Biopsychology Flashcards
The nervous system
- Network of specialised cells in the body
- Consists of the central nervous system and the peripheral nervous system.
- It is our main internal communication system whose main functions are to collect, process and respond to information in the environment and to co-ordinate the workings of the organs and cells within the body.
Central nervous system (CNS)
consists of the brain and the spinal cord
The brain
- Centre of all conscious awareness
- Involved in all psychological processes
The spinal cord
- Transfers messages to and from the brain and body
- Responsible for simple reflex actions
The peripheral nervous system
- Responsible for relaying messages to and from the CNS and rest of the body via neurones (nerve cells)
Somatic nervous system
- Facilitates communication between the central nervous system and the outside world.
- It is made up of sensory receptors that carry information to the spinal cord and brain, and motor pathways that allow the brain to control movement.
- Controls voluntary muscle movements and some involuntary, eg reflex arc.
Automatic nervous system
- Maintains internal bodily processes like body temperature, heart rate and blood pressure.
- Works largely unconsciously and involuntarily.
- Subdivided into the parasympathetic nervous system and the sympathetic nervous system.
Sympathetic nervous system
- Prepares the body for ‘fight or flight’ response.
- Impulses travel from the sympathetic nervous system to organs in the body to help us prepare for action, e.g. quickens heart rate, inhibits less important processes like digestion and need to urinate.
Parasympathetic nervous system
- Its role is to relax the body and return it to its normal resting state.
- It slows down our heart rate and breathing rate and reduces blood pressure.
- It also restarts any functions (e.g. digestion) that were inhibited during the fight-or- flight response.
Neurons
Nerve cells that process and transmit information (messages) throughout the human nervous system through electrical and chemical signals.
Fill in the gaps:
Neurons can ____ in size but they all _____ the ____ structure.
Neurons can vary in size but they all share the same structure.
Dendrites
Branch-like structures that extend from the cell body that receives and carry signals from neighbouring neurons or sensory receptor cells towards the cell body
Axon
Carries an electrical signal (called an action potential) away from the cell body, along the axon, to the terminal buttons.
Myelin sheath
Covering that insulates and protects the axon and speeds up the transmission of the electrical signal along the axon.
Terminal button
Communicates with the next neurone in the chain across a gap called the synapse (or synaptic cleft), through a process of synaptic (chemical) transmission.
Cell body
Control centre of the neuron
Nucleus
Contains genetic material
What are the three types of neurons?
Sensory
Relay
Motor
Function of a sensory neuron
Carry messages from sensory receptors in the peripheral nervous system (found in skin, tongue etc) to the central nervous system.
Why do some neurons stop at the spinal cord?
To allow quick reflex actions
Structure of a sensory neuron
Long dendrites and short axons
Function of a relay neuron
- Connect sensory neurons to motor neurons and other relay neurons.
- Involved in the analysis of sensations.
Where are relay neurons found?
In the brain and spinal cord
Structure of a relay neuron
Short dendrites and short axons
Function of a motor neuron
Connect the central nervous system to effectors such as muscles and glands. Therefore, they allow the CNS to control movement.
Structure of a motor neuron
Short dendrites and long axons
Nodes of ranvier
Gaps that divide up (segments) the myelin sheath. These speed up the transmission of the impulse by forcing it to ‘jump’ across the gaps along the axon.
Why does the myelin sheath have gaps (nodes of ranvier)?
If the myelin sheath was continuous this would have the reverse effect and slow down the electrical impulse.
How do neurons transmit signals?
Through electric transmission and synaptic (chemical) transmission
Where does electrical transmission occur?
Within a neuron
Process of electrical transmission
At rest, a neuron is negatively charged inside the cell body (-70V) i.e., the inside of the cell is negatively charged compared to the outside of the cell. When a neuron receives a signal from a neighbouring neuron, the inside of the cell body becomes momentarily positively charged (becomes depolarised) causing an action potential (which is an electrical signal) to travel down the axon.
Where does synaptic (chemical) transmission occur?
Between neurons
Synaptic (chemical) transmission
The process by which neighbouring neurons communicate with each other by sending chemical messages across the gap (the synapse) that separates them.
Process of synaptic transmission
When the action potential (electrical signal) reaches the axon terminal at the end of the neuron, it triggers the release of neurotransmitters from tiny sacs called synaptic vesicles. Once the neurotransmitter crosses the gap, it is taken up by a postsynaptic receptor on the postsynaptic neuron and here the chemical signal is converted back into an electrical signal in the postsynaptic neuron and the process of transmission begins again in this other neuron.
Neurotransmitters
Brain chemicals that are released from the synaptic vesicles that relay signals across the synapse to the next neuron in the chain.
Neurotransmitters- Lock and key
Each neurotransmitter has it’s own molecular structure, which means it will only fit to a particular postsynaptic receptor- much like a lock and key.
Examples of specialist functions of neurotransmitters
Dopamine - pleasure
(Imbalance in dopamine causes schizophrenia)
Serotonin - mood
(Imbalance in serotonin causes depression)
Why can neurons only transmit information in one direction at a synapse?
Neurotransmitters are released by the presynaptic neuron and received by the postsynaptic neuron- so it can’t go the other way!
What are the two effects that neurotransmitters can have on neighbouring neurons?
Excitatory or inhibitory effect
Excitation
Excitation occurs when excitatory neurotransmitters stimulate the postsynaptic receptor resulting in an increase in the positive charge of the postsynaptic neuron.
This increases the likelihood of the postsynaptic neuron firing and passing on the electrical signal.
This is known as a excitatory postsynaptic potential (EPSP).
Inhibition
Inhibition occurs when inhibitory neurotransmitters stimulate the postsynaptic receptor resulting in an increase in the negative charge of the postsynaptic neuron. This decreases the likelihood of the postsynaptic neuron firing and passing on the electrical signal. This is known as a inhibitory postsynaptic potential (IPSP).