# Checklist 1 – Nervous System

###### tags: `CCN` `Nervous System` `Brain`

## Central Nervous System

- Consists of the brain, brain stem and the spinal cord, where the central nervous system (CNS) is mostly focused in the brain and spinal cord, where all cognitive and subconscious thought occurs.
- The brain processes the received information from the peripheral nervous system (PNS), as well as relaying information to the PNS for implementation.
- It plays a central role in the control of most bodily functions such as awareness, movement, thoughts, speech, memory and sensation.
- The main conduit of the CNS is the spinal cord.


_Figure 1 - Central Nervous System_

## Peripheral Nervous System

- The nerves and ganglia that exist outside of the brain and spinal cord.
- The main job is to relay information transmitted by the brain throughout the body, and to gather input from the body and relaying it back to the brain through the spinal cord.
- The nerves form the communication network between the CNS and the body (parts).


_Figure 2 - Peripheral Nervous System_

### Somatic Nervous System

- The Somatic Nervous System (SMS) oversees voluntary control of the skeletomuscular system. such as bodily movements of the muscles, skin and bones.

### Autonomic Nervous System

- The Automatic Nervous System (ANS) oversees the involuntary controls of the body, such as breathing, digestion, operation and function of the organs, involuntary movements of (smooth) muscles, urination and sexual arousal.
- Fight or flight is also overseen by the ANS.


_Figure 3- somatic & Autonomic Nervous System_

## Neuroanatomy

### Planes, Sections

#### Saggital

- The left or right plane (when facing from the front or back)

#### Coronal

- Front or back plane (when facing from front or back).
- You can see both left and right half from the front or back.

#### Transverse/Axial/Horizontal

- Bottom or Top plane (when facing from the front or back)
- You can see both left and right half from the top or bottom.


_Figure 4 - Planes and Sections_

### Sides, Directions

#### Superior/Dorsal

- The top part of the brain.
- Towards surface of the back-top of the head.

#### Inferior/Ventral

- The bottom part of the brain.
- Towards surface of the chest-bottom of the head.

#### Anterior/Rostral

- The front side of the brain

#### Posterior/Caudal

- The back side of the brain

#### Medial

- The medial line is the line down the middle (from the front to back) of the brain.
- Towards the middle of the body

#### Lateral

- The literal side(s) are the sides of the brain (human perspective)
- Away from the middle of the body


_Figure 5 - Sides and Directions_

### White matter

- Made up of mostly myelinated axons (and other information transmitters) which together make the so called "information highway" of the brain.
- A shiny layer underneath the cortex that consists of largely axons with white myelin sheaths.

### Grey matter

- Area of the brain that is dominated by cell bodies and (usually) un-myelinated axons.

### Nuclei

- An anatomical collection of neurons within the CNS.
- Not to be mistaken with Ganglia, which is an anatomical collection of neurons in the PNS.

### Hemispheres

- The brain consists of two hemispheres: left and right hemisphere.
- It's divided evenly down the medial line.
- The left hemisphere handles most information analysis and extraction of elements, such as the recognition of serial events.
- The left hemisphere controls the right side of the body.
- The right hemisphere does synthesis by putting isolated elements together and perceiving things as a whole.
- The right hemisphere controls the left side of the body.

### Ventricles

- Produces Cerebrospinal fluid (CSF).
- The CSF acts as a cushion or buffer between the cerebral cortex and the inside of the skull.
- The CSF plays an important role for the blood flow through the brain and cerebral autoregulation.

### Brainstem

- Brainstem is the posterior part of the brain adjoining and structurally continuous with the spinal cord.
- The brainstem is extremely important, as the nerve connections from the motor and sensory systems of the cortex pass through it to communicate the with PNS.
- The brainstem plays an important role in the regulation of cardiac and respiratory functions, consciousness and the sleeping cycle.
- The brainstem consists of the medulla, pons and midbrain.

#### Hindbrain

- The Hintbrain supports vital bodily processes.

##### Medulla

- The medulla is the lower half of the brainstem.
- Controls autonomic functions
- Connects higher levels of the brain to the spinal cord.
- Is responsible for regulating basic functions of the ANS, such as respiration, heart rate, vasodilation, reflexes (like vomiting, coughing, sneezing and swallowing).

##### Cerebellum

- The cerebellum is essential for making fine adjustments to motor actions.
- A dysfunction of the cerebellum primarily result in problems with motor control.
- Four principles are important to cerebellar processing: Feedforward processing, divergence & convergence, modularity and plasticity.
- Signal processing in the cerebellum is almost entirely feedforward. Signals move through the system from input to output with very little internal transmission.
- The cerebellum both receives input and transmits output via a limited number of cells.
- The cerebellar system is divided into thousands of independent modules of similar structure.

##### Pons

- The white matter includes tracts that conduct signals from the cerebrum down to the cerebellum and medulla, as well as tracts that carry sensory signals up into the thalamus.
- The pons contains nuclei that relay signals from the forebrain to the cerebellum, along with nuclei that deal primarily with sleep, respiration, swallowing, bladder control, hearing, equilibrium ,taste, eye movement, facial expressions, facial sensation and posture.
- The pneumotaxic center lays within the pons. It consists of nucleus that regulate the change from inspiration to expiration.
- The pons also contains the sleep paralysis center of the brain and plays an important role in generating dreams.

