What are the different names for areas of the brain?
- Rostrum (beak), caudum (tail), dorsum (back - superior) and ventrum (stomach - inferior)
- Anterior/frontal, posterior, lateral (sides) and medial (center)
- Coronal (vertical plane cut), horizontal (horizon plane cut) and sagittal (cut lengthways)
What are different terms to keep in mind while considering brain parts?
- Ipsilateral - structures that lie on the same side
- Contralateral - structures that lie on different sides
- Bilateral - structures lie in each hemisphere
- Proximal - structures close to one another
- Distal - structures far from one another
- Afferent - movement toward brain structure
- Efferent - movement away from brian structure
What makes up the autonomic nervous system?
- Parasympathetic nerves (rest and digest)
- Sympathetic nerves (fight or flight)
How does the brain and spinal cord remain protected from injury/infection?
- Brain is enclosed in the skull and the spinal cord in interlocking bony vertebrae (SNS and ANS being outside of it.)
- The CNS has a triple-layered set of membranes (meninges) with a outer dura mater (tough), arachnoid membrane (thin sheet) and inner pia mater (moderately tough)
- CNS cushioned by CSF; if outflow of CSF is blocked than the increasing pressure leads to hydrocephalus
- Blood-brain barrier limits the movement of chemicals from the rest of the body into the CNS and protects from infection.
How is blood supply given to the brain?
It receives blood supply from two internal cartoid arteries and two vertebral arteries which branch off. The anterior cerebral artery (ACA) irrigates the medial/dorsal parts of the cortex, the middle cerebral artery (MCA) the lateral and the posterior cerebral artery (PCA) the ventral/posterior
Where does the brain originate from?
Undifferentiated neural stem cells; these self-renewing multipotential cells give rise to different neurons and glia in the nervous system.
How are neurons formed?
Stem cells give rise to progenitor cells which migrate and act as precursor cells leading to nondividing primitive cells (blasts). Neuroblasts differentiate into neurons, glioblasts into glial cells.
What type of neurons are there?
- Sensory neurons - the simplest sensory receptor is a bipolar neuron (consists of a cell body, with a dendrite and an axon found in the retina); the somatosensory neuron (dendrite and axon are connected which speeds messages) projects from a sensory receptor to the spinal cord
- Interneurons - link up sensory and motor neuron activity to the CNS; have multiple dendrites that branch extensively but only one axon.
- Motor neurons - located in between the brainstem and spinal cord to muscles. Motor neurons are called the final common path as all movement produced by the brain is through them.
What are the types of interneurons?
- Stellate (star shaped) characterised by many branches
- Pyramidal cells (pyramid shaped cell body) in the cortex - output cell for its structure
- Purkinje cells of the cerebellum - output cell for its structure
What are the types of glia?
- Ependymal cells - line the brain’s ventricles and make CSF
- Astroglia (star-shaped) - connection with blood-brain barrier, provides structural support and neuron nutrition.
- Microglia - fight infection and remove debris
- Oligodendroglia - insulate neurons in the CNS
- Schwann cells - insulate sensory and motor neurons in the PNS
What are the types of brain matter?
- Gray matter - predominately makes up the cortex; is grey due to capillaries and neuronal cell bodies prominent there.
- White matter - consists of mainly axons that extend from these cell bodies to form connections with neurons in other brain areas. Axons are myelinated by glial cells that are white.
- Reticular matter - contains a mix of cell bodies and axons which makes it acquire a mottled grey/white appearance; midregions of the brain stem contain it.
What cell clusters are in the PNS?
Ganglia
What are tracts?
Fiber pathways that are large collections of axons projecting toward/away from the nucelus in the CNS; they carry information from one place to another within the CNS. When the fiber pathways enter/leave the CNS they are nerves but once they enter the CNS they are tracts.
What are the sections of the brainstem?
It has the midbrain and the hindbrain. The brainstem core consists of cranial nerve nuclei and other nuclei that mediate regulatory functions. Sensory nerve fibers from the spinal cord pass through the posterior regions of the brainstem on their way to the forebrain + motor fibers from the forebrain pass through anterior regions of the brainstem on their way to the spinal cord.
What are features of the hindbrain?
Its most distinctive structure is the cerebellum which a surface gathered into narrow folds (folia). It has a reticular formation which controls sleeping and consciousness (reticular activating system). its pons (upper) bridge inputs from the cerebellum to the rest of the brain while the medulla (lower) regulates vital functioning like breathing.
What does the cerebellum do?
It plays a role in motor coordination and motor learning. It receives its impulses from the vestibular system (sensory receptors in the ear for balance/movement) which maintains bodily equilibrium.
What are the features of the midbrain?
It has two subdivisions:
1. Tectum (posterior sensory component) - consists of two bilaterally symmetrical nuclei that receive sensory information from the eyes/ears > they locate objects in space and orient towards those objects (visual or auditory) and mediates pattern recognition.
2. Tegmentum (motor structure) - red nucelus controls limb movements and coordinates for walking; substantia nigra is important for movement and places value on things rewarding to us and acquiring habits to such objects; periacqueductal gray matter controls species-typical behaviours (like sexual behaviour) and modulating pain responses
What are the two sets of bilaterally symmetical nuclei in the tectum?
- Superior colliculi (upper) receives projections from the retina of the eye
- Inferior colliculi (lower) receives projections from the auditory receptors of the ear
What are the features of the diencephalon?
Includes three thalamic structures:
1. Hypothalamus - takes part in nearly all aspects of motivated behavior and helps control endocrine functions
2. Epithalamus - secretes melatonin and the habenula regulates hunger/thirst
3. Thalamus.
What does the thalamus do?
It relays information from sensory systems to their appropriate targets (lGB, MGB and VLP), between cortical areas (pulvinar nucleus) and between the cortex and a number of brainstem regions.
What are the three main telencephalic structures?
- Neocortex
- Basal Ganglia - enveloped by the frontal neocortex; involved in motor behavior and associative learning
- Limbic System - enveloped by the posterior neocortex; spatial/emotional behavior
What are the features of the basal ganglia?
Collection of nuclei that form a circuit with the cortex.The ganglia include the putamen, globus pallisud and caudate nucleus (receives projections from all areas of cortex and sends to the putamen + globus pallidus > frontal cortical areas)
What are the functions of basal ganglia?
- Connect sensory regions of the cortex to motor regions of the cortex
- Regulate movement so that it is fluid
- Involved in associative learning (in turn leading to habits)
> It focuses on controlling, not producing, movements such as with Huntington’s and Parkinsons disease and Tourettes
What are the functions of the limbic system?
It plays a role in self-regulatory behaviours with structures like the amygdala (emotion), hippocampus (personal memory/spatial navigation) and cingulate cortex (sexual behavior, social interactions and executive functions)
