Anatomy of the somatic nervous system Flashcards
The Somatic Nervous System
A unique collection of tissues under the direct command of the human organism- it is the voluntary division of the nervous system. It is used to accurately localise sensations around the body and gives us an awareness of our body in 3D space (proprioception).
Anatomical organisation of the nervous system
- central nervous system (CNS); brain and spinal cord
- peripheral nervous system (PNS); cranial nerve, spinal nerve etc.
Directional organisation of the nervous system
- afferent/sensory portion (input); senses a stimulus, signals towards the CNS
- efferent/motor portion (output); effects a response, signals away from the CNS
Functional organisation of the nervous system
- somatic (voluntary) nervous system; responds to external changes
- autonomic (involuntary) nervous system; responds to internal changes, important for homestasis, can be divided into sympathetic, parasympathetic and enteric
The Peripheral Nervous System
- connects the sensory portion to the CNS
- CNS integrates the information
- connects the CNS to target organs
Parts of the PNS
- 31 spinal nerve pairs
- 12 cranial nerve pairs
- ganglia (autonomic/sensory)
- nerve plexuses (brachial/lumbar/sacral)
- enteric nervous system
Components of the nervous system
- neurones (nerve cells)
- glia (supporting cells)
The neurone
The nerve cell responsible for conducting impulses.
Parts of a neurone
- soma (cell body)
- axon
- dendrites
- terminals
- organelles (nucleus, mitochondria, ER, golgi, ribosomes etc.)
3 main types of neurones
- multipolar; motor/efferent
- bipolar; relay or special sense
- pseudo-unipolar; sensory/afferent
Glial cells
Supporting cells which occupy and interact with neurones.
Types of glia
- ependymal cells
- astrocytes
- microglia
- oligodendrocytes
- Schwann cells
Myelination
Myelin is a lipid sheath 0.5-2.5 micrometer thick, created by glial cells (oligodendrocytes in CNS, Schwann cells in PNS) which surrounds the axon of a neurone. It increases the speed of conduction, provides protection and structural support.
Afferent division
Sensory portion (input) of the nervous system, transmits stimuli detected by the skin or special sense organs of the PNS to be processed by the CNS.
Efferent division
Motor portion (output) of the nervous system, transmits signals from the brain to effect a response.
