CNS (A&PL2 Week 2) - Brain and Spinal Cord

Divisions of the Brain

Forebrain, Midbrain, Hindbrain

Forebrain

Processes sensory info and helps with reasoning and problem-solving. Also regulates autonomic, endocrine, and motor functions.

Midbrain

Helps to regulate movement and process auditory and visual info

Hindbrain

Helps to regulate autonomic functions, relay sensory info, coordinate movement, and maintain balance.

Prosencephalon (Forebrain) Subdivisions

Telencephalon and Diencephalon

_____ allow the flow of CSF through the brain

Ventricles

What nerves are found in the forebrain

Olfactory and Optic nerves

Telencephalon Parts

Cerebral cortex and Basal Ganglia

Hemispheric Lateralization

left: language and calculation. Right: visual, emotional, artistic awareness.  Opposite sides for motor control.  Connected by the corpus callosum and commissural fibers

Corpus Callosum

This is important for transmitting information from one side of the brain to the other

Telencephalon

This is where we see folded bulges called gyri that create indentations in the brain

Function: processing sensory information, controlling motor functions, and performing higher-order functions such as reasoning and problem-solving

Frontal Lobes

Prefrontal cortex, premotor area, and motor area

Function: Voluntary muscle movement, memory, thinking, decision-making, and planning

Parietal Lobes

Function: Receiving and processing sensory information

Also contains the somatosensory cortex, which is essential for processing touch sensations

Occipital Lobes

Function: Receiving and processing visual information from the retina

Temporal Lobes

Home of the limbic system structures, including amygdala and hippocampus

Function: Organize sensory input and aid in auditory perception, memory formation, and language and speech production

Basal Ganglia

Function: smooth motor movement; coordinate learned movement

Parkinson’s would be a dysfunction of this area

Diencephalon Parts

Composed of important centers for homeostasis:

Thalamus, Hypothalamus, Epithalamus, Pineal gland

Thalamus

Connects areas of the cerebral cortex that are involved in sensory perception and movement with other parts of the brain and spinal cord

Role in the control of sleep and wake cycles

Hypothalamus

Overall function: Control center for many autonomic functions including respiration, blood pressure, and body temperature regulation

Endocrine function: secretes hormones that act on the pituitary gland

Limbic system function: influences various emotional responses through its influence on the pituitary gland, skeletal muscular system, and ANS

Epithalamus

Connect the limbic system to other parts of the brain

Pineal Gland

Function:

Endocrine gland that produces melatonin

Vital to regulation of sleep-wake cycles and influences sexual development

Converts nerve signals from the sympathetic component of the PNS into hormone signals, thereby linking the nervous and endocrine systems

Limbic System

General function: Emotion, memory, and learning

Specific function:

Controls emotional states

Links conscious and unconscious portions of the brain

Helps with memory storage and retrieval

Limbic System Parts

Amygdala

Hippocampus

Cingulate gyrus

Thalamus

Hypothalamus

Mesencephalon (Midbrain)

Connects forebrain to hindbrain

Cerebral Aqueduct

Canal that connects the third and fourth cerebral ventricles

Tectum

Dorsal portion of the midbrain composed of the superior and inferior colliculi

Function: Visual and auditory reflexes

Superior colliculus

Inferior colliculus

Superior Calliculus

Processes visual signals and relays them to the occipital lobes

Inferior Colliculus

Processes auditory signals and relays them to the auditory cortex in the temporal lobe

Cerebral Peduncle

Anterior portion consisting of large bundles of fiber tracts that connect the forebrain to the hindbrain

Function: aids in control of autonomic and endocrine functions, as well as muscle reflexes and sleep and awake states

Substantia Nigra

Function:

Produces the neurotransmitter dopamine

Helps control voluntary movement and regulates mood

Rhombencephalon (Hindbrain) Subregions

Metencephalon and Myelencephalon

Metencephalon

The upper region of the hindbrain that contains pons and cerebellum

Pons

acts as a bridge connecting the cerebrum with medulla oblongata and cerebellum

Assists in control of autonomic functions, as well as states of sleep and arousal

Cerebellum

Relays information between muscles and areas of the cerebral cortex that are involved in motor control

Aids in fine movement coordination, balance and equilibrium maintenance, and muscle tone

Myelencephalon

Lower region, below metencephalon and above the spinal cord

Consists of medulla oblongata

Medulla Oblongata

Relays motor and sensory signals between the spinal cord and higher brain regions

Assists regulation of autonomic functions such as breathing, heart rate, and reflex actions, including swallowing and sneezing

Brain Stem

Essential for basic life

Cerebellum (basic definition)

Balance and posture

Medulla

Contains nuclei that regulate autonomic functions such as respiration and heartbeat.

