Nervous System + Spinal Cord Flashcards
Peripheral Nervous System
general components
Distributed throughout the rest of the body: Visceral organs, muscles, skin, bones
Afferent + efferent neurons, few interneurons
Nerves (have blood vessels and CT)
Ganglia
Nerves definition
Bundles of myelinated axon that carries signals between the PNS + CNS that have blood vessels + dense irregular connective tissue.
Nerves Connective Tissues
- Endoneurium: connective tissue around myelin of a single sheath
- Fascicles: bundle of many axons, nerve makes up many fascicles
- Perineurium: around a fascicle
- Epineurium: around a whole nerve
Spinal nerves - general
- Come out of the spinal cord
- Pairs come out between each pair of vertebrae: 1 to the left + 1 to the right
Cranial nerves
general
- 12 numbered nerves that come out of the brain
- Most come out of the brain stem
- Most go to the head
Ganglia
Clusters of soma of neurons in PNS
Sometimes many synapses
Some have no synapses
3 Branches of the PNS
- Afferent: sensory neurons
- Efferent Nervous System: carries signals out of the CNS that control other parts of the body.
- Enteric Nervous System: Nervous system around the digestive tract controls the glands and smooth muscle, receives sensory signals from the tract, and communicates with the CNS through the efferent + afferent nervous system.
Afferent Nervous System
breakdown
- Gathers info + sends it back to the CNS
- Special Senses: senses with special sensory organs
- Sight, hearing, smell, taste, balance - Somatic Senses: senses of the body
- Of the skin, muscles, + joints - pressure, temp, pain - Visceral Senses: sense of visceral organs + body fluids
- Heart, digestive, reproductive, etc.
- Blood
- Not entirely consciously aware
Efferent Nervous System
definition & components
Definition: Carries signals out of the CNS that control other parts of the body
Associated systems: Autonomic Nervous System & Enteric Nervous System
Somatic Nervous System
Part of the efferent nervous system that controls skeletal muscle.
- Composed of somatic motor neurons + units
- Voluntary
- Controlled by the cerebral cortex - the conscious part of the brain
Autonomic Nervous System:
Part of the efferent nervous system that controls smooth muscle, cardiac muscle, glands, adipose.
- Involuntarily controlled by the hypothalamus
- Sympathetic: “fight or flight” - gets the body ready for action
- Parasympathetic: “rest + digest” - stimulates normal metabolism of the body, works the opposite of the sympathetic
Enteric Nervous System
Part of the efferent nervous system around the digestive tract that controls the glands and smooth muscle, receives sensory signals from the tract, and communicates with the CNS through the efferent + afferent nervous system.
Can act independently of the rest of the nervous system because it has its own interneurons.
Central Nervous System
(CNS) general components
- Located in the dorsal body cavity + inside bones: Spinal cord - in vertebrae, Brain - cranial bones
- Surrounded by meninges = connective tissue membrane that protects the CNS
- Bathes in cerebrospinal fluid
- Lots of interneurons
- Primary information processor of the body
- white & grey matter
White Matter
Fat from the myelinated axons gives it its color that carries info between different parts of the CNS.
In the spinal cord- grey on the outside + white matter around it
In the brain- grey on the outside + inside with white matter in between
Grey Matter
Have lots of synapses for information processing. The cell bodies and unmyelinated axons give it its color.
In the spinal cord- grey on the outside + white matter around it
In the brain- grey on the outside + inside with white matter in between
Spinal cord
Located in the spinal cavity and passes through the vertebral foramen of vertebrae.
Carries signals up to and down from the brain.
Controls many reflexes
Does some information processing
Spinal Nerves
31 pairs of nerves that come out of the spinal cord between vertebrae and most have the same thickness all the way down.
For each pair - 1L + 1R
Efferent + afferent signals
Named after the vertebrae they emerge from
Superiorly - starts just below the skull, vertebral foramen, + medulla
Inferiorily- goes down to between the 1st + 2nd lumbar vertebrae L1 + L2 (don’t go all the way down the spine)
2 enlargements: Cervical (where the nerves for arms come out) + Lumbar (where the nerves for legs come out)
Cervical enlargement
Where the nerves for arms emerge from the spinal cord.
Lumbar enlargement
Where the nerves for the legs emerge from the spinal cord.
Conus Medulla
Cone = point
Where the bottom of the spinal cord comes to a point
Cauda Equina
= horses tail
Spinal cord ends at the top of the lumbar within the vertebral foramen to the places they will emerge from the spine
Spinal cord cross-section
Each spinal nerve emerges from the spinal cord as 2 roots
1. Dorsal root
2. Ventral root
The roots come together to form a spinal nerve
Dorsal root
- Carries afferent signals
- Has axons of sensory neurons
- Has Dorsal Root Ganglion (ganglia of the root)
Dorsal Root Ganglion
Ganglion on the dorsal root
- Cell bodies of afferent neurons
- All pseudo unipolar
- No synapses
General rule - dorsal = afferent, sensory, up to the brain
Ventral Root
Carries efferent signals to autonomic + somatic nervous systems.
Has axons of efferent neurons.
General rule - ventral = efferent, motor, down from the brain
Horn
Bump in the grey matter of spinal cords.
Dorsal horn
Bump in spinal cord grey matter that has cell bodies of interneurons.
Afferent neurons on dorsal root synapse on interneurons in dorsal horn.
General rule - dorsal = afferent, sensory, up to the brain
Ventral horn
Bump in spinal cord grey matter that has cell bodies of somatic efferent neurons that are all multipolar
* Axons of efferent neurons and Somatic motor neurons exit the spinal cord on the ventral root
* Receives signals from interneurons + sometimes from afferent neurons
General rule - ventral = efferent, motor, down from the brain
Lateral horn
Bump in spinal cord grey matter that has cell bodies of autonomic efferent neurons.
Exit the spinal cord on ventral root.
Ascending white matter tracts
Myelinated axons carrying signals up to the brain that tend to be dorsal
Descending white matter tracts
myelinated axons carrying signals down from the brain that tend to be ventral
Cerebrospinal Fluid (CSF)
- Surrounds the CNS
- Is within meninges
- Supports the weight of the brain
- Protects the brain from impact
- Circulates through the brain + spinal cord: Delivers gasses + nutrients to brain cells, Removes waste
- Similar to blood in terms of chemical content: Not identical + More stable than blood
Choroid plexus
On the root of each ventricle to produce CSF
How: Capillary surrounded by ependymal cells
- Fluid in blood moves out of capillary to become CSF
- Ependymal cells are able to pass from blood into CSF - Controling the content of CSF
Where does CSF circulate through?
- Ventricles + central canal in the middle of CNS
- Subamchroid space - outside CSN
Movement is driven by the beating of cilia on the ependymal cells
CSF made in choroid processes
Lateral ventricles (Where CSF starts, L + R, surrounded by cerebrum) → Internventricular foreman → 3rd ventricle (Thin space between 2 halves of the thalamus) → Cerebral aqueduct → 4th ventricle - posterior pons → Into subarachnoid space (moves towards transverse fissure from cerebellum) OR Down central canal of the spinal cord (Will pass into subarachnoid space in the spinal cord) → dural venous sinuses → return to blood
