Nervous System Structure Quiz

Nervous System Structure

• The nervous system is divided into the central nervous system (CNS) and the peripheral nervous system (PNS).
• The CNS includes the brain and spinal cord.
• The PNS includes cranial nerves, spinal nerves, and peripheral ganglia.
• The brain is protected by the skull, and the spinal cord is protected by the vertebral column.
• The brain is made up of neurons, glia, and other supporting cells.
• The brain floats in cerebrospinal fluid (CSF).
• The brain receives about 20% of blood flow from the heart.
• The blood-brain barrier protects the brain from chemicals.
• Glucose is crucial for brain function and has limited storage, requiring continuous blood supply.
• 6 seconds without blood flow can cause unconsciousness, and several minutes can cause permanent brain damage.
• Anatomists named brain structures based on their resemblance to objects.
  • Amygdala: almond-shaped
  • Hippocampus: sea horse
  • Genu: knee
  • Cortex: tree bark
  • Pons: bridge
  • Uncus: hook

Anatomical Directions

• Neuraxis: Imaginary line from the bottom of the spinal cord to the front of the brain.
• Dorsal: top of the head
• Rostral or anterior: front of the face
• Caudal or posterior: away from the front of the face & back of the head
• Ventral: bottom of skull/front of body
• Lateral: towards the side
• Medial: towards the middle
• Ipsilateral: same side of body
• Contralateral: opposite side of body

Anatomical Planes

• The nervous system is sliced in three ways:
  • Cross sections
  • Horizontal sections
  • Sagittal sections

Meninges and Ventricular System

• Meninges: Protective membranes around the brain and spinal cord.
• Consist of three layers: Dura Mater, Arachnoid Membrane, and Pia Mater.
• Dura Mater: Durable, thick, tough outer layer.
• Arachnoid Membrane: Weblike, soft, and spongy middle layer.
• Subarachnoid Space: space between the arachnoid membrane and pia matter
• Pia Mater: Attached to the brain and spinal cord containing small blood vessels.
• Cerebrospinal fluid (CSF) fills the subarachnoid space.
• CSF is produced and reabsorbed by the choroid plexus in the ventricles (chambers in the brain).

Ventricles

• Types of Ventricles:
  • Lateral: two large ventricles
  • Third: located at the midline of the brain
• Cerebral Aqueduct: connects the third ventricle to the fourth ventricle
  • Fourth: Long tube connecting the third ventricle to the fourth ventricle
• CSF flows through the ventricles, and out to the subarachnoid space and back into the blood supply of the dural venous sinuses.

Obstructive Hydrocephalus

• Causes of blockage: tumors, congenital issues.
• Consequences: Increased intracranial pressure, occlusion of blood vessels, permanent or fatal brain damage.
• Treatment: Surgeons create a shunt to relieve pressure.

The Forebrain: Telencephalon

• The cerebral cortex surrounds the cerebral hemispheres.
• It is convoluted with grooves (sulci) and bulges (gyri) to increase surface area.
• The cerebral cortex is composed of:
  • White matter: Myelinated axons underneath the cortex.
  • Gray matter: Cell bodies and dendrites (outer layer)
• Divided into four lobes: Frontal, Parietal, Temporal, and Occipital. Each lobe has specific functions (e.g., movement, processing sensory information)

Sensory and Motor Cortices

• Primary sensory cortex receives inputs from various sensory organs, processing in different cortical areas.

The Forebrain: Diencephalon

• The second major division of the forebrain, located between the telencephalon and the mesencephalon.
• It surrounds the third ventricle and contains two key structures:
  • Thalamus: relay center for sensory information; Greek for "inner chamber".
  • Hypothalamus: regulates autonomic, endocrine, and survival-related behaviors.

Pituitary Gland

• The hypothalamus produces hormones and regulates the anterior and posterior pituitary glands.
• Anterior pituitary: produces hormones (e.g., prolactin, somatotropin).
• Posterior pituitary: stores and releases hormones (e.g., oxytocin, vasopressin).

The Midbrain: Mesencephalon

• The midbrain plays a key role in motor control, visual and auditory reflexes, and processing of pain and species-specific behaviors.
• The midbrain contains the tectum and tegmentum.
• The tegmentum contains the reticular formation (sleep, arousal, attention).

The Hindbrain: Metencephalon and Myelencephalon

• Metencephalon: includes cerebellum and pons.
• The cerebellum is involved in motor coordination and movement, receiving sensory input and feedback.
• The pons relays information between the cerebral cortex and cerebellum.
• Myelencephalon: also known as medulla oblongata; controls vital autonomic functions like cardiovascular and respiratory regulation.

The Spinal Cord

• The spinal cord connects to the brain and carries sensory information from the body to the brain and motor commands from the brain to the body.
• The spinal cord is protected by the vertebral column and contains two key structures:
  • Dorsal roots: transmit sensory information
  • Ventral roots: transmit motor commands
    • Cauda equina: Lower spinal nerves forming a bundle near the lower end of the spinal cord.

Peripheral Nervous System (PNS)

• Contains 12 pairs of cranial nerves attached to the ventral/surface of the brain and 31 pairs of spinal nerves that carry impulses to the brain.

• Spinal and cranial nerves exit the vertebral column or brain to innervate muscles and sensory receptors.

• Afferent axons carry sensory information towards the central nervous system (CNS).

• Efferent axons send motor commands away from the CNS toward the muscles and glands.

• Autonomic nervous system: part of the PNS that regulates smooth muscle, cardiac muscle, and glands, separated into sympathetic and parasympathetic divisions.

Studying the Living Human Brain (Noninvasive Methods)

• Computerized Tomography (CT): uses X-rays to create cross-sectional images of the brain.
• Magnetic Resonance Imaging (MRI): uses magnetic fields and radio waves to create detailed images of the brain.

Research Techniques(Invasive Methods)

• Techniques used to produce lesions (damage to specific brain regions) in animals (mostly), as a way to evaluate the effects of those lesions.
• Some techniques to produce lesions include Electrical currents, Excitotoxic lesion production, Radiofrequency lesions, and Stereotaxic surgery.

Diffusion Tensor Imaging (DTI)

• An advanced MRI technique that tracks the movement of water molecules in the white matter pathways.