Biopsychology

• Nervous system: Consists of the central nervous system and the peripheral nervous system. Communicates using electrical signals.
• Central nervous system (CNS): Consists of the brain and the spinal cord and its the origin of all complex commands and decisions.
• Peripheral nervous system (PNS): Sends information to the CNS from the outside world, and transmits messages from the CNS to muscles and glands in the body.
• Somatic nervous system (SNS): Transmits information from receptor cells in the sense organs to the CNS. It also receives information from the CNS that directs muscles to act.
• Autonomic nervous system (ANS): Transmits information to and from internal bodily organs. It is 'autonomic as the system operates involuntarily. It has two main divisions: the parasympathetic nervous system and the sympathetic nervous system.
• The nervous system has two main functions:

  • To collect, process and respond to information.
  • To co-ordinate the working of different organs and cells in the body.
• Brain: Centre of all conscious awareness, the outer layer (Cerebral cortex) is only 3mm thick and covers the brain like an orange peel. It is highly developed in humans and is divided into two hemispheres.
• Spinal cord: Extension of the brain, passes messages to and from the brain and connects nerves to the PNS. Responsible for reflex actions.
• The ANS governs vital functions in the body such as breathing, heartrate, digestion and stress responses.
• The SNS governs muscle movement and receives information from sensory receptors.
• Order of the human nervous system:

  • Peripheral nervous system & Central nervous system
  • Autonomic and Somatic (PNS) & Brain and spinal cord (CNS)
  • Sympathetic and Parasympathetic (ANS)
• The endocrine system acts more slowly and uses glands and hormones to affect behaviour.
• The pituitary gland controls the release of hormones from all other glands in the body.
• Main endocrine glands:

  • Hypothalamus
  • Pituitary
  • Thyroid
  • Parathyroid
  • Adrenals
  • Pancreas
  • Ovaries (Female)
  • Testes (Male)
• The endocrine system and the ANS work together during stressful situations. The hypothalamus activates the pituitary gland which triggers the sympathetic branch of the ANS. The ANS then changes from its normal parasympathetic state to its sympathetic state.
• Adrenaline: Stress hormone is released from the adrenal glands into the bloodstream. This triggers changes to the body to prepare for a flight or fight response.
• Immediate and automatic: Flight or fight happens in an instant as soon as a threat is detected. The sympathetic state kicks in making physical changes to how a person is acting.
• Parasympathetic action: Once the threat has passed the PNS retuns the vody to its normal resting state. Its actions are antagonistic to the sympathetic system. This can be referred to as the rest and digest response.
• Sympathetic state (Changes):

  • Increases heart rate
  • Increases breathing rate
  • Dilates pupils
  • Inhibits digestion
  • Inhibits saliva production
  • Contracts rectum
• Parasympathetic state (Changes):

  • Decreases heartrate
  • Decreases breathing rate
  • Constricts pupils
  • Simulates digestion
  • Simulates saliva production
  • Relaxes rectum
• Neuron: The basic building blocks of the nervous system, they are nerve cells that process and transmit messages through electrical and chemical signals.
• Sensory neurons: These carry messages from the PNS to the CNS. They have long dendrites and short axons.
• Relay neurons: These connect the sensory neurons to the motor neurons and other relay neurons. They have short dendrites and long axons.
• Motor neurons: These connect the CNS to effectors such as muscles and glands. They have short dendrites and long axons.
• Structure of a neuron:

  • The cell body includes a nucleus which contains the genetic material of the cell.
  • Dendrites protrude from the cell body and carry nerve impulses from neighboring neurons to the cell body.
  • The axon carries impulses away from the cell body and are covered in myelin sheath that protects it and speeds up transmission.
  • The myelin sheath is segmented by gaps called nodes of Ranvier which forces the impulse to jump across gaps speeding it up.
  • At the end of the axon is terminal buttons that communicate with the next neuron in the chain across a gap known as the synapse.
• Location of a neuron:

  • Cell body's of a motor neuron may be in the CNS but the axons form part of the PNS.
  • Sensory neurons are located outside of the CNS in clusters known as ganglia.
  • Relay neurons make up 97% of all neurons and are mostly found in the brain and visual system.
• Electrical transmission: When a neuron is in resting state the inside of the cell is negatively charged compared to the outside. When activated by a stimulus the inside of the cell becomes positively charged causing action potential to occur. This creates an electrical impulse that travels down the axon.
• Chemical transmission: Neurons communicate within groups known as neural networks. Each neuron is separated by a synapse. The signals between each synapse is transmitted chemically.
• Neurotransmitter: Brain chemicals released from synaptic vesicles that relay signals across the synapse. They can be either excitatory or inhibitory.
• Excitation: When a neurotransmitter increases the positive charge of the postsynaptic neuron. This increases the likelihood that the postsynaptic neuron will pass on the electrical impulse.
• Inhibition: When a neurotransmitter increases the negative charge of the postsynaptic neuron. This decreases the likelihood that the postsynaptic neuron will pass on the electrical impulse.