biopsychology revision

the nervous system

key features of the nervous system

  • the nervous system is a specialised network of cells and our primary communication system

  • it is based on electrical and chemical signals whereas the endocrine system is based on hormones

  • main functions:

  1. to collect, process and respond to information in the evnironment

  2. to coordinate the working of different organs and cells in the body

the structure and function of the central nervous system

  • CNS is made up of the brain and spinal cord

  • the brain is the centre of conscious awareness

  • the outer layer of the brain, the cerebral cortex (3mm thick), is highly developed in humans and is what distinguishes our higher mental functions from those animals

  • the brain hemisphere is divided into two hemisphere

  • the spinal cord is an extension of the brain and is responsible for reflex actions

  • it passes messages to and from the brain and connects nerves to the PNS

the structure and function of the peripheral nervous system

  • the PNS transmits messages, via millions of neurons, to and from the nervous system

  • the PNS is further subdivided into:

  1. autonomic nervous system (ANS) governs vital functions in the body such as breathing, heart rate, digestion, sexual arousal and stress responses

  2. somatic nervous system (SNS) governs muscle movement and receives information from sensory receptors

the endocrine system

key features of the endocrine system

  • the endocrine system works alongside the nervous system to control vital functions in the body through the action of hormones

  • it works more slowly than the nervous system (seconds instead of milliseconds) but has widespread and powerful effects

glands

  • glands are organs in the body that produce hormones

  • the key endocrine gland is the ‘pituitary gland’ located in the brain. it is called the ‘master gland’ because it controls the release of hormones from all the other endocrine glands in the body

hormones

  • hormones are secreted in the bloodstream and affect any cell in the body that has a receptor for particular hormones

  • for example, thyroxine produced by the thyroid gland affects cells in the heart and also cells throughout 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

  • often the endocrine system and the ANS work in parallel, for instance during a stressful event

  • stressor perceived by the hypothalamus which activates the pituitary

  • the sympathetic nervous system is now aroused

  • adrenaline (stress hormone) is released from the adrenal medulla into the bloodstream. this delivers the aroused state causing changes in the target organs in the body e.g. increased heart rate, dilated pupils, decreased production of saliva. this is called the fight or flight response

  • immediate and automatic - this response happens the instant a threat is received

  • parasympathetic nervous system (rest and digest) takes over once the threat has passed. this returns the body to its resting state. this acts as a brake and reduces the activities of the body that were increased by the actions of the sympathetic branch (rest and digest)

neurons

types of neurons

  • there are 100 billion nerve cells in the human nervous system, 80% of which are located in the brin

  • by transmitting signals electrically and chemically, these provide the nervous system with its primary means of communication

  • there are three types of neuron

  1. sensory neurons carry mesages from the PNS to the CNS. they have long dendrites and short axons. located in the PNS in clusters called ganglias

  2. relay neurons connect sensory neurons to motor or other relay neurons. they have short dendrites and short axons. of a;; neurons, 97% are relay neurons and most are in the brain and visual system

  3. motor neurons connect the CNS to effectors such as muscles and glands. they have short dendrites and long axons. cell bodies may be in the CNS but long axons form part of the PNS

structure of a neuron

  • neurons vary in size but all share the same basic structure:

  • cell body (soma) includes a nucleus which contains the genetic material of the cell

  • dendrites - branchlike structures that protrude from the cell body. these carry nerve impulses from neighbouring neurons towards the cell body

  • axon - carried the electrical impulse away from the cell body down the length of the neuron

    • it is covered in a fatty layer of m