Pons (Simple definition)

contains tracts and nuclei that link parts of the brain together and nuclei as well

Midbrain (Simple Definition)

contains colliculi that control auditory (inferior) and visual reflexes (Superior)

Cerebrospinal Fluid

Protects and supports nervous system

Produced in choroid plexuses (by which cells?) on ventricle walls

Circulates through ventricles, meninges, spinal cord

Cushion for the brain

Flow of CSF

lateral ventricles, interventricular foramens, third ventricle, cerebral aqueduct, and fourth ventricle

Blood Supply to Brain

Internal carotid, vertebral arteries to dural venous sinuses to internal jugular vein

Astrocytes join to capillary walls to form blood brain barrier

Cranial Protection of the Brain

Bones of Cranium, CSF, and Cranial Meninges

CSF flows in the ______ space

Subarachnoid

Bones of cranium

Sphenoid (1), Ethmoid (1), Parietal (2), Temporal (2), Frontal (1), and Occipital (1)

Cranial Meninges

Dura Mater, Arachnoid Mater, Pia Mater

Dura Mater

Consists of two layers of connective tissue

One attaches to your skull and the other adheres to your arachnoid mater

Contains a drainage system, called the dural venous sinuses, which allow blood to leave your brain and allows CSF to re-enter the circulation

Trigeminal nerve runs through this area

Arachnoid Mater

Thin layer

Does not contain blood vessels or nerves

Has spiderweb-like appearance because it has connective tissue projections that attach to your pia mater

Subarachnoid contains CSF that helps cushion your brain

Pia Mater

Thin layer that’s held tightly to the surface of your brain and spinal cord

Many blood vessels pass through this layer to supply your brain tissue with blood

In your spinal cord, pia mater helps maintain the stiffness of the cord

Spinal Cord

Begins at Foramen Magnum and ends at Conus medullaris. 33 vertebrae C7, T12, L5, S5

Cervical Plexus

Supplies nerves to the posterior head and neck, as well as to the diaphragm

Brachial Plexus

Supplies nerves to the arms

Lumbar Plexus

Supplies nerves to the anterior leg

Sacral Plexus

Supplies nerves to the posterior leg

Cauda Equina

This it a group of nerves and nerve roots stemming from the distal end of the spinal cord, typically from L1-L5 and contains axons of nerves that give both motor and sensory innervation to the legs, bladder, anus, and perineum

Spinal Cord Enlargements

Two enlargements (they are called this due to the abundance of nerve cells and connections needed to process information related to the upper and lower limbs)

Cervical Enlargements

C5 to T1. Corresponds to the arms

Lumbar Enlargements

L2 to S3. Corresponds to the legs.

Spinal Cord Histology

Gray and White Matter

Gray Matter

Home to neural cell bodies, axon terminals, and dendrites, as well as all nerve synapses

Dorsal (Posterior) gray horn

passes sensory information (touch, pain, temperature, and proprioceptive information) via ascending nerve signals to the brain

Problems: may affect the brain’s ability to interpret sensory information

Ventral (anterior) gray horn

sends descending nerve signals governing motor activities to your autonomic nerves

Gray commissure

Connects dorsal and ventral horn regions and surrounds the central canal, where CSF runs down the center of the spinal cord

Lateral Horns

Only present in thoracic and superior lumbar spinal cord segments and contain autonomic motor neuron cell bodies that innervate the visceral organs

White matter

Composed of bundles of axons

Job is to conduct, process, and send nerve signals up and down the spinal cord

Damage to this area can affect your ability to move, use your sensory faculties, or react appropriately to external stimuli

Some people may suffer deficits in reflexive reactions

Appears white due to the abundance of lipid-rich myelin that surrounds most of the axons

Alzeimer’s Disease

Most common form of dementia

Symptoms usually begin in the 60’s and slowly and irreversibly progress

Clumps and tangles: amyloid plaques and tau

Loss of neural connections

Plaques: beta-amyloids are protein subunits which accumulate as waste with toxic effects as they form plaques

Tau proteins which normally provide internal support and transport for tangles, disrupting this process

Lateral Sulcus

Separates Frontal and temporal lobes

Central Sulcus

Separates Frontal and Parietal lobes