#### Midbrain

- The midbrain controls many autonomous and manual functions such as hearing, motor control, sleep and wake-cycles, arousal, alertness and temperature regulation.

### Diencephalon

- Part of the forebrain
- The diencephalon is made up of 4 main components: thalamus, subthalamus, hypothalamus and epithalamus.

##### Thalamus

- Relay station of the brain.
- Processes input and distributes it to the relevant centers in the brain.
- Is responsible for relaying sensory and motor signals to the cerebral cortex and the regulation of consciousness, sleep and alertness.
- The thalamus consists of two halves.
- The thalamus has a system of myelinated fibers that separate the different thalamic subparts. These areas are defined by distinct clusters of neurons.

##### Hypothalamus

- Hormone and autonomic control
- It regulates hunger, hormones, temperature, sleep and other cycles.
- The hypothalamus can pass signals back and forth between the anterior and posterior pituitary by the neurohypophysis and medium eminence.
- The hypothalamus can sample the blood composition at two sites, the subfornical organ and the organum vasculosum of the lamina terminalus. This is important for the uptake of circulating hormones and to determine concentration of substances in the blood.
- The output of the hypothalamus can be divided into neural projections and endocrine hormones. The neural projections tend to run bidirectionally.
- Integral part of the endocrine system, with the key function of linking the nervous system to the endocrine system via the pituitary gland.

#### Telencephalon

- The embryonic structure (early development) from which the cerebral cortex develops.

##### Limbic system

- Memory and Emotions
- Consists of: Frontal Cortex, Fornix, Cingulate Cortex, Corpus Collosum, Thalamus, Stria Terminalis, Hippocampus, Amygdala, Mammillary body, Olfactory Bulb, Septum.

##### Basal ganglia

- Group of structures in the thalamus overseeing motor control and motor learning processes. (voluntary motor responses and decision making).
- A group of nuclei of varied origin in the brains of vertebrates that act as a cohesive functional unit.
- The basal ganglia are associated with a variety of functions including voluntary motor control, procedural learning relating to routine behaviors or "habits" such as bruxism, eye movement, cognitive and emotional functions.
- The basal ganglia are composed of striatum, pallidum, substantia nigra and subthalamic nucleus.
- The basal ganglia play a central role in a number of neurological conditions including Parkinson's disease and Huntington's disease.

##### Cerebral cortex

- The cerebral cotrex is the outermost layer of matter on the brain, made up of neural tissue, that plays the role in memory, attention, perception, awareness, thought, language and consciousness.
- The Cerebral cortex is 2-4mm thick.

#### Gyri

- "Bumps" on the brain surface.
- **Dentate gyrus** is a simple cortical region that is an integral portion of the larger functional brain system called the hippocampal formation.
- **Inferior Temporal Gyrus** is placed below the middle temporal sulcus and is connected behind with the inferior occipital gyrus; one of the higher levels of the visual processing, associated with the representation of complex object features.
- **Middle temporal gyrus** is located between the superior temporal gyrus and inferior temporal gyrus, and handles tasks like the recognition of known faces.
- **Inferior frontal fyrus** is broca's area and handles tasks like speech production.

#### Sulci

- "Grooves" on the brain surface.
- **Central Sulcus** divides frontal from parietal lobes.
- **Lateral sulcus** demarcates the temporal lobe.
- **Cytoarchitecture** is the study of the cellular composition of the CNS's tissues under the microscope.

#### Cortical layers

- Exists of 6 layers of the cerebral cortex, where each layer has a different cell density, along with separate functions for each.
- **Molecular layer** contains the flattened dendritic trees of purkinje cells, and the huge array of parallel fibers from the granular layer that penetrates the purkinje cell dendritic trees at right angles.
- **External granular** is a thin layer that consists numerous small, densely packed neurons.
- **External pyramidal** is the most superficial layer of the cerebral cortex.
- **Internal granular** is a layer that receives the afferent connections from the thalamus and from other cortical regions and sends connections to the other layers.
- **Internal pyramidal** consists predominantly of the medium-sized and large pyramidal cells. It's the source of the output or corticofugal fibers.
- **Multiform (fusiform) layers** is the deepest layer of the cortex that directly overlies the subcortical white matter.


_Figure 6 - Cortical layers_

#### Brodmann's areas

- a region of the cerebral cortex in the human or other primate brain defined by its cytoarchitecture or histological structure and organization of cells.


_Figure 7 - Brodmann Area_

### Lobes & basic functions

- Each lobe of the cerebral cortex plays a different role in the overall function.

#### Occipital

- Exclusively reserved for visual processing

#### Temporal

- "What" partway, auditory cortex, language perception, memory

#### Parietal

- Linking sensory info to action
- Receiving input from contralateral body senses
- Perceives location of objects, own body and direct attention, functions: integrating sensory information, manipulating of objects, visual and special processing.

#### Frontal Lobe

- Motor function, planning, language production, personality