Central Nervous System Flashcards
What are the main functions of the central nervous system (CNS)
(4)
- Sensation - changes in body and external environment
- Integration - makes sense of changes
- Response- initiates a response
(Represents the body’s most rapid means of maintaining homeostasis)
What are the two principle types of cells in the nervous system?
- Neurones - functional unit (help transmit nerve impulse)
- Neuroglia - support and protect neurones (responsible for maintaining homeostasis control)
What are the 3 characteristics of a neurone?
- The cell body (the core section of the neurone)
- Axon (long tail-like structure)
- Dendrites (fibrous roots that branch out of the cell body and communicate with adjacent neurones)
What is action potential in nerve cells? (4)
- Action potential occurs when a neurone sends information down an axon, away from the cell body
- Nerve fires when it’s depolarised and stops firing when it’s polarised
- Active = Depolarised (inside of cell is positive)
- Non active/resting = polarised (inside of the cell is negative)
What are the main characteristics of action potential in nerve cells? (3)
- Depolarisation of the cell is na dependent
- Sodium and potassium cells open, na goes in and K goes out
- Impulse needs to reach action potential to carry on, if it’s not reached the message won’t continue to be transmitted
(Resting membrane potential = -70mV)
How do drugs modulate the nerve firing in the action potential in nerve cells?
- Deter cell depolarisation by blocking an entry and blocking na and ca channels
- Render negatively charged by leaving K channels open
What is Saltatory conduction? (4)
- Saltatory conduction describes the way an electrical impulse skips from node to node down the length of an axon
- only occurs in myelinated nerves
- Dramatically increases conduction velocity
- Impulse jumps between nodes of ranvier
Speed of nerve impulses are dependent on the size and type of nerve……
Explain (2)
- Large, myelinated - A fibres = fast motor (sharp, stabbing, acute pain)
- Small, unmyelinated - C fibres = slow (achy or throbbing pain, itch, cough)
(Neuropathic pain - thermal messages)
1) What is a synapse?
2) What is the antidromic conduction?
1) A synapse is a junction between two nerve cells, which impulses pass by diffusion of a neurotransmitter
2) Antidromic conduction is conduction of nerve cells in a reversed direction/back tracks
What are neurotransmitters? (4)
- Chemicals released into the synaptic cleft
- 100 or more varieties in the brain
- Bind to post synaptic receptors
- Neurotransmitter disfunction is implicated in mental health
What are the 4 groups of neurotransmitters?
1) Biogenic (ACh, monoamines, noradrenaline)
2) Amino acids (GABA, glutamate, glycine)
3) Peptides (endorphins, enkephalins)
4) Other (nitric oxide, adenosine)
- Noradrenaline is produced in the nervous system
- Adrenaline is produced in the endocrine system
How do neurotransmitters work? (3)
- Neurotransmitters are stored in the axon terminals of the neurone in small sacks called synaptic vesicles
- Pre synaptic nerve excited by electrical signal (action potential) releases neurotransmitters into synaptic cleft
- When in the synaptic cleft the neurotransmitter interacts with the post synaptic receptors and cause a reaction to occur in the post synaptic neurone. This increases or decreases the likeliness the post synaptic neurone will become activated and fire an action potential
What are the main characteristics of the parasympathetic nervous system? (5)
- Concerned with conservation and restoration of energy
- Otherwise known as ‘cranio-sacral’ outflow
- Long pre ganglionic fibre, short post ganglionic fibre
- Neuro transmitter Acetylchlorine (ACh) acts on nicotinic and muscarinic receptors
- Responsible for cholinergic transmission
(A substance (or ligand) is cholinergic if it is capable of producing, altering or releasing ACh)
What are the main characteristics of the sympathetic nervous system? (5)
- Otherwise known as ‘thoracolumbar’ outflow
- fight or flight
- Short pre ganglionic fibre, long post ganglionic fibre
- Neurotransmitter ACh pre ganglionic and noradrenaline post ganglionic
- a and b receptors
1) Nicotinic receptors are…..
2) Muscarinic receptors are…..
1) Nicotinic (nAChR) - coupled to cation channels. Membrane depolarisation and fast excitatory transmission receptors
2) Muscarinic (mAChR) - G protein coupled receptors with 5 sub types
(M2 = cardiac and M3 = smooth muscle)
