Anatomy and Physiology of the Nervous System Flashcards
The Nervous System can be divided into several sections based on either anatomical or functional divisions.
Anatomical Divisions:
- Spinal Cord • Brainstem
* Cerebrum
The spinal cord sits within the vertebral column.
It is made up of several distinct anatomical regions, corresponding to curves in the vertebral column:
- Cervical
- Thoracic
- Lumbar
- Sacrum
- Coccygeal
Spinal cord layers correspond to specific vertebral discs, these are;
- Cervical
- Seven Vertebrae (C1-C7)
- Thoracic
- Thirteen Vertebrae (T1-T13)
- Lumbar
- Seven Vertebrae (L1-L7)
- Sacrum
- Coccygeal
- Six Vertebrae (C1-C6)
Annulus Fibrosis
Fibrous collagen disc, providing mechanical support to the vertebral column.
Nucleus Pulposus
Gel like collagen and water inner layer, providing mechanical support.
Spinal Nerves
Exit and enter the spinal cord via the dorsal or ventral roots. Nerve exits through the vertebral column via the intervertebral foramen.
Meningeal Layers
Three separate membrane layers as part of the meningeal system.
• Pia
• Arachnoid
• Dura
Cerebrum
The cerebrum rests on top of the Temporal bone, extending from the Occipital bone to the Zygomatic arch.
The cerebral lobes correspond to their respective bones:
• Frontal
• Parietal
• Occipital
• Temporal
Meningeal System
Three membranes that envelop the brain and spinal cord:
• Dura Mater
• Arachnoid Mater
• Pia Mater
Cerebrospinal fluid circulates within the subarachnoid space between the arachnoid mater and the pia mater.
The primary function of the meninges is to protect the central nervous system.
Dura Mater
The Dura Mater is a thick fibrinous layer, surrounding the cerebrum, constituting the outermost meningeal layer near to the skull. The Dura receives dense arterial, venous and nerve fibre (Trigeminal) innervation.
The Dura consists of two layers:
• Periosteal layer: Proximal to the skull
• Meningeal layer: Proximal to the Arachnoid Mater
Arachnoid Mater
The Arachnoid Mater is a thin, transparent membrane, composed of fibrous tissue forming a web-like structure. The Arachnoid receives little arterial, venous and nerve fibre innervation.
The sub-arachnoid space exist between the Arachnoid and Pia Mater, through which cerebrospinal perfusion of fluid occurs.
Pia Mater
The Pia Mater is a delicate, thin membrane attached to the superficial surface of the cerebrum and spinal cord. The Pia receives dense arterial, venous and nerve fibre innervation.
The space between the Pia and nervous system tissue enables formation of Perivascular spaces, facilitating immune function.
Gyrus
Ridge like structure in the cerebral cortex, general surrounded by one or more sulci.
Sulci
Groove like structure in the cerebral cortex, generally surrounding a specific gyrus. Larger Sulci are termed fissures.
Anatomical purpose of identification of Gyrus & Sulci
is to navigate around the brain during surgery and imaging.
Functional purpose of identification of Gyrus & Sulci
is to identify regions of conserved function.
Neurological function enables an organism to
respond to external stimuli in an appropriate manner.
The nervous system can be divided into
Central Nervous System
Peripheral Nervous System
The CNS can be divided into
The brain- receives and processes sensory information, initiates responses. Stores memories and generates thoughts and emotions
and the spine- conducts signals to and from the brain controls reflex activities
The PNS can be divided into
Motor neurons- CNS to muscles and glands
Sensory neurons- sensory organs to CNS
Motor neurons make up the
Somatic nervous system - controls voluntary movements
and the autonomic nervous system - controls involuntary responses
The autonomic nervous system is made up of
The sympathetic division- fight or flight
The parasympathetic system- rest or digest
Somatic Nervous System
Voluntary control over motor function and sensory perception.
Autonomic Nervous System
Involuntary control over motor function and sensory perception.
