Introduction to the nervous system Flashcards
What is the nervous system?
The nervous system coordinates voluntary and involuntary actions and transmits signals between different parts of the body.
Divided in two ways - anatomically or functionally
Anatomically - The central nervous system (CNS) and peripheral nervous system (PNS)
Functionally - The somatic nervous system and the autonomic nervous system
What is the central nervous system?
The central nervous is the brain, the brain stem and the spinal cord.
Responsible for integrating, processing and coordinating sensory data and motor command.
Also responsible for higher functions such as intelligence, memory, learning and emotions.
What is the peripheral nervous system?
Peripheral nervous system contains all of the neural tissue except the brain, the brain stem and the spinal cord.
Delivers sensory information to the CNS.
Carries motor demands to the peripheral tissues and systems.
Functionally divided into afferent and efferent.
Nerve Components
The individual axons within a nerve can have different functions to each other.
For example a peripheral nerve may have sensory nerve cells and motor nerve cells (fibres).
These fibres will also be carrying out individual functions - for example some motor fibres will be travelling to skeletal muscle some will be travelling to blood vessels (vasoconstriction).
Afferent vs Efferent
Afferent = sensory nerve fibres - for example impulses pass from the skin to the CNS.
Efferent = motor nerve fibres - for example impulses pass from CNS to active skeletal muscles.
The Spinal Cord
Vertebrae makes up the spinal cord. Vertebrae contain the vertebral foramen which stacked up has a canal where the spinal cord is safely located. Spinal nerve emerges from the spinal cord.
Spinal Nerves
7 Cervical vertebrae/ 8 cervical nerves
12 Thoracic vertebrae/nerves
5 Lumbar vertebrae/nerves
5 Sacral vertebrae/nerves
3/4 Coccyx vertebrae/nerves
Dermatomes and Myotomes
Dermatome is defined as the area of skin supplied by a single spinal nerve.
Myotomes - defined as the area of muscle supplied by a single spinal nerve. Complicated as segments might join together or break up so myotomes change the amount of muscle it is connected too.
Cranial Nerve
Olfactory - sensory for smell
Optic - sensory for sight
Oculomotor - motor for eye movement, pupil size and lens
Trochlear - motor for eye movement
Trigeminal - mixed component for sensory to face, muscles of mastication
Abducent - motor for eye movement
Facial - mixed components for taste, muscles of facial expression, salivary gland secretion
Vestibulocochlear - sensory for balance and hearing
Glossopharyngeal - mixed for taste, monitors blood pressure and gases, swallowing and salivary gland secretion
Vagus - mixed for taste, sensory, movement and secretion to abdominal and thoracic viscera
Accessory - motor for movement of neck
Hypoglossal - movement of tongue.
Nerve Plexuses
Plexuses means network. There are three plexuses: Cervical, brachial and lumbar. Cervical plexus from ventral rami.
Brachial Plexus contains MANY nerves (Hundreds of thousands of nerve cells) where ventral rami joins together (also definition of plexuses).
Radial nerve has root value from C5 to T1 as it has neurones/fibres from all five levels.
Autonomic Nervous system
Unconscious control
Is itself divided into the sympathetic nervous system and parasympathetic nervous system
Sympathetic - ‘fight or flight’ response. For example increases heart rate and respiratory rate, diverts blood to muscles, dilates pupils etc.
Parasympathetic - ‘rest and digests’. Usually the opposite to above, increase salivation, increases rate of digestion.
Ganglion is a collection of cell bodies. There is a pre-ganglion and post-ganglion.
Sympathetic Nervous System
Sympathetic nerves comes out between T1 and L2 coming out of the ventral root. There is something called the sympathetic chain. The sympathetic neurones will synapse the chain and travel up and down to go where they need to go (way more complicated than this but it’s the general principle).
This nervous system is very wide spread as it supplies organs and the skin (moves hear such as arrector pilli).
Enteric nervous System
Can act autonomously - described as the second brain
Controls peristalsis
Has input from sympathetic and parasympathetic divisions of the autonomic nervous system
