Nervous System Organization

• The brain functions by producing movement, receiving and processing information, and generating responses.
• Neuroplasticity refers to the brain's ability to change physically or chemically due to environmental factors, injury, or aging.
• Phenotypic plasticity describes an individual's capacity for neuroplasticity based on their observable traits.

Neural Potential

• Afferent nerves carry information towards the central nervous system (CNS), and are sensory.
• Efferent nerves carry information away from the CNS and are motor.

Brain Orientation and Protection

• Meninges are protective tissues between the brain and skull.
• The dura mater is the tough, outer layer of the meninges.
• The arachnoid layer is a thin, delicate connective tissue sheet.
• Cerebrospinal fluid (CSF) flows between the arachnoid and pia mater, as well as in the brain ventricles.
• CSF cushions the brain, transports nutrients, removes waste, and regulates temperature.
• The pia mater is a membrane that clings to the brain's surface, softer than the dura mater.

Cerebral Cortex and Lobes

• The cerebral cortex is the outer layer of the forebrain, composed of grey matter.
• The cerebrum contains the four lobes.
• The frontal lobe handles executive functions like cognition, personality, and decision-making.
• The parietal lobe is responsible for sensory integration and motor coordination.
• The temporal lobe processes auditory, taste, olfactory, and emotional sensory information, memory, and language.
• The occipital lobe processes visual information.
• The cerebellum is located at the back of the brain and is essential for motor coordination.
• A gyrus is a bump/protrusion caused by folding in the brain.
• A sulcus is a groove in brain matter.
• A fissure is a very deep sulcus.

Cerebral Circulation

• The brain is covered in blood vessels.
• The cerebral hemispheres receive blood from the anterior, middle, and posterior cerebral arteries.
• A stroke occurs when neurological symptoms arise from severely reduced blood flow.
• Strokes in different arteries affect different brain areas.
• Strokes in the left hemisphere affect the right side of the body due to the brain's cross-connections.

Brain's Internal Features

• Grey matter consists of cell bodies and blood vessels where neurons collect and modify information.
• White matter is composed of fat-sheathed neural axons/fibres.
• The corpus callosum is a bridge connecting the two brain hemispheres.
• Cerebral ventricles are cavities in the brain containing CSF, including the left and right lateral ventricles, third ventricle, and fourth ventricle.
• Subcortical regions are areas beneath the cortex that communicate with cortical areas to further process sensory information.
• The brain contains glial cells that aid and modulate neuron activities, and neurons that communicate with each other to process information.
• Bundles of axons from neurons form tracts within the CNS and nerves in the PNS.

Spinal Cord

• The spinal cord controls bodily movements, with sensory and motor neurons communicating.
• It can act independently to produce reflexes.
• The brain cannot inhibit reflexes.
• The brainstem begins where the spinal cord enters the skull.

Hindbrain Components

• The hindbrain controls fine and gross motor functions, such as breathing and balance.
• The cerebellum is involved in complex movements and cognitive functions; its size relates to cognitive capacity in humans.
• The reticular formation is a mix of grey and white matter that stimulates the forebrain, regulates the sleep-wake cycle, and is theorized to be involved in personality.
• The pons connects the cerebellum to the brain and controls vital body movements.
• The medulla contains nuclei that regulate vital functions like breathing and cardiovascular regulation.

Midbrain Components

• The tectum is involved in visual and auditory processing and produces orienting movements via the superior (visual input) and inferior colliculus (auditory input).
• The tegmentum is a motor structure involved in eye and limb movements, species-specific behaviors, and pain perception/regulation (periaqueductal grey matter - PAG).

Diencephalon

• The diencephalon integrates sensory and motor information on its way to the cerebral cortex.
• Key structures of the diencephalon are the thalamus and hypothalamus.
• The hypothalamus controls homeostasis, hormone functioning (connected to the pituitary gland), and bodily functions like feeding, sexual behavior, sleeping, temperature regulation, and emotional regulation.
• The thalamus is a conveying center that transmits sensory information to the correct cortices, integrating and processing sensory and motor information.
  • The lateral geniculate processes visual information.
  • The medial geniculate processes auditory information.
  • The dorsomedial nucleus processes olfaction.

Forebrain

• The neocortex regulates mental activities and contains six neocortical layers with varying cell densities.
• The basal ganglia controls voluntary and involuntary movement; structures include the caudate nucleus, putamen, and globus pallidus.
• The limbic system regulates emotions and behaviors that store and require memory, includes the amygdala, hippocampus, and cingulate cortex, and regulates emotional and sexual behaviors, memory, and spatial navigation.
• The olfactory system is located at the front of the brain behind the nose, includes the pyriform cortex, amygdala, and dorsomedial thalamus.
• The allocortex controls motivational and emotional states, plays a role in memory and includes the hippocampus, parts of the amygdala, and the cingulate cortex.

Somatic Nervous System (SNS)

• The SNS transmits sensory and motor information to and from the body, controlled by the CNS through cranial and spinal nerves.
• There are 12 cranial nerve pairs.
• The spinal cord is contained within the spinal column (vertebrae).
• Vertebrae are categorized into cervical, thoracic, lumbar, sacral, and coccygeal.
• Dermatomes are body segments corresponding to spinal cord segments.
• According to the Law of Bell and Magendie, posterior fibres are afferent and anterior fibres are efferent.

Autonomic Nervous System (ANS)

• The ANS controls autonomous functioning like breathing, heart rate, and glands.
• The parasympathetic nervous system prepares the body to rest and digest and reverses the fight-flight-freeze response.
• The parasympathetic nervous system activates from cranial nerves and the sacral region of the spine.
• The sympathetic nervous system arouses the body for action via the fight-flight-freeze response.
• Activation for the sympathetic division starts in the thoracic and lumbar spinal regions.

Enteric Nervous System (ENS)

• The ENS is a network of neurons in the gastrointestinal tract that controls bowel movement, secretion, blood flow, nutrient absorption, and waste elimination.
• The ENS is called the 'second brain' because it largely functions independently of the ANS.
• The ENS is connected by the vagus cranial nerve (nerve 10).

Principles of Nervous System Function

• Neurons are interconnected by synapses to function.
• Sensory and motor divisions exist throughout the nervous system.
• The CNS is organized hierarchically and in parallel.
• Many brain functions are crossed (left brain controls the right side of the body, etc.).
• Brain functions are localized and distributed.
• The brain is symmetrical and asymmetrical (certain brain regions may have specializations).
• The nervous system works by balancing excitation and inhibition.
• The brain divides sensory input for object recognition and motor control.
• The nervous system produces movement in a perceptual world the brain constructs.
• Neuroplasticity is a special feature of the nervous system's functioning.