Sympathetic Nervous System
• Fight or flight response. • Homeostasis • Sensory. • Motor.
Parasympathetic Nervous System
- Rest and Digest.
- Sexual arousal.
- Salivation.
- Lacrimation.
- Urination.
- Digestion.
- Defecation.
Blood Supply: Ventricles
The ventricular system is composed of four fluid- filled interconnected cavities within the brain:
• Lateral ventricles
• Third ventricle
• Fourth ventricle
Within each ventricle the Choroid Plexus is responsible for the production of Cerebrospinal Fluid (CSF).
The ventricles form a continuous system with the central canal of the spinal cord.
Cerebrospinal Fluid
- Cerebrospinal fluid (CSF) is produced by the Choroid Plexus in the Ventricles.
- CSF circulates around the nervous system.
- Arachnoid granulations draw CSF out of the sub-arachnoid space and filter into the venous system (via Sinuses).
Similar composition to systemic plasma with notable variations in calcium, magnesium, potassium and amino acids.
Microscopic evaluation demonstrate low cellular content, with elevated levels indicative of pathology.
CSF Production & Drainage Review
• Granulations Active removal of CSF from sub-arachnoid space. • Sinuses Receive CSF from the granulations, permit filtration into the venous system. • Choroid Plexus Receive arterial blood supply, enable production of CSF
Blood Supply: Arterial
- Inputs to Cerebral Circulation
- Internal & External Carotid
- Ventral Spinal
- Vertebral
- Circle of Willis
- Links both hemispheres
- Primary Arteries
- Anterior Cerebral
- Middle Cerebral
- Posterior Cerebral
Vascular Territories
• Specific region of the brain associated with named arterial
innervation.
Secondary Arteries
• Provide localised vascularisation to specific parts of the brain regions.
Venous Outputs from Cerebral Circulation
- Jugular
- Maxillary
- Vertebral
Venous Sinuses
- Dorsal sagittal
- Temporal
- Dorsal petrosal
- Middle meningeal
Blood Supply: Sinuses
Neural Sinus
• Low oxygenated blood collects within the neural sinuses.
• Movement of blood in these regions is significantly slower than in venous systems.
• Facilitates exchange between CSF and blood via the Blood Brain Barrier (BBB).
Brain Divisions: Development
During development, regions of the brain termed vesicles due to hollow nature.
• Primary vesicles develop first.
• Differentiate into secondary vesicles.
Brain Divisions: Telencephalon
Frontal Lobe: Problem solving, memory, behaviour.
• Parietal Lobe: Sensation
• Temporal Lobe: Consciousness, memory.
• Occipital Lobe: Visual perception
Brain Divisions: Rhinencephalon
The ‘olfactory-brain’ responsible for sensory processing of olfactory stimuli, linking in cognitive and behavioural function.
Includes the olfactory bulb, olfactory tract, anterior olfactory nucleus, olfactory stria, amygdala, and hippocampus.
Brain Divisions: Diencephalon
The diencephalon can be divided into the following structures:
• Thalamus: Sensory processing structure.
• Hypothalamus: Endocrine function.
• Epi-Thalamus: Including the Pineal, responsible for some endocrine function.
• Sub-Thalamus: Motor integration.
Brain Divisions: Mesencephalon
The midbrain region, associated with: • Vision • Hearing • Motor control • Sleep • Wakefulness Principle components include: • Tectum • Tegmentum • Cerebral peduncles
Brain Divisions: Metencephalon
The Metencephalon can be divided into the following structures:
• Cerebellum: Motor control
• Pons: Sensory-Motor Relay, auditory, respiration, facial sensation, eye movement, chewing, facial secretions.
Brain Divisions: Myelencephalon
The Meyencephalon can be divided into the following structures: • Medulla Oblongata: Respiratory control, Cardiac and vasomotor control, physiological reflexes (swallowing, vomiting, coughing sneezing, etc). • Pyramids: Contain the pyramidal motor tracts.
