Topic 2 - The Nervous System Flashcards
What is the central nervous system?
Brain and spinal cord
What is the spinal cord?
A long, thin structure composed of neurones that extends from the medulla oblongata down the spine.
What is the function of the spinal cord?
Connects the peripheral nervous system (nerves outside of the CNS) to the brain.
Describe the structure of the brain
Consists of three main regions:
● Cerebrum
● Cerebellum
● Medulla oblongata
Identify the structures of the brain labelled in the diagram
cerebrum is top bit
medulla oblongata is stem bit and cerebellum is circular thing next to the stem
Describe the structure of the cerebrum
● Largest region of the brain
● Divided into two hemispheres
What is the function of the cerebrum?
Involved in: ● Intelligence ● Language ● Memory ● Emotion ● Visual and sensory processes
What is the function of each cerebral hemisphere?
● Left hemisphere receives sensory information from the right side of the body and controls muscle coordination on the right
● Right hemisphere receives sensory information from the left side of the body and controls muscle coordination on the left
Where is the cerebellum located?
Lower region of the brain
What is the function of the cerebellum?
nvolved in:
● Coordination of muscles
● Voluntary movement e.g. walking
● Non-voluntary movement e.g. balance
What is the function of the medulla oblongata?
Controls automatic processes in the body e.g. breathing rate, heart rate, peristalsis
What methods, other than surgery, are used by doctors to observe the brain?
● CT scan
● PET scan
What is a CT scan?
A procedure that uses X-rays to produce 3D cross-sectional images of the brain
Describe how CT scans are useful to investigate brain function
● CT scans show damaged regions of the brain e.g. areas of swelling, bleeding
● Observations of the patient’s symptoms can enable scientists to determine the function of the damaged region
What does a PET scan involve?
● Radioactive substance injected into a patient’s
bloodstream and taken up by tissues in the brain
● Radiation emitted by tissues detected, enabling the identification of active and inactive regions of the brain
Describe how PET scans are useful to investigate brain function
● Show which areas of the brain are active and which areas are not
● Comparisons of brain activity in healthy patients and patients with brain damage allow scientists to determine
the functions of inactive regions
Why is it difficult to treat damage to the CNS?
● Damage to neurones is permanent and cannot be
repaired (as nerve cells don’t divide by mitosis)
● Hard to reach some areas of the brain
● Risk of further permanent damage to other areas of the CNS during surgery
What is the function of the nervous system?
Allows an organism to rapidly react to environmental and internal changes
What are neurones?
Nerve cells adapted to quickly transmit
nerve impulses. They are the functional units of the nervous system.
What is the function of the axon?
● Carries impulses away from the cell body
● Enables the transmission of nerve impulses
over long distances
What is the function of the dendrites and dendrons?
● Carry impulses towards the cell body
● Dendrites provide a large surface area to
receive impulses
What is the role of the myelin sheath?
● Electrically insulating layer
● Surrounds the axon and increases the speed
of impulses
Outline the function of a sensory neurone
Carries impulses from receptors to the
central nervous system
Describe the structure of a sensory neurone
● Long dendron carries impulses from receptors to the cell body
● Cell body found part way along the neurone
● Short axon carries impulses from the cell body to the CNS
Outline the function of a motor neurone
Carries impulses from the central nervous system to effectors
Describe the structure of a motor neurone
● Short dendrites carry impulses from the CNS to the cell body
● Cell body found at one end of the neurone
● Long axon carries impulses from the cell body to the effectors
Outline the function of a relay neurone
Carries impulses from sensory neurones
to motor neurones within the central nervous system
Describe the structure of a relay neurone
● Short dendrites carry impulses from sensory
neurones to the cell body
● Short axon carries impulses from the cell body to motor neurones
Describe how the central nervous system coordinates a response to a stimulus
● Stimulus
● Sensory receptor detects stimulus
● Sensory receptor sends impulses along sensory neurone to CNS
● CNS coordinates response
● CNS sends information to effector along motor neurone
● Effector produces a response to the stimulus
What is a synapse?
A small gap between neurones across
which a nerve impulse is transmitted via
neurotransmitters
How are nerve impulses transmitted
across a synapse?
● Nerve impulse reaches presynaptic neurone
● This triggers the release of neurotransmitters
● Neurotransmitters diffuse across the synapse
● They bind to receptors on the postsynaptic neurone
● This stimulates an impulse in the postsynaptic neurone
Why do synapses slow down the transmission of nerve impulses?
It takes time for the neurotransmitters to
diffuse across the synapse and bind to receptors on the postsynaptic neurone.
What is a reflex?
● Automatic response to a stimulus by the body
● Involuntary - does not involve conscious part of the brain
● Protective mechanism e.g. a withdrawal reflex is initiated when a hot object is touched to prevent burns
Describe the reflex arc
stimulus → sensory receptor → sensory neurone → relay neurone → motor neurone → effector → response
