neurones and synaptic transmission

Question 1

Intro

Answer 1

• Over 100 Billion neurons in the human nervous system
80% in the brain
• Electrical and chemical transmission
• Primary means of communication for the nervous system

Question 2

Electrical transmission occurs within a neuron

Answer 2

• Resting state = negatively charged cell.
  -Stimulus activates neuron - inside becomes positively charged.
  -Action potential occurs.

Question 3

sensory neurons

Answer 3

• Sensory neurons carry messages from the peripheral nervous system to the central nervous system.
-found in receptors eg eyes ears tongue
-when nerve impulses reach brain-translated to sensations like touch

Question 4

motor neurons

Answer 4

-found in central nervous system-connect CNS to effectors like muscles and glands-control muscle movements

-When motor neurons are stimulated they release neurotransmitters that bind to the receptors on muscles to trigger a response, which lead to movement.

Question 5

relay neurons

Answer 5

• Relay Neurons are found between sensory input and motor output/response.
• Relay neurons are mainly in the brain and spinal cord and allow sensory and motor neurons to communicate.

Question 6

structure of neurons

Answer 6

• Dendrites are branch like structures that receive nerve impulses from neighbouring neurons or sensory receptors and carry them towards the cell body.
  -The cell body of a neuron includes the nucleus which contains the genetic material of the cell.
  -The axon carries impulses, in the form of an electrical signal known as an action potential, away from the cell body down the length of the neuron to the axon terminal.
  -The axon is insulated by the myelin sheath to protect it and speed up electrical transmission of the impulse.
  -The Myelin sheath is segmented by the Nodes of Ranvier. These are the gaps between the myelin sheath that speed up the transmission of impulses by forcing the impulse to jump across the gaps.
  -Terminal buttons / axon terminals are at the end of the axon; these communicate with the next neuron across the synapse.

Question 7

synaptic transmission

Answer 7

Neurons communicate with each other within groups known as neural networks.
- Each neuron is separated from the next by a small gap called the synapse.
-Now whilst information within neurons is transmitted electrically, between neurons information is transmitted chemically via neurotransmitters.

-Impulse arrives at the presynaptic neuron.
-Neurotransmitters released from vesicles.
• Diffuse across synapse.
• Bind to receptor sites on postsynaptic neuron.
-Chemical message is converted back into electrical impulse.
• Neurotransmitters are broken down and reabsorbed into the presynaptic neuron.

Question 8

neurotransmitters

Answer 8

• The chemicals that diffuse across the synapse to the next neuron in the chain.
  -E.g. Serotonin, Dopamine & Acetylcholine
  -Post-synaptic receptor site.
  • Always a perfect fit into specific receptor site.
  • Conversion of chemical to electrical message.
  -Each neurotransmitter has a specific function eg acetylcholine makes muscles contract.

Question 9

excitation and inhibition

Answer 9

Neurotransmitters can have one of two effects on neighbouring neurons.
-Some cause neighbouring neurons to become more positively charged.
- Makes the neuron more likely to fire.
• E.g. Adrenaline.

-Others result in an increased negative charge.
• Makes the neuron less likely to fire
• Serotonin.

Process of Summation - Majority rules-if it’s more positive or negative that determines whether it fires or doesn’t.

Question 10

structure and function of sensory neuron

Answer 10

Long dendrites and short axon

Carry messages from the PNS (receptors/ senses) to the CNS

Question 11

structure and function of relay neuron

Answer 11

Short dendrites and short axons

These connect sensory neurons to motor neurons.

Question 12

structure and function of motor neurons

Answer 12

Short dendrites long axon

Connect the CNS to effectors, such as muscles and glands.