Structure and Function of Neurons

Neurotransmitter (2)

- Brain chemicals released from synaptic vesicles that relay signals across the synapse from one neuron to another. - Can be divided into those that perform an inhibitory function and those that perform an excitatory function

Sensory neuron (3)

- Carry nerve impulses from the peripheral nervous system to the CNS - Found in receptors such as the eyes, ears, tongue and skin. - Long dendrites and short axons

Neurotransmitter explained (4)

- Chemicals that diffuse across the synapse to the next neuron in the chain - Once it has crossed, it is taken up by the postsynaptic receptor site (dendrites) of the next neuron. - Here, the chemical message is converted back into an electrical impulse and the process of transmission begins again in this other neuron - Each neurotransmitter has its own molecular structure that fits perfectly into a post-synaptic receptor site

Motor neurons (2)

- Connect the CNS to effectors such as muscles and glands; release neurotransmitters which bind to receptors - Short dendrites and long axons

Relay neurons (2)

- Connect the sensory neurons to the motor or other relay neurons - Short dendrites and short axons

Explain synaptic transmission (4)

- Neurons communicate with each other within groups known as neural networks - Each neuron is separated by a gap called a synapse - Signals between neurons are transmitted chemically across the synapse - When the electrical impulse reaches the end of the neuron, the presynaptic terminal, it triggers the release of neurotransmitter from sacs called synaptic vesicles

Excitation and inhibition (3)

- Neurotransmitters either have an excitatory or inhibitory effect on the neighbouring neuron - Neurotransmitter serotonin causes inhibition in the receiving neuron resulting in the neuron becoming more negatively charged and less likely to fire - In contrast, adrenaline causes excitation of the post-synaptic neuron by increasing its positive charge and making it more likely to fire

Types of neuron (3)

- Sensory - Relay - Motor

Neuron (2)

- The basic building blocks of the nervous system; nerve cells that process and transmit messages through electrical and chemical signals - 100 billion in the human nervous system, 80% located in the brain

Structure of a neuron (5)

- The cell body (soma) includes a nucleus, which contains the genetic material of the cell - Dendrites protrude from the cell body which carry nerve impulses from neighbouring neurons towards cell body - Axon carries impulses away from cell body down the neuron; it is covered in a fatty layer of myelin sheath that protects the axon and speeds up electrical transmission - Myelin sheath is segmented by gaps called nodes of Ranvier that speed up transmission by forcing the impulse to 'jump' across the gaps along the axon - At the end of the axon are terminal buttons that communicate with the next neuron in the chain across a gap known as the synapse

Electric transmission (firing of a neuron) (3)

- When a neuron is in a resting state the inside of the cell is negatively charged compared to the outside - When a neuron is activated by a stimulus, the inside of the cell becomes positively charged for a split second causing an action potential to occur - This creates an electrical impulse that travels down the axon towards the end of the neuron

Specialist functions of neurotransmitter example

ACh is found at each point where a motor neuron meets a muscle, and upon its release it will cause muscles to contract

Synaptic transmission

The process by which neighbouring neurons communicate with each other by sending chemical messages across the synapse that separates them