4.5.2.1 Structure and Function Flashcards
3 components of the nervous system:
- brain
- nerves
- spinal cord
What may automatic control systems involve?
automatic control systems may involve nervous responses or chemical responses
Function of the nervous system:
enables humans to react to their surroundings and coordinate their behaviour
How do impulses travel?
stimulus → receptor → coordinator → effector → response
- There is a stimulus - change in environment
- The receptor cells detect the stimulus - change in environment
- Receptor cells convert a stimulus into an electrical impulse
- Electrical impulses (information) travel from the receptors along sensory neurones to relay neurones in central nervous system (CNS - brain and spinal cord)
- When the impulses reach a synapse between sensory neurone and relay neurone - trigger chemicals (neurotransmitters) to be released - these chemicals cause impulses to be sent along relay neurone
- The information is processed and integrated and the CNS (spinal cord or brain) coordinates the appropriate response of effectors
- When impulses reach a synapse between the relay neurone and motor neurone - chemicals released allowing impulses to be sent along motor neurone
- The electrical impulses travel along motor neurone to effector (muscle or gland)
- The effectors (muscle or gland) carry out the response - this may be muscles contracting or glands secreting hormones
How does the nervous system react to changes in the environment?
- Stimulus - change in the environment
- Receptor - detection of the change
- Sensory neurone
- Co-ordination (CNS) - integration of information
- Motor Neurone
- Effector - muscle or gland
- Response - contraction or secretion of hormones
What do sense organs contain?
sense organs contain receptors that are sensitive to detect stimuli
Nerve impulse:
electrical signal that passes along a neurone
Neurone:
nerve cells that carry electrical signals
How are neurones adapted/specialised to their function?
- Has a long, thin shape which allows impulses to travel long distances in the boy and makes it faster to send electrical messages
- Its axon is covered in rings of myelin sheath
- The myelin sheath stops the electrical signals from travelling down the axon because it is an electrical insulator
- This means the electrical signals have to jump between gaps of the myelin sheath, speeds up the conduction of electrical impulses and allows them to travel much faster
Reflex action:
- actions that are automatic and rapid - do not involve the conscious part of the brain/bypass the brain and go to spinal cord for extra speed
- help to protect from danger/harm
- a response / reaction
- involuntary - not under conscious control
Examples of reflex actions:
- startle reflex - moving away, contraction of arm and leg muscles
- with-drawl reflex - moving away from potentially harmful things
- iris reflex - pupils become smaller in bright light
Why are reflex actions important?
- important as they can prevent an individual from getting injuries
- information travels down a pathway called reflex arc - allows vital responses to take place quickly
- different from usual responses to stimuli as impulse does not pass through conscious part of brain
Diagram of neural pathway in reflex arc:
Reflex arc:
the passage of information in a reflex (from receptor to effector) is a reflex arc
Process of reflex arc:
stimulus —> receptor neurone —> sensory neurone —> spinal cord / unconscious part of brain (relay neurone) —> motor neurone —> effector
- There is a stimulus - change in environment
- The receptor cells detect the stimulus - change in environment
- Receptor cells convert a stimulus into an electrical impulse
- Electrical impulses (information) travel from the receptors along sensory neurones to relay neurones in central nervous system (CNS - brain (not conscious pat of brain) and spinal cord)
- When the impulses reach a synapse between sensory neurone and relay neurone - trigger chemicals (neurotransmitters) to be released - these chemicals cause impulses to be sent along relay neurone
- The information is processed and integrated and the CNS (spinal cord or part of brain that isn’t conscious) coordinates the appropriate response of effectors
- When impulses reach a synapse between the relay neurone and motor neurone - chemicals released allowing impulses to be sent along motor neurone
- The electrical impulses travel along motor neurone to effector (muscle or gland)
- The effectors (muscle or gland) carry out the response - this may be muscles contracting or glands secreting hormones
- Quicker than normal responses as impulses don’t travel through conscious part of brain and don’t have to be thought about
How do electrical messages cross the gap between neurones and why is it slow?
by the relay neurone - takes time from neurone to diffuse across synapses cleft and bind with receptors on membrane of second neurone
Stimuli:
changes in the environment
Receptors:
cells that detect stimuli
What are the different types of receptors?
- receptors in the eye that are sensitive to light - retina
- receptors in the ear that are sensitive to sound - hairs on cochlear
- receptors in the ears that are sensitive to changes in position and enable us to keep our balance
- receptors on the tongue and in the nose that are sensitive to chemicals and enable us to taste and smell
- receptors in the skin that are sensitive to tough, pressure, pain and temperature changes
What can receptors form part of?
receptors can form part of larger, complex organs e.g. retina in the eye covered in light receptor cells
What do light receptor cells have?
like most animal cells have nucleus, cytoplasm and cell membrane
Sensory neurone:
transmit impulses from receptor to CNS
Diagram of sensory neurone:
Synaps(es):
junction between 2 neurones
- the microscopic gap between the end of one neurone and the start of the next
- most often form between axons and dendrites (where info is passed from one neurone to the next)
How do impulses pass between neurones?
Stage 1
- When a memory impulse arrives at the end of the first neurone, a neurotransmitter (chemical) is released into the synapse
- The chemical diffuses from one synapses side to the other in one direction after vesicles move to the end of the neurone
Stage 2
- the chemical is released from vesicles into the synaptic cleft and diffuses across the gap from a high concentration to a low concentration across the cleft
Stage 3
- when the neurotransmitter molecules reach the far side of the synaptic cleft it binds to receptors on the membrane of the second neurone
- this causes an impulse to start in the next membrane
- vesicles fuse with the cell membrane
Diagram of synapse:
Co-ordination centre:
part of the body which receives and processes information from receptors around the body
Central nervous system:
- brain and spinal cord
- processes and integrates the information and the CNS coordinates the appropriate response of effectors
- connected to the body by sensory neurones and motor neurones
Relay neurones:
relay neurones pass the electrical impulses from sensory neurones to motor neurones
Where are relay neurones found?
spinal cord or brain(CNS)
Diagram of relay neurone:
Motor neurone:
transmits electrical impulses from the CNS to the effector
Diagram of motor neurone:
Effectors:
- respond to electrical nerve impulses
- are muscles or glands and carry out the response
Different types of stimuli:
- light (sight)
- chemicals (taste and smell)
- pressure (touch)
- temperature
- sound
