Topic 3 Bio - Content Flashcards
What’s the Central Nervous System (CNS)?
Brain & Spinal Cord
What’s the Brain, Spinal Cord & Neurons?
Brain:
- Processes incoming info from all senses
Spinal Cord:
- Connects brain to rest of the body
- Allows messages to be passed, body->brain brain->body
Neurons:
- Cells within CNS
- Communicate with lots of other cells in huge networks
Describe & Explain the structure of the Neuron
Cell Body:
- Contains Nucleus: contains genetic material & mitochondria -> provides energy
Dendrite:
- Receives chemical message from another neuron, which triggers an electrical impulse (action potential)
Axon Hillock:
- Where the nerve impulse is triggered from
Axon:
- Electrical impulse travels through the axon (from the cell body to the axon terminal)
Myelin Sheath:
- Fatty insulating layer -> speeds up rate of transmission
Node of Ranvier:
- Gaps between Myelin Sheath
Axon Terminals:
- End of axon - Sends the electrical impulse from the cell body to parts of the body
Terminal Buttons:
- Electrical impulse converts to chemical message; Neurotransmitter -> are released & stored
What’s Action Potential?
- Process where electrical impulse passes down the axon to stimulate the release of neurotransmitters
- Tiny electrical impulse that is triggered by a change in the electrical potential of the neuron
Resting Membrane Potential:
- Slight negative charge
When a neuron receives a message - can either stimulate:
- excitatory postsynaptic potential: depolarise neuron -> reducing charge (less negative charge)
- Inhibitory postsynaptic potential: hyperpolarise neuron -> increasing charge (more negative charge)
When it has received more excitatory than inhibitory -> action potential triggered (sends impulse along axon of neuron)
FULL PROCESS:
- When the neuron is at rest, the inside is negatively charged
- When the neuron is stimulated, positively charged particles enter. The action potential is initiated - neuron is depolarised.
- After a brief period - some positive particles are pushed out of the neuron - thus the neuron moves back to its polarised state
- Neuron has finally returned to its initial polarised resting state
What is Synaptic Transmission?
- When electrical message reaches the terminal button -> turns to a chemical message
- Neurons can then pass its message to other neurons across the synaptic gap (space between 2 neurons)
PROCESS:
- Action potential reaches axon terminal
- Calcium channels open
- Calcium ions flood the terminal buttons
- Vesicles contain neurotransmitters which are released & travel to the outer membrane of the terminal button
- Casing of the vesicle fuses with the outer membrane
- Neurotransmitters (which are released from the vesicles) travel to the synaptic gap
- Receptors on postsynaptic neuron are designed to bind to a specific neurotransmitter - once detected, it will be absorbed
- Unabsorbed molecules left in the synaptic gap will be destroyed by enzymes or absorbed again by the presynaptic neuron (reuptake)
What are the examples of neurotransmitters & what do they mean or do?
Dopamine:
- Related to emotion & cognitive function
- Posture + control of movement
- Reinforcement in learning
- Dependency (e.g. addiction)
- Hormonal regulation
Serotonin:
- Mood control (esp in limbic system)
- Pain
- Sleep
- Hunger
- Regulating body temperature
Acetylcholine:
- Stimulates muscle contractions
- Necessary for memory + other cognitive functions
- Involved in expression of some emotions (e.g. anger & sexuality)
Noradrenaline:
- Associated with emotion, esp in mood control
- Sleeping
- Dreaming
- Learning
What are Recreational Drugs?
- Chemicals taken by personal enjoyment
- Alter brain functions changing mood, perception or conscious experience
What’s a Reward Pathway?
- group of brain structures
- When activated -> gives a pleasant & rewarding feeling
- Feeling encourages to repeat behaviour
Why are some drugs called ‘psychoactive’?
affect mental processes, e.g. perception, consciousness, cognition or mood and emotions
- Not always used as recreational drugs
(medical cannabis & marijuana)
What is the Dopamine system & why is it important when trying to understand recreational drugs?
- Pathway in the brain, operates on the neurotransmitter dopamine, release of which leads to feelings of reward
- All recreational drugs increase dopamine release
- Stimulate the ventral tegmental area (VTA) & nucleus membrane: nucleus accumbens creates a sense of pleasure when activated, produces more dopamine
How does heroin (recreational drug) effect the dopamine system?
- Heroin increases amount of dopamine in reward pathways of the brain (the nucleus accumbens & VTA) by boosting the activation of dopaminergic synapses -> pleasurable experience/euphoria
- Heroin is an opioid -> depressant effect on CNS -> slows down CNS activity
- When heroin for injected, morphine binds with a specific receptor at the synapse found in cerebral cortex, lambic system & hypothalamus
- Endorphins & enkephalins are produced by the body as natural painkillers; Heroin taps into this system by binding with the receptors of the natural opioid system -> enhance the natural response
- Is an agonist drug as it mimics the action of another natural biochemical
- Repeated use of heroin -> opioid receptors on postsynaptic neutrons are constantly with morphine molecules -> desensitises them to the effect of the drug
What is brains natural response to a sudden increase in dopamine & what is the consequence of the sudden increase in dopamine from the brain?
- Brain reacts to sudden increase of dopamine & reduces natural production so when the drugs wear off they have less dopamine than normal (unpleasant experience/dysphoria)
- Motivates ppl to take more of the drug to feel euphoria (dopamine)
What do we mean by withdrawal?
- ## Symptoms a person experiences when not using a substance, due to the body reacting to no longer having the substance.
What is meant by tolerance?
- When the user takes greater doses of the drug to get the same effect as on the previous occasions when they took it because the brain adapts to high lvls of dopamine caused by the drug & down-regulates it’s own natural production
What are the mode of action of recreational drugs?
- Nicotine
- Cocaine
How does Nicotine work? (what is its mode of action)
- Targets parts of the dopamine pathway & increases the amount & transmission of dopamine
- Mimics Acetylcholine
- Binds to the Nicotinic receptors