nervous system


nervous system

Nervous system is divided into two sub systems - the central nervous system (CNS) and the peripheral nervous sytem (PNS)

Central nervous system

  • made up on nerouns in the brain and spinal cord
  • brain is centre of all conscoius awareness and main job is to ensure life is maintained

The perihperal nervous sytem

Somatic nervous system (SNS)- transmit and recieve messages from senses. also directs muscles to react and move

Automatic nervous sytem (ANS) - transmit and recive messages from the organs and divided into sympathetic system (fight or flight) and the parasympathetic system (returns body back to normal

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sensory, relay and motor neurons

Motor neuron

  • the moving neuron
  • they carry information away from CNS.
  • largest cell body with a sigle projecting axon

Sensory neuron

  • the sensing neuron
  • carry information to the CNS.

Relay neuron

  • thinking, feeling, deciding neuron
  • carry signal between ither neurons - sensory and motor.

see diagram in book

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endocrine system

The endocrine system is a systme of glands that produce hormones

These glands control many biological functions and affect many behaviours. it does this by releasing chemicals called hormones into the bloodstream.

Hormones are chemical messengers that regulate a range of processes in the body.

They travel rapidly in the bloodstream to parts of the body where they can either have a very specific influence or a general effect.

example - part of the adrenal gland called the adrenal medulla is triggered by the sympathetic division of the ANS to produce adrenaline. this contributes to physiological arousal.

Functions of some glands and hormones

Adrenal- imprortant part of fight or flight as it facilitates the releaseof adrenaline

Testes- facilitate the relase of testosterone

Ovaries- facilitate the release if oestrogen and progesterone.

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fight or flight response

  • Appraisal of the situation as threatening
  • Hypthalamus (brain-CNS)
  • Triggers sympathetic branch of the ANS (PNS)
  • Tells adrenal medulla to release adrenaline (endocrine system)
  • Triggers physiological changes- heart rate increases, pupils dilated
  • Hypothalamus detects adrenaline and stimulates the parasympathetic branch of the ANS to return body back to normal (rest and digest)

increased heart rate - to speed up the blood flow of organs and improve spreadof adrenaline

faster breathing- to increase oxygen intake

pupil dilation- to improve vision

reduced functioning of the digestive and immune system- to save energy for prioritised functions, such as runninh

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synaptic transmission

An action potential is released down into the presynaptic neuron. This causes the vesicles to move towards the presynaptic membrane and fuse with it. This releases the neurotransmitters into the synapse. The neurotransmitters move towards the recoptor sites of the post synpatic membrane and fuse in a 'lock and key' fashion

ion channels open up causing an exchange of positive and negative ions which creates an electric charge, this means the signal which began in one neuron has now been transmitted to another.

Neurons can produce either excitation or inhibition in the receing neuron. Excitation occurs when neurotransmitter messages make it more likely that receing neurons will themselves 'fire' an action potential. As the name suggests inhibatitaion makes the firing less likely to happen.

If the sum of the excitatory impluses is greater than inhibitory ones then the neuron will fire and if there are more inhibitory impluses then it wil no fire.

Once the neurotransmitter has completed its task, it must be inactivated. one way it can do that is to drift away so it has no furtehr effect. another way s that it can be broken down by enzymes.

The most common way for the neurotransmitter to be recylced is through reuptake back into the axon terminal.

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