Anatomy of the Nervous System Flashcards
What are the two divisions of the nervous system?
The central nervous system and the peripheral nervous system
Central Nervous System
Brain and spinal cord
Peripheral Nervous System
Somatic nervous system and autonomic nervous system
Autonomic Nervous System
Sympathetic and parasympathetic
Somatic Division of the PNS
Voluntary
Afferent nerves bring information to the CNS
Efferent nerves carry information out of the CNS
Autonomic Division of the PNS
Involuntary
Afferent nerves provide information about the state of organs
Efferent nerves are parasympathetic or sympathetic which oppose each other
-flight/fight/freeze vs relaxation
What region of the CNS do sympathetic efferents come from?
The thoracolumbar region
What region of the CNS do parasympathetic efferents come from?
The craniosacral region
Where are sympathetic ganglia located?
Close to the spinal cord in a chain
Where are the parasympathetic ganglia located?
Close to the target organs
What is the length of sympathetic postganglionic fibres?
Long
What is the length of parasympathetic postganglionic fibres?
Short
How much postganglionic branching is there? (sympathetic)
Lots so that multiple organs can be mobilized at once
How much postganglionic branching is there? (parasympathetic)
Very little branching
Cranial Nerves
12 pairs of nerves in the periphery that originate on the ventral surface of the brain instead of the spinal cord
Purely sensory
Olfactory (I) Sensory
Nose
Optic (II) Sensory
Eye
Oculomotor (III) Motor
All eye muscles except those supplied by IV and VI
Trochlear (IV) Motor
Superior oblique muscle
Trigeminal (V) Sensory
Face, sinuses, teeth
Trigeminal (V) Motor
Muscles of mastication
Abducent (VI) Motor
External rectus muscle
Facial (VII) Motor
Muscles of the face
Vestibulocochlear (VIII) Sensory
Inner ear
Glossopharyngeal (IX)
Pharyngeal musculature
Vagus (X) Motor
Heart, lungs, bronchi, GIT
Vagus (X) Sensory
Heat, lungs, bronchi, trachea, larynx, pharynx, GIT, external ear
Accessory (XI) Motor
Sternocleidomastoid and trapezius muscles
Protection for the CNS
Meniges
Cerebrospinal fluid (cushion)
Blood brain barrier
Encased in bone
What are the layers of the meninges?
Dura mater
Arachnoid mater
Pia mater
Dura Mater
Epidural (between the skull and dura)
Tough outer layer
Restricts movement within the skull
Sinuses that drain deoxygenated blood and CSF fluid
Arachnoid Mater
Collagenous and weblike
Pia Mater
Adheres to the surface of the CNS
Encloses CSF
Where the blood vessels are found
What makes cerebral spinal fluid?
Ependymal cells
Where is the cerebral spinal fluid found?
Ventricles and central canal
How is waste removed from the CSF?
It removes toxic byproducts by having the CSF absorb into the subdural sinus and from there drain into the jugular vein
The Function of the CSF
Supports and cushions the brain
Shock absorption
Central Canal
Channel runs length of the spinal cord
Ventricles
Produce and circulate CSF in the brain
Interconnected by a series of openings
Single reservoir
The Chambers of the Ventricles
2 later
3rd
4th
The Function of the Blood-Brain Barrier
Keeps CNS electrochemically separated from the PNS
Keeps molecules outside of the brain
-lipid soluble materials don’t need a transporter (usually)
What is the BBB made out of?
Tightly packed cells surrounding blood vessels epithelial and glial cells
How are Psychoactive Effects Limited by the BBB?
For there to be significant psychoactive effects, the molecule in question need to have high lipid solubility
Ways to Break Down the BBB
High blood pressure Not completely formed at birth High concentration of non-permeable molecules Brain injury or disease Infection Microwaves and radiation
The Brain’s Blood Supply
Carotid and vertebrobasilar system form anastomosis in the Circle of Willis
What are Neurons?
Specialized cells for electrochemical signals
- reception
- conduction
- transmission
Dendrites
Receive synaptic contacts from other neurons
Axon Hillock
The cone-shaped region at the junction between the axon and the cell body
Cell Body
The metabolic center of the neuron
Myelin
Fatty insulation around many axons
Axon
Transmits an action potential
Nodes of Ranvier
The gaps between section of myelin
Buttons
Release chemicals into synapses
Presynaptic Density
Vesicular release machinery
Postsynaptic Density
Receptor signalling machinery
Unipolar Neuron
Found in PNS
Bipolar Neuron
Found in retinas
Multipolar Neuron
Found in CNS
Multipolar interneuron
No axon, does not transmit signal far
Nerve Fiber
Nerve process (axon or dendrite)
Nerve
Bundle of nerve fibres in the PNS
Tract
Bundle of nerve fibres in the CNS
Ganglion
Cluster of neuronal cell bodies in PNS
Nucleus
Cluster of neuronal cell bodies in CNS
Glia vs Neurons
Glia do not form synapses
They are less excitable than neurons
Their processes are not differentiated
They can divide
Types of Glia
Astrocytes
Microglia
Oligodendrocytes
Schwann Cells
Astrocytes
Star-shaped, largest glial cell Clean up neurotransmitters Hold neurons in place and rearrange synapses Regulate ions in extracellular space Wrap around capillaries -form BBB Important in cognition
Microglia
Really small Macrophage Multiply in response to injury or disease Active immune response Fast acting Synaptic plasticity Sensitive to changes in potassium ions
Oligodendrocytes
Only CNS
Forms myelin sheath
Schwann Cells
Only PNS
each cell creates only one myelinated axon segment
guide axon regeneration in PNS
Anterior
Nose or front
Posterior
Tail or back
Dorsal
Top of the head
Ventral
Bottom of the head
Medial
Midline
Lateral
Away from the middle
Axial Plane
Look at the brain starting at the chin to the top of the head
Ventral to dorsal
Sagittal Plane
Look at the brain from the side starting from one ear to the other
Lateral to medial
Coronal Plane
Look at the brain starting at the back of the head moving towards the face
Posterior to anterior
What is the spinal cord?
