B3.1 Nervous System Flashcards
Function of nervous system
To detect changes in the environment and respond to these changes to maintain homeostasis
Name given to change in environment
Stimulus
Name group of cells responsible for detecting a stimulus
Sensory receptors
Where are receptor cells generally found
Sense organs
Some common examples of sense organs and their stimulus (5 senses)
Eye - Light
Tongue - Chemical tastes (in food and drink)
Nose - Chemical smells (in the air)
Skin - Temperature, pressure and pain
Ears - Sound
Name given to cells that carry out the response
Effectors
2 types of effectors giving an example response for each
Muscles - respond by contracting
Glands - respond by secretions
2 key components of the nervous system
Central nervous system (CNS)
Peripheral nervous system (PNS)
Key components of nervous system
Brain
Spinal cord
Nerves
Central nervous system
Composed of brain and spinal cord
Brain is only involved in voluntary actions
Involved in both voluntary and involuntary actions
Peripheral nervous system
PNS is composed of nerve cells that carry information to and from CNS in spinal cord
Invovled in both voluntary and involuntary actions
3 main types of nerve cell including their pathway
Sensory – neurones that carry information as electrical impluses from receptors in the sense organs to CNS
Relay – neurones that carry electrical impulses from sensory neurones to motor neurones, found in CNS
Motor – neurones that carry electrical impulses from CNS to effectors
Direction of impulse
Direction in which a signal travels through a nerve
Type of signal is transmited by nervous system
Electrical
Difference between nerve and neurone
Neurones = specialised cells that conduct electrical impulses through body
Nerve = bundle of many nerve fibres enclosed within a protective sheath
Nerve fibres = long axons of neurones together with any associated tissues
Pathway for a ‘voluntary action’
Stimulus → Receptor cells → Sensory neurone → Spinal cord → Brain → Spinal cord → Motor neurone → Effector → Response
What is menat by a ‘coordinated’ response
Ability of brain to process information from many sensory receptors simultaneously and send a series impulses to different parts of the body to produce the required actions
Direction of impulse through neurone with reference to labels
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2
Impulse travels from dendrites (1) through neurone to axon terminals (4)
Parts of a motor neurone
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2
1) Dendrites
2) Cell body
3) Axon
4) Axon terminals
Cell type that surrounds axon of certain neurones and their purpose
Schwann’s cells
Collectively they form MYELIN SHEATH - insulates axon and increase speed of transmission
Gaps between these cells = nodes of Ranvier
Synapse
Area between axon terminals of pre-synaptic (previous) neurone, and dendrites of post-synaptic (next) neurone
Synapse aka synaptic cleft
Name to mode of transmission within a synaptic cleft / synapse
Chemical
Pathway of transmision from axon terminals pre-synaptic neurone to post-synaptic neurone
Electrical signal arrives at axon terminals of the pre-synaptic neurone.
Vesicles containing neurotransmitters stimulated.
Neurotransmitters difuse out of pre-synaptic neurone into synaptic cleft.
Neurotransmitters difuse across synaptic cleft.
Neurotransmitters bind to receptors dendrites of the post-synaptic neurone
Electrical signal triggered by neurotransmitters in the post-synaptic neurone
e.g electrical → chemical → electrical
Simple:
The neurotransmitters bind to receptors on the next neurone.
Neurotransmitters diffuse across the synapse.
The presence of the neurotransmitter causes the production of an electrical impulse in the next neurone.
Organelle in abundance in neurones
Mitochondria to provide energy
Difference between voluntary and reflex action
Voluntary actions involve conscious thought
Reflex actions are automatic (involuntary) reactions, they are unconscious missing out the brain, occuring without thinking