The Nervous System
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How heavy is the brain?
1.5kg
What does the nervous system consist of?
Brain, spinal cord and peripheral nerves
What are the types of cells in the brain?
Neurons and glial cells
What are the three main types of neurons?
• Sensory neurons • Motor neurons • Interneurons
What do sensory neurons do?
They are connected to receptors specialised to detect and respond to different attributes of the internal and external environment
What do motor neurons do?
They control the activity of muscles and are responsible for all forms of behaviour including speech
What type of neuron exist in the greatest quantity?
Interneurons
Where are interneurons?
Situated between the sensory and motor neurons
What do interneurons do?
Mediate simple reflexes and responsible for highest functions of brain
What do glial cells do?
Support neurons
What do neurons consist of?
• Cell body 2. Processes: axons & dendrites
What do axons do?
Transmit information from neuron on to others
What do dendrites do?
Receive information being transmitted by axons of other neurons
What is something both processes (axons and dendrites) do?
Participate in specialised contacts called synapses
How are neurons organised?
They are organised in complex chains and network that are pathways where information in nervous system is transmitted
How are brain and spinal cord connected to sensory receptors and muscles?
Through long axons that make up peripheral neerves
What are the functions of spinal cord?
• Simple and complex reflexes 2. Forms a highway between body and brain for information to travel in both directions
What distinguishes human brain with others?
• large size of human brains in relation to body size • enormous increase in number of interneurons over course of evolution, making humans have a wide choice of reactions to environment
What do the brain consist of ?
Brain stem and cerebral hemispheres
What are the three parts of brain stem?
• hind-brain • diencephalon • mid-brain
What is hind-brain?
Extension of spinal cord
What do hind-brain consist of?
Contains networks of neurons that constitute centres of control of vital functions like breathing and blood pressure
What do cerebellum do?
Control and timing of movements
What do midbrain contain?
Groups of neurons that use predominantly a particular type of chemical messenger but all project up to cerebral hemispheres