Biopsychology Flashcards
The nervous system
Network of cells and our primary communication system, divided into the central nervous system and the peripheral nervous system
Divided into central and peripheral
2 main functions of NS
1) To collect, process and respond to information in the environment
2) To co-ordinate the working of different organs and cells in the body
Structure and functions of CNS
- CNS= brain and spinal cord
- brain is centre of all conscious awareness
- cerebral cortex (highly developed in humans) distinguishes our higher mental functions from animals
- spinal cord is extension of the brain; responsible for reflex actions
- spinal cord passes messages to and from brain + connects nerves to PNS
Structure and functions of PNS
- PNS transmits messages, via millions of neurons, to and from nervous system
- PNS is split into the automatic nervous system the somatic nervous system
- ANS governs vital functions in body such as breathing, heart rate, digestion, sexual arousal and stress responses
- SNS controls muscle movement and receives information from sensory receptors
The endocrine system
Works alongside the NS to control vital functions in the body through the action of hormones
-slower than NS but has widespread and powerful effects
Glands
Organs in the body that control hormones
- The major endocrine gland is the pituitary, located in the brain
- called ‘master gland’ bc it controls release of hormones from all the other endocrine glands in the body
Hormones
Secreted in the bloodstream and affect any cell in the body that has a receptor for that specific hormone
-e.g. thyroxine produced by thyroid gland affects cells in the heart and also cells thought the body, which increase metabolic rates. This in turn affects growth rates
The endocrine system and the ANS work together
E.g. fight or flight
- When stressor is perceived, hypothalamus triggers activity in sympathetic branch of ANS. ANS changes from normal resting state (parasympathetic state) to physiologically aroused state
- Stress hormone adrenaline is released from adrenal medulla into bloodstream
- Adrenaline triggers physiological changes in target organs in the body and causes, e.g. increased heart rate, dilation of pupils, decreased production of saliva. Called ‘fight or flight’
- Once threat has passed, parasympathetic NS returns body to resting state. This acts as a ‘brake’ and reduces activities of the body that were increased by sympathetic branch
Motor neurons
- Connect CNS to effectors such as muscle and glands
- Short dendrites and axons
Sensory neurons
- Carry messages from PNS to the CNS
- Long dendrites and short axons
Relay neurons
- Connect sensory neurons to motor neurons or other relay neurons
- Short dendrites and axons
Cell body (soma)
Includes a nucleus which. Contains the genetic material of the cell
Dendrites
Branch-like structures that protrude from the cell body. Carry nerve impulses from neighbouring neurons towards the cell body
Axon
Carries the electrical impulse away from the cell body down the neuron
- covered in a fatty layer of myelin sheath that protects the axon
- gaps in the axon (nodes of Ranvier) speed up the transmission of the impulse
Terminal buttons
At the end of the axon, communicate with the next neurons in the chain across synapse
Electric transmission
The firing of a neuron
- When neuron is in resting, inside of the cell is negatively charged compared to outside
- When neuron activated, inside of cell becomes positively charged for split second, causing an action potentials to occur
- This creates an electrical impulse that travels down axon towards end of the neuron
Synapse
A tiny gap where one neuron (presynaptic) can send a chemical message to an adjacent neuron (postsynaptic)
Signal transmission
Transmitted electrically within neurons but chemically between neurons (across the synapse)
The events that occur at the synapse
- When electrical impulse reaches presynaptic terminal, triggers release of neurotransmitter from synaptic vesicles
- Once neurotransmitter crosses gap, it’s taken up by postsynaptic receptor site on the next neuron
- Chemical message converted back into electrical impulse and process of electric transmission begins
Neurotransmitters
Chemicals that diffuse across the synapse to the next neuron in the chain
Examples of neurons
- Acetylcholine (ACh) founds where a motor neuron meets the muscle, causing muscles to contract
- Serotonin affects moods and social behaviours, involved as a cause of depression
Adrenaline
Generally excitatory, increasing the positive charge of the postsynaptic neuron, making it more likely the neuron will fire
Seratonin
Generally inhibitory, increasing the negative charge of the postsynaptic neuron, making it less likely to fire
Dopamine
Equally likely to have excitatory or inhibitory effects on the next neuron will fire
Summation
Excitatory and inhibitory influences are summed and must reach a certain threshold in order for the action potential of the postsynaptic neuron to be triggered
If the net effect of the neurotransmitters is inhibitory then the postsynaptic neurons is less likely to fire. It is more likely to fire if the net effect is excitatory
Synaptic transmission
Process by which one neuron communicates with another
Process of synaptic transmission
-Information is passed down the axon of the neuron as action potential
Once the action potential reaches the end of the axon it needs to be transferred to another neuron or tissue
It must cross over the synaptic gap between the presynaptic neuron and post-synaptic neuron
At the end of the neuron (in the axon terminal) are the synaptic vesicles, which contain neurotransmitters
- When the action potential reaches these synaptic vesicles, they release their contents of neurotransmitters
- Neurotransmitters then carry the signal across the synaptic gap
- They bind to receptor sites on the post-synaptic cell, thereby completing the process
