens that could cause brain infections, while at the same time allowing vital nutrients to reach the brain.
https://qbi.uq.edu.au/brain/brain-anatomy/what-blood-brain-barrier
Capillary Cells in the CNS are tightly joined
Capillary Cells outside the CNS have “gaps”
What is CNS
Central Nervous System
Brain & Spinal Cord
Responsible for “higher order” functions - perception, thinking, experience, memory, learning
Integrates information for reflex actions. eg conditioning
Where is the CNS
Within the brain and down the spinal cord
What is PNS
Peripheral nervous System
Afferent nerves - nervous input from the body to the spinal cord.
Efferent or motor nerves which leave the CNS
Where is the PNS
Outside the brain and spinal cord
How the nervous system is organised and how does it send messages
See picture
nerves send messages by releasing chemicals.
PNS - Afferent nerves
- nervous input from the body to the spinal cord
PNS - Efferent or Motor nerves
- nerves which leave the CNS
PNS - Sympathetic Division
Produces a fight or flight response - arousing
Activates body during emergency situations
pupils - dilate
salivation - inhibits
lung airways - relaxes
Digestion - inhibits
Heartbeat - accelerates
PNS - Parasympathetic Division
Opposite to sympathetic - relaxing or calming Controls non emergency functions pupils - Constricts salivation - Stimulates lung airways - Constricts Digestion - Stimulates Heartbeat - Slows
The Neural Impulse
* A working Knowledge of this is necessary, be sure to elloaborate
When a neuron fires an action potential.
A change in the membrane potential that is regenerated at successive axon locations
potential
Refers to a stored up source of electrical energy
Depolarisation (again)
When the inside -relative to the outside electrical potential becomes less negative
Hyperpolarisation (again)
When the inside -relative to the outside electrical potential becomes more negative
membrane potential
Membrane potential is the difference in electric potential between the interior and the exterior of a biological cell. For the exterior of the cell, typical values of membrane potential, normally given in units of millivolts and denoted as mV, range from –40 mV to –80 mV.
Membrane potential is a potential gradient that forces ions to passively move in one direction: positive ions are attracted by the ‘negative’ side of the membrane and negative ions by the ‘positive’ one.
Maintaining the membrane potential
Diffusion (concentration of gradient)
Movement of molecules from regions of high to low concentration
note - selective permeability
Maintaining the membrane potential
Electrostatic Pressure
Molecules attract or repel each other, depending on their inherent charge. (positive or negative)
Maintaining the membrane potential
Anions
negatively charged ions (eg protein & chloride)
*be sure to know the levels of anions and cations inside & outside the neuron
Maintaining the membrane potential
Cations
positively charged ions (sodium & potassium)
*be sure to know the levels of anions and cations inside & outside the neuron
Cell membrane process
Potassium Channels are permeable, meaning..
??????
Role of potassium channels (open potassium channels mean potassium ions move out of the cell)
Cell membrane process
Sodium Channels are permeable, meaning..
??????
Role of sodium channels (open sodium channels mean sodium ions move into the cell, resulting in depolarisation)
Factors affecting speed of impulse
- Diameter of axon
- Myelinated or Nonmyelinated
- Saltatory Conduction (nodes of ranvier/gaps)
Saltatory Conduction
Saltatory conduction (from the Latin saltare, to hop or leap) is the propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials.
Skips over the myelin sheath making it faster
Saltatory Conduction
Saltatory conduction (from the Latin saltare, to hop or leap) is the propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials.
Skips over the myelin sheath making it faster
