nervous system Flashcards
components of CNS vs PNS
Central nervous system- brain and the spinal cord
Peripheral nervous system- nerves and structures that connect the CNS to all parts of the body
SNS vs ANS
Somatic nervous system- refers to that part of the nervous system that predominantly regulates muscular function
Autonomic nervous system- refers to that part of the nervous system that regulates visceral and some special functions
what can the ANS be further divided into?
sympathetic and parasympathetic nervous systems
what are the functions of the NS mediated by?
different types of cells present within the brain and spinal cord and other structures such as ganglia
what are the two types of NS cells ?
neurons
glial cells
how do neurons communicate?
synapses
describe the basic functional unit of a neuron
contains a cell body with a nucleus – called ‘perikaryon’
what are the two process of neurons?
dendrite and axon
describe dendrite
- Transmits impulses towards the cell body
- Generally, there are multiple dendrites
describe the axon
- Transmits impulses away from the cell body
- Always originates as a single process from the cell body
- May divide in multiple processes after
travelling a distance from its origin
what are the three types of neurons based on its process and define them
Unipolar (Pseudounipolar):
The dendrite and axon come together to form a single process to the cell body. These neurons are also called ‘pseudounipolar’.
Bipolar:
The dendrites join together to form a common trunk before they reach the cell body at a site that is different from that of the origin of the axon.
Multipolar:
A number of dendrites join the cell body at different points. Most neurons are multipolar.
how do neurons communicate with each other?
through the formation of synapses and they transmit information in the form of action potentials.
what are synapses?
communication between one neuronal membrane to another
how does communication via synapses occur?
through the transmission of signals which could be either electrical or chemical in nature
define axosomatic
connection between an axon of one neuron and a cell body of another neuron
define axodendritic
connection between an axon of one neuron and a dendrite of another neuron
define axoaxonic
between an axon of one neuron and an axon of another neuron
what is the difference between nuclei and ganglia?
nuclei- Neuronal aggregations in the brain
ganglia- aggregations of cell bodies in the peripheral nerves
what are glia and the 3 types?
- provide nutrition to neurons and help with ‘neurotransmission’.
- do not directly participate in neurotransmission.
- produce myelin which surrounds nerve fibers and provide insulation, protection and support
- 3 types: astrocytes, oligodendrocytes, microglia
describe astrocytes
- star-shaped
- found in the brain and spinal cord
- histologically identified by the presence of a protein called ‘glial fibrillary acidic protein (GFAP)’
- ## involved in various functions that are critical for CNS function: metabolic support for neurons, maintenance of blood-brain barrier, repair of injury to the nervous system, regulating ion concentrations, etc.
describe oligodendrocytes
provide support to axons of the CNS by producing myelin sheath.
describe microglia
- cells of immune origin and are very critical for the immune defence mechanism of the CNS
- several types have the ability to undergo changes in their structure to enable them to participate in immune functions in the CNS.
what is the spinal cord?
- cylindrical structure that runs between the hindbrain to the lumbar vertebrae
what are the fibre tracts (which matter) of the spinal cord?
- white matter
- carry information to and from the brain
what are cell bodies (which matter) of the spinal cord?
- grey matter
- either interneurons or motor neurons that give rise to motor fibres
___________(dorsal and ventral) emerge from the spinal cord on each side and merge to form the spinal nerves
nerve roots
what fibres do the spinal nerves contain?
sensory and motor
where are sensory neurons (cell bodies) for the spinal cord located?
dorsal root ganglion
describe the process of how the spinal cord and its nerves provide innervation to muscles
- sensory neurons located in dorsal root ganglion
- dendrites carry the sensory information from the periphery to the cell body and then through the axons (dorsal root) towards the dorsal horn of the spinal cord (afferent – towards the spinal cord)
- Motor neurons are typically located in the ventral horn of the spinal cord and their axons travel through the ventral root (efferent – away from the spinal cord) and join the dorsal roots to form the spinal nerve
- spinal nerve exits through the intervertebral foramen, and splits into dorsal and ventral branches and provides innervation to muscles.
what segments are the spinal cord divided into?
Cervical, Thoracic, Lumbar, Sacral, and Caudal
name and describe the two enlargements along the length of the spinal cord
i) cervicothoracic area (between last three or four cervical spinal cord segments and first two or three thoracic segments)
ii) lumbosacral area (between last three lumbar spinal cord segments and first two sacral segments)
what does the cervicothoracic area and lumbosacral area give rise to?
brachial and lumbosacral plexus
what is the difference between the brachial and lumbosacral plexus?
- brachial plexus gives rise to nerves that innervate the forelimb
- lumbosacral plexus gives rise to nerves that innervate the hind limb
what are the gross divisions of the brain?
- hindbrain (rhombencephalon = Metencephalon “pons”+ Myelencephalon “medulla oblongata”) (metencephalon “cerebellum”)
- midbrain (Mesencephalon)
- forebrain (Diencephalon+Telencephalon)