The Nervous System Flashcards
What are the functions of the nervous system?
Sensory- input- gathering information to monitor changes (stimuli) occurring inside and outside the body
Integration to process and interpret sensory input and decide if action is needed
Motor- response- initiate action (voluntary and/or involuntary)
What does the nervous system do?
Regulates and controls all body activity. It works with the endocrine system to maintain homeostasis
What are the two types of nervous system?
Central Nervous System (CNS)- brain and spinal cord
Peripheral Nervous System (PNS)- all nerves outside the CNS
What is a nerve?
A bundle of hundreds to thousands of axons associated with connective tissue and blood vessels
Each nerve has sensory (afferent) and motor (efferent) fibres (neurones)
Each nerve serves a specific region of the body
What is a neurone?
A single nerve cell
Specialised cells to transmit messages
Major regions of neurones
Cell body- nucleus and metabolic centre of the cell
Processes outside the body- fibres that extend from the cell body (axons and dendrites)
Axons conduct impulses (electrical transmission) away from the cell body
Dendrites conduct impulses towards the cell body
Describe the structure of Neurones
Cell body- containing nucleus and organelles
Axons end in axon terminals
Axon terminals contain vesicles containing neurotransmitters
Axon terminals are separated from the next neurone/cell by a gap called the synapse (junction between nerves)
Schwann cells cover some axons (myelinated neurones)
Between Schwann cells are gaps- nodes of Ranvier (NoR)
What is an action potential?
An electrical signal that is transmitted along the axon. The action potential hops from 1 NoR to the next
Where are neurotransmitters made?
Made in the cell body but stored in the axon terminals
How do neurones communicate with other cells?
Chemically:
Chemical messengers known as neurotransmitters are stored in the ‘axon terminals’
When stimulated by an action potential, neurotransmitters are released into the synapse
They diffuse across the synapse then attach to a receptor on the adjacent cell (post synaptic cell)
They then either stimulate or inhibit the post synaptic cell
Describe the features of motor neurones
Have cell body at one end and lots of processes (dendrites and axon) leaving the cell body (multi-polar)
They carry impulse from CNS to peripheral (to effectors)
Describe the features of sensory neurones
Have cell body on axon, only one process leaving the cell body (axon)
Carry impulse from peripheral to CNS. e.g. information about pain and temperature
What are receptors?
Usually proteins to which chemical messengers such as neurotransmitters bind to on the surface of the ‘target’ cell (cell they want to affect)
Once the chemical has bound it can change activity within the cell
Describe the effect of the neurotransmitter noradrenaline
Noradrenaline is a neurotransmitter released by the sympathetic nervous system that can bind to the SA node, causing an increase in heart rate
What are neuroglia?
Support cells within the CNS
Support, insulate, nourish and protect neurones, also form the ‘blood brain barrier’
For example, Schwann cells which form the myelin sheath in the PNS
Describe the features of the CNS
The brain (containing millions of neurons) and the spinal cord (neurones convey impulses towards and away from the brain)
The CNS is protected by the skull (brain) and vertebral column (spinal cord)
Also has a covering of connective tissue which protects and supports
What are the meninges?
Three connective tissue membranes that cover and protect the CNS