Link brain to body and body to brain
How many regions does the spinal cord have?
4 Cervical Thoracic Lumbar Sacral
Where is the major site of injury in the CNS?
The spinal cord
Location of the injury will determine which functions are lost
What is the dorsal root of the spinal cord?
Sensory information from afferents come through the dorsal root
Axon terminals in the root
Unipolar neurons
What is the ventral root of the spinal cord?
Motor information from efferents leaves through the ventral root
Dendrites in the root
Multipolar neurons
Where is white matter located in the spinal cord?
In the periphery
Myelinated axons
Where is grey matter located in the spinal cord?
In the middle
- cell bodies
- unmyelinated
- butterfly or H-shaped
Where is CSF located in the spinal cord?
The central canal
How does the amount of white and grey matter vary by region?
The lower regions are greyer and the higher regions are more white
What are the 5 divisions of the brain?
Telencephalon Diencephalon Mesencephalon Metencephalon Myelencephalon
What are the 3 swellings of the brain?
Fore -tele and di Mid Hind -met and myel
What is the myelencephalon composed of?
Most posterior - in the hindbrain The medulla -ascending and descending tracts at the core -cranial nerve nuclei Origin of the reticular formation
What is reticular formation?
Core network of 100 nuclei
Also composes core of the hindbrain and midbrain
Arousal system
What is the metencephalon composed of?
Ascending and descending tracts
Cerebellum
Pons
What is the cerebellum function?
Sensorimotor coordination
Maintain fine motor skills
Plays a role in cognition/language/attention
What is the pons?
Contains the reticular formation and cranial nerve nuclei
Swelling on the ventral surface of the brainstem
-4th ventricle
Transfer information between the brainstem and the cerebellum
What is the mesencephalon composed of?
Midbrain -contains reticular formation Tectum -superior colliculi (visuomotor) -inferior colliculi (auditory) Tegementum
What is tegementum?
Contains cranial nerve and red nucleus
Substantia nigra
Periaqueductal gray
What is the function of the red nucleus?
Sensorimotor
-motor coordination; gait
Gets its red colour from hemoglobin and ferritin
What is the function of the substantia nigra?
Sensorimotor
Movement
Melanin
What is the function of the periaqueductal gray?
Analgesia
Defensive behaviour
Gate control theory of pain
-release endorphins and dense endorphin receptors that cause analgesia
What is the diencephalon composed of?
Thalamus
Hypothalamus
Mammillary Bodies
Optic chiasm
What is the structure of the thalamus?
2 lobes
-mass intermedia - runs through the third ventricle to connect
What is the function of the thalamus?
Sensory relay nuclei
Feedback bidirectional to and from the cortex
What is the function of the hypothalamus?
Located under the thalamus
The pituitary gland is suspended by the hypothalamus
-release hormones to modulate behaviour like stress, reproduction, and feeding
What is optic chiasm?
The portion of the brain after the optic nerve and before the optic tract
What is the telencephalon?
The largest division in the human brain Limbic system Basal ganglia Neocortex Corpus callosum
What is the corpus callosum?
The cerebral hemispheres are separated by a longitudinal fissure called the corpus callosum
The largest connecting 2 hemispheres
What are gyri and sulci?
Cortex convolutions that act as landmarks
What are the 4 lobes of the neocortex?
Frontal
Parietal
Occipital
Temporal
Longitudinal Fissure
Between hemispheres
Precentral Gyri
Primary motor cortex
Postcentral Gyri
Primary somatosensory cortex
Prefrontal Cortex
Nonmotor portion of frontal lobe
What are the layers of the neocortex?
There are 6 layers with the first being at the surface
Differ in:
Size of the cell body
Density of neurons
The proportion of cell types
Thickness
They all have a vertical flow of information
What is the function of the limbic system?
Regulation of motivated behaviours
- feedings
- fleeing
- fighting
- sex
What are the structures of the limbic system?
Hippocampus Cingulate cortex Amygdala Fornix Septum Mammillary bodies
What is the function of the hippocampus?
Spatial learning and memory
What is the function of the amygdala?
Emotional memory
Fear and anger
What is the fornix?
A tract that connects the hippocampus to the septum
What is the septum?
The anterior tip of the cingulate cortex
What is the function of the basal ganglia?
Voluntary motor system
Procedural learning
What are the deep subcortical structures of the basal ganglia?
Amygdala
Nucleus accumbens
Striatum (caudate nucleus and the putamen)
Globus pallidus
What is the function of the nucleus accumbens?
Reinforcement learning
-drug addiction
