sistemul nervos Flashcards
When did people begin to think that the brain was important?
In the 1800s. Before that people used to chuck away the brain. They thought the heart was more important and that the brain was involved in thermoregulation.
What did Luigi Galvani do?
He put electrical current through a frog’s leg and made the legs twitch.
Thus discovering the electrical basis of nerves.
What did Helmholtz do?
He measured the speed of nerve conduction.
What did Ramon y Cajal do?
Described how nerve cells communicate
History of MRI
1947 - first discovered
1977 - first clinical images
1982 - first brain MRI
1990s - commonly used in the UK
What are the sub-divisions of the nervous system>
Central nervous system and peripheral nervous system
What are the sub-divisions of the central nervous system
Brain and spinal cord
what are the sub-divisions of peripheral nervous system
somatic and autonomic nervous system
what are the sub-divisions of the autonomic nervous system
sympathetic and parasympathetic
Roles of the brain and spinal cord
The brain receives and processes sensory information and then initiates appropriate responses
The spinal cord is the principal route for this information to and from the brain
How are the brain and spinal cord protected?
The brain and spinal cord are highly protected:
- encased in bone (skull and vertebrae)
- surrounded by meninges (3 membranes that line the skull and vertebral canal)
- cerebrospinal fluid (CSF)
Brain is guarded from chemical invasion by the blood brain barrier (BBB)
How is the spinal cord protected?
The spinal cord is encased by the vertebral column, which provides protection.
It is the main pathway for information between the brain and the peripheral nervous system.
What is grey and white matter?
In the brain: grey matter is outer layer, white matter is inner layer
In the spinal cord: grey matter is inner layer, white matter is outer layer
Grey matter consists of densely packed neuronal cell bodies and other cells.
White matter contains mainly myelinated axons that allow communications between cells.
What are meninges?
In the CNS, there are 3 protective layers that surround the brain and spinal cord.
- Dura mater: thick, flexible, unstretchable
- Arachnoid membrane: middle, below dura. soft
- Pia mater: lower and delicate closely attached to the brain and spinal cord
In the PNS there are only 2 layers: dura and pia mater
What is the cerebral spinal fluid
A clear fluid which helps protect the brain and spinal cord from damage.
Removes waste products.
Acts as a cushion
Provides hormones and nutrition
Where is cerebral spinal fluid found in the CNS?
Subarachnoid space: the gap between the arachnoid membrane and the pia mater
Ventricles: hollow, interconnected chambers within the brain
Central canal: of the spinal cord
CSF is secreted within the ventricles
What is the BBB?
The BBB is a barrier of capillaries without gaps between the blood and the brain
BBB helps regulate the composition of the fluid which surrounds neurones, important for synaptic transmission and brain function
It allows certain substances in and only certain substances out
Is BBB consistent throughout the brain>
No. A weak spot is at area postrema in the medulla.
Area postrema controls vomiting.
Neurones in the area postrema can detect toxins, and vomiting can be initiated.
What does the PNS consist of?
Nerves (cable-like bundles of axons) and ganglia (clusters of cell bodies) that are outside of the CNS.
These connect the CNS to the limbs and organs
There are 12 pairs of cranial nerves in the brain that establish connections in the head and upper body
There are 31 pairs of spinal nerves that do the same for the rest of the body.
What do cranial nerves do?
Mostly involved with motor and sensory functions of the head and neck.
Vagus nerve: regulates functions of internal organs located in thoracic and abdominal cavities e.g. heart and intestines
What do spinal nerves do?
The Bell-Magendie Law states that the spinal cord contains:
Descending motor information (efferent signals carried away from the CNS via the ventral root to muscle or glands)
Ascending somatosensory information (afferent signals carried toward the CNS via the dorsal root)
What does the PNS do?
The CNS receives information from the PNS, which senses signals from outside of the body (somatic) and from inside the body (autonomic)
What is the sympathetic and parasympathetic?
Symp: Fight or flight
Parasymp: rest and digest
