Unit 3.8 - The nervous system Flashcards
What kind of animals have nervous coordination?
Only higher animals (e.g - mammals) have developed it
Purpose of the nervous system
To respond to changes in the external or internal environment, and do something to respond to these changes
Name for the things we respond to with the nervous system
Stimuli
(Singular = stimulus)
How would the nervous system act when the sun comes through the window?
Receptor cells in the retina in the eyes convert the signal into an electrical signal that’s transmitted to the brain = react
What does the nervous system allow us to do?
Respond to changes in our environment
Stimulus
Any detectable change in the internal or external environment of the organism
What do receptor cells act as and how?
Transducers
They detect energy in one form and convert it into electrical energy
what act as transducers in the nervous system?
Specialised receptor cells
How does electrical energy travel along neurones?
As a nerve impulse
What is a nerve impulse?
Electrical energy travelling along neurones
Neurones
Nerve cells
What do nerve impulses do?
Initiate a response in an effector
What is an effector?
A muscle or a gland
What do muscles and glands do as part of the nervous system?
Act as effectors
What are the 2 main parts of the nervous system?
The central nervous system (CNS)
The peripheral nervous system (PNS)
What is the central nervous system composed of?
The brain and spinal cord
What does the central nervous system do?
Processes information provided by a stimulus and coordinates a response
What is the peripheral nervous system made up of?
Neurones (nerve cells)
Which part of the nervous system then has two further parts?
The peripheral nervous system
2 parts of the peripheral nervous system
The somatic nervous system
The autonomic nervous system
The somatic nervous system:
What is it made up of?
What do these do?
Made up of pairs of nerves branching from the brain and spinal cord
These neurones carry impulses from receptor cells to the CNS and then from the CNS to the effectors
What does the autonomic nervous system do?
Provides unconscious control of the internal organs (e.g -heartbeat and breathing)
Which part of the peripheral nervous system is made up of pairs of nerves branching from the brain and spinal cord?
The somatic nervous system
Which part of the nervous system is composed of the brain and spinal cord?
The central nervous system
Which part of the peripheral nervous system provides unconscious control of the internal organ?
The autonomic nervous system
What is the nervous system made up of?
Neurones
What type of neurone is the one we have a detailed labelled diagram of?
A motor neurone
Which part of neurones contains the nucleus and most organelles?
The cell body
What does the cell body of a neurone contain?
The nucleus and most organelles
What come from the cell body of a neurone?
Many extensions
Names for the extensions from the cell body of a neurone
Many extensions - dendrites
1 long extension - axon
What do the dendrites of a neurone do?
Conduct nerve impulses towards the cell body
What does the axon of a neurone do?
Conducts nerve impulses away from the cell body towards the axonal terminals
Name for the ends of the axonal terminals
Synaptic end bulbs
What happens at the synaptic end bulbs of the neurone?
Where the neurone connects to another neurone or a muscle or a gland (effector)
What do Schwann cells form?
Form the myelin sheath
What form the myelin sheath?
Schwann cells
Describe Schwann cells
Wrapped around along the axon many times in several layers
What are Schwann cells wrapped around many times in several layers?
The axon
Purpose of Schwann cells wrapping around the axon many times in several layers
Provide a form of electrical insulation for the axon
Why do Shwann cells need to provide a form of electrical insulation for the axon of a neurone?
The electrical insulation increases the speed of nerve impulses along the axon
Do Shwann cells form a complete sheath?
No
Gaps between Shwann cells
Nodes of Ranvier
Why are nodes of Ranvier important?
Important in the way in which the nerve impulse propagates along the axon
Describe neurones
Highly specialised cells which carry nerve impulses in one direction
How are nerve impulses carried?
In one direction by neurones
Three main types of neurones in a vertebrate
Sensory
Relay
Motor
What do sensory neurones do?
Carry nerve impulses from the receptor cells in the sense organ to the CNS
What do relay neurones do?
Connect the sensory and motor neurones
Where are relay neurones found?
In the CNS
What do motor neurones do?
Transport nerve impulses from the CNS to the effectors (muscles and glands)
Where are sensory, relay and motor neurones found?
In both the somatic and central nervous systems
Another word for Shwann cells
Myelin sheath
What does the plasma membrane of a Shwann cell do?
Provides electrical insulation to the axon
Describe the plasma membrane of Shwann cels
Layers of membrane
Where is axoplasm in Shwann cells and what does it do?
Inside the axon
Contains organelles (e.g - mitochondria)
What is the plasma membrane of Shwann cells made up of?
Phospholipids
Why is the plasma membrane of Shwann cells a good electrical insulator?
Phospholipids contain non-polar fatty acid tails, making the membrane a good electrical insulator (non-polar)
Between the membranes of Shwann cells
Myelin
What does myelin do in Shwann cells?
Is a fatty substance that also acts as an electrical insulator
Reflex arc
A mechanism that controls a reflex
Describe the features of reflex responses
Unconscious (doesn’t go through the brain)
Innate (present in an individual from birth + not learnt)
Protects us from injury
Rapid, automatic, beneficial
How come reflex responses are unconscious?
Don’t go through the brain
What does it mean that reflex responses are innate?
Present in an individual from birth and not learnt
Give 2 examples of reflex reponses
Hand moving away from a hot surface
Blink response when something approaches your eye
What’s the purpose of the gaps between the vertebrae of the spinal cord?
Allow spinal nerves to branch off from the spinal cord and branch into the various parts of the body
How many neurones make up the branches from the spinal nerves?
Thousands
What do reflex responses rely on?
The 3 types of neurones previously mentioned
What’s the name for the region at the back of the spinal cord?
Dorsal region
What’s the name for the region at the front of the spinal cord?
Ventral region
Dorsal region of the spinal cord
Back of the spinal cord
Ventral region of the spinal cord
Front of the spinal cord
What are all of the different features that the transmission of a nerve impulse along a three-neurone reflex arc involves?
Stimulus
Receptor
Sensory neurone
Relay neurone (in CNS)
Motor neurone
Effector
Response
Explain exactly how a nerve impulse is transmitted along a three-neurone reflex arc
Stimulus
Receptor that initiates a nerve impulse to travel along the…
Sensory neurone. The axon of the sensory neurone enters the spinal cord via the dorsal root. It first enters the dorsal root ganglion, which is where the cell body of the sensory neurone is.
The axon of the sensory neurone then continues to the grey matter, where it forms a synapse with the…
Relay neurone (in CNS). The replay neurone then forms a synapse with the…
Motor neurone, which carries the nerve impulse to the…
Effector to give a response
Example of a receptor involves in a reflex response
Temperature receptors in the skin
What initiates the nerve impulse that travels along the sensory neurone?
Receptors
How does the axon of the sensory neurone enter the spinal cord?
Via the dorsal root
Where is the cell body of the sensory neurone?
The dorsal root ganglion
What is in the dorsal root ganglion?
The cell body of the sensory neurone
Where does the sensory neurone form a synapse with the relay neurone?
In the grey matter