Action of recreational drugs Neurones & Neurotransmitters KA 3: The cells of the nervous system and neurotransmitters at synapses (a) Structure and function of neurones (e) Action of recreational drugs Key Area 3: Neurones & Neurotransmitters (b) Neurotransmitters at synapses (d) Neurotransmitters, moods and behaviour (c) Function of converging, diverging and reverberating pathways

Key Area 3(a) Structure and function of neurones Be able to identify the following structures in a diagram: Dendrites Cell body Axons Myelin sheath State the function of the above structures State what is what meant by myelination State the difference in impulse conduction between 2 year olds and adolescents and adults Describe and explain the effects of destroyed myelin sheaths State 4 functions of glial cells

Revision of Neurones CELL BODY NERVE FIBRE (Axon)‏ Our nervous system is made of nerve cells called neurones Consist of a cell body attached to very long nerve fibre Electrical impulses carry messages along neurones.

Neurones There are 3 types of neurones; Sensory neurones Inter neurones Motor Neurones These neurones allow an electrical impulse to pass along them resulting in a reflex action.

These cells provide the body with a means of rapid communication. Pupils highlight the yellow labels in their notes These cells provide the body with a means of rapid communication. Although they appear very different they all have the same basic structure.

Dendrites Cell Body Axon Node Node Direction of Impulse Dendrites Cell Body Axon

Structure Function Dendrite Cell body Axon Myelin sheath Receives nerve impulse and passes them towards the cell body. Cell body Control centre containing nucleus and ribosome's for protein synthesis (neurotransmitter production) Axon Carries nerve impulses away from the cell body Myelin sheath Layer of fatty material which increases the speed of impulse conduction from node to node.

Young kids (particularly toddlers) are usually very uncoordinated. Myelination Young kids (particularly toddlers) are usually very uncoordinated. Why do you think this is?

Myelination Myelination is the development of myelin around the axon. This process continues from birth until adolescence. Consequently the speed of impulse conduction in younger children is slower than in older children. As a result children under 2 are not as coordinated and cannot respond to external stimuli as rapidly as older children.

Glial Cells Neurones only account for around 50% of the cells in your nervous system The rest are called Glial cells They carry out various roles and your nervous system could not function without them! Video is a great summary of what they know so far. Goes into individual Glial cell types (which they don’t need to know) but does give a good overview of the various functions. The Nervous System, Part 1: Crash Course A&P #8 – Up to 5:24

Glial Cells

Glial Cells Glial cells account for around 50% of the cells found in the nervous system and physically support the neurones by carrying out various functions. Their functions include: producing the myelin sheath maintaining a homeostatic (ideal) environment around the neurones removing debris by phagocytosis Change to pionts

Diseases of the Nervous System Some diseases destroy the myelin sheath causing a loss of coordination. For example: Polio Tay-Sachs disease Polio – Caused by a virus. Symptoms: fever and pains in the neck and back muscles. In a minority of cases, asymmetrical weakness of certain muscles occurs, followed by paralysis of one or more body parts, commonly a limb. No cure, can be prevented by a vaccination Tay-Sachs – Genetic disorder (a single gene mutation). Symptoms: The most common form of the disease (infantile TSD) results in the continuous deterioration of physical and mental abilities from the age of around 6 months. The child becomes deaf and blind. Muscles fail to work and paralysis follows. The child normally dies at about age 4 years. No cure.

Multiple Sclerosis If someone suffers from MS then their own immune system is damaging the myelin sheaths around axons. This can result in a lose of coordination https://www.youtube.com/watch?v=VIoDr8ugbqI (2.11) MS – cause unknown. Symptoms - numbness, walking difficulties, impaired vision and progressive loss of coordination as the ability to control muscles is lost. ‘Cure’ being developed through use of stem cells.

Diseases of the Nervous System Some diseases destroy the myelin sheath causing a loss of coordination. For example: Polio Multiple sclerosis Tay-Sachs diseases