biopsychology

• The nervous system Specialised network of cells in the human body & our primary internal communication system. Based on electrical and chemical signals
• What are the 2 main functions of the nervous system? 1. Collect, process & respond to information in the environment 2. Co-ordinate the working of different organs and cells in the body
• The nervous system is divided into... Central Nervous System (CNS) and Peripheral Nervous System (PNS)
• The CNS is made up of... Brain and spinal cord
• The brain - Centre of all conscious awareness - Outer layer (cerebral cortex) just 3mm thick and only found in mammals - Highly developed in humans; distinguishes our higher mental functions from other animals - Divided into 2 hemispheres
• The spinal cord - Extension of the brain - Passes messages to and from brain - Connects nerves to PNS - Responsible for reflex actions
• The peripheral nervous system... Transmits messages via millions of neurons to and from the CNS
• The PNS is further subdivided into... Autonomic nervous system (ANS) and somatic nervous system (SNS)
• The autonomic nervous system Governs vital bodily functions e.g. breathing, heart rate, digestion, sexual arousal, stress responses
• The somatic nervous system Governs muscle movement and receives information from sensory receptors
• The endocrine system - Works alongside the nervous system to control vital functions in the body - Works slower than NS but has more widespread and powerful effects
• How does the endocrine system work? - Various glands (e.g. the thyroid) secrete hormones into the bloodstream - Hormone affects any cell with receptor for that hormone - Most hormones affects cells in >1 organ and so have many diverse & powerful responses, e.g. thyroxine -> heart rate -> metabolic rate -> growth rate
• The pituitary gland - Key endocrine gland - Located in the brain - Often called 'master gland' as it controls the release of hormones from all other endocrine glands
• How is the fight or flight response triggered? 1. Stressor perceived 2. Hypothalamus activates pituitary gland 3. Triggers activity in sympathetic branch of ANS 4. ANS changes from normal parasympathetic state to psychologically aroused sympathetic state
• Adrenaline - Released from adrenal medulla (part of adrenal gland near kidney) into bloodstream - Triggers physiological changes (e.g. increased heart rate) which creates physiological arousal necessary for f/f response
• The fight or flight response is... Immediate and automatic
• Sympathetic vs parasympathetic state
• Parasympathetic action - Branch works opposite to SNS, actions antagonistic to SNS - Acts as a 'brake' and reduces activities of body that were increased by actions of sympathetic branch - Sometimes referred to as 'rest and digest' response
• Neurons - Nerve cells - Basic building blocks of nervous system - Provide nervous system with primary means of communication - Transmit signals electrically & chemically - 1b in human nervous system, 80% in brain
• Components of neurons Cell body, dendrites, axon, myelin sheath, nodes of Ranvier, terminal buttons
• Cell body Contains nucleus which contains genetic material
• Dendrites Carry nerve impulses from neighboruing neurons towards cell body
• Axon Carries impulses away from cell body down length of neuron
• Myelin sheath Fatty layer which protects axon & speeds up electrical transmission of impulse
• nodes of Ranvier Speed up transmission by segmenting myelin sheath, forcing transmission to 'jump' across gaps
• Terminal buttons Communicate with next neuron in chain across synapse
• What are the 3 types of neurons? Sensory, relay, motor
• Sensory neurons Carry messages from the PNS to the CNS. They have long dendrites and short axons.
• Relay neurons Connect sensory neurons to motor or other relay neurons. They have short dendrites and short axons.
• Motor neurons These connect the CNS to effectors such as muscles and glands. They have short dendrites and long axons.
• Where are motor neurons found? Cell bodies may be in CNS, axons form part of PNS
• Where are sensory neurons found? In the PNS, in clusters known as ganglia
• Where are relay neurons found? Mostly in the brain and visual system. RNs make up 97% of all neurons
• The firing of a neuron 1. Neuron in resting state, inside of cell negatively charged 2. Neuron activated by stimulus 3. Inside of cell becomes positively charged for a split second 4. Action potential occurs 5. Creates electrical impulse that travels down axon towards end of neuron
• Synaptic transmission 1. Electrical impulse travels down axon and reaches presynaptic terminal 2. Triggers release of neurotransmitters from synaptic vesicles 3. Neurotransmitters diffuse across synapse 4. Neurotransmitters taken up by postsynaptic receptor sites on dendrites of next neuron 5. Neurotransmitters converted back into electrical impulse
• Neurotransmitters Chemicals that diffuse across synapse to next neuron in chain
• Features of Neurotransmitters - Several types identified in brain, spinal cord and glands - Each has specific molecular strucutre that fits perfectly into a postsynaptic receptor site - Specialist functions e.g. acetylcholine found at each point where motor neuron meets muscle, casues muscle to contract - Excitatory (e.g. adrenaline) or inhibitory (e.g. serotonin) effect on neighbouring neuron
• Excitation Increases positive charge of postsynaptic neuron, making it more likely to fire
• Inhibition Makes postsynaptic neuron more negatively charged, making it less likely to fire
• Summation The net influence of the excitatory & inhibitory influences is summed; if the net influence is excitatory, the neuron will fire; if it is inhibitory, the neuron